summaryrefslogtreecommitdiff
path: root/net/py-kenosis/files/python2.3-Queue.py
diff options
context:
space:
mode:
Diffstat (limited to 'net/py-kenosis/files/python2.3-Queue.py')
-rw-r--r--net/py-kenosis/files/python2.3-Queue.py206
1 files changed, 206 insertions, 0 deletions
diff --git a/net/py-kenosis/files/python2.3-Queue.py b/net/py-kenosis/files/python2.3-Queue.py
new file mode 100644
index 000000000000..980aee619ddc
--- /dev/null
+++ b/net/py-kenosis/files/python2.3-Queue.py
@@ -0,0 +1,206 @@
+"""A multi-producer, multi-consumer queue."""
+
+from time import time as _time, sleep as _sleep
+
+__all__ = ['Empty', 'Full', 'Queue']
+
+class Empty(Exception):
+ "Exception raised by Queue.get(block=0)/get_nowait()."
+ pass
+
+class Full(Exception):
+ "Exception raised by Queue.put(block=0)/put_nowait()."
+ pass
+
+class Queue:
+ def __init__(self, maxsize=0):
+ """Initialize a queue object with a given maximum size.
+
+ If maxsize is <= 0, the queue size is infinite.
+ """
+ try:
+ import thread
+ except ImportError:
+ import dummy_thread as thread
+ self._init(maxsize)
+ self.mutex = thread.allocate_lock()
+ self.esema = thread.allocate_lock()
+ self.esema.acquire()
+ self.fsema = thread.allocate_lock()
+
+ def qsize(self):
+ """Return the approximate size of the queue (not reliable!)."""
+ self.mutex.acquire()
+ n = self._qsize()
+ self.mutex.release()
+ return n
+
+ def empty(self):
+ """Return True if the queue is empty, False otherwise (not reliable!)."""
+ self.mutex.acquire()
+ n = self._empty()
+ self.mutex.release()
+ return n
+
+ def full(self):
+ """Return True if the queue is full, False otherwise (not reliable!)."""
+ self.mutex.acquire()
+ n = self._full()
+ self.mutex.release()
+ return n
+
+ def put(self, item, block=True, timeout=None):
+ """Put an item into the queue.
+
+ If optional args 'block' is true and 'timeout' is None (the default),
+ block if necessary until a free slot is available. If 'timeout' is
+ a positive number, it blocks at most 'timeout' seconds and raises
+ the Full exception if no free slot was available within that time.
+ Otherwise ('block' is false), put an item on the queue if a free slot
+ is immediately available, else raise the Full exception ('timeout'
+ is ignored in that case).
+ """
+ if block:
+ if timeout is None:
+ # blocking, w/o timeout, i.e. forever
+ self.fsema.acquire()
+ elif timeout >= 0:
+ # waiting max. 'timeout' seconds.
+ # this code snipped is from threading.py: _Event.wait():
+ # Balancing act: We can't afford a pure busy loop, so we
+ # have to sleep; but if we sleep the whole timeout time,
+ # we'll be unresponsive. The scheme here sleeps very
+ # little at first, longer as time goes on, but never longer
+ # than 20 times per second (or the timeout time remaining).
+ delay = 0.0005 # 500 us -> initial delay of 1 ms
+ endtime = _time() + timeout
+ while True:
+ if self.fsema.acquire(0):
+ break
+ remaining = endtime - _time()
+ if remaining <= 0: #time is over and no slot was free
+ raise Full
+ delay = min(delay * 2, remaining, .05)
+ _sleep(delay) #reduce CPU usage by using a sleep
+ else:
+ raise ValueError("'timeout' must be a positive number")
+ elif not self.fsema.acquire(0):
+ raise Full
+ self.mutex.acquire()
+ release_fsema = True
+ try:
+ was_empty = self._empty()
+ self._put(item)
+ # If we fail before here, the empty state has
+ # not changed, so we can skip the release of esema
+ if was_empty:
+ self.esema.release()
+ # If we fail before here, the queue can not be full, so
+ # release_full_sema remains True
+ release_fsema = not self._full()
+ finally:
+ # Catching system level exceptions here (RecursionDepth,
+ # OutOfMemory, etc) - so do as little as possible in terms
+ # of Python calls.
+ if release_fsema:
+ self.fsema.release()
+ self.mutex.release()
+
+ def put_nowait(self, item):
+ """Put an item into the queue without blocking.
+
+ Only enqueue the item if a free slot is immediately available.
+ Otherwise raise the Full exception.
+ """
+ return self.put(item, False)
+
+ def get(self, block=True, timeout=None):
+ """Remove and return an item from the queue.
+
+ If optional args 'block' is true and 'timeout' is None (the default),
+ block if necessary until an item is available. If 'timeout' is
+ a positive number, it blocks at most 'timeout' seconds and raises
+ the Empty exception if no item was available within that time.
+ Otherwise ('block' is false), return an item if one is immediately
+ available, else raise the Empty exception ('timeout' is ignored
+ in that case).
+ """
+ if block:
+ if timeout is None:
+ # blocking, w/o timeout, i.e. forever
+ self.esema.acquire()
+ elif timeout >= 0:
+ # waiting max. 'timeout' seconds.
+ # this code snipped is from threading.py: _Event.wait():
+ # Balancing act: We can't afford a pure busy loop, so we
+ # have to sleep; but if we sleep the whole timeout time,
+ # we'll be unresponsive. The scheme here sleeps very
+ # little at first, longer as time goes on, but never longer
+ # than 20 times per second (or the timeout time remaining).
+ delay = 0.0005 # 500 us -> initial delay of 1 ms
+ endtime = _time() + timeout
+ while 1:
+ if self.esema.acquire(0):
+ break
+ remaining = endtime - _time()
+ if remaining <= 0: #time is over and no element arrived
+ raise Empty
+ delay = min(delay * 2, remaining, .05)
+ _sleep(delay) #reduce CPU usage by using a sleep
+ else:
+ raise ValueError("'timeout' must be a positive number")
+ elif not self.esema.acquire(0):
+ raise Empty
+ self.mutex.acquire()
+ release_esema = True
+ try:
+ was_full = self._full()
+ item = self._get()
+ # If we fail before here, the full state has
+ # not changed, so we can skip the release of fsema
+ if was_full:
+ self.fsema.release()
+ # Failure means empty state also unchanged - release_esema
+ # remains True.
+ release_esema = not self._empty()
+ finally:
+ if release_esema:
+ self.esema.release()
+ self.mutex.release()
+ return item
+
+ def get_nowait(self):
+ """Remove and return an item from the queue without blocking.
+
+ Only get an item if one is immediately available. Otherwise
+ raise the Empty exception.
+ """
+ return self.get(False)
+
+ # Override these methods to implement other queue organizations
+ # (e.g. stack or priority queue).
+ # These will only be called with appropriate locks held
+
+ # Initialize the queue representation
+ def _init(self, maxsize):
+ self.maxsize = maxsize
+ self.queue = []
+
+ def _qsize(self):
+ return len(self.queue)
+
+ # Check whether the queue is empty
+ def _empty(self):
+ return not self.queue
+
+ # Check whether the queue is full
+ def _full(self):
+ return self.maxsize > 0 and len(self.queue) == self.maxsize
+
+ # Put a new item in the queue
+ def _put(self, item):
+ self.queue.append(item)
+
+ # Get an item from the queue
+ def _get(self):
+ return self.queue.pop(0)