haiku/headers/posix/lock.h

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#ifndef LOCK_H
#define LOCK_H
/* lock.h - benaphore locking, "faster semaphores", read/write locks
** sorry for all those macros; I wish C would support C++-style
** inline functions.
**
** Initial version by Axel Dörfler, axeld@pinc-software.de
**
** This file may be used under the terms of the OpenBeOS License.
*/
#include <SupportDefs.h>
// for read/write locks
#define MAX_READERS 100000
struct benaphore {
sem_id sem;
int32 count;
};
typedef struct benaphore benaphore;
// it may make sense to add a status field to the rw_lock to
// be able to check if the semaphore could be locked
struct rw_lock {
sem_id sem;
int32 count;
benaphore writeLock;
};
typedef struct rw_lock rw_lock;
#ifndef _KERNEL_
#define INIT_BENAPHORE(lock,name) \
{ \
(lock).count = 1; \
(lock).sem = create_sem(0, name); \
}
#else
#define INIT_BENAPHORE(lock,name) \
{ \
(lock).count = 1; \
(lock).sem = create_sem(0, name); \
set_sem_owner((lock).sem, B_SYSTEM_TEAM); \
}
#endif
#define CHECK_BENAPHORE(lock) \
((lock).sem)
#define UNINIT_BENAPHORE(lock) \
delete_sem((lock).sem);
#define ACQUIRE_BENAPHORE(lock) \
(atomic_add(&((lock).count), -1) <= 0 ? \
acquire_sem_etc((lock).sem, 1, B_CAN_INTERRUPT, 0) \
: B_OK)
#define RELEASE_BENAPHORE(lock) \
{ \
if (atomic_add(&((lock).count), 1) < 0) \
release_sem((lock).sem); \
}
/* read/write lock */
#ifndef _KERNEL_
#define INIT_RW_LOCK(lock,name) \
{ \
(lock).sem = create_sem(0, name); \
(lock).count = MAX_READERS; \
INIT_BENAPHORE((lock).writeLock, "r/w write lock"); \
}
#else
#define INIT_RW_LOCK(lock,name) \
{ \
(lock).sem = create_sem(0, name); \
set_sem_owner((lock).sem, B_SYSTEM_TEAM); \
(lock).count = MAX_READERS; \
INIT_BENAPHORE((lock).writeLock, "r/w write lock"); \
}
#endif
#define CHECK_RW_LOCK(lock) \
((lock).sem)
#define UNINIT_RW_LOCK(lock) \
delete_sem((lock).sem); \
UNINIT_BENAPHORE((lock).writeLock)
#define ACQUIRE_READ_LOCK(lock) \
{ \
if (atomic_add(&(lock).count, -1) <= 0) \
acquire_sem((lock).sem); \
}
#define RELEASE_READ_LOCK(lock) \
{ \
if (atomic_add(&(lock).count, 1) < 0) \
release_sem((lock).sem); \
}
#define ACQUIRE_WRITE_LOCK(lock) \
{ \
int32 readers; \
ACQUIRE_BENAPHORE((lock).writeLock); \
readers = atomic_add(&(lock).count, -MAX_READERS); \
if (readers < MAX_READERS) \
acquire_sem_etc((lock).sem,readers <= 0 ? 1 : MAX_READERS - readers,0,0); \
RELEASE_BENAPHORE((lock).writeLock); \
}
#define RELEASE_WRITE_LOCK(lock) \
{ \
int32 readers = atomic_add(&(lock).count,MAX_READERS); \
if (readers < 0) \
release_sem_etc((lock).sem,readers <= -MAX_READERS ? 1 : -readers,B_CAN_INTERRUPT); \
}
#endif /* LOCK_H */