/brz/remove-bazaar

# Copyright (C) 2005, 2006, 2007, 2008 Canonical Ltd

#

# Authors:

#   Johan Rydberg <jrydberg@gnu.org>

#

# 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

"""Versioned text file storage api."""

from copy import copy

from cStringIO import StringIO

import os

from zlib import adler32

from bzrlib.lazy_import import lazy_import

lazy_import(globals(), """

import urllib

from bzrlib import (

    errors,

    index,

    osutils,

    multiparent,

    tsort,

    revision,

    ui,

    )

from bzrlib.graph import DictParentsProvider, Graph, _StackedParentsProvider

from bzrlib.transport.memory import MemoryTransport

""")

from bzrlib.inter import InterObject

from bzrlib.registry import Registry

from bzrlib.symbol_versioning import *

from bzrlib.textmerge import TextMerge

adapter_registry = Registry()

adapter_registry.register_lazy(('knit-delta-gz', 'fulltext'), 'bzrlib.knit',

    'DeltaPlainToFullText')

adapter_registry.register_lazy(('knit-ft-gz', 'fulltext'), 'bzrlib.knit',

    'FTPlainToFullText')

adapter_registry.register_lazy(('knit-annotated-delta-gz', 'knit-delta-gz'),

    'bzrlib.knit', 'DeltaAnnotatedToUnannotated')

adapter_registry.register_lazy(('knit-annotated-delta-gz', 'fulltext'),

    'bzrlib.knit', 'DeltaAnnotatedToFullText')

adapter_registry.register_lazy(('knit-annotated-ft-gz', 'knit-ft-gz'),

    'bzrlib.knit', 'FTAnnotatedToUnannotated')

adapter_registry.register_lazy(('knit-annotated-ft-gz', 'fulltext'),

    'bzrlib.knit', 'FTAnnotatedToFullText')

class ContentFactory(object):

    """Abstract interface for insertion and retrieval from a VersionedFile.

    :ivar sha1: None, or the sha1 of the content fulltext.

    :ivar storage_kind: The native storage kind of this factory. One of

        'mpdiff', 'knit-annotated-ft', 'knit-annotated-delta', 'knit-ft',

        'knit-delta', 'fulltext', 'knit-annotated-ft-gz',

        'knit-annotated-delta-gz', 'knit-ft-gz', 'knit-delta-gz'.

    :ivar key: The key of this content. Each key is a tuple with a single

        string in it.

    :ivar parents: A tuple of parent keys for self.key. If the object has

        no parent information, None (as opposed to () for an empty list of

        parents).

    """

    def __init__(self):

        """Create a ContentFactory."""

        self.sha1 = None

        self.storage_kind = None

        self.key = None

        self.parents = None

class FulltextContentFactory(ContentFactory):

    """Static data content factory.

    This takes a fulltext when created and just returns that during

    get_bytes_as('fulltext').

    :ivar sha1: None, or the sha1 of the content fulltext.

    :ivar storage_kind: The native storage kind of this factory. Always

        'fulltext'.

    :ivar key: The key of this content. Each key is a tuple with a single

        string in it.

    :ivar parents: A tuple of parent keys for self.key. If the object has

        no parent information, None (as opposed to () for an empty list of

        parents).

     """

    def __init__(self, key, parents, sha1, text):

        """Create a ContentFactory."""

        self.sha1 = sha1

        self.storage_kind = 'fulltext'

        self.key = key

        self.parents = parents

        self._text = text

    def get_bytes_as(self, storage_kind):

        if storage_kind == self.storage_kind:

            return self._text

        raise errors.UnavailableRepresentation(self.key, storage_kind,

            self.storage_kind)

class AbsentContentFactory(ContentFactory):

    """A placeholder content factory for unavailable texts.

    :ivar sha1: None.

    :ivar storage_kind: 'absent'.

    :ivar key: The key of this content. Each key is a tuple with a single

        string in it.

    :ivar parents: None.

    """

    def __init__(self, key):

        """Create a ContentFactory."""

        self.sha1 = None

        self.storage_kind = 'absent'

        self.key = key

        self.parents = None

class AdapterFactory(ContentFactory):

    """A content factory to adapt between key prefix's."""

    def __init__(self, key, parents, adapted):

        """Create an adapter factory instance."""

        self.key = key

        self.parents = parents

        self._adapted = adapted

    def __getattr__(self, attr):

        """Return a member from the adapted object."""

        if attr in ('key', 'parents'):

            return self.__dict__[attr]

        else:

            return getattr(self._adapted, attr)

def filter_absent(record_stream):

    """Adapt a record stream to remove absent records."""

    for record in record_stream:

        if record.storage_kind != 'absent':

            yield record

class VersionedFile(object):

    """Versioned text file storage.

    A versioned file manages versions of line-based text files,

    keeping track of the originating version for each line.

    To clients the "lines" of the file are represented as a list of

    strings. These strings will typically have terminal newline

    characters, but this is not required.  In particular files commonly

    do not have a newline at the end of the file.

    Texts are identified by a version-id string.

    """

    @staticmethod

    def check_not_reserved_id(version_id):

        revision.check_not_reserved_id(version_id)

    def copy_to(self, name, transport):

        """Copy this versioned file to name on transport."""

        raise NotImplementedError(self.copy_to)

    def get_record_stream(self, versions, ordering, include_delta_closure):

        """Get a stream of records for versions.

        :param versions: The versions to include. Each version is a tuple

            (version,).

        :param ordering: Either 'unordered' or 'topological'. A topologically

            sorted stream has compression parents strictly before their

            children.

        :param include_delta_closure: If True then the closure across any

            compression parents will be included (in the data content of the

            stream, not in the emitted records). This guarantees that

            'fulltext' can be used successfully on every record.

        :return: An iterator of ContentFactory objects, each of which is only

            valid until the iterator is advanced.

        """

        raise NotImplementedError(self.get_record_stream)

    def has_version(self, version_id):

        """Returns whether version is present."""

        raise NotImplementedError(self.has_version)

    def insert_record_stream(self, stream):

        """Insert a record stream into this versioned file.

        :param stream: A stream of records to insert. 

        :return: None

        :seealso VersionedFile.get_record_stream:

        """

        raise NotImplementedError

    def add_lines(self, version_id, parents, lines, parent_texts=None,

        left_matching_blocks=None, nostore_sha=None, random_id=False,

        check_content=True):

        """Add a single text on top of the versioned file.

        Must raise RevisionAlreadyPresent if the new version is

        already present in file history.

        Must raise RevisionNotPresent if any of the given parents are

        not present in file history.

        :param lines: A list of lines. Each line must be a bytestring. And all

            of them except the last must be terminated with \n and contain no

            other \n's. The last line may either contain no \n's or a single

            terminated \n. If the lines list does meet this constraint the add

            routine may error or may succeed - but you will be unable to read

            the data back accurately. (Checking the lines have been split

            correctly is expensive and extremely unlikely to catch bugs so it

            is not done at runtime unless check_content is True.)

        :param parent_texts: An optional dictionary containing the opaque 

            representations of some or all of the parents of version_id to

            allow delta optimisations.  VERY IMPORTANT: the texts must be those

            returned by add_lines or data corruption can be caused.

        :param left_matching_blocks: a hint about which areas are common

            between the text and its left-hand-parent.  The format is

            the SequenceMatcher.get_matching_blocks format.

        :param nostore_sha: Raise ExistingContent and do not add the lines to

            the versioned file if the digest of the lines matches this.

        :param random_id: If True a random id has been selected rather than

            an id determined by some deterministic process such as a converter

            from a foreign VCS. When True the backend may choose not to check

            for uniqueness of the resulting key within the versioned file, so

            this should only be done when the result is expected to be unique

            anyway.

        :param check_content: If True, the lines supplied are verified to be

            bytestrings that are correctly formed lines.

        :return: The text sha1, the number of bytes in the text, and an opaque

                 representation of the inserted version which can be provided

                 back to future add_lines calls in the parent_texts dictionary.

        """

        self._check_write_ok()

        return self._add_lines(version_id, parents, lines, parent_texts,

            left_matching_blocks, nostore_sha, random_id, check_content)

    def _add_lines(self, version_id, parents, lines, parent_texts,

        left_matching_blocks, nostore_sha, random_id, check_content):

        """Helper to do the class specific add_lines."""

        raise NotImplementedError(self.add_lines)

    def add_lines_with_ghosts(self, version_id, parents, lines,

        parent_texts=None, nostore_sha=None, random_id=False,

        check_content=True, left_matching_blocks=None):

        """Add lines to the versioned file, allowing ghosts to be present.

        This takes the same parameters as add_lines and returns the same.

        """

        self._check_write_ok()

        return self._add_lines_with_ghosts(version_id, parents, lines,

            parent_texts, nostore_sha, random_id, check_content, left_matching_blocks)

    def _add_lines_with_ghosts(self, version_id, parents, lines, parent_texts,

        nostore_sha, random_id, check_content, left_matching_blocks):

        """Helper to do class specific add_lines_with_ghosts."""

        raise NotImplementedError(self.add_lines_with_ghosts)

    def check(self, progress_bar=None):

        """Check the versioned file for integrity."""

        raise NotImplementedError(self.check)

    def _check_lines_not_unicode(self, lines):

        """Check that lines being added to a versioned file are not unicode."""

        for line in lines:

            if line.__class__ is not str:

                raise errors.BzrBadParameterUnicode("lines")

    def _check_lines_are_lines(self, lines):

        """Check that the lines really are full lines without inline EOL."""

        for line in lines:

            if '\n' in line[:-1]:

                raise errors.BzrBadParameterContainsNewline("lines")

    def get_format_signature(self):

        """Get a text description of the data encoding in this file.

        :since: 0.90

        """

        raise NotImplementedError(self.get_format_signature)

    def make_mpdiffs(self, version_ids):

        """Create multiparent diffs for specified versions."""

        knit_versions = set()

        knit_versions.update(version_ids)

        parent_map = self.get_parent_map(version_ids)

        for version_id in version_ids:

            try:

                knit_versions.update(parent_map[version_id])

            except KeyError:

                raise errors.RevisionNotPresent(version_id, self)

        # We need to filter out ghosts, because we can't diff against them.

        knit_versions = set(self.get_parent_map(knit_versions).keys())

        lines = dict(zip(knit_versions,

            self._get_lf_split_line_list(knit_versions)))

        diffs = []

        for version_id in version_ids:

            target = lines[version_id]

            try:

                parents = [lines[p] for p in parent_map[version_id] if p in

                    knit_versions]

            except KeyError:

                # I don't know how this could ever trigger.

                # parent_map[version_id] was already triggered in the previous

                # for loop, and lines[p] has the 'if p in knit_versions' check,

                # so we again won't have a KeyError.

                raise errors.RevisionNotPresent(version_id, self)

            if len(parents) > 0:

                left_parent_blocks = self._extract_blocks(version_id,

                                                          parents[0], target)

            else:

                left_parent_blocks = None

            diffs.append(multiparent.MultiParent.from_lines(target, parents,

                         left_parent_blocks))

        return diffs

    def _extract_blocks(self, version_id, source, target):

        return None

    def add_mpdiffs(self, records):

        """Add mpdiffs to this VersionedFile.

        Records should be iterables of version, parents, expected_sha1,

        mpdiff. mpdiff should be a MultiParent instance.

        """

        # Does this need to call self._check_write_ok()? (IanC 20070919)

        vf_parents = {}

        mpvf = multiparent.MultiMemoryVersionedFile()

        versions = []

        for version, parent_ids, expected_sha1, mpdiff in records:

            versions.append(version)

            mpvf.add_diff(mpdiff, version, parent_ids)

        needed_parents = set()

        for version, parent_ids, expected_sha1, mpdiff in records:

            needed_parents.update(p for p in parent_ids

                                  if not mpvf.has_version(p))

        present_parents = set(self.get_parent_map(needed_parents).keys())

        for parent_id, lines in zip(present_parents,

                                 self._get_lf_split_line_list(present_parents)):

            mpvf.add_version(lines, parent_id, [])

        for (version, parent_ids, expected_sha1, mpdiff), lines in\

            zip(records, mpvf.get_line_list(versions)):

            if len(parent_ids) == 1:

                left_matching_blocks = list(mpdiff.get_matching_blocks(0,

                    mpvf.get_diff(parent_ids[0]).num_lines()))

            else:

                left_matching_blocks = None

            try:

                _, _, version_text = self.add_lines_with_ghosts(version,

                    parent_ids, lines, vf_parents,

                    left_matching_blocks=left_matching_blocks)

            except NotImplementedError:

                # The vf can't handle ghosts, so add lines normally, which will

                # (reasonably) fail if there are ghosts in the data.

                _, _, version_text = self.add_lines(version,

                    parent_ids, lines, vf_parents,

                    left_matching_blocks=left_matching_blocks)

            vf_parents[version] = version_text

        sha1s = self.get_sha1s(versions)

        for version, parent_ids, expected_sha1, mpdiff in records:

            if expected_sha1 != sha1s[version]:

                raise errors.VersionedFileInvalidChecksum(version)

    def get_text(self, version_id):

        """Return version contents as a text string.

        Raises RevisionNotPresent if version is not present in

        file history.

        """

        return ''.join(self.get_lines(version_id))

    get_string = get_text

    def get_texts(self, version_ids):

        """Return the texts of listed versions as a list of strings.

        Raises RevisionNotPresent if version is not present in

        file history.

        """

        return [''.join(self.get_lines(v)) for v in version_ids]

    def get_lines(self, version_id):

        """Return version contents as a sequence of lines.

        Raises RevisionNotPresent if version is not present in

        file history.

        """

        raise NotImplementedError(self.get_lines)

    def _get_lf_split_line_list(self, version_ids):

        return [StringIO(t).readlines() for t in self.get_texts(version_ids)]

    def get_ancestry(self, version_ids, topo_sorted=True):

        """Return a list of all ancestors of given version(s). This

        will not include the null revision.

        This list will not be topologically sorted if topo_sorted=False is

        passed.

        Must raise RevisionNotPresent if any of the given versions are

        not present in file history."""

        if isinstance(version_ids, basestring):

            version_ids = [version_ids]

        raise NotImplementedError(self.get_ancestry)

    def get_ancestry_with_ghosts(self, version_ids):

        """Return a list of all ancestors of given version(s). This

        will not include the null revision.

        Must raise RevisionNotPresent if any of the given versions are

        not present in file history.

        Ghosts that are known about will be included in ancestry list,

        but are not explicitly marked.

        """

        raise NotImplementedError(self.get_ancestry_with_ghosts)

    def get_parent_map(self, version_ids):

        """Get a map of the parents of version_ids.

        :param version_ids: The version ids to look up parents for.

        :return: A mapping from version id to parents.

        """

        raise NotImplementedError(self.get_parent_map)

    def get_parents_with_ghosts(self, version_id):

        """Return version names for parents of version_id.

        Will raise RevisionNotPresent if version_id is not present

        in the history.

        Ghosts that are known about will be included in the parent list,

        but are not explicitly marked.

        """

        try:

            return list(self.get_parent_map([version_id])[version_id])

        except KeyError:

            raise errors.RevisionNotPresent(version_id, self)

    def annotate(self, version_id):

        """Return a list of (version-id, line) tuples for version_id.

        :raise RevisionNotPresent: If the given version is

        not present in file history.

        """

        raise NotImplementedError(self.annotate)

    def iter_lines_added_or_present_in_versions(self, version_ids=None,

                                                pb=None):

        """Iterate over the lines in the versioned file from version_ids.

        This may return lines from other versions. Each item the returned

        iterator yields is a tuple of a line and a text version that that line

        is present in (not introduced in).

        Ordering of results is in whatever order is most suitable for the

        underlying storage format.

        If a progress bar is supplied, it may be used to indicate progress.

        The caller is responsible for cleaning up progress bars (because this

        is an iterator).

        NOTES: Lines are normalised: they will all have \n terminators.

               Lines are returned in arbitrary order.

        :return: An iterator over (line, version_id).

        """

        raise NotImplementedError(self.iter_lines_added_or_present_in_versions)

    def plan_merge(self, ver_a, ver_b):

        """Return pseudo-annotation indicating how the two versions merge.

        This is computed between versions a and b and their common

        base.

        Weave lines present in none of them are skipped entirely.

        Legend:

        killed-base Dead in base revision

        killed-both Killed in each revision

        killed-a    Killed in a

        killed-b    Killed in b

        unchanged   Alive in both a and b (possibly created in both)

        new-a       Created in a

        new-b       Created in b

        ghost-a     Killed in a, unborn in b    

        ghost-b     Killed in b, unborn in a

        irrelevant  Not in either revision

        """

        raise NotImplementedError(VersionedFile.plan_merge)

    def weave_merge(self, plan, a_marker=TextMerge.A_MARKER,

                    b_marker=TextMerge.B_MARKER):

        return PlanWeaveMerge(plan, a_marker, b_marker).merge_lines()[0]

class RecordingVersionedFilesDecorator(object):

    """A minimal versioned files that records calls made on it.

    Only enough methods have been added to support tests using it to date.

    :ivar calls: A list of the calls made; can be reset at any time by

        assigning [] to it.

    """

    def __init__(self, backing_vf):

        """Create a RecordingVersionedFileDsecorator decorating backing_vf.

        :param backing_vf: The versioned file to answer all methods.

        """

        self._backing_vf = backing_vf

        self.calls = []

    def add_lines(self, key, parents, lines, parent_texts=None,

        left_matching_blocks=None, nostore_sha=None, random_id=False,

        check_content=True):

        self.calls.append(("add_lines", key, parents, lines, parent_texts,

            left_matching_blocks, nostore_sha, random_id, check_content))

        return self._backing_vf.add_lines(key, parents, lines, parent_texts,

            left_matching_blocks, nostore_sha, random_id, check_content)

    def check(self):

        self._backing_vf.check()

    def get_parent_map(self, keys):

        self.calls.append(("get_parent_map", copy(keys)))

        return self._backing_vf.get_parent_map(keys)

    def get_record_stream(self, keys, sort_order, include_delta_closure):

        self.calls.append(("get_record_stream", list(keys), sort_order,

            include_delta_closure))

        return self._backing_vf.get_record_stream(keys, sort_order,

            include_delta_closure)

    def get_sha1s(self, keys):

        self.calls.append(("get_sha1s", copy(keys)))

        return self._backing_vf.get_sha1s(keys)

    def iter_lines_added_or_present_in_keys(self, keys, pb=None):

        self.calls.append(("iter_lines_added_or_present_in_keys", copy(keys)))

        return self._backing_vf.iter_lines_added_or_present_in_keys(keys, pb=pb)

    def keys(self):

        self.calls.append(("keys",))

        return self._backing_vf.keys()

class KeyMapper(object):

    """KeyMappers map between keys and underlying partitioned storage."""

    def map(self, key):

        """Map key to an underlying storage identifier.

        :param key: A key tuple e.g. ('file-id', 'revision-id').

        :return: An underlying storage identifier, specific to the partitioning

            mechanism.

        """

        raise NotImplementedError(self.map)

    def unmap(self, partition_id):

        """Map a partitioned storage id back to a key prefix.

        :param partition_id: The underlying partition id.

        :return: As much of a key (or prefix) as is derivable from the partition

            id.

        """

        raise NotImplementedError(self.unmap)

class ConstantMapper(KeyMapper):

    """A key mapper that maps to a constant result."""

    def __init__(self, result):

        """Create a ConstantMapper which will return result for all maps."""

        self._result = result

    def map(self, key):

        """See KeyMapper.map()."""

        return self._result

class URLEscapeMapper(KeyMapper):

    """Base class for use with transport backed storage.

    This provides a map and unmap wrapper that respectively url escape and

    unescape their outputs and inputs.

    """

    def map(self, key):

        """See KeyMapper.map()."""

        return urllib.quote(self._map(key))

    def unmap(self, partition_id):

        """See KeyMapper.unmap()."""

        return self._unmap(urllib.unquote(partition_id))

class PrefixMapper(URLEscapeMapper):

    """A key mapper that extracts the first component of a key.

    This mapper is for use with a transport based backend.

    """

    def _map(self, key):

        """See KeyMapper.map()."""

        return key[0]

    def _unmap(self, partition_id):

        """See KeyMapper.unmap()."""

        return (partition_id,)

class HashPrefixMapper(URLEscapeMapper):

    """A key mapper that combines the first component of a key with a hash.

    This mapper is for use with a transport based backend.

    """

    def _map(self, key):

        """See KeyMapper.map()."""

        prefix = self._escape(key[0])

        return "%02x/%s" % (adler32(prefix) & 0xff, prefix)

    def _escape(self, prefix):

        """No escaping needed here."""

        return prefix

    def _unmap(self, partition_id):

        """See KeyMapper.unmap()."""

        return (self._unescape(osutils.basename(partition_id)),)

    def _unescape(self, basename):

        """No unescaping needed for HashPrefixMapper."""

        return basename

class HashEscapedPrefixMapper(HashPrefixMapper):

    """Combines the escaped first component of a key with a hash.

    This mapper is for use with a transport based backend.

    """

    _safe = "abcdefghijklmnopqrstuvwxyz0123456789-_@,."

    def _escape(self, prefix):

        """Turn a key element into a filesystem safe string.

        This is similar to a plain urllib.quote, except

        it uses specific safe characters, so that it doesn't

        have to translate a lot of valid file ids.

        """

        # @ does not get escaped. This is because it is a valid

        # filesystem character we use all the time, and it looks

        # a lot better than seeing %40 all the time.

        r = [((c in self._safe) and c or ('%%%02x' % ord(c)))

             for c in prefix]

        return ''.join(r)

    def _unescape(self, basename):

        """Escaped names are easily unescaped by urlutils."""

        return urllib.unquote(basename)

def make_versioned_files_factory(versioned_file_factory, mapper):

    """Create a ThunkedVersionedFiles factory.

    This will create a callable which when called creates a

    ThunkedVersionedFiles on a transport, using mapper to access individual

    versioned files, and versioned_file_factory to create each individual file.

    """

    def factory(transport):

        return ThunkedVersionedFiles(transport, versioned_file_factory, mapper,

            lambda:True)

    return factory

class VersionedFiles(object):

    """Storage for many versioned files.

    This object allows a single keyspace for accessing the history graph and

    contents of named bytestrings.

    Currently no implementation allows the graph of different key prefixes to

    intersect, but the API does allow such implementations in the future.

    The keyspace is expressed via simple tuples. Any instance of VersionedFiles

    may have a different length key-size, but that size will be constant for

    all texts added to or retrieved from it. For instance, bzrlib uses

    instances with a key-size of 2 for storing user files in a repository, with

    the first element the fileid, and the second the version of that file.

    The use of tuples allows a single code base to support several different

    uses with only the mapping logic changing from instance to instance.

    """

    def add_lines(self, key, parents, lines, parent_texts=None,

        left_matching_blocks=None, nostore_sha=None, random_id=False,

        check_content=True):

        """Add a text to the store.

        :param key: The key tuple of the text to add.

        :param parents: The parents key tuples of the text to add.

        :param lines: A list of lines. Each line must be a bytestring. And all

            of them except the last must be terminated with \n and contain no

            other \n's. The last line may either contain no \n's or a single

            terminating \n. If the lines list does meet this constraint the add

            routine may error or may succeed - but you will be unable to read

            the data back accurately. (Checking the lines have been split

            correctly is expensive and extremely unlikely to catch bugs so it

            is not done at runtime unless check_content is True.)

        :param parent_texts: An optional dictionary containing the opaque 

            representations of some or all of the parents of version_id to

            allow delta optimisations.  VERY IMPORTANT: the texts must be those

            returned by add_lines or data corruption can be caused.

        :param left_matching_blocks: a hint about which areas are common

            between the text and its left-hand-parent.  The format is

            the SequenceMatcher.get_matching_blocks format.

        :param nostore_sha: Raise ExistingContent and do not add the lines to

            the versioned file if the digest of the lines matches this.

        :param random_id: If True a random id has been selected rather than

            an id determined by some deterministic process such as a converter

            from a foreign VCS. When True the backend may choose not to check

            for uniqueness of the resulting key within the versioned file, so

            this should only be done when the result is expected to be unique

            anyway.

        :param check_content: If True, the lines supplied are verified to be

            bytestrings that are correctly formed lines.

        :return: The text sha1, the number of bytes in the text, and an opaque

                 representation of the inserted version which can be provided

                 back to future add_lines calls in the parent_texts dictionary.

        """

        raise NotImplementedError(self.add_lines)

    def add_mpdiffs(self, records):

        """Add mpdiffs to this VersionedFile.

        Records should be iterables of version, parents, expected_sha1,

        mpdiff. mpdiff should be a MultiParent instance.

        """

        vf_parents = {}

        mpvf = multiparent.MultiMemoryVersionedFile()

        versions = []

        for version, parent_ids, expected_sha1, mpdiff in records:

            versions.append(version)

            mpvf.add_diff(mpdiff, version, parent_ids)

        needed_parents = set()

        for version, parent_ids, expected_sha1, mpdiff in records:

            needed_parents.update(p for p in parent_ids