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255 lines
8.4 KiB
255 lines
8.4 KiB
4 months ago
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#
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# Module which supports allocation of memory from an mmap
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#
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# multiprocessing/heap.py
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#
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# Copyright (c) 2006-2008, R Oudkerk
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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# 3. Neither the name of author nor the names of any contributors may be
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# used to endorse or promote products derived from this software
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# without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
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# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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# SUCH DAMAGE.
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#
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import bisect
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import mmap
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import tempfile
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import os
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import sys
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import threading
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import itertools
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import _multiprocessing
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from multiprocessing.util import Finalize, info
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from multiprocessing.forking import assert_spawning
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__all__ = ['BufferWrapper']
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#
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# Inheirtable class which wraps an mmap, and from which blocks can be allocated
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#
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if sys.platform == 'win32':
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from _multiprocessing import win32
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class Arena(object):
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_counter = itertools.count()
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def __init__(self, size):
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self.size = size
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self.name = 'pym-%d-%d' % (os.getpid(), Arena._counter.next())
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self.buffer = mmap.mmap(-1, self.size, tagname=self.name)
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assert win32.GetLastError() == 0, 'tagname already in use'
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self._state = (self.size, self.name)
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def __getstate__(self):
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assert_spawning(self)
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return self._state
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def __setstate__(self, state):
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self.size, self.name = self._state = state
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self.buffer = mmap.mmap(-1, self.size, tagname=self.name)
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assert win32.GetLastError() == win32.ERROR_ALREADY_EXISTS
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else:
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class Arena(object):
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def __init__(self, size):
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self.buffer = mmap.mmap(-1, size)
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self.size = size
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self.name = None
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#
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# Class allowing allocation of chunks of memory from arenas
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#
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class Heap(object):
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_alignment = 8
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def __init__(self, size=mmap.PAGESIZE):
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self._lastpid = os.getpid()
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self._lock = threading.Lock()
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self._size = size
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self._lengths = []
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self._len_to_seq = {}
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self._start_to_block = {}
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self._stop_to_block = {}
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self._allocated_blocks = set()
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self._arenas = []
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# list of pending blocks to free - see free() comment below
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self._pending_free_blocks = []
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@staticmethod
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def _roundup(n, alignment):
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# alignment must be a power of 2
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mask = alignment - 1
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return (n + mask) & ~mask
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def _malloc(self, size):
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# returns a large enough block -- it might be much larger
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i = bisect.bisect_left(self._lengths, size)
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if i == len(self._lengths):
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length = self._roundup(max(self._size, size), mmap.PAGESIZE)
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self._size *= 2
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info('allocating a new mmap of length %d', length)
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arena = Arena(length)
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self._arenas.append(arena)
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return (arena, 0, length)
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else:
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length = self._lengths[i]
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seq = self._len_to_seq[length]
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block = seq.pop()
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if not seq:
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del self._len_to_seq[length], self._lengths[i]
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(arena, start, stop) = block
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del self._start_to_block[(arena, start)]
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del self._stop_to_block[(arena, stop)]
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return block
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def _free(self, block):
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# free location and try to merge with neighbours
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(arena, start, stop) = block
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try:
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prev_block = self._stop_to_block[(arena, start)]
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except KeyError:
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pass
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else:
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start, _ = self._absorb(prev_block)
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try:
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next_block = self._start_to_block[(arena, stop)]
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except KeyError:
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pass
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else:
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_, stop = self._absorb(next_block)
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block = (arena, start, stop)
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length = stop - start
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try:
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self._len_to_seq[length].append(block)
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except KeyError:
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self._len_to_seq[length] = [block]
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bisect.insort(self._lengths, length)
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self._start_to_block[(arena, start)] = block
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self._stop_to_block[(arena, stop)] = block
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def _absorb(self, block):
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# deregister this block so it can be merged with a neighbour
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(arena, start, stop) = block
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del self._start_to_block[(arena, start)]
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del self._stop_to_block[(arena, stop)]
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length = stop - start
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seq = self._len_to_seq[length]
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seq.remove(block)
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if not seq:
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del self._len_to_seq[length]
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self._lengths.remove(length)
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return start, stop
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def _free_pending_blocks(self):
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# Free all the blocks in the pending list - called with the lock held.
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while True:
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try:
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block = self._pending_free_blocks.pop()
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except IndexError:
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break
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self._allocated_blocks.remove(block)
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self._free(block)
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def free(self, block):
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# free a block returned by malloc()
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# Since free() can be called asynchronously by the GC, it could happen
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# that it's called while self._lock is held: in that case,
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# self._lock.acquire() would deadlock (issue #12352). To avoid that, a
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# trylock is used instead, and if the lock can't be acquired
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# immediately, the block is added to a list of blocks to be freed
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# synchronously sometimes later from malloc() or free(), by calling
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# _free_pending_blocks() (appending and retrieving from a list is not
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# strictly thread-safe but under cPython it's atomic thanks to the GIL).
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assert os.getpid() == self._lastpid
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if not self._lock.acquire(False):
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# can't acquire the lock right now, add the block to the list of
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# pending blocks to free
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self._pending_free_blocks.append(block)
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else:
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# we hold the lock
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try:
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self._free_pending_blocks()
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self._allocated_blocks.remove(block)
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self._free(block)
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finally:
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self._lock.release()
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def malloc(self, size):
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# return a block of right size (possibly rounded up)
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assert 0 <= size < sys.maxint
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if os.getpid() != self._lastpid:
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self.__init__() # reinitialize after fork
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self._lock.acquire()
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self._free_pending_blocks()
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try:
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size = self._roundup(max(size,1), self._alignment)
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(arena, start, stop) = self._malloc(size)
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new_stop = start + size
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if new_stop < stop:
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self._free((arena, new_stop, stop))
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block = (arena, start, new_stop)
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self._allocated_blocks.add(block)
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return block
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finally:
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self._lock.release()
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#
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# Class representing a chunk of an mmap -- can be inherited
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#
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class BufferWrapper(object):
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_heap = Heap()
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def __init__(self, size):
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assert 0 <= size < sys.maxint
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block = BufferWrapper._heap.malloc(size)
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self._state = (block, size)
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Finalize(self, BufferWrapper._heap.free, args=(block,))
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def get_address(self):
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(arena, start, stop), size = self._state
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address, length = _multiprocessing.address_of_buffer(arena.buffer)
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assert size <= length
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return address + start
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def get_size(self):
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return self._state[1]
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