www.pudn.com > pthread_examples.rar > control.c

/* control.c 
** Copyright 2000 Daniel Robbins, Gentoo Technologies, Inc. 
** Author: Daniel Robbins 
** Date: 16 Jun 2000 
** 
** These routines provide an easy way to make any type of 
** data-structure thread-aware.  Simply associate a data_control 
** structure with the data structure (by creating a new struct, for 
** example).  Then, simply lock and unlock the mutex, or 
** wait/signal/broadcast on the condition variable in the data_control 
** structure as needed. 
** 
** data_control structs contain an int called "active".  This int is 
** intended to be used for a specific kind of multithreaded design, 
** where each thread checks the state of "active" every time it locks 
** the mutex.  If active is 0, the thread knows that instead of doing 
** its normal routine, it should stop itself.  If active is 1, it 
** should continue as normal.  So, by setting active to 0, a 
** controlling thread can easily inform a thread work crew to shut 
** down instead of processing new jobs.  Use the control_activate() 
** and control_deactivate() functions, which will also broadcast on 
** the data_control struct's condition variable, so that all threads 
** stuck in pthread_cond_wait() will wake up, have an opportunity to 
** notice the change, and then terminate. 
*/ 
 
#include "control.h" 
 
int control_init(data_control *mycontrol)  
{ 
	if (pthread_mutex_init(&(mycontrol->mutex),NULL)) 
	{ 
		return 1; 
	} 
	 
	if (pthread_cond_init(&(mycontrol->cond),NULL)) 
	{ 
		return 1; 
	} 
	 
	mycontrol->active = 0; 
	return 0; 
} 
 
int control_destroy(data_control *mycontrol)  
{ 
	if (pthread_cond_destroy(&(mycontrol->cond))) 
	{ 
		return 1; 
	} 
 
	if (pthread_cond_destroy(&(mycontrol->cond))) 
	{ 
		return 1; 
	} 
	 
	mycontrol->active = 0; 
	return 0; 
} 
 
int control_activate(data_control *mycontrol)  
{ 
	if (pthread_mutex_lock(&(mycontrol->mutex))) 
	{ 
		return 0; 
	} 
	 
	mycontrol->active = 1; 
	pthread_mutex_unlock(&(mycontrol->mutex)); 
	pthread_cond_broadcast(&(mycontrol->cond)); 
	 
	return 1; 
} 
 
int control_deactivate(data_control *mycontrol)  
{ 
	if (pthread_mutex_lock(&(mycontrol->mutex))) 
	{ 
		return 0; 
	} 
	 
	mycontrol->active = 0; 
	pthread_mutex_unlock(&(mycontrol->mutex)); 
	pthread_cond_broadcast(&(mycontrol->cond)); 
	 
	return 1; 
}