Synnefo » Pithos

# Copyright 2011 GRNET S.A. All rights reserved.

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from os.path import realpath, join, exists, isdir

from os import makedirs, unlink

from errno import ENOENT

from pithos.lib.hashfiler.context_file import ContextFile

class Mapper(object):

    """Mapper.

       Required contstructor parameters: mappath, namelen.

    """

    mappath = None

    namelen = None

    def __init__(self, **params):

        self.params = params

        self.namelen = params['namelen']

        mappath = realpath(params['mappath'])

        if not isdir(mappath):

            if not exists(mappath):

                makedirs(mappath)

            else:

                raise ValueError("Variable mappath '%s' is not a directory" % (mappath,))

        self.mappath = mappath

    def get_rear_map(self, name, create=0):

        name = join(self.mappath, hex(int(name)))

        return ContextFile(name, create)

    def delete_rear_map(self, name):

        name = join(self.mappath, hex(int(name)))

        try:

            unlink(name)

            return 1

        except OSError, e:

            if e.errno != ENOENT:

                raise

        return 0

    def map_retr(self, name, blkoff=0, nr=100000000000000):

        """Return as a list, part of the hashes map of an object

           at the given block offset.

           By default, return the whole hashes map.

        """

        namelen = self.namelen

        hashes = ()

        with self.get_rear_map(name, 0) as rmap:

            if rmap:

                hashes = list(rmap.sync_read_chunks(namelen, nr, blkoff))

        return hashes

    def map_stor(self, name, hashes=(), blkoff=0, create=1):

        """Store hashes in the given hashes map, replacing the old ones."""

        namelen = self.namelen

        with self.get_rear_map(name, 1) as rmap:

            rmap.sync_write_chunks(namelen, blkoff, hashes, None)

#     def map_copy(self, src, dst):

#         """Copy a hashes map to another one, replacing it."""

#         with self.get_rear_map(src, 0) as rmap:

#             if rmap:

#                 rmap.copy_to(dst)

    def map_remv(self, name):

        """Remove a hashes map. Returns true if the map was found and removed."""

        return self.delete_rear_map(name)