//	Semesterarbeit Topsy TCP/IP
//	Reto Gaehler, Toni Kaufmann
//	Semaphore Module with the following limitations:
//	- smWait tmYield only needed for cooperative environment
//	- smSignal does only increment and not signal any waiting processes

#include "Semaphore.h"

//	semInit
//	initializes a semaphore
//
int semInit(SemaphorePtr pSem,int nsCount)
{
	if (pSem!=NULL)
	{
		lockInit(&pSem->recLock);
		lock(&pSem->recLock);
		pSem->nsCount = nsCount;
		unlock(&pSem->recLock);
		return SEM_OK;
	}
	return SEM_FAILED;
}

//	semReset
//	resets the semaphore counter
//
int semReset(SemaphorePtr pSem,int nsCount)
{
	if (pSem!=NULL)
	{
		lock(&pSem->recLock);
		pSem->nsCount = nsCount;
		unlock(&pSem->recLock);
		return SEM_OK;
	}
	return SEM_FAILED;
}

//	semCount
//	returns the semaphore counter
//
int semCount(SemaphorePtr pSem)
{
	if (pSem!=NULL)
	{
		return pSem->nsCount;
	}
	return SEM_FAILED;
}

//	semWait
//	decrements counter and waits until counter >= 0
//
int semWait(SemaphorePtr pSem)
{
	if (pSem!=NULL)
	{
		lock(&pSem->recLock);
		pSem->nsCount--;
		while (pSem->nsCount<0)
		{
			pSem->nsCount++;
			unlock(&pSem->recLock);
			tmYield();
			lock(&pSem->recLock);
			pSem->nsCount--;
		}
		unlock(&pSem->recLock);
		return SEM_OK;
	}
	return SEM_FAILED;
}

//	semSignal
//	increments counter
//
int semSignal(SemaphorePtr pSem)
{
	if (pSem!=NULL)
	{
		lock(&pSem->recLock);
		pSem->nsCount++;
		unlock(&pSem->recLock);
		return SEM_OK;
	}
	return SEM_FAILED;
}

//	semSignalIfLess
//	special signal for tcp implementation
//
int semSignalIfLess(SemaphorePtr pSem,int cmpValue)
{
	if (pSem!=NULL)
	{
		lock(&pSem->recLock);
		if (semCount(pSem)<cmpValue)
		{
			unlock(&pSem->recLock);
			return semSignal(pSem);
		}
		unlock(&pSem->recLock);
	}
	return SEM_FAILED;
}