1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
|
"""A multi-producer, multi-consumer 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.
"""
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()
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, 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()
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(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):
return self.queue.pop(0)
|
