sdl_syssem.c

网络MPEG4IP流媒体开发源代码

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002  Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    [e-mail]
*/

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id$";
#endif

/* Semaphore functions using the Win32 API */

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

#include "SDL_error.h"
#include "SDL_thread.h"
#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
#include "win_ce_semaphore.h"
#endif


struct SDL_semaphore {
#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
	SYNCHHANDLE id;
#else
	HANDLE id;
#endif
	Uint32 volatile count;
};


/* Create a semaphore */
SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
{
	SDL_sem *sem;

	/* Allocate sem memory */
	sem = (SDL_sem *)malloc(sizeof(*sem));
	if ( sem ) {
		/* Create the semaphore, with max value 32K */
#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
		sem->id = CreateSemaphoreCE(NULL, initial_value, 32*1024, NULL);
#else
		sem->id = CreateSemaphore(NULL, initial_value, 32*1024, NULL);
#endif
		sem->count = initial_value;
		if ( ! sem->id ) {
			SDL_SetError("Couldn't create semaphore");
			free(sem);
			sem = NULL;
		}
	} else {
		SDL_OutOfMemory();
	}
	return(sem);
}

/* Free the semaphore */
void SDL_DestroySemaphore(SDL_sem *sem)
{
	if ( sem ) {
		if ( sem->id ) {
#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
			CloseSynchHandle(sem->id);
#else
			CloseHandle(sem->id);
#endif
			sem->id = 0;
		}
		free(sem);
	}
}

int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
{
	int retval;
	DWORD dwMilliseconds;

	if ( ! sem ) {
		SDL_SetError("Passed a NULL sem");
		return -1;
	}

	if ( timeout == SDL_MUTEX_MAXWAIT ) {
		dwMilliseconds = INFINITE;
	} else {
		dwMilliseconds = (DWORD)timeout;
	}
#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
	switch (WaitForSemaphoreCE(sem->id, dwMilliseconds)) {
#else
	switch (WaitForSingleObject(sem->id, dwMilliseconds)) {
#endif
	    case WAIT_OBJECT_0:
		--sem->count;
		retval = 0;
		break;
	    case WAIT_TIMEOUT:
		retval = SDL_MUTEX_TIMEDOUT;
		break;
	    default:
		SDL_SetError("WaitForSingleObject() failed");
		retval = -1;
		break;
	}
	return retval;
}

int SDL_SemTryWait(SDL_sem *sem)
{
	return SDL_SemWaitTimeout(sem, 0);
}

int SDL_SemWait(SDL_sem *sem)
{
	return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
}

/* Returns the current count of the semaphore */
Uint32 SDL_SemValue(SDL_sem *sem)
{
	if ( ! sem ) {
		SDL_SetError("Passed a NULL sem");
		return 0;
	}
	return sem->count;
}

int SDL_SemPost(SDL_sem *sem)
{
	if ( ! sem ) {
		SDL_SetError("Passed a NULL sem");
		return -1;
	}
	/* Increase the counter in the first place, because
	 * after a successful release the semaphore may
	 * immediately get destroyed by another thread which
	 * is waiting for this semaphore.
	 */
	++sem->count;
#if defined(_WIN32_WCE) && (_WIN32_WCE < 300)
	if ( ReleaseSemaphoreCE(sem->id, 1, NULL) == FALSE ) {
#else
	if ( ReleaseSemaphore(sem->id, 1, NULL) == FALSE ) {
#endif
		--sem->count;	/* restore */
		SDL_SetError("ReleaseSemaphore() failed");
		return -1;
	}
	return 0;
}