Guido van Rossum | 4acc25b | 2000-02-02 15:10:15 +0000 | [diff] [blame] | 1 | """A multi-producer, multi-consumer queue.""" |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 2 | |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 3 | from time import time as _time, sleep as _sleep |
Raymond Hettinger | 756b3f3 | 2004-01-29 06:37:52 +0000 | [diff] [blame] | 4 | from collections import deque |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 5 | |
Brett Cannon | b42bb5a | 2003-07-01 05:34:27 +0000 | [diff] [blame] | 6 | __all__ = ['Empty', 'Full', 'Queue'] |
| 7 | |
Tim Peters | b8c9417 | 2001-01-15 22:53:46 +0000 | [diff] [blame] | 8 | class Empty(Exception): |
| 9 | "Exception raised by Queue.get(block=0)/get_nowait()." |
| 10 | pass |
| 11 | |
| 12 | class Full(Exception): |
| 13 | "Exception raised by Queue.put(block=0)/put_nowait()." |
| 14 | pass |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 15 | |
| 16 | class Queue: |
Guido van Rossum | a41c691 | 1999-09-09 14:54:28 +0000 | [diff] [blame] | 17 | def __init__(self, maxsize=0): |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 18 | """Initialize a queue object with a given maximum size. |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 19 | |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 20 | If maxsize is <= 0, the queue size is infinite. |
| 21 | """ |
Guido van Rossum | a093424 | 2002-12-30 22:36:09 +0000 | [diff] [blame] | 22 | try: |
| 23 | import thread |
| 24 | except ImportError: |
| 25 | import dummy_thread as thread |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 26 | self._init(maxsize) |
| 27 | self.mutex = thread.allocate_lock() |
| 28 | self.esema = thread.allocate_lock() |
Guido van Rossum | 7e6d18c | 1998-04-29 14:29:32 +0000 | [diff] [blame] | 29 | self.esema.acquire() |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 30 | self.fsema = thread.allocate_lock() |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 31 | |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 32 | def qsize(self): |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 33 | """Return the approximate size of the queue (not reliable!).""" |
Guido van Rossum | 7e6d18c | 1998-04-29 14:29:32 +0000 | [diff] [blame] | 34 | self.mutex.acquire() |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 35 | n = self._qsize() |
Guido van Rossum | 7e6d18c | 1998-04-29 14:29:32 +0000 | [diff] [blame] | 36 | self.mutex.release() |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 37 | return n |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 38 | |
| 39 | def empty(self): |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 40 | """Return True if the queue is empty, False otherwise (not reliable!).""" |
Guido van Rossum | 7e6d18c | 1998-04-29 14:29:32 +0000 | [diff] [blame] | 41 | self.mutex.acquire() |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 42 | n = self._empty() |
Guido van Rossum | 7e6d18c | 1998-04-29 14:29:32 +0000 | [diff] [blame] | 43 | self.mutex.release() |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 44 | return n |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 45 | |
| 46 | def full(self): |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 47 | """Return True if the queue is full, False otherwise (not reliable!).""" |
Guido van Rossum | 7e6d18c | 1998-04-29 14:29:32 +0000 | [diff] [blame] | 48 | self.mutex.acquire() |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 49 | n = self._full() |
Guido van Rossum | 7e6d18c | 1998-04-29 14:29:32 +0000 | [diff] [blame] | 50 | self.mutex.release() |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 51 | return n |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 52 | |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 53 | def put(self, item, block=True, timeout=None): |
Guido van Rossum | c09e6b1 | 1998-04-09 14:25:32 +0000 | [diff] [blame] | 54 | """Put an item into the queue. |
| 55 | |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 56 | If optional args 'block' is true and 'timeout' is None (the default), |
| 57 | block if necessary until a free slot is available. If 'timeout' is |
| 58 | a positive number, it blocks at most 'timeout' seconds and raises |
| 59 | the Full exception if no free slot was available within that time. |
| 60 | Otherwise ('block' is false), put an item on the queue if a free slot |
| 61 | is immediately available, else raise the Full exception ('timeout' |
| 62 | is ignored in that case). |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 63 | """ |
| 64 | if block: |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 65 | if timeout is None: |
| 66 | # blocking, w/o timeout, i.e. forever |
| 67 | self.fsema.acquire() |
| 68 | elif timeout >= 0: |
| 69 | # waiting max. 'timeout' seconds. |
| 70 | # this code snipped is from threading.py: _Event.wait(): |
| 71 | # Balancing act: We can't afford a pure busy loop, so we |
| 72 | # have to sleep; but if we sleep the whole timeout time, |
| 73 | # we'll be unresponsive. The scheme here sleeps very |
| 74 | # little at first, longer as time goes on, but never longer |
| 75 | # than 20 times per second (or the timeout time remaining). |
| 76 | delay = 0.0005 # 500 us -> initial delay of 1 ms |
| 77 | endtime = _time() + timeout |
| 78 | while True: |
| 79 | if self.fsema.acquire(0): |
| 80 | break |
| 81 | remaining = endtime - _time() |
| 82 | if remaining <= 0: #time is over and no slot was free |
| 83 | raise Full |
| 84 | delay = min(delay * 2, remaining, .05) |
| 85 | _sleep(delay) #reduce CPU usage by using a sleep |
| 86 | else: |
| 87 | raise ValueError("'timeout' must be a positive number") |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 88 | elif not self.fsema.acquire(0): |
| 89 | raise Full |
Guido van Rossum | 7e6d18c | 1998-04-29 14:29:32 +0000 | [diff] [blame] | 90 | self.mutex.acquire() |
Mark Hammond | 3b959db | 2002-04-19 00:11:32 +0000 | [diff] [blame] | 91 | release_fsema = True |
| 92 | try: |
| 93 | was_empty = self._empty() |
| 94 | self._put(item) |
| 95 | # If we fail before here, the empty state has |
| 96 | # not changed, so we can skip the release of esema |
| 97 | if was_empty: |
| 98 | self.esema.release() |
| 99 | # If we fail before here, the queue can not be full, so |
| 100 | # release_full_sema remains True |
| 101 | release_fsema = not self._full() |
| 102 | finally: |
| 103 | # Catching system level exceptions here (RecursionDepth, |
| 104 | # OutOfMemory, etc) - so do as little as possible in terms |
| 105 | # of Python calls. |
| 106 | if release_fsema: |
| 107 | self.fsema.release() |
| 108 | self.mutex.release() |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 109 | |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 110 | def put_nowait(self, item): |
| 111 | """Put an item into the queue without blocking. |
Guido van Rossum | c09e6b1 | 1998-04-09 14:25:32 +0000 | [diff] [blame] | 112 | |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 113 | Only enqueue the item if a free slot is immediately available. |
| 114 | Otherwise raise the Full exception. |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 115 | """ |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 116 | return self.put(item, False) |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 117 | |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 118 | def get(self, block=True, timeout=None): |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 119 | """Remove and return an item from the queue. |
Guido van Rossum | c09e6b1 | 1998-04-09 14:25:32 +0000 | [diff] [blame] | 120 | |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 121 | If optional args 'block' is true and 'timeout' is None (the default), |
| 122 | block if necessary until an item is available. If 'timeout' is |
| 123 | a positive number, it blocks at most 'timeout' seconds and raises |
| 124 | the Empty exception if no item was available within that time. |
| 125 | Otherwise ('block' is false), return an item if one is immediately |
| 126 | available, else raise the Empty exception ('timeout' is ignored |
| 127 | in that case). |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 128 | """ |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 129 | if block: |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 130 | if timeout is None: |
| 131 | # blocking, w/o timeout, i.e. forever |
| 132 | self.esema.acquire() |
| 133 | elif timeout >= 0: |
| 134 | # waiting max. 'timeout' seconds. |
| 135 | # this code snipped is from threading.py: _Event.wait(): |
| 136 | # Balancing act: We can't afford a pure busy loop, so we |
| 137 | # have to sleep; but if we sleep the whole timeout time, |
| 138 | # we'll be unresponsive. The scheme here sleeps very |
| 139 | # little at first, longer as time goes on, but never longer |
| 140 | # than 20 times per second (or the timeout time remaining). |
| 141 | delay = 0.0005 # 500 us -> initial delay of 1 ms |
| 142 | endtime = _time() + timeout |
| 143 | while 1: |
| 144 | if self.esema.acquire(0): |
| 145 | break |
| 146 | remaining = endtime - _time() |
| 147 | if remaining <= 0: #time is over and no element arrived |
| 148 | raise Empty |
| 149 | delay = min(delay * 2, remaining, .05) |
| 150 | _sleep(delay) #reduce CPU usage by using a sleep |
| 151 | else: |
| 152 | raise ValueError("'timeout' must be a positive number") |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 153 | elif not self.esema.acquire(0): |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 154 | raise Empty |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 155 | self.mutex.acquire() |
Mark Hammond | 3b959db | 2002-04-19 00:11:32 +0000 | [diff] [blame] | 156 | release_esema = True |
| 157 | try: |
| 158 | was_full = self._full() |
| 159 | item = self._get() |
| 160 | # If we fail before here, the full state has |
| 161 | # not changed, so we can skip the release of fsema |
| 162 | if was_full: |
| 163 | self.fsema.release() |
| 164 | # Failure means empty state also unchanged - release_esema |
| 165 | # remains True. |
| 166 | release_esema = not self._empty() |
| 167 | finally: |
| 168 | if release_esema: |
| 169 | self.esema.release() |
| 170 | self.mutex.release() |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 171 | return item |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 172 | |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 173 | def get_nowait(self): |
| 174 | """Remove and return an item from the queue without blocking. |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 175 | |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 176 | Only get an item if one is immediately available. Otherwise |
Guido van Rossum | 9e1721f | 1999-02-08 18:34:01 +0000 | [diff] [blame] | 177 | raise the Empty exception. |
| 178 | """ |
Martin v. Löwis | 77ac429 | 2002-10-15 15:11:13 +0000 | [diff] [blame] | 179 | return self.get(False) |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 180 | |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 181 | # Override these methods to implement other queue organizations |
| 182 | # (e.g. stack or priority queue). |
| 183 | # These will only be called with appropriate locks held |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 184 | |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 185 | # Initialize the queue representation |
| 186 | def _init(self, maxsize): |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 187 | self.maxsize = maxsize |
Raymond Hettinger | 756b3f3 | 2004-01-29 06:37:52 +0000 | [diff] [blame] | 188 | self.queue = deque() |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 189 | |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 190 | def _qsize(self): |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 191 | return len(self.queue) |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 192 | |
Jeremy Hylton | a05e293 | 2000-06-28 14:48:01 +0000 | [diff] [blame] | 193 | # Check whether the queue is empty |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 194 | def _empty(self): |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 195 | return not self.queue |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 196 | |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 197 | # Check whether the queue is full |
| 198 | def _full(self): |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 199 | return self.maxsize > 0 and len(self.queue) == self.maxsize |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 200 | |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 201 | # Put a new item in the queue |
| 202 | def _put(self, item): |
Guido van Rossum | 45e2fbc | 1998-03-26 21:13:24 +0000 | [diff] [blame] | 203 | self.queue.append(item) |
Guido van Rossum | 9022fce | 1992-08-25 12:30:44 +0000 | [diff] [blame] | 204 | |
Barry Warsaw | 3d96d52 | 1997-11-20 19:56:38 +0000 | [diff] [blame] | 205 | # Get an item from the queue |
| 206 | def _get(self): |
Raymond Hettinger | 756b3f3 | 2004-01-29 06:37:52 +0000 | [diff] [blame] | 207 | return self.queue.popleft() |