/brz/remove-bazaar

# Copyright (C) 2008 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

"""Persistent maps from string->string using CHK stores."""

import osutils

class CHKMap(object):

    """A persistent map from string to string backed by a CHK store."""

    def __init__(self, store, root_key):

        """Create a CHKMap object.

        :param store: The store the CHKMap is stored in.

        :param root_key: The root key of the map. None to create an empty

            CHKMap.

        """

        self._store = store

        if root_key is None:

            self._root_node = RootNode()

        else:

            self._root_node = root_key

    def apply_delta(self, delta):

        """Apply a delta to the map.

        :param delta: An iterable of old_key, new_key, new_value tuples.

            If new_key is not None, then new_key->new_value is inserted

            into the map; if old_key is not None, then the old mapping

            of old_key is removed.

        """

        for old, new, value in delta:

            if old is not None and old != new:

                # unmap

                self._unmap(old)

        for old, new, value in delta:

            if new is not None:

                # map

                self._map(new, value)

        return self._save()

    def _ensure_root(self):

        """Ensure that the root node is an object not a key."""

        if type(self._root_node) == tuple:

            # Demand-load the root

            bytes = self._read_bytes(self._root_node)

            root_key = self._root_node

            self._root_node = RootNode()

            self._root_node.deserialise(bytes, root_key)

    def _read_bytes(self, key):

        stream = self._store.get_record_stream([key], 'unordered', True)

        return stream.next().get_bytes_as('fulltext')

    @classmethod

    def from_dict(klass, store, initial_value):

        """Create a CHKMap in store with initial_value as the content.

        :param store: The store to record initial_value in, a VersionedFiles

            object with 1-tuple keys supporting CHK key generation.

        :param initial_value: A dict to store in store. Its keys and values

            must be bytestrings.

        :return: The root chk of te resulting CHKMap.

        """

        result = CHKMap(store, None)

        for key, value in initial_value.items():

            result._map(key, value)

        return result._save()

    def iteritems(self, key_filter=None):

        """Iterate over the entire CHKMap's contents."""

        self._ensure_root()

        if key_filter is not None:

            for name, key, in self._root_node._nodes.iteritems():

                if name in key_filter:

                    bytes = self._read_bytes(key)

                    yield name, ValueNode.deserialise(bytes).value

        else:

            for name, key, in self._root_node._nodes.iteritems():

                bytes = self._read_bytes(key)

                yield name, ValueNode.deserialise(bytes).value

    def key(self):

        """Return the key for this map."""

        if isinstance(self._root_node, tuple):

            return self._root_node

        else:

            return self._root_node._key

    def _map(self, key, value):

        """Map key to value."""

        self._ensure_root()

        # Store the value

        bytes = ValueNode(value).serialise()

        sha1, _, _ = self._store.add_lines((None,), (), osutils.split_lines(bytes))

        # And link into the root

        self._root_node.add_child(key, ("sha1:" + sha1,))

    def _unmap(self, key):

        """remove key from the map."""

        self._ensure_root()

        self._root_node.remove_child(key)

    def _save(self):

        """Save the map completely.

        :return: The key of the root node.

        """

        if type(self._root_node) == tuple:

            # Already saved.

            return self._root_node

        # TODO: flush root_nodes children?

        bytes = self._root_node.serialise()

        sha1, _, _ = self._store.add_lines((None,), (),

            osutils.split_lines(bytes))

        result = ("sha1:" + sha1,)

        self._root_node._key = result

        return result

class RootNode(object):

    """A root node in a CHKMap."""

    def __init__(self):

        self._nodes = {}

        self._key = None

    def add_child(self, name, child):

        """Add a child to the node.

        If the node changes, it's key is reset.

        :param name: The name of the child. A bytestring.

        :param child: The child, a key tuple for the childs value.

        """

        self._nodes[name] = child

        self._key = None

    def deserialise(self, bytes, key):

        """Set the nodes value to that contained in bytes.

        :param bytes: The bytes of the node.

        :param key: The key that the serialised node has.

        """

        lines = bytes.splitlines()

        nodes = {}

        if lines[0] != 'chkroot:':

            raise ValueError("not a serialised root node: %r" % bytes)

        for line in lines[1:]:

            name, value = line.split('\x00')

            nodes[name] = (value,)

        self._nodes = nodes

        self._key = key

    def refs(self):

        """Get the CHK key references this node holds."""

        return self._nodes.values()

    def remove_child(self, name):

        """Remove name from the node.

        If the node changes, it's key is reset.

        :param name: The name to remove from the node.

        """

        del self._nodes[name]

        self._key = None

    def serialise(self):

        """Flatten the node to a bytestring.

        :return: A bytestring.

        """

        lines = ["chkroot:\n"]

        for name, child in sorted(self._nodes.items()):

            lines.append("%s\x00%s\n" % (name, child[0]))

        return "".join(lines)

class ValueNode(object):

    """A value in a CHKMap."""

    def __init__(self, value):

        """Create a ValueNode.

        :param value: The value of this node, must be a bytestring.

        """

        self.value = value

    @classmethod

    def deserialise(klass, bytes):

        """Get a ValueNode from a serialised bytestring.

        :param bytes: The bytes returned by an earlier serialisation.

        """

        if not bytes.startswith("chkvalue:\n"):

            raise ValueError("not a chkvalue %r" % bytes)

        return ValueNode(bytes[10:])

    def serialise(self):

        """Flatten the value to a bytestring.

        :return: A bytestring.

        """

        return "chkvalue:\n" + self.value