sdl_syscond.c

来自「MPEG-4编解码的实现(包括MPEG4视音频编解码)」· C语言 代码 · 共 141 行

/*
 *	GNU pth conditions variables
 *
 *	Patrice Mandin
 */

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

#include "SDL_error.h"
#include "SDL_thread.h"
#include "SDL_syscond_c.h"
#include "SDL_sysmutex_c.h"

/* Create a condition variable */
SDL_cond * SDL_CreateCond(void)
{
	SDL_cond *cond;

	cond = (SDL_cond *) malloc(sizeof(SDL_cond));
	if ( cond ) {
		if ( pth_cond_init(&(cond->condpth_p)) < 0 ) {
			SDL_SetError("pthread_cond_init() failed");
			free(cond);
			cond = NULL;
		}
	} else {
		SDL_OutOfMemory();
	}
	return(cond);
}

/* Destroy a condition variable */
void SDL_DestroyCond(SDL_cond *cond)
{
	if ( cond ) {
		free(cond);
	}
}

/* Restart one of the threads that are waiting on the condition variable */
int SDL_CondSignal(SDL_cond *cond)
{
	int retval;

	if ( ! cond ) {
		SDL_SetError("Passed a NULL condition variable");
		return -1;
	}

	retval = 0;
	if ( pth_cond_notify(&(cond->condpth_p), FALSE) != 0 ) {
		SDL_SetError("pth_cond_notify() failed");
		retval = -1;
	}
	return retval;
}

/* Restart all threads that are waiting on the condition variable */
int SDL_CondBroadcast(SDL_cond *cond)
{
	int retval;

	if ( ! cond ) {
		SDL_SetError("Passed a NULL condition variable");
		return -1;
	}

	retval = 0;
	if ( pth_cond_notify(&(cond->condpth_p), TRUE) != 0 ) {
		SDL_SetError("pth_cond_notify() failed");
		retval = -1;
	}
	return retval;
}

/* Wait on the condition variable for at most 'ms' milliseconds.
   The mutex must be locked before entering this function!
   The mutex is unlocked during the wait, and locked again after the wait.

Typical use:

Thread A:
	SDL_LockMutex(lock);
	while ( ! condition ) {
		SDL_CondWait(cond);
	}
	SDL_UnlockMutex(lock);

Thread B:
	SDL_LockMutex(lock);
	...
	condition = true;
	...
	SDL_UnlockMutex(lock);
 */
int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms)
{
	int retval;
	pth_event_t ev;
	int sec;

	if ( ! cond ) {
		SDL_SetError("Passed a NULL condition variable");
		return -1;
	}

	retval = 0;

	sec = ms/1000;
	ev = pth_event(PTH_EVENT_TIME, pth_timeout(sec,(ms-sec*1000)*1000));

	if ( pth_cond_await(&(cond->condpth_p), &(mutex->mutexpth_p), ev) != 0 ) {
		SDL_SetError("pth_cond_await() failed");
		retval = -1;
	}

    pth_event_free(ev, PTH_FREE_ALL);

	return retval;
}

/* Wait on the condition variable forever */
int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex)
{
	int retval;

	if ( ! cond ) {
		SDL_SetError("Passed a NULL condition variable");
		return -1;
	}

	retval = 0;
	if ( pth_cond_await(&(cond->condpth_p), &(mutex->mutexpth_p), NULL) != 0 ) {
		SDL_SetError("pth_cond_await() failed");
		retval = -1;
	}
	return retval;
}