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88794a1ea9
Bulk documentation pass covering 702 C++ source files in src/libxrpl, src/xrpld, and include/xrpl. Adds class, function, parameter, and invariant docs per docs/DOCUMENTATION_STANDARDS.md. Squashed from the original three-part series (part 1 / part 2 / part 3) to avoid merge-conflict noise when rebasing the work onto current develop.
324 lines
9.3 KiB
C++
324 lines
9.3 KiB
C++
/** @file
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* Defines `STBitString<Bits>`, the serialization-layer representation of
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* fixed-width opaque bit arrays, and the four concrete aliases used
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* throughout the protocol: `STUInt128`, `STUInt160`, `STUInt192`, and
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* `STUInt256`.
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*/
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#pragma once
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#include <xrpl/basics/CountedObject.h>
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#include <xrpl/beast/utility/Zero.h>
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#include <xrpl/protocol/STBase.h>
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namespace xrpl {
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/** Serialized fixed-width bit string field in the XRPL protocol type system.
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*
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* Bridges `BaseUInt<Bits>` — used for transaction hashes, account IDs,
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* ledger indices, and similar opaque identifiers — and the `STBase`
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* serialization framework. Despite the underlying type supporting
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* arithmetic, this class treats its value as an opaque sequence of bits:
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* only identity comparison, serialization, and value access are exposed.
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*
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* Each concrete instantiation (128, 160, 192, 256 bits) returns a
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* distinct wire-type code from `getSType()` (`STI_UINT128` through
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* `STI_UINT256`), so field metadata and codec behavior are type-correct at
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* the protocol level.
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*
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* `CountedObject<STBitString<Bits>>` maintains a per-width live instance
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* counter for diagnostic reporting; it carries no functional overhead.
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*
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* @tparam Bits Number of bits in the value. Declared `int` rather than
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* `unsigned int` to work around a GDB 12.1 bug that prevents locating
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* RTTI for templates instantiated over unsigned types; a `static_assert`
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* enforces that the value is positive.
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*/
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template <int Bits>
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class STBitString final : public STBase, public CountedObject<STBitString<Bits>>
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{
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static_assert(Bits > 0, "Number of bits must be positive");
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public:
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/** The underlying tag-free bit-string type (`BaseUInt<Bits>`). */
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using value_type = BaseUInt<Bits>;
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private:
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value_type value_{};
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public:
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STBitString() = default;
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/** Construct a named field with a zero-initialized value.
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*
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* Used when building objects programmatically before the value is known.
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*
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* @param n The `SField` that identifies this field on the wire.
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*/
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STBitString(SField const& n);
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/** Construct an anonymous value, discarding field identity.
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*
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* Intended for temporary computations where only the raw value matters.
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*
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* @param v The initial bit-string value.
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*/
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STBitString(value_type const& v);
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/** Construct a fully specified named field with a given value.
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*
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* @param n The `SField` that identifies this field on the wire.
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* @param v The initial bit-string value.
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*/
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STBitString(SField const& n, value_type const& v);
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/** Deserialize a named field from a byte stream.
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*
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* Reads exactly `Bits/8` bytes from `sit` at the current cursor
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* position via `SerialIter::getBitString<Bits>()`, centralizing
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* deserialization logic in `SerialIter`.
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*
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* @param sit The input cursor; advanced by `Bits/8` bytes on success.
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* @param name The `SField` that identifies this field on the wire.
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* @throws std::runtime_error if the stream has fewer than `Bits/8`
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* bytes remaining.
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*/
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STBitString(SerialIter& sit, SField const& name);
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/** Return the wire-type identifier for this bit width.
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*
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* Specialized for each concrete alias: `STI_UINT128`, `STI_UINT160`,
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* `STI_UINT192`, and `STI_UINT256`.
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*
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* @return The `SerializedTypeID` matching this instantiation's bit width.
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*/
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[[nodiscard]] SerializedTypeID
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getSType() const override;
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/** Return the hex-encoded string representation of the stored value.
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*
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* @return A lowercase hex string with no prefix.
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*/
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[[nodiscard]] std::string
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getText() const override;
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/** Test whether this field holds the same value as another `STBitString`.
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*
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* @param t The object to compare against.
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* @return `true` if `t` is the same concrete bit width and both values
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* are equal; `false` otherwise (including when `t` has a different
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* bit width).
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*/
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[[nodiscard]] bool
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isEquivalent(STBase const& t) const override;
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/** Serialize the value into a `Serializer` byte buffer.
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*
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* Writes exactly `Bits/8` bytes to `s` via `Serializer::addBitString`.
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*
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* @param s The accumulator to write into.
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* @pre `getFName().isBinary()` must be `true`.
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* @pre `getFName().fieldType` must equal `getSType()`.
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* @note Both preconditions are checked with `XRPL_ASSERT`; violations
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* indicate a field/type metadata mismatch that would cause silent
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* protocol corruption.
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*/
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void
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add(Serializer& s) const override;
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/** Return `true` when the stored value is the all-zeros bit string.
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*
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* The serialization layer uses this to decide whether a field may be
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* omitted from canonical binary encoding.
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*
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* @return `true` if the value equals `beast::zero`.
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*/
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[[nodiscard]] bool
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isDefault() const override;
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/** Assign a new value, accepting any tag variant of `BaseUInt<Bits>`.
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*
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* The free `Tag` template parameter allows cross-tag assignment (e.g.,
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* assigning a raw `uint256` to an `sfTransactionID` field) when the
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* caller explicitly intends it, while making accidental mixing visible
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* at the call site. Tag information is erased on storage.
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*
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* @tparam Tag The source tag type; any `BaseUInt<Bits, Tag>` is accepted.
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* @param v The new value.
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*/
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template <typename Tag>
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void
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setValue(BaseUInt<Bits, Tag> const& v);
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/** Return a const reference to the stored tag-free value.
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*
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* @return Reference to the internal `value_type`; valid for the lifetime
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* of this object.
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*/
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[[nodiscard]] value_type const&
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value() const;
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/** Implicit conversion to the tag-free `value_type`.
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*
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* Erases any tag information from the underlying `BaseUInt` on the way
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* out. Prefer `value()` in generic code to make the conversion explicit.
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*/
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operator value_type() const;
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private:
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/** Place-construct a copy into `buf` if it fits within `n` bytes;
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* otherwise heap-allocate. Called by `detail::STVar` for the
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* small-object optimisation inside `STObject` containers.
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*/
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STBase*
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copy(std::size_t n, void* buf) const override;
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/** Place-construct a moved instance into `buf` if it fits within `n`
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* bytes; otherwise heap-allocate. Called by `detail::STVar`.
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*/
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STBase*
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move(std::size_t n, void* buf) override;
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friend class detail::STVar;
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};
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/** Serialized 128-bit opaque bit string (wire type `STI_UINT128`). */
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using STUInt128 = STBitString<128>;
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/** Serialized 160-bit opaque bit string (wire type `STI_UINT160`).
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*
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* Used for `AccountID` fields and similar 20-byte identifiers.
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*/
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using STUInt160 = STBitString<160>;
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/** Serialized 192-bit opaque bit string (wire type `STI_UINT192`).
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*
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* Used for `MPTID` fields (32-bit sequence number ‖ 160-bit issuer).
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*/
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using STUInt192 = STBitString<192>;
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/** Serialized 256-bit opaque bit string (wire type `STI_UINT256`).
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*
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* The most commonly used alias; carries transaction hashes, ledger
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* indices, node IDs, and other 32-byte protocol identifiers.
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*/
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using STUInt256 = STBitString<256>;
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template <int Bits>
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inline STBitString<Bits>::STBitString(SField const& n) : STBase(n)
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{
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}
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template <int Bits>
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inline STBitString<Bits>::STBitString(value_type const& v) : value_(v)
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{
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}
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template <int Bits>
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inline STBitString<Bits>::STBitString(SField const& n, value_type const& v) : STBase(n), value_(v)
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{
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}
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template <int Bits>
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inline STBitString<Bits>::STBitString(SerialIter& sit, SField const& name)
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: STBitString(name, sit.getBitString<Bits>())
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{
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}
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template <int Bits>
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STBase*
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STBitString<Bits>::copy(std::size_t n, void* buf) const
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{
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return emplace(n, buf, *this);
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}
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template <int Bits>
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STBase*
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STBitString<Bits>::move(std::size_t n, void* buf)
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{
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return emplace(n, buf, std::move(*this));
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}
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template <>
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inline SerializedTypeID
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STUInt128::getSType() const
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{
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return STI_UINT128;
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}
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template <>
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inline SerializedTypeID
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STUInt160::getSType() const
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{
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return STI_UINT160;
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}
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template <>
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inline SerializedTypeID
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STUInt192::getSType() const
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{
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return STI_UINT192;
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}
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template <>
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inline SerializedTypeID
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STUInt256::getSType() const
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{
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return STI_UINT256;
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}
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template <int Bits>
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std::string
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STBitString<Bits>::getText() const
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{
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return to_string(value_);
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}
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template <int Bits>
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bool
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STBitString<Bits>::isEquivalent(STBase const& t) const
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{
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STBitString const* v = dynamic_cast<STBitString const*>(&t);
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return v && (value_ == v->value_);
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}
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template <int Bits>
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void
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STBitString<Bits>::add(Serializer& s) const
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{
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XRPL_ASSERT(getFName().isBinary(), "xrpl::STBitString::add : field is binary");
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XRPL_ASSERT(getFName().fieldType == getSType(), "xrpl::STBitString::add : field type match");
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s.addBitString<Bits>(value_);
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}
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template <int Bits>
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template <typename Tag>
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void
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STBitString<Bits>::setValue(BaseUInt<Bits, Tag> const& v)
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{
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value_ = v;
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}
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template <int Bits>
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typename STBitString<Bits>::value_type const&
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STBitString<Bits>::value() const
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{
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return value_;
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}
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template <int Bits>
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STBitString<Bits>::
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operator value_type() const
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{
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return value_;
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}
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template <int Bits>
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bool
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STBitString<Bits>::isDefault() const
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{
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return value_ == beast::kZERO;
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}
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} // namespace xrpl
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