/*
* barrier.h
*
* This header file describes the "barrier" synchronization
* construct. The type barrier_t describes the full state of the
* barrier including the POSIX 1003.1c synchronization objects
* necessary.
*
* A barrier causes threads to wait until a set of threads has
* all "reached" the barrier. The number of threads required is
* set when the barrier is initialized, and cannot be changed
* except by reinitializing.
*/
#include <pthread.h>

#define EINVAL -1
#define EBUSY  -2

/*
* Structure describing a barrier.
*/
typedef struct barrier_tag {
	pthread_mutex_t     mutex;          /* Control access to barrier */
	pthread_cond_t      cv;             /* wait for barrier */
	int                 valid;          /* set when valid */
	int                 threshold;      /* number of threads required */
	int                 counter;        /* current number of threads */
	int                 cycle;          /* alternate wait cycles (0 or 1) */
} barrier_t;

#define BARRIER_VALID   0xdbcafe

/*
* Support static initialization of barriers
*/
#define BARRIER_INITIALIZER(cnt) \
	{PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, \
	BARRIER_VALID, cnt, cnt, 0}

/*
* Define barrier functions
*/
extern int barrier_init (barrier_t *barrier, int count);
extern int barrier_destroy (barrier_t *barrier);
extern int barrier_wait (barrier_t *barrier);