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pripcsem.h (2640B)

      1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* This Source Code Form is subject to the terms of the Mozilla Public
      3 * License, v. 2.0. If a copy of the MPL was not distributed with this
      4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      5 
      6 /*
      7 * File: pripcsem.h
      8 *
      9 * Description: named semaphores for interprocess
     10 * synchronization
     11 *
     12 * Unrelated processes obtain access to a shared semaphore
     13 * by specifying its name.
     14 *
     15 * Our goal is to support named semaphores on at least
     16 * Unix and Win32 platforms.  The implementation will use
     17 * one of the three native semaphore APIs: POSIX, System V,
     18 * and Win32.
     19 *
     20 * Because POSIX named semaphores have kernel persistence,
     21 * we are forced to have a delete function in this API.
     22 */
     23 
     24 #ifndef pripcsem_h___
     25 #define pripcsem_h___
     26 
     27 #include "prtypes.h"
     28 #include "prio.h"
     29 
     30 PR_BEGIN_EXTERN_C
     31 
     32 /*
     33 * PRSem is an opaque structure that represents a named
     34 * semaphore.
     35 */
     36 typedef struct PRSem PRSem;
     37 
     38 /*
     39 * PR_OpenSemaphore --
     40 *
     41 * Create or open a named semaphore with the specified name.
     42 * A handle to the semaphore is returned.
     43 *
     44 * If the named semaphore doesn't exist and the PR_SEM_CREATE
     45 * flag is specified, the named semaphore is created.  The
     46 * created semaphore needs to be removed from the system with
     47 * a PR_DeleteSemaphore call.
     48 *
     49 * If PR_SEM_CREATE is specified, the third argument is the
     50 * access permission bits of the new semaphore (same
     51 * interpretation as the mode argument to PR_Open) and the
     52 * fourth argument is the initial value of the new semaphore.
     53 * If PR_SEM_CREATE is not specified, the third and fourth
     54 * arguments are ignored.
     55 */
     56 
     57 #define PR_SEM_CREATE 0x1  /* create if not exist */
     58 #define PR_SEM_EXCL   0x2  /* fail if already exists */
     59 
     60 NSPR_API(PRSem *) PR_OpenSemaphore(
     61    const char *name, PRIntn flags, PRIntn mode, PRUintn value);
     62 
     63 /*
     64 * PR_WaitSemaphore --
     65 *
     66 * If the value of the semaphore is > 0, decrement the value and return.
     67 * If the value is 0, sleep until the value becomes > 0, then decrement
     68 * the value and return.
     69 *
     70 * The "test and decrement" operation is performed atomically.
     71 */
     72 
     73 NSPR_API(PRStatus) PR_WaitSemaphore(PRSem *sem);
     74 
     75 /*
     76 * PR_PostSemaphore --
     77 *
     78 * Increment the value of the named semaphore by 1.
     79 */
     80 
     81 NSPR_API(PRStatus) PR_PostSemaphore(PRSem *sem);
     82 
     83 /*
     84 * PR_CloseSemaphore --
     85 *
     86 * Close a named semaphore handle.
     87 */
     88 
     89 NSPR_API(PRStatus) PR_CloseSemaphore(PRSem *sem);
     90 
     91 /*
     92 * PR_DeleteSemaphore --
     93 *
     94 * Remove a named semaphore from the system.
     95 */
     96 
     97 NSPR_API(PRStatus) PR_DeleteSemaphore(const char *name);
     98 
     99 PR_END_EXTERN_C
    100 
    101 #endif /* pripcsem_h___ */