libcxx/include/condition_variable

// -*- 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_CONDITION_VARIABLE
#define _LIBCPP_CONDITION_VARIABLE

/*
    condition_variable synopsis

namespace std
{

enum class cv_status { no_timeout, timeout };

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

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

    void notify_one() noexcept;
    void notify_all() noexcept;

    void wait(unique_lock<mutex>& lock);
    template <class Predicate>
        void wait(unique_lock<mutex>& lock, Predicate pred);

    template <class Clock, class Duration>
        cv_status
        wait_until(unique_lock<mutex>& lock,
                   const chrono::time_point<Clock, Duration>& abs_time);

    template <class Clock, class Duration, class Predicate>
        bool
        wait_until(unique_lock<mutex>& lock,
                   const chrono::time_point<Clock, Duration>& abs_time,
                   Predicate pred);

    template <class Rep, class Period>
        cv_status
        wait_for(unique_lock<mutex>& lock,
                 const chrono::duration<Rep, Period>& rel_time);

    template <class Rep, class Period, class Predicate>
        bool
        wait_for(unique_lock<mutex>& lock,
                 const chrono::duration<Rep, Period>& rel_time,
                 Predicate pred);

    typedef pthread_cond_t* native_handle_type;
    native_handle_type native_handle();
};

void notify_all_at_thread_exit(condition_variable& cond, unique_lock<mutex> lk);

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

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

    void notify_one() noexcept;
    void notify_all() noexcept;

    template <class Lock>
        void wait(Lock& lock);
    template <class Lock, class Predicate>
        void wait(Lock& lock, Predicate pred);

    template <class Lock, class Clock, class Duration>
        cv_status
        wait_until(Lock& lock,
                   const chrono::time_point<Clock, Duration>& abs_time);

    template <class Lock, class Clock, class Duration, class Predicate>
        bool
        wait_until(Lock& lock,
                   const chrono::time_point<Clock, Duration>& abs_time,
                   Predicate pred);

    template <class Lock, class Rep, class Period>
        cv_status
        wait_for(Lock& lock,
                 const chrono::duration<Rep, Period>& rel_time);

    template <class Lock, class Rep, class Period, class Predicate>
        bool
        wait_for(Lock& lock,
                 const chrono::duration<Rep, Period>& rel_time,
                 Predicate pred);

    // [thread.condvarany.intwait], interruptible waits
    template <class Lock, class Predicate>
      bool wait(Lock& lock, stop_token stoken, Predicate pred);                               // since C++20

    template <class Lock, class Clock, class Duration, class Predicate>
      bool wait_until(Lock& lock, stop_token stoken,
                      const chrono::time_point<Clock, Duration>& abs_time, Predicate pred);   // since C++20

    template <class Lock, class Rep, class Period, class Predicate>
      bool wait_for(Lock& lock, stop_token stoken,
                    const chrono::duration<Rep, Period>& rel_time, Predicate pred);           // since C++20
};

}  // std

*/

#if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
#  include <__cxx03/condition_variable>
#else
#  include <__chrono/duration.h>
#  include <__chrono/steady_clock.h>
#  include <__chrono/time_point.h>
#  include <__condition_variable/condition_variable.h>
#  include <__config>
#  include <__memory/shared_ptr.h>
#  include <__mutex/lock_guard.h>
#  include <__mutex/mutex.h>
#  include <__mutex/tag_types.h>
#  include <__mutex/unique_lock.h>
#  include <__stop_token/stop_callback.h>
#  include <__stop_token/stop_token.h>
#  include <__utility/move.h>
#  include <version>

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

_LIBCPP_PUSH_MACROS
#  include <__undef_macros>

#  if _LIBCPP_HAS_THREADS

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _Lock>
struct __unlock_guard {
  _Lock& __lock_;

  _LIBCPP_HIDE_FROM_ABI __unlock_guard(_Lock& __lock) : __lock_(__lock) { __lock_.unlock(); }

  _LIBCPP_HIDE_FROM_ABI ~__unlock_guard() _NOEXCEPT // turns exception to std::terminate
  {
    __lock_.lock();
  }

  __unlock_guard(const __unlock_guard&)            = delete;
  __unlock_guard& operator=(const __unlock_guard&) = delete;
};

class _LIBCPP_EXPORTED_FROM_ABI condition_variable_any {
  condition_variable __cv_;
  shared_ptr<mutex> __mut_;

public:
  _LIBCPP_HIDE_FROM_ABI condition_variable_any();

  _LIBCPP_HIDE_FROM_ABI void notify_one() _NOEXCEPT;
  _LIBCPP_HIDE_FROM_ABI void notify_all() _NOEXCEPT;

  template <class _Lock>
  _LIBCPP_HIDE_FROM_ABI void wait(_Lock& __lock) {
    shared_ptr<mutex> __mut = __mut_;
    unique_lock<mutex> __lk(*__mut);
    __unlock_guard<_Lock> __unlock(__lock);
    lock_guard<unique_lock<mutex> > __lx(__lk, adopt_lock_t());
    __cv_.wait(__lk);
  } // __mut_.unlock(), __lock.lock()

  template <class _Lock, class _Predicate>
  _LIBCPP_HIDE_FROM_ABI void wait(_Lock& __lock, _Predicate __pred);

  template <class _Lock, class _Clock, class _Duration>
  _LIBCPP_HIDE_FROM_ABI cv_status wait_until(_Lock& __lock, const chrono::time_point<_Clock, _Duration>& __t) {
    shared_ptr<mutex> __mut = __mut_;
    unique_lock<mutex> __lk(*__mut);
    __unlock_guard<_Lock> __unlock(__lock);
    lock_guard<unique_lock<mutex> > __lx(__lk, adopt_lock_t());
    return __cv_.wait_until(__lk, __t);
  } // __mut_.unlock(), __lock.lock()

  template <class _Lock, class _Clock, class _Duration, class _Predicate>
  bool _LIBCPP_HIDE_FROM_ABI
  wait_until(_Lock& __lock, const chrono::time_point<_Clock, _Duration>& __t, _Predicate __pred);

  template <class _Lock, class _Rep, class _Period>
  cv_status _LIBCPP_HIDE_FROM_ABI wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __d);

  template <class _Lock, class _Rep, class _Period, class _Predicate>
  bool _LIBCPP_HIDE_FROM_ABI wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __d, _Predicate __pred);

#    if _LIBCPP_STD_VER >= 20

  template <class _Lock, class _Predicate>
  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool wait(_Lock& __lock, stop_token __stoken, _Predicate __pred);

  template <class _Lock, class _Clock, class _Duration, class _Predicate>
  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool wait_until(
      _Lock& __lock, stop_token __stoken, const chrono::time_point<_Clock, _Duration>& __abs_time, _Predicate __pred);

  template <class _Lock, class _Rep, class _Period, class _Predicate>
  _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool
  wait_for(_Lock& __lock, stop_token __stoken, const chrono::duration<_Rep, _Period>& __rel_time, _Predicate __pred);

#    endif // _LIBCPP_STD_VER >= 20
};

inline condition_variable_any::condition_variable_any() : __mut_(make_shared<mutex>()) {}

inline void condition_variable_any::notify_one() _NOEXCEPT {
  { lock_guard<mutex> __lx(*__mut_); }
  __cv_.notify_one();
}

inline void condition_variable_any::notify_all() _NOEXCEPT {
  { lock_guard<mutex> __lx(*__mut_); }
  __cv_.notify_all();
}

template <class _Lock, class _Predicate>
inline void condition_variable_any::wait(_Lock& __lock, _Predicate __pred) {
  while (!__pred())
    wait(__lock);
}

template <class _Lock, class _Clock, class _Duration, class _Predicate>
inline bool
condition_variable_any::wait_until(_Lock& __lock, const chrono::time_point<_Clock, _Duration>& __t, _Predicate __pred) {
  while (!__pred())
    if (wait_until(__lock, __t) == cv_status::timeout)
      return __pred();
  return true;
}

template <class _Lock, class _Rep, class _Period>
inline cv_status condition_variable_any::wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __d) {
  return wait_until(__lock, chrono::steady_clock::now() + __d);
}

template <class _Lock, class _Rep, class _Period, class _Predicate>
inline bool
condition_variable_any::wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __d, _Predicate __pred) {
  return wait_until(__lock, chrono::steady_clock::now() + __d, std::move(__pred));
}

#    if _LIBCPP_STD_VER >= 20

template <class _Lock, class _Predicate>
bool condition_variable_any::wait(_Lock& __user_lock, stop_token __stoken, _Predicate __pred) {
  if (__stoken.stop_requested())
    return __pred();

  // Per https://eel.is/c++draft/thread.condition.condvarany#general-note-2,
  // we do need to take a copy of the shared pointer __mut_
  // This ensures that a thread can call the destructor immediately after calling
  // notify_all, without waiting all the wait calls.
  // A thread can also safely call the destructor immediately after calling
  // request_stop, as the call to request_stop would evaluate the callback,
  // which accesses the internal condition variable, immediately on the same thread.
  // In this situation, it is OK even without copying a shared ownership the internal
  // condition variable. However, this needs the evaluation of stop_callback to
  // happen-before the destruction.
  // The spec only says "Only the notification to unblock the wait needs to happen
  // before destruction". To make this work, we need to copy the shared ownership of
  // the internal condition variable inside this function, which is not possible
  // with the current ABI.
  shared_ptr<mutex> __mut = __mut_;

  stop_callback __cb(__stoken, [this] { notify_all(); });

  while (true) {
    if (__pred())
      return true;

    // We need to take the internal lock before checking stop_requested,
    // so that the notification cannot come in between the stop_requested
    // check and entering the wait.
    // Note that the stop_callback takes the same internal lock before notifying
    unique_lock<mutex> __internal_lock(*__mut);
    if (__stoken.stop_requested())
      break;

    __unlock_guard<_Lock> __unlock(__user_lock);
    unique_lock<mutex> __internal_lock2(
        std::move(__internal_lock)); // switch unlock order between __internal_lock and __user_lock
    __cv_.wait(__internal_lock2);
  } // __internal_lock2.unlock(), __user_lock.lock()
  return __pred();
}

template <class _Lock, class _Clock, class _Duration, class _Predicate>
bool condition_variable_any::wait_until(
    _Lock& __user_lock,
    stop_token __stoken,
    const chrono::time_point<_Clock, _Duration>& __abs_time,
    _Predicate __pred) {
  if (__stoken.stop_requested())
    return __pred();

  shared_ptr<mutex> __mut = __mut_;
  stop_callback __cb(__stoken, [this] { notify_all(); });

  while (true) {
    if (__pred())
      return true;

    unique_lock<mutex> __internal_lock(*__mut);
    if (__stoken.stop_requested())
      break;

    __unlock_guard<_Lock> __unlock(__user_lock);
    unique_lock<mutex> __internal_lock2(
        std::move(__internal_lock)); // switch unlock order between __internal_lock and __user_lock

    if (__cv_.wait_until(__internal_lock2, __abs_time) == cv_status::timeout)
      break;
  } // __internal_lock2.unlock(), __user_lock.lock()
  return __pred();
}

template <class _Lock, class _Rep, class _Period, class _Predicate>
bool condition_variable_any::wait_for(
    _Lock& __lock, stop_token __stoken, const chrono::duration<_Rep, _Period>& __rel_time, _Predicate __pred) {
  return wait_until(__lock, std::move(__stoken), chrono::steady_clock::now() + __rel_time, std::move(__pred));
}

#    endif // _LIBCPP_STD_VER >= 20

_LIBCPP_EXPORTED_FROM_ABI void notify_all_at_thread_exit(condition_variable&, unique_lock<mutex>);

_LIBCPP_END_NAMESPACE_STD

#  endif // _LIBCPP_HAS_THREADS

_LIBCPP_POP_MACROS

#  if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
#    include <atomic>
#    include <concepts>
#    include <cstdint>
#    include <cstdlib>
#    include <cstring>
#    include <initializer_list>
#    include <iosfwd>
#    include <new>
#    include <optional>
#    include <stdexcept>
#    include <system_error>
#    include <type_traits>
#    include <typeinfo>
#  endif
#endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)

#endif // _LIBCPP_CONDITION_VARIABLE