semaphore.cc.svn-base

德国Erlangen大学教学操作系统源码。

/*****************************************************************************/
/* Betriebssysteme                                                           */
/*---------------------------------------------------------------------------*/
/*                                                                           */
/*                           S E M A P H O R E                               */
/*                                                                           */
/*---------------------------------------------------------------------------*/
/* Semaphore werden zur Synchronisation von Threads verwendet.               */
/*****************************************************************************/

#include "meeting/semaphore.h"
#include "thread/customer.h"
#include "syscall/guarded_organizer.h"

extern Guarded_Organizer scheduler;

Semaphore::Semaphore()
{
	_z= 1;
}

Semaphore::Semaphore(int c)
{
	_z = c;
}


Semaphore::~Semaphore()
{
}

void Semaphore::p()
{
	Customer *cust = static_cast<Customer*>(scheduler.Scheduler::active());
	if(_z==0) {
		enqueue(cust);
		scheduler.Organizer::block(*cust, *this);
	} else
		_z--;
}

void Semaphore::v()
{
	_z++;
	if (_z == 1) {
		Customer *cust = static_cast<Customer*>(dequeue());
		if (cust!=NULL) {
			_z--;
			scheduler.Organizer::wakeup(*cust);
		}
	}
}

void Semaphore::wait()
{
	p(); 
}

void Semaphore::signal()
{
	v(); 
}