A POSIC semaphore.
| 50 | c_struct_timespec_p = POINTER(c_struct_timespec) |
| 51 | |
| 52 | class Sem(object): |
| 53 | """A POSIC semaphore.""" |
| 54 | O_CREAT = 0x0200 # create if nonexistent |
| 55 | O_EXCL = 0x0800 # error if already exists |
| 56 | |
| 57 | _clock_gettime = get_func("libc.so", "clock_gettime", None, (c_int32, c_struct_timespec_p)) |
| 58 | |
| 59 | _error = get_func("libc.so", "__error", POINTER(c_int), ()) |
| 60 | |
| 61 | _sem_close = get_func("libc.so", "sem_close", c_int, (c_sem_p,)) |
| 62 | _sem_destroy = get_func("libc.so", "sem_destroy", c_int, (c_sem_p,)) |
| 63 | _sem_getvalue = get_func("libc.so", "sem_getvalue", c_int, (c_sem_p, c_int_p)) |
| 64 | _sem_init = get_func("libc.so", "sem_init", c_int, (c_sem_p, c_int, c_uint)) |
| 65 | _sem_open = get_func("libc.so", "sem_open", c_sem_p, (c_char_p, c_int)) |
| 66 | _sem_post = get_func("libc.so", "sem_post", c_int, (c_sem_p,)) |
| 67 | _sem_timedwait = get_func("libc.so", "sem_timedwait", c_int, (c_sem_p, c_struct_timespec_p)) |
| 68 | _sem_trywait = get_func("libc.so", "sem_trywait", c_int, (c_sem_p,)) |
| 69 | _sem_unlink = get_func("libc.so", "sem_unlink", c_int, (c_char_p,)) |
| 70 | _sem_wait = get_func("libc.so", "sem_wait", c_int, (c_sem_p,)) |
| 71 | |
| 72 | def __init__(self, value=1, name=None, oflags=0x0200): |
| 73 | """Create a semaphore with initial value, possible name and flags.""" |
| 74 | if name: |
| 75 | self.sem = None |
| 76 | self.sem_p = self._sem_open("/%s" % name, oflags) |
| 77 | if not self.sem_p: |
| 78 | raise SemError() |
| 79 | else: |
| 80 | self.sem = c_sem() |
| 81 | self.sem_p = c_sem_p(self.sem) |
| 82 | if self._sem_init(self.sem_p, 0, value): |
| 83 | raise SemError() |
| 84 | |
| 85 | def __del__(self): |
| 86 | """Cleanup the semaphore.""" |
| 87 | if self.sem is None: |
| 88 | res = self._sem_close(self.sem_p) |
| 89 | else: |
| 90 | res = self._sem_destroy(self.sem_p) |
| 91 | if res: |
| 92 | raise SemError() |
| 93 | |
| 94 | def __len__(self): |
| 95 | """The current value of the semaphore.""" |
| 96 | return self.getvalue() |
| 97 | |
| 98 | def __enter__(self): |
| 99 | """Decrement the value of the semaphore, waiting if required.""" |
| 100 | self.wait() |
| 101 | return self |
| 102 | |
| 103 | def __exit__(self, exc_type, exc_value, traceback): |
| 104 | """Increment the value of the semaphore.""" |
| 105 | self.post() |
| 106 | |
| 107 | def acquire(self, blocking=True): |
| 108 | """Decrement the value of the semaphore, block if requested and |
| 109 | required.""" |