diff options
Diffstat (limited to 'absl/strings/cord.h')
| -rw-r--r-- | absl/strings/cord.h | 1121 |
1 files changed, 1121 insertions, 0 deletions
diff --git a/absl/strings/cord.h b/absl/strings/cord.h new file mode 100644 index 000000000000..40566cbaa011 --- /dev/null +++ b/absl/strings/cord.h @@ -0,0 +1,1121 @@ +// Copyright 2020 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +// A Cord is a sequence of characters with some unusual access propreties. +// A Cord supports efficient insertions and deletions at the start and end of +// the byte sequence, but random access reads are slower, and random access +// modifications are not supported by the API. Cord also provides cheap copies +// (using a copy-on-write strategy) and cheap substring operations. +// +// Thread safety +// ------------- +// Cord has the same thread-safety properties as many other types like +// std::string, std::vector<>, int, etc -- it is thread-compatible. In +// particular, if no thread may call a non-const method, then it is safe to +// concurrently call const methods. Copying a Cord produces a new instance that +// can be used concurrently with the original in arbitrary ways. +// +// Implementation is similar to the "Ropes" described in: +// Ropes: An alternative to strings +// Hans J. Boehm, Russ Atkinson, Michael Plass +// Software Practice and Experience, December 1995 + +#ifndef ABSL_STRINGS_CORD_H_ +#define ABSL_STRINGS_CORD_H_ + +#include <algorithm> +#include <cstddef> +#include <cstdint> +#include <cstring> +#include <iostream> +#include <iterator> +#include <string> + +#include "absl/base/internal/endian.h" +#include "absl/base/internal/invoke.h" +#include "absl/base/internal/per_thread_tls.h" +#include "absl/base/macros.h" +#include "absl/base/port.h" +#include "absl/container/inlined_vector.h" +#include "absl/functional/function_ref.h" +#include "absl/meta/type_traits.h" +#include "absl/strings/internal/cord_internal.h" +#include "absl/strings/internal/resize_uninitialized.h" +#include "absl/strings/string_view.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +class Cord; +class CordTestPeer; +template <typename Releaser> +Cord MakeCordFromExternal(absl::string_view, Releaser&&); +void CopyCordToString(const Cord& src, std::string* dst); +namespace hash_internal { +template <typename H> +H HashFragmentedCord(H, const Cord&); +} + +// A Cord is a sequence of characters. +class Cord { + private: + template <typename T> + using EnableIfString = + absl::enable_if_t<std::is_same<T, std::string>::value, int>; + + public: + // -------------------------------------------------------------------- + // Constructors, destructors and helper factories + + // Create an empty cord + constexpr Cord() noexcept; + + // Cord is copyable and efficiently movable. + // The moved-from state is valid but unspecified. + Cord(const Cord& src); + Cord(Cord&& src) noexcept; + Cord& operator=(const Cord& x); + Cord& operator=(Cord&& x) noexcept; + + // Create a cord out of "src". This constructor is explicit on + // purpose so that people do not get automatic type conversions. + explicit Cord(absl::string_view src); + Cord& operator=(absl::string_view src); + + // These are templated to avoid ambiguities for types that are convertible to + // both `absl::string_view` and `std::string`, such as `const char*`. + // + // Note that these functions reserve the right to reuse the `string&&`'s + // memory and that they will do so in the future. + template <typename T, EnableIfString<T> = 0> + explicit Cord(T&& src) : Cord(absl::string_view(src)) {} + template <typename T, EnableIfString<T> = 0> + Cord& operator=(T&& src); + + // Destroy the cord + ~Cord() { + if (contents_.is_tree()) DestroyCordSlow(); + } + + // Creates a Cord that takes ownership of external memory. The contents of + // `data` are not copied. + // + // This function takes a callable that is invoked when all Cords are + // finished with `data`. The data must remain live and unchanging until the + // releaser is called. The requirements for the releaser are that it: + // * is move constructible, + // * supports `void operator()(absl::string_view) const`, + // * does not have alignment requirement greater than what is guaranteed by + // ::operator new. This is dictated by alignof(std::max_align_t) before + // C++17 and __STDCPP_DEFAULT_NEW_ALIGNMENT__ if compiling with C++17 or + // it is supported by the implementation. + // + // Example: + // + // Cord MakeCord(BlockPool* pool) { + // Block* block = pool->NewBlock(); + // FillBlock(block); + // return absl::MakeCordFromExternal( + // block->ToStringView(), + // [pool, block](absl::string_view /*ignored*/) { + // pool->FreeBlock(block); + // }); + // } + // + // WARNING: It's likely a bug if your releaser doesn't do anything. + // For example, consider the following: + // + // void Foo(const char* buffer, int len) { + // auto c = absl::MakeCordFromExternal(absl::string_view(buffer, len), + // [](absl::string_view) {}); + // + // // BUG: If Bar() copies its cord for any reason, including keeping a + // // substring of it, the lifetime of buffer might be extended beyond + // // when Foo() returns. + // Bar(c); + // } + template <typename Releaser> + friend Cord MakeCordFromExternal(absl::string_view data, Releaser&& releaser); + + // -------------------------------------------------------------------- + // Mutations + + void Clear(); + + void Append(const Cord& src); + void Append(Cord&& src); + void Append(absl::string_view src); + template <typename T, EnableIfString<T> = 0> + void Append(T&& src); + + void Prepend(const Cord& src); + void Prepend(absl::string_view src); + template <typename T, EnableIfString<T> = 0> + void Prepend(T&& src); + + void RemovePrefix(size_t n); + void RemoveSuffix(size_t n); + + // Returns a new cord representing the subrange [pos, pos + new_size) of + // *this. If pos >= size(), the result is empty(). If + // (pos + new_size) >= size(), the result is the subrange [pos, size()). + Cord Subcord(size_t pos, size_t new_size) const; + + friend void swap(Cord& x, Cord& y) noexcept; + + // -------------------------------------------------------------------- + // Accessors + + size_t size() const; + bool empty() const; + + // Returns the approximate number of bytes pinned by this Cord. Note that + // Cords that share memory could each be "charged" independently for the same + // shared memory. + size_t EstimatedMemoryUsage() const; + + // -------------------------------------------------------------------- + // Comparators + + // Compares 'this' Cord with rhs. This function and its relatives + // treat Cords as sequences of unsigned bytes. The comparison is a + // straightforward lexicographic comparison. Return value: + // -1 'this' Cord is smaller + // 0 two Cords are equal + // 1 'this' Cord is larger + int Compare(absl::string_view rhs) const; + int Compare(const Cord& rhs) const; + + // Does 'this' cord start/end with rhs + bool StartsWith(const Cord& rhs) const; + bool StartsWith(absl::string_view rhs) const; + bool EndsWith(absl::string_view rhs) const; + bool EndsWith(const Cord& rhs) const; + + // -------------------------------------------------------------------- + // Conversion to other types + + explicit operator std::string() const; + + // Copies the contents from `src` to `*dst`. + // + // This function optimizes the case of reusing the destination std::string since it + // can reuse previously allocated capacity. However, this function does not + // guarantee that pointers previously returned by `dst->data()` remain valid + // even if `*dst` had enough capacity to hold `src`. If `*dst` is a new + // object, prefer to simply use the conversion operator to `std::string`. + friend void CopyCordToString(const Cord& src, std::string* dst); + + // -------------------------------------------------------------------- + // Iteration + + class CharIterator; + + // Type for iterating over the chunks of a `Cord`. See comments for + // `Cord::chunk_begin()`, `Cord::chunk_end()` and `Cord::Chunks()` below for + // preferred usage. + // + // Additional notes: + // * The `string_view` returned by dereferencing a valid, non-`end()` + // iterator is guaranteed to be non-empty. + // * A `ChunkIterator` object is invalidated after any non-const + // operation on the `Cord` object over which it iterates. + // * Two `ChunkIterator` objects can be equality compared if and only if + // they remain valid and iterate over the same `Cord`. + // * This is a proxy iterator. This means the `string_view` returned by the + // iterator does not live inside the Cord, and its lifetime is limited to + // the lifetime of the iterator itself. To help prevent issues, + // `ChunkIterator::reference` is not a true reference type and is + // equivalent to `value_type`. + // * The iterator keeps state that can grow for `Cord`s that contain many + // nodes and are imbalanced due to sharing. Prefer to pass this type by + // const reference instead of by value. + class ChunkIterator { + public: + using iterator_category = std::input_iterator_tag; + using value_type = absl::string_view; + using difference_type = ptrdiff_t; + using pointer = const value_type*; + using reference = value_type; + + ChunkIterator() = default; + + ChunkIterator& operator++(); + ChunkIterator operator++(int); + bool operator==(const ChunkIterator& other) const; + bool operator!=(const ChunkIterator& other) const; + reference operator*() const; + pointer operator->() const; + + friend class Cord; + friend class CharIterator; + + private: + // Constructs a `begin()` iterator from `cord`. + explicit ChunkIterator(const Cord* cord); + + // Removes `n` bytes from `current_chunk_`. Expects `n` to be smaller than + // `current_chunk_.size()`. + void RemoveChunkPrefix(size_t n); + Cord AdvanceAndReadBytes(size_t n); + void AdvanceBytes(size_t n); + // Iterates `n` bytes, where `n` is expected to be greater than or equal to + // `current_chunk_.size()`. + void AdvanceBytesSlowPath(size_t n); + + // A view into bytes of the current `CordRep`. It may only be a view to a + // suffix of bytes if this is being used by `CharIterator`. + absl::string_view current_chunk_; + // The current leaf, or `nullptr` if the iterator points to short data. + // If the current chunk is a substring node, current_leaf_ points to the + // underlying flat or external node. + absl::cord_internal::CordRep* current_leaf_ = nullptr; + // The number of bytes left in the `Cord` over which we are iterating. + size_t bytes_remaining_ = 0; + absl::InlinedVector<absl::cord_internal::CordRep*, 4> + stack_of_right_children_; + }; + + // Returns an iterator to the first chunk of the `Cord`. + // + // This is useful for getting a `ChunkIterator` outside the context of a + // range-based for-loop (in which case see `Cord::Chunks()` below). + // + // Example: + // + // absl::Cord::ChunkIterator FindAsChunk(const absl::Cord& c, + // absl::string_view s) { + // return std::find(c.chunk_begin(), c.chunk_end(), s); + // } + ChunkIterator chunk_begin() const; + // Returns an iterator one increment past the last chunk of the `Cord`. + ChunkIterator chunk_end() const; + + // Convenience wrapper over `Cord::chunk_begin()` and `Cord::chunk_end()` to + // enable range-based for-loop iteration over `Cord` chunks. + // + // Prefer to use `Cord::Chunks()` below instead of constructing this directly. + class ChunkRange { + public: + explicit ChunkRange(const Cord* cord) : cord_(cord) {} + + ChunkIterator begin() const; + ChunkIterator end() const; + + private: + const Cord* cord_; + }; + + // Returns a range for iterating over the chunks of a `Cord` with a + // range-based for-loop. + // + // Example: + // + // void ProcessChunks(const Cord& cord) { + // for (absl::string_view chunk : cord.Chunks()) { ... } + // } + // + // Note that the ordinary caveats of temporary lifetime extension apply: + // + // void Process() { + // for (absl::string_view chunk : CordFactory().Chunks()) { + // // The temporary Cord returned by CordFactory has been destroyed! + // } + // } + ChunkRange Chunks() const; + + // Type for iterating over the characters of a `Cord`. See comments for + // `Cord::char_begin()`, `Cord::char_end()` and `Cord::Chars()` below for + // preferred usage. + // + // Additional notes: + // * A `CharIterator` object is invalidated after any non-const + // operation on the `Cord` object over which it iterates. + // * Two `CharIterator` objects can be equality compared if and only if + // they remain valid and iterate over the same `Cord`. + // * The iterator keeps state that can grow for `Cord`s that contain many + // nodes and are imbalanced due to sharing. Prefer to pass this type by + // const reference instead of by value. + // * This type cannot be a forward iterator because a `Cord` can reuse + // sections of memory. This violates the requirement that if dereferencing + // two iterators returns the same object, the iterators must compare + // equal. + class CharIterator { + public: + using iterator_category = std::input_iterator_tag; + using value_type = char; + using difference_type = ptrdiff_t; + using pointer = const char*; + using reference = const char&; + + CharIterator() = default; + + CharIterator& operator++(); + CharIterator operator++(int); + bool operator==(const CharIterator& other) const; + bool operator!=(const CharIterator& other) const; + reference operator*() const; + pointer operator->() const; + + friend Cord; + + private: + explicit CharIterator(const Cord* cord) : chunk_iterator_(cord) {} + + ChunkIterator chunk_iterator_; + }; + + // Advances `*it` by `n_bytes` and returns the bytes passed as a `Cord`. + // + // `n_bytes` must be less than or equal to the number of bytes remaining for + // iteration. Otherwise the behavior is undefined. It is valid to pass + // `char_end()` and 0. + static Cord AdvanceAndRead(CharIterator* it, size_t n_bytes); + + // Advances `*it` by `n_bytes`. + // + // `n_bytes` must be less than or equal to the number of bytes remaining for + // iteration. Otherwise the behavior is undefined. It is valid to pass + // `char_end()` and 0. + static void Advance(CharIterator* it, size_t n_bytes); + + // Returns the longest contiguous view starting at the iterator's position. + // + // `it` must be dereferenceable. + static absl::string_view ChunkRemaining(const CharIterator& it); + + // Returns an iterator to the first character of the `Cord`. + CharIterator char_begin() const; + // Returns an iterator to one past the last character of the `Cord`. + CharIterator char_end() const; + + // Convenience wrapper over `Cord::char_begin()` and `Cord::char_end()` to + // enable range-based for-loop iterator over the characters of a `Cord`. + // + // Prefer to use `Cord::Chars()` below instead of constructing this directly. + class CharRange { + public: + explicit CharRange(const Cord* cord) : cord_(cord) {} + + CharIterator begin() const; + CharIterator end() const; + + private: + const Cord* cord_; + }; + + // Returns a range for iterating over the characters of a `Cord` with a + // range-based for-loop. + // + // Example: + // + // void ProcessCord(const Cord& cord) { + // for (char c : cord.Chars()) { ... } + // } + // + // Note that the ordinary caveats of temporary lifetime extension apply: + // + // void Process() { + // for (char c : CordFactory().Chars()) { + // // The temporary Cord returned by CordFactory has been destroyed! + // } + // } + CharRange Chars() const; + + // -------------------------------------------------------------------- + // Miscellaneous + + // Get the "i"th character of 'this' and return it. + // NOTE: This routine is reasonably efficient. It is roughly + // logarithmic in the number of nodes that make up the cord. Still, + // if you need to iterate over the contents of a cord, you should + // use a CharIterator/CordIterator rather than call operator[] or Get() + // repeatedly in a loop. + // + // REQUIRES: 0 <= i < size() + char operator[](size_t i) const; + + // Flattens the cord into a single array and returns a view of the data. + // + // If the cord was already flat, the contents are not modified. + absl::string_view Flatten(); + + private: + friend class CordTestPeer; + template <typename H> + friend H absl::hash_internal::HashFragmentedCord(H, const Cord&); + friend bool operator==(const Cord& lhs, const Cord& rhs); + friend bool operator==(const Cord& lhs, absl::string_view rhs); + + // Call the provided function once for each cord chunk, in order. Unlike + // Chunks(), this API will not allocate memory. + void ForEachChunk(absl::FunctionRef<void(absl::string_view)>) const; + + // Allocates new contiguous storage for the contents of the cord. This is + // called by Flatten() when the cord was not already flat. + absl::string_view FlattenSlowPath(); + + // Actual cord contents are hidden inside the following simple + // class so that we can isolate the bulk of cord.cc from changes + // to the representation. + // + // InlineRep holds either either a tree pointer, or an array of kMaxInline + // bytes. + class InlineRep { + public: + static const unsigned char kMaxInline = 15; + static_assert(kMaxInline >= sizeof(absl::cord_internal::CordRep*), ""); + // Tag byte & kMaxInline means we are storing a pointer. + static const unsigned char kTreeFlag = 1 << 4; + // Tag byte & kProfiledFlag means we are profiling the Cord. + static const unsigned char kProfiledFlag = 1 << 5; + + constexpr InlineRep() : data_{} {} + InlineRep(const InlineRep& src); + InlineRep(InlineRep&& src); + InlineRep& operator=(const InlineRep& src); + InlineRep& operator=(InlineRep&& src) noexcept; + + void Swap(InlineRep* rhs); + bool empty() const; + size_t size() const; + const char* data() const; // Returns nullptr if holding pointer + void set_data(const char* data, size_t n, + bool nullify_tail); // Discards pointer, if any + char* set_data(size_t n); // Write data to the result + // Returns nullptr if holding bytes + absl::cord_internal::CordRep* tree() const; + // Discards old pointer, if any + void set_tree(absl::cord_internal::CordRep* rep); + // Replaces a tree with a new root. This is faster than set_tree, but it + // should only be used when it's clear that the old rep was a tree. + void replace_tree(absl::cord_internal::CordRep* rep); + // Returns non-null iff was holding a pointer + absl::cord_internal::CordRep* clear(); + // Convert to pointer if necessary + absl::cord_internal::CordRep* force_tree(size_t extra_hint); + void reduce_size(size_t n); // REQUIRES: holding data + void remove_prefix(size_t n); // REQUIRES: holding data + void AppendArray(const char* src_data, size_t src_size); + absl::string_view FindFlatStartPiece() const; + void AppendTree(absl::cord_internal::CordRep* tree); + void PrependTree(absl::cord_internal::CordRep* tree); + void GetAppendRegion(char** region, size_t* size, size_t max_length); + void GetAppendRegion(char** region, size_t* size); + bool IsSame(const InlineRep& other) const { + return memcmp(data_, other.data_, sizeof(data_)) == 0; + } + int BitwiseCompare(const InlineRep& other) const { + uint64_t x, y; + // Use memcpy to avoid anti-aliasing issues. + memcpy(&x, data_, sizeof(x)); + memcpy(&y, other.data_, sizeof(y)); + if (x == y) { + memcpy(&x, data_ + 8, sizeof(x)); + memcpy(&y, other.data_ + 8, sizeof(y)); + if (x == y) return 0; + } + return absl::big_endian::FromHost64(x) < absl::big_endian::FromHost64(y) + ? -1 + : 1; + } + void CopyTo(std::string* dst) const { + // memcpy is much faster when operating on a known size. On most supported + // platforms, the small std::string optimization is large enough that resizing + // to 15 bytes does not cause a memory allocation. + absl::strings_internal::STLStringResizeUninitialized(dst, + sizeof(data_) - 1); + memcpy(&(*dst)[0], data_, sizeof(data_) - 1); + // erase is faster than resize because the logic for memory allocation is + // not needed. + dst->erase(data_[kMaxInline]); + } + + // Copies the inline contents into `dst`. Assumes the cord is not empty. + void CopyToArray(char* dst) const; + + bool is_tree() const { return data_[kMaxInline] > kMaxInline; } + + private: + friend class Cord; + + void AssignSlow(const InlineRep& src); + // Unrefs the tree, stops profiling, and zeroes the contents + void ClearSlow(); + + // If the data has length <= kMaxInline, we store it in data_[0..len-1], + // and store the length in data_[kMaxInline]. Else we store it in a tree + // and store a pointer to that tree in data_[0..sizeof(CordRep*)-1]. + alignas(absl::cord_internal::CordRep*) char data_[kMaxInline + 1]; + }; + InlineRep contents_; + + // Helper for MemoryUsage() + static size_t MemoryUsageAux(const absl::cord_internal::CordRep* rep); + + // Helper for GetFlat() + static bool GetFlatAux(absl::cord_internal::CordRep* rep, + absl::string_view* fragment); + + // Helper for ForEachChunk() + static void ForEachChunkAux( + absl::cord_internal::CordRep* rep, + absl::FunctionRef<void(absl::string_view)> callback); + + // The destructor for non-empty Cords. + void DestroyCordSlow(); + + // Out-of-line implementation of slower parts of logic. + void CopyToArraySlowPath(char* dst) const; + int CompareSlowPath(absl::string_view rhs, size_t compared_size, + size_t size_to_compare) const; + int CompareSlowPath(const Cord& rhs, size_t compared_size, + size_t size_to_compare) const; + bool EqualsImpl(absl::string_view rhs, size_t size_to_compare) const; + bool EqualsImpl(const Cord& rhs, size_t size_to_compare) const; + int CompareImpl(const Cord& rhs) const; + + template <typename ResultType, typename RHS> + friend ResultType GenericCompare(const Cord& lhs, const RHS& rhs, + size_t size_to_compare); + static absl::string_view GetFirstChunk(const Cord& c); + static absl::string_view GetFirstChunk(absl::string_view sv); + + // Returns a new reference to contents_.tree(), or steals an existing + // reference if called on an rvalue. + absl::cord_internal::CordRep* TakeRep() const&; + absl::cord_internal::CordRep* TakeRep() &&; + + // Helper for Append() + template <typename C> + void AppendImpl(C&& src); +}; + +ABSL_NAMESPACE_END +} // namespace absl + +namespace absl { +ABSL_NAMESPACE_BEGIN + +// allow a Cord to be logged +extern std::ostream& operator<<(std::ostream& out, const Cord& cord); + +// ------------------------------------------------------------------ +// Internal details follow. Clients should ignore. + +namespace cord_internal { + +// Fast implementation of memmove for up to 15 bytes. This implementation is +// safe for overlapping regions. If nullify_tail is true, the destination is +// padded with '\0' up to 16 bytes. +inline void SmallMemmove(char* dst, const char* src, size_t n, + bool nullify_tail = false) { + if (n >= 8) { + assert(n <= 16); + uint64_t buf1; + uint64_t buf2; + memcpy(&buf1, src, 8); + memcpy(&buf2, src + n - 8, 8); + if (nullify_tail) { + memset(dst + 8, 0, 8); + } + memcpy(dst, &buf1, 8); + memcpy(dst + n - 8, &buf2, 8); + } else if (n >= 4) { + uint32_t buf1; + uint32_t buf2; + memcpy(&buf1, src, 4); + memcpy(&buf2, src + n - 4, 4); + if (nullify_tail) { + memset(dst + 4, 0, 4); + memset(dst + 8, 0, 8); + } + memcpy(dst, &buf1, 4); + memcpy(dst + n - 4, &buf2, 4); + } else { + if (n != 0) { + dst[0] = src[0]; + dst[n / 2] = src[n / 2]; + dst[n - 1] = src[n - 1]; + } + if (nullify_tail) { + memset(dst + 8, 0, 8); + memset(dst + n, 0, 8); + } + } +} + +struct ExternalRepReleaserPair { + CordRep* rep; + void* releaser_address; +}; + +// Allocates a new external `CordRep` and returns a pointer to it and a pointer +// to `releaser_size` bytes where the desired releaser can be constructed. +// Expects `data` to be non-empty. +ExternalRepReleaserPair NewExternalWithUninitializedReleaser( + absl::string_view data, ExternalReleaserInvoker invoker, + size_t releaser_size); + +// Creates a new `CordRep` that owns `data` and `releaser` and returns a pointer +// to it, or `nullptr` if `data` was empty. +template <typename Releaser> +// NOLINTNEXTLINE - suppress clang-tidy raw pointer return. +CordRep* NewExternalRep(absl::string_view data, Releaser&& releaser) { + static_assert( +#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__) + alignof(Releaser) <= __STDCPP_DEFAULT_NEW_ALIGNMENT__, +#else + alignof(Releaser) <= alignof(max_align_t), +#endif + "Releasers with alignment requirement greater than what is returned by " + "default `::operator new()` are not supported."); + + using ReleaserType = absl::decay_t<Releaser>; + if (data.empty()) { + // Never create empty external nodes. + ::absl::base_internal::Invoke( + ReleaserType(std::forward<Releaser>(releaser)), data); + return nullptr; + } + + auto releaser_invoker = [](void* type_erased_releaser, absl::string_view d) { + auto* my_releaser = static_cast<ReleaserType*>(type_erased_releaser); + ::absl::base_internal::Invoke(std::move(*my_releaser), d); + my_releaser->~ReleaserType(); + return sizeof(Releaser); + }; + + ExternalRepReleaserPair external = NewExternalWithUninitializedReleaser( + data, releaser_invoker, sizeof(releaser)); + ::new (external.releaser_address) + ReleaserType(std::forward<Releaser>(releaser)); + return external.rep; +} + +// Overload for function reference types that dispatches using a function +// pointer because there are no `alignof()` or `sizeof()` a function reference. +// NOLINTNEXTLINE - suppress clang-tidy raw pointer return. +inline CordRep* NewExternalRep(absl::string_view data, + void (&releaser)(absl::string_view)) { + return NewExternalRep(data, &releaser); +} + +} // namespace cord_internal + +template <typename Releaser> +Cord MakeCordFromExternal(absl::string_view data, Releaser&& releaser) { + Cord cord; + cord.contents_.set_tree(::absl::cord_internal::NewExternalRep( + data, std::forward<Releaser>(releaser))); + return cord; +} + +inline Cord::InlineRep::InlineRep(const Cord::InlineRep& src) { + cord_internal::SmallMemmove(data_, src.data_, sizeof(data_)); +} + +inline Cord::InlineRep::InlineRep(Cord::InlineRep&& src) { + memcpy(data_, src.data_, sizeof(data_)); + memset(src.data_, 0, sizeof(data_)); +} + +inline Cord::InlineRep& Cord::InlineRep::operator=(const Cord::InlineRep& src) { + if (this == &src) { + return *this; + } + if (!is_tree() && !src.is_tree()) { + cord_internal::SmallMemmove(data_, src.data_, sizeof(data_)); + return *this; + } + AssignSlow(src); + return *this; +} + +inline Cord::InlineRep& Cord::InlineRep::operator=( + Cord::InlineRep&& src) noexcept { + if (is_tree()) { + ClearSlow(); + } + memcpy(data_, src.data_, sizeof(data_)); + memset(src.data_, 0, sizeof(data_)); + return *this; +} + +inline void Cord::InlineRep::Swap(Cord::InlineRep* rhs) { + if (rhs == this) { + return; + } + + Cord::InlineRep tmp; + cord_internal::SmallMemmove(tmp.data_, data_, sizeof(data_)); + cord_internal::SmallMemmove(data_, rhs->data_, sizeof(data_)); + cord_internal::SmallMemmove(rhs->data_, tmp.data_, sizeof(data_)); +} + +inline const char* Cord::InlineRep::data() const { + return is_tree() ? nullptr : data_; +} + +inline absl::cord_internal::CordRep* Cord::InlineRep::tree() const { + if (is_tree()) { + absl::cord_internal::CordRep* rep; + memcpy(&rep, data_, sizeof(rep)); + return rep; + } else { + return nullptr; + } +} + +inline bool Cord::InlineRep::empty() const { return data_[kMaxInline] == 0; } + +inline size_t Cord::InlineRep::size() const { + const char tag = data_[kMaxInline]; + if (tag <= kMaxInline) return tag; + return static_cast<size_t>(tree()->length); +} + +inline void Cord::InlineRep::set_tree(absl::cord_internal::CordRep* rep) { + if (rep == nullptr) { + memset(data_, 0, sizeof(data_)); + } else { + bool was_tree = is_tree(); + memcpy(data_, &rep, sizeof(rep)); + memset(data_ + sizeof(rep), 0, sizeof(data_) - sizeof(rep) - 1); + if (!was_tree) { + data_[kMaxInline] = kTreeFlag; + } + } +} + +inline void Cord::InlineRep::replace_tree(absl::cord_internal::CordRep* rep) { + ABSL_ASSERT(is_tree()); + if (ABSL_PREDICT_FALSE(rep == nullptr)) { + set_tree(rep); + return; + } + memcpy(data_, &rep, sizeof(rep)); + memset(data_ + sizeof(rep), 0, sizeof(data_) - sizeof(rep) - 1); +} + +inline absl::cord_internal::CordRep* Cord::InlineRep::clear() { + const char tag = data_[kMaxInline]; + absl::cord_internal::CordRep* result = nullptr; + if (tag > kMaxInline) { + memcpy(&result, data_, sizeof(result)); + } + memset(data_, 0, sizeof(data_)); // Clear the cord + return result; +} + +inline void Cord::InlineRep::CopyToArray(char* dst) const { + assert(!is_tree()); + size_t n = data_[kMaxInline]; + assert(n != 0); + cord_internal::SmallMemmove(dst, data_, n); +} + +constexpr inline Cord::Cord() noexcept {} + +inline Cord& Cord::operator=(const Cord& x) { + contents_ = x.contents_; + return *this; +} + +inline Cord::Cord(Cord&& src) noexcept : contents_(std::move(src.contents_)) {} + +inline Cord& Cord::operator=(Cord&& x) noexcept { + contents_ = std::move(x.contents_); + return *this; +} + +template <typename T, Cord::EnableIfString<T>> +inline Cord& Cord::operator=(T&& src) { + *this = absl::string_view(src); + return *this; +} + +inline size_t Cord::size() const { + // Length is 1st field in str.rep_ + return contents_.size(); +} + +inline bool Cord::empty() const { return contents_.empty(); } + +inline size_t Cord::EstimatedMemoryUsage() const { + size_t result = sizeof(Cord); + if (const absl::cord_internal::CordRep* rep = contents_.tree()) { + result += MemoryUsageAux(rep); + } + return result; +} + +inline absl::string_view Cord::Flatten() { + absl::cord_internal::CordRep* rep = contents_.tree(); + if (rep == nullptr) { + return absl::string_view(contents_.data(), contents_.size()); + } else { + absl::string_view already_flat_contents; + if (GetFlatAux(rep, &already_flat_contents)) { + return already_flat_contents; + } + } + return FlattenSlowPath(); +} + +inline void Cord::Append(absl::string_view src) { + contents_.AppendArray(src.data(), src.size()); +} + +template <typename T, Cord::EnableIfString<T>> +inline void Cord::Append(T&& src) { + // Note that this function reserves the right to reuse the `string&&`'s + // memory and that it will do so in the future. + Append(absl::string_view(src)); +} + +template <typename T, Cord::EnableIfString<T>> +inline void Cord::Prepend(T&& src) { + // Note that this function reserves the right to reuse the `string&&`'s + // memory and that it will do so in the future. + Prepend(absl::string_view(src)); +} + +inline int Cord::Compare(const Cord& rhs) const { + if (!contents_.is_tree() && !rhs.contents_.is_tree()) { + return contents_.BitwiseCompare(rhs.contents_); + } + + return CompareImpl(rhs); +} + +// Does 'this' cord start/end with rhs +inline bool Cord::StartsWith(const Cord& rhs) const { + if (contents_.IsSame(rhs.contents_)) return true; + size_t rhs_size = rhs.size(); + if (size() < rhs_size) return false; + return EqualsImpl(rhs, rhs_size); +} + +inline bool Cord::StartsWith(absl::string_view rhs) const { + size_t rhs_size = rhs.size(); + if (size() < rhs_size) return false; + return EqualsImpl(rhs, rhs_size); +} + +inline Cord::ChunkIterator::ChunkIterator(const Cord* cord) + : bytes_remaining_(cord->size()) { + if (cord->empty()) return; + if (cord->contents_.is_tree()) { + stack_of_right_children_.push_back(cord->contents_.tree()); + operator++(); + } else { + current_chunk_ = absl::string_view(cord->contents_.data(), cord->size()); + } +} + +inline Cord::ChunkIterator Cord::ChunkIterator::operator++(int) { + ChunkIterator tmp(*this); + operator++(); + return tmp; +} + +inline bool Cord::ChunkIterator::operator==(const ChunkIterator& other) const { + return bytes_remaining_ == other.bytes_remaining_; +} + +inline bool Cord::ChunkIterator::operator!=(const ChunkIterator& other) const { + return !(*this == other); +} + +inline Cord::ChunkIterator::reference Cord::ChunkIterator::operator*() const { + assert(bytes_remaining_ != 0); + return current_chunk_; +} + +inline Cord::ChunkIterator::pointer Cord::ChunkIterator::operator->() const { + assert(bytes_remaining_ != 0); + return ¤t_chunk_; +} + +inline void Cord::ChunkIterator::RemoveChunkPrefix(size_t n) { + assert(n < current_chunk_.size()); + current_chunk_.remove_prefix(n); + bytes_remaining_ -= n; +} + +inline void Cord::ChunkIterator::AdvanceBytes(size_t n) { + if (ABSL_PREDICT_TRUE(n < current_chunk_.size())) { + RemoveChunkPrefix(n); + } else if (n != 0) { + AdvanceBytesSlowPath(n); + } +} + +inline Cord::ChunkIterator Cord::chunk_begin() const { + return ChunkIterator(this); +} + +inline Cord::ChunkIterator Cord::chunk_end() const { return ChunkIterator(); } + +inline Cord::ChunkIterator Cord::ChunkRange::begin() const { + return cord_->chunk_begin(); +} + +inline Cord::ChunkIterator Cord::ChunkRange::end() const { + return cord_->chunk_end(); +} + +inline Cord::ChunkRange Cord::Chunks() const { return ChunkRange(this); } + +inline Cord::CharIterator& Cord::CharIterator::operator++() { + if (ABSL_PREDICT_TRUE(chunk_iterator_->size() > 1)) { + chunk_iterator_.RemoveChunkPrefix(1); + } else { + ++chunk_iterator_; + } + return *this; +} + +inline Cord::CharIterator Cord::CharIterator::operator++(int) { + CharIterator tmp(*this); + operator++(); + return tmp; +} + +inline bool Cord::CharIterator::operator==(const CharIterator& other) const { + return chunk_iterator_ == other.chunk_iterator_; +} + +inline bool Cord::CharIterator::operator!=(const CharIterator& other) const { + return !(*this == other); +} + +inline Cord::CharIterator::reference Cord::CharIterator::operator*() const { + return *chunk_iterator_->data(); +} + +inline Cord::CharIterator::pointer Cord::CharIterator::operator->() const { + return chunk_iterator_->data(); +} + +inline Cord Cord::AdvanceAndRead(CharIterator* it, size_t n_bytes) { + assert(it != nullptr); + return it->chunk_iterator_.AdvanceAndReadBytes(n_bytes); +} + +inline void Cord::Advance(CharIterator* it, size_t n_bytes) { + assert(it != nullptr); + it->chunk_iterator_.AdvanceBytes(n_bytes); +} + +inline absl::string_view Cord::ChunkRemaining(const CharIterator& it) { + return *it.chunk_iterator_; +} + +inline Cord::CharIterator Cord::char_begin() const { + return CharIterator(this); +} + +inline Cord::CharIterator Cord::char_end() const { return CharIterator(); } + +inline Cord::CharIterator Cord::CharRange::begin() const { + return cord_->char_begin(); +} + +inline Cord::CharIterator Cord::CharRange::end() const { + return cord_->char_end(); +} + +inline Cord::CharRange Cord::Chars() const { return CharRange(this); } + +inline void Cord::ForEachChunk( + absl::FunctionRef<void(absl::string_view)> callback) const { + absl::cord_internal::CordRep* rep = contents_.tree(); + if (rep == nullptr) { + callback(absl::string_view(contents_.data(), contents_.size())); + } else { + return ForEachChunkAux(rep, callback); + } +} + +// Nonmember Cord-to-Cord relational operarators. +inline bool operator==(const Cord& lhs, const Cord& rhs) { + if (lhs.contents_.IsSame(rhs.contents_)) return true; + size_t rhs_size = rhs.size(); + if (lhs.size() != rhs_size) return false; + return lhs.EqualsImpl(rhs, rhs_size); +} + +inline bool operator!=(const Cord& x, const Cord& y) { return !(x == y); } +inline bool operator<(const Cord& x, const Cord& y) { + return x.Compare(y) < 0; +} +inline bool operator>(const Cord& x, const Cord& y) { + return x.Compare(y) > 0; +} +inline bool operator<=(const Cord& x, const Cord& y) { + return x.Compare(y) <= 0; +} +inline bool operator>=(const Cord& x, const Cord& y) { + return x.Compare(y) >= 0; +} + +// Nonmember Cord-to-absl::string_view relational operators. +// +// Due to implicit conversions, these also enable comparisons of Cord with +// with std::string, ::string, and const char*. +inline bool operator==(const Cord& lhs, absl::string_view rhs) { + size_t lhs_size = lhs.size(); + size_t rhs_size = rhs.size(); + if (lhs_size != rhs_size) return false; + return lhs.EqualsImpl(rhs, rhs_size); +} + +inline bool operator==(absl::string_view x, const Cord& y) { return y == x; } +inline bool operator!=(const Cord& x, absl::string_view y) { return !(x == y); } +inline bool operator!=(absl::string_view x, const Cord& y) { return !(x == y); } +inline bool operator<(const Cord& x, absl::string_view y) { + return x.Compare(y) < 0; +} +inline bool operator<(absl::string_view x, const Cord& y) { + return y.Compare(x) > 0; +} +inline bool operator>(const Cord& x, absl::string_view y) { return y < x; } +inline bool operator>(absl::string_view x, const Cord& y) { return y < x; } +inline bool operator<=(const Cord& x, absl::string_view y) { return !(y < x); } +inline bool operator<=(absl::string_view x, const Cord& y) { return !(y < x); } +inline bool operator>=(const Cord& x, absl::string_view y) { return !(x < y); } +inline bool operator>=(absl::string_view x, const Cord& y) { return !(x < y); } + +// Overload of swap for Cord. The use of non-const references is +// required. :( +inline void swap(Cord& x, Cord& y) noexcept { y.contents_.Swap(&x.contents_); } + +// Some internals exposed to test code. +namespace strings_internal { +class CordTestAccess { + public: + static size_t FlatOverhead(); + static size_t MaxFlatLength(); + static size_t SizeofCordRepConcat(); + static size_t SizeofCordRepExternal(); + static size_t SizeofCordRepSubstring(); + static size_t FlatTagToLength(uint8_t tag); + static uint8_t LengthToTag(size_t s); +}; +} // namespace strings_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STRINGS_CORD_H_ |