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___ */
102