sem.h File Reference

Semaphore implementation for the synchronization of POSIX threads. More...

Go to the source code of this file.

Typedefs
typedef struct SEM	SEM
Functions
SEM *	sem_init (int initVal)
	Creates a new semaphore.
int	sem_del (SEM *sem)
	Destroys a semaphore and frees all associated resources.
void	P (SEM *sem)
	P operation.
void	V (SEM *sem)
	V operation.

---

Detailed Description

Semaphore implementation for the synchronization of POSIX threads.

This module implements counting P/V semaphores suitable for the synchronization of POSIX threads. POSIX mutexes and condition variables shall be utilized to implement the semaphor operations.

---

Typedef Documentation

typedef struct SEM SEM

Opaque type of a semaphore.

---

Function Documentation

void P

(

SEM *

sem

)

P operation.

Attempts to decrement the semaphore value by 1. If the semaphore value is 0, the operation blocks until a V operation increments the value and the P operation succeeds.

Parameters:

sem

handle of the semaphore to decrement

int sem_del

(

SEM *

sem

)

Destroys a semaphore and frees all associated resources.

Parameters:

sem

handle of the semaphore to destroy

Returns:

0 on success, negative value on error. In case of an error, not all resources may have been freed, but nevertheless the semaphore handle must not be used any more.

SEM* sem_init

(

int

initVal

)

Creates a new semaphore.

This function creates a new semaphore. If an error occurs during the initialization, the implementation shall free all resources already allocated by then.

Parameters:

initVal

the initial value of the semaphore

Returns:

handle for the created semaphore, or NULL if an error occured.

void V

(

SEM *

sem

)

V operation.

Increments the semaphore value by 1 and notifies P operations that are blocked on the semaphore of the change.

Parameters:

sem

handle of the semaphore to increment