Home | History | Annotate | Download | only in nspr 
      1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /*
      3  * The contents of this file are subject to the Mozilla Public
      4  * License Version 1.1 (the "License"); you may not use this file
      5  * except in compliance with the License. You may obtain a copy of
      6  * the License at http://www.mozilla.org/MPL/
      7  *
      8  * Software distributed under the License is distributed on an "AS
      9  * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
     10  * implied. See the License for the specific language governing
     11  * rights and limitations under the License.
     12  *
     13  * The Original Code is the Netscape Portable Runtime (NSPR).
     14  *
     15  * The Initial Developer of the Original Code is Netscape
     16  * Communications Corporation.  Portions created by Netscape are
     17  * Copyright (C) 1999-2000 Netscape Communications Corporation.  All
     18  * Rights Reserved.
     19  *
     20  * Contributor(s):
     21  *
     22  * Alternatively, the contents of this file may be used under the
     23  * terms of the GNU General Public License Version 2 or later (the
     24  * "GPL"), in which case the provisions of the GPL are applicable
     25  * instead of those above.  If you wish to allow use of your
     26  * version of this file only under the terms of the GPL and not to
     27  * allow others to use your version of this file under the MPL,
     28  * indicate your decision by deleting the provisions above and
     29  * replace them with the notice and other provisions required by
     30  * the GPL.  If you do not delete the provisions above, a recipient
     31  * may use your version of this file under either the MPL or the
     32  * GPL.
     33  */
     34 
     35 /*
     36  * File: pripcsem.h
     37  *
     38  * Description: named semaphores for interprocess
     39  * synchronization
     40  *
     41  * Unrelated processes obtain access to a shared semaphore
     42  * by specifying its name.
     43  *
     44  * Our goal is to support named semaphores on at least
     45  * Unix and Win32 platforms.  The implementation will use
     46  * one of the three native semaphore APIs: POSIX, System V,
     47  * and Win32.
     48  *
     49  * Because POSIX named semaphores have kernel persistence,
     50  * we are forced to have a delete function in this API.
     51  */
     52 
     53 #ifndef pripcsem_h___
     54 #define pripcsem_h___
     55 
     56 #include "prtypes.h"
     57 #include "prio.h"
     58 
     59 PR_BEGIN_EXTERN_C
     60 
     61 /*
     62  * PRSem is an opaque structure that represents a named
     63  * semaphore.
     64  */
     65 typedef struct PRSem PRSem;
     66 
     67 /*
     68  * PR_OpenSemaphore --
     69  *
     70  * Create or open a named semaphore with the specified name.
     71  * A handle to the semaphore is returned.
     72  *
     73  * If the named semaphore doesn't exist and the PR_SEM_CREATE
     74  * flag is specified, the named semaphore is created.  The
     75  * created semaphore needs to be removed from the system with
     76  * a PR_DeleteSemaphore call.
     77  *
     78  * If PR_SEM_CREATE is specified, the third argument is the
     79  * access permission bits of the new semaphore (same
     80  * interpretation as the mode argument to PR_Open) and the
     81  * fourth argument is the initial value of the new semaphore.
     82  * If PR_SEM_CREATE is not specified, the third and fourth
     83  * arguments are ignored.
     84  */
     85 
     86 #define PR_SEM_CREATE 0x1  /* create if not exist */
     87 #define PR_SEM_EXCL   0x2  /* fail if already exists */
     88 
     89 NSPR_API(PRSem *) PR_OpenSemaphore(
     90     const char *name, PRIntn flags, PRIntn mode, PRUintn value);
     91 
     92 /*
     93  * PR_WaitSemaphore --
     94  *
     95  * If the value of the semaphore is > 0, decrement the value and return.
     96  * If the value is 0, sleep until the value becomes > 0, then decrement
     97  * the value and return.
     98  *
     99  * The "test and decrement" operation is performed atomically.
    100  */
    101 
    102 NSPR_API(PRStatus) PR_WaitSemaphore(PRSem *sem);
    103 
    104 /*
    105  * PR_PostSemaphore --
    106  *
    107  * Increment the value of the named semaphore by 1.
    108  */
    109 
    110 NSPR_API(PRStatus) PR_PostSemaphore(PRSem *sem);
    111 
    112 /*
    113  * PR_CloseSemaphore --
    114  *
    115  * Close a named semaphore handle.
    116  */
    117 
    118 NSPR_API(PRStatus) PR_CloseSemaphore(PRSem *sem);
    119 
    120 /*
    121  * PR_DeleteSemaphore --
    122  *
    123  * Remove a named semaphore from the system.
    124  */
    125 
    126 NSPR_API(PRStatus) PR_DeleteSemaphore(const char *name);
    127 
    128 PR_END_EXTERN_C
    129 
    130 #endif /* pripcsem_h___ */
    131