| 1 | /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ |
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| 2 | /* This Source Code Form is subject to the terms of the Mozilla Public |
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| 3 | * License, v. 2.0. If a copy of the MPL was not distributed with this |
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| 4 | * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
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| 5 | |
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| 6 | /* |
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| 7 | * File: pripcsem.h |
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| 8 | * |
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| 9 | * Description: named semaphores for interprocess |
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| 10 | * synchronization |
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| 11 | * |
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| 12 | * Unrelated processes obtain access to a shared semaphore |
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| 13 | * by specifying its name. |
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| 14 | * |
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| 15 | * Our goal is to support named semaphores on at least |
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| 16 | * Unix and Win32 platforms. The implementation will use |
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| 17 | * one of the three native semaphore APIs: POSIX, System V, |
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| 18 | * and Win32. |
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| 19 | * |
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| 20 | * Because POSIX named semaphores have kernel persistence, |
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| 21 | * we are forced to have a delete function in this API. |
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| 22 | */ |
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| 23 | |
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| 24 | #ifndef pripcsem_h___ |
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| 25 | #define pripcsem_h___ |
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| 26 | |
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| 27 | #include "prtypes.h" |
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| 28 | #include "prio.h" |
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| 29 | |
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| 30 | PR_BEGIN_EXTERN_C |
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| 31 | |
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| 32 | /* |
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| 33 | * PRSem is an opaque structure that represents a named |
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| 34 | * semaphore. |
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| 35 | */ |
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| 36 | typedef struct PRSem PRSem; |
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| 37 | |
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| 38 | /* |
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| 39 | * PR_OpenSemaphore -- |
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| 40 | * |
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| 41 | * Create or open a named semaphore with the specified name. |
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| 42 | * A handle to the semaphore is returned. |
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| 43 | * |
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| 44 | * If the named semaphore doesn't exist and the PR_SEM_CREATE |
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| 45 | * flag is specified, the named semaphore is created. The |
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| 46 | * created semaphore needs to be removed from the system with |
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| 47 | * a PR_DeleteSemaphore call. |
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| 48 | * |
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| 49 | * If PR_SEM_CREATE is specified, the third argument is the |
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| 50 | * access permission bits of the new semaphore (same |
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| 51 | * interpretation as the mode argument to PR_Open) and the |
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| 52 | * fourth argument is the initial value of the new semaphore. |
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| 53 | * If PR_SEM_CREATE is not specified, the third and fourth |
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| 54 | * arguments are ignored. |
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| 55 | */ |
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| 56 | |
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| 57 | #define PR_SEM_CREATE 0x1 /* create if not exist */ |
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| 58 | #define PR_SEM_EXCL 0x2 /* fail if already exists */ |
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| 59 | |
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| 60 | NSPR_API(PRSem *) PR_OpenSemaphore( |
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| 61 | const char *name, PRIntn flags, PRIntn mode, PRUintn value); |
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| 62 | |
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| 63 | /* |
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| 64 | * PR_WaitSemaphore -- |
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| 65 | * |
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| 66 | * If the value of the semaphore is > 0, decrement the value and return. |
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| 67 | * If the value is 0, sleep until the value becomes > 0, then decrement |
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| 68 | * the value and return. |
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| 69 | * |
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| 70 | * The "test and decrement" operation is performed atomically. |
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| 71 | */ |
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| 72 | |
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| 73 | NSPR_API(PRStatus) PR_WaitSemaphore(PRSem *sem); |
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| 74 | |
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| 75 | /* |
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| 76 | * PR_PostSemaphore -- |
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| 77 | * |
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| 78 | * Increment the value of the named semaphore by 1. |
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| 79 | */ |
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| 80 | |
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| 81 | NSPR_API(PRStatus) PR_PostSemaphore(PRSem *sem); |
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| 82 | |
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| 83 | /* |
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| 84 | * PR_CloseSemaphore -- |
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| 85 | * |
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| 86 | * Close a named semaphore handle. |
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| 87 | */ |
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| 88 | |
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| 89 | NSPR_API(PRStatus) PR_CloseSemaphore(PRSem *sem); |
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| 90 | |
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| 91 | /* |
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| 92 | * PR_DeleteSemaphore -- |
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| 93 | * |
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| 94 | * Remove a named semaphore from the system. |
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| 95 | */ |
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| 96 | |
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| 97 | NSPR_API(PRStatus) PR_DeleteSemaphore(const char *name); |
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| 98 | |
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| 99 | PR_END_EXTERN_C |
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| 100 | |
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| 101 | #endif /* pripcsem_h___ */ |
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| 102 | |
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