Add CachedLedger:

This type alias provide cache-wrapping for Ledger objects.
Through the CachedLedger interface, access to the underlying
Ledger is permitted to allow for cases where the implementation
must perform Ledger specific activities. For example, building
a fetch pack from the contained SHAMap objects.

The CachingReadView is refactored:

* Renamed to CachedView
* Templated on Base, the base type
* base() returns a shared_ptr to the wrapped object
* Constructor requires a shared_ptr<Base>

Builds/VisualStudio2013/RippleD.vcxproj

@@ -2303,7 +2303,7 @@
     </ClInclude>
     <ClInclude Include="..\..\src\ripple\ledger\CachedSLEs.h">
     </ClInclude>
-    <ClInclude Include="..\..\src\ripple\ledger\CachingReadView.h">
+    <ClInclude Include="..\..\src\ripple\ledger\CachedView.h">
     </ClInclude>
     <ClInclude Include="..\..\src\ripple\ledger\detail\ApplyStateTable.h">
     </ClInclude>
@@ -2333,7 +2333,7 @@
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='debug|x64'">True</ExcludedFromBuild>
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='release|x64'">True</ExcludedFromBuild>
     </ClCompile>
-    <ClCompile Include="..\..\src\ripple\ledger\impl\CachingReadView.cpp">
+    <ClCompile Include="..\..\src\ripple\ledger\impl\CachedView.cpp">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='debug|x64'">True</ExcludedFromBuild>
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='release|x64'">True</ExcludedFromBuild>
     </ClCompile>

Builds/VisualStudio2013/RippleD.vcxproj.filters

@@ -3030,7 +3030,7 @@
     <ClInclude Include="..\..\src\ripple\ledger\CachedSLEs.h">
       <Filter>ripple\ledger</Filter>
     </ClInclude>
-    <ClInclude Include="..\..\src\ripple\ledger\CachingReadView.h">
+    <ClInclude Include="..\..\src\ripple\ledger\CachedView.h">
       <Filter>ripple\ledger</Filter>
     </ClInclude>
     <ClInclude Include="..\..\src\ripple\ledger\detail\ApplyStateTable.h">
@@ -3063,7 +3063,7 @@
     <ClCompile Include="..\..\src\ripple\ledger\impl\CachedSLEs.cpp">
       <Filter>ripple\ledger\impl</Filter>
     </ClCompile>
-    <ClCompile Include="..\..\src\ripple\ledger\impl\CachingReadView.cpp">
+    <ClCompile Include="..\..\src\ripple\ledger\impl\CachedView.cpp">
       <Filter>ripple\ledger\impl</Filter>
     </ClCompile>
     <ClCompile Include="..\..\src\ripple\ledger\impl\Directory.cpp">

src/ripple/app/ledger/Ledger.h

@@ -22,6 +22,7 @@
 
 #include <ripple/ledger/TxMeta.h>
 #include <ripple/ledger/View.h>
+#include <ripple/ledger/CachedView.h>
 #include <ripple/app/tx/Transaction.h>
 #include <ripple/basics/CountedObject.h>
 #include <ripple/protocol/Indexes.h>
@@ -412,6 +413,9 @@ private:
     std::uint32_t mutable mReserveIncrement = 0;
 };
 
+/** A ledger wrapped in a CachedView. */
+using CachedLedger = CachedView<Ledger>;
+
 //------------------------------------------------------------------------------
 //
 // API

src/ripple/app/ledger/OpenLedger.h

@@ -68,7 +68,7 @@ public:
         @param ledger A closed ledger
     */
     explicit
-    OpenLedger (std::shared_ptr<
+    OpenLedger(std::shared_ptr<
         Ledger const> const& ledger,
             Config const& config, CachedSLEs& cache,
                 beast::Journal journal);

src/ripple/app/ledger/impl/OpenLedger.cpp

@@ -20,13 +20,13 @@
 #include <BeastConfig.h>
 #include <ripple/app/ledger/OpenLedger.h>
 #include <ripple/app/tx/apply.h>
-#include <ripple/ledger/CachingReadView.h>
+#include <ripple/ledger/CachedView.h>
 #include <boost/range/adaptor/transformed.hpp>
 
 namespace ripple {
 
-OpenLedger::OpenLedger(
+OpenLedger::OpenLedger(std::shared_ptr<
-    std::shared_ptr<Ledger const> const& ledger,
+    Ledger const> const& ledger,
         Config const& config, CachedSLEs& cache,
             beast::Journal journal)
     : j_ (journal)
@@ -65,7 +65,7 @@ OpenLedger::modify (std::function<
 }
 
 void
-OpenLedger::accept (std::shared_ptr<
+OpenLedger::accept(std::shared_ptr<
     Ledger const> const& ledger,
         OrderedTxs const& locals, bool retriesFirst,
             OrderedTxs& retries, ApplyFlags flags,
@@ -113,12 +113,12 @@ OpenLedger::accept (std::shared_ptr<
 //------------------------------------------------------------------------------
 
 std::shared_ptr<OpenView>
-OpenLedger::create (std::shared_ptr<
+OpenLedger::create(std::shared_ptr<
     Ledger const> const& ledger)
 {
     return std::make_shared<OpenView>(
         open_ledger, std::make_shared<
-            CachingReadView const>(ledger,
+            CachedLedger const>(ledger,
                 cache_));
 }
 

src/ripple/ledger/CachedView.h

@@ -17,8 +17,8 @@
 */
 //==============================================================================
 
-#ifndef RIPPLE_LEDGER_CACHINGREADVIEW_H_INCLUDED
+#ifndef RIPPLE_LEDGER_CACHEDVIEW_H_INCLUDED
-#define RIPPLE_LEDGER_CACHINGREADVIEW_H_INCLUDED
+#define RIPPLE_LEDGER_CACHEDVIEW_H_INCLUDED
 
 #include <ripple/ledger/CachedSLEs.h>
 #include <ripple/ledger/ReadView.h>
@@ -26,41 +26,39 @@
 #include <map>
 #include <memory>
 #include <mutex>
+#include <type_traits>
 
 namespace ripple {
 
-//------------------------------------------------------------------------------
+namespace detail {
 
-/** ReadView that caches by key and hash. */
+class CachedViewImpl
-class CachingReadView
+    : public DigestAwareReadView
-    : public ReadView
 {
 private:
+    DigestAwareReadView const& base_;
     CachedSLEs& cache_;
     std::mutex mutable mutex_;
-    DigestAwareReadView const& base_;
-    std::shared_ptr<void const> hold_;
     std::unordered_map<key_type,
         std::shared_ptr<SLE const>,
             hardened_hash<>> mutable map_;
 
 public:
-    CachingReadView() = delete;
+    CachedViewImpl() = delete;
-    CachingReadView (CachingReadView const&) = delete;
+    CachedViewImpl (CachedViewImpl const&) = delete;
-    CachingReadView& operator= (CachingReadView const&) = delete;
+    CachedViewImpl& operator= (CachedViewImpl const&) = delete;
 
-    CachingReadView(
+    CachedViewImpl (DigestAwareReadView const* base,
-        DigestAwareReadView const* base,
-            CachedSLEs& cache,
-                std::shared_ptr<void const> hold);
-
-    CachingReadView (std::shared_ptr<
-        DigestAwareReadView const> const& base,
             CachedSLEs& cache)
-        : CachingReadView (&*base, cache, base)
+        : base_ (*base)
+        , cache_ (cache)
     {
     }
 
+    //
+    // ReadView
+    //
+
     bool
     exists (Keylet const& k) const override;
 
@@ -110,39 +108,58 @@ public:
         return base_.txRead(key);
     }
 
+    //
+    // DigestAwareReadView
+    //
+
+    boost::optional<digest_type>
+    digest (key_type const& key) const override
+    {
+        return base_.digest(key);
+    }
+
 };
 
-//------------------------------------------------------------------------------
+} // detail
 
-/** Wrap a DigestAwareReadView with a cache.
+/** Wraps a DigestAwareReadView to provide caching.
 
-    Effects:
+    @tparam Base A subclass of DigestAwareReadView
-
-        Returns ownership of a base ReadView that is
-        wrapped in a thread-safe cache.
-
-        The returned ReadView gains a reference to
-        the base.
-
-    Postconditions:
-
-        The base object will not be destroyed before
-        the returned view is destroyed.
-
-    The caller is responsible for ensuring that the
-    `cache` object lifetime extends to the lifetime of
-    the returned object.
 */
-inline
+template <class Base>
-std::shared_ptr<ReadView const>
+class CachedView
-makeCached (std::shared_ptr<
+    : public detail::CachedViewImpl
-    DigestAwareReadView const> const& base,
-        CachedSLEs& cache)
 {
-    return std::make_shared<
+private:
-        CachingReadView const>(
+    static_assert(std::is_base_of<
-            &*base, cache, base);
+        DigestAwareReadView, Base>::value, "");
-}
+
+    std::shared_ptr<Base const> sp_;
+
+public:
+    using base_type = Base;
+
+    CachedView() = delete;
+    CachedView (CachedView const&) = delete;
+    CachedView& operator= (CachedView const&) = delete;
+
+    CachedView (std::shared_ptr<
+        Base const> const& base, CachedSLEs& cache)
+        : CachedViewImpl (base.get(), cache)
+        , sp_ (base)
+    {
+    }
+
+    /** Returns the base type.
+
+        @note This breaks encapsulation and bypasses the cache.
+    */
+    std::shared_ptr<Base const> const&
+    base() const
+    {
+        return sp_;
+    }
+};
 
 } // ripple
 

src/ripple/ledger/impl/CachedView.cpp

@@ -18,30 +18,21 @@
 //==============================================================================
 
 #include <BeastConfig.h>
-#include <ripple/ledger/CachingReadView.h>
+#include <ripple/ledger/CachedView.h>
 #include <ripple/basics/contract.h>
 #include <ripple/protocol/Serializer.h>
 
 namespace ripple {
-
+namespace detail {
-CachingReadView::CachingReadView(
-    DigestAwareReadView const* base,
-        CachedSLEs& cache,
-            std::shared_ptr<void const> hold)
-    : cache_ (cache)
-    , base_ (*base)
-    , hold_ (hold)
-{
-}
 
 bool
-CachingReadView::exists (Keylet const& k) const
+CachedViewImpl::exists (Keylet const& k) const
 {
     return read(k) != nullptr;
 }
 
 std::shared_ptr<SLE const>
-CachingReadView::read (Keylet const& k) const
+CachedViewImpl::read (Keylet const& k) const
 {
     {
         std::lock_guard<
@@ -70,9 +61,10 @@ CachingReadView::read (Keylet const& k) const
         return sle;
     }
     if (! k.check(*iter->second))
-        LogicError("CachingReadView::read: wrong type");
+        LogicError("CachedView::read: wrong type");
     return iter->second;
 
 }
 
+} // detail
 } // ripple

src/ripple/unity/ledger.cpp

@@ -23,7 +23,7 @@
 #include <ripple/ledger/impl/ApplyViewBase.cpp>
 #include <ripple/ledger/impl/ApplyViewImpl.cpp>
 #include <ripple/ledger/impl/CachedSLEs.cpp>
-#include <ripple/ledger/impl/CachingReadView.cpp>
+#include <ripple/ledger/impl/CachedView.cpp>
 #include <ripple/ledger/impl/Directory.cpp>
 #include <ripple/ledger/impl/OpenView.cpp>
 #include <ripple/ledger/impl/PaymentSandbox.cpp>