sdl_syssem.c

SDL库 在进行视频显示程序spcaview安装时必须的库文件

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 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
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    [e-mail]
*/
#include "SDL_config.h"

/* Semaphores in the BeOS environment */

#include <be/kernel/OS.h>

#include "SDL_thread.h"


struct SDL_semaphore {
	sem_id id;
};

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

	sem = (SDL_sem *)SDL_malloc(sizeof(*sem));
	if ( sem ) {
		sem->id = create_sem(initial_value, "SDL semaphore");
		if ( sem->id < B_NO_ERROR ) {
			SDL_SetError("create_sem() failed");
			SDL_free(sem);
			sem = NULL;
		}
	} else {
		SDL_OutOfMemory();
	}
	return(sem);
}

/* Free the semaphore */
void SDL_DestroySemaphore(SDL_sem *sem)
{
	if ( sem ) {
		if ( sem->id >= B_NO_ERROR ) {
			delete_sem(sem->id);
		}
		SDL_free(sem);
	}
}

int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
{
	int32 val;
	int retval;

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

  tryagain:
	if ( timeout == SDL_MUTEX_MAXWAIT ) {
		val = acquire_sem(sem->id);
	} else {
		timeout *= 1000; /* BeOS uses a timeout in microseconds */
		val = acquire_sem_etc(sem->id, 1, B_RELATIVE_TIMEOUT, timeout);
	}
	switch (val) {
	    case B_INTERRUPTED:
		goto tryagain;
	    case B_NO_ERROR:
		retval = 0;
		break;
	    case B_TIMED_OUT:
		retval = SDL_MUTEX_TIMEDOUT;
		break;
	    case B_WOULD_BLOCK:
		retval = SDL_MUTEX_TIMEDOUT;
		break;
	    default:
		SDL_SetError("acquire_sem() 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)
{
	int32 count;
	Uint32 value;

	value = 0;
	if ( sem ) {
		get_sem_count(sem->id, &count);
		if ( count > 0 ) {
			value = (Uint32)count;
		}
	}
	return value;
}

/* Atomically increases the semaphore's count (not blocking) */
int SDL_SemPost(SDL_sem *sem)
{
	if ( ! sem ) {
		SDL_SetError("Passed a NULL semaphore");
		return -1;
	}

	if ( release_sem(sem->id) != B_NO_ERROR ) {
		SDL_SetError("release_sem() failed");
		return -1;
	}
	return 0;
}