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* File: pripcsem.h
* Description: named semaphores for interprocess
* synchronization
* Unrelated processes obtain access to a shared semaphore
* by specifying its name.
* Our goal is to support named semaphores on at least
* Unix and Win32 platforms. The implementation will use
* one of the three native semaphore APIs: POSIX, System V,
* and Win32.
* Because POSIX named semaphores have kernel persistence,
* we are forced to have a delete function in this API.
#ifndef pripcsem_h___
#define pripcsem_h___
#include "prtypes.h"
#include "prio.h"
* PRSem is an opaque structure that represents a named
* semaphore.
typedef struct PRSem PRSem;
* PR_OpenSemaphore --
* Create or open a named semaphore with the specified name.
* A handle to the semaphore is returned.
* If the named semaphore doesn't exist and the PR_SEM_CREATE
* flag is specified, the named semaphore is created. The
* created semaphore needs to be removed from the system with
* a PR_DeleteSemaphore call.
* If PR_SEM_CREATE is specified, the third argument is the
* access permission bits of the new semaphore (same
* interpretation as the mode argument to PR_Open) and the
* fourth argument is the initial value of the new semaphore.
* If PR_SEM_CREATE is not specified, the third and fourth
* arguments are ignored.
#define PR_SEM_CREATE 0x1 /* create if not exist */
#define PR_SEM_EXCL 0x2 /* fail if already exists */
NSPR_API(PRSem *) PR_OpenSemaphore(
const char *name, PRIntn flags, PRIntn mode, PRUintn value);
* PR_WaitSemaphore --
* If the value of the semaphore is > 0, decrement the value and return.
* If the value is 0, sleep until the value becomes > 0, then decrement
* the value and return.
* The "test and decrement" operation is performed atomically.
NSPR_API(PRStatus) PR_WaitSemaphore(PRSem *sem);
* PR_PostSemaphore --
* Increment the value of the named semaphore by 1.
NSPR_API(PRStatus) PR_PostSemaphore(PRSem *sem);
* PR_CloseSemaphore --
* Close a named semaphore handle.
NSPR_API(PRStatus) PR_CloseSemaphore(PRSem *sem);
* PR_DeleteSemaphore --
* Remove a named semaphore from the system.
NSPR_API(PRStatus) PR_DeleteSemaphore(const char *name);
#endif /* pripcsem_h___ */