mirror of
https://github.com/python/cpython.git
synced 2025-10-29 20:51:26 +00:00
121 lines
2.9 KiB
Python
121 lines
2.9 KiB
Python
# A multi-producer, multi-consumer queue.
|
|
|
|
Empty = 'Queue.Empty' # Exception raised by get_nowait()
|
|
|
|
class Queue:
|
|
|
|
# Initialize a queue object with a given maximum size
|
|
# (If maxsize is <= 0, the maximum size is infinite)
|
|
def __init__(self, maxsize):
|
|
import thread
|
|
self._init(maxsize)
|
|
self.mutex = thread.allocate_lock()
|
|
self.esema = thread.allocate_lock()
|
|
self.esema.acquire_lock()
|
|
self.fsema = thread.allocate_lock()
|
|
|
|
# Get an approximation of the queue size (not reliable!)
|
|
def qsize(self):
|
|
self.mutex.acquire_lock()
|
|
n = self._qsize()
|
|
self.mutex.release_lock()
|
|
return n
|
|
|
|
# Check if the queue is empty (not reliable!)
|
|
def empty(self):
|
|
self.mutex.acquire_lock()
|
|
n = self._empty()
|
|
self.mutex.release_lock()
|
|
return n
|
|
|
|
# Check if the queue is full (not reliable!)
|
|
def full(self):
|
|
self.mutex.acquire_lock()
|
|
n = self._full()
|
|
self.mutex.release_lock()
|
|
return n
|
|
|
|
# Put a new item into the queue
|
|
def put(self, item):
|
|
self.fsema.acquire_lock()
|
|
self.mutex.acquire_lock()
|
|
was_empty = self._empty()
|
|
self._put(item)
|
|
if was_empty:
|
|
self.esema.release_lock()
|
|
if not self._full():
|
|
self.fsema.release_lock()
|
|
self.mutex.release_lock()
|
|
|
|
# Get an item from the queue,
|
|
# blocking if necessary until one is available
|
|
def get(self):
|
|
self.esema.acquire_lock()
|
|
self.mutex.acquire_lock()
|
|
was_full = self._full()
|
|
item = self._get()
|
|
if was_full:
|
|
self.fsema.release_lock()
|
|
if not self._empty():
|
|
self.esema.release_lock()
|
|
self.mutex.release_lock()
|
|
return item
|
|
|
|
# Get an item from the queue if one is immediately available,
|
|
# raise Empty if the queue is empty or temporarily unavailable
|
|
def get_nowait(self):
|
|
locked = self.esema.acquire_lock(0)
|
|
self.mutex.acquire_lock()
|
|
if self._empty():
|
|
# The queue is empyt -- we can't have esema
|
|
self.mutex.release_lock()
|
|
raise Empty
|
|
if not locked:
|
|
locked = self.esema.acquire_lock(0)
|
|
if not locked:
|
|
# Somebody else has esema
|
|
# but we have mutex --
|
|
# go out of their way
|
|
self.mutex.release_lock()
|
|
raise Empty
|
|
was_full = self._full()
|
|
item = self._get()
|
|
if was_full:
|
|
self.fsema.release_lock()
|
|
if not self._empty():
|
|
self.esema.release_lock()
|
|
self.mutex.release_lock()
|
|
return item
|
|
|
|
# XXX Need to define put_nowait() as well.
|
|
|
|
|
|
# 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 wheter 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
|