|
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 #ifndef prsem_h___ |
|
7 #define prsem_h___ |
|
8 |
|
9 /* |
|
10 ** API for counting semaphores. Semaphores are counting synchronizing |
|
11 ** variables based on a lock and a condition variable. They are lightweight |
|
12 ** contention control for a given count of resources. |
|
13 */ |
|
14 #include "prtypes.h" |
|
15 |
|
16 PR_BEGIN_EXTERN_C |
|
17 |
|
18 typedef struct PRSemaphore PRSemaphore; |
|
19 |
|
20 /* |
|
21 ** Create a new semaphore object. |
|
22 */ |
|
23 NSPR_API(PRSemaphore*) PR_NewSem(PRUintn value); |
|
24 |
|
25 /* |
|
26 ** Destroy the given semaphore object. |
|
27 ** |
|
28 */ |
|
29 NSPR_API(void) PR_DestroySem(PRSemaphore *sem); |
|
30 |
|
31 /* |
|
32 ** Wait on a Semaphore. |
|
33 ** |
|
34 ** This routine allows a calling thread to wait or proceed depending upon the |
|
35 ** state of the semahore sem. The thread can proceed only if the counter value |
|
36 ** of the semaphore sem is currently greater than 0. If the value of semaphore |
|
37 ** sem is positive, it is decremented by one and the routine returns immediately |
|
38 ** allowing the calling thread to continue. If the value of semaphore sem is 0, |
|
39 ** the calling thread blocks awaiting the semaphore to be released by another |
|
40 ** thread. |
|
41 ** |
|
42 ** This routine can return PR_PENDING_INTERRUPT if the waiting thread |
|
43 ** has been interrupted. |
|
44 */ |
|
45 NSPR_API(PRStatus) PR_WaitSem(PRSemaphore *sem); |
|
46 |
|
47 /* |
|
48 ** This routine increments the counter value of the semaphore. If other threads |
|
49 ** are blocked for the semaphore, then the scheduler will determine which ONE |
|
50 ** thread will be unblocked. |
|
51 */ |
|
52 NSPR_API(void) PR_PostSem(PRSemaphore *sem); |
|
53 |
|
54 /* |
|
55 ** Returns the value of the semaphore referenced by sem without affecting |
|
56 ** the state of the semaphore. The value represents the semaphore vaule |
|
57 F** at the time of the call, but may not be the actual value when the |
|
58 ** caller inspects it. |
|
59 */ |
|
60 NSPR_API(PRUintn) PR_GetValueSem(PRSemaphore *sem); |
|
61 |
|
62 PR_END_EXTERN_C |
|
63 |
|
64 #endif /* prsem_h___ */ |