// Protocol Buffers - Google's data interchange format

// Copyright 2008 Google Inc.  All rights reserved.

//

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file or at

// https://developers.google.com/open-source/licenses/bsd

#ifndef GOOGLE_PROTOBUF_ARENASTRING_H__

#define GOOGLE_PROTOBUF_ARENASTRING_H__

#include <algorithm>

#include <cstdint>

#include <string>

#include <type_traits>

#include <utility>

#include "absl/log/absl_check.h"

#include "absl/strings/string_view.h"

#include "google/protobuf/arena.h"

#include "google/protobuf/explicitly_constructed.h"

#include "google/protobuf/port.h"

// must be last:

#include "google/protobuf/port_def.inc"

#ifdef SWIG

#error "You cannot SWIG proto headers"

#endif

namespace google {

namespace protobuf {

namespace internal {

class EpsCopyInputStream;

class SwapFieldHelper;

// Declared in message_lite.h

PROTOBUF_EXPORT extern ExplicitlyConstructedArenaString

    fixed_address_empty_string;

// Lazy string instance to support string fields with non-empty default.

// These are initialized on the first call to .get().

class PROTOBUF_EXPORT LazyString {

 public:

  // We explicitly make LazyString an aggregate so that MSVC can do constant

  // initialization on it without marking it `constexpr`.

  // We do not want to use `constexpr` because it makes it harder to have extern

  // storage for it and causes library bloat.

  struct InitValue {

    const char* ptr;

    size_t size;

  };

  // We keep a union of the initialization value and the std::string to save on

  // space. We don't need the string array after Init() is done.

  union {

    mutable InitValue init_value_;

    alignas(std::string) mutable char string_buf_[sizeof(std::string)];

  };

  mutable std::atomic<const std::string*> inited_;

  const std::string& get() const {

    // This check generates less code than a call-once invocation.

    auto* res = inited_.load(std::memory_order_acquire);

    if (PROTOBUF_PREDICT_FALSE(res == nullptr)) return Init();

    return *res;

  }

 private:

  // Initialize the string in `string_buf_`, update `inited_` and return it.

  // We return it here to avoid having to read it again in the inlined code.

  const std::string& Init() const;

};

class PROTOBUF_EXPORT TaggedStringPtr {

 public:

  // Bit flags qualifying string properties. We can use 2 bits as

  // ptr_ is guaranteed and enforced to be aligned on 4 byte boundaries.

  enum Flags {

    kArenaBit = 0x1,    // ptr is arena allocated

    kMutableBit = 0x2,  // ptr contents are fully mutable

    kMask = 0x3         // Bit mask

  };

  // Composed logical types

  enum Type {

    // Default strings are immutable and never owned.

    kDefault = 0,

    // Allocated strings are mutable and (as the name implies) owned.

    // A heap allocated string must be deleted.

    kAllocated = kMutableBit,

    // Mutable arena strings are strings where the string instance is owned

    // by the arena, but the string contents itself are owned by the string

    // instance. Mutable arena string instances need to be destroyed which is

    // typically done through a cleanup action added to the arena owning it.

    kMutableArena = kArenaBit | kMutableBit,

    // Fixed size arena strings are strings where both the string instance and

    // the string contents are fully owned by the arena. Fixed size arena

    // strings are a platform and c++ library specific customization. Fixed

    // size arena strings are immutable, with the exception of custom internal

    // updates to the content that fit inside the existing capacity.

    // Fixed size arena strings must never be deleted or destroyed.

    kFixedSizeArena = kArenaBit,

  };

  TaggedStringPtr() = default;

  explicit constexpr TaggedStringPtr(ExplicitlyConstructedArenaString* ptr)

      : ptr_(ptr) {}

  // Sets the value to `p`, tagging the value as being a 'default' value.

  // See documentation for kDefault for more info.

  inline const std::string* SetDefault(const std::string* p) {

    return TagAs(kDefault, const_cast<std::string*>(p));

  }

  // Sets the value to `p`, tagging the value as a heap allocated value.

  // Allocated strings are mutable and (as the name implies) owned.

  // `p` must not be null

  inline std::string* SetAllocated(std::string* p) {

    return TagAs(kAllocated, p);

  }

  // Sets the value to `p`, tagging the value as a fixed size arena string.

  // See documentation for kFixedSizeArena for more info.

  // `p` must not be null

  inline std::string* SetFixedSizeArena(std::string* p) {

    return TagAs(kFixedSizeArena, p);

  }

  // Sets the value to `p`, tagging the value as a mutable arena string.

  // See documentation for kMutableArena for more info.

  // `p` must not be null

  inline std::string* SetMutableArena(std::string* p) {

    return TagAs(kMutableArena, p);

  }

  // Returns true if the contents of the current string are fully mutable.

  inline bool IsMutable() const { return as_int() & kMutableBit; }

  // Returns true if the current string is an immutable default value.

  inline bool IsDefault() const { return (as_int() & kMask) == kDefault; }

  // If the current string is a heap-allocated mutable value, returns a pointer

  // to it.  Returns nullptr otherwise.

  inline std::string* GetIfAllocated() const {

    auto allocated = as_int() ^ kAllocated;

    if (allocated & kMask) return nullptr;

    auto ptr = reinterpret_cast<std::string*>(allocated);

    PROTOBUF_ASSUME(ptr != nullptr);

    return ptr;

  }

  // Returns true if the current string is an arena allocated value.

  // This means it's either a mutable or fixed size arena string.

  inline bool IsArena() const { return as_int() & kArenaBit; }

  // Returns true if the current string is a fixed size arena allocated value.

  inline bool IsFixedSizeArena() const {

    return (as_int() & kMask) == kFixedSizeArena;

  }

  // Returns the contained string pointer.

  inline std::string* Get() const {

    return reinterpret_cast<std::string*>(as_int() & ~kMask);

  }

  // Returns true if the contained pointer is null, indicating some error.

  // The Null value is only used during parsing for temporary values.

  // A persisted ArenaStringPtr value is never null.

  inline bool IsNull() const { return ptr_ == nullptr; }

  // Returns a copy of this instance. In debug builds, the returned value may be

  // a forced copy regardless if the current instance is a compile time default.

  TaggedStringPtr Copy(Arena* arena) const;

  // Identical to the above `Copy` function except that in debug builds,

  // `default_value` can be used to substitute an empty default with a

  // hardened copy of the default value.

  TaggedStringPtr Copy(Arena* arena, const LazyString& default_value) const;

 private:

  static inline void assert_aligned(const void* p) {

    static_assert(kMask <= alignof(void*), "Pointer underaligned for bit mask");

    static_assert(kMask <= alignof(std::string),

                  "std::string underaligned for bit mask");

    ABSL_DCHECK_EQ(reinterpret_cast<uintptr_t>(p) & kMask, 0UL);

  }

  // Creates a heap or arena allocated copy of this instance.

  TaggedStringPtr ForceCopy(Arena* arena) const;

  inline std::string* TagAs(Type type, std::string* p) {

    ABSL_DCHECK(p != nullptr);

    assert_aligned(p);

    ptr_ = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(p) | type);

    return p;

  }

  uintptr_t as_int() const { return reinterpret_cast<uintptr_t>(ptr_); }

  void* ptr_;

};

static_assert(std::is_trivial<TaggedStringPtr>::value,

              "TaggedStringPtr must be trivial");

// This class encapsulates a pointer to a std::string with or without arena

// owned contents, tagged by the bottom bits of the string pointer. It is a

// high-level wrapper that almost directly corresponds to the interface required

// by string fields in generated code. It replaces the old std::string* pointer

// in such cases.

//

// The string pointer is tagged to be either a default, externally owned value,

// a mutable heap allocated value, or an arena allocated value. The object uses

// a single global instance of an empty string that is used as the initial

// default value. Fields that have empty default values directly use this global

// default. Fields that have non empty default values are supported through

// lazily initialized default values managed by the LazyString class.

//

// Generated code and reflection code both ensure that ptr_ is never null.

// Because ArenaStringPtr is used in oneof unions, its constructor is a NOP and

// the field is always manually initialized via method calls.

//

// See TaggedStringPtr for more information about the types of string values

// being held, and the mutable and ownership invariants for each type.

struct PROTOBUF_EXPORT ArenaStringPtr {

  // Default constructor, leaves current instance uninitialized (does nothing)

  ArenaStringPtr() = default;

  // Constexpr constructor, initializes to a constexpr, empty string value.

  constexpr ArenaStringPtr(ExplicitlyConstructedArenaString* default_value,

                           ConstantInitialized)

      : tagged_ptr_(default_value) {}

  // Arena enabled constructor for strings without a default value.

  // Initializes this instance to a constexpr, empty string value, unless debug

  // hardening is enabled, in which case this instance will hold a forced copy.

  explicit ArenaStringPtr(Arena* arena)

      : tagged_ptr_(&fixed_address_empty_string) {

    if (DebugHardenForceCopyDefaultString()) {

      Set(absl::string_view(""), arena);

    }

  }

  // Arena enabled constructor for strings with a non-empty default value.

  // Initializes this instance to a constexpr, empty string value, unless debug

  // hardening is enabled, in which case this instance will be forced to hold a

  // forced copy of the value in `default_value`.

  ArenaStringPtr(Arena* arena, const LazyString& default_value)

      : tagged_ptr_(&fixed_address_empty_string) {

    if (DebugHardenForceCopyDefaultString()) {

      Set(absl::string_view(default_value.get()), arena);

    }

  }

  // Arena enabled copy constructor for strings without a default value.

  // This instance will be initialized with a copy of the value in `rhs`.

  // If `rhs` holds a default (empty) value, then this instance will also be

  // initialized with the default empty value, unless debug hardening is

  // enabled, in which case this instance will be forced to hold a copy of

  // an empty default value.

  ArenaStringPtr(Arena* arena, const ArenaStringPtr& rhs)

      : tagged_ptr_(rhs.tagged_ptr_.Copy(arena)) {}

  // Arena enabled copy constructor for strings with a non-empty default value.

  // This instance will be initialized with a copy of the value in `rhs`.

  // If `rhs` holds a default (empty) value, then this instance will also be

  // initialized with the default empty value, unless debug hardening is

  // enabled, in which case this instance will be forced to hold forced copy

  // of the value in `default_value`.

  ArenaStringPtr(Arena* arena, const ArenaStringPtr& rhs,

                 const LazyString& default_value)

      : tagged_ptr_(rhs.tagged_ptr_.Copy(arena, default_value)) {}

  // Called from generated code / reflection runtime only. Resets value to point

  // to a default string pointer, with the semantics that this ArenaStringPtr

  // does not own the pointed-to memory. Disregards initial value of ptr_ (so

  // this is the *ONLY* safe method to call after construction or when

  // reinitializing after becoming the active field in a oneof union).

  inline void InitDefault();

  // Similar to `InitDefault` except that it allows the default value to be

  // initialized to an externally owned string. This method is called from

  // parsing code. `str` must not be null and outlive this instance.

  inline void InitExternal(const std::string* str);

  // Called from generated code / reflection runtime only. Resets the value of

  // this instances to the heap allocated value in `str`. `str` must not be

  // null. Invokes `arena->Own(str)` to transfer ownership into the arena if

  // `arena` is not null, else, `str` will be owned by ArenaStringPtr. This

  // function should only be used to initialize a ArenaStringPtr or on an

  // instance known to not carry any heap allocated value.

  inline void InitAllocated(std::string* str, Arena* arena);

  void Set(absl::string_view value, Arena* arena);

  void Set(std::string&& value, Arena* arena);

  template <typename... OverloadDisambiguator>

  void Set(const std::string& value, Arena* arena);

  void Set(const char* s, Arena* arena);

  void Set(const char* s, size_t n, Arena* arena);

  void SetBytes(absl::string_view value, Arena* arena);

  void SetBytes(std::string&& value, Arena* arena);

  template <typename... OverloadDisambiguator>

  void SetBytes(const std::string& value, Arena* arena);

  void SetBytes(const char* s, Arena* arena);

  void SetBytes(const void* p, size_t n, Arena* arena);

  template <typename RefWrappedType>

  void Set(std::reference_wrapper<RefWrappedType> const_string_ref,

           ::google::protobuf::Arena* arena) {

    Set(const_string_ref.get(), arena);

  }

  // Returns a mutable std::string reference.

  // The version accepting a `LazyString` value is used in the generated code to

  // initialize mutable copies for fields with a non-empty default where the

  // default value is lazily initialized.

  std::string* Mutable(Arena* arena);

  std::string* Mutable(const LazyString& default_value, Arena* arena);

  // Gets a mutable pointer with unspecified contents.

  // This function is identical to Mutable(), except it is optimized for the

  // case where the caller is not interested in the current contents. For

  // example, if the current field is not mutable, it will re-initialize the

  // value with an empty string rather than a (non-empty) default value.

  // Likewise, if the current value is a fixed size arena string with contents,

  // it will be initialized into an empty mutable arena string.

  std::string* MutableNoCopy(Arena* arena);

  // Basic accessors.

  PROTOBUF_NDEBUG_INLINE const std::string& Get() const {

    // Unconditionally mask away the tag.

    return *tagged_ptr_.Get();

  }

  // Returns a pointer to the stored contents for this instance.

  // This method is for internal debugging and tracking purposes only.

  PROTOBUF_NDEBUG_INLINE const std::string* UnsafeGetPointer() const

      ABSL_ATTRIBUTE_RETURNS_NONNULL {

    return tagged_ptr_.Get();

  }

  // Release returns a std::string* instance that is heap-allocated and is not

  // Own()'d by any arena. If the field is not set, this returns nullptr. The

  // caller retains ownership. Clears this field back to the default state.

  // Used to implement release_<field>() methods on generated classes.

  PROTOBUF_NODISCARD std::string* Release();

  // Takes a std::string that is heap-allocated, and takes ownership. The

  // std::string's destructor is registered with the arena. Used to implement

  // set_allocated_<field> in generated classes.

  void SetAllocated(std::string* value, Arena* arena);

  // Frees storage (if not on an arena).

  void Destroy();

  // Clears content, but keeps allocated std::string, to avoid the overhead of

  // heap operations. After this returns, the content (as seen by the user) will

  // always be the empty std::string. Assumes that |default_value| is an empty

  // std::string.

  void ClearToEmpty();

  // Clears content, assuming that the current value is not the empty

  // string default.

  void ClearNonDefaultToEmpty();

  // Clears content, but keeps allocated std::string if arena != nullptr, to

  // avoid the overhead of heap operations. After this returns, the content

  // (as seen by the user) will always be equal to |default_value|.

  void ClearToDefault(const LazyString& default_value, ::google::protobuf::Arena* arena);

  // Swaps internal pointers. Arena-safety semantics: this is guarded by the

  // logic in Swap()/UnsafeArenaSwap() at the message level, so this method is

  // 'unsafe' if called directly.

  inline PROTOBUF_NDEBUG_INLINE static void InternalSwap(ArenaStringPtr* rhs,

                                                         ArenaStringPtr* lhs,

                                                         Arena* arena);

  // Internal setter used only at parse time to directly set a donated string

  // value.

  void UnsafeSetTaggedPointer(TaggedStringPtr value) { tagged_ptr_ = value; }

  // Generated code only! An optimization, in certain cases the generated

  // code is certain we can obtain a std::string with no default checks and

  // tag tests.

  std::string* UnsafeMutablePointer() ABSL_ATTRIBUTE_RETURNS_NONNULL;

  // Returns true if this instances holds an immutable default value.

  inline bool IsDefault() const { return tagged_ptr_.IsDefault(); }

 private:

  template <typename... Args>

  inline std::string* NewString(Arena* arena, Args&&... args) {

    if (arena == nullptr) {

      auto* s = new std::string(std::forward<Args>(args)...);

      return tagged_ptr_.SetAllocated(s);

    } else {

      auto* s = Arena::Create<std::string>(arena, std::forward<Args>(args)...);

      return tagged_ptr_.SetMutableArena(s);

    }

  }

  TaggedStringPtr tagged_ptr_;

  bool IsFixedSizeArena() const { return false; }

  // Swaps tagged pointer without debug hardening. This is to allow python

  // protobuf to maintain pointer stability even in DEBUG builds.

  inline PROTOBUF_NDEBUG_INLINE static void UnsafeShallowSwap(

      ArenaStringPtr* rhs, ArenaStringPtr* lhs) {

    std::swap(lhs->tagged_ptr_, rhs->tagged_ptr_);

  }

  friend class ::google::protobuf::internal::SwapFieldHelper;

  friend class TcParser;

  // Slow paths.

  // MutableSlow requires that !IsString() || IsDefault

  // Variadic to support 0 args for empty default and 1 arg for LazyString.

  template <typename... Lazy>

  std::string* MutableSlow(::google::protobuf::Arena* arena, const Lazy&... lazy_default);

  friend class EpsCopyInputStream;

};

inline TaggedStringPtr TaggedStringPtr::Copy(Arena* arena) const {

  if (DebugHardenForceCopyDefaultString()) {

    // Harden by forcing an allocated string value.

    return IsNull() ? *this : ForceCopy(arena);

  }

  return IsDefault() ? *this : ForceCopy(arena);

}

inline TaggedStringPtr TaggedStringPtr::Copy(

    Arena* arena, const LazyString& default_value) const {

  if (DebugHardenForceCopyDefaultString()) {

    // Harden by forcing an allocated string value.

    TaggedStringPtr hardened(*this);

    if (IsDefault()) {

      hardened.SetDefault(&default_value.get());

    }

    return hardened.ForceCopy(arena);

  }

  return IsDefault() ? *this : ForceCopy(arena);

}

inline void ArenaStringPtr::InitDefault() {

  tagged_ptr_ = TaggedStringPtr(&fixed_address_empty_string);

}

inline void ArenaStringPtr::InitExternal(const std::string* str) {

  tagged_ptr_.SetDefault(str);

}

inline void ArenaStringPtr::InitAllocated(std::string* str, Arena* arena) {

  if (arena != nullptr) {

    tagged_ptr_.SetMutableArena(str);

    arena->Own(str);

  } else {

    tagged_ptr_.SetAllocated(str);

  }

}

inline void ArenaStringPtr::Set(const char* s, Arena* arena) {

  Set(absl::string_view{s}, arena);

}

inline void ArenaStringPtr::Set(const char* s, size_t n, Arena* arena) {

  Set(absl::string_view{s, n}, arena);

}

inline void ArenaStringPtr::SetBytes(absl::string_view value, Arena* arena) {

  Set(value, arena);

}

template <>

PROTOBUF_EXPORT void ArenaStringPtr::Set(const std::string& value,

                                         Arena* arena);

template <>

inline void ArenaStringPtr::SetBytes(const std::string& value, Arena* arena) {

  Set(value, arena);

}

inline void ArenaStringPtr::SetBytes(std::string&& value, Arena* arena) {

  Set(std::move(value), arena);

}

inline void ArenaStringPtr::SetBytes(const char* s, Arena* arena) {

  Set(s, arena);

}

inline void ArenaStringPtr::SetBytes(const void* p, size_t n, Arena* arena) {

  Set(absl::string_view{static_cast<const char*>(p), n}, arena);

}

inline PROTOBUF_NDEBUG_INLINE void ArenaStringPtr::InternalSwap(

    ArenaStringPtr* rhs, ArenaStringPtr* lhs, Arena* arena) {

  // Silence unused variable warnings in release buildls.

  (void)arena;

  std::swap(lhs->tagged_ptr_, rhs->tagged_ptr_);

  if (internal::DebugHardenForceCopyInSwap()) {

    for (auto* p : {lhs, rhs}) {

      if (p->IsDefault()) continue;

      std::string* old_value = p->tagged_ptr_.Get();

      std::string* new_value =

          p->IsFixedSizeArena()

              ? Arena::Create<std::string>(arena, *old_value)

              : Arena::Create<std::string>(arena, std::move(*old_value));

      if (arena == nullptr) {

        delete old_value;

        p->tagged_ptr_.SetAllocated(new_value);

      } else {

        p->tagged_ptr_.SetMutableArena(new_value);

      }

    }

  }

}

inline void ArenaStringPtr::ClearNonDefaultToEmpty() {

  // Unconditionally mask away the tag.

  tagged_ptr_.Get()->clear();

}

inline std::string* ArenaStringPtr::UnsafeMutablePointer() {

  ABSL_DCHECK(tagged_ptr_.IsMutable());

  ABSL_DCHECK(tagged_ptr_.Get() != nullptr);

  return tagged_ptr_.Get();

}

}  // namespace internal

}  // namespace protobuf

}  // namespace google

#include "google/protobuf/port_undef.inc"

#endif  // GOOGLE_PROTOBUF_ARENASTRING_H__