libcxx/include/shared_mutex

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_SHARED_MUTEX
#define _LIBCPP_SHARED_MUTEX

/*
    shared_mutex synopsis

// C++1y

namespace std
{

class shared_mutex      // C++17
{
public:
    shared_mutex();
    ~shared_mutex();

    shared_mutex(const shared_mutex&) = delete;
    shared_mutex& operator=(const shared_mutex&) = delete;

    // Exclusive ownership
    void lock(); // blocking
    bool try_lock();
    void unlock();

    // Shared ownership
    void lock_shared(); // blocking
    bool try_lock_shared();
    void unlock_shared();

    typedef implementation-defined native_handle_type; // See 30.2.3
    native_handle_type native_handle(); // See 30.2.3
};

class shared_timed_mutex
{
public:
    shared_timed_mutex();
    ~shared_timed_mutex();

    shared_timed_mutex(const shared_timed_mutex&) = delete;
    shared_timed_mutex& operator=(const shared_timed_mutex&) = delete;

    // Exclusive ownership
    void lock(); // blocking
    bool try_lock();
    template <class Rep, class Period>
        bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
    template <class Clock, class Duration>
        bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
    void unlock();

    // Shared ownership
    void lock_shared(); // blocking
    bool try_lock_shared();
    template <class Rep, class Period>
        bool
        try_lock_shared_for(const chrono::duration<Rep, Period>& rel_time);
    template <class Clock, class Duration>
        bool
        try_lock_shared_until(const chrono::time_point<Clock, Duration>& abs_time);
    void unlock_shared();
};

template <class Mutex>
class shared_lock
{
public:
    typedef Mutex mutex_type;

    // Shared locking
    shared_lock() noexcept;
    explicit shared_lock(mutex_type& m); // blocking
    shared_lock(mutex_type& m, defer_lock_t) noexcept;
    shared_lock(mutex_type& m, try_to_lock_t);
    shared_lock(mutex_type& m, adopt_lock_t);
    template <class Clock, class Duration>
        shared_lock(mutex_type& m,
                    const chrono::time_point<Clock, Duration>& abs_time);
    template <class Rep, class Period>
        shared_lock(mutex_type& m,
                    const chrono::duration<Rep, Period>& rel_time);
    ~shared_lock();

    shared_lock(shared_lock const&) = delete;
    shared_lock& operator=(shared_lock const&) = delete;

    shared_lock(shared_lock&& u) noexcept;
    shared_lock& operator=(shared_lock&& u) noexcept;

    void lock(); // blocking
    bool try_lock();
    template <class Rep, class Period>
        bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
    template <class Clock, class Duration>
        bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
    void unlock();

    // Setters
    void swap(shared_lock& u) noexcept;
    mutex_type* release() noexcept;

    // Getters
    bool owns_lock() const noexcept;
    explicit operator bool () const noexcept;
    mutex_type* mutex() const noexcept;
};

template <class Mutex>
    void swap(shared_lock<Mutex>& x, shared_lock<Mutex>& y) noexcept;

}  // std

*/

#if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
#  include <__cxx03/__config>
#else
#  include <__config>

#  if _LIBCPP_HAS_THREADS

#    include <__chrono/duration.h>
#    include <__chrono/steady_clock.h>
#    include <__chrono/time_point.h>
#    include <__condition_variable/condition_variable.h>
#    include <__memory/addressof.h>
#    include <__mutex/mutex.h>
#    include <__mutex/tag_types.h>
#    include <__mutex/unique_lock.h>
#    include <__system_error/throw_system_error.h>
#    include <__utility/move.h>
#    include <__utility/swap.h>
#    include <cerrno>
#    include <version>

_LIBCPP_PUSH_MACROS
#    include <__undef_macros>

#    if _LIBCPP_STD_VER >= 14

#      if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#        pragma GCC system_header
#      endif

_LIBCPP_BEGIN_NAMESPACE_STD
_LIBCPP_BEGIN_EXPLICIT_ABI_ANNOTATIONS

struct _LIBCPP_EXPORTED_FROM_ABI __shared_mutex_base {
  mutex __mut_;
  condition_variable __gate1_;
  condition_variable __gate2_;
  unsigned __state_;

  static const unsigned __write_entered_ = 1U << (sizeof(unsigned) * __CHAR_BIT__ - 1);
  static const unsigned __n_readers_     = ~__write_entered_;

  __shared_mutex_base();
  _LIBCPP_HIDE_FROM_ABI ~__shared_mutex_base() = default;

  __shared_mutex_base(const __shared_mutex_base&)            = delete;
  __shared_mutex_base& operator=(const __shared_mutex_base&) = delete;

  // Exclusive ownership
  void lock(); // blocking
  bool try_lock();
  void unlock();

  // Shared ownership
  void lock_shared(); // blocking
  bool try_lock_shared();
  void unlock_shared();

  //     typedef implementation-defined native_handle_type; // See 30.2.3
  //     native_handle_type native_handle(); // See 30.2.3
};

#      if _LIBCPP_STD_VER >= 17
class _LIBCPP_EXPORTED_FROM_ABI _LIBCPP_CAPABILITY("shared_mutex") _LIBCPP_WARN_UNUSED shared_mutex {
  __shared_mutex_base __base_;

public:
  _LIBCPP_HIDE_FROM_ABI shared_mutex() : __base_() {}
  _LIBCPP_HIDE_FROM_ABI ~shared_mutex() = default;

  shared_mutex(const shared_mutex&)            = delete;
  shared_mutex& operator=(const shared_mutex&) = delete;

  // Exclusive ownership
  _LIBCPP_ACQUIRE_CAPABILITY() _LIBCPP_HIDE_FROM_ABI void lock() { return __base_.lock(); }
  [[nodiscard]] _LIBCPP_TRY_ACQUIRE_CAPABILITY(true) _LIBCPP_HIDE_FROM_ABI bool try_lock() {
    return __base_.try_lock();
  }
  _LIBCPP_RELEASE_CAPABILITY() _LIBCPP_HIDE_FROM_ABI void unlock() { return __base_.unlock(); }

  // Shared ownership
  _LIBCPP_ACQUIRE_SHARED_CAPABILITY _LIBCPP_HIDE_FROM_ABI void lock_shared() { return __base_.lock_shared(); }
  [[nodiscard]] _LIBCPP_TRY_ACQUIRE_SHARED_CAPABILITY(true) _LIBCPP_HIDE_FROM_ABI bool try_lock_shared() {
    return __base_.try_lock_shared();
  }
  _LIBCPP_RELEASE_SHARED_CAPABILITY _LIBCPP_HIDE_FROM_ABI void unlock_shared() { return __base_.unlock_shared(); }

  //     typedef __shared_mutex_base::native_handle_type native_handle_type;
  //     _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() { return __base::unlock_shared(); }
};
#      endif

class _LIBCPP_EXPORTED_FROM_ABI _LIBCPP_CAPABILITY("shared_timed_mutex") _LIBCPP_WARN_UNUSED shared_timed_mutex {
  __shared_mutex_base __base_;

public:
  shared_timed_mutex();
  _LIBCPP_HIDE_FROM_ABI ~shared_timed_mutex() = default;

  shared_timed_mutex(const shared_timed_mutex&)            = delete;
  shared_timed_mutex& operator=(const shared_timed_mutex&) = delete;

  // Exclusive ownership
  void lock() _LIBCPP_ACQUIRE_CAPABILITY();
  [[__nodiscard__]] _LIBCPP_TRY_ACQUIRE_CAPABILITY(true) bool try_lock();
  template <class _Rep, class _Period>
  [[__nodiscard__]] _LIBCPP_TRY_ACQUIRE_CAPABILITY(true) _LIBCPP_HIDE_FROM_ABI bool
  try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time) {
    return try_lock_until(chrono::steady_clock::now() + __rel_time);
  }

  template <class _Clock, class _Duration>
  [[__nodiscard__]] _LIBCPP_TRY_ACQUIRE_CAPABILITY(true) _LIBCPP_HIDE_FROM_ABI bool
  try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time) {
    unique_lock<mutex> __lk(__base_.__mut_);
    if (__base_.__state_ & __base_.__write_entered_) {
      while (true) {
        cv_status __status = __base_.__gate1_.wait_until(__lk, __abs_time);
        if ((__base_.__state_ & __base_.__write_entered_) == 0)
          break;
        if (__status == cv_status::timeout)
          return false;
      }
    }
    __base_.__state_ |= __base_.__write_entered_;
    if (__base_.__state_ & __base_.__n_readers_) {
      while (true) {
        cv_status __status = __base_.__gate2_.wait_until(__lk, __abs_time);
        if ((__base_.__state_ & __base_.__n_readers_) == 0)
          break;
        if (__status == cv_status::timeout) {
          __base_.__state_ &= ~__base_.__write_entered_;
          __base_.__gate1_.notify_all();
          return false;
        }
      }
    }
    return true;
  }

  _LIBCPP_RELEASE_CAPABILITY() void unlock();

  // Shared ownership
  _LIBCPP_ACQUIRE_SHARED_CAPABILITY void lock_shared();
  [[__nodiscard__]] _LIBCPP_TRY_ACQUIRE_SHARED_CAPABILITY(true) bool try_lock_shared();
  template <class _Rep, class _Period>
  [[__nodiscard__]] _LIBCPP_TRY_ACQUIRE_SHARED_CAPABILITY(true) _LIBCPP_HIDE_FROM_ABI bool
  try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rel_time) {
    return try_lock_shared_until(chrono::steady_clock::now() + __rel_time);
  }

  template <class _Clock, class _Duration>
  [[__nodiscard__]] _LIBCPP_TRY_ACQUIRE_SHARED_CAPABILITY(true) _LIBCPP_HIDE_FROM_ABI bool
  try_lock_shared_until(const chrono::time_point<_Clock, _Duration>& __abs_time) {
    unique_lock<mutex> __lk(__base_.__mut_);
    if ((__base_.__state_ & __base_.__write_entered_) ||
        (__base_.__state_ & __base_.__n_readers_) == __base_.__n_readers_) {
      while (true) {
        cv_status __status = __base_.__gate1_.wait_until(__lk, __abs_time);
        if ((__base_.__state_ & __base_.__write_entered_) == 0 &&
            (__base_.__state_ & __base_.__n_readers_) < __base_.__n_readers_)
          break;
        if (__status == cv_status::timeout)
          return false;
      }
    }
    unsigned __num_readers = (__base_.__state_ & __base_.__n_readers_) + 1;
    __base_.__state_ &= ~__base_.__n_readers_;
    __base_.__state_ |= __num_readers;
    return true;
  }

  _LIBCPP_RELEASE_SHARED_CAPABILITY void unlock_shared();
};

template <class _Mutex>
class shared_lock {
public:
  typedef _Mutex mutex_type;

private:
  mutex_type* __m_;
  bool __owns_;

public:
  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI shared_lock() noexcept : __m_(nullptr), __owns_(false) {}

  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI explicit shared_lock(mutex_type& __m)
      : __m_(std::addressof(__m)), __owns_(true) {
    __m_->lock_shared();
  }

  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI shared_lock(mutex_type& __m, defer_lock_t) noexcept
      : __m_(std::addressof(__m)), __owns_(false) {}

  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI shared_lock(mutex_type& __m, try_to_lock_t)
      : __m_(std::addressof(__m)), __owns_(__m.try_lock_shared()) {}

  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI shared_lock(mutex_type& __m, adopt_lock_t)
      : __m_(std::addressof(__m)), __owns_(true) {}

  template <class _Clock, class _Duration>
  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI
  shared_lock(mutex_type& __m, const chrono::time_point<_Clock, _Duration>& __abs_time)
      : __m_(std::addressof(__m)), __owns_(__m.try_lock_shared_until(__abs_time)) {}

  template <class _Rep, class _Period>
  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI
  shared_lock(mutex_type& __m, const chrono::duration<_Rep, _Period>& __rel_time)
      : __m_(std::addressof(__m)), __owns_(__m.try_lock_shared_for(__rel_time)) {}

  _LIBCPP_HIDE_FROM_ABI ~shared_lock() {
    if (__owns_)
      __m_->unlock_shared();
  }

  shared_lock(shared_lock const&)            = delete;
  shared_lock& operator=(shared_lock const&) = delete;

  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI shared_lock(shared_lock&& __u) noexcept
      : __m_(__u.__m_), __owns_(__u.__owns_) {
    __u.__m_    = nullptr;
    __u.__owns_ = false;
  }

  _LIBCPP_HIDE_FROM_ABI shared_lock& operator=(shared_lock&& __u) noexcept {
    if (this != std::addressof(__u))
      shared_lock(std::move(__u)).swap(*this);
    return *this;
  }

  _LIBCPP_HIDE_FROM_ABI void lock();
  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool try_lock();
  template <class _Rep, class _Period>
  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time);
  template <class _Clock, class _Duration>
  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
  _LIBCPP_HIDE_FROM_ABI void unlock();

  // Setters
  _LIBCPP_HIDE_FROM_ABI void swap(shared_lock& __u) noexcept {
    std::swap(__m_, __u.__m_);
    std::swap(__owns_, __u.__owns_);
  }

  _LIBCPP_HIDE_FROM_ABI mutex_type* release() noexcept {
    mutex_type* __m = __m_;
    __m_            = nullptr;
    __owns_         = false;
    return __m;
  }

  // Getters
  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool owns_lock() const noexcept { return __owns_; }

  _LIBCPP_HIDE_FROM_ABI explicit operator bool() const noexcept { return __owns_; }

  [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI mutex_type* mutex() const noexcept { return __m_; }
};
_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(shared_lock);

template <class _Mutex>
void shared_lock<_Mutex>::lock() {
  if (__m_ == nullptr)
    std::__throw_system_error(EPERM, "shared_lock::lock: references null mutex");
  if (__owns_)
    std::__throw_system_error(EDEADLK, "shared_lock::lock: already locked");
  __m_->lock_shared();
  __owns_ = true;
}

template <class _Mutex>
bool shared_lock<_Mutex>::try_lock() {
  if (__m_ == nullptr)
    std::__throw_system_error(EPERM, "shared_lock::try_lock: references null mutex");
  if (__owns_)
    std::__throw_system_error(EDEADLK, "shared_lock::try_lock: already locked");
  __owns_ = __m_->try_lock_shared();
  return __owns_;
}

template <class _Mutex>
template <class _Rep, class _Period>
bool shared_lock<_Mutex>::try_lock_for(const chrono::duration<_Rep, _Period>& __d) {
  if (__m_ == nullptr)
    std::__throw_system_error(EPERM, "shared_lock::try_lock_for: references null mutex");
  if (__owns_)
    std::__throw_system_error(EDEADLK, "shared_lock::try_lock_for: already locked");
  __owns_ = __m_->try_lock_shared_for(__d);
  return __owns_;
}

template <class _Mutex>
template <class _Clock, class _Duration>
bool shared_lock<_Mutex>::try_lock_until(const chrono::time_point<_Clock, _Duration>& __t) {
  if (__m_ == nullptr)
    std::__throw_system_error(EPERM, "shared_lock::try_lock_until: references null mutex");
  if (__owns_)
    std::__throw_system_error(EDEADLK, "shared_lock::try_lock_until: already locked");
  __owns_ = __m_->try_lock_shared_until(__t);
  return __owns_;
}

template <class _Mutex>
void shared_lock<_Mutex>::unlock() {
  if (!__owns_)
    std::__throw_system_error(EPERM, "shared_lock::unlock: not locked");
  __m_->unlock_shared();
  __owns_ = false;
}

template <class _Mutex>
inline _LIBCPP_HIDE_FROM_ABI void swap(shared_lock<_Mutex>& __x, shared_lock<_Mutex>& __y) noexcept {
  __x.swap(__y);
}

_LIBCPP_END_EXPLICIT_ABI_ANNOTATIONS
_LIBCPP_END_NAMESPACE_STD

#    endif // _LIBCPP_STD_VER >= 14

_LIBCPP_POP_MACROS

#  endif // _LIBCPP_HAS_THREADS

#endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)

#endif // _LIBCPP_SHARED_MUTEX