Synnefo

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from fileblocker import FileBlocker

def intersect(a, b):

    """ return the intersection of two lists """

    return list(set(a) & set(b))

def union(a, b):

    """ return the union of two lists """

    return list(set(a) | set(b))

class Blocker(object):

    """Blocker.

       Required constructor parameters: blocksize, blockpath, hashtype.

       Optional blockpool.

    """

    def __init__(self, **params):

        self.rblocker = None

        try:

            if params['blockpool']:

                from radosblocker import RadosBlocker

                self.rblocker = RadosBlocker(**params)

        except KeyError:

            pass

        self.fblocker = FileBlocker(**params)

        self.hashlen = self.fblocker.hashlen

        self.blocksize = params['blocksize']

    def block_hash(self, data):

        """Hash a block of data"""

        return self.fblocker.block_hash(data)

    def block_ping(self, hashes):

        """Check hashes for existence and

           return those missing from block storage.

        """

        r = []

        if self.rblocker:

            r = self.rblocker.block_ping(hashes)

        f = self.fblocker.block_ping(hashes)

        return union(r, f)

    def block_retr(self, hashes):

        """Retrieve blocks from storage by their hashes."""

        return self.fblocker.block_retr(hashes)

    def block_stor(self, blocklist):

        """Store a bunch of blocks and return (hashes, missing).

           Hashes is a list of the hashes of the blocks,

           missing is a list of indices in that list indicating

           which blocks were missing from the store.

        """

        r_missing = []

        (hashes, f_missing) = self.fblocker.block_stor(blocklist)

        if self.rblocker:

            (_, r_missing) = self.rblocker.block_stor(blocklist)

        return (hashes, union(r_missing, f_missing))

    def block_delta(self, blkhash, offset, data):

        """Construct and store a new block from a given block

           and a data 'patch' applied at offset. Return:

           (the hash of the new block, if the block already existed)

        """

        blocksize = self.blocksize

        r_hash = None

        r_existed = True

        (f_hash, f_existed) = self.fblocker.block_delta(blkhash, offset, data)

        if self.rblocker:

            (r_hash, r_existed) = self.rblocker.block_delta(blkhash, offset,

                                                            data)

        if not r_hash and not f_hash:

            return None, None

        if self.rblocker and not r_hash:

            block = self.fblocker.block_retr((blkhash,))

            if not block:

                return None, None

            block = block[0]

            newblock = block[:offset] + data

            if len(newblock) > blocksize:

                newblock = newblock[:blocksize]

            elif len(newblock) < blocksize:

                newblock += block[len(newblock):]

            r_hash, r_existed = self.rblocker.block_stor((newblock,))

        return f_hash, 1 if r_existed and f_existed else 0