blender-archive/source/blender/blenlib/intern/threads.c

/**
 *
 * $Id:
 *
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version. 
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * The Original Code is Copyright (C) 2006 Blender Foundation
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): none yet.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include <math.h>
#include <stdlib.h>
#include <string.h>
#include "MEM_guardedalloc.h"

#include "BLI_blenlib.h"
#include "BLI_threads.h"

#include "SDL_thread.h"

/* ********** basic thread control API ************ 

Many thread cases have an X amount of jobs, and only an Y amount of
threads are useful (typically amount of cpus)

This code can be used to start a maximum amount of 'thread slots', which
then can be filled in a loop with an idle timer. 

A sample loop can look like this (pseudo c);

	ListBase lb;
	int maxthreads= 2;
	int cont= 1;

	BLI_init_threads(&lb, do_something_func, maxthreads);

	while(cont) {
		if(BLI_available_threads(&lb) && !(escape loop event)) {
			// get new job (data pointer)
			// tag job 'processed 
			BLI_insert_thread(&lb, job);
		}
		else PIL_sleep_ms(50);
		
		// find if a job is ready, this the do_something_func() should write in job somewhere
		cont= 0;
		for(go over all jobs)
			if(job is ready) {
				if(job was not removed) {
					BLI_remove_thread(&lb, job);
				}
			}
			else cont= 1;
		}
		// conditions to exit loop 
		if(if escape loop event) {
			if(BLI_available_threadslots(&lb)==maxthreads)
				break;
		}
	}

	BLI_end_threads(&lb);

 ************************************************ */

/* just a max for security reasons */
#define RE_MAX_THREAD	8

typedef struct ThreadSlot {
	struct ThreadSlot *next, *prev;
	int (*do_thread)(void *);
	void *callerdata;
	SDL_Thread *sdlthread;
	int avail;
} ThreadSlot;

static ThreadSlot threadslots[RE_MAX_THREAD];

void BLI_init_threads(ListBase *threadbase, int (*do_thread)(void *), int tot)
{
	int a;
	
	if(threadbase==NULL)
		return;
	threadbase->first= threadbase->last= NULL;
	
	if(tot>RE_MAX_THREAD) tot= RE_MAX_THREAD;
	else if(tot<1) tot= 1;
	
	for(a=0; a<tot; a++) {
		ThreadSlot *tslot= MEM_callocN(sizeof(ThreadSlot), "threadslot");
		BLI_addtail(threadbase, tslot);
		tslot->do_thread= do_thread;
	}
}

/* amount of available threads */
int BLI_available_threads(ListBase *threadbase)
{
	ThreadSlot *tslot;
	int counter=0;
	
	for(tslot= threadbase->first; tslot; tslot= tslot->next) {
		if(tslot->sdlthread==NULL)
			counter++;
	}
	return counter;
}

/* returns thread number, for sample patterns or threadsafe tables */
int BLI_available_thread_index(ListBase *threadbase)
{
	ThreadSlot *tslot;
	int counter=0;
	
	for(tslot= threadbase->first; tslot; tslot= tslot->next, counter++) {
		if(tslot->sdlthread==NULL)
			return counter;
	}
	return 0;
}


void BLI_insert_thread(ListBase *threadbase, void *callerdata)
{
	ThreadSlot *tslot;
	
	for(tslot= threadbase->first; tslot; tslot= tslot->next) {
		if(tslot->sdlthread==NULL) {
			tslot->callerdata= callerdata;
			tslot->sdlthread= SDL_CreateThread(tslot->do_thread, tslot->callerdata);
			return;
		}
	}
	printf("ERROR: could not insert thread slot\n");
}

void BLI_remove_thread(ListBase *threadbase, void *callerdata)
{
	ThreadSlot *tslot;
	
	for(tslot= threadbase->first; tslot; tslot= tslot->next) {
		if(tslot->callerdata==callerdata) {
			tslot->callerdata= NULL;
			SDL_WaitThread(tslot->sdlthread, NULL);
			tslot->sdlthread= NULL;
		}
	}
}

void BLI_end_threads(ListBase *threadbase)
{
	ThreadSlot *tslot;
	
	for(tslot= threadbase->first; tslot; tslot= tslot->next) {
		if(tslot->sdlthread) {
			SDL_WaitThread(tslot->sdlthread, NULL);
		}
	}
	BLI_freelistN(threadbase);
}

/* eof */