// (C) Copyright 2013 Andrey Semashev
// (C) Copyright 2013 Vicente J. Botet Escriba
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//#define __STDC_CONSTANT_MACROS
#include <boost/thread/detail/config.hpp>
#include <boost/thread/once.hpp>
#include <boost/thread/pthread/pthread_helpers.hpp>
#include <boost/thread/pthread/pthread_mutex_scoped_lock.hpp>
#include <boost/assert.hpp>
#include <boost/static_assert.hpp>
#include <boost/memory_order.hpp>
#include <boost/atomic/atomic.hpp>
#include <pthread.h>

namespace boost
{
 namespace thread_detail
 {

 enum flag_states
 {
 uninitialized, in_progress, initialized
 };


#ifndef BOOST_THREAD_PROVIDES_ONCE_CXX11
 BOOST_STATIC_ASSERT_MSG(sizeof(atomic_int_type) == sizeof(atomic_type), "Boost.Thread: unsupported platform");
#endif

 static pthread_mutex_t once_mutex = PTHREAD_MUTEX_INITIALIZER;
 static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER;

 BOOST_THREAD_DECL bool enter_once_region(once_flag& flag) BOOST_NOEXCEPT
 {
 atomic_type& f = get_atomic_storage(flag);
 if (f.load(memory_order_acquire) != initialized)
 {
 pthread::pthread_mutex_scoped_lock lk(&once_mutex);
 if (f.load(memory_order_acquire) != initialized)
 {
 for (;;)
 {
 atomic_int_type expected = uninitialized;
 if (f.compare_exchange_strong(expected, in_progress, memory_order_acq_rel, memory_order_acquire))
 {
 // We have set the flag to in_progress
 return true;
 }
 else if (expected == initialized)
 {
 // Another thread managed to complete the initialization
 return false;
 }
 else
 {
 // Wait until the initialization is complete
 //pthread::pthread_mutex_scoped_lock lk(&once_mutex);
 BOOST_VERIFY(!posix::pthread_cond_wait(&once_cv, &once_mutex));
 }
 }
 }
 }
 return false;
 }

 BOOST_THREAD_DECL void commit_once_region(once_flag& flag) BOOST_NOEXCEPT
 {
 atomic_type& f = get_atomic_storage(flag);
 {
 pthread::pthread_mutex_scoped_lock lk(&once_mutex);
 f.store(initialized, memory_order_release);
 }
 BOOST_VERIFY(!posix::pthread_cond_broadcast(&once_cv));
 }

 BOOST_THREAD_DECL void rollback_once_region(once_flag& flag) BOOST_NOEXCEPT
 {
 atomic_type& f = get_atomic_storage(flag);
 {
 pthread::pthread_mutex_scoped_lock lk(&once_mutex);
 f.store(uninitialized, memory_order_release);
 }
 BOOST_VERIFY(!posix::pthread_cond_broadcast(&once_cv));
 }

 } // namespace thread_detail

} // namespace boost