/usr/share/pyshared/queuelib/queue.py is in python-queuelib 1.1.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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import struct
import glob
import json
from collections import deque
class FifoMemoryQueue(object):
"""In-memory FIFO queue, API compliant with FifoDiskQueue."""
def __init__(self):
self.q = deque()
self.push = self.q.append
def pop(self):
q = self.q
return q.popleft() if q else None
def close(self):
pass
def __len__(self):
return len(self.q)
class LifoMemoryQueue(FifoMemoryQueue):
"""In-memory LIFO queue, API compliant with LifoDiskQueue."""
def pop(self):
q = self.q
return q.pop() if q else None
class FifoDiskQueue(object):
"""Persistent FIFO queue."""
szhdr_format = ">L"
szhdr_size = struct.calcsize(szhdr_format)
def __init__(self, path, chunksize=100000):
self.path = path
if not os.path.exists(path):
os.makedirs(path)
self.info = self._loadinfo(chunksize)
self.chunksize = self.info['chunksize']
self.headf = self._openchunk(self.info['head'][0], 'ab+')
self.tailf = self._openchunk(self.info['tail'][0])
os.lseek(self.tailf.fileno(), self.info['tail'][2], os.SEEK_SET)
def push(self, string):
hnum, hpos = self.info['head']
hpos += 1
szhdr = struct.pack(self.szhdr_format, len(string))
os.write(self.headf.fileno(), szhdr + string)
if hpos == self.chunksize:
hpos = 0
hnum += 1
self.headf.close()
self.headf = self._openchunk(hnum, 'ab+')
self.info['size'] += 1
self.info['head'] = [hnum, hpos]
def _openchunk(self, number, mode='r'):
return open(os.path.join(self.path, 'q%05d' % number), mode)
def pop(self):
tnum, tcnt, toffset = self.info['tail']
if [tnum, tcnt] >= self.info['head']:
return
tfd = self.tailf.fileno()
szhdr = os.read(tfd, self.szhdr_size)
if not szhdr:
return
size, = struct.unpack(self.szhdr_format, szhdr)
data = os.read(tfd, size)
tcnt += 1
toffset += self.szhdr_size + size
if tcnt == self.chunksize and tnum <= self.info['head'][0]:
tcnt = toffset = 0
tnum += 1
self.tailf.close()
os.remove(self.tailf.name)
self.tailf = self._openchunk(tnum)
self.info['size'] -= 1
self.info['tail'] = [tnum, tcnt, toffset]
return data
def close(self):
self.headf.close()
self.tailf.close()
self._saveinfo(self.info)
if len(self) == 0:
self._cleanup()
def __len__(self):
return self.info['size']
def _loadinfo(self, chunksize):
infopath = self._infopath()
if os.path.exists(infopath):
with open(infopath) as f:
info = json.load(f)
else:
info = {
'chunksize': chunksize,
'size': 0,
'tail': [0, 0, 0],
'head': [0, 0],
}
return info
def _saveinfo(self, info):
with open(self._infopath(), 'w') as f:
json.dump(info, f)
def _infopath(self):
return os.path.join(self.path, 'info.json')
def _cleanup(self):
for x in glob.glob(os.path.join(self.path, 'q*')):
os.remove(x)
os.remove(os.path.join(self.path, 'info.json'))
if not os.listdir(self.path):
os.rmdir(self.path)
class LifoDiskQueue(object):
"""Persistent LIFO queue."""
SIZE_FORMAT = ">L"
SIZE_SIZE = struct.calcsize(SIZE_FORMAT)
def __init__(self, path):
self.path = path
if os.path.exists(path):
self.f = open(path, 'rb+')
qsize = self.f.read(self.SIZE_SIZE)
self.size, = struct.unpack(self.SIZE_FORMAT, qsize)
self.f.seek(0, os.SEEK_END)
else:
self.f = open(path, 'wb+')
self.f.write(struct.pack(self.SIZE_FORMAT, 0))
self.size = 0
def push(self, string):
self.f.write(string)
ssize = struct.pack(self.SIZE_FORMAT, len(string))
self.f.write(ssize)
self.size += 1
def pop(self):
if not self.size:
return
self.f.seek(-self.SIZE_SIZE, os.SEEK_END)
size, = struct.unpack(self.SIZE_FORMAT, self.f.read())
self.f.seek(-size-self.SIZE_SIZE, os.SEEK_END)
data = self.f.read(size)
self.f.seek(-size, os.SEEK_CUR)
self.f.truncate()
self.size -= 1
return data
def close(self):
if self.size:
self.f.seek(0)
self.f.write(struct.pack(self.SIZE_FORMAT, self.size))
self.f.close()
if not self.size:
os.remove(self.path)
def __len__(self):
return self.size
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