view src/thread/win32/SDL_syssem.c @ 968:4675910b0b7b

Date: Mon, 11 Oct 2004 15:17:27 +0300 (EEST) From: Hannu Savolainen Subject: Re: SDL uses obsolete OSS features I did some work on getting OSS to work better with SDL. There have been some problems with select which should be fixed now. I'm having some problems in understanding what is the purpose of the DSP_WaitAudio() routine. I added a return to the very beginning of this routine and commendted out the define for USE_BLOCKING_WRITES. At least lbreakout2 seems to work as well as earlier. The latencies are the same. An ordinary blocking write does exactly the same thing than DSP_WaitAudio does. So I would recommend using the USE_BLOCKING_WRITES approach and removing everything from the DSP_WaitAudio routine. Also enabling USE_BLOCKING_WRITES makes it possible to simplify DSP_PlayAudio() because you don't need to handle the partial writes (the do-while loop). Attached is a patch against SDL-1.2.7. After these changes SDL will use OSS as it's designed to be used (make it as simple as possible). This code should work with all OSS implementations because it uses only the very fundamental features that have been there since the jurassic times.
author Sam Lantinga <slouken@libsdl.org>
date Fri, 12 Nov 2004 21:39:04 +0000
parents b8d311d90021
children c9b51268668f
line wrap: on
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/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2004 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
    slouken@libsdl.org
*/

#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;
}