#ifndef BOOST_SYSTEM_DETAIL_MUTEX_HPP_INCLUDED
#define BOOST_SYSTEM_DETAIL_MUTEX_HPP_INCLUDED

// Copyright 2023 Peter Dimov
// Distributed under the Boost Software License, Version 1.0.
// https://www.boost.org/LICENSE_1_0.txt)

#include <b/config.hpp>

#if defined(BOOST_SYSTEM_DISABLE_THREADS)

namespace boost
{
namespace system
{
namespace detail
{

struct mutex
{
    void lock()
    {
    }

    void unlock()
    {
    }
};

} // namespace detail
} // namespace system
} // namespace boost

#else // defined(BOOST_SYSTEM_DISABLE_THREADS)

#if defined(BOOST_MSSTL_VERSION) && BOOST_MSSTL_VERSION >= 140

// Under the MS STL, std::mutex::mutex() is not constexpr, as is
// required by the standard, which leads to initialization order
// issues. However, shared_mutex is based on SRWLock and its
// default constructor is constexpr, so we use that instead.

#include <b/winapi/config.hpp>

// SRWLOCK is not available when targeting Windows XP
#if BOOST_USE_WINAPI_VERSION >= BOOST_WINAPI_VERSION_WIN6

#include <shared_mutex>

#if BOOST_MSSTL_VERSION >= 142 || _HAS_SHARED_MUTEX
# define BOOST_SYSTEM_HAS_MSSTL_SHARED_MUTEX
#endif

#endif // BOOST_MSSTL_VERSION >= 142 || _HAS_SHARED_MUTEX

#endif // BOOST_USE_WINAPI_VERSION >= BOOST_WINAPI_VERSION_WIN6

#if defined(BOOST_SYSTEM_HAS_MSSTL_SHARED_MUTEX)

namespace boost
{
namespace system
{
namespace detail
{

typedef std::shared_mutex mutex;

} // namespace detail
} // namespace system
} // namespace boost

#else // defined(BOOST_SYSTEM_HAS_MSSTL_SHARED_MUTEX)

#include <mutex>

namespace boost
{
namespace system
{
namespace detail
{

using std::mutex;

} // namespace detail
} // namespace system
} // namespace boost

#endif // defined(BOOST_SYSTEM_HAS_MSSTL_SHARED_MUTEX)
#endif // defined(BOOST_SYSTEM_DISABLE_THREADS)

namespace boost
{
namespace system
{
namespace detail
{

template<class Mtx> class lock_guard
{
private:

    Mtx& mtx_;

private:

    lock_guard( lock_guard const& );
    lock_guard& operator=( lock_guard const& );

public:

    explicit lock_guard( Mtx& mtx ): mtx_( mtx )
    {
        mtx_.lock();
    }

    ~lock_guard()
    {
        mtx_.unlock();
    }
};

} // namespace detail
} // namespace system
} // namespace boost

#endif // #ifndef BOOST_SYSTEM_DETAIL_MUTEX_HPP_INCLUDED
