Synnefo

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from pithos.api.settings import PITHOS_BACKEND_STORAGE

from store_helpers import get_blocker

class Blocker(object):

    """Blocker.

       Required constructor parameters: blocksize, blockpath, hashtype.

       Optional blockpool.

    """

    def __init__(self, **params):

        fblocker, rblocker, hashlen, blocksize = \

                        get_blocker(PITHOS_BACKEND_STORAGE, **params)

        self.fblocker = fblocker

        self.rblocker = rblocker

        self.hashlen = hashlen

        self.blocksize = blocksize

    def block_hash(self, data):

        """Hash a block of data"""

        if self.fblocker:

            return self.fblocker.block_hash(data)

        elif self.rblocker:

            return self.rblocker.block_hash(data)

    def block_ping(self, hashes):

        """Check hashes for existence and

           return those missing from block storage.

        """

        if self.fblocker:

            return self.fblocker.block_ping(hashes)

        elif self.rblocker:

            return self.rblocker.block_ping(hashes)

    def block_retr(self, hashes):

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

        if self.fblocker:

            return self.fblocker.block_retr(hashes)

        elif self.rblocker:

            return self.rblocker.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.

        """

        if self.fblocker:

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

        elif self.rblocker:

            (hashes, missing) = self.rblocker.block_stor(blocklist)

        return (hashes, 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

        if self.fblocker:

            (hash, existed) = self.fblocker.block_delta(blkhash, offset, data)

        elif self.rblocker:

            (hash, existed) = self.rblocker.block_delta(blkhash, offset,

                                                            data)

        if not hash:

            return None, None

        if self.rblocker and not hash:

            block = self.rblocker.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):]

            hash, existed = self.rblocker.block_stor((newblock,))

        elif self.fblocker and not 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):]

            hash, existed = self.fblocker.block_stor((newblock,))

        return hash, 1 if existed else 0