215 lines
7.6 KiB
Python
215 lines
7.6 KiB
Python
"""A multi-producer, multi-consumer queue."""
|
|
|
|
from time import time as _time
|
|
from collections import deque
|
|
|
|
__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:
|
|
"""Create a queue object with a given maximum size.
|
|
|
|
If maxsize is <= 0, the queue size is infinite.
|
|
"""
|
|
def __init__(self, maxsize=0):
|
|
try:
|
|
import threading
|
|
except ImportError:
|
|
import dummy_threading as threading
|
|
self._init(maxsize)
|
|
# mutex must be held whenever the queue is mutating. All methods
|
|
# that acquire mutex must release it before returning. mutex
|
|
# is shared between the three conditions, so acquiring and
|
|
# releasing the conditions also acquires and releases mutex.
|
|
self.mutex = threading.Lock()
|
|
# Notify not_empty whenever an item is added to the queue; a
|
|
# thread waiting to get is notified then.
|
|
self.not_empty = threading.Condition(self.mutex)
|
|
# Notify not_full whenever an item is removed from the queue;
|
|
# a thread waiting to put is notified then.
|
|
self.not_full = threading.Condition(self.mutex)
|
|
# Notify all_tasks_done whenever the number of unfinished tasks
|
|
# drops to zero; thread waiting to join() is notified to resume
|
|
self.all_tasks_done = threading.Condition(self.mutex)
|
|
self.unfinished_tasks = 0
|
|
|
|
def task_done(self):
|
|
"""Indicate that a formerly enqueued task is complete.
|
|
|
|
Used by Queue consumer threads. For each get() used to fetch a task,
|
|
a subsequent call to task_done() tells the queue that the processing
|
|
on the task is complete.
|
|
|
|
If a join() is currently blocking, it will resume when all items
|
|
have been processed (meaning that a task_done() call was received
|
|
for every item that had been put() into the queue).
|
|
|
|
Raises a ValueError if called more times than there were items
|
|
placed in the queue.
|
|
"""
|
|
self.all_tasks_done.acquire()
|
|
try:
|
|
unfinished = self.unfinished_tasks - 1
|
|
if unfinished <= 0:
|
|
if unfinished < 0:
|
|
raise ValueError('task_done() called too many times')
|
|
self.all_tasks_done.notifyAll()
|
|
self.unfinished_tasks = unfinished
|
|
finally:
|
|
self.all_tasks_done.release()
|
|
|
|
def join(self):
|
|
"""Blocks until all items in the Queue have been gotten and processed.
|
|
|
|
The count of unfinished tasks goes up whenever an item is added to the
|
|
queue. The count goes down whenever a consumer thread calls task_done()
|
|
to indicate the item was retrieved and all work on it is complete.
|
|
|
|
When the count of unfinished tasks drops to zero, join() unblocks.
|
|
"""
|
|
self.all_tasks_done.acquire()
|
|
try:
|
|
while self.unfinished_tasks:
|
|
self.all_tasks_done.wait()
|
|
finally:
|
|
self.all_tasks_done.release()
|
|
|
|
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).
|
|
"""
|
|
self.not_full.acquire()
|
|
try:
|
|
if not block:
|
|
if self._full():
|
|
raise Full
|
|
elif timeout is None:
|
|
while self._full():
|
|
self.not_full.wait()
|
|
else:
|
|
if timeout < 0:
|
|
raise ValueError("'timeout' must be a positive number")
|
|
endtime = _time() + timeout
|
|
while self._full():
|
|
remaining = endtime - _time()
|
|
if remaining <= 0.0:
|
|
raise Full
|
|
self.not_full.wait(remaining)
|
|
self._put(item)
|
|
self.unfinished_tasks += 1
|
|
self.not_empty.notify()
|
|
finally:
|
|
self.not_full.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).
|
|
"""
|
|
self.not_empty.acquire()
|
|
try:
|
|
if not block:
|
|
if self._empty():
|
|
raise Empty
|
|
elif timeout is None:
|
|
while self._empty():
|
|
self.not_empty.wait()
|
|
else:
|
|
if timeout < 0:
|
|
raise ValueError("'timeout' must be a positive number")
|
|
endtime = _time() + timeout
|
|
while self._empty():
|
|
remaining = endtime - _time()
|
|
if remaining <= 0.0:
|
|
raise Empty
|
|
self.not_empty.wait(remaining)
|
|
item = self._get()
|
|
self.not_full.notify()
|
|
return item
|
|
finally:
|
|
self.not_empty.release()
|
|
|
|
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 = deque()
|
|
|
|
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.popleft()
|