diff options
Diffstat (limited to 'third_party/abseil_cpp/absl/strings/cord.h')
| -rw-r--r-- | third_party/abseil_cpp/absl/strings/cord.h | 206 |
1 files changed, 92 insertions, 114 deletions
diff --git a/third_party/abseil_cpp/absl/strings/cord.h b/third_party/abseil_cpp/absl/strings/cord.h index dc987454fa..5d5c897e66 100644 --- a/third_party/abseil_cpp/absl/strings/cord.h +++ b/third_party/abseil_cpp/absl/strings/cord.h @@ -71,7 +71,6 @@ #include <type_traits> #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" @@ -80,6 +79,7 @@ #include "absl/meta/type_traits.h" #include "absl/strings/internal/cord_internal.h" #include "absl/strings/internal/resize_uninitialized.h" +#include "absl/strings/internal/string_constant.h" #include "absl/strings/string_view.h" #include "absl/types/optional.h" @@ -126,9 +126,9 @@ class Cord { absl::enable_if_t<std::is_same<T, std::string>::value, int>; public: - // Cord::Cord() Constructors + // Cord::Cord() Constructors. - // Creates an empty Cord + // Creates an empty Cord. constexpr Cord() noexcept; // Creates a Cord from an existing Cord. Cord is copyable and efficiently @@ -154,7 +154,7 @@ class Cord { // Cord::~Cord() // - // Destructs the Cord + // Destructs the Cord. ~Cord() { if (contents_.is_tree()) DestroyCordSlow(); } @@ -173,10 +173,6 @@ class Cord { // // * be move constructible // * support `void operator()(absl::string_view) const` or `void operator()` - // * not have alignment requirement greater than what is guaranteed by - // `::operator new`. This alignment is dictated by - // `alignof(std::max_align_t)` (pre-C++17 code) or - // `__STDCPP_DEFAULT_NEW_ALIGNMENT__` (C++17 code). // // Example: // @@ -592,7 +588,7 @@ class Cord { // Cord::operator[] // - // Get the "i"th character of the Cord and returns it, provided that + // Gets the "i"th character of the Cord and returns it, provided that // 0 <= i < Cord.size(). // // NOTE: This routine is reasonably efficient. It is roughly @@ -604,8 +600,8 @@ class Cord { // Cord::TryFlat() // - // If this cord's representation is a single flat array, return a - // string_view referencing that array. Otherwise return nullopt. + // If this cord's representation is a single flat array, returns a + // string_view referencing that array. Otherwise returns nullopt. absl::optional<absl::string_view> TryFlat() const; // Cord::Flatten() @@ -615,7 +611,7 @@ class Cord { // If the cord was already flat, the contents are not modified. absl::string_view Flatten(); - // Support absl::Cord as a sink object for absl::Format(). + // Supports absl::Cord as a sink object for absl::Format(). friend void AbslFormatFlush(absl::Cord* cord, absl::string_view part) { cord->Append(part); } @@ -629,12 +625,20 @@ class Cord { return c.HashFragmented(std::move(hash_state)); } + // Create a Cord with the contents of StringConstant<T>::value. + // No allocations will be done and no data will be copied. + // This is an INTERNAL API and subject to change or removal. This API can only + // be used by spelling absl::strings_internal::MakeStringConstant, which is + // also an internal API. + template <typename T> + explicit constexpr Cord(strings_internal::StringConstant<T>); + private: friend class CordTestPeer; 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 + // Calls 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; @@ -649,19 +653,19 @@ class Cord { // InlineRep holds either a tree pointer, or an array of kMaxInline bytes. class InlineRep { public: - static constexpr unsigned char kMaxInline = 15; + static constexpr unsigned char kMaxInline = cord_internal::kMaxInline; static_assert(kMaxInline >= sizeof(absl::cord_internal::CordRep*), ""); - // Tag byte & kMaxInline means we are storing a pointer. - static constexpr unsigned char kTreeFlag = 1 << 4; - // Tag byte & kProfiledFlag means we are profiling the Cord. - static constexpr unsigned char kProfiledFlag = 1 << 5; + static constexpr unsigned char kTreeFlag = cord_internal::kTreeFlag; + static constexpr unsigned char kProfiledFlag = cord_internal::kProfiledFlag; - constexpr InlineRep() : data_{} {} + constexpr InlineRep() : data_() {} InlineRep(const InlineRep& src); InlineRep(InlineRep&& src); InlineRep& operator=(const InlineRep& src); InlineRep& operator=(InlineRep&& src) noexcept; + explicit constexpr InlineRep(cord_internal::InlineData data); + void Swap(InlineRep* rhs); bool empty() const; size_t size() const; @@ -678,7 +682,7 @@ class Cord { 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 + // Converts 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 @@ -689,16 +693,16 @@ class Cord { 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; + 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)); + // Use memcpy to avoid 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)); + memcpy(&x, reinterpret_cast<const char*>(&data_) + 8, sizeof(x)); + memcpy(&y, reinterpret_cast<const char*>(&other.data_) + 8, sizeof(y)); if (x == y) return 0; } return absl::big_endian::FromHost64(x) < absl::big_endian::FromHost64(y) @@ -711,16 +715,16 @@ class Cord { // to 15 bytes does not cause a memory allocation. absl::strings_internal::STLStringResizeUninitialized(dst, sizeof(data_) - 1); - memcpy(&(*dst)[0], data_, 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]); + dst->erase(tagged_size()); } // 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; } + bool is_tree() const { return tagged_size() > kMaxInline; } private: friend class Cord; @@ -729,21 +733,29 @@ class Cord { // 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]; + void ResetToEmpty() { data_ = {}; } + + // This uses reinterpret_cast instead of the union to avoid accessing the + // inactive union element. The tagged size is not a common prefix. + void set_tagged_size(char new_tag) { + reinterpret_cast<char*>(&data_)[kMaxInline] = new_tag; + } + char tagged_size() const { + return reinterpret_cast<const char*>(&data_)[kMaxInline]; + } + + cord_internal::InlineData data_; }; InlineRep contents_; - // Helper for MemoryUsage() + // Helper for MemoryUsage(). static size_t MemoryUsageAux(const absl::cord_internal::CordRep* rep); - // Helper for GetFlat() and TryFlat() + // Helper for GetFlat() and TryFlat(). static bool GetFlatAux(absl::cord_internal::CordRep* rep, absl::string_view* fragment); - // Helper for ForEachChunk() + // Helper for ForEachChunk(). static void ForEachChunkAux( absl::cord_internal::CordRep* rep, absl::FunctionRef<void(absl::string_view)> callback); @@ -772,11 +784,11 @@ class Cord { absl::cord_internal::CordRep* TakeRep() const&; absl::cord_internal::CordRep* TakeRep() &&; - // Helper for Append() + // Helper for Append(). template <typename C> void AppendImpl(C&& src); - // Helper for AbslHashValue() + // Helper for AbslHashValue(). template <typename H> H HashFragmented(H hash_state) const { typename H::AbslInternalPiecewiseCombiner combiner; @@ -842,47 +854,15 @@ inline void SmallMemmove(char* dst, const char* src, size_t n, } } -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. +// Does non-template-specific `CordRepExternal` initialization. // Expects `data` to be non-empty. -ExternalRepReleaserPair NewExternalWithUninitializedReleaser( - absl::string_view data, ExternalReleaserInvoker invoker, - size_t releaser_size); - -struct Rank1 {}; -struct Rank0 : Rank1 {}; - -template <typename Releaser, typename = ::absl::base_internal::InvokeT< - Releaser, absl::string_view>> -void InvokeReleaser(Rank0, Releaser&& releaser, absl::string_view data) { - ::absl::base_internal::Invoke(std::forward<Releaser>(releaser), data); -} - -template <typename Releaser, - typename = ::absl::base_internal::InvokeT<Releaser>> -void InvokeReleaser(Rank1, Releaser&& releaser, absl::string_view) { - ::absl::base_internal::Invoke(std::forward<Releaser>(releaser)); -} +void InitializeCordRepExternal(absl::string_view data, CordRepExternal* rep); // 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. @@ -891,18 +871,10 @@ CordRep* NewExternalRep(absl::string_view data, Releaser&& releaser) { return nullptr; } - auto releaser_invoker = [](void* type_erased_releaser, absl::string_view d) { - auto* my_releaser = static_cast<ReleaserType*>(type_erased_releaser); - InvokeReleaser(Rank0{}, 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; + CordRepExternal* rep = new CordRepExternalImpl<ReleaserType>( + std::forward<Releaser>(releaser), 0); + InitializeCordRepExternal(data, rep); + return rep; } // Overload for function reference types that dispatches using a function @@ -923,13 +895,16 @@ Cord MakeCordFromExternal(absl::string_view data, Releaser&& releaser) { return cord; } +constexpr Cord::InlineRep::InlineRep(cord_internal::InlineData data) + : data_(data) {} + inline Cord::InlineRep::InlineRep(const Cord::InlineRep& src) { - cord_internal::SmallMemmove(data_, src.data_, sizeof(data_)); + data_ = src.data_; } inline Cord::InlineRep::InlineRep(Cord::InlineRep&& src) { - memcpy(data_, src.data_, sizeof(data_)); - memset(src.data_, 0, sizeof(data_)); + data_ = src.data_; + src.ResetToEmpty(); } inline Cord::InlineRep& Cord::InlineRep::operator=(const Cord::InlineRep& src) { @@ -937,7 +912,7 @@ inline Cord::InlineRep& Cord::InlineRep::operator=(const Cord::InlineRep& src) { return *this; } if (!is_tree() && !src.is_tree()) { - cord_internal::SmallMemmove(data_, src.data_, sizeof(data_)); + data_ = src.data_; return *this; } AssignSlow(src); @@ -949,8 +924,8 @@ inline Cord::InlineRep& Cord::InlineRep::operator=( if (is_tree()) { ClearSlow(); } - memcpy(data_, src.data_, sizeof(data_)); - memset(src.data_, 0, sizeof(data_)); + data_ = src.data_; + src.ResetToEmpty(); return *this; } @@ -959,43 +934,39 @@ inline void Cord::InlineRep::Swap(Cord::InlineRep* rhs) { 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_)); + std::swap(data_, rhs->data_); } inline const char* Cord::InlineRep::data() const { - return is_tree() ? nullptr : data_; + return is_tree() ? nullptr : data_.as_chars; } inline absl::cord_internal::CordRep* Cord::InlineRep::tree() const { if (is_tree()) { - absl::cord_internal::CordRep* rep; - memcpy(&rep, data_, sizeof(rep)); - return rep; + return data_.as_tree.rep; } else { return nullptr; } } -inline bool Cord::InlineRep::empty() const { return data_[kMaxInline] == 0; } +inline bool Cord::InlineRep::empty() const { return tagged_size() == 0; } inline size_t Cord::InlineRep::size() const { - const char tag = data_[kMaxInline]; + const char tag = tagged_size(); 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_)); + ResetToEmpty(); } else { bool was_tree = is_tree(); - memcpy(data_, &rep, sizeof(rep)); - memset(data_ + sizeof(rep), 0, sizeof(data_) - sizeof(rep) - 1); + data_.as_tree = {rep, {}, tagged_size()}; if (!was_tree) { - data_[kMaxInline] = kTreeFlag; + // If we were not a tree already, set the tag. + // Otherwise, leave it alone because it might have the profile bit on. + set_tagged_size(kTreeFlag); } } } @@ -1006,29 +977,36 @@ inline void Cord::InlineRep::replace_tree(absl::cord_internal::CordRep* rep) { set_tree(rep); return; } - memcpy(data_, &rep, sizeof(rep)); - memset(data_ + sizeof(rep), 0, sizeof(data_) - sizeof(rep) - 1); + data_.as_tree = {rep, {}, tagged_size()}; } 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 + absl::cord_internal::CordRep* result = tree(); + ResetToEmpty(); return result; } inline void Cord::InlineRep::CopyToArray(char* dst) const { assert(!is_tree()); - size_t n = data_[kMaxInline]; + size_t n = tagged_size(); assert(n != 0); - cord_internal::SmallMemmove(dst, data_, n); + cord_internal::SmallMemmove(dst, data_.as_chars, n); } constexpr inline Cord::Cord() noexcept {} +template <typename T> +constexpr Cord::Cord(strings_internal::StringConstant<T>) + : contents_(strings_internal::StringConstant<T>::value.size() <= + cord_internal::kMaxInline + ? cord_internal::InlineData( + strings_internal::StringConstant<T>::value) + : cord_internal::InlineData(cord_internal::AsTree{ + &cord_internal::ConstInitExternalStorage< + strings_internal::StringConstant<T>>::value, + {}, + cord_internal::kTreeFlag})) {} + inline Cord& Cord::operator=(const Cord& x) { contents_ = x.contents_; return *this; |