nsprpub/pr/include/pripcsem.h

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  37
  38 /*
  39  * File: pripcsem.h
  40  *
  41  * Description: named semaphores for interprocess
  42  * synchronization
  43  *
  44  * Unrelated processes obtain access to a shared semaphore
  45  * by specifying its name.
  46  *
  47  * Our goal is to support named semaphores on at least
  48  * Unix and Win32 platforms.  The implementation will use
  49  * one of the three native semaphore APIs: POSIX, System V,
  50  * and Win32.
  51  *
  52  * Because POSIX named semaphores have kernel persistence,
  53  * we are forced to have a delete function in this API.
  54  */
  55
  56 #ifndef pripcsem_h___
  57 #define pripcsem_h___
  58
  59 #include "prtypes.h"
  60 #include "prio.h"
  61
  62 PR_BEGIN_EXTERN_C
  63
  64 /*
  65  * PRSem is an opaque structure that represents a named
  66  * semaphore.
  67  */
  68 typedef struct PRSem PRSem;
  69
  70 /*
  71  * PR_OpenSemaphore --
  72  *
  73  * Create or open a named semaphore with the specified name.
  74  * A handle to the semaphore is returned.
  75  *
  76  * If the named semaphore doesn't exist and the PR_SEM_CREATE
  77  * flag is specified, the named semaphore is created.  The
  78  * created semaphore needs to be removed from the system with
  79  * a PR_DeleteSemaphore call.
  80  *
  81  * If PR_SEM_CREATE is specified, the third argument is the
  82  * access permission bits of the new semaphore (same
  83  * interpretation as the mode argument to PR_Open) and the
  84  * fourth argument is the initial value of the new semaphore.
  85  * If PR_SEM_CREATE is not specified, the third and fourth
  86  * arguments are ignored.
  87  */
  88
  89 #define PR_SEM_CREATE 0x1  /* create if not exist */
  90 #define PR_SEM_EXCL   0x2  /* fail if already exists */
  91
  92 NSPR_API(PRSem *) PR_OpenSemaphore(
  93     const char *name, PRIntn flags, PRIntn mode, PRUintn value);
  94
  95 /*
  96  * PR_WaitSemaphore --
  97  *
  98  * If the value of the semaphore is > 0, decrement the value and return.
  99  * If the value is 0, sleep until the value becomes > 0, then decrement
 100  * the value and return.
 101  *
 102  * The "test and decrement" operation is performed atomically.
 103  */
 104
 105 NSPR_API(PRStatus) PR_WaitSemaphore(PRSem *sem);
 106
 107 /*
 108  * PR_PostSemaphore --
 109  *
 110  * Increment the value of the named semaphore by 1.
 111  */
 112
 113 NSPR_API(PRStatus) PR_PostSemaphore(PRSem *sem);
 114
 115 /*
 116  * PR_CloseSemaphore --
 117  *
 118  * Close a named semaphore handle.
 119  */
 120
 121 NSPR_API(PRStatus) PR_CloseSemaphore(PRSem *sem);
 122
 123 /*
 124  * PR_DeleteSemaphore --
 125  *
 126  * Remove a named semaphore from the system.
 127  */
 128
 129 NSPR_API(PRStatus) PR_DeleteSemaphore(const char *name);
 130
 131 PR_END_EXTERN_C
 132
 133 #endif /* pripcsem_h___ */