libcruft-util/thread/semaphore_win32.cpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2018 Danny Robson <danny@nerdcruft.net>
 */

#include "semaphore_win32.hpp"

#include "../win32/except.hpp"
#include "../win32/windows.hpp"

#include "../debug.hpp"

using cruft::thread::semaphore;


///////////////////////////////////////////////////////////////////////////////
semaphore::semaphore ():
    semaphore (1)
{ ; }


//-----------------------------------------------------------------------------
semaphore::semaphore (value_type initial):
    m_handle (
        win32::error::try_call (
            CreateSemaphore,
            nullptr,
            initial,
            std::numeric_limits<LONG>::max (),
            nullptr
        )
    )
{
    m_value = initial;
}


///////////////////////////////////////////////////////////////////////////////
semaphore::value_type
semaphore::acquire (value_type const count)
{
    CHECK_GE (count, 0);

    for (value_type i = 0; i < count; ++i) {
        if (WAIT_OBJECT_0 != WaitForSingleObject(m_handle.native(), INFINITE))
            win32::error::throw_code();
        --m_value;
    }

    return m_value;
}


//-----------------------------------------------------------------------------
semaphore::value_type
semaphore::acquire (void)
{
    return acquire (1);
}


//-----------------------------------------------------------------------------
semaphore::value_type
semaphore::release (value_type count)
{
    LONG previous;
    for (value_type i = 0; i < count; ++i) {
        if (!ReleaseSemaphore (m_handle.native(), count, &previous))
            win32::error::throw_code ();
        ++m_value;
    }

    return previous + 1;
}


//-----------------------------------------------------------------------------
semaphore::value_type
semaphore::release (void)
{
    return release (1);
}


///////////////////////////////////////////////////////////////////////////////
semaphore::value_type
semaphore::value (void) const
{
    return m_value;
}


//-----------------------------------------------------------------------------
semaphore::value_type
semaphore::operator++ (void)
{
    return release ();
}


//-----------------------------------------------------------------------------
semaphore::value_type
semaphore::operator-- (void)
{
    return acquire ();
}