Synnefo

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from os import makedirs

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

from binascii import hexlify

from context_file import ContextFile

from os import O_RDONLY, O_WRONLY

class FileMapper(object):

    """Mapper.

       Required constructor 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 _read_rear_map(self, maphash):

        filename = hexlify(maphash)

        dir = join(self.mappath, filename[0:2], filename[2:4], filename[4:6])

        name = join(dir, filename)

        return ContextFile(name, O_RDONLY)

    def _write_rear_map(self, maphash):

        filename = hexlify(maphash)

        dir = join(self.mappath, filename[0:2], filename[2:4], filename[4:6])

        if not exists(dir):

            makedirs(dir)

        name = join(dir, filename)

        return ContextFile(name, O_WRONLY)

    def _check_rear_map(self, maphash):

        filename = hexlify(maphash)

        dir = join(self.mappath, filename[0:2], filename[2:4], filename[4:6])

        name = join(dir, filename)

        return exists(name)

    def map_retr(self, maphash, 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._read_rear_map(maphash) as rmap:

            if rmap:

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

        return hashes

    def map_stor(self, maphash, hashes=(), blkoff=0):

        """Store hashes in the given hashes map."""

        namelen = self.namelen

        if self._check_rear_map(maphash):

            return

        with self._write_rear_map(maphash) as rmap:

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