diff options
Diffstat (limited to 'third_party/abseil-cpp/absl/strings/internal/cord_internal.h')
| -rw-r--r-- | third_party/abseil-cpp/absl/strings/internal/cord_internal.h | 577 |
1 files changed, 523 insertions, 54 deletions
diff --git a/third_party/abseil-cpp/absl/strings/internal/cord_internal.h b/third_party/abseil-cpp/absl/strings/internal/cord_internal.h index 5b5d108308..bfe5564e46 100644 --- a/third_party/abseil-cpp/absl/strings/internal/cord_internal.h +++ b/third_party/abseil-cpp/absl/strings/internal/cord_internal.h @@ -1,4 +1,4 @@ -// Copyright 2020 The Abseil Authors. +// Copyright 2021 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. @@ -21,6 +21,11 @@ #include <cstdint> #include <type_traits> +#include "absl/base/config.h" +#include "absl/base/internal/endian.h" +#include "absl/base/internal/invoke.h" +#include "absl/base/optimization.h" +#include "absl/container/internal/compressed_tuple.h" #include "absl/meta/type_traits.h" #include "absl/strings/string_view.h" @@ -28,49 +33,153 @@ namespace absl { ABSL_NAMESPACE_BEGIN namespace cord_internal { -// Wraps std::atomic for reference counting. -class Refcount { +class CordzInfo; + +// Default feature enable states for cord ring buffers +enum CordFeatureDefaults { + kCordEnableBtreeDefault = true, + kCordEnableRingBufferDefault = false, + kCordShallowSubcordsDefault = false +}; + +extern std::atomic<bool> cord_btree_enabled; +extern std::atomic<bool> cord_ring_buffer_enabled; +extern std::atomic<bool> shallow_subcords_enabled; + +// `cord_btree_exhaustive_validation` can be set to force exhaustive validation +// in debug assertions, and code that calls `IsValid()` explicitly. By default, +// assertions should be relatively cheap and AssertValid() can easily lead to +// O(n^2) complexity as recursive / full tree validation is O(n). +extern std::atomic<bool> cord_btree_exhaustive_validation; + +inline void enable_cord_btree(bool enable) { + cord_btree_enabled.store(enable, std::memory_order_relaxed); +} + +inline void enable_cord_ring_buffer(bool enable) { + cord_ring_buffer_enabled.store(enable, std::memory_order_relaxed); +} + +inline void enable_shallow_subcords(bool enable) { + shallow_subcords_enabled.store(enable, std::memory_order_relaxed); +} + +enum Constants { + // The inlined size to use with absl::InlinedVector. + // + // Note: The InlinedVectors in this file (and in cord.h) do not need to use + // the same value for their inlined size. The fact that they do is historical. + // It may be desirable for each to use a different inlined size optimized for + // that InlinedVector's usage. + // + // TODO(jgm): Benchmark to see if there's a more optimal value than 47 for + // the inlined vector size (47 exists for backward compatibility). + kInlinedVectorSize = 47, + + // Prefer copying blocks of at most this size, otherwise reference count. + kMaxBytesToCopy = 511 +}; + +// Compact class for tracking the reference count and state flags for CordRep +// instances. Data is stored in an atomic int32_t for compactness and speed. +class RefcountAndFlags { public: - Refcount() : count_{1} {} - ~Refcount() {} + constexpr RefcountAndFlags() : count_{kRefIncrement} {} + struct Immortal {}; + explicit constexpr RefcountAndFlags(Immortal) : count_(kImmortalFlag) {} + struct WithCrc {}; + explicit constexpr RefcountAndFlags(WithCrc) + : count_(kCrcFlag | kRefIncrement) {} - // Increments the reference count by 1. Imposes no memory ordering. - inline void Increment() { count_.fetch_add(1, std::memory_order_relaxed); } + // Increments the reference count. Imposes no memory ordering. + inline void Increment() { + count_.fetch_add(kRefIncrement, std::memory_order_relaxed); + } // Asserts that the current refcount is greater than 0. If the refcount is - // greater than 1, decrements the reference count by 1. + // greater than 1, decrements the reference count. // // Returns false if there are no references outstanding; true otherwise. // Inserts barriers to ensure that state written before this method returns // false will be visible to a thread that just observed this method returning - // false. + // false. Always returns false when the immortal bit is set. inline bool Decrement() { - int32_t refcount = count_.load(std::memory_order_acquire); - assert(refcount > 0); - return refcount != 1 && count_.fetch_sub(1, std::memory_order_acq_rel) != 1; + int32_t refcount = count_.load(std::memory_order_acquire) & kRefcountMask; + assert(refcount > 0 || refcount & kImmortalFlag); + return refcount != kRefIncrement && + (count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel) & + kRefcountMask) != kRefIncrement; } // Same as Decrement but expect that refcount is greater than 1. inline bool DecrementExpectHighRefcount() { - int32_t refcount = count_.fetch_sub(1, std::memory_order_acq_rel); - assert(refcount > 0); - return refcount != 1; + int32_t refcount = + count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel) & + kRefcountMask; + assert(refcount > 0 || refcount & kImmortalFlag); + return refcount != kRefIncrement; } // Returns the current reference count using acquire semantics. - inline int32_t Get() const { return count_.load(std::memory_order_acquire); } - - // Returns whether the atomic integer is 1. - // If the reference count is used in the conventional way, a - // reference count of 1 implies that the current thread owns the - // reference and no other thread shares it. - // This call performs the test for a reference count of one, and - // performs the memory barrier needed for the owning thread - // to act on the object, knowing that it has exclusive access to the - // object. - inline bool IsOne() { return count_.load(std::memory_order_acquire) == 1; } + inline int32_t Get() const { + return count_.load(std::memory_order_acquire) >> kNumFlags; + } + + // Returns true if the referenced object carries a CRC value. + bool HasCrc() const { + return (count_.load(std::memory_order_relaxed) & kCrcFlag) != 0; + } + + // Returns true iff the atomic integer is 1 and this node does not store + // a CRC. When both these conditions are met, the current thread owns + // the reference and no other thread shares it, so its contents may be + // safely mutated. + // + // If the referenced item is shared, carries a CRC, or is immortal, + // it should not be modified in-place, and this function returns false. + // + // This call performs the memory barrier needed for the owning thread + // to act on the object, so that if it returns true, it may safely + // assume exclusive access to the object. + inline bool IsMutable() { + return (count_.load(std::memory_order_acquire)) == kRefIncrement; + } + + // Returns whether the atomic integer is 1. Similar to IsMutable(), + // but does not check for a stored CRC. (An unshared node with a CRC is not + // mutable, because changing its data would invalidate the CRC.) + // + // When this returns true, there are no other references, and data sinks + // may safely adopt the children of the CordRep. + inline bool IsOne() { + return (count_.load(std::memory_order_acquire) & kRefcountMask) == + kRefIncrement; + } + + bool IsImmortal() const { + return (count_.load(std::memory_order_relaxed) & kImmortalFlag) != 0; + } private: + // We reserve the bottom bits for flags. + // kImmortalBit indicates that this entity should never be collected; it is + // used for the StringConstant constructor to avoid collecting immutable + // constant cords. + // kReservedFlag is reserved for future use. + enum { + kNumFlags = 2, + + kImmortalFlag = 0x1, + kCrcFlag = 0x2, + kRefIncrement = (1 << kNumFlags), + + // Bitmask to use when checking refcount by equality. This masks out + // all flags except kImmortalFlag, which is part of the refcount for + // purposes of equality. (A refcount of 0 or 1 does not count as 0 or 1 + // if the immortal bit is set.) + kRefcountMask = ~kCrcFlag, + }; + std::atomic<int32_t> count_; }; @@ -80,34 +189,106 @@ class Refcount { // functions in the base class. struct CordRepConcat; -struct CordRepSubstring; struct CordRepExternal; +struct CordRepFlat; +struct CordRepSubstring; +class CordRepRing; +class CordRepBtree; + +// Various representations that we allow +enum CordRepKind { + CONCAT = 0, + SUBSTRING = 1, + BTREE = 2, + RING = 3, + EXTERNAL = 4, + + // We have different tags for different sized flat arrays, + // starting with FLAT, and limited to MAX_FLAT_TAG. The 225 value is based on + // the current 'size to tag' encoding of 8 / 32 bytes. If a new tag is needed + // in the future, then 'FLAT' and 'MAX_FLAT_TAG' should be adjusted as well + // as the Tag <---> Size logic so that FLAT stil represents the minimum flat + // allocation size. (32 bytes as of now). + FLAT = 5, + MAX_FLAT_TAG = 225 +}; + +// There are various locations where we want to check if some rep is a 'plain' +// data edge, i.e. an external or flat rep. By having FLAT == EXTERNAL + 1, we +// can perform this check in a single branch as 'tag >= EXTERNAL' +// Likewise, we have some locations where we check for 'ring or external/flat', +// so likewise align RING to EXTERNAL. +// Note that we can leave this optimization to the compiler. The compiler will +// DTRT when it sees a condition like `tag == EXTERNAL || tag >= FLAT`. +static_assert(RING == BTREE + 1, "BTREE and RING not consecutive"); +static_assert(EXTERNAL == RING + 1, "BTREE and EXTERNAL not consecutive"); +static_assert(FLAT == EXTERNAL + 1, "EXTERNAL and FLAT not consecutive"); struct CordRep { + CordRep() = default; + constexpr CordRep(RefcountAndFlags::Immortal immortal, size_t l) + : length(l), refcount(immortal), tag(EXTERNAL), storage{} {} + // The following three fields have to be less than 32 bytes since // that is the smallest supported flat node size. - // We use uint64_t for the length even in 32-bit binaries. - uint64_t length; - Refcount refcount; + size_t length; + RefcountAndFlags refcount; // If tag < FLAT, it represents CordRepKind and indicates the type of node. // Otherwise, the node type is CordRepFlat and the tag is the encoded size. uint8_t tag; - char data[1]; // Starting point for flat array: MUST BE LAST FIELD of CordRep + // `storage` provides two main purposes: + // - the starting point for FlatCordRep.Data() [flexible-array-member] + // - 3 bytes of additional storage for use by derived classes. + // The latter is used by CordrepConcat and CordRepBtree. CordRepConcat stores + // a 'depth' value in storage[0], and the (future) CordRepBtree class stores + // `height`, `begin` and `end` in the 3 entries. Otherwise we would need to + // allocate room for these in the derived class, as not all compilers reuse + // padding space from the base class (clang and gcc do, MSVC does not, etc) + uint8_t storage[3]; + + // Returns true if this instance's tag matches the requested type. + constexpr bool IsRing() const { return tag == RING; } + constexpr bool IsConcat() const { return tag == CONCAT; } + constexpr bool IsSubstring() const { return tag == SUBSTRING; } + constexpr bool IsExternal() const { return tag == EXTERNAL; } + constexpr bool IsFlat() const { return tag >= FLAT; } + constexpr bool IsBtree() const { return tag == BTREE; } + + inline CordRepRing* ring(); + inline const CordRepRing* ring() const; inline CordRepConcat* concat(); inline const CordRepConcat* concat() const; inline CordRepSubstring* substring(); inline const CordRepSubstring* substring() const; inline CordRepExternal* external(); inline const CordRepExternal* external() const; + inline CordRepFlat* flat(); + inline const CordRepFlat* flat() const; + inline CordRepBtree* btree(); + inline const CordRepBtree* btree() const; + + // -------------------------------------------------------------------- + // Memory management + + // Destroys the provided `rep`. + static void Destroy(CordRep* rep); + + // Increments the reference count of `rep`. + // Requires `rep` to be a non-null pointer value. + static inline CordRep* Ref(CordRep* rep); + + // Decrements the reference count of `rep`. Destroys rep if count reaches + // zero. Requires `rep` to be a non-null pointer value. + static inline void Unref(CordRep* rep); }; struct CordRepConcat : public CordRep { CordRep* left; CordRep* right; - uint8_t depth() const { return static_cast<uint8_t>(data[0]); } - void set_depth(uint8_t depth) { data[0] = static_cast<char>(depth); } + uint8_t depth() const { return storage[0]; } + void set_depth(uint8_t depth) { storage[0] = depth; } }; struct CordRepSubstring : public CordRep { @@ -115,37 +296,325 @@ struct CordRepSubstring : public CordRep { CordRep* child; }; -// TODO(strel): replace the following logic (and related functions in cord.cc) -// with container_internal::Layout. - -// Alignment requirement for CordRepExternal so that the type erased releaser -// will be stored at a suitably aligned address. -constexpr size_t ExternalRepAlignment() { -#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__) - return __STDCPP_DEFAULT_NEW_ALIGNMENT__; -#else - return alignof(max_align_t); -#endif -} - -// Type for function pointer that will invoke and destroy the type-erased -// releaser function object. Accepts a pointer to the releaser and the -// `string_view` that were passed in to `NewExternalRep` below. The return value -// is the size of the `Releaser` type. -using ExternalReleaserInvoker = size_t (*)(void*, absl::string_view); +// Type for function pointer that will invoke the releaser function and also +// delete the `CordRepExternalImpl` corresponding to the passed in +// `CordRepExternal`. +using ExternalReleaserInvoker = void (*)(CordRepExternal*); // External CordReps are allocated together with a type erased releaser. The // releaser is stored in the memory directly following the CordRepExternal. -struct alignas(ExternalRepAlignment()) CordRepExternal : public CordRep { +struct CordRepExternal : public CordRep { + CordRepExternal() = default; + explicit constexpr CordRepExternal(absl::string_view str) + : CordRep(RefcountAndFlags::Immortal{}, str.size()), + base(str.data()), + releaser_invoker(nullptr) {} + const char* base; // Pointer to function that knows how to call and destroy the releaser. ExternalReleaserInvoker releaser_invoker; + + // Deletes (releases) the external rep. + // Requires rep != nullptr and rep->IsExternal() + static void Delete(CordRep* rep); +}; + +struct Rank1 {}; +struct Rank0 : Rank1 {}; + +template <typename Releaser, typename = ::absl::base_internal::invoke_result_t< + 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::invoke_result_t<Releaser>> +void InvokeReleaser(Rank1, Releaser&& releaser, absl::string_view) { + ::absl::base_internal::invoke(std::forward<Releaser>(releaser)); +} + +// We use CompressedTuple so that we can benefit from EBCO. +template <typename Releaser> +struct CordRepExternalImpl + : public CordRepExternal, + public ::absl::container_internal::CompressedTuple<Releaser> { + // The extra int arg is so that we can avoid interfering with copy/move + // constructors while still benefitting from perfect forwarding. + template <typename T> + CordRepExternalImpl(T&& releaser, int) + : CordRepExternalImpl::CompressedTuple(std::forward<T>(releaser)) { + this->releaser_invoker = &Release; + } + + ~CordRepExternalImpl() { + InvokeReleaser(Rank0{}, std::move(this->template get<0>()), + absl::string_view(base, length)); + } + + static void Release(CordRepExternal* rep) { + delete static_cast<CordRepExternalImpl*>(rep); + } +}; + +inline void CordRepExternal::Delete(CordRep* rep) { + assert(rep != nullptr && rep->IsExternal()); + auto* rep_external = static_cast<CordRepExternal*>(rep); + assert(rep_external->releaser_invoker != nullptr); + rep_external->releaser_invoker(rep_external); +} + +template <typename Str> +struct ConstInitExternalStorage { + ABSL_CONST_INIT static CordRepExternal value; }; -// TODO(strel): look into removing, it doesn't seem like anything relies on this -static_assert(sizeof(CordRepConcat) == sizeof(CordRepSubstring), ""); +template <typename Str> +CordRepExternal ConstInitExternalStorage<Str>::value(Str::value); + +enum { + kMaxInline = 15, +}; + +constexpr char GetOrNull(absl::string_view data, size_t pos) { + return pos < data.size() ? data[pos] : '\0'; +} + +// We store cordz_info as 64 bit pointer value in big endian format. This +// guarantees that the least significant byte of cordz_info matches the last +// byte of the inline data representation in as_chars_, which holds the inlined +// size or the 'is_tree' bit. +using cordz_info_t = int64_t; + +// Assert that the `cordz_info` pointer value perfectly overlaps the last half +// of `as_chars_` and can hold a pointer value. +static_assert(sizeof(cordz_info_t) * 2 == kMaxInline + 1, ""); +static_assert(sizeof(cordz_info_t) >= sizeof(intptr_t), ""); + +// BigEndianByte() creates a big endian representation of 'value', i.e.: a big +// endian value where the last byte in the host's representation holds 'value`, +// with all other bytes being 0. +static constexpr cordz_info_t BigEndianByte(unsigned char value) { +#if defined(ABSL_IS_BIG_ENDIAN) + return value; +#else + return static_cast<cordz_info_t>(value) << ((sizeof(cordz_info_t) - 1) * 8); +#endif +} + +class InlineData { + public: + // DefaultInitType forces the use of the default initialization constructor. + enum DefaultInitType { kDefaultInit }; + + // kNullCordzInfo holds the big endian representation of intptr_t(1) + // This is the 'null' / initial value of 'cordz_info'. The null value + // is specifically big endian 1 as with 64-bit pointers, the last + // byte of cordz_info overlaps with the last byte holding the tag. + static constexpr cordz_info_t kNullCordzInfo = BigEndianByte(1); + + constexpr InlineData() : as_chars_{0} {} + explicit InlineData(DefaultInitType) {} + explicit constexpr InlineData(CordRep* rep) : as_tree_(rep) {} + explicit constexpr InlineData(absl::string_view chars) + : as_chars_{ + GetOrNull(chars, 0), GetOrNull(chars, 1), + GetOrNull(chars, 2), GetOrNull(chars, 3), + GetOrNull(chars, 4), GetOrNull(chars, 5), + GetOrNull(chars, 6), GetOrNull(chars, 7), + GetOrNull(chars, 8), GetOrNull(chars, 9), + GetOrNull(chars, 10), GetOrNull(chars, 11), + GetOrNull(chars, 12), GetOrNull(chars, 13), + GetOrNull(chars, 14), static_cast<char>((chars.size() << 1))} {} + + // Returns true if the current instance is empty. + // The 'empty value' is an inlined data value of zero length. + bool is_empty() const { return tag() == 0; } + + // Returns true if the current instance holds a tree value. + bool is_tree() const { return (tag() & 1) != 0; } + + // Returns true if the current instance holds a cordz_info value. + // Requires the current instance to hold a tree value. + bool is_profiled() const { + assert(is_tree()); + return as_tree_.cordz_info != kNullCordzInfo; + } + + // Returns true if either of the provided instances hold a cordz_info value. + // This method is more efficient than the equivalent `data1.is_profiled() || + // data2.is_profiled()`. Requires both arguments to hold a tree. + static bool is_either_profiled(const InlineData& data1, + const InlineData& data2) { + assert(data1.is_tree() && data2.is_tree()); + return (data1.as_tree_.cordz_info | data2.as_tree_.cordz_info) != + kNullCordzInfo; + } + + // Returns the cordz_info sampling instance for this instance, or nullptr + // if the current instance is not sampled and does not have CordzInfo data. + // Requires the current instance to hold a tree value. + CordzInfo* cordz_info() const { + assert(is_tree()); + intptr_t info = + static_cast<intptr_t>(absl::big_endian::ToHost64(as_tree_.cordz_info)); + assert(info & 1); + return reinterpret_cast<CordzInfo*>(info - 1); + } + + // Sets the current cordz_info sampling instance for this instance, or nullptr + // if the current instance is not sampled and does not have CordzInfo data. + // Requires the current instance to hold a tree value. + void set_cordz_info(CordzInfo* cordz_info) { + assert(is_tree()); + intptr_t info = reinterpret_cast<intptr_t>(cordz_info) | 1; + as_tree_.cordz_info = absl::big_endian::FromHost64(info); + } + + // Resets the current cordz_info to null / empty. + void clear_cordz_info() { + assert(is_tree()); + as_tree_.cordz_info = kNullCordzInfo; + } + + // Returns a read only pointer to the character data inside this instance. + // Requires the current instance to hold inline data. + const char* as_chars() const { + assert(!is_tree()); + return as_chars_; + } + + // Returns a mutable pointer to the character data inside this instance. + // Should be used for 'write only' operations setting an inlined value. + // Applications can set the value of inlined data either before or after + // setting the inlined size, i.e., both of the below are valid: + // + // // Set inlined data and inline size + // memcpy(data_.as_chars(), data, size); + // data_.set_inline_size(size); + // + // // Set inlined size and inline data + // data_.set_inline_size(size); + // memcpy(data_.as_chars(), data, size); + // + // It's an error to read from the returned pointer without a preceding write + // if the current instance does not hold inline data, i.e.: is_tree() == true. + char* as_chars() { return as_chars_; } + + // Returns the tree value of this value. + // Requires the current instance to hold a tree value. + CordRep* as_tree() const { + assert(is_tree()); + return as_tree_.rep; + } + + // Initialize this instance to holding the tree value `rep`, + // initializing the cordz_info to null, i.e.: 'not profiled'. + void make_tree(CordRep* rep) { + as_tree_.rep = rep; + as_tree_.cordz_info = kNullCordzInfo; + } + + // Set the tree value of this instance to 'rep`. + // Requires the current instance to already hold a tree value. + // Does not affect the value of cordz_info. + void set_tree(CordRep* rep) { + assert(is_tree()); + as_tree_.rep = rep; + } + + // Returns the size of the inlined character data inside this instance. + // Requires the current instance to hold inline data. + size_t inline_size() const { + assert(!is_tree()); + return tag() >> 1; + } + + // Sets the size of the inlined character data inside this instance. + // Requires `size` to be <= kMaxInline. + // See the documentation on 'as_chars()' for more information and examples. + void set_inline_size(size_t size) { + ABSL_ASSERT(size <= kMaxInline); + tag() = static_cast<char>(size << 1); + } + + private: + // See cordz_info_t for forced alignment and size of `cordz_info` details. + struct AsTree { + explicit constexpr AsTree(absl::cord_internal::CordRep* tree) + : rep(tree), cordz_info(kNullCordzInfo) {} + // This union uses up extra space so that whether rep is 32 or 64 bits, + // cordz_info will still start at the eighth byte, and the last + // byte of cordz_info will still be the last byte of InlineData. + union { + absl::cord_internal::CordRep* rep; + cordz_info_t unused_aligner; + }; + cordz_info_t cordz_info; + }; + + char& tag() { return reinterpret_cast<char*>(this)[kMaxInline]; } + char tag() const { return reinterpret_cast<const char*>(this)[kMaxInline]; } + + // If the data has length <= kMaxInline, we store it in `as_chars_`, and + // store the size in the last char of `as_chars_` shifted left + 1. + // Else we store it in a tree and store a pointer to that tree in + // `as_tree_.rep` and store a tag in `tagged_size`. + union { + char as_chars_[kMaxInline + 1]; + AsTree as_tree_; + }; +}; + +static_assert(sizeof(InlineData) == kMaxInline + 1, ""); + +inline CordRepConcat* CordRep::concat() { + assert(IsConcat()); + return static_cast<CordRepConcat*>(this); +} + +inline const CordRepConcat* CordRep::concat() const { + assert(IsConcat()); + return static_cast<const CordRepConcat*>(this); +} + +inline CordRepSubstring* CordRep::substring() { + assert(IsSubstring()); + return static_cast<CordRepSubstring*>(this); +} + +inline const CordRepSubstring* CordRep::substring() const { + assert(IsSubstring()); + return static_cast<const CordRepSubstring*>(this); +} + +inline CordRepExternal* CordRep::external() { + assert(IsExternal()); + return static_cast<CordRepExternal*>(this); +} + +inline const CordRepExternal* CordRep::external() const { + assert(IsExternal()); + return static_cast<const CordRepExternal*>(this); +} + +inline CordRep* CordRep::Ref(CordRep* rep) { + assert(rep != nullptr); + rep->refcount.Increment(); + return rep; +} + +inline void CordRep::Unref(CordRep* rep) { + assert(rep != nullptr); + // Expect refcount to be 0. Avoiding the cost of an atomic decrement should + // typically outweigh the cost of an extra branch checking for ref == 1. + if (ABSL_PREDICT_FALSE(!rep->refcount.DecrementExpectHighRefcount())) { + Destroy(rep); + } +} } // namespace cord_internal + ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_STRINGS_INTERNAL_CORD_INTERNAL_H_ |