root / snf-pithos-backend / pithos / backends / lib / hashfiler / filemapper.py @ 89e32f26
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# Copyright 2011-2012 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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# 1. Redistributions of source code must retain the above
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# copyright notice, this list of conditions and the following
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# disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following
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# disclaimer in the documentation and/or other materials
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# provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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from os import makedirs |
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from os.path import isdir, realpath, exists, join |
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from binascii import hexlify |
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from context_file import ContextFile |
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from os import O_RDONLY, O_WRONLY |
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class FileMapper(object): |
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"""Mapper.
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Required constructor parameters: mappath, namelen.
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"""
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mappath = None
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namelen = None
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def __init__(self, **params): |
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self.params = params
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self.namelen = params['namelen'] |
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mappath = realpath(params['mappath'])
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if not isdir(mappath): |
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if not exists(mappath): |
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makedirs(mappath) |
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else:
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raise ValueError("Variable mappath '%s' is not a directory" % |
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(mappath,)) |
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self.mappath = mappath
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def _read_rear_map(self, maphash): |
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filename = hexlify(maphash) |
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dir = join(self.mappath, filename[0:2], filename[2:4], filename[4:6]) |
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if not exists(dir): |
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makedirs(dir)
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name = join(dir, filename)
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return ContextFile(name, O_RDONLY)
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def _write_rear_map(self, maphash): |
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filename = hexlify(maphash) |
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dir = join(self.mappath, filename[0:2], filename[2:4], filename[4:6]) |
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if not exists(dir): |
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makedirs(dir)
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name = join(dir, filename)
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return ContextFile(name, O_WRONLY)
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def _check_rear_map(self, maphash): |
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filename = hexlify(maphash) |
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dir = join(self.mappath, filename[0:2], filename[2:4], filename[4:6]) |
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name = join(dir, filename)
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return exists(name)
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def map_retr(self, maphash, blkoff=0, nr=100000000000000): |
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"""Return as a list, part of the hashes map of an object
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at the given block offset.
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By default, return the whole hashes map.
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"""
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namelen = self.namelen
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hashes = () |
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with self._read_rear_map(maphash) as rmap: |
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if rmap:
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hashes = list(rmap.sync_read_chunks(namelen, nr, blkoff))
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return hashes
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def map_stor(self, maphash, hashes=(), blkoff=0): |
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"""Store hashes in the given hashes map."""
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namelen = self.namelen
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if self._check_rear_map(maphash): |
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return
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with self._write_rear_map(maphash) as rmap: |
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rmap.sync_write_chunks(namelen, blkoff, hashes, None)
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