Restructure the spinlock code:

- Add function-based spinlock API
- Improve comments
- Reduce bouncing with contested locks

include/xrpl/basics/CountedObject.h

@@ -1,29 +1,31 @@
 #pragma once
 
-#include <xrpl/beast/type_name.h>
+#include <xrpl/beast/utility/instrumentation.h>
 
+#include <boost/core/type_name.hpp>
+
+#include <algorithm>
 #include <atomic>
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
 #include <string>
+#include <type_traits>
 #include <utility>
-#include <vector>
 
 namespace xrpl {
 
 /**
  * Manages all counted object types.
+ *
+ * Counters register themselves on a lock-free intrusive list maintained
+ * by this object when constructed. Because counters are never destroyed
+ * or removed, the ABA problem does not apply.
+ *
+ * The registry is iterable as a forward range.
  */
 class CountedObjects
 {
-public:
-    static CountedObjects&
-    getInstance() noexcept;
-
-    using Entry = std::pair<std::string, int>;
-    using List = std::vector<Entry>;
-
-    [[nodiscard]] List
-    getCounts(int minimumThreshold) const;
-
 public:
     /**
      * Implementation for @ref CountedObject.
@@ -33,68 +35,147 @@ public:
     class Counter
     {
     public:
-        Counter(std::string name) noexcept : name_(std::move(name)), count_(0)
-        {
-            // Insert ourselves at the front of the lock-free linked list
-            CountedObjects& instance = CountedObjects::getInstance();
-            Counter* head = nullptr;
+        Counter(std::string name) noexcept;
 
-            do
-            {
-                head = instance.head_.load();
-                next_ = head;
-            } while (instance.head_.exchange(this) != head);
+        // Counters are intrusive list nodes whose addresses are published
+        // in the registry; they must never be copied or moved. The atomic
+        // members already force this, but we make it explicit.
+        Counter(Counter const&) = delete;
+        Counter&
+        operator=(Counter const&) = delete;
+        Counter(Counter&&) = delete;
+        Counter&
+        operator=(Counter&&) = delete;
 
-            ++instance.count_;
-        }
-
-        ~Counter() noexcept = default;
-
-        int
+        std::uint32_t
         increment() noexcept
         {
-            return ++count_;
+            auto const newCount = count_.fetch_add(1, std::memory_order::relaxed) + 1;
+            XRPL_ASSERT(newCount != 0, "xrpl::CountedObjects::Counter::increment : no overflow");
+
+            auto maxCount = maxCount_.load(std::memory_order::relaxed);
+
+            while (newCount > maxCount &&
+                   !maxCount_.compare_exchange_weak(maxCount, newCount, std::memory_order::relaxed))
+            {
+            }
+
+            return newCount;
         }
 
-        int
+        std::uint32_t
         decrement() noexcept
         {
-            return --count_;
+            auto const prev = count_.fetch_sub(1, std::memory_order::relaxed);
+            XRPL_ASSERT(prev != 0, "xrpl::CountedObjects::Counter::decrement : no underflow");
+            return prev - 1;
         }
 
-        [[nodiscard]] int
-        getCount() const noexcept
+        [[nodiscard]] std::uint32_t
+        count() const noexcept
         {
-            return count_.load();
+            return count_.load(std::memory_order::relaxed);
         }
 
-        [[nodiscard]] Counter*
-        getNext() const noexcept
+        [[nodiscard]] std::uint32_t
+        max() const noexcept
         {
-            return next_;
+            return std::max(
+                count_.load(std::memory_order::relaxed),
+                maxCount_.load(std::memory_order::relaxed));
         }
 
         [[nodiscard]] std::string const&
-        getName() const noexcept
+        name() const noexcept
         {
             return name_;
         }
 
     private:
+        friend class CountedObjects;
+
+        Counter* next_ = nullptr;
+        std::atomic<std::uint32_t> count_ = 0;
+        std::atomic<std::uint32_t> maxCount_ = 0;
         std::string const name_;
-        std::atomic<int> count_;
-        Counter* next_;
     };
 
-private:
-    CountedObjects() noexcept;
-    ~CountedObjects() noexcept = default;
+    class Iterator
+    {
+    public:
+        using value_type = Counter const;
+        using reference = value_type&;
+        using pointer = value_type*;
+        using difference_type = std::ptrdiff_t;
+        using iterator_category = std::forward_iterator_tag;
+
+        explicit Iterator(Counter* c = nullptr) noexcept : current_(c)
+        {
+        }
+
+        reference
+        operator*() const noexcept
+        {
+            return *current_;
+        }
+
+        pointer
+        operator->() const noexcept
+        {
+            return current_;
+        }
+
+        Iterator&
+        operator++() noexcept
+        {
+            current_ = current_->next_;
+            return *this;
+        }
+
+        Iterator
+        operator++(int) noexcept
+        {
+            auto tmp = *this;
+            ++*this;
+            return tmp;
+        }
+
+        bool
+        operator==(Iterator const&) const noexcept = default;
+
+    private:
+        Counter* current_;
+    };
+
+    constexpr CountedObjects() noexcept = default;
+
+    [[nodiscard]] auto
+    begin() const noexcept
+    {
+        return Iterator{head_.load(std::memory_order::acquire)};
+    }
+
+    [[nodiscard]] auto
+    end() const noexcept
+    {
+        return Iterator{};
+    }
 
 private:
-    std::atomic<int> count_;
-    std::atomic<Counter*> head_;
+    std::atomic<Counter*> head_ = nullptr;
 };
 
+/** The global counted object registry. */
+inline constinit CountedObjects gCountedObjects;
+
+inline CountedObjects::Counter::Counter(std::string name) noexcept
+    : next_(gCountedObjects.head_.load(std::memory_order::relaxed)), name_(std::move(name))
+{
+    while (!gCountedObjects.head_.compare_exchange_weak(
+        next_, this, std::memory_order::release, std::memory_order::relaxed))
+        ;
+}
+
 //------------------------------------------------------------------------------
 
 /**
@@ -103,27 +184,37 @@ private:
  * Derived classes have their instances counted automatically. This is used
  * for reporting purposes.
  *
+ * The constructors are private and `Object` is befriended so that the
+ * CRTP parameter must be the deriving class itself: a copy-paste error
+ * like `class B : public CountedObject<A>` fails to compile instead of
+ * silently polluting A's count.
+ *
+ * @note This class has no move operations by design: a derived class's
+ *       move constructor falls back to the copy constructor for this
+ *       base, so the newly created instance is counted. This keeps the
+ *       invariant that count is the number of outstanding subobjects.
+ *
+ * @warning Counted objects constructed during dynamic initialization of
+ *          other translation units may have their increments discarded when
+ *          counter itself is dynamically initialized. Do not create counted
+ *          objects before main() begins.
+ *
  * @ingroup basics
  */
 template <class Object>
+    requires std::is_class_v<Object>
 class CountedObject
 {
-private:
-    static auto&
-    getCounter() noexcept
-    {
-        static CountedObjects::Counter kC{beast::typeName<Object>()};
-        return kC;
-    }
+    static inline CountedObjects::Counter counter{boost::core::type_name<Object>()};
 
     CountedObject() noexcept
     {
-        getCounter().increment();
+        counter.increment();
     }
 
     CountedObject(CountedObject const&) noexcept
     {
-        getCounter().increment();
+        counter.increment();
     }
 
     CountedObject&
@@ -132,7 +223,7 @@ private:
 public:
     ~CountedObject() noexcept
     {
-        getCounter().decrement();
+        counter.decrement();
     }
 
     friend Object;

include/xrpl/basics/SlabAllocator.h

@@ -3,11 +3,11 @@
 #pragma once
 
 #include <xrpl/basics/ByteUtilities.h>
-#include <xrpl/beast/type_name.h>
 #include <xrpl/beast/utility/instrumentation.h>
 
 #include <boost/align.hpp>
 #include <boost/container/static_vector.hpp>
+#include <boost/core/type_name.hpp>
 #include <boost/predef.h>
 
 #include <algorithm>
@@ -16,6 +16,7 @@
 #include <cstring>
 #include <mutex>
 #include <stdexcept>
+#include <typeinfo>
 #include <vector>
 
 #if BOOST_OS_LINUX
@@ -335,7 +336,7 @@ public:
                 }) != cfg.end())
         {
             throw std::runtime_error(
-                "SlabAllocatorSet<" + beast::typeName<Type>() + ">: duplicate slab size");
+                "SlabAllocatorSet<" + boost::core::type_name<Type>() + ">: duplicate slab size");
         }
 
         for (auto const& c : cfg)

include/xrpl/basics/contract.h

@@ -1,7 +1,8 @@
 #pragma once
 
 #include <xrpl/basics/sanitizers.h>
-#include <xrpl/beast/type_name.h>
+
+#include <boost/core/type_name.hpp>
 
 #include <exception>
 #include <string>
@@ -55,7 +56,7 @@ Throw(Args&&... args)
         std::is_convertible_v<E*, std::exception*>, "Exception must derive from std::exception.");
 
     E e(std::forward<Args>(args)...);
-    logThrow(std::string("Throwing exception of type " + beast::typeName<E>() + ": ") + e.what());
+    logThrow("Throwing exception of type " + boost::core::type_name<E>() + ": " + e.what());
     throw std::move(e);
 }
 

include/xrpl/basics/enum_bitops.h

@@ -0,0 +1,200 @@
+#pragma once
+
+#include <concepts>
+#include <type_traits>
+#include <utility>
+
+namespace xrpl {
+
+/**
+ * Opt-in bitwise operators for scoped enumerations.
+ *
+ * Provides `&`, `|`, `^`, `~` and the corresponding compound assignment forms
+ * for any scoped enumeration with an unsigned underlying type that opts in by
+ * specializing @ref OptIn:
+ *
+ * @code
+ * namespace xrpl {
+ *
+ * enum class MyFlags : std::uint32_t { a = 1, b = 2, c = 4 };
+ *
+ * template <>
+ * struct enum_bitops::OptIn<MyFlags> : std::true_type {};
+ *
+ * }  // namespace xrpl
+ * @endcode
+ *
+ * The operators are constexpr and noexcept, and return the enumeration type.
+ *
+ * @par Where the specialization may be declared
+ *   In namespace xrpl, or at global scope with full qualification, and after
+ *   the enumeration is defined but before the operators are first used. This
+ *   cannot be done in a nested namespace or at class scope; for enumerations
+ *   nested in a class this means after the class definition.
+ *
+ * @par Where the operators are found
+ *   The operators are declared in namespace xrpl, so argument-dependent lookup
+ *   will find them only for enumerations declared in xrpl or nested in a class
+ *   declared directly in xrpl. Enumerations in a nested namespace will only be
+ *   found from code inside xrpl, and only if no enclosing scope declares an
+ *   operator of the same name; elsewhere they require using-declarations.
+ */
+namespace enum_bitops {
+
+/**
+ * Types that may be opted in to the bitwise operators.
+ *
+ * Satisfied by a scoped enumeration whose underlying type is an unsigned
+ * integer type.
+ *
+ * @tparam T The type to test.
+ */
+template <typename T>
+concept Eligible = std::is_scoped_enum_v<T> && std::unsigned_integral<std::underlying_type_t<T>>;
+
+/**
+ * Opt-in switch for the bitwise operators.
+ *
+ * The primary template derives from std::false_type. Specialize it to derive
+ * from std::true_type to enable the operators for an @ref Eligible enumeration.
+ *
+ * @tparam T The scoped enumeration to opt in.
+ */
+template <Eligible T>
+struct OptIn : std::false_type
+{
+};
+
+/**
+ * Enumerations for which the bitwise operators are enabled.
+ *
+ * Satisfied when @p T satisfies @ref Eligible and @ref OptIn has been
+ * specialized for it to derive from std::true_type.
+ *
+ * @tparam T The type to test.
+ */
+template <typename T>
+concept Candidate = Eligible<T> && OptIn<T>::value;
+
+}  // namespace enum_bitops
+
+// These are declared in xrpl, not in enum_bitops, so that argument-dependent
+// lookup finds them for enumerations whose associated namespace is xrpl.
+
+/**
+ * @name Bitwise operators for opted-in scoped enumerations
+ *
+ * Each operator applies the corresponding built-in operator to the
+ * underlying values and converts the result back to the enumeration type.
+ * Both operands must have the same enumeration type; there is no implicit
+ * conversion to or from the underlying type.
+ */
+/** @{ */
+
+/**
+ * Bitwise AND.
+ *
+ * @param lhs The left operand.
+ * @param rhs The right operand.
+ * @return The bits set in both @p lhs and @p rhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T
+operator&(T lhs, T rhs) noexcept
+{
+    return static_cast<T>(std::to_underlying(lhs) & std::to_underlying(rhs));
+}
+
+/**
+ * Bitwise OR.
+ *
+ * @param lhs The left operand.
+ * @param rhs The right operand.
+ * @return The bits set in @p lhs, in @p rhs, or in both.
+ */
+template <enum_bitops::Candidate T>
+constexpr T
+operator|(T lhs, T rhs) noexcept
+{
+    return static_cast<T>(std::to_underlying(lhs) | std::to_underlying(rhs));
+}
+
+/**
+ * Bitwise exclusive OR.
+ *
+ * @param lhs The left operand.
+ * @param rhs The right operand.
+ * @return The bits set in exactly one of @p lhs and @p rhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T
+operator^(T lhs, T rhs) noexcept
+{
+    return static_cast<T>(std::to_underlying(lhs) ^ std::to_underlying(rhs));
+}
+
+/**
+ * Bitwise complement.
+ *
+ * The result has every bit of the underlying type that is clear in
+ * @p val, including bits that no enumerator names. It is intended for
+ * clearing flags, as in `flags & ~flag`.
+ *
+ * @param val The operand.
+ * @return The complement of @p val.
+ */
+template <enum_bitops::Candidate T>
+constexpr T
+operator~(T val) noexcept
+{
+    return static_cast<T>(~std::to_underlying(val));
+}
+
+/**
+ * Bitwise AND assignment.
+ *
+ * @param lhs The value to modify.
+ * @param rhs The right operand.
+ * @return A reference to @p lhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T&
+operator&=(T& lhs, T rhs) noexcept
+{
+    lhs = lhs & rhs;
+    return lhs;
+}
+
+/**
+ * Bitwise OR assignment.
+ *
+ * @param lhs The value to modify.
+ * @param rhs The right operand.
+ * @return A reference to @p lhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T&
+operator|=(T& lhs, T rhs) noexcept
+{
+    lhs = lhs | rhs;
+    return lhs;
+}
+
+/**
+ * Bitwise exclusive OR assignment.
+ *
+ * @param lhs The value to modify.
+ * @param rhs The right operand.
+ * @return A reference to @p lhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T&
+operator^=(T& lhs, T rhs) noexcept
+{
+    lhs = lhs ^ rhs;
+    return lhs;
+}
+
+/** @} */
+
+}  // namespace xrpl

include/xrpl/basics/safe_cast.h

@@ -2,107 +2,212 @@
 
 #include <xrpl/beast/utility/instrumentation.h>  // IWYU pragma: keep
 
+#include <concepts>
+#include <cstdint>
+#include <limits>
+#include <memory>
 #include <type_traits>
+#include <utility>
 
 namespace xrpl {
 
-// safe_cast adds compile-time checks to a static_cast to ensure that
-// the destination can hold all values of the source.  This is particularly
-// handy when the source or destination is an enumeration type.
+/** Every value of @p Src can be represented by @p Dest.
 
-template <class Src, class Dest>
-concept SafeToCast = (std::is_integral_v<Src> && std::is_integral_v<Dest>) &&
-    (std::is_signed_v<Src> || std::is_unsigned_v<Dest>) &&
-    (std::is_signed_v<Src> != std::is_signed_v<Dest> ? sizeof(Dest) > sizeof(Src)
-                                                     : sizeof(Dest) >= sizeof(Src));
+    Given two integral types, the cast is safe when the destination can
+    hold every possible value of the source.
 
-template <class Dest, class Src>
+    Comparing the bounds requires care: we use @c std::cmp_less_equal and
+    @c std::cmp_greater_equal; the plain relational operators would apply
+    arithmetic conversions, resulting in incorrect results when comparing
+    across signedness.
+
+    Because @c std::cmp_* requires standard signed or unsigned integer
+    arguments, which excludes character types and bool, we first widen
+    all type bounds to the maximum-width integer type while preserving
+    signedness.
+
+    @note Extended integer types, like __int128 on gcc, cannot be safely
+          widened to a standard integer type, so the concept will reject
+          them.
+*/
+template <typename Src, typename Dest>
+concept SafeToCast = std::is_integral_v<Src> && std::is_integral_v<Dest> && []() consteval {
+    using WideSrc = std::conditional_t<std::is_signed_v<Src>, std::intmax_t, std::uintmax_t>;
+    using WideDest = std::conditional_t<std::is_signed_v<Dest>, std::intmax_t, std::uintmax_t>;
+
+    // Note: this guard must be an evaluated branch, and not a
+    // static_assert. The lambda body is outside the immediate
+    // context, so a substitution-time failure here would be a
+    // hard error rather than leaving the concept unsatisfied.
+    if constexpr (sizeof(Src) > sizeof(WideSrc) || sizeof(Dest) > sizeof(WideDest))
+    {
+        return false;
+    }
+    else
+    {
+        return std::cmp_less_equal(
+                   static_cast<WideDest>(std::numeric_limits<Dest>::min()),
+                   static_cast<WideSrc>(std::numeric_limits<Src>::min())) &&
+            std::cmp_greater_equal(
+                   static_cast<WideDest>(std::numeric_limits<Dest>::max()),
+                   static_cast<WideSrc>(std::numeric_limits<Src>::max()));
+    }
+}();
+
+/** Compile-time-checked static_cast that rejects non-value preserving casts.
+
+    @note There is deliberately no enum-to-enum overload, and no overload
+          returning the underlying type of an enum. For the latter, use
+          @c std::to_underlying.
+*/
+/** @{ */
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 safeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 {
     static_assert(
-        std::is_signed_v<Dest> || std::is_unsigned_v<Src>, "Cannot cast signed to unsigned");
-    constexpr unsigned kNotSame = std::is_signed_v<Dest> != std::is_signed_v<Src>;
-    static_assert(
-        sizeof(Dest) >= sizeof(Src) + kNotSame,
-        "Destination is too small to hold all values of source");
+        SafeToCast<Src, Dest>, "This cast is not value-preserving. Please use unsafeCast instead.");
     return static_cast<Dest>(s);
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 safeCast(Src s) noexcept
-    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 {
     return static_cast<Dest>(safeCast<std::underlying_type_t<Dest>>(s));
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 constexpr Dest
 safeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 {
-    return safeCast<Dest>(static_cast<std::underlying_type_t<Src>>(s));
+    return safeCast<Dest>(std::to_underlying(s));
 }
+/** @} */
 
-// unsafe_cast explicitly flags a static_cast as not necessarily able to hold
-// all values of the source. It includes a compile-time check so that if
-// underlying types become safe, it can be converted to a safe_cast.
+/** Integral-to-integral cast that is known to be narrowing or sign-erasing.
 
-template <class Dest, class Src>
+    This explicitly flags a conversion that can lose information for some
+    values of the source type, where the call site accepts that loss (or
+    truncation is the intended behavior).
+
+    The compile-time check ensures the cast remains "unsafe": if the types
+    involved later change such that the conversion becomes inherently
+    value-preserving, the static assertion fires with instructions to
+    migrate the call site to @ref safeCast.
+
+    If the conversion's safety depends on a runtime precondition rather
+    than on the types, or varies across instantiations of generic code,
+    use @ref checkedCast instead.
+*/
+/** @{ */
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 unsafeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 {
     static_assert(
-        !SafeToCast<Src, Dest>,
-        "Only unsafe if casting signed to unsigned or "
-        "destination is too small");
+        !SafeToCast<Src, Dest>, "This cast is value-preserving. Please use safeCast instead.");
     return static_cast<Dest>(s);
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 unsafeCast(Src s) noexcept
-    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 {
     return static_cast<Dest>(unsafeCast<std::underlying_type_t<Dest>>(s));
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 constexpr Dest
 unsafeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 {
-    return unsafeCast<Dest>(static_cast<std::underlying_type_t<Src>>(s));
+    return unsafeCast<Dest>(std::to_underlying(s));
+}
+/** @} */
+
+/** Integral-to-integral cast when the caller has performed a bounds check.
+
+    This documents that a runtime precondition or external invariant, which
+    is not necessarily visible to the compiler, guarantees that the requested
+    conversion is value-preserving for the values that can actually occur.
+
+    This is primarily meant for generic code, where the same expression may
+    be value-preserving for one instantiation but not for another, making
+    both @ref safeCast and @ref unsafeCast unusable.
+
+    Unlike @ref safeCast and @ref unsafeCast, this imposes no static check
+    on the type relationship: the caller's claim is about runtime values,
+    not about types.
+*/
+/** @{ */
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
+constexpr Dest
+checkedCast(Src s) noexcept
+{
+    return static_cast<Dest>(s);
 }
 
+template <typename Dest, typename Src>
+    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
+constexpr Dest
+checkedCast(Src s) noexcept
+{
+    return static_cast<Dest>(checkedCast<std::underlying_type_t<Dest>>(s));
+}
+
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
+constexpr Dest
+checkedCast(Src s) noexcept
+{
+    return checkedCast<Dest>(std::to_underlying(s));
+}
+/** @} */
+
+/** Downcast within a class hierarchy, verified in debug builds.
+
+    Performs a static_cast down a hierarchy, but in debug builds verifies
+    via dynamic_cast that the object's dynamic type actually permits the
+    downcast. Both build modes execute the same conversion; debug builds
+    merely add the check.
+
+    The pointer form passes null through unchanged, as dynamic_cast does.
+
+    @note The check requires @p Src to be polymorphic; in release builds
+          an invalid downcast is undefined behavior on use, exactly as
+          with a bare static_cast.
+*/
+/** @{ */
 template <class Dest, class Src>
-    requires std::is_pointer_v<Dest>
+    requires(
+        std::is_pointer_v<Dest> && std::is_polymorphic_v<Src> &&
+        std::derived_from<std::remove_pointer_t<Dest>, Src> &&
+        (std::is_const_v<std::remove_pointer_t<Dest>> || !std::is_const_v<Src>) &&
+        (std::is_volatile_v<std::remove_pointer_t<Dest>> || !std::is_volatile_v<Src>))
 inline Dest
 safeDowncast(Src* s) noexcept
 {
-#ifdef NDEBUG
+    XRPL_ASSERT(
+        s == nullptr || dynamic_cast<Dest>(s) != nullptr, "xrpl::safeDowncast : valid downcast");
     return static_cast<Dest>(s);  // NOLINT(cppcoreguidelines-pro-type-static-cast-downcast)
-#else
-    auto* result = dynamic_cast<Dest>(s);
-    XRPL_ASSERT(result != nullptr, "xrpl::safeDowncast : pointer downcast is valid");
-    return result;
-#endif
 }
 
 template <class Dest, class Src>
-    requires std::is_lvalue_reference_v<Dest>
+    requires(
+        std::is_lvalue_reference_v<Dest> && std::is_polymorphic_v<Src> &&
+        std::derived_from<std::remove_reference_t<Dest>, Src>)
 inline Dest
 safeDowncast(Src& s) noexcept
 {
-#ifndef NDEBUG
-    XRPL_ASSERT(
-        dynamic_cast<std::add_pointer_t<std::remove_reference_t<Dest>>>(&s) != nullptr,
-        "xrpl::safeDowncast : reference downcast is valid");
-#endif
-    return static_cast<Dest>(s);  // NOLINT(cppcoreguidelines-pro-type-static-cast-downcast)
+    return *safeDowncast<std::add_pointer_t<std::remove_reference_t<Dest>>>(std::addressof(s));
 }
+/** @} */
 
 }  // namespace xrpl

include/xrpl/basics/spinlock.h

@@ -4,88 +4,215 @@
 
 #include <xrpl/beast/utility/instrumentation.h>
 
+#include <boost/predef/architecture.h>
+
 #include <atomic>
+#include <concepts>
 #include <limits>
 #include <type_traits>
 
-#ifndef __aarch64__
+#if BOOST_ARCH_X86
 #include <immintrin.h>
 #endif
 
 namespace xrpl {
 
+/** An unsigned integral type suitable for use as a spinlock.
+
+    The type must be always lock-free when wrapped in std::atomic, so
+    that lock operations cannot themselves take a (library-level) lock.
+ */
+template <typename T>
+concept SpinlockValueType = std::is_unsigned_v<T> && std::atomic<T>::is_always_lock_free;
+
+/** A spinlock value type that additionally supports the atomic bitwise
+    operations required to pack multiple locks into a single integer.
+ */
+template <typename T>
+concept PackedSpinlockValueType = SpinlockValueType<T> && requires(std::atomic<T>& a, T v) {
+    { a.fetch_or(v) } -> std::same_as<T>;
+    { a.fetch_and(v) } -> std::same_as<T>;
+};
+
 namespace detail {
-/**
- * Inform the processor that we are in a tight spin-wait loop.
- *
- * Spinlocks caught in tight loops can result in the processor's pipeline
- * filling up with comparison operations, resulting in a misprediction at
- * the time the lock is finally acquired, necessitating pipeline flushing
- * which is ridiculously expensive and results in very high latency.
- *
- * This function instructs the processor to "pause" for some architecture
- * specific amount of time, to prevent this.
+
+/** Inform the processor that we are in a tight spin-wait loop.
+
+    Spinlocks caught in tight loops can result in the processor's pipeline
+    filling up with comparison operations, resulting in a misprediction at
+    the time the lock is finally acquired, necessitating pipeline flushing
+    which is ridiculously expensive and results in very high latency.
+
+    This function instructs the processor to "pause" for some architecture
+    specific amount of time, to prevent this.
  */
 inline void
 spinPause() noexcept
 {
-#ifdef __aarch64__
-    asm volatile("yield");
-#else
+#if BOOST_ARCH_X86
     _mm_pause();
+#elif BOOST_ARCH_ARM
+    asm volatile("yield" ::: "memory");
+#else
+#error No implementation available for spinPause to use
 #endif
 }
 
 }  // namespace detail
 
-/** @{ */
-/**
- * Classes to handle arrays of spinlocks packed into a single atomic integer:
- *
- * Packed spinlocks allow for tremendously space-efficient lock-sharding
- * but they come at a cost.
- *
- * First, the implementation is necessarily low-level and uses advanced
- * features like memory ordering and highly platform-specific tricks to
- * maximize performance. This imposes a significant and ongoing cost to
- * developers.
- *
- * Second, and perhaps most important, is that the packing of multiple
- * locks into a single integer which, albeit space-efficient, also has
- * performance implications stemming from data dependencies, increased
- * cache-coherency traffic between processors and heavier loads on the
- * processor's load/store units.
- *
- * To be sure, these locks can have advantages but they are definitely
- * not general purpose locks and should not be thought of or used that
- * way. The use cases for them are likely few and far between; without
- * a compelling reason to use them, backed by profiling data, it might
- * be best to use one of the standard locking primitives instead. Note
- * that in most common platforms, `std::mutex` is so heavily optimized
- * that it can, usually, outperform spinlocks.
- *
- * @tparam T An unsigned integral type (e.g. std::uint16_t)
- */
+//------------------------------------------------------------------------------
 
-/**
- * A class that grabs a single packed spinlock from an atomic integer.
- *
- * This class meets the requirements of Lockable:
- *     https://en.cppreference.com/w/cpp/named_req/Lockable
+/** Attempt to acquire a spinlock without blocking.
+
+    @note This interface is primarily intended for one-shot attempts to
+          acquire the lock. Avoid calling this function directly from a
+          loop and use @ref spinLock instead.
+
+    @tparam T An unsigned integral type.
+    @param lock The atomic variable used as the lock.
+    @return true if the lock was acquired, false if it was already held.
  */
-template <class T>
+template <SpinlockValueType T>
+[[nodiscard]] bool
+spinTryLock(std::atomic<T>& lock) noexcept
+{
+    // A compare-exchange is required here, not an unconditional exchange:
+    // a failed attempt must not modify the lock word, in case the atomic
+    // is shared with PackedSpinlock).
+    T expected = 0;
+
+    return lock.compare_exchange_strong(
+        expected,
+        std::numeric_limits<T>::max(),
+        std::memory_order::acquire,
+        std::memory_order::relaxed);
+    ;
+}
+
+/** Acquire a spinlock, blocking until available.
+
+    Uses a TTAS (test-and-test-and-set) pattern, so waiters share the cache
+    line read-only, helping to avoid unnecessary coherency traffic.
+
+    @tparam T An unsigned integral type.
+    @param lock The atomic variable used as the lock.
+ */
+template <SpinlockValueType T>
+void
+spinLock(std::atomic<T>& lock) noexcept
+{
+    do
+    {
+        // Relaxed ordering is sufficient for the spin: this load is only
+        // a filter. The acquire on the successful exchange in spinTryLock
+        // is what synchronizes the critical section.
+        while (lock.load(std::memory_order::relaxed) != 0)
+            detail::spinPause();
+    } while (!spinTryLock(lock));
+}
+
+/** Release a spinlock.
+
+    @tparam T An unsigned integral type.
+    @param lock The atomic variable used as the lock.
+ */
+template <SpinlockValueType T>
+void
+spinUnlock(std::atomic<T>& lock) noexcept
+{
+    lock.store(0, std::memory_order::release);
+}
+
+//------------------------------------------------------------------------------
+
+/** A Lockable interface to a spinlock implemented on top of an atomic.
+
+    @tparam T An unsigned integral type.
+
+    @note Using `PackedSpinlock` and `Spinlock` against the same underlying
+          atomic integer is possible but can result in `Spinlock` not being
+          able to acquire the lock during periods of high contention due to
+          the way the two locks operate: `Spinlock` spins and tries to grab
+          all the bits at once, whereas any given `PackedSpinlock` instance
+          only tries to grab one bit at a time. Caveat emptor.
+
+    This class meets the requirements of Lockable:
+        https://en.cppreference.com/w/cpp/named_req/Lockable
+ */
+template <SpinlockValueType T>
+class Spinlock
+{
+    std::atomic<T>& lock_;
+
+public:
+    Spinlock(Spinlock const&) = delete;
+    Spinlock&
+    operator=(Spinlock const&) = delete;
+
+    /** Construct a spinlock handle.
+
+        @param lock The atomic integer to spin against.
+
+        @note For performance reasons, you should strive to have `lock` be
+              on a cacheline by itself.
+     */
+    explicit Spinlock(std::atomic<T>& lock) noexcept : lock_(lock)
+    {
+    }
+
+    [[nodiscard]] bool
+    try_lock() noexcept  // NOLINT(readability-identifier-naming)
+    {
+        return spinTryLock(lock_);
+    }
+
+    void
+    lock() noexcept
+    {
+        spinLock(lock_);
+    }
+
+    void
+    unlock() noexcept
+    {
+        spinUnlock(lock_);
+    }
+};
+
+//------------------------------------------------------------------------------
+
+/** A Lockable interface to a packed spinlock implemented on top of an atomic.
+
+    Packed spinlocks offer tremendous space-efficient lock-sharding but
+    they come at a cost.
+
+    First, the implementation is necessarily low-level and uses advanced
+    features like memory ordering and highly platform-specific tricks to
+    maximize performance. This imposes a significant and ongoing cost to
+    developers.
+
+    Second, and perhaps most important, is that the packing of multiple
+    locks into a single integer which, albeit space-efficient, also has
+    performance implications stemming from data dependencies, increased
+    cache-coherency traffic between processors and heavier loads on the
+    processor's load/store units.
+
+    To be sure, these locks can have advantages but they are definitely
+    not general purpose locks and should not be thought of or used that
+    way. The use cases for them are likely few and far between; without
+    a compelling reason to use them, backed by profiling data, it might
+    be best to use one of the standard locking primitives instead. Note
+    that in most common platforms, `std::mutex` is so heavily optimized
+    that it can, usually, outperform spinlocks.
+
+    @tparam T An unsigned integral type (e.g. std::uint16_t)
+
+    This class meets the requirements of Lockable:
+        https://en.cppreference.com/w/cpp/named_req/Lockable
+ */
+template <PackedSpinlockValueType T>
 class PackedSpinlock
 {
-    // clang-format off
-    static_assert(std::is_unsigned_v<T>);
-    static_assert(std::atomic<T>::is_always_lock_free);
-    static_assert(
-        std::is_same_v<decltype(std::declval<std::atomic<T>&>().fetch_or(0)), T> &&
-        std::is_same_v<decltype(std::declval<std::atomic<T>&>().fetch_and(0)), T>,
-        "std::atomic<T>::fetch_and(T) and std::atomic<T>::fetch_and(T) are required by packed_spinlock");
-    // clang-format on
-
-private:
     std::atomic<T>& bits_;
     T const mask_;
 
@@ -94,120 +221,49 @@ public:
     PackedSpinlock&
     operator=(PackedSpinlock const&) = delete;
 
-    /**
-     * A single spinlock packed inside the specified atomic
-     *
-     * @param lock The atomic integer inside which the spinlock is packed.
-     * @param index The index of the spinlock this object acquires.
-     *
-     * @note For performance reasons, you should strive to have `lock` be
-     *       on a cacheline by itself.
+    /** Construct a packed spinlock handle for a single bit.
+
+        @param lock The atomic integer inside which the spinlock is packed.
+        @param index The index of the spinlock this object acquires.
+
+        @note For performance reasons, you should strive to have `lock` be
+              on a cacheline by itself.
      */
-    PackedSpinlock(std::atomic<T>& lock, int index) : bits_(lock), mask_(static_cast<T>(1) << index)
-    {
-        XRPL_ASSERT(
-            index >= 0 && (mask_ != 0),
-            "xrpl::PackedSpinlock::PackedSpinlock : valid index and mask");
-    }
-
-    [[nodiscard]] bool
-    try_lock()  // NOLINT(readability-identifier-naming)
-    {
-        return (bits_.fetch_or(mask_, std::memory_order_acquire) & mask_) == 0;
-    }
-
-    void
-    lock()
-    {
-        while (!try_lock())
-        {
-            // The use of relaxed memory ordering here is intentional and
-            // serves to help reduce cache coherency traffic during times
-            // of contention by avoiding writes that would definitely not
-            // result in the lock being acquired.
-            while ((bits_.load(std::memory_order_relaxed) & mask_) != 0)
-                detail::spinPause();
-        }
-    }
-
-    void
-    unlock()
-    {
-        bits_.fetch_and(~mask_, std::memory_order_release);
-    }
-};
-
-/**
- * A spinlock implemented on top of an atomic integer.
- *
- * @note Using `packed_spinlock` and `spinlock` against the same underlying
- *       atomic integer can result in `spinlock` not being able to actually
- *       acquire the lock during periods of high contention, because of how
- *       the two locks operate: `spinlock` will spin trying to grab all the
- *       bits at once, whereas any given `packed_spinlock` will only try to
- *       grab one bit at a time. Caveat emptor.
- *
- * This class meets the requirements of Lockable:
- *     https://en.cppreference.com/w/cpp/named_req/Lockable
- */
-template <class T>
-class Spinlock
-{
-    static_assert(std::is_unsigned_v<T>);
-    static_assert(std::atomic<T>::is_always_lock_free);
-
-private:
-    std::atomic<T>& lock_;
-
-public:
-    Spinlock(Spinlock const&) = delete;
-    Spinlock&
-    operator=(Spinlock const&) = delete;
-
-    /**
-     * Grabs the
-     *
-     * @param lock The atomic integer to spin against.
-     *
-     * @note For performance reasons, you should strive to have `lock` be
-     *       on a cacheline by itself.
-     */
-    Spinlock(std::atomic<T>& lock) : lock_(lock)
+    PackedSpinlock(std::atomic<T>& lock, int index) noexcept
+        : bits_(lock), mask_([index]() {
+            XRPL_ASSERT(
+                index >= 0 && index < std::numeric_limits<T>::digits,
+                "xrpl::PackedSpinlock::PackedSpinlock : valid index");
+            return static_cast<T>(T{1} << index);
+        }())
     {
     }
 
     [[nodiscard]] bool
-    try_lock()  // NOLINT(readability-identifier-naming)
+    try_lock() noexcept  // NOLINT(readability-identifier-naming)
     {
-        T expected = 0;
-
-        return lock_.compare_exchange_weak(
-            expected,
-            std::numeric_limits<T>::max(),
-            std::memory_order_acquire,
-            std::memory_order_relaxed);
+        return (bits_.fetch_or(mask_, std::memory_order::acquire) & mask_) == 0;
     }
 
     void
-    lock()
+    lock() noexcept
     {
-        while (!try_lock())
+        do
         {
             // The use of relaxed memory ordering here is intentional and
             // serves to help reduce cache coherency traffic during times
-            // of contention by avoiding writes that would definitely not
-            // result in the lock being acquired.
-            while (lock_.load(std::memory_order_relaxed) != 0)
+            // of contention by avoiding writes that are unlikely to grab
+            // the requested lock.
+            while ((bits_.load(std::memory_order::relaxed) & mask_) != 0)
                 detail::spinPause();
-        }
+        } while (!try_lock());
     }
 
     void
-    unlock()
+    unlock() noexcept
     {
-        lock_.store(0, std::memory_order_release);
+        bits_.fetch_and(~mask_, std::memory_order::release);
     }
 };
-/** @} */
 
 }  // namespace xrpl

include/xrpl/beast/type_name.h

@@ -1,47 +0,0 @@
-#pragma once
-
-#include <cstdlib>
-#include <string>
-#include <type_traits>
-#include <typeinfo>
-
-#ifndef _MSC_VER
-#include <cxxabi.h>
-#endif
-
-namespace beast {
-
-template <typename T>
-std::string
-typeName()
-{
-    using TR = std::remove_reference_t<T>;
-
-    std::string name = typeid(TR).name();
-
-#ifndef _MSC_VER
-    if (auto s = abi::__cxa_demangle(name.c_str(), nullptr, nullptr, nullptr))
-    {
-        name = s;
-        // NOLINTNEXTLINE(cppcoreguidelines-no-malloc)
-        std::free(s);
-    }
-#endif
-
-    if (std::is_const_v<TR>)
-        name += " const";
-    if (std::is_volatile_v<TR>)
-        name += " volatile";
-    if (std::is_lvalue_reference_v<T>)
-    {
-        name += "&";
-    }
-    else if (std::is_rvalue_reference_v<T>)
-    {
-        name += "&&";
-    }
-
-    return name;
-}
-
-}  // namespace beast

include/xrpl/beast/utility/Zero.h

@@ -2,26 +2,24 @@
 
 #pragma once
 
+#include <compare>
+#include <concepts>
+
 namespace beast {
 
 /**
  * Zero allows classes to offer efficient comparisons to zero.
  *
- * Zero is a struct to allow classes to efficiently compare with zero without
- * requiring an rvalue construction.
- *
  * It's often the case that we have classes which combine a number and a unit.
  * In such cases, comparisons like t > 0 or t != 0 make sense, but comparisons
- * like t > 1 or t != 1 do not.
+ * like t > 1 or t != 1 do not. Comparing against kZero expresses exactly that,
+ * without constructing a T.
  *
- * The class Zero allows such comparisons to be easily made.
- *
- * The comparing class T either needs to have a method called signum() which
- * returns a positive number, 0, or a negative; or there needs to be a signum
- * function which resolves in the namespace which takes an instance of T and
- * returns a positive, zero or negative number.
+ * A type T participates if either `t.signum()` or an unqualified `signum(t)`
+ * found by argument-dependent lookup returns an integer that is negative,
+ * zero, or positive according to the sign of t. Both `t == kZero` and
+ * `kZero == t` work, as do all six relational operators in either order.
  */
-
 struct Zero
 {
     explicit Zero() = default;
@@ -30,115 +28,44 @@ struct Zero
 inline constexpr Zero kZero{};
 
 /**
- * Default implementation of signum calls the method on the class.
+ * Default implementation of signum: call the member function.
  */
-template <typename T>
-auto
-signum(T const& t)
+template <class T>
+    requires requires(T const& t) {
+        { t.signum() } -> std::integral;
+    }
+[[nodiscard]] constexpr auto
+signum(T const& t) noexcept(noexcept(t.signum()))
 {
     return t.signum();
 }
 
-namespace detail::zero_helper {
+namespace detail {
 
-// For argument dependent lookup to function properly, calls to signum must
-// be made from a namespace that does not include overloads of the function..
+/**
+ * A type with a usable signum: either the member-based default above, or a
+ * `signum(t)` overload in T's own namespace, found by ADL. A user overload
+ * that is a better match than the template wins, as usual.
+ */
 template <class T>
-auto
-callSignum(T const& t)
+concept HasSignum = requires(T const& t) {
+    { signum(t) } -> std::integral;
+};
+
+}  // namespace detail
+
+template <detail::HasSignum T>
+[[nodiscard]] constexpr bool
+operator==(T const& t, Zero) noexcept(noexcept(signum(t)))
 {
-    return signum(t);
+    return signum(t) == 0;
 }
 
-}  // namespace detail::zero_helper
-
-// Handle operators where T is on the left side using signum.
-
-template <typename T>
-bool
-operator==(T const& t, Zero)
+template <detail::HasSignum T>
+[[nodiscard]] constexpr std::strong_ordering
+operator<=>(T const& t, Zero) noexcept(noexcept(signum(t)))
 {
-    return detail::zero_helper::callSignum(t) == 0;
-}
-
-template <typename T>
-bool
-operator!=(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) != 0;
-}
-
-template <typename T>
-bool
-operator<(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) < 0;
-}
-
-template <typename T>
-bool
-operator>(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) > 0;
-}
-
-template <typename T>
-bool
-operator>=(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) >= 0;
-}
-
-template <typename T>
-bool
-operator<=(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) <= 0;
-}
-
-// Handle operators where T is on the right side by
-// reversing the operation, so that T is on the left side.
-
-template <typename T>
-bool
-operator==(Zero, T const& t)
-{
-    return t == kZero;
-}
-
-template <typename T>
-bool
-operator!=(Zero, T const& t)
-{
-    return t != kZero;
-}
-
-template <typename T>
-bool
-operator<(Zero, T const& t)
-{
-    return t > kZero;
-}
-
-template <typename T>
-bool
-operator>(Zero, T const& t)
-{
-    return t < kZero;
-}
-
-template <typename T>
-bool
-operator>=(Zero, T const& t)
-{
-    return t <= kZero;
-}
-
-template <typename T>
-bool
-operator<=(Zero, T const& t)
-{
-    return t >= kZero;
+    return signum(t) <=> 0;
 }
 
 }  // namespace beast

include/xrpl/ledger/ApplyView.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <xrpl/basics/base_uint.h>
-#include <xrpl/basics/safe_cast.h>
+#include <xrpl/basics/enum_bitops.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/OwnerCounts.h>
 #include <xrpl/ledger/ReadView.h>
@@ -22,80 +22,39 @@
 
 namespace xrpl {
 
-// Bitwise flag enum with existing operator overloads
-// NOLINTNEXTLINE(cppcoreguidelines-use-enum-class)
-enum ApplyFlags : std::uint32_t {
-    TapNone = 0x00,
+enum class ApplyFlags : std::uint32_t {
+    None = 0x00,
 
     // This is a local transaction with the
     // fail_hard flag set.
-    TapFailHard = 0x10,
+    FailHard = 0x10,
 
     // This is not the transaction's last pass
     // Transaction can be retried, soft failures allowed
-    TapRetry = 0x20,
+    Retry = 0x20,
 
     // Transaction came from a privileged source
-    TapUnlimited = 0x400,
+    Unlimited = 0x400,
 
     // Transaction is executing as part of a batch
-    TapBatch = 0x800,
+    Batch = 0x800,
 
     // Transaction shouldn't be applied
     // Signatures shouldn't be checked
-    TapDryRun = 0x1000,
+    DryRun = 0x1000,
 
     // Transaction is being preflighted as the payload of a
     // TransactionProposalCreate. Its signatures are collected on-ledger
     // afterward, so signature-presence checks (e.g. Batch signer matching)
     // are skipped at proposal-creation time (On-Chain Cosigner spec
     // §5.3.1.2).
-    TapProposal = 0x2000
+    Proposal = 0x2000
 };
 
-constexpr ApplyFlags
-operator|(ApplyFlags const& lhs, ApplyFlags const& rhs)
+template <>
+struct enum_bitops::OptIn<ApplyFlags> : std::true_type
 {
-    return safeCast<ApplyFlags>(
-        safeCast<std::underlying_type_t<ApplyFlags>>(lhs) |
-        safeCast<std::underlying_type_t<ApplyFlags>>(rhs));
-}
-
-static_assert((TapFailHard | TapRetry) == safeCast<ApplyFlags>(0x30u), "ApplyFlags operator |");
-static_assert((TapRetry | TapFailHard) == safeCast<ApplyFlags>(0x30u), "ApplyFlags operator |");
-
-constexpr ApplyFlags
-operator&(ApplyFlags const& lhs, ApplyFlags const& rhs)
-{
-    return safeCast<ApplyFlags>(
-        safeCast<std::underlying_type_t<ApplyFlags>>(lhs) &
-        safeCast<std::underlying_type_t<ApplyFlags>>(rhs));
-}
-
-static_assert((TapFailHard & TapRetry) == TapNone, "ApplyFlags operator &");
-static_assert((TapRetry & TapFailHard) == TapNone, "ApplyFlags operator &");
-
-constexpr ApplyFlags
-operator~(ApplyFlags const& flags)
-{
-    return safeCast<ApplyFlags>(~safeCast<std::underlying_type_t<ApplyFlags>>(flags));
-}
-
-static_assert(~TapRetry == safeCast<ApplyFlags>(0xFFFFFFDFu), "ApplyFlags operator ~");
-
-inline ApplyFlags
-operator|=(ApplyFlags& lhs, ApplyFlags const& rhs)
-{
-    lhs = lhs | rhs;
-    return lhs;
-}
-
-inline ApplyFlags
-operator&=(ApplyFlags& lhs, ApplyFlags const& rhs)
-{
-    lhs = lhs & rhs;
-    return lhs;
-}
+};
 
 //------------------------------------------------------------------------------
 

include/xrpl/protocol/AccountID.h

@@ -101,22 +101,6 @@ operator<<(std::ostream& os, AccountID const& x)
     return os;
 }
 
-/**
- * Initialize the global cache used to map AccountID to base58 conversions.
- *
- * The cache is optional and need not be initialized. But because conversion
- * is expensive (it requires a SHA-256 operation) in most cases the overhead
- * of the cache is worth the benefit.
- *
- * @param count The number of entries the cache should accommodate. Zero will
- *              disable the cache, releasing any memory associated with it.
- *
- * @note The function will only initialize the cache the first time it is
- *       invoked. Subsequent invocations do nothing.
- */
-void
-initAccountIdCache(std::size_t count);
-
 }  // namespace xrpl
 
 //------------------------------------------------------------------------------

include/xrpl/protocol/KnownFormats.h

@@ -1,10 +1,10 @@
 #pragma once
 
 #include <xrpl/basics/contract.h>
-#include <xrpl/beast/type_name.h>
 #include <xrpl/protocol/SOTemplate.h>
 
 #include <boost/container/flat_map.hpp>
+#include <boost/core/type_name.hpp>
 
 #include <algorithm>
 #include <cstddef>
@@ -84,7 +84,7 @@ public:
      * Derived classes will load the object with all the known formats.
      */
 private:
-    KnownFormats() : name_(beast::typeName<Derived>())
+    KnownFormats() : name_(boost::core::type_name<Derived>())
     {
     }
 

include/xrpl/protocol/STPathSet.h

@@ -2,6 +2,7 @@
 
 #include <xrpl/basics/CountedObject.h>
 #include <xrpl/basics/UnorderedContainers.h>
+#include <xrpl/basics/enum_bitops.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/json/json_value.h>
 #include <xrpl/protocol/AccountID.h>
@@ -15,6 +16,7 @@
 #include <cstdint>
 #include <memory>
 #include <optional>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -22,18 +24,8 @@ namespace xrpl {
 
 class STPathElement final : public CountedObject<STPathElement>
 {
-    unsigned int type_;
-    AccountID accountID_;
-    PathAsset assetID_;
-    AccountID issuerID_;
-
-    bool isOffer_;
-    std::size_t hashValue_;
-
 public:
-    // Bitwise values (typeCurrency | typeMPT)
-    // NOLINTNEXTLINE(cppcoreguidelines-use-enum-class)
-    enum Type {
+    enum class Type : std::uint8_t {
         TypeNone = 0x00,
         TypeAccount = 0x01,   // Rippling through an account (vs taking an offer).
         TypeCurrency = 0x10,  // Currency follows.
@@ -45,6 +37,8 @@ public:
         // Combination of all types.
     };
 
+    using enum Type;
+
     STPathElement();
     STPathElement(STPathElement const&) = default;
     STPathElement&
@@ -62,42 +56,42 @@ public:
         bool forceAsset = false);
 
     STPathElement(
-        unsigned int uType,
+        Type type,
         AccountID const& account,
         PathAsset const& asset,
         AccountID const& issuer);
 
-    [[nodiscard]] std::uint32_t
-    getNodeType() const;
+    [[nodiscard]] Type
+    getNodeType() const noexcept;
 
     [[nodiscard]] bool
-    isOffer() const;
+    isOffer() const noexcept;
 
     [[nodiscard]] bool
-    isAccount() const;
+    isAccount() const noexcept;
 
     [[nodiscard]] bool
-    hasIssuer() const;
+    hasIssuer() const noexcept;
 
     [[nodiscard]] bool
-    hasCurrency() const;
+    hasCurrency() const noexcept;
 
     [[nodiscard]] bool
-    hasMPT() const;
+    hasMPT() const noexcept;
 
     [[nodiscard]] bool
-    hasAsset() const;
+    hasAsset() const noexcept;
 
     [[nodiscard]] bool
-    isNone() const;
+    isNone() const noexcept;
 
     // Nodes are either an account ID or a offer prefix. Offer prefixs denote a
     // class of offers.
     [[nodiscard]] AccountID const&
-    getAccountID() const;
+    getAccountID() const noexcept;
 
     [[nodiscard]] PathAsset const&
-    getPathAsset() const;
+    getPathAsset() const noexcept;
 
     [[nodiscard]] Currency const&
     getCurrency() const;
@@ -106,17 +100,35 @@ public:
     getMPTID() const;
 
     [[nodiscard]] AccountID const&
-    getIssuerID() const;
+    getIssuerID() const noexcept;
 
     [[nodiscard]] bool
-    isType(Type const& pe) const;
+    isType(Type pe) const noexcept;
 
-    bool
-    operator==(STPathElement const& t) const;
+    friend bool
+    operator==(STPathElement const& lhs, STPathElement const& rhs) noexcept
+    {
+        return lhs.isType(TypeAccount) == rhs.isType(TypeAccount) &&
+            lhs.hashValue_ == rhs.hashValue_ && lhs.accountID_ == rhs.accountID_ &&
+            lhs.assetID_ == rhs.assetID_ && lhs.issuerID_ == rhs.issuerID_;
+    }
 
 private:
     static std::size_t
     getHash(STPathElement const& element);
+
+    Type type_;
+    AccountID accountID_;
+    PathAsset assetID_;
+    AccountID issuerID_;
+
+    bool isOffer_;
+    std::size_t hashValue_;
+};
+
+template <>
+struct enum_bitops::OptIn<STPathElement::Type> : std::true_type
+{
 };
 
 template <class Hasher>
@@ -124,7 +136,7 @@ void
 hash_append(Hasher& h, STPathElement const& e) noexcept
 {
     using beast::hash_append;
-    hash_append(h, (e.getNodeType() & STPathElement::TypeAccount) != 0u);
+    hash_append(h, e.isType(STPathElement::TypeAccount));
     hash_append(h, e.getAccountID());
     hash_append(h, e.getPathAsset());
     hash_append(h, e.getIssuerID());
@@ -404,11 +416,11 @@ inline STPathElement::STPathElement(
 }
 
 inline STPathElement::STPathElement(
-    unsigned int uType,
+    Type type,
     AccountID const& account,
     PathAsset const& asset,
     AccountID const& issuer)
-    : type_(uType)
+    : type_(type)
     , accountID_(account)
     , assetID_(asset)
     , issuerID_(issuer)
@@ -423,56 +435,56 @@ inline STPathElement::STPathElement(
     hashValue_ = getHash(*this);
 }
 
-inline std::uint32_t
-STPathElement::getNodeType() const
+inline STPathElement::Type
+STPathElement::getNodeType() const noexcept
 {
     return type_;
 }
 
 inline bool
-STPathElement::isOffer() const
+STPathElement::isOffer() const noexcept
 {
     return isOffer_;
 }
 
 inline bool
-STPathElement::isAccount() const
+STPathElement::isAccount() const noexcept
 {
     return !isOffer();
 }
 
 inline bool
-STPathElement::isType(Type const& pe) const
+STPathElement::isType(Type pe) const noexcept
 {
-    return (type_ & pe) != 0u;
+    return (type_ & pe) != STPathElement::TypeNone;
 }
 
 inline bool
-STPathElement::hasIssuer() const
+STPathElement::hasIssuer() const noexcept
 {
     return isType(STPathElement::TypeIssuer);
 }
 
 inline bool
-STPathElement::hasCurrency() const
+STPathElement::hasCurrency() const noexcept
 {
     return isType(STPathElement::TypeCurrency);
 }
 
 inline bool
-STPathElement::hasMPT() const
+STPathElement::hasMPT() const noexcept
 {
     return isType(STPathElement::TypeMpt);
 }
 
 inline bool
-STPathElement::hasAsset() const
+STPathElement::hasAsset() const noexcept
 {
     return isType(STPathElement::TypeAsset);
 }
 
 inline bool
-STPathElement::isNone() const
+STPathElement::isNone() const noexcept
 {
     return getNodeType() == STPathElement::TypeNone;
 }
@@ -480,13 +492,13 @@ STPathElement::isNone() const
 // Nodes are either an account ID or a offer prefix. Offer prefixs denote a
 // class of offers.
 inline AccountID const&
-STPathElement::getAccountID() const
+STPathElement::getAccountID() const noexcept
 {
     return accountID_;
 }
 
 inline PathAsset const&
-STPathElement::getPathAsset() const
+STPathElement::getPathAsset() const noexcept
 {
     return assetID_;
 }
@@ -504,18 +516,11 @@ STPathElement::getMPTID() const
 }
 
 inline AccountID const&
-STPathElement::getIssuerID() const
+STPathElement::getIssuerID() const noexcept
 {
     return issuerID_;
 }
 
-inline bool
-STPathElement::operator==(STPathElement const& t) const
-{
-    return (type_ & TypeAccount) == (t.type_ & TypeAccount) && hashValue_ == t.hashValue_ &&
-        accountID_ == t.accountID_ && assetID_ == t.assetID_ && issuerID_ == t.issuerID_;
-}
-
 // ------------ STPath ------------
 
 inline STPath::STPath(std::vector<STPathElement> p) : path_(std::move(p))

include/xrpl/protocol/jss.h

@@ -392,6 +392,7 @@ JSS(max_ledger);                  // in/out: LedgerCleaner
 JSS(max_queue_size);              // out: TxQ
 JSS(max_spend_drops);             // out: AccountInfo
 JSS(max_spend_drops_total);       // out: AccountInfo
+JSS(maximum);
 JSS(mean);                        // out: get_aggregate_price
 JSS(median);                      // out: get_aggregate_price
 JSS(median_fee);                  // out: TxQ

include/xrpl/tx/ApplyContext.h

@@ -51,7 +51,8 @@ public:
         beast::Journal journal = beast::Journal{beast::Journal::getNullSink()})
         : ApplyContext(registry, base, std::nullopt, tx, preclaimResult, baseFee, flags, journal)
     {
-        XRPL_ASSERT((flags & TapBatch) == 0, "Batch apply flag should not be set");
+        XRPL_ASSERT(
+            (flags & ApplyFlags::Batch) == ApplyFlags::None, "Batch apply flag should not be set");
     }
 
     std::reference_wrapper<ServiceRegistry> registry;

include/xrpl/tx/Transactor.h

@@ -59,10 +59,11 @@ public:
         , parentBatchId(parentBatchId)
         , j(j)
     {
-        XRPL_ASSERT((flags & TapBatch) == TapBatch, "Batch apply flag should be set");
+        XRPL_ASSERT(
+            (flags & ApplyFlags::Batch) == ApplyFlags::Batch, "Batch apply flag should be set");
         XRPL_ASSERT_IF(
-            (flags & TapProposal) != TapNone,
-            (flags & TapDryRun) != TapNone,
+            (flags & ApplyFlags::Proposal) != ApplyFlags::None,
+            (flags & ApplyFlags::DryRun) != ApplyFlags::None,
             "xrpl::PreflightContext : proposal preflight implies dry run");
     }
 
@@ -74,10 +75,11 @@ public:
         beast::Journal j = beast::Journal{beast::Journal::getNullSink()})
         : registry(registry), tx(tx), rules(std::move(rules)), flags(flags), j(j)
     {
-        XRPL_ASSERT((flags & TapBatch) == 0, "Batch apply flag should not be set");
+        XRPL_ASSERT(
+            (flags & ApplyFlags::Batch) == ApplyFlags::None, "Batch apply flag should not be set");
         XRPL_ASSERT_IF(
-            (flags & TapProposal) != TapNone,
-            (flags & TapDryRun) != TapNone,
+            (flags & ApplyFlags::Proposal) != ApplyFlags::None,
+            (flags & ApplyFlags::DryRun) != ApplyFlags::None,
             "xrpl::PreflightContext : proposal preflight implies dry run");
     }
 
@@ -116,7 +118,7 @@ public:
         , j(j)
     {
         XRPL_ASSERT(
-            parentBatchId.has_value() == ((flags & TapBatch) == TapBatch),
+            parentBatchId.has_value() == ((flags & ApplyFlags::Batch) == ApplyFlags::Batch),
             "Parent Batch ID should be set if batch apply flag is set");
     }
 
@@ -129,7 +131,8 @@ public:
         beast::Journal j = beast::Journal{beast::Journal::getNullSink()})
         : PreclaimContext(registry, view, preflightResult, tx, flags, std::nullopt, j)
     {
-        XRPL_ASSERT((flags & TapBatch) == 0, "Batch apply flag should not be set");
+        XRPL_ASSERT(
+            (flags & ApplyFlags::Batch) == ApplyFlags::None, "Batch apply flag should not be set");
     }
 
     PreclaimContext&

include/xrpl/tx/applySteps.h

@@ -41,7 +41,7 @@ struct ApplyResult
 inline bool
 isTecClaimHardFail(TER ter, ApplyFlags flags)
 {
-    return isTecClaim(ter) && ((flags & TapRetry) == 0u);
+    return isTecClaim(ter) && ((flags & ApplyFlags::Retry) == ApplyFlags::None);
 }
 
 /**

src/libxrpl/basics/CountedObject.cpp

@@ -1,39 +0,0 @@
-#include <xrpl/basics/CountedObject.h>
-
-#include <algorithm>
-
-namespace xrpl {
-
-CountedObjects&
-CountedObjects::getInstance() noexcept
-{
-    static CountedObjects kInstance;
-
-    return kInstance;
-}
-
-CountedObjects::CountedObjects() noexcept : count_(0), head_(nullptr)
-{
-}
-
-CountedObjects::List
-CountedObjects::getCounts(int minimumThreshold) const
-{
-    List counts;
-
-    // When other operations are concurrent, the count
-    // might be temporarily less than the actual count.
-    counts.reserve(count_.load());
-
-    for (auto* ctr = head_.load(); ctr != nullptr; ctr = ctr->getNext())
-    {
-        if (ctr->getCount() >= minimumThreshold)
-            counts.emplace_back(ctr->getName(), ctr->getCount());
-    }
-
-    std::ranges::sort(counts);
-
-    return counts;
-}
-
-}  // namespace xrpl

src/libxrpl/nodestore/backend/RocksDBFactory.cpp

@@ -317,8 +317,8 @@ public:
             }
             else
             {
-                status = static_cast<Status>(
-                    static_cast<int>(Status::CustomCode) + unsafeCast<int>(getStatus.code()));
+                status = checkedCast<Status>(
+                    safeCast<int>(Status::CustomCode) + safeCast<int>(getStatus.code()));
 
                 JLOG(journal.error()) << getStatus.ToString();
             }

src/libxrpl/protocol/AccountID.cpp

@@ -8,6 +8,8 @@
 #include <xrpl/protocol/digest.h>
 #include <xrpl/protocol/tokens.h>
 
+#include <algorithm>
+#include <array>
 #include <atomic>
 #include <cstdint>
 #include <cstring>
@@ -19,85 +21,136 @@
 
 namespace xrpl {
 
-namespace detail {
+namespace {
 
-/**
- * Caches the base58 representations of AccountIDs
+/** If true, we implement a cache for account ID lookups.
+
+    This is generally a good idea and can improve performance, especially
+    when serving client requests.
+
+    The cache may generate warnings under some sanitizers; if you want to
+    disable caching, set this variable to false.
  */
-class AccountIdCache
+constexpr bool cacheAccountIDs = true;
+
+/** Represents a cached entry for the given AccountID.
+
+    We keep the size and alignment of the structure at 64 bytes to
+    make sure it fits within a cache line and avoid false sharing.
+ */
+struct alignas(64) CachedAccountID
 {
-private:
-    struct CachedAccountID
-    {
-        AccountID id;
-        char encoding[40] = {0};
-    };
+    /** The sequence lock for the entry.
 
-    // The actual cache
-    std::vector<CachedAccountID> cache_;
+        An even value means that the data is stable, whereas an odd
+        value indicates the data is being actively modified.
 
-    // We use a hash function designed to resist algorithmic complexity attacks
-    HardenedHash<> hasher_;
+        We use a 32-bit value to ensure that the counter will never
+        return to an observed value during a read window.
+     */
+    std::atomic<std::uint32_t> seq{0};
 
-    // 64 spinlocks, packed into a single 64-bit value
-    std::atomic<std::uint64_t> locks_ = 0;
+    /** The account id. */
+    AccountID id{};
 
-public:
-    AccountIdCache(std::size_t count) : cache_(count)
-    {
-        // This is non-binding, but we try to avoid wasting memory that
-        // is caused by overallocation.
-        cache_.shrink_to_fit();
-    }
+    /** The length of the cached encoding.
 
-    std::string
-    toBase58(AccountID const& id)
-    {
-        auto const index = hasher_(id) % cache_.size();
+        This field disambiguates collisions between ACCOUNT_ZERO and
+        never-written-to slots, since they would otherwise share the
+        same encoded bits.
+     */
+    std::uint8_t len = 0;
 
-        PackedSpinlock sl(locks_, index % 64);
-
-        {
-            std::scoped_lock const lock(sl);
-
-            // The check against the first character of the encoding ensures
-            // that we don't mishandle the case of the all-zero account:
-            if (cache_[index].encoding[0] != 0 && cache_[index].id == id)
-                return cache_[index].encoding;
-        }
-
-        auto ret = encodeBase58Token(TokenType::AccountID, id.data(), id.size());
-
-        XRPL_ASSERT(ret.size() <= 38, "xrpl::detail::AccountIdCache : maximum result size");
-
-        {
-            std::scoped_lock const lock(sl);
-            cache_[index].id = id;
-            std::strcpy(cache_[index].encoding, ret.c_str());
-        }
-
-        return ret;
-    }
+    /** The actual string encoding. */
+    char encoding[39] = {0};
 };
 
-}  // namespace detail
+static_assert(sizeof(CachedAccountID) == 64 && alignof(CachedAccountID) == 64);
 
-static std::unique_ptr<detail::AccountIdCache> gAccountIdCache;
+// The actual cache to use: a simple, direct-mapped, best-effort construct.
+//
+// We do not use a hardened hash for this because an AccountID is already
+// just cryptographically generated (i.e. uniformly distributed) bits and
+// there is no amplification, since collisions do not carry an additional
+// cost.
+//
+// The size is a "nice" power of 2 because it makes the calculation of an
+// index easier.
+constinit std::array<CachedAccountID, 65536> gAccountIdCache{};
 
-void
-initAccountIdCache(std::size_t count)
-{
-    if (!gAccountIdCache && count != 0)
-        gAccountIdCache = std::make_unique<detail::AccountIdCache>(count);
-}
+}  // namespace
 
 std::string
 toBase58(AccountID const& v)
 {
-    if (gAccountIdCache)
-        return gAccountIdCache->toBase58(v);
+    // Since the input bits are generated by a cryptographically secure
+    // hash construct, we can just pick any subset of them, no muss, no
+    // fuss.
+    auto const index = [&v]() -> std::uint16_t {
+        auto const data = v.data();
 
-    return encodeBase58Token(TokenType::AccountID, v.data(), v.size());
+        return static_cast<std::uint16_t>(data[0]) | (static_cast<std::uint16_t>(data[1]) << 8);
+    }();
+
+    if constexpr (cacheAccountIDs)
+    {
+        auto& slot = gAccountIdCache[index];
+
+        // This is the optimistic, store-free read path: a collision with a
+        // concurrent writer will be detected because the seq recheck fails
+        // and we fall through to the slow path.
+        //
+        // These unsynchronized reads of the slot fields are, formally, data
+        // races and, technically speaking, result in undefined behavior and
+        // a tool like TSAN might flag them. These should not have an impact
+        // on the correctness of the returned data: the sequence lock checks
+        // ensure we discard any data that was in flux.
+        if (auto const s0 = slot.seq.load(std::memory_order::acquire);
+            (s0 & 1) == 0 && slot.len != 0 && slot.id == v)
+        {
+            char buf[38];
+            auto const len = std::min<std::size_t>(slot.len, sizeof(buf));
+            std::memcpy(buf, slot.encoding, len);
+
+            // Prevents the loads above from sinking below the recheck; the
+            // acquire on s0 constrains later operations, not earlier ones.
+            std::atomic_thread_fence(std::memory_order::acquire);
+
+            // Everything read from the slot — the gates above and the bytes in
+            // buf — precedes this recheck and is validated by it. No slot access
+            // may follow it.
+            if (slot.seq.load(std::memory_order::relaxed) == s0)
+                return std::string(buf, len);
+        }
+    }
+
+    auto ret = encodeBase58Token(TokenType::AccountID, v.data(), v.size());
+
+    XRPL_ASSERT(!ret.empty() && ret.size() <= 38, "xrpl::toBase58 : maximum result size");
+
+    if constexpr (cacheAccountIDs)
+    {
+        auto& slot = gAccountIdCache[index];
+
+        // The CAS to an odd value excludes other writers; if it fails, another
+        // thread wrote or is writing into this slot. That is not a problem: we
+        // just don't store our result into the cache this time.
+        if (auto s0 = slot.seq.load(std::memory_order::relaxed); (s0 & 1) == 0 &&
+            slot.seq.compare_exchange_strong(s0, s0 + 1, std::memory_order::acquire))
+        {
+            slot.id = v;
+            slot.len = static_cast<std::uint8_t>(ret.size());
+            std::copy_n(ret.data(), ret.size(), slot.encoding);
+
+            // The acquire on the CAS above keeps the writes from becoming visible
+            // before the seqlock transitions to an odd value, which means readers
+            // can detect an in-progress write. This release publishes them before
+            // the seqlock transitions to an even value.
+            slot.seq.store(s0 + 2, std::memory_order::release);
+        }
+    }
+
+    return ret;
 }
 
 template <>

src/libxrpl/protocol/STPathSet.cpp

@@ -5,6 +5,7 @@
 #include <xrpl/basics/UnorderedContainers.h>
 #include <xrpl/basics/base_uint.h>
 #include <xrpl/basics/contract.h>
+#include <xrpl/basics/safe_cast.h>
 #include <xrpl/beast/hash/uhash.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/json/json_value.h>
@@ -17,9 +18,13 @@
 #include <xrpl/protocol/jss.h>
 
 #include <algorithm>
+#include <concepts>
 #include <cstddef>
+#include <cstdint>
 #include <memory>
+#include <optional>
 #include <stdexcept>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -36,10 +41,10 @@ STPathElement::getHash(STPathElement const& element)
     //            important. We don't even really need to fully hash the whole
     //            base_uint here, as a few bytes would do for our use.
     //
-    // The note above is only true because the result of this function reaches
-    // nothing but STPathElement::operator==, where it is a fast-reject
-    // prefilter ahead of the field comparisons that decide the answer.  Do not
-    // use it to key a container.
+    // The note above is only true because the result of this function is only
+    // used by the STPathElement equality operator as a fast-reject prefilter,
+    // ahead of the field comparisons that then decide the answer. Do not use
+    // it to key a container.
 
     for (auto const x : element.getAccountID())
         hashAccount += (hashAccount * 257) ^ x;
@@ -106,12 +111,38 @@ STPathSet::operator=(STPathSet const& other)
 
 STPathSet::STPathSet(SerialIter& sit, SField const& name) : STBase(name)
 {
-    std::vector<STPathElement> path;
-    for (;;)
-    {
-        int const iType = sit.get8();
+    using enum STPathElement::Type;
 
-        if (iType == STPathElement::TypeNone || iType == STPathElement::TypeBoundary)
+    auto parsePathElementType = [](std::underlying_type_t<STPathElement::Type> byte) noexcept
+        -> std::optional<STPathElement::Type> {
+        if (byte == std::to_underlying(TypeBoundary))
+            return TypeBoundary;
+
+        constexpr auto knownBits = static_cast<std::underlying_type_t<STPathElement::Type>>(
+            std::to_underlying(TypeAccount) | std::to_underlying(TypeCurrency) |
+            std::to_underlying(TypeIssuer) | std::to_underlying(TypeMpt));
+
+        if ((byte & ~knownBits) != 0)
+            return std::nullopt;
+
+        return static_cast<STPathElement::Type>(byte);
+    };
+
+    std::vector<STPathElement> path;
+
+    std::optional<STPathElement::Type> type;
+
+    do
+    {
+        type = parsePathElementType(sit.get8());
+
+        if (!type)
+        {
+            JLOG(debugLog().error()) << "Bad path element in pathset";
+            Throw<std::runtime_error>("bad path element");
+        }
+
+        if (type == TypeNone || type == TypeBoundary)
         {
             if (path.empty())
             {
@@ -122,28 +153,11 @@ STPathSet::STPathSet(SerialIter& sit, SField const& name) : STBase(name)
             // Move rather than converting the vector to an STPath by copy.
             value_.emplace_back(std::move(path));
             path.clear();
-
-            if (iType == STPathElement::TypeNone)
-                return;
-        }
-        else if ((iType & ~STPathElement::TypeAll) != 0)
-        {
-            JLOG(debugLog().error()) << "Bad path element " << iType << " in pathset";
-            Throw<std::runtime_error>("bad path element");
         }
         else
         {
-            auto const hasAccount = (iType & STPathElement::TypeAccount) != 0u;
-            auto const hasCurrency = (iType & STPathElement::TypeCurrency) != 0u;
-            auto const hasIssuer = (iType & STPathElement::TypeIssuer) != 0u;
-            auto const hasMPT = (iType & STPathElement::TypeMpt) != 0u;
-
-            AccountID account;
-            PathAsset asset;
-            AccountID issuer;
-
-            if (hasAccount)
-                account = sit.get160();
+            bool const hasCurrency = ((*type & TypeCurrency) == TypeCurrency);
+            bool const hasMPT = ((*type & TypeMpt) == TypeMpt);
 
             if (hasCurrency && hasMPT)
             {
@@ -151,18 +165,26 @@ STPathSet::STPathSet(SerialIter& sit, SField const& name) : STBase(name)
                 Throw<std::runtime_error>("bad path element: MPT and Currency");
             }
 
+            AccountID account;
+            AccountID issuer;
+
+            if ((*type & TypeAccount) == TypeAccount)
+                account = sit.get160();
+
+            PathAsset asset;
+
             if (hasCurrency)
                 asset = Currency::fromRaw(sit.get160());
 
             if (hasMPT)
                 asset = sit.get192();
 
-            if (hasIssuer)
+            if ((*type & TypeIssuer) == TypeIssuer)
                 issuer = sit.get160();
 
             path.emplace_back(account, asset, issuer, hasCurrency || hasMPT);
         }
-    }
+    } while (type != TypeNone);
 }
 
 STBase*
@@ -216,24 +238,22 @@ STPath::getJson(JsonOptions) const
     for (auto const& it : path_)
     {
         json::Value elem(json::ValueType::Object);
-        auto const iType = it.getNodeType();
 
-        elem[jss::type] = iType;
+        elem[jss::type] = safeCast<std::uint32_t>(it.getNodeType());
 
-        if ((iType & STPathElement::TypeAccount) != 0u)
+        if (it.isType(STPathElement::TypeAccount))
             elem[jss::account] = to_string(it.getAccountID());
 
         XRPL_ASSERT(
-            ((iType & STPathElement::TypeCurrency) == 0u) ||
-                ((iType & STPathElement::TypeMpt) == 0u),
+            !(it.hasCurrency() && it.hasMPT()),
             "xrpl::STPath::getJson : not type Currency and MPT");
-        if ((iType & STPathElement::TypeCurrency) != 0u)
+        if (it.hasCurrency())
             elem[jss::currency] = to_string(it.getCurrency());
 
-        if ((iType & STPathElement::TypeMpt) != 0u)
+        if (it.hasMPT())
             elem[jss::mpt_issuance_id] = to_string(it.getMPTID());
 
-        if ((iType & STPathElement::TypeIssuer) != 0u)
+        if (it.hasIssuer())
             elem[jss::issuer] = to_string(it.getIssuerID());
 
         ret.append(elem);
@@ -265,34 +285,42 @@ STPathSet::add(Serializer& s) const
     XRPL_ASSERT(getFName().fieldType == STI_PATHSET, "xrpl::STPathSet::add : valid field type");
     bool first = true;
 
+    // Workaround, since `Serializer` does not accept strongly-typed enums
+    // yet. When support is added, the static_assert will trigger, and the
+    // lambda can be removed entirely.
+    auto const toByte = [](std::same_as<STPathElement::Type> auto t) noexcept {
+        static_assert(
+            !requires(Serializer& ser) { ser.add8(t); },
+            "Serializer::add8 now accepts STPathElement::Type directly; remove toByte.");
+        return std::to_underlying(t);
+    };
+
     for (auto const& spPath : value_)
     {
         if (!first)
-            s.add8(STPathElement::TypeBoundary);
+            s.add8(toByte(STPathElement::TypeBoundary));
 
         for (auto const& speElement : spPath)
         {
-            int const iType = speElement.getNodeType();
+            s.add8(toByte(speElement.getNodeType()));
 
-            s.add8(iType);
-
-            if ((iType & STPathElement::TypeAccount) != 0u)
+            if (speElement.isType(STPathElement::TypeAccount))
                 s.addBitString(speElement.getAccountID());
 
-            if ((iType & STPathElement::TypeMpt) != 0u)
+            if (speElement.hasMPT())
                 s.addBitString(speElement.getMPTID());
 
-            if ((iType & STPathElement::TypeCurrency) != 0u)
+            if (speElement.hasCurrency())
                 s.addBitString(speElement.getCurrency());
 
-            if ((iType & STPathElement::TypeIssuer) != 0u)
+            if (speElement.hasIssuer())
                 s.addBitString(speElement.getIssuerID());
         }
 
         first = false;
     }
 
-    s.add8(STPathElement::TypeNone);
+    s.add8(toByte(STPathElement::TypeNone));
 }
 
 }  // namespace xrpl

src/libxrpl/tx/ApplyContext.cpp

@@ -38,7 +38,7 @@ ApplyContext::ApplyContext(
     , parentBatchId_(parentBatchId)
 {
     XRPL_ASSERT(
-        parentBatchId.has_value() == ((flags_ & TapBatch) == TapBatch),
+        parentBatchId.has_value() == ((flags_ & ApplyFlags::Batch) == ApplyFlags::Batch),
         "Parent Batch ID should be set if batch apply flag is set");
     view_.emplace(&base_, flags_);
 }
@@ -53,13 +53,14 @@ std::optional<TxMeta>
 ApplyContext::apply(TER ter)
 {
     // NOLINTNEXTLINE(bugprone-unchecked-optional-access) view_ emplaced in constructor
-    return view_->apply(base_, tx, ter, parentBatchId_, (flags_ & TapDryRun) != 0u, journal);
+    return view_->apply(
+        base_, tx, ter, parentBatchId_, (flags_ & ApplyFlags::DryRun) != ApplyFlags::None, journal);
 }
 
 void
 ApplyContext::addOrderBook(Book const& book)
 {
-    if ((flags_ & TapDryRun) == TapNone)
+    if ((flags_ & ApplyFlags::DryRun) == ApplyFlags::None)
         registry.get().getOrderBookDB().addOrderBook(book);
 }
 

src/libxrpl/tx/Transactor.cpp

@@ -134,7 +134,7 @@ preflightCheckSigningKey(STObject const& sigObject, beast::Journal j)
 std::optional<NotTEC>
 preflightCheckSimulateKeys(ApplyFlags flags, STObject const& sigObject, beast::Journal j)
 {
-    if ((flags & TapDryRun) != 0u)  // simulation
+    if ((flags & ApplyFlags::DryRun) != ApplyFlags::None)  // simulation
     {
         std::optional<Slice> const signature = sigObject[~sfTxnSignature];
         if (signature && !signature->empty())
@@ -510,7 +510,8 @@ Transactor::minimumFee(
     Fees const& fees,
     ApplyFlags flags)
 {
-    return scaleFeeLoad(baseFee, registry.getFeeTrack(), fees, (flags & TapUnlimited) != 0u);
+    return scaleFeeLoad(
+        baseFee, registry.getFeeTrack(), fees, (flags & ApplyFlags::Unlimited) != ApplyFlags::None);
 }
 
 TER
@@ -521,7 +522,7 @@ Transactor::checkFee(PreclaimContext const& ctx, XRPAmount baseFee)
 
     auto const feePaid = ctx.tx[sfFee].xrp();
 
-    if ((ctx.flags & TapBatch) != 0u)
+    if ((ctx.flags & ApplyFlags::Batch) != ApplyFlags::None)
     {
         if (feePaid == beast::kZero)
             return tesSUCCESS;
@@ -951,7 +952,8 @@ Transactor::checkSign(
         return tesSUCCESS;
     }
 
-    if (((flags & TapDryRun) != 0u) && pkSigner.empty() && !sigObject.isFieldPresent(sfSigners))
+    if (((flags & ApplyFlags::DryRun) != ApplyFlags::None) && pkSigner.empty() &&
+        !sigObject.isFieldPresent(sfSigners))
     {
         // simulate: skip signature validation when neither SigningPubKey nor
         // Signers are provided
@@ -1122,7 +1124,7 @@ Transactor::checkMultiSign(
         }
 
         XRPL_ASSERT(
-            (flags & TapDryRun) || !spk.empty(),
+            (flags & ApplyFlags::DryRun) != ApplyFlags::None || !spk.empty(),
             "xrpl::Transactor::checkMultiSign : non-empty signer or "
             "simulation");
         AccountID const signingAcctIDFromPubKey =
@@ -1604,7 +1606,7 @@ Transactor::operator()()
         if (ctx_.size() > kOversizeMetaDataCap)
             result = tecOVERSIZE;
 
-        if (isTecClaim(result) && ((view().flags() & TapFailHard) != 0u))
+        if (isTecClaim(result) && ((view().flags() & ApplyFlags::FailHard) != ApplyFlags::None))
         {
             // If the TapFailHard flag is set, a tec result
             // must not do anything
@@ -1684,7 +1686,7 @@ Transactor::operator()()
     // Once we call apply, we will no longer be able to look at view()
     metadata = ctx_.apply(result);
 
-    if ((ctx_.flags() & TapDryRun) != 0u)
+    if ((ctx_.flags() & ApplyFlags::DryRun) != ApplyFlags::None)
         return logger(result, false, std::move(metadata));
 
     return logger(result, canApply, std::move(metadata));

src/libxrpl/tx/apply.cpp

@@ -215,7 +215,7 @@ applyBatchTransactions(
     auto applyOneTransaction = [&registry, &j, &parentBatchId, &batchView](STTx const& tx) {
         OpenView perTxBatchView(kBatchView, batchView);
 
-        auto const ret = apply(registry, perTxBatchView, parentBatchId, tx, TapBatch, j);
+        auto const ret = apply(registry, perTxBatchView, parentBatchId, tx, ApplyFlags::Batch, j);
         XRPL_ASSERT(
             ret.applied == (isTesSuccess(ret.ter) || isTecClaim(ret.ter)),
             "Inner transaction should not be applied");
@@ -274,7 +274,7 @@ applyTransaction(
 {
     // Returns false if the transaction has need not be retried.
     if (retryAssured)
-        flags = flags | TapRetry;
+        flags = flags | ApplyFlags::Retry;
 
     JLOG(j.debug()) << "TXN " << txn.getTransactionID() << (retryAssured ? "/retry" : "/final");
 

src/libxrpl/tx/applySteps.cpp

@@ -346,7 +346,8 @@ preflight(
     // builds; re-check the same invariant here so a release build can't
     // silently skip a proposed transaction's signature-presence checks
     // outside of a dry run.
-    if ((flags & TapProposal) != TapNone && (flags & TapDryRun) == TapNone)
+    if ((flags & ApplyFlags::Proposal) != ApplyFlags::None &&
+        (flags & ApplyFlags::DryRun) == ApplyFlags::None)
     {
         // LCOV_EXCL_START
         JLOG(j.fatal()) << "apply (preflight): TapProposal set without TapDryRun.";
@@ -377,7 +378,8 @@ preflight(
     PreflightContext const pfCtx(registry, tx, parentBatchId, rules, flags, j);
 
     // See the comment in the other preflight() overload above.
-    if ((flags & TapProposal) != TapNone && (flags & TapDryRun) == TapNone)
+    if ((flags & ApplyFlags::Proposal) != ApplyFlags::None &&
+        (flags & ApplyFlags::DryRun) == ApplyFlags::None)
     {
         // LCOV_EXCL_START
         JLOG(j.fatal()) << "apply (preflight): TapProposal set without TapDryRun.";

src/libxrpl/tx/paths/BookStep.cpp

@@ -985,7 +985,7 @@ std::optional<std::variant<Quality, AMMOffer<TIn, TOut>>>
 BookStep<TIn, TOut, TDerived>::tip(ReadView const& view) const
 {
     // This can be simplified (and sped up) if directories are never empty.
-    Sandbox sb(&view, TapNone);
+    Sandbox sb(&view, ApplyFlags::None);
     BookTip bt(sb, book_);
     auto const lobQuality = bt.step(j_) ? std::optional<Quality>(bt.quality()) : std::nullopt;
     // Multi-path offer generates an offer with the quality

src/libxrpl/tx/paths/PaySteps.cpp

@@ -57,10 +57,8 @@ checkNear(IOUAmount const& expected, IOUAmount const& actual)
 static bool
 isXRPAccount(STPathElement const& pe)
 {
-    if (pe.getNodeType() != STPathElement::TypeAccount)
-        return false;
-    return isXRP(pe.getAccountID());
-};
+    return pe.getNodeType() == STPathElement::TypeAccount && isXRP(pe.getAccountID());
+}
 
 static std::pair<TER, std::unique_ptr<Step>>
 toStep(
@@ -71,11 +69,8 @@ toStep(
 {
     auto& j = ctx.j;
 
-    if (ctx.isFirst && e1->isAccount() &&
-        ((e1->getNodeType() & STPathElement::TypeCurrency) != 0u) && e1->getPathAsset().isXRP())
-    {
+    if (ctx.isFirst && e1->isAccount() && e1->hasCurrency() && e1->getPathAsset().isXRP())
         return makeXrpEndpointStep(ctx, e1->getAccountID());
-    }
 
     if (ctx.isLast && isXRPAccount(*e1) && e2->isAccount())
         return makeXrpEndpointStep(ctx, e2->getAccountID());
@@ -117,15 +112,9 @@ toStep(
         // LCOV_EXCL_STOP
     }
 
-    XRPL_ASSERT(
-        (e2->getNodeType() & STPathElement::TypeAsset) ||
-            (e2->getNodeType() & STPathElement::TypeIssuer),
-        "xrpl::toStep : currency or issuer");
-    PathAsset const outAsset =
-        ((e2->getNodeType() & STPathElement::TypeAsset) != 0u) ? e2->getPathAsset() : curAsset;
-    auto const outIssuer = ((e2->getNodeType() & STPathElement::TypeIssuer) != 0u)
-        ? e2->getIssuerID()
-        : curAsset.getIssuer();
+    XRPL_ASSERT(e2->hasAsset() || e2->hasIssuer(), "xrpl::toStep : currency or issuer");
+    PathAsset const outAsset = e2->hasAsset() ? e2->getPathAsset() : curAsset;
+    auto const outIssuer = e2->hasIssuer() ? e2->getIssuerID() : curAsset.getIssuer();
 
     if (isXRP(curAsset) && outAsset.isXRP())
     {
@@ -197,16 +186,15 @@ toStrand(
     for (std::size_t i = 0; i < path.size(); ++i)
     {
         auto const& pe = path[i];
-        auto const t = pe.getNodeType();
 
-        if (((t & ~STPathElement::TypeAll) != 0u) || (t == 0u))
+        if ((pe.getNodeType() & ~STPathElement::TypeAll) != STPathElement::TypeNone || pe.isNone())
             return {temBAD_PATH, Strand{}};
 
-        bool const hasAccount = (t & STPathElement::TypeAccount) != 0u;
-        bool const hasIssuer = (t & STPathElement::TypeIssuer) != 0u;
-        bool const hasCurrency = (t & STPathElement::TypeCurrency) != 0u;
-        bool const hasMPT = (t & STPathElement::TypeMpt) != 0u;
-        bool const hasAsset = (t & STPathElement::TypeAsset) != 0u;
+        bool const hasAccount = pe.isType(STPathElement::TypeAccount);
+        bool const hasIssuer = pe.hasIssuer();
+        bool const hasCurrency = pe.hasCurrency();
+        bool const hasMPT = pe.hasMPT();
+        bool const hasAsset = pe.hasAsset();
 
         if (hasAccount && (hasIssuer || hasCurrency))
             return {temBAD_PATH, Strand{}};
@@ -250,9 +238,7 @@ toStrand(
     }();
 
     // Currency or MPT
-    auto hasAsset = [](STPathElement const pe) {
-        return pe.getNodeType() & STPathElement::TypeAsset;
-    };
+    auto hasAsset = [](STPathElement const& pe) { return pe.hasAsset(); };
 
     std::vector<STPathElement> normPath;
     // reserve enough for the path, the implied source, destination,

src/libxrpl/tx/transactors/account/AccountSet.cpp

@@ -187,7 +187,8 @@ AccountSet::preclaim(PreclaimContext const& ctx)
         if (!dirIsEmpty(ctx.view, keylet::ownerDir(id)))
         {
             JLOG(ctx.j.trace()) << "Retry: Owner directory not empty.";
-            return ((ctx.flags & TapRetry) != 0u) ? TER{terOWNERS} : TER{tecOWNERS};
+            return ((ctx.flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terOWNERS}
+                                                                         : TER{tecOWNERS};
         }
     }
 

src/libxrpl/tx/transactors/dex/OfferCreate.cpp

@@ -295,7 +295,8 @@ OfferCreate::checkAcceptAsset(
         JLOG(j.debug()) << "delay: can't receive IOUs from non-existent issuer: "
                         << to_string(asset.getIssuer());
 
-        return ((flags & TapRetry) != 0u) ? TER{terNO_ACCOUNT} : TER{tecNO_ISSUER};
+        return ((flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terNO_ACCOUNT}
+                                                                 : TER{tecNO_ISSUER};
     }
 
     // An account cannot create a trustline to itself, so no line can exist
@@ -318,7 +319,8 @@ OfferCreate::checkAcceptAsset(
                 {
                     JLOG(j.debug()) << "delay: can't receive IOUs from issuer with "
                                        "DisallowIncomingTrustline set";
-                    return ((flags & TapRetry) != 0u) ? TER{terNO_LINE} : TER{tecNO_LINE};
+                    return ((flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terNO_LINE}
+                                                                             : TER{tecNO_LINE};
                 }
             }
 
@@ -326,7 +328,8 @@ OfferCreate::checkAcceptAsset(
             {
                 if (!trustLine)
                 {
-                    return ((flags & TapRetry) != 0u) ? TER{terNO_LINE} : TER{tecNO_LINE};
+                    return ((flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terNO_LINE}
+                                                                             : TER{tecNO_LINE};
                 }
 
                 // Entries have a canonical representation, determined by a
@@ -342,7 +345,8 @@ OfferCreate::checkAcceptAsset(
                     JLOG(j.debug()) << "delay: can't receive IOUs from "
                                        "issuer without auth.";
 
-                    return ((flags & TapRetry) != 0u) ? TER{terNO_AUTH} : TER{tecNO_AUTH};
+                    return ((flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terNO_AUTH}
+                                                                             : TER{tecNO_AUTH};
                 }
             }
 

src/libxrpl/tx/transactors/lending/LoanSet.cpp

@@ -91,7 +91,8 @@ LoanSet::preflight(PreflightContext const& ctx)
     // A proposed LoanSet is stored unsigned; its CounterpartySignature is
     // collected on-ledger afterward, so its absence here is expected, not an
     // error (On-Chain Cosigner spec §5.3.1.2).
-    if (!tx.isFlag(tfInnerBatchTxn) && !counterPartySig && (ctx.flags & TapProposal) == 0)
+    if (!tx.isFlag(tfInnerBatchTxn) && !counterPartySig &&
+        (ctx.flags & ApplyFlags::Proposal) == ApplyFlags::None)
     {
         JLOG(ctx.j.warn()) << "LoanSet transaction must have a CounterpartySignature.";
         return temBAD_SIGNER;

src/libxrpl/tx/transactors/proposal/TransactionProposalCreate.cpp

@@ -54,8 +54,8 @@ TransactionProposalCreate::preflight(PreflightContext const& ctx)
     try
     {
         STTx const stx{STObject{proposedTx}};
-        auto const inner =
-            xrpl::preflight(ctx.registry, ctx.rules, stx, TapDryRun | TapProposal, ctx.j);
+        auto const inner = xrpl::preflight(
+            ctx.registry, ctx.rules, stx, ApplyFlags::DryRun | ApplyFlags::Proposal, ctx.j);
         if (!isTesSuccess(inner.ter))
         {
             JLOG(ctx.j.debug()) << "TransactionProposalCreate: proposed txn "

src/libxrpl/tx/transactors/sponsor/SponsorshipTransfer.cpp

@@ -205,7 +205,7 @@ SponsorshipTransfer::preflight(PreflightContext const& ctx)
     // is collected on-ledger afterward, so its absence here is expected, not
     // an error (On-Chain Cosigner spec §5.3.1.2).
     if (isAccountReserveSponsorship && !ctx.tx.isFieldPresent(sfSponsorSignature) &&
-        (ctx.flags & TapProposal) == 0)
+        (ctx.flags & ApplyFlags::Proposal) == ApplyFlags::None)
     {
         JLOG(ctx.j.debug()) << "preflight: account sponsorship requires sfSponsorSignature";
         return temMALFORMED;

src/libxrpl/tx/transactors/system/Batch.cpp

@@ -359,7 +359,8 @@ Batch::preflight(PreflightContext const& ctx)
         // TapBatch — PreflightContext with a parentBatchId requires it.
         // LoanSet already short-circuits on tfInnerBatchTxn; it is also in
         // kDisabledTxTypes, so it never reaches this call.
-        ApplyFlags const innerFlags = TapBatch | (ctx.flags & (TapProposal | TapDryRun));
+        ApplyFlags const innerFlags =
+            ApplyFlags::Batch | (ctx.flags & (ApplyFlags::Proposal | ApplyFlags::DryRun));
         if (auto const preflightResult =
                 xrpl::preflight(ctx.registry, ctx.rules, parentBatchId, stx, innerFlags, ctx.j);
             !isTesSuccess(preflightResult.ter))
@@ -431,7 +432,7 @@ Batch::preflightSigValidated(PreflightContext const& ctx)
     // A proposed Batch is stored unsigned; its BatchSigners are collected
     // on-ledger afterward, so the signer-presence match belongs to submission
     // time, not proposal creation (On-Chain Cosigner spec §5.3.1.2).
-    if ((ctx.flags & TapProposal) != 0)
+    if ((ctx.flags & ApplyFlags::Proposal) != ApplyFlags::None)
         return tesSUCCESS;
 
     auto const parentBatchId = ctx.tx.getTransactionID();

src/test/app/AMMExtendedMPT_test.cpp

@@ -1890,7 +1890,7 @@ private:
             auto const flowResult = [&] {
                 STAmount const deliver(eth(51'000'000));
                 STAmount smax(btc(61'000'000));
-                PaymentSandbox sb(env.current().get(), TapNone);
+                PaymentSandbox sb(env.current().get(), ApplyFlags::None);
                 STPathSet paths;
                 auto ipe = [](MPTTester const& iss) {
                     return STPathElement(
@@ -1928,7 +1928,7 @@ private:
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
                 if (flowResult.removableOffers.empty())
                     return false;
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 for (auto const& o : flowResult.removableOffers)
                 {
                     if (auto ok = sb.peek(keylet::offer(o)))

src/test/app/AMMExtended_test.cpp

@@ -2049,7 +2049,7 @@ private:
             auto const flowResult = [&] {
                 STAmount const deliver(USD(51));
                 STAmount smax(BTC(61));
-                PaymentSandbox sb(env.current().get(), TapNone);
+                PaymentSandbox sb(env.current().get(), ApplyFlags::None);
                 STPathSet paths;
                 auto ipe = [](Issue const& iss) {
                     return STPathElement(
@@ -2087,7 +2087,7 @@ private:
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
                 if (flowResult.removableOffers.empty())
                     return false;
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 for (auto const& o : flowResult.removableOffers)
                 {
                     if (auto ok = sb.peek(keylet::offer(o)))

src/test/app/AMMMPT_test.cpp

@@ -4158,7 +4158,7 @@ private:
                 auto jtx = env.jt(tx, Seq(1), Fee(10));
                 env.app().config().features.erase(featureMPTokensV2);
                 PreflightContext const ctx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = AMMBid::checkExtraFeatures(ctx);
                 BEAST_EXPECT(pf == false);
                 env.app().config().features.insert(featureMPTokensV2);
@@ -4170,7 +4170,7 @@ private:
                 jtx.jv["Asset2"].removeMember("mpt_issuance_id");
                 jtx.stx = env.ust(jtx);
                 PreflightContext const ctx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = AMMBid::preflight(ctx);
                 BEAST_EXPECT(pf == temBAD_AMM_TOKENS);
             }

src/test/app/AMM_test.cpp

@@ -3263,7 +3263,7 @@ private:
                 auto jtx = env.jt(tx, Seq(1), Fee(baseFee));
                 env.app().config().features.erase(featureAMM);
                 PreflightContext const pfCtx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = Transactor::invokePreflight<AMMBid>(pfCtx);
                 BEAST_EXPECT(pf == temDISABLED);
                 env.app().config().features.insert(featureAMM);
@@ -3274,7 +3274,7 @@ private:
                 jtx.jv["TxnSignature"] = "deadbeef";
                 jtx.stx = env.ust(jtx);
                 PreflightContext const pfCtx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = Transactor::invokePreflight<AMMBid>(pfCtx);
                 BEAST_EXPECT(!isTesSuccess(pf));
             }
@@ -3285,7 +3285,7 @@ private:
                 jtx.jv["Asset2"].removeMember("issuer");
                 jtx.stx = env.ust(jtx);
                 PreflightContext const pfCtx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = Transactor::invokePreflight<AMMBid>(pfCtx);
                 BEAST_EXPECT(pf == temBAD_AMM_TOKENS);
             }

src/test/app/AccountSet_test.cpp

@@ -594,7 +594,7 @@ public:
         stx->at(sfSigningPubKey) = makeSlice(std::string("badkey"));
 
         env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-            auto const result = xrpl::apply(env.app(), view, *stx, TapNone, j);
+            auto const result = xrpl::apply(env.app(), view, *stx, ApplyFlags::None, j);
             BEAST_EXPECT(result.ter == temBAD_SIGNATURE);
             BEAST_EXPECT(!result.applied);
             return result.applied;

src/test/app/Batch_test.cpp

@@ -436,7 +436,7 @@ class Batch_test : public beast::unit_test::Suite
         {
             auto jtx = env.jt(pay(alice, bob, XRP(1)), Txflags(tfInnerBatchTxn));
             PreflightContext const pfCtx(
-                env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
             auto const pf = Transactor::invokePreflight<Payment>(pfCtx);
             BEAST_EXPECT(pf == temINVALID_INNER_BATCH);
         }
@@ -451,7 +451,7 @@ class Batch_test : public beast::unit_test::Suite
                 disabledEnv.app(),
                 *jtx.stx,
                 disabledEnv.current()->rules(),
-                TapNone,
+                ApplyFlags::None,
                 disabledEnv.journal);
             auto const pf = Transactor::invokePreflight<Payment>(pfCtx);
             BEAST_EXPECT(pf == temINVALID_FLAG);
@@ -462,7 +462,12 @@ class Batch_test : public beast::unit_test::Suite
         {
             auto jtx = env.jt(pay(alice, bob, XRP(1)));
             PreflightContext const pfCtx(
-                env.app(), *jtx.stx, UInt256{1}, env.current()->rules(), TapBatch, env.journal);
+                env.app(),
+                *jtx.stx,
+                UInt256{1},
+                env.current()->rules(),
+                ApplyFlags::Batch,
+                env.journal);
             auto const pf = Transactor::invokePreflight<Payment>(pfCtx);
             BEAST_EXPECT(pf == temINVALID_INNER_BATCH);
         }
@@ -1590,7 +1595,7 @@ class Batch_test : public beast::unit_test::Suite
                 batch::Sig(std::vector<Reg>(kMaxBatchSigners + 1, bob)));
 
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-                auto const result = xrpl::apply(env.app(), view, *jt.stx, TapNone, j);
+                auto const result = xrpl::apply(env.app(), view, *jt.stx, ApplyFlags::None, j);
                 BEAST_EXPECT(!result.applied && result.ter == temARRAY_TOO_LARGE);
                 return result.applied;
             });
@@ -4391,7 +4396,7 @@ class Batch_test : public beast::unit_test::Suite
         BEAST_EXPECT(!passesLocalChecks(stx, reason));
         BEAST_EXPECT(reason == "Cannot submit pseudo transactions.");
         env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-            auto const result = xrpl::apply(env.app(), view, stx, TapNone, j);
+            auto const result = xrpl::apply(env.app(), view, stx, ApplyFlags::None, j);
             BEAST_EXPECT(!result.applied && result.ter == temINVALID_FLAG);
             return result.applied;
         });
@@ -5637,7 +5642,7 @@ class Batch_test : public beast::unit_test::Suite
                     obj.setFieldU32(sfFlags, tfInnerBatchTxn);
                 });
 
-                auto const result = xrpl::apply(env.app(), view, stx, TapNone, j);
+                auto const result = xrpl::apply(env.app(), view, stx, ApplyFlags::None, j);
                 // Must NOT be applied — signature was never checked
                 BEAST_EXPECT(!result.applied);
                 return false;

src/test/app/ConfidentialTransfer_test.cpp

@@ -1745,7 +1745,8 @@ class ConfidentialTransfer_test : public ConfidentialTransferTestBase
                 (*sle)[sfConfidentialBalanceVersion] = wrappedFrom;
                 view.rawReplace(sle);
 
-                auto const result = xrpl::apply(env.app(), view, *jt.stx, TapNone, env.journal);
+                auto const result =
+                    xrpl::apply(env.app(), view, *jt.stx, ApplyFlags::None, env.journal);
                 BEAST_EXPECT(result.ter == tesSUCCESS);
                 return result.applied;
             }));

src/test/app/Credentials_test.cpp

@@ -901,8 +901,7 @@ struct Credentials_test : public beast::unit_test::Suite
 
             {
                 testcase("deleteSLE fail, bad SLE.");
-                auto view =
-                    std::make_shared<ApplyViewImpl>(env.current().get(), ApplyFlags::TapNone);
+                auto view = std::make_shared<ApplyViewImpl>(env.current().get(), ApplyFlags::None);
                 auto ter = xrpl::credentials::deleteSLE(*view, {}, env.journal);
                 BEAST_EXPECT(ter == tecNO_ENTRY);
             }
@@ -1125,7 +1124,7 @@ struct Credentials_test : public beast::unit_test::Suite
         // Create an ApplyViewImpl on top of the current closed ledger
         // and corrupt it by erasing the issuer's account SLE
         auto const open = env.current();
-        ApplyViewImpl av(&*open, TapNone);
+        ApplyViewImpl av(&*open, ApplyFlags::None);
 
         // Erase the issuer's account to simulate ledger corruption
         auto sleIssuer = av.peek(keylet::account(issuer.id()));

src/test/app/EscrowToken_test.cpp

@@ -2795,7 +2795,7 @@ struct EscrowToken_test : public beast::unit_test::Suite
 
             auto const seq1 = env.seq(alice);
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 auto sleNew =
                     std::make_shared<SLE>(keylet::escrow(alice, SeqProxy::rawSequence(seq1)));
                 MPTIssue const mpt{MPTIssue{makeMptID(1, AccountID(0x4985601))}};
@@ -3023,7 +3023,7 @@ struct EscrowToken_test : public beast::unit_test::Suite
 
             auto const seq1 = env.seq(alice);
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 auto sleNew =
                     std::make_shared<SLE>(keylet::escrow(alice, SeqProxy::rawSequence(seq1)));
                 MPTIssue const mpt{MPTIssue{makeMptID(1, AccountID(0x4985601))}};

src/test/app/Escrow_test.cpp

@@ -1302,8 +1302,8 @@ struct Escrow_test : public beast::unit_test::Suite
                 escrow::kFinishTime(env.now() + 1s),
                 Seq(1),
                 Fee(baseFee));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jtx.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jtx.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(baseFee));
@@ -1312,8 +1312,8 @@ struct Escrow_test : public beast::unit_test::Suite
 
         {
             auto const jtx = env.jt(escrow::cancel("bob", "alice", 3), Seq(1), Fee(baseFee));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jtx.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jtx.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(baseFee));
@@ -1322,8 +1322,8 @@ struct Escrow_test : public beast::unit_test::Suite
 
         {
             auto const jtx = env.jt(escrow::finish("bob", "alice", 3), Seq(1), Fee(baseFee));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jtx.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jtx.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(baseFee));

src/test/app/FeeVote_test.cpp

@@ -134,7 +134,7 @@ createInvalidFeeTx(
 bool
 applyFeeAndTestResult(jtx::Env& env, OpenView& view, STTx const& tx)
 {
-    auto const res = apply(env.app(), view, tx, ApplyFlags::TapNone, env.journal);
+    auto const res = apply(env.app(), view, tx, ApplyFlags::None, env.journal);
     return isTesSuccess(res.ter);
 }
 

src/test/app/FlowMPT_test.cpp

@@ -333,7 +333,7 @@ struct FlowMPT_test : public beast::unit_test::Suite
                 auto const flowResult = [&] {
                     STAmount const deliver(usd(5'100));
                     STAmount smax(btc(61));
-                    PaymentSandbox sb(env.current().get(), TapNone);
+                    PaymentSandbox sb(env.current().get(), ApplyFlags::None);
                     STPathSet paths;
                     auto ipe = [](Asset const& asset) {
                         return STPathElement(
@@ -371,7 +371,7 @@ struct FlowMPT_test : public beast::unit_test::Suite
                 env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
                     if (flowResult.removableOffers.empty())
                         return false;
-                    Sandbox sb(&view, TapNone);
+                    Sandbox sb(&view, ApplyFlags::None);
                     for (auto const& o : flowResult.removableOffers)
                     {
                         if (auto ok = sb.peek(keylet::offer(o)))

src/test/app/Flow_test.cpp

@@ -476,7 +476,7 @@ struct Flow_test : public beast::unit_test::Suite
             auto const flowResult = [&] {
                 STAmount const deliver(usd(51));
                 STAmount smax(btc(61));
-                PaymentSandbox sb(env.current().get(), TapNone);
+                PaymentSandbox sb(env.current().get(), ApplyFlags::None);
                 STPathSet paths;
                 auto ipe = [](Issue const& iss) {
                     return STPathElement(
@@ -514,7 +514,7 @@ struct Flow_test : public beast::unit_test::Suite
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
                 if (flowResult.removableOffers.empty())
                     return false;
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 for (auto const& o : flowResult.removableOffers)
                 {
                     if (auto ok = sb.peek(keylet::offer(o)))

src/test/app/LedgerHistory_test.cpp

@@ -59,7 +59,7 @@ public:
         if (stx)
         {
             OpenView accum(&*res);
-            applyTransaction(env.app(), accum, *stx, false, TapNone, env.journal);
+            applyTransaction(env.app(), accum, *stx, false, ApplyFlags::None, env.journal);
             accum.apply(*res);
         }
         res->updateSkipList();

src/test/app/LedgerReplay_test.cpp

@@ -90,7 +90,7 @@ struct LedgerReplay_test : public beast::unit_test::Suite
         auto const lastClosedParent = ledgerMaster.getLedgerByHash(lastClosed->header().parentHash);
 
         auto const replayed = buildLedger(
-            LedgerReplay(lastClosedParent, lastClosed), TapNone, env.app(), env.journal);
+            LedgerReplay(lastClosedParent, lastClosed), ApplyFlags::None, env.app(), env.journal);
 
         BEAST_EXPECT(replayed->header().hash == lastClosed->header().hash);
     }
@@ -122,7 +122,7 @@ struct LedgerReplay_test : public beast::unit_test::Suite
         auto const lastClosedParent = ledgerMaster.getLedgerByHash(lastClosed->header().parentHash);
 
         auto const replayed = buildLedger(
-            LedgerReplay(lastClosedParent, lastClosed), TapNone, env.app(), env.journal);
+            LedgerReplay(lastClosedParent, lastClosed), ApplyFlags::None, env.app(), env.journal);
 
         BEAST_EXPECT(replayed->header().hash == lastClosed->header().hash);
     }

src/test/app/MPToken_test.cpp

@@ -4059,7 +4059,7 @@ class MPToken_test : public beast::unit_test::Suite
                                  TER expectedTer,
                                  std::optional<std::uint64_t> expectedOutstanding,
                                  std::string const& label) {
-            ApplyViewImpl av(&*env.current(), TapNone);
+            ApplyViewImpl av(&*env.current(), ApplyFlags::None);
             auto const ter =
                 accountSendMulti(av, issuer.id(), asset, receivers, env.app().getJournal("View"));
             BEAST_EXPECTS(ter == expectedTer, label);

src/test/app/NFTokenBurn_test.cpp

@@ -776,7 +776,13 @@ class NFTokenBurn_test : public beast::unit_test::Suite
                 test::StreamSink sink{beast::Severity::Warning};
                 beast::Journal const jlog{sink};
                 ApplyContext ac{
-                    env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                    env.app(),
+                    ov,
+                    tx,
+                    tesSUCCESS,
+                    env.current()->fees().base,
+                    ApplyFlags::None,
+                    jlog};
 
                 // Verify that the last page is present and contains one NFT.
                 auto lastNFTokenPage = ac.view().peek(keylet::nftokenPageMax(alice));
@@ -808,7 +814,13 @@ class NFTokenBurn_test : public beast::unit_test::Suite
                 test::StreamSink sink{beast::Severity::Warning};
                 beast::Journal const jlog{sink};
                 ApplyContext ac{
-                    env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                    env.app(),
+                    ov,
+                    tx,
+                    tesSUCCESS,
+                    env.current()->fees().base,
+                    ApplyFlags::None,
+                    jlog};
 
                 // Verify that the middle  page is present.
                 auto lastNFTokenPage = ac.view().peek(keylet::nftokenPageMax(alice));

src/test/app/PayStrandMPT_test.cpp

@@ -572,7 +572,7 @@ struct PayStrandMPT_test : public beast::unit_test::Suite
         inputs.defaultPathsAllowed = true;
         try
         {
-            PaymentSandbox sb{env.current().get(), TapNone};
+            PaymentSandbox sb{env.current().get(), ApplyFlags::None};
             {
                 auto const r = ::xrpl::path::RippleCalc::rippleCalculate(
                     sb,

src/test/app/PayStrand_test.cpp

@@ -768,7 +768,8 @@ struct PayStrand_test : public beast::unit_test::Suite
                 env,
                 usd,
                 std::nullopt,
-                STPath({STPathElement(0, xrpAccount(), xrpCurrency(), xrpAccount())}),
+                STPath({STPathElement(
+                    STPathElement::Type::TypeNone, xrpAccount(), xrpCurrency(), xrpAccount())}),
                 temBAD_PATH);
 
             // The same account can't appear more than once on a path
@@ -1076,7 +1077,7 @@ struct PayStrand_test : public beast::unit_test::Suite
         inputs.defaultPathsAllowed = true;
         try
         {
-            PaymentSandbox sb{env.current().get(), TapNone};
+            PaymentSandbox sb{env.current().get(), ApplyFlags::None};
             {
                 auto const r = ::xrpl::path::RippleCalc::rippleCalculate(
                     sb,

src/test/app/PseudoTx_test.cpp

@@ -82,7 +82,7 @@ struct PseudoTx_test : public beast::unit_test::Suite
             BEAST_EXPECT(!passesLocalChecks(stx, reason));
             BEAST_EXPECT(reason == "Cannot submit pseudo transactions.");
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-                auto const result = xrpl::apply(env.app(), view, stx, TapNone, j);
+                auto const result = xrpl::apply(env.app(), view, stx, ApplyFlags::None, j);
                 BEAST_EXPECT(!result.applied && result.ter == temINVALID);
                 return result.applied;
             });

src/test/app/Regression_test.cpp

@@ -103,7 +103,8 @@ struct Regression_test : public beast::unit_test::Suite
             auto const jt = env.jt(pay(env.master, "alice", aliceAmount));
             OpenView accum(&*next);
 
-            auto const result = xrpl::apply(env.app(), accum, *jt.stx, TapNone, env.journal);
+            auto const result =
+                xrpl::apply(env.app(), accum, *jt.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(result.ter));
             BEAST_EXPECT(result.applied);
 
@@ -126,7 +127,8 @@ struct Regression_test : public beast::unit_test::Suite
 
             OpenView accum(&*next);
 
-            auto const result = xrpl::apply(env.app(), accum, *jt.stx, TapNone, env.journal);
+            auto const result =
+                xrpl::apply(env.app(), accum, *jt.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(result.ter == tecINSUFF_FEE);
             BEAST_EXPECT(result.applied);
 
@@ -303,12 +305,11 @@ struct Regression_test : public beast::unit_test::Suite
                 return digest.asUInt256();
             }();
 
-            auto const mapCounts = [&](CountedObjects::List const& list) {
-                std::map<std::string, int> result;
-                for (auto const& e : list)
-                {
-                    result[e.first] = e.second;
-                }
+            auto const mapCounts = [] {
+                std::map<std::string, std::uint32_t> result;
+
+                for (auto const& c : gCountedObjects)
+                    result.emplace(c.name(), c.count());
 
                 return result;
             };
@@ -317,11 +318,11 @@ struct Regression_test : public beast::unit_test::Suite
             {
                 auto& cache = env.app().getCachedSLEs();
                 cache.del(*digest, false);  // NOLINT(bugprone-unchecked-optional-access)
-                auto const beforeCounts = mapCounts(CountedObjects::getInstance().getCounts(0));
+                auto const beforeCounts = mapCounts();
 
                 env(check::cash(alice, bobIndex, check::DeliverMin(XRP(100))), Ter(tecNO_ENTRY));
 
-                auto const afterCounts = mapCounts(CountedObjects::getInstance().getCounts(0));
+                auto const afterCounts = mapCounts();
 
                 using namespace std::string_literals;
                 BEAST_EXPECT(

src/test/app/Sponsor_test.cpp

@@ -915,8 +915,8 @@ public:
                 sponsor::SponseeAcc(alice),
                 Seq(1),
                 Fee(baseFee));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jt.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jt.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(baseFee));
@@ -931,8 +931,8 @@ public:
                 sponsor::SponseeAcc(alice),
                 Seq(1),
                 Fee(baseFee));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jt.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jt.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(baseFee));
@@ -946,8 +946,8 @@ public:
                 sponsor::SponseeAcc(alice),
                 Seq(1),
                 Fee(baseFee));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jt.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jt.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(baseFee));
@@ -2242,7 +2242,8 @@ public:
                 Seq(env.seq(alice)),
                 sponsor::As(carol, spfSponsorFee));
 
-            auto const result = xrpl::apply(env.app(), overlay, *jt.stx, TapNone, env.journal);
+            auto const result =
+                xrpl::apply(env.app(), overlay, *jt.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(result.ter == tecINSUFF_FEE);
             BEAST_EXPECT(result.applied);
 
@@ -2295,7 +2296,8 @@ public:
                 Fee(fixFee),
                 sponsor::As(sponsor, spfSponsorFee));
 
-            auto const pf = preflight(env.app(), overlay.rules(), *jt.stx, TapNone, env.journal);
+            auto const pf =
+                preflight(env.app(), overlay.rules(), *jt.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             auto const pc = preclaim(pf, env.app(), overlay);
             BEAST_EXPECT(isTesSuccess(pc.ter));

src/test/app/TheoreticalQuality_test.cpp

@@ -252,7 +252,7 @@ class TheoreticalQuality_test : public beast::unit_test::Suite
         std::shared_ptr<ReadView const> closed,
         std::optional<Quality> const& expectedQ = {})
     {
-        PaymentSandbox const sb(closed.get(), TapNone);
+        PaymentSandbox const sb(closed.get(), ApplyFlags::None);
         AMMContext ammContext(rcp.srcAccount, false);
 
         auto const sendMaxIssue = [&rcp]() -> std::optional<Asset> {

src/test/app/TxQ_test.cpp

@@ -989,7 +989,8 @@ public:
             Env::ParsedResult parsed;
 
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-                auto const result = xrpl::apply(env.app(), view, *jt.stx, TapNone, env.journal);
+                auto const result =
+                    xrpl::apply(env.app(), view, *jt.stx, ApplyFlags::None, env.journal);
                 parsed.ter = result.ter;
                 return result.applied;
             });
@@ -2424,8 +2425,8 @@ public:
         env.memoize("carol");
         {
             auto const jtx = env.jt(offerCancel(alice, 3), Seq(5), Fee(10));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jtx.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jtx.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(10));
@@ -2436,8 +2437,8 @@ public:
             auto usd = alice["USD"];
 
             auto const jtx = env.jt(trust("carol", usd(50000000)), Seq(1), Fee(10));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jtx.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jtx.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(10));
@@ -2446,8 +2447,8 @@ public:
 
         {
             auto const jtx = env.jt(ticket::create(alice, 1), Seq(1), Fee(10));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jtx.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jtx.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(10));
@@ -4002,7 +4003,7 @@ public:
         //  be callable via RPC.)
         env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
             auto const tx = env.jt(noop(alice), Seq(aliceSeq), Fee(openLedgerCost(env)));
-            auto const result = xrpl::apply(env.app(), view, *tx.stx, TapUnlimited, j);
+            auto const result = xrpl::apply(env.app(), view, *tx.stx, ApplyFlags::Unlimited, j);
             BEAST_EXPECT(isTesSuccess(result.ter) && result.applied);
             return result.applied;
         });
@@ -4070,7 +4071,7 @@ public:
         //  be callable via RPC.)
         env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
             auto const tx = env.jt(noop(alice), ticket::Use(tktSeq0 + 1), Fee(openLedgerCost(env)));
-            auto const result = xrpl::apply(env.app(), view, *tx.stx, TapUnlimited, j);
+            auto const result = xrpl::apply(env.app(), view, *tx.stx, ApplyFlags::Unlimited, j);
             BEAST_EXPECT(isTesSuccess(result.ter) && result.applied);
             return result.applied;
         });

src/test/app/invariants/InvariantsBase.cpp

@@ -122,7 +122,8 @@ InvariantsBase::doInvariantCheck(
     OpenView ov{*env.current()};
     test::StreamSink sink{beast::Severity::Warning};
     beast::Journal const jlog{sink};
-    ApplyContext ac{env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+    ApplyContext ac{
+        env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
 
     // Invariants normally run in the Transaction's "apply" (operator()) context, and can always
     // access global Rules.

src/test/app/invariants/InvariantsMisc_test.cpp

@@ -811,7 +811,13 @@ class InvariantsMisc_test : public InvariantsBase
                 test::StreamSink sink{beast::Severity::Warning};
                 beast::Journal const jlog{sink};
                 ApplyContext ac{
-                    env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                    env.app(),
+                    ov,
+                    tx,
+                    tesSUCCESS,
+                    env.current()->fees().base,
+                    ApplyFlags::None,
+                    jlog};
                 CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
                 auto sleLoan = ac.view().peek(loanKeylet);
@@ -866,7 +872,13 @@ class InvariantsMisc_test : public InvariantsBase
                 test::StreamSink sink{beast::Severity::Warning};
                 beast::Journal const jlog{sink};
                 ApplyContext ac{
-                    env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                    env.app(),
+                    ov,
+                    tx,
+                    tesSUCCESS,
+                    env.current()->fees().base,
+                    ApplyFlags::None,
+                    jlog};
                 CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
                 auto sleLoan = ac.view().peek(loanKeylet);
@@ -979,7 +991,13 @@ class InvariantsMisc_test : public InvariantsBase
                     test::StreamSink sink{beast::Severity::Warning};
                     beast::Journal const jlog{sink};
                     ApplyContext ac{
-                        env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                        env.app(),
+                        ov,
+                        tx,
+                        tesSUCCESS,
+                        env.current()->fees().base,
+                        ApplyFlags::None,
+                        jlog};
                     CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
                     auto sleLoan = ac.view().peek(loanKeylet);
@@ -1417,7 +1435,7 @@ class InvariantsMisc_test : public InvariantsBase
             test::StreamSink sink{beast::Severity::Warning};
             beast::Journal const jlog{sink};
             ApplyContext ac{
-                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
             CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
             auto sle = ac.view().peek(vaultKeylet);
@@ -1484,7 +1502,7 @@ class InvariantsMisc_test : public InvariantsBase
             test::StreamSink sink{beast::Severity::Warning};
             beast::Journal const jlog{sink};
             ApplyContext ac{
-                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
             CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
             // visitEntry only runs for entries the transaction touched, so
@@ -1541,7 +1559,8 @@ class InvariantsMisc_test : public InvariantsBase
         STTx const tx{ttACCOUNT_SET, [](STObject&) {}};
         test::StreamSink sink{beast::Severity::Warning};
         beast::Journal const jlog{sink};
-        ApplyContext ac{env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+        ApplyContext ac{
+            env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
         CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
         FailingTxInvariantCheck failing;

src/test/app/invariants/InvariantsPseudoAccount_test.cpp

@@ -581,7 +581,7 @@ class InvariantsPseudoAccount_test : public InvariantsBase
             test::StreamSink sink{beast::Severity::Warning};
             beast::Journal const jlog{sink};
             ApplyContext ac{
-                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
             CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
             auto sleBroker = ac.view().peek(brokerKeylet);
@@ -633,7 +633,7 @@ class InvariantsPseudoAccount_test : public InvariantsBase
             test::StreamSink sink{beast::Severity::Warning};
             beast::Journal const jlog{sink};
             ApplyContext ac{
-                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
             CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
             auto sleBroker = ac.view().peek(brokerKeylet);
@@ -681,7 +681,7 @@ class InvariantsPseudoAccount_test : public InvariantsBase
             test::StreamSink sink{beast::Severity::Warning};
             beast::Journal const jlog{sink};
             ApplyContext ac{
-                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
             CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
             auto sleBroker = ac.view().peek(brokerKeylet);

src/test/app/invariants/InvariantsVault_test.cpp

@@ -1088,7 +1088,13 @@ class InvariantsVault_test : public InvariantsBase
                 test::StreamSink sink{beast::Severity::Warning};
                 beast::Journal const jlog{sink};
                 ApplyContext ac{
-                    env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                    env.app(),
+                    ov,
+                    tx,
+                    tesSUCCESS,
+                    env.current()->fees().base,
+                    ApplyFlags::None,
+                    jlog};
                 CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
                 auto sleLoan = ac.view().peek(loanKeylet);
@@ -1140,7 +1146,7 @@ class InvariantsVault_test : public InvariantsBase
             test::StreamSink sink{beast::Severity::Warning};
             beast::Journal const jlog{sink};
             ApplyContext ac{
-                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
             CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
             auto sleLoan = ac.view().peek(loanKeylet);
@@ -1302,7 +1308,13 @@ class InvariantsVault_test : public InvariantsBase
                 test::StreamSink sink{beast::Severity::Warning};
                 beast::Journal const jlog{sink};
                 ApplyContext ac{
-                    env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                    env.app(),
+                    ov,
+                    tx,
+                    tesSUCCESS,
+                    env.current()->fees().base,
+                    ApplyFlags::None,
+                    jlog};
                 CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
                 auto sleLoan = ac.view().peek(loanKeylet);
@@ -1357,7 +1369,13 @@ class InvariantsVault_test : public InvariantsBase
                     test::StreamSink sink{beast::Severity::Warning};
                     beast::Journal const jlog{sink};
                     ApplyContext ac{
-                        env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                        env.app(),
+                        ov,
+                        tx,
+                        tesSUCCESS,
+                        env.current()->fees().base,
+                        ApplyFlags::None,
+                        jlog};
                     CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
                     auto sleLoan = ac.view().peek(loanKeylet);
@@ -1457,7 +1475,7 @@ class InvariantsVault_test : public InvariantsBase
             test::StreamSink sink{beast::Severity::Warning};
             beast::Journal const jlog{sink};
             ApplyContext ac{
-                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
             CurrentTransactionRulesGuard const rulesGuard(ov.rules());
 
             {

src/test/app/lending/LoanBroker_test.cpp

@@ -1249,7 +1249,8 @@ class LoanBroker_test : public beast::unit_test::Suite
         OpenView ov{*env.current()};
         test::StreamSink sink{beast::Severity::Warning};
         beast::Journal const jlog{sink};
-        ApplyContext ac{env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+        ApplyContext ac{
+            env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, ApplyFlags::None, jlog};
 
         if (auto sleBroker = ac.view().peek(keylet::loanBroker(brokerKeylet.key)))
         {
@@ -1262,7 +1263,7 @@ class LoanBroker_test : public beast::unit_test::Suite
 
         // Invoke preclaim against the mutated (ApplyView) view; triggers
         // nullptr deref
-        PreclaimContext const pctx{env.app(), ac.view(), tesSUCCESS, tx, TapNone, jlog};
+        PreclaimContext const pctx{env.app(), ac.view(), tesSUCCESS, tx, ApplyFlags::None, jlog};
         (void)LoanBrokerCoverDeposit::preclaim(pctx);
     }
 

src/test/app/vault/VaultScale_test.cpp

@@ -108,7 +108,7 @@ private:
             auto const peek = [keylet, &env, this](std::function<bool(SLE&, SLE&)> fn) -> bool {
                 return env.app().getOpenLedger().modify(
                     [&](OpenView& view, beast::Journal j) -> bool {
-                        Sandbox sb(&view, TapNone);
+                        Sandbox sb(&view, ApplyFlags::None);
                         auto vault = sb.peek(keylet::vault(keylet.key));
                         if (!BEAST_EXPECT(vault))
                             return false;

src/test/app/vault/VaultShares_test.cpp

@@ -300,7 +300,7 @@ private:
         env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
             for (auto const field : encryptedBalanceFields)
             {
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 auto const token = sb.peek(tokenKeylet);
                 if (!BEAST_EXPECT(token))
                     return false;

src/test/consensus/NegativeUNL_test.cpp

@@ -1902,7 +1902,7 @@ negUnlSizeTest(
 bool
 applyAndTestResult(jtx::Env& env, OpenView& view, STTx const& tx, bool pass)
 {
-    auto const res = apply(env.app(), view, tx, ApplyFlags::TapNone, env.journal);
+    auto const res = apply(env.app(), view, tx, ApplyFlags::None, env.journal);
     if (pass)
     {
         return isTesSuccess(res.ter);

src/test/jtx/impl/directory.cpp

@@ -32,7 +32,7 @@ bumpLastPage(
 {
     std::expected<void, Error> res{};
     env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) -> bool {
-        Sandbox sb(&view, TapNone);
+        Sandbox sb(&view, ApplyFlags::None);
 
         // Find the root page
         auto sleRoot = sb.peek(directory);

src/test/ledger/Directory_test.cpp

@@ -313,7 +313,7 @@ struct Directory_test : public beast::unit_test::Suite
         // All the offers have been cancelled, so the book
         // should have no entries and be empty:
         {
-            Sandbox const sb(env.closed().get(), TapNone);
+            Sandbox const sb(env.closed().get(), ApplyFlags::None);
             UInt256 const bookBase = getBookBase({xrpIssue(), usd, std::nullopt});
 
             BEAST_EXPECT(dirIsEmpty(sb, keylet::page(bookBase)));
@@ -352,7 +352,7 @@ struct Directory_test : public beast::unit_test::Suite
 
         {
             // Create a chain of three pages:
-            Sandbox sb(env.closed().get(), TapNone);
+            Sandbox sb(env.closed().get(), ApplyFlags::None);
             makePages(sb, kBase, 3);
 
             // Insert an item in the middle page:
@@ -376,7 +376,7 @@ struct Directory_test : public beast::unit_test::Suite
 
         {
             // Create a chain of four pages:
-            Sandbox sb(env.closed().get(), TapNone);
+            Sandbox sb(env.closed().get(), ApplyFlags::None);
             makePages(sb, kBase, 4);
 
             // Now add items on pages 1 and 2:

src/test/ledger/PaymentSandbox_test.cpp

@@ -131,7 +131,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
         STAmount const toDebit(usdGw1(20));
         {
             // accountSend, no deferredCredits
-            ApplyViewImpl av(&*env.current(), TapNone);
+            ApplyViewImpl av(&*env.current(), ApplyFlags::None);
 
             auto const iss = usdGw1;
             auto const startingAmount =
@@ -156,7 +156,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
 
         {
             // directSendNoFee, no deferredCredits
-            ApplyViewImpl av(&*env.current(), TapNone);
+            ApplyViewImpl av(&*env.current(), ApplyFlags::None);
 
             auto const iss = usdGw1;
             auto const startingAmount =
@@ -177,7 +177,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
 
         {
             // accountSend, w/ deferredCredits
-            ApplyViewImpl av(&*env.current(), TapNone);
+            ApplyViewImpl av(&*env.current(), ApplyFlags::None);
             PaymentSandbox pv(&av);
 
             auto const iss = usdGw1;
@@ -205,7 +205,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
 
         {
             // directSendNoFee, w/ deferredCredits
-            ApplyViewImpl av(&*env.current(), TapNone);
+            ApplyViewImpl av(&*env.current(), ApplyFlags::None);
             PaymentSandbox pv(&av);
 
             auto const iss = usdGw1;
@@ -221,7 +221,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
 
         {
             // redeemIOU, w/ deferredCredits
-            ApplyViewImpl av(&*env.current(), TapNone);
+            ApplyViewImpl av(&*env.current(), ApplyFlags::None);
             PaymentSandbox pv(&av);
 
             auto const iss = usdGw1;
@@ -237,7 +237,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
 
         {
             // issueIOU, w/ deferredCredits
-            ApplyViewImpl av(&*env.current(), TapNone);
+            ApplyViewImpl av(&*env.current(), ApplyFlags::None);
             PaymentSandbox pv(&av);
 
             auto const iss = usdGw1;
@@ -253,7 +253,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
 
         {
             // accountSend, w/ deferredCredits and stacked views
-            ApplyViewImpl av(&*env.current(), TapNone);
+            ApplyViewImpl av(&*env.current(), ApplyFlags::None);
             PaymentSandbox pv(&av);
 
             auto const iss = usdGw1;
@@ -319,7 +319,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
         STAmount const hugeAmt(
             issue, STAmount::kMaxValue, STAmount::kMaxOffset - 1, false, STAmount::Unchecked{});
 
-        ApplyViewImpl av(&*env.current(), TapNone);
+        ApplyViewImpl av(&*env.current(), ApplyFlags::None);
         PaymentSandbox pv(&av);
         pv.creditHookIOU(gw, alice, hugeAmt, -tinyAmt);
         BEAST_EXPECT(pv.balanceHookIOU(alice, gw, hugeAmt) == tinyAmt);
@@ -347,7 +347,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
         env.fund(reserve(env, 1), alice);
 
         env.close();
-        ApplyViewImpl av(&*env.current(), TapNone);
+        ApplyViewImpl av(&*env.current(), ApplyFlags::None);
         PaymentSandbox sb(&av);
         {
             // Send alice an amount and spend it. The deferredCredits will cause
@@ -380,7 +380,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
         auto const usd = gw["USD"];
         Account const alice("alice");
 
-        ApplyViewImpl av(&*env.current(), TapNone);
+        ApplyViewImpl av(&*env.current(), ApplyFlags::None);
         PaymentSandbox sb(&av);
 
         // The currency we pass for the last argument mimics the currency that
@@ -412,7 +412,7 @@ class PaymentSandbox_test : public beast::unit_test::Suite
         env.fund(XRP(10000), alice, sponsor);
         env.close();
 
-        ApplyViewImpl av(&*env.current(), TapNone);
+        ApplyViewImpl av(&*env.current(), ApplyFlags::None);
         PaymentSandbox sb(&av);
 
         // Test basic owner count hook without sponsor

src/test/ledger/View_test.cpp

@@ -189,7 +189,7 @@ class View_test : public beast::unit_test::Suite
         Env env(*this);
         wipe(env.app().getOpenLedger());
         auto const open = env.current();
-        ApplyViewImpl v(&*open, TapNone);
+        ApplyViewImpl v(&*open, ApplyFlags::None);
         succ(v, 0, std::nullopt);
         v.insert(sle(1));
         BEAST_EXPECT(v.exists(k(1)));
@@ -222,7 +222,7 @@ class View_test : public beast::unit_test::Suite
         Env env(*this);
         wipe(env.app().getOpenLedger());
         auto const open = env.current();
-        ApplyViewImpl v0(&*open, TapNone);
+        ApplyViewImpl v0(&*open, ApplyFlags::None);
         v0.insert(sle(1));
         v0.insert(sle(2));
         v0.insert(sle(4));
@@ -288,7 +288,7 @@ class View_test : public beast::unit_test::Suite
         Env env(*this);
         wipe(env.app().getOpenLedger());
         auto const open = env.current();
-        ApplyViewImpl v0(&*open, TapNone);
+        ApplyViewImpl v0(&*open, ApplyFlags::None);
         v0.rawInsert(sle(1, 1));
         v0.rawInsert(sle(2, 2));
         v0.rawInsert(sle(4, 4));
@@ -368,22 +368,22 @@ class View_test : public beast::unit_test::Suite
                 BEAST_EXPECT(v1.seq() == v0.seq());
                 BEAST_EXPECT(v1.parentCloseTime() == v1.parentCloseTime());
 
-                ApplyViewImpl v2(&v1, TapRetry);
+                ApplyViewImpl v2(&v1, ApplyFlags::Retry);
                 BEAST_EXPECT(v2.parentCloseTime() == v1.parentCloseTime());
                 BEAST_EXPECT(v2.seq() == v1.seq());
-                BEAST_EXPECT(v2.flags() == TapRetry);
+                BEAST_EXPECT(v2.flags() == ApplyFlags::Retry);
 
                 Sandbox const v3(&v2);
                 BEAST_EXPECT(v3.seq() == v2.seq());
                 BEAST_EXPECT(v3.parentCloseTime() == v2.parentCloseTime());
-                BEAST_EXPECT(v3.flags() == TapRetry);
+                BEAST_EXPECT(v3.flags() == ApplyFlags::Retry);
             }
             {
-                ApplyViewImpl v1(&v0, TapRetry);
+                ApplyViewImpl v1(&v0, ApplyFlags::Retry);
                 PaymentSandbox v2(&v1);
                 BEAST_EXPECT(v2.seq() == v0.seq());
                 BEAST_EXPECT(v2.parentCloseTime() == v0.parentCloseTime());
-                BEAST_EXPECT(v2.flags() == TapRetry);
+                BEAST_EXPECT(v2.flags() == ApplyFlags::Retry);
                 PaymentSandbox const v3(&v2);
                 BEAST_EXPECT(v3.seq() == v2.seq());
                 BEAST_EXPECT(v3.parentCloseTime() == v2.parentCloseTime());
@@ -1028,7 +1028,7 @@ class View_test : public beast::unit_test::Suite
             wipe(*ledger);
             ledger->rawInsert(sle(1));
             ReadView const& v0 = *ledger;
-            ApplyViewImpl v1(&v0, TapNone);
+            ApplyViewImpl v1(&v0, ApplyFlags::None);
             {
                 Sandbox v2(&v1);
                 v2.erase(v2.peek(k(1)));

src/test/rpc/GetCounts_test.cpp

@@ -9,6 +9,7 @@
 #include <xrpl/json/json_value.h>
 #include <xrpl/protocol/jss.h>
 
+#include <algorithm>
 #include <thread>
 
 namespace xrpl {
@@ -52,36 +53,59 @@ class GetCounts_test : public beast::unit_test::Suite
             // check counts, default params
             result = env.rpc("get_counts")[jss::result];
             BEAST_EXPECT(result[jss::status] == "success");
-            // compare with values reported by CountedObjects
-            auto const& objectCounts = CountedObjects::getInstance().getCounts(10);
-            for (auto const& it : objectCounts)
+
+            // compare with values reported by the registry
+            auto const& counters = result[jss::counters];
+
+            for (auto const& c : gCountedObjects)
             {
-                BEAST_EXPECTS(result.isMember(it.first), it.first);
-                BEAST_EXPECTS(result[it.first].asInt() == it.second, it.first);
+                if (auto const count = c.count(); count >= 10)
+                {
+                    BEAST_EXPECTS(counters.isMember(c.name()), c.name());
+                    BEAST_EXPECTS(counters[c.name()][jss::current].asUInt() == count, c.name());
+                }
             }
+
             BEAST_EXPECT(!result.isMember(jss::local_txs));
         }
-
         {
             // make request with min threshold 100 and verify
-            // that only STObject and NodeObject are reported
+            // that only counters at or above the threshold are reported
             result = env.rpc("get_counts", "100")[jss::result];
             BEAST_EXPECT(result[jss::status] == "success");
 
-            // compare with values reported by CountedObjects
-            auto const& objectCounts = CountedObjects::getInstance().getCounts(100);
-            for (auto const& it : objectCounts)
-            {
-                BEAST_EXPECTS(result.isMember(it.first), it.first);
-                BEAST_EXPECTS(result[it.first].asInt() == it.second, it.first);
-            }
-            BEAST_EXPECT(!result.isMember("Transaction"));
-            BEAST_EXPECT(!result.isMember("STTx"));
-            BEAST_EXPECT(!result.isMember("STArray"));
-            BEAST_EXPECT(!result.isMember("HashRouterEntry"));
-            BEAST_EXPECT(!result.isMember("STLedgerEntry"));
-        }
+            auto const& counters = result[jss::counters];
 
+            // every registry counter at/above threshold must be reported, with
+            // a matching current value
+            for (auto const& c : gCountedObjects)
+            {
+                if (auto const count = c.count(); count >= 100)
+                {
+                    BEAST_EXPECTS(counters.isMember(c.name()), c.name());
+                    BEAST_EXPECTS(counters[c.name()][jss::current].asUInt() == count, c.name());
+                }
+            }
+
+            // conversely, every reported entry must be a known counter that met
+            // the threshold, and its maximum must be consistent
+            for (auto const& name : counters.getMemberNames())
+            {
+                auto const it = std::ranges::find_if(
+                    gCountedObjects, [&](auto const& c) { return c.name() == name; });
+                BEAST_EXPECTS(it != gCountedObjects.end(), name);
+
+                auto const& entry = counters[name];
+                BEAST_EXPECTS(entry[jss::current].asUInt() >= 100, name);
+                BEAST_EXPECTS(entry[jss::maximum].asUInt() >= entry[jss::current].asUInt(), name);
+            }
+
+            BEAST_EXPECT(!counters.isMember("xrpl::Transaction"));
+            BEAST_EXPECT(!counters.isMember("xrpl::STTx"));
+            BEAST_EXPECT(!counters.isMember("xrpl::STArray"));
+            BEAST_EXPECT(!counters.isMember("xrpl::HashRouterEntry"));
+            BEAST_EXPECT(!counters.isMember("xrpl::STLedgerEntry"));
+        }
         {
             // local_txs field will exist when there are open Txs
             env(pay(alice, bob, alice["USD"](5)));

src/tests/libxrpl/helpers/TxTest.cpp

@@ -107,7 +107,8 @@ TxTest::getRules() const
 [[nodiscard]] TxResult
 TxTest::submit(std::shared_ptr<STTx const> stx)
 {
-    auto result = apply(registry_, *openLedger_, *stx, TapNone, registry_.getJournal("apply"));
+    auto result =
+        apply(registry_, *openLedger_, *stx, ApplyFlags::None, registry_.getJournal("apply"));
 
     // Track successfully applied transactions for canonical reordering on close
     // We make a copy since the TransactionBase doesn't own the STTx
@@ -198,7 +199,8 @@ TxTest::close()
         OpenView accum(&*newLedger);
         for (auto const& [key, tx] : txSet)
         {
-            auto result = apply(registry_, accum, *tx, TapNone, registry_.getJournal("apply"));
+            auto result =
+                apply(registry_, accum, *tx, ApplyFlags::None, registry_.getJournal("apply"));
             if (!result.applied)
             {
                 throw std::runtime_error("TxTest::close: failed to apply transaction");

src/tests/libxrpl/ledger/EntryTestHelpers.h

@@ -32,7 +32,7 @@ public:
     Account const bob{"bob"};
     Account const carol{"carol"};
 
-    EntryTestEnv() : av_(&fundAndClose(), TapNone)
+    EntryTestEnv() : av_(&fundAndClose(), ApplyFlags::None)
     {
     }
 

src/tests/libxrpl/ledger/SLEBase.cpp

@@ -204,7 +204,7 @@ TEST_F(SLEBaseTests, adopt_sle)
 
 TEST_F(SLEBaseTests, writable_accessors)
 {
-    ApplyViewImpl av(&env_.getClosedLedger(), TapNone);
+    ApplyViewImpl av(&env_.getClosedLedger(), ApplyFlags::None);
     beast::Journal const j{beast::Journal::getNullSink()};
 
     AccountRootEntryW account(alice_.id(), av, j);
@@ -239,7 +239,7 @@ TEST_F(SLEBaseTests, writable_accessors)
 
 TEST_F(SLEBaseTests, apply_view_context_ctor)
 {
-    ApplyViewImpl av(&env_.getClosedLedger(), TapNone);
+    ApplyViewImpl av(&env_.getClosedLedger(), ApplyFlags::None);
     beast::Journal const j{beast::Journal::getNullSink()};
 
     transactions::AccountSetBuilder builder{alice_.id()};
@@ -264,7 +264,7 @@ TEST_F(SLEBaseTests, apply_view_context_ctor)
 TEST_F(SLEBaseTests, writable_lifecycle)
 {
     // A view we never apply, so nothing here reaches the ledger.
-    ApplyViewImpl av(&env_.getClosedLedger(), TapNone);
+    ApplyViewImpl av(&env_.getClosedLedger(), ApplyFlags::None);
 
     // Entry that does not exist yet: newSLE() -> insert().
     {
@@ -289,7 +289,7 @@ TEST_F(SLEBaseTests, writable_lifecycle)
     // Erase but not Cache, so it shows the difference: building the entry
     // only peeks, and the write is invisible to the view until update().
     {
-        ApplyViewImpl fresh(&env_.getClosedLedger(), TapNone);
+        ApplyViewImpl fresh(&env_.getClosedLedger(), ApplyFlags::None);
 
         AccountRootEntryW account(alice_.id(), fresh);
         EXPECT_TRUE(account.exists());
@@ -321,7 +321,7 @@ TEST_F(SLEBaseTests, writable_lifecycle)
 
 TEST_F(SLEBaseTests, conversion)
 {
-    ApplyViewImpl av(&env_.getClosedLedger(), TapNone);
+    ApplyViewImpl av(&env_.getClosedLedger(), ApplyFlags::None);
 
     AccountRootEntryW const writable(alice_.id(), av);
     EXPECT_TRUE(writable.exists());
@@ -346,7 +346,7 @@ TEST_F(SLEBaseTests, resolve_entry_peeks)
     AccountRootEntryR const overLedger(alice_.id(), ledger);
     EXPECT_TRUE(overLedger.exists());
 
-    ApplyViewImpl av(&ledger, TapNone);
+    ApplyViewImpl av(&ledger, ApplyFlags::None);
 
     // ReadView const& binds an ApplyViewImpl just as happily, and there the
     // dynamic_cast succeeds, so this one resolves through ApplyView::peek().
@@ -393,7 +393,7 @@ TEST_F(SLEBaseTests, throws_on_missing_entry)
 TEST_F(SLEBaseTests, throws_on_missing_writable_entry)
 {
     // A view we never apply, so nothing here reaches the ledger.
-    ApplyViewImpl av(&env_.getClosedLedger(), TapNone);
+    ApplyViewImpl av(&env_.getClosedLedger(), ApplyFlags::None);
 
     // bob is unfunded, so this resolves to nothing and every operation that
     // needs an SLE has to throw instead of dereferencing null. These are the

src/xrpld/app/consensus/RCLConsensus.cpp

@@ -655,7 +655,7 @@ RCLConsensus::Adaptor::doAccept(
             localTxs_.getTxSet(),
             anyDisputes,
             retriableTxs,
-            TapNone,
+            ApplyFlags::None,
             "consensus",
             [&](OpenView& view, beast::Journal j) {
                 // Stuff the ledger with transactions from the queue.
@@ -760,7 +760,7 @@ RCLConsensus::Adaptor::buildLCL(
             XRPL_ASSERT(
                 replayData->parent()->header().hash == previousLedger.id(),
                 "xrpl::RCLConsensus::Adaptor::buildLCL : parent hash match");
-            return buildLedger(*replayData, TapNone, app_, j_);
+            return buildLedger(*replayData, ApplyFlags::None, app_, j_);
         }
         return buildLedger(
             previousLedger.ledger,

src/xrpld/app/ledger/detail/BuildLedger.cpp

@@ -126,7 +126,7 @@ applyTransactions(
                     continue;
                 }
 
-                switch (applyTransaction(app, view, *it->second, certainRetry, TapNone, j))
+                switch (applyTransaction(app, view, *it->second, certainRetry, ApplyFlags::None, j))
                 {
                     case ApplyTransactionResult::Success:
                         it = txns.erase(it);

src/xrpld/app/ledger/detail/LedgerDeltaAcquire.cpp

@@ -205,7 +205,7 @@ LedgerDeltaAcquire::tryBuild(std::shared_ptr<Ledger const> const& parent)
         "xrpl::LedgerDeltaAcquire::tryBuild : parent hash match");
     // build ledger
     LedgerReplay const replayData(parent, replayTemp_, std::move(orderedTxns_));
-    fullLedger_ = buildLedger(replayData, TapNone, app_, journal_);
+    fullLedger_ = buildLedger(replayData, ApplyFlags::None, app_, journal_);
     if (fullLedger_ && fullLedger_->header().hash == hash_)
     {
         JLOG(journal_.info()) << "Built " << hash_;

src/xrpld/app/ledger/detail/OpenLedger.cpp

@@ -178,7 +178,7 @@ OpenLedger::applyOne(
     beast::Journal j) -> Result
 {
     if (retry)
-        flags = flags | TapRetry;
+        flags = flags | ApplyFlags::Retry;
     // If it's in anybody's proposed set, try to keep it in the ledger
     auto const result = xrpl::apply(app, view, *tx, flags, j);
     if (result.applied || result.ter == terQUEUED)

src/xrpld/app/main/Application.cpp

@@ -473,8 +473,6 @@ public:
               getIoContext())
         , grpcServer_(std::make_unique<GRPCServer>(*this))
     {
-        initAccountIdCache(config_->getValueFor(SizedItem::AccountIdCacheSize));
-
         add(resourceManager_.get());
 
         //

src/xrpld/app/misc/FeeVoteImpl.cpp

@@ -226,27 +226,22 @@ FeeVoteImpl::doVoting(
         auto doVote = [](std::shared_ptr<STValidation> const& val,
                          detail::VotableValue& value,
                          auto const& valueField) {
-            if (auto const field = val->at(~valueField))
+            using XRPType = XRPAmount::value_type;
+
+            if (auto const field = val->at(~valueField); field && std::in_range<XRPType>(*field))
             {
-                using XRPType = XRPAmount::value_type;
-                auto const vote = *field;
-                if (vote <= std::numeric_limits<XRPType>::max() &&
-                    isLegalAmountSigned(XRPAmount{unsafeCast<XRPType>(vote)}))
+                if (auto const amount = XRPAmount{checkedCast<XRPType>(*field)};
+                    isLegalAmountSigned(amount))
                 {
-                    value.addVote(XRPAmount{unsafeCast<XRPType>(vote)});
-                }
-                else
-                {
-                    // Invalid amounts will be treated as if they're
-                    // not provided. Don't throw because this value is
-                    // provided by an external entity.
-                    value.noVote();
+                    value.addVote(amount);
+                    return;
                 }
             }
-            else
-            {
-                value.noVote();
-            }
+
+            // Invalid or missing amounts are treated as if they're not
+            // provided. Don't throw because this value is provided by an
+            // external entity.
+            value.noVote();
         };
 
         for (auto const& val : set)

src/xrpld/app/misc/NetworkOPs.cpp

@@ -1706,12 +1706,12 @@ NetworkOPsImp::apply(std::unique_lock<std::mutex>& batchLock)
                 for (TransactionStatus& e : transactions)
                 {
                     // we check before adding to the batch
-                    ApplyFlags flags = TapNone;
+                    ApplyFlags flags = ApplyFlags::None;
                     if (e.admin)
-                        flags |= TapUnlimited;
+                        flags |= ApplyFlags::Unlimited;
 
                     if (e.failType == FailHard::Yes)
-                        flags |= TapFailHard;
+                        flags |= ApplyFlags::FailHard;
 
                     auto const result = registry_.get().getTxQ().apply(
                         registry_.get().getApp(), view, e.transaction->getSTransaction(), flags, j);
@@ -2207,7 +2207,7 @@ NetworkOPsImp::switchLastClosedLedger(std::shared_ptr<Ledger const> const& newLC
             OrderedTxs({}),
             false,
             retries,
-            TapNone,
+            ApplyFlags::None,
             "jump",
             [&](OpenView& view, beast::Journal j) {
                 // Stuff the ledger with transactions from the queue.

src/xrpld/app/misc/detail/TxQ.cpp

@@ -333,8 +333,9 @@ TxQ::MaybeTx::apply(Application& app, OpenView& view, beast::Journal j)
     if (pfResult->rules != view.rules() || pfResult->flags != flags)
     {
         JLOG(j.debug()) << "Queued transaction " << txID
-                        << " rules or flags have changed. Flags from " << pfResult->flags << " to "
-                        << flags;
+                        << " rules or flags have changed. Flags from "
+                        << std::to_underlying(pfResult->flags) << " to "
+                        << std::to_underlying(flags);
 
         pfResult.emplace(preflight(app, view.rules(), pfResult->tx, flags, pfResult->j));
     }
@@ -425,7 +426,7 @@ TxQ::canBeHeld(
     // queue yet, but should be added in the future.
     // TapFailHard transactions are never held
     if (tx.isFieldPresent(sfPreviousTxnID) || tx.isFieldPresent(sfAccountTxnID) ||
-        ((flags & TapFailHard) != 0u))
+        ((flags & ApplyFlags::FailHard) != ApplyFlags::None))
         return telCAN_NOT_QUEUE;
 
     // Disallow delegated transactions from being queued.
@@ -777,7 +778,7 @@ TxQ::apply(
     if (auto directApplied = tryDirectApply(app, view, tx, flags, j))
         return *directApplied;
 
-    if ((flags & TapDryRun) != 0u)
+    if ((flags & ApplyFlags::DryRun) != ApplyFlags::None)
         return {telCAN_NOT_QUEUE, false};
 
     // If we get past tryDirectApply() without returning then we expect
@@ -1345,7 +1346,7 @@ TxQ::apply(
     // will not be checked again, so the cost should be minimal.
 
     // Don't allow soft failures, which can lead to retries
-    flags &= ~TapRetry;
+    flags &= ~ApplyFlags::Retry;
 
     auto& candidate = accountIter->second.add({tx, transactionID, feeLevelPaid, flags, pfResult});
 
@@ -1354,8 +1355,7 @@ TxQ::apply(
     JLOG(j_.debug()) << "Added transaction " << candidate.txID << " with result "
                      << transToken(pfResult.ter) << " from "
                      << (accountIsInQueue ? "existing" : "new") << " account " << candidate.account
-                     << " to queue."
-                     << " Flags: " << flags;
+                     << " to queue. Flags: " << std::to_underlying(flags);
 
     return {terQUEUED, false};
 }
@@ -1473,7 +1473,8 @@ TxQ::accept(Application& app, OpenView& view)
             candidateIter++;
             continue;
         }
-        auto const requiredFeeLevel = getRequiredFeeLevel(view, TapNone, metricsSnapshot, lock);
+        auto const requiredFeeLevel =
+            getRequiredFeeLevel(view, ApplyFlags::None, metricsSnapshot, lock);
         auto const feeLevelPaid = candidateIter->feeLevel;
         JLOG(j_.trace()) << "Queued transaction " << candidateIter->txID << " from account "
                          << candidateIter->account << " has fee level of " << feeLevelPaid
@@ -1515,7 +1516,8 @@ TxQ::accept(Application& app, OpenView& view)
             {
                 JLOG(j_.debug()) << "Queued transaction " << candidateIter->txID << " failed with "
                                  << transToken(txnResult) << ". Leave in queue."
-                                 << " Applied: " << didApply << ". Flags: " << candidateIter->flags;
+                                 << " Applied: " << didApply
+                                 << ". Flags: " << std::to_underlying(candidateIter->flags);
                 if (account.retryPenalty && candidateIter->retriesRemaining > 2)
                 {
                     candidateIter->retriesRemaining = 1;

src/xrpld/core/Config.h

@@ -41,7 +41,6 @@ enum class SizedItem : std::size_t {
     OpenFinalLimit,
     BurstSize,
     RamSizeGb,
-    AccountIdCacheSize,
 };
 
 /**

src/xrpld/core/detail/Config.cpp

@@ -111,7 +111,7 @@ namespace xrpl {
 
 // clang-format off
 // The configurable node sizes are "tiny", "small", "medium", "large", "huge"
-inline constexpr std::array<std::pair<SizedItem, std::array<int, 5>>, 13>
+inline constexpr std::array<std::pair<SizedItem, std::array<int, 5>>, 12>
 kSizedItems
 {{
     // FIXME: We should document each of these items, explaining exactly
@@ -130,8 +130,7 @@ kSizedItems
     {SizedItem::LgrDbCache,         {{      4,       8,      16,      32,     128 }}},
     {SizedItem::OpenFinalLimit,     {{      8,      16,      32,      64,     128 }}},
     {SizedItem::BurstSize,          {{      4,       8,      16,      32,      48 }}},
-    {SizedItem::RamSizeGb,          {{      6,       8,      12,      24,       0 }}},
-    {SizedItem::AccountIdCacheSize, {{  20047,   50053,   77081,  150061,  300007 }}}
+    {SizedItem::RamSizeGb,          {{      6,       8,      12,      24,       0 }}}
 }};
 // clang-format on
 

src/xrpld/rpc/detail/PathRequest.cpp

@@ -633,7 +633,7 @@ PathRequest::findPaths(
         path::RippleCalc::Input rcInput;
         if (convertAll_)
             rcInput.partialPaymentAllowed = true;
-        auto sandbox = std::make_unique<PaymentSandbox>(&*cache->getLedger(), TapNone);
+        auto sandbox = std::make_unique<PaymentSandbox>(&*cache->getLedger(), ApplyFlags::None);
         auto rc = path::RippleCalc::rippleCalculate(
             *sandbox,
             saMaxAmount,  // --> Amount to send is unlimited
@@ -654,7 +654,7 @@ PathRequest::findPaths(
             JLOG(journal_.debug()) << iIdentifier_ << " Trying with an extra path element";
 
             ps.pushBack(fullLiquidityPath);
-            sandbox = std::make_unique<PaymentSandbox>(&*cache->getLedger(), TapNone);
+            sandbox = std::make_unique<PaymentSandbox>(&*cache->getLedger(), ApplyFlags::None);
             rc = path::RippleCalc::rippleCalculate(
                 *sandbox,
                 saMaxAmount,  // --> Amount to send is unlimited

src/xrpld/rpc/detail/Pathfinder.cpp

@@ -392,7 +392,7 @@ Pathfinder::getPathLiquidity(
     path::RippleCalc::Input rcInput;
     rcInput.defaultPathsAllowed = false;
 
-    PaymentSandbox sandbox(&*ledger_, TapNone);
+    PaymentSandbox sandbox(&*ledger_, ApplyFlags::None);
 
     try
     {
@@ -455,7 +455,7 @@ Pathfinder::computePathRanks(int maxPaths, std::function<bool(void)> const& cont
     // Must subtract liquidity in default path from remaining amount.
     try
     {
-        PaymentSandbox sandbox(&*ledger_, TapNone);
+        PaymentSandbox sandbox(&*ledger_, ApplyFlags::None);
 
         path::RippleCalc::Input rcInput;
         rcInput.partialPaymentAllowed = true;
@@ -948,7 +948,7 @@ Pathfinder::isNoRippleOut(STPath const& currentPath)
 
     // Last link must be an account.
     STPathElement const& endElement = currentPath.back();
-    if ((endElement.getNodeType() & STPathElement::TypeAccount) == 0u)
+    if (!endElement.isType(STPathElement::TypeAccount))
         return false;
 
     // If there's only one item in the path, return true if that item specifies

src/xrpld/rpc/handlers/admin/status/GetCounts.cpp

@@ -4,6 +4,7 @@
 #include <xrpld/app/rdb/backend/SQLiteDatabase.h>
 #include <xrpld/rpc/Context.h>
 
+#include <xrpl/basics/CountedObject.h>
 #include <xrpl/basics/UptimeClock.h>
 #include <xrpl/json/json_forwards.h>
 #include <xrpl/json/json_value.h>
@@ -11,9 +12,11 @@
 #include <xrpl/protocol/jss.h>
 #include <xrpl/server/NetworkOPs.h>
 
+#include <algorithm>
 #include <chrono>
 #include <cstddef>
 #include <string>
+#include <utility>
 
 namespace xrpl {
 
@@ -43,16 +46,26 @@ textTime(
 }
 
 json::Value
-getCountsJson(Application& app, int minObjectCount)
+getCountsJson(Application& app, std::uint32_t minObjectCount)
 {
-    auto objectCounts = CountedObjects::getInstance().getCounts(minObjectCount);
+    json::Value ret = json::ValueType::Object;
 
-    json::Value ret(json::ValueType::Object);
+    ret[jss::counters] = [minObjectCount] {
+        json::Value ctrs = json::ValueType::Object;
 
-    for (auto const& [k, v] : objectCounts)
-    {
-        ret[k] = v;
-    }
+        for (auto const& c : gCountedObjects)
+        {
+            if (auto const count = c.count(); count >= minObjectCount)
+            {
+                json::Value obj(json::ValueType::Object);
+                obj[jss::current] = count;
+                obj[jss::maximum] = std::max(count, c.max());
+                ctrs[c.name()] = std::move(obj);
+            }
+        }
+
+        return ctrs;
+    }();
 
     if (app.config().useTxTables())
     {
@@ -113,7 +126,7 @@ getCountsJson(Application& app, int minObjectCount)
 json::Value
 doGetCounts(rpc::JsonContext& context)
 {
-    int minCount = 10;
+    std::uint32_t minCount = 10;
 
     if (context.params.isMember(jss::min_count))
         minCount = context.params[jss::min_count].asUInt();

src/xrpld/rpc/handlers/admin/status/GetCounts.h

@@ -4,9 +4,11 @@
 
 #include <xrpl/json/json_value.h>
 
+#include <cstdint>
+
 namespace xrpl {
 
 json::Value
-getCountsJson(Application& app, int minObjectCount);
+getCountsJson(Application& app, std::uint32_t minObjectCount);
 
 }  // namespace xrpl

src/xrpld/rpc/handlers/transaction/Simulate.cpp

@@ -247,7 +247,7 @@ simulateTxn(rpc::JsonContext& context, std::shared_ptr<Transaction> transaction)
     // Process the transaction
     OpenView view = *context.app.getOpenLedger().current();
     auto const result = context.app.getTxQ().apply(
-        context.app, view, transaction->getSTransaction(), TapDryRun, context.j);
+        context.app, view, transaction->getSTransaction(), ApplyFlags::DryRun, context.j);
 
     jvResult[jss::applied] = result.applied;
     jvResult[jss::ledger_index] = view.seq();