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/*
* This code is from the book "Programming with POSIX Threads", by
* David R. Butenhof. Appears in modified and GPL'ed form in at least
* the Bacula sources.
*/
#ifndef RWLOCK_H
#define RWLOCK_H
/*
* rwlock.h
*
* This header file describes the "reader/writer lock" synchronization
* construct. The type rwlock_t describes the full state of the lock
* including the POSIX 1003.1c synchronization objects necessary.
*
* A reader/writer lock allows a thread to lock shared data either for shared
* read access or exclusive write access.
*
* The rwl_init() and rwl_destroy() functions, respectively, allow you to
* initialize/create and destroy/free the reader/writer lock.
*/
#include <pthread.h>
#ifdef PTHREAD_RWLOCK_INITIALIZER
// #ifdef HAVE_PTHREAD_RWLOCK
#define rwlock_t pthread_rwlock_t
#define RWL_INITIALIZER PTHREAD_RWLOCK_INITIALIZER
#define rwl_init(tag) pthread_rwlock_init(tag, NULL)
#define rwl_destroy pthread_rwlock_destroy
#define rwl_rdlock pthread_rwlock_rdlock
#define rwl_tryrdlock pthread_rwlock_tryrdlock
#define rwl_rdunlock pthread_rwlock_unlock
#define rwl_wrlock pthread_rwlock_wrlock
#define rwl_trywrlock pthread_rwlock_trywrlock
#define rwl_wrunlock pthread_rwlock_unlock
#else /* HAVE_PTHREAD_RWLOCK */
/*
* Structure describing a read-write lock.
*/
typedef struct rwlock_tag {
pthread_mutex_t mutex;
pthread_cond_t read; /* wait for read */
pthread_cond_t write; /* wait for write */
int valid; /* set when valid */
int r_active; /* readers active */
int w_active; /* writer active */
int r_wait; /* readers waiting */
int w_wait; /* writers waiting */
} rwlock_t;
#define RWLOCK_VALID 0xfacade
/*
* Support static initialization of read-write locks.
*/
#define RWL_INITIALIZER \
{PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, \
PTHREAD_COND_INITIALIZER, RWLOCK_VALID, 0, 0, 0, 0}
/*
* Define read-write lock functions
*/
extern int rwl_init (rwlock_t *rwlock);
extern int rwl_destroy (rwlock_t *rwlock);
extern int rwl_rdlock (rwlock_t *rwlock);
extern int rwl_tryrdlock (rwlock_t *rwlock);
extern int rwl_rdunlock (rwlock_t *rwlock);
extern int rwl_wrlock (rwlock_t *rwlock);
extern int rwl_trywrlock (rwlock_t *rwlock);
extern int rwl_wrunlock (rwlock_t *rwlock);
#endif /* not HAVE_POSIX_RWLOCK */
#endif /* RWLOCK_H */
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