mirror of
https://github.com/python/cpython.git
synced 2024-11-24 18:34:43 +08:00
139 lines
4.0 KiB
Python
139 lines
4.0 KiB
Python
"""A multi-producer, multi-consumer queue."""
|
|
|
|
# define this exception to be compatible with Python 1.5's class
|
|
# exceptions, but also when -X option is used.
|
|
try:
|
|
class Empty(Exception):
|
|
pass
|
|
class Full(Exception):
|
|
pass
|
|
except TypeError:
|
|
# string based exceptions
|
|
# exception raised by get(block=0)/get_nowait()
|
|
Empty = 'Queue.Empty'
|
|
# exception raised by put(block=0)/put_nowait()
|
|
Full = 'Queue.Full'
|
|
|
|
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.
|
|
"""
|
|
import 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 1 if the queue is empty, 0 otherwise (not reliable!)."""
|
|
self.mutex.acquire()
|
|
n = self._empty()
|
|
self.mutex.release()
|
|
return n
|
|
|
|
def full(self):
|
|
"""Return 1 if the queue is full, 0 otherwise (not reliable!)."""
|
|
self.mutex.acquire()
|
|
n = self._full()
|
|
self.mutex.release()
|
|
return n
|
|
|
|
def put(self, item, block=1):
|
|
"""Put an item into the queue.
|
|
|
|
If optional arg 'block' is 1 (the default), block if
|
|
necessary until a free slot is available. Otherwise (block
|
|
is 0), put an item on the queue if a free slot is immediately
|
|
available, else raise the Full exception.
|
|
"""
|
|
if block:
|
|
self.fsema.acquire()
|
|
elif not self.fsema.acquire(0):
|
|
raise Full
|
|
self.mutex.acquire()
|
|
was_empty = self._empty()
|
|
self._put(item)
|
|
if was_empty:
|
|
self.esema.release()
|
|
if not self._full():
|
|
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, 0)
|
|
|
|
def get(self, block=1):
|
|
"""Remove and return an item from the queue.
|
|
|
|
If optional arg 'block' is 1 (the default), block if
|
|
necessary until an item is available. Otherwise (block is 0),
|
|
return an item if one is immediately available, else raise the
|
|
Empty exception.
|
|
"""
|
|
if block:
|
|
self.esema.acquire()
|
|
elif not self.esema.acquire(0):
|
|
raise Empty
|
|
self.mutex.acquire()
|
|
was_full = self._full()
|
|
item = self._get()
|
|
if was_full:
|
|
self.fsema.release()
|
|
if not self._empty():
|
|
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(0)
|
|
|
|
# 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):
|
|
item = self.queue[0]
|
|
del self.queue[0]
|
|
return item
|