csem.c

Intel PXA270 Wince5.0 BSP

//
// Copyright (c) Microsoft Corporation.  All rights reserved.
//
//
// Use of this source code is subject to the terms of the Microsoft end-user
// license agreement (EULA) under which you licensed this SOFTWARE PRODUCT.
// If you did not accept the terms of the EULA, you are not authorized to use
// this source code. For a copy of the EULA, please see the LICENSE.RTF on your
// install media.
//
/*
 * This module implements a synchronization object like a
 * Win32 semaphore, except that its state is signalled if
 * (and only if) the count is equal to zero.
 *
 */

#include <globals.hpp>

void InitCountdown (Countdown *psem, DWORD cInitial)
{
    psem->count = cInitial;
    psem->hev = CreateEvent(NULL, TRUE, cInitial ? FALSE : TRUE, NULL);
    InitializeCriticalSection(&psem->cs);
    psem->lock = FALSE;
}

BOOL IncrCountdown (Countdown *psem)
{
    BOOL r = TRUE;

    EnterCriticalSection(&psem->cs);
    if (psem->lock)
        r = FALSE;
    else
        if (psem->count++ == 0)
            ResetEvent(psem->hev);
    LeaveCriticalSection(&psem->cs);

    return r;
}

void DecrCountdown (Countdown *psem)
{
    EnterCriticalSection(&psem->cs);
    ASSERT(psem->count > 0);
    if (--psem->count == 0)
        SetEvent(psem->hev);
    LeaveCriticalSection(&psem->cs);
}

void LockCountdown (Countdown *psem)
{
    EnterCriticalSection(&psem->cs);
    psem->lock = TRUE;
    LeaveCriticalSection(&psem->cs);
}

static void WaitForCountdown (Countdown *psem, BOOL keepLocked)
{
    LockCountdown(psem);
    
    WaitForSingleObject(psem->hev, INFINITE);
    ASSERT(psem->count == 0);

    psem->lock = keepLocked;
}

void DeleteCountdown (Countdown *psem)
{
    WaitForCountdown(psem, TRUE);

    CloseHandle(psem->hev);
    DeleteCriticalSection(&psem->cs);
}