# Copyright (C) 2005, 2006 by Canonical Ltd # Written by Martin Pool. # Modified by Johan Rydberg # Modified by Robert Collins # Modified by Aaron Bentley # # 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 """Knit versionedfile implementation. A knit is a versioned file implementation that supports efficient append only updates. Knit file layout: lifeless: the data file is made up of "delta records". each delta record has a delta header that contains; (1) a version id, (2) the size of the delta (in lines), and (3) the digest of the -expanded data- (ie, the delta applied to the parent). the delta also ends with a end-marker; simply "end VERSION" delta can be line or full contents.a ... the 8's there are the index number of the annotation. version robertc@robertcollins.net-20051003014215-ee2990904cc4c7ad 7 c7d23b2a5bd6ca00e8e266cec0ec228158ee9f9e 59,59,3 8 8 if ie.executable: 8 e.set('executable', 'yes') 130,130,2 8 if elt.get('executable') == 'yes': 8 ie.executable = True end robertc@robertcollins.net-20051003014215-ee2990904cc4c7ad whats in an index: 09:33 < jrydberg> lifeless: each index is made up of a tuple of; version id, options, position, size, parents 09:33 < jrydberg> lifeless: the parents are currently dictionary compressed 09:33 < jrydberg> lifeless: (meaning it currently does not support ghosts) 09:33 < lifeless> right 09:33 < jrydberg> lifeless: the position and size is the range in the data file so the index sequence is the dictionary compressed sequence number used in the deltas to provide line annotation """ # TODOS: # 10:16 < lifeless> make partial index writes safe # 10:16 < lifeless> implement 'knit.check()' like weave.check() # 10:17 < lifeless> record known ghosts so we can detect when they are filled in rather than the current 'reweave # always' approach. # move sha1 out of the content so that join is faster at verifying parents # record content length ? from copy import copy from cStringIO import StringIO import difflib from itertools import izip, chain import operator import os import sys import warnings import bzrlib from bzrlib import ( cache_utf8, errors, ) from bzrlib.errors import FileExists, NoSuchFile, KnitError, \ InvalidRevisionId, KnitCorrupt, KnitHeaderError, \ RevisionNotPresent, RevisionAlreadyPresent from bzrlib.tuned_gzip import GzipFile from bzrlib.trace import mutter from bzrlib.osutils import contains_whitespace, contains_linebreaks, \ sha_strings from bzrlib.symbol_versioning import DEPRECATED_PARAMETER, deprecated_passed from bzrlib.tsort import topo_sort import bzrlib.weave from bzrlib.versionedfile import VersionedFile, InterVersionedFile # TODO: Split out code specific to this format into an associated object. # TODO: Can we put in some kind of value to check that the index and data # files belong together? # TODO: accommodate binaries, perhaps by storing a byte count # TODO: function to check whole file # TODO: atomically append data, then measure backwards from the cursor # position after writing to work out where it was located. we may need to # bypass python file buffering. DATA_SUFFIX = '.knit' INDEX_SUFFIX = '.kndx' class KnitContent(object): """Content of a knit version to which deltas can be applied.""" def __init__(self, lines): self._lines = lines def annotate_iter(self): """Yield tuples of (origin, text) for each content line.""" for origin, text in self._lines: yield origin, text def annotate(self): """Return a list of (origin, text) tuples.""" return list(self.annotate_iter()) def line_delta_iter(self, new_lines): """Generate line-based delta from this content to new_lines.""" new_texts = [text for origin, text in new_lines._lines] old_texts = [text for origin, text in self._lines] s = KnitSequenceMatcher(None, old_texts, new_texts) for op in s.get_opcodes(): if op[0] == 'equal': continue # ofrom oto length data yield (op[1], op[2], op[4]-op[3], new_lines._lines[op[3]:op[4]]) def line_delta(self, new_lines): return list(self.line_delta_iter(new_lines)) def text(self): return [text for origin, text in self._lines] def copy(self): return KnitContent(self._lines[:]) class _KnitFactory(object): """Base factory for creating content objects.""" def make(self, lines, version): num_lines = len(lines) return KnitContent(zip([version] * num_lines, lines)) class KnitAnnotateFactory(_KnitFactory): """Factory for creating annotated Content objects.""" annotated = True def parse_fulltext(self, content, version): """Convert fulltext to internal representation fulltext content is of the format revid(utf8) plaintext\n internal representation is of the format: (revid, plaintext) """ decode_utf8 = cache_utf8.decode lines = [] for line in content: origin, text = line.split(' ', 1) lines.append((decode_utf8(origin), text)) return KnitContent(lines) def parse_line_delta_iter(self, lines): for result_item in self.parse_line_delta[lines]: yield result_item def parse_line_delta(self, lines, version): """Convert a line based delta into internal representation. line delta is in the form of: intstart intend intcount 1..count lines: revid(utf8) newline\n internal representation is (start, end, count, [1..count tuples (revid, newline)]) """ decode_utf8 = cache_utf8.decode result = [] lines = iter(lines) next = lines.next # walk through the lines parsing. for header in lines: start, end, count = [int(n) for n in header.split(',')] contents = [] remaining = count while remaining: origin, text = next().split(' ', 1) remaining -= 1 contents.append((decode_utf8(origin), text)) result.append((start, end, count, contents)) return result def lower_fulltext(self, content): """convert a fulltext content record into a serializable form. see parse_fulltext which this inverts. """ encode_utf8 = cache_utf8.encode return ['%s %s' % (encode_utf8(o), t) for o, t in content._lines] def lower_line_delta(self, delta): """convert a delta into a serializable form. See parse_line_delta which this inverts. """ encode_utf8 = cache_utf8.encode out = [] for start, end, c, lines in delta: out.append('%d,%d,%d\n' % (start, end, c)) out.extend(encode_utf8(origin) + ' ' + text for origin, text in lines) return out class KnitPlainFactory(_KnitFactory): """Factory for creating plain Content objects.""" annotated = False def parse_fulltext(self, content, version): """This parses an unannotated fulltext. Note that this is not a noop - the internal representation has (versionid, line) - its just a constant versionid. """ return self.make(content, version) def parse_line_delta_iter(self, lines, version): while lines: header = lines.pop(0) start, end, c = [int(n) for n in header.split(',')] yield start, end, c, zip([version] * c, lines[:c]) del lines[:c] def parse_line_delta(self, lines, version): return list(self.parse_line_delta_iter(lines, version)) def lower_fulltext(self, content): return content.text() def lower_line_delta(self, delta): out = [] for start, end, c, lines in delta: out.append('%d,%d,%d\n' % (start, end, c)) out.extend([text for origin, text in lines]) return out def make_empty_knit(transport, relpath): """Construct a empty knit at the specified location.""" k = KnitVersionedFile(transport, relpath, 'w', KnitPlainFactory) k._data._open_file() class KnitVersionedFile(VersionedFile): """Weave-like structure with faster random access. A knit stores a number of texts and a summary of the relationships between them. Texts are identified by a string version-id. Texts are normally stored and retrieved as a series of lines, but can also be passed as single strings. Lines are stored with the trailing newline (if any) included, to avoid special cases for files with no final newline. Lines are composed of 8-bit characters, not unicode. The combination of these approaches should mean any 'binary' file can be safely stored and retrieved. """ def __init__(self, relpath, transport, file_mode=None, access_mode=None, factory=None, basis_knit=DEPRECATED_PARAMETER, delta=True, create=False, create_parent_dir=False, delay_create=False, dir_mode=None): """Construct a knit at location specified by relpath. :param create: If not True, only open an existing knit. :param create_parent_dir: If True, create the parent directory if creating the file fails. (This is used for stores with hash-prefixes that may not exist yet) :param delay_create: The calling code is aware that the knit won't actually be created until the first data is stored. """ if deprecated_passed(basis_knit): warnings.warn("KnitVersionedFile.__(): The basis_knit parameter is" " deprecated as of bzr 0.9.", DeprecationWarning, stacklevel=2) if access_mode is None: access_mode = 'w' super(KnitVersionedFile, self).__init__(access_mode) assert access_mode in ('r', 'w'), "invalid mode specified %r" % access_mode self.transport = transport self.filename = relpath self.factory = factory or KnitAnnotateFactory() self.writable = (access_mode == 'w') self.delta = delta self._index = _KnitIndex(transport, relpath + INDEX_SUFFIX, access_mode, create=create, file_mode=file_mode, create_parent_dir=create_parent_dir, delay_create=delay_create, dir_mode=dir_mode) self._data = _KnitData(transport, relpath + DATA_SUFFIX, access_mode, create=create and not len(self), file_mode=file_mode, create_parent_dir=create_parent_dir, delay_create=delay_create, dir_mode=dir_mode) def __repr__(self): return '%s(%s)' % (self.__class__.__name__, self.transport.abspath(self.filename)) def _add_delta(self, version_id, parents, delta_parent, sha1, noeol, delta): """See VersionedFile._add_delta().""" self._check_add(version_id, []) # should we check the lines ? self._check_versions_present(parents) present_parents = [] ghosts = [] parent_texts = {} for parent in parents: if not self.has_version(parent): ghosts.append(parent) else: present_parents.append(parent) if delta_parent is None: # reconstitute as full text. assert len(delta) == 1 or len(delta) == 0 if len(delta): assert delta[0][0] == 0 assert delta[0][1] == 0, delta[0][1] return super(KnitVersionedFile, self)._add_delta(version_id, parents, delta_parent, sha1, noeol, delta) digest = sha1 options = [] if noeol: options.append('no-eol') if delta_parent is not None: # determine the current delta chain length. # To speed the extract of texts the delta chain is limited # to a fixed number of deltas. This should minimize both # I/O and the time spend applying deltas. count = 0 delta_parents = [delta_parent] while count < 25: parent = delta_parents[0] method = self._index.get_method(parent) if method == 'fulltext': break delta_parents = self._index.get_parents(parent) count = count + 1 if method == 'line-delta': # did not find a fulltext in the delta limit. # just do a normal insertion. return super(KnitVersionedFile, self)._add_delta(version_id, parents, delta_parent, sha1, noeol, delta) options.append('line-delta') store_lines = self.factory.lower_line_delta(delta) where, size = self._data.add_record(version_id, digest, store_lines) self._index.add_version(version_id, options, where, size, parents) def _add_raw_records(self, records, data): """Add all the records 'records' with data pre-joined in 'data'. :param records: A list of tuples(version_id, options, parents, size). :param data: The data for the records. When it is written, the records are adjusted to have pos pointing into data by the sum of the preceding records sizes. """ # write all the data pos = self._data.add_raw_record(data) offset = 0 index_entries = [] for (version_id, options, parents, size) in records: index_entries.append((version_id, options, pos+offset, size, parents)) if self._data._do_cache: self._data._cache[version_id] = data[offset:offset+size] offset += size self._index.add_versions(index_entries) def enable_cache(self): """Start caching data for this knit""" self._data.enable_cache() def clear_cache(self): """Clear the data cache only.""" self._data.clear_cache() def copy_to(self, name, transport): """See VersionedFile.copy_to().""" # copy the current index to a temp index to avoid racing with local # writes transport.put_file_non_atomic(name + INDEX_SUFFIX + '.tmp', self.transport.get(self._index._filename)) # copy the data file f = self._data._open_file() try: transport.put_file(name + DATA_SUFFIX, f) finally: f.close() # move the copied index into place transport.move(name + INDEX_SUFFIX + '.tmp', name + INDEX_SUFFIX) def create_empty(self, name, transport, mode=None): return KnitVersionedFile(name, transport, factory=self.factory, delta=self.delta, create=True) def _fix_parents(self, version, new_parents): """Fix the parents list for version. This is done by appending a new version to the index with identical data except for the parents list. the parents list must be a superset of the current list. """ current_values = self._index._cache[version] assert set(current_values[4]).difference(set(new_parents)) == set() self._index.add_version(version, current_values[1], current_values[2], current_values[3], new_parents) def get_delta(self, version_id): """Get a delta for constructing version from some other version.""" if not self.has_version(version_id): raise RevisionNotPresent(version_id, self.filename) parents = self.get_parents(version_id) if len(parents): parent = parents[0] else: parent = None data_pos, data_size = self._index.get_position(version_id) data, sha1 = self._data.read_records(((version_id, data_pos, data_size),))[version_id] version_idx = self._index.lookup(version_id) noeol = 'no-eol' in self._index.get_options(version_id) if 'fulltext' == self._index.get_method(version_id): new_content = self.factory.parse_fulltext(data, version_idx) if parent is not None: reference_content = self._get_content(parent) old_texts = reference_content.text() else: old_texts = [] new_texts = new_content.text() delta_seq = KnitSequenceMatcher(None, old_texts, new_texts) return parent, sha1, noeol, self._make_line_delta(delta_seq, new_content) else: delta = self.factory.parse_line_delta(data, version_idx) return parent, sha1, noeol, delta def get_graph_with_ghosts(self): """See VersionedFile.get_graph_with_ghosts().""" graph_items = self._index.get_graph() return dict(graph_items) def get_sha1(self, version_id): """See VersionedFile.get_sha1().""" record_map = self._get_record_map([version_id]) method, content, digest, next = record_map[version_id] return digest @staticmethod def get_suffixes(): """See VersionedFile.get_suffixes().""" return [DATA_SUFFIX, INDEX_SUFFIX] def has_ghost(self, version_id): """True if there is a ghost reference in the file to version_id.""" # maybe we have it if self.has_version(version_id): return False # optimisable if needed by memoising the _ghosts set. items = self._index.get_graph() for node, parents in items: for parent in parents: if parent not in self._index._cache: if parent == version_id: return True return False def versions(self): """See VersionedFile.versions.""" return self._index.get_versions() def has_version(self, version_id): """See VersionedFile.has_version.""" return self._index.has_version(version_id) __contains__ = has_version def _merge_annotations(self, content, parents, parent_texts={}, delta=None, annotated=None): """Merge annotations for content. This is done by comparing the annotations based on changed to the text. """ if annotated: delta_seq = None for parent_id in parents: merge_content = self._get_content(parent_id, parent_texts) seq = KnitSequenceMatcher(None, merge_content.text(), content.text()) if delta_seq is None: # setup a delta seq to reuse. delta_seq = seq for i, j, n in seq.get_matching_blocks(): if n == 0: continue # this appears to copy (origin, text) pairs across to the new # content for any line that matches the last-checked parent. # FIXME: save the sequence control data for delta compression # against the most relevant parent rather than rediffing. content._lines[j:j+n] = merge_content._lines[i:i+n] if delta: if not annotated: reference_content = self._get_content(parents[0], parent_texts) new_texts = content.text() old_texts = reference_content.text() delta_seq = KnitSequenceMatcher(None, old_texts, new_texts) return self._make_line_delta(delta_seq, content) def _make_line_delta(self, delta_seq, new_content): """Generate a line delta from delta_seq and new_content.""" diff_hunks = [] for op in delta_seq.get_opcodes(): if op[0] == 'equal': continue diff_hunks.append((op[1], op[2], op[4]-op[3], new_content._lines[op[3]:op[4]])) return diff_hunks def _get_components_positions(self, version_ids): """Produce a map of position data for the components of versions. This data is intended to be used for retrieving the knit records. A dict of version_id to (method, data_pos, data_size, next) is returned. method is the way referenced data should be applied. data_pos is the position of the data in the knit. data_size is the size of the data in the knit. next is the build-parent of the version, or None for fulltexts. """ component_data = {} for version_id in version_ids: cursor = version_id while cursor is not None and cursor not in component_data: method = self._index.get_method(cursor) if method == 'fulltext': next = None else: next = self.get_parents(cursor)[0] data_pos, data_size = self._index.get_position(cursor) component_data[cursor] = (method, data_pos, data_size, next) cursor = next return component_data def _get_content(self, version_id, parent_texts={}): """Returns a content object that makes up the specified version.""" if not self.has_version(version_id): raise RevisionNotPresent(version_id, self.filename) cached_version = parent_texts.get(version_id, None) if cached_version is not None: return cached_version text_map, contents_map = self._get_content_maps([version_id]) return contents_map[version_id] def _check_versions_present(self, version_ids): """Check that all specified versions are present.""" version_ids = set(version_ids) for r in list(version_ids): if self._index.has_version(r): version_ids.remove(r) if version_ids: raise RevisionNotPresent(list(version_ids)[0], self.filename) def _add_lines_with_ghosts(self, version_id, parents, lines, parent_texts): """See VersionedFile.add_lines_with_ghosts().""" self._check_add(version_id, lines) return self._add(version_id, lines[:], parents, self.delta, parent_texts) def _add_lines(self, version_id, parents, lines, parent_texts): """See VersionedFile.add_lines.""" self._check_add(version_id, lines) self._check_versions_present(parents) return self._add(version_id, lines[:], parents, self.delta, parent_texts) def _check_add(self, version_id, lines): """check that version_id and lines are safe to add.""" assert self.writable, "knit is not opened for write" ### FIXME escape. RBC 20060228 if contains_whitespace(version_id): raise InvalidRevisionId(version_id, self.filename) if self.has_version(version_id): raise RevisionAlreadyPresent(version_id, self.filename) self._check_lines_not_unicode(lines) self._check_lines_are_lines(lines) def _add(self, version_id, lines, parents, delta, parent_texts): """Add a set of lines on top of version specified by parents. If delta is true, compress the text as a line-delta against the first parent. Any versions not present will be converted into ghosts. """ # 461 0 6546.0390 43.9100 bzrlib.knit:489(_add) # +400 0 889.4890 418.9790 +bzrlib.knit:192(lower_fulltext) # +461 0 1364.8070 108.8030 +bzrlib.knit:996(add_record) # +461 0 193.3940 41.5720 +bzrlib.knit:898(add_version) # +461 0 134.0590 18.3810 +bzrlib.osutils:361(sha_strings) # +461 0 36.3420 15.4540 +bzrlib.knit:146(make) # +1383 0 8.0370 8.0370 + # +61 0 13.5770 7.9190 +bzrlib.knit:199(lower_line_delta) # +61 0 963.3470 7.8740 +bzrlib.knit:427(_get_content) # +61 0 973.9950 5.2950 +bzrlib.knit:136(line_delta) # +61 0 1918.1800 5.2640 +bzrlib.knit:359(_merge_annotations) present_parents = [] ghosts = [] if parent_texts is None: parent_texts = {} for parent in parents: if not self.has_version(parent): ghosts.append(parent) else: present_parents.append(parent) if delta and not len(present_parents): delta = False digest = sha_strings(lines) options = [] if lines: if lines[-1][-1] != '\n': options.append('no-eol') lines[-1] = lines[-1] + '\n' if len(present_parents) and delta: # To speed the extract of texts the delta chain is limited # to a fixed number of deltas. This should minimize both # I/O and the time spend applying deltas. count = 0 delta_parents = present_parents while count < 25: parent = delta_parents[0] method = self._index.get_method(parent) if method == 'fulltext': break delta_parents = self._index.get_parents(parent) count = count + 1 if method == 'line-delta': delta = False lines = self.factory.make(lines, version_id) if delta or (self.factory.annotated and len(present_parents) > 0): # Merge annotations from parent texts if so is needed. delta_hunks = self._merge_annotations(lines, present_parents, parent_texts, delta, self.factory.annotated) if delta: options.append('line-delta') store_lines = self.factory.lower_line_delta(delta_hunks) else: options.append('fulltext') store_lines = self.factory.lower_fulltext(lines) where, size = self._data.add_record(version_id, digest, store_lines) self._index.add_version(version_id, options, where, size, parents) return lines def check(self, progress_bar=None): """See VersionedFile.check().""" def _clone_text(self, new_version_id, old_version_id, parents): """See VersionedFile.clone_text().""" # FIXME RBC 20060228 make fast by only inserting an index with null # delta. self.add_lines(new_version_id, parents, self.get_lines(old_version_id)) def get_lines(self, version_id): """See VersionedFile.get_lines().""" return self.get_line_list([version_id])[0] def _get_record_map(self, version_ids): """Produce a dictionary of knit records. The keys are version_ids, the values are tuples of (method, content, digest, next). method is the way the content should be applied. content is a KnitContent object. digest is the SHA1 digest of this version id after all steps are done next is the build-parent of the version, i.e. the leftmost ancestor. If the method is fulltext, next will be None. """ position_map = self._get_components_positions(version_ids) # c = component_id, m = method, p = position, s = size, n = next records = [(c, p, s) for c, (m, p, s, n) in position_map.iteritems()] record_map = {} for component_id, content, digest in \ self._data.read_records_iter(records): method, position, size, next = position_map[component_id] record_map[component_id] = method, content, digest, next return record_map def get_text(self, version_id): """See VersionedFile.get_text""" return self.get_texts([version_id])[0] def get_texts(self, version_ids): return [''.join(l) for l in self.get_line_list(version_ids)] def get_line_list(self, version_ids): """Return the texts of listed versions as a list of strings.""" text_map, content_map = self._get_content_maps(version_ids) return [text_map[v] for v in version_ids] def _get_content_maps(self, version_ids): """Produce maps of text and KnitContents :return: (text_map, content_map) where text_map contains the texts for the requested versions and content_map contains the KnitContents. Both dicts take version_ids as their keys. """ for version_id in version_ids: if not self.has_version(version_id): raise RevisionNotPresent(version_id, self.filename) record_map = self._get_record_map(version_ids) text_map = {} content_map = {} final_content = {} for version_id in version_ids: components = [] cursor = version_id while cursor is not None: method, data, digest, next = record_map[cursor] components.append((cursor, method, data, digest)) if cursor in content_map: break cursor = next content = None for component_id, method, data, digest in reversed(components): if component_id in content_map: content = content_map[component_id] else: version_idx = self._index.lookup(component_id) if method == 'fulltext': assert content is None content = self.factory.parse_fulltext(data, version_idx) elif method == 'line-delta': delta = self.factory.parse_line_delta(data[:], version_idx) content = content.copy() content._lines = self._apply_delta(content._lines, delta) content_map[component_id] = content if 'no-eol' in self._index.get_options(version_id): content = content.copy() line = content._lines[-1][1].rstrip('\n') content._lines[-1] = (content._lines[-1][0], line) final_content[version_id] = content # digest here is the digest from the last applied component. text = content.text() if sha_strings(text) != digest: raise KnitCorrupt(self.filename, 'sha-1 does not match %s' % version_id) text_map[version_id] = text return text_map, final_content def iter_lines_added_or_present_in_versions(self, version_ids=None): """See VersionedFile.iter_lines_added_or_present_in_versions().""" if version_ids is None: version_ids = self.versions() # we don't care about inclusions, the caller cares. # but we need to setup a list of records to visit. # we need version_id, position, length version_id_records = [] requested_versions = list(version_ids) # filter for available versions for version_id in requested_versions: if not self.has_version(version_id): raise RevisionNotPresent(version_id, self.filename) # get a in-component-order queue: version_ids = [] for version_id in self.versions(): if version_id in requested_versions: version_ids.append(version_id) data_pos, length = self._index.get_position(version_id) version_id_records.append((version_id, data_pos, length)) pb = bzrlib.ui.ui_factory.nested_progress_bar() count = 0 total = len(version_id_records) try: pb.update('Walking content.', count, total) for version_id, data, sha_value in \ self._data.read_records_iter(version_id_records): pb.update('Walking content.', count, total) method = self._index.get_method(version_id) version_idx = self._index.lookup(version_id) assert method in ('fulltext', 'line-delta') if method == 'fulltext': content = self.factory.parse_fulltext(data, version_idx) for line in content.text(): yield line else: delta = self.factory.parse_line_delta(data, version_idx) for start, end, count, lines in delta: for origin, line in lines: yield line count +=1 pb.update('Walking content.', total, total) pb.finished() except: pb.update('Walking content.', total, total) pb.finished() raise def num_versions(self): """See VersionedFile.num_versions().""" return self._index.num_versions() __len__ = num_versions def annotate_iter(self, version_id): """See VersionedFile.annotate_iter.""" content = self._get_content(version_id) for origin, text in content.annotate_iter(): yield origin, text def get_parents(self, version_id): """See VersionedFile.get_parents.""" # perf notes: # optimism counts! # 52554 calls in 1264 872 internal down from 3674 try: return self._index.get_parents(version_id) except KeyError: raise RevisionNotPresent(version_id, self.filename) def get_parents_with_ghosts(self, version_id): """See VersionedFile.get_parents.""" try: return self._index.get_parents_with_ghosts(version_id) except KeyError: raise RevisionNotPresent(version_id, self.filename) def get_ancestry(self, versions): """See VersionedFile.get_ancestry.""" if isinstance(versions, basestring): versions = [versions] if not versions: return [] self._check_versions_present(versions) return self._index.get_ancestry(versions) def get_ancestry_with_ghosts(self, versions): """See VersionedFile.get_ancestry_with_ghosts.""" if isinstance(versions, basestring): versions = [versions] if not versions: return [] self._check_versions_present(versions) return self._index.get_ancestry_with_ghosts(versions) #@deprecated_method(zero_eight) def walk(self, version_ids): """See VersionedFile.walk.""" # We take the short path here, and extract all relevant texts # and put them in a weave and let that do all the work. Far # from optimal, but is much simpler. # FIXME RB 20060228 this really is inefficient! from bzrlib.weave import Weave w = Weave(self.filename) ancestry = self.get_ancestry(version_ids) sorted_graph = topo_sort(self._index.get_graph()) version_list = [vid for vid in sorted_graph if vid in ancestry] for version_id in version_list: lines = self.get_lines(version_id) w.add_lines(version_id, self.get_parents(version_id), lines) for lineno, insert_id, dset, line in w.walk(version_ids): yield lineno, insert_id, dset, line def plan_merge(self, ver_a, ver_b): """See VersionedFile.plan_merge.""" ancestors_b = set(self.get_ancestry(ver_b)) def status_a(revision, text): if revision in ancestors_b: return 'killed-b', text else: return 'new-a', text ancestors_a = set(self.get_ancestry(ver_a)) def status_b(revision, text): if revision in ancestors_a: return 'killed-a', text else: return 'new-b', text annotated_a = self.annotate(ver_a) annotated_b = self.annotate(ver_b) plain_a = [t for (a, t) in annotated_a] plain_b = [t for (a, t) in annotated_b] blocks = KnitSequenceMatcher(None, plain_a, plain_b).get_matching_blocks() a_cur = 0 b_cur = 0 for ai, bi, l in blocks: # process all mismatched sections # (last mismatched section is handled because blocks always # includes a 0-length last block) for revision, text in annotated_a[a_cur:ai]: yield status_a(revision, text) for revision, text in annotated_b[b_cur:bi]: yield status_b(revision, text) # and now the matched section a_cur = ai + l b_cur = bi + l for text_a, text_b in zip(plain_a[ai:a_cur], plain_b[bi:b_cur]): assert text_a == text_b yield "unchanged", text_a class _KnitComponentFile(object): """One of the files used to implement a knit database""" def __init__(self, transport, filename, mode, file_mode=None, create_parent_dir=False, dir_mode=None): self._transport = transport self._filename = filename self._mode = mode self._file_mode = file_mode self._dir_mode = dir_mode self._create_parent_dir = create_parent_dir self._need_to_create = False def check_header(self, fp): line = fp.readline() if line != self.HEADER: raise KnitHeaderError(badline=line) def commit(self): """Commit is a nop.""" def __repr__(self): return '%s(%s)' % (self.__class__.__name__, self._filename) class _KnitIndex(_KnitComponentFile): """Manages knit index file. The index is already kept in memory and read on startup, to enable fast lookups of revision information. The cursor of the index file is always pointing to the end, making it easy to append entries. _cache is a cache for fast mapping from version id to a Index object. _history is a cache for fast mapping from indexes to version ids. The index data format is dictionary compressed when it comes to parent references; a index entry may only have parents that with a lover index number. As a result, the index is topological sorted. Duplicate entries may be written to the index for a single version id if this is done then the latter one completely replaces the former: this allows updates to correct version and parent information. Note that the two entries may share the delta, and that successive annotations and references MUST point to the first entry. The index file on disc contains a header, followed by one line per knit record. The same revision can be present in an index file more than once. The first occurrence gets assigned a sequence number starting from 0. The format of a single line is REVISION_ID FLAGS BYTE_OFFSET LENGTH( PARENT_ID|PARENT_SEQUENCE_ID)* :\n REVISION_ID is a utf8-encoded revision id FLAGS is a comma separated list of flags about the record. Values include no-eol, line-delta, fulltext. BYTE_OFFSET is the ascii representation of the byte offset in the data file that the the compressed data starts at. LENGTH is the ascii representation of the length of the data file. PARENT_ID a utf-8 revision id prefixed by a '.' that is a parent of REVISION_ID. PARENT_SEQUENCE_ID the ascii representation of the sequence number of a revision id already in the knit that is a parent of REVISION_ID. The ' :' marker is the end of record marker. partial writes: when a write is interrupted to the index file, it will result in a line that does not end in ' :'. If the ' :' is not present at the end of a line, or at the end of the file, then the record that is missing it will be ignored by the parser. When writing new records to the index file, the data is preceded by '\n' to ensure that records always start on new lines even if the last write was interrupted. As a result its normal for the last line in the index to be missing a trailing newline. One can be added with no harmful effects. """ HEADER = "# bzr knit index 8\n" # speed of knit parsing went from 280 ms to 280 ms with slots addition. # __slots__ = ['_cache', '_history', '_transport', '_filename'] def _cache_version(self, version_id, options, pos, size, parents): """Cache a version record in the history array and index cache. This is inlined into __init__ for performance. KEEP IN SYNC. (It saves 60ms, 25% of the __init__ overhead on local 4000 record indexes). """ # only want the _history index to reference the 1st index entry # for version_id if version_id not in self._cache: index = len(self._history) self._history.append(version_id) else: index = self._cache[version_id][5] self._cache[version_id] = (version_id, options, pos, size, parents, index) def __init__(self, transport, filename, mode, create=False, file_mode=None, create_parent_dir=False, delay_create=False, dir_mode=None): _KnitComponentFile.__init__(self, transport, filename, mode, file_mode=file_mode, create_parent_dir=create_parent_dir, dir_mode=dir_mode) self._cache = {} # position in _history is the 'official' index for a revision # but the values may have come from a newer entry. # so - wc -l of a knit index is != the number of unique names # in the knit. self._history = [] pb = bzrlib.ui.ui_factory.nested_progress_bar() try: count = 0 total = 1 try: pb.update('read knit index', count, total) fp = self._transport.get(self._filename) try: self.check_header(fp) # readlines reads the whole file at once: # bad for transports like http, good for local disk # we save 60 ms doing this one change ( # from calling readline each time to calling # readlines once. # probably what we want for nice behaviour on # http is a incremental readlines that yields, or # a check for local vs non local indexes, for l in fp.readlines(): rec = l.split() if len(rec) < 5 or rec[-1] != ':': # corrupt line. # FIXME: in the future we should determine if its a # short write - and ignore it # or a different failure, and raise. RBC 20060407 continue count += 1 total += 1 #pb.update('read knit index', count, total) # See self._parse_parents parents = [] for value in rec[4:-1]: if '.' == value[0]: # uncompressed reference parents.append(value[1:]) else: # this is 15/4000ms faster than isinstance, # (in lsprof) # this function is called thousands of times a # second so small variations add up. assert value.__class__ is str parents.append(self._history[int(value)]) # end self._parse_parents # self._cache_version(rec[0], # rec[1].split(','), # int(rec[2]), # int(rec[3]), # parents) # --- self._cache_version # only want the _history index to reference the 1st # index entry for version_id version_id = rec[0] if version_id not in self._cache: index = len(self._history) self._history.append(version_id) else: index = self._cache[version_id][5] self._cache[version_id] = (version_id, rec[1].split(','), int(rec[2]), int(rec[3]), parents, index) # --- self._cache_version finally: fp.close() except NoSuchFile, e: if mode != 'w' or not create: raise if delay_create: self._need_to_create = True else: self._transport.put_bytes_non_atomic(self._filename, self.HEADER, mode=self._file_mode) finally: pb.update('read knit index', total, total) pb.finished() def _parse_parents(self, compressed_parents): """convert a list of string parent values into version ids. ints are looked up in the index. .FOO values are ghosts and converted in to FOO. NOTE: the function is retained here for clarity, and for possible use in partial index reads. However bulk processing now has it inlined in __init__ for inner-loop optimisation. """ result = [] for value in compressed_parents: if value[-1] == '.': # uncompressed reference result.append(value[1:]) else: # this is 15/4000ms faster than isinstance, # this function is called thousands of times a # second so small variations add up. assert value.__class__ is str result.append(self._history[int(value)]) return result def get_graph(self): graph = [] for version_id, index in self._cache.iteritems(): graph.append((version_id, index[4])) return graph def get_ancestry(self, versions): """See VersionedFile.get_ancestry.""" # get a graph of all the mentioned versions: graph = {} pending = set(versions) while len(pending): version = pending.pop() parents = self._cache[version][4] # got the parents ok # trim ghosts parents = [parent for parent in parents if parent in self._cache] for parent in parents: # if not completed and not a ghost if parent not in graph: pending.add(parent) graph[version] = parents return topo_sort(graph.items()) def get_ancestry_with_ghosts(self, versions): """See VersionedFile.get_ancestry_with_ghosts.""" # get a graph of all the mentioned versions: graph = {} pending = set(versions) while len(pending): version = pending.pop() try: parents = self._cache[version][4] except KeyError: # ghost, fake it graph[version] = [] pass else: # got the parents ok for parent in parents: if parent not in graph: pending.add(parent) graph[version] = parents return topo_sort(graph.items()) def num_versions(self): return len(self._history) __len__ = num_versions def get_versions(self): return self._history def idx_to_name(self, idx): return self._history[idx] def lookup(self, version_id): assert version_id in self._cache return self._cache[version_id][5] def _version_list_to_index(self, versions): encode_utf8 = cache_utf8.encode result_list = [] for version in versions: if version in self._cache: # -- inlined lookup() -- result_list.append(str(self._cache[version][5])) # -- end lookup () -- else: result_list.append('.' + encode_utf8(version)) return ' '.join(result_list) def add_version(self, version_id, options, pos, size, parents): """Add a version record to the index.""" self.add_versions(((version_id, options, pos, size, parents),)) def add_versions(self, versions): """Add multiple versions to the index. :param versions: a list of tuples: (version_id, options, pos, size, parents). """ lines = [] encode_utf8 = cache_utf8.encode for version_id, options, pos, size, parents in versions: line = "\n%s %s %s %s %s :" % (encode_utf8(version_id), ','.join(options), pos, size, self._version_list_to_index(parents)) assert isinstance(line, str), \ 'content must be utf-8 encoded: %r' % (line,) lines.append(line) if not self._need_to_create: self._transport.append_bytes(self._filename, ''.join(lines)) else: sio = StringIO() sio.write(self.HEADER) sio.writelines(lines) sio.seek(0) self._transport.put_file_non_atomic(self._filename, sio, create_parent_dir=self._create_parent_dir, mode=self._file_mode, dir_mode=self._dir_mode) self._need_to_create = False # cache after writing, so that a failed write leads to missing cache # entries not extra ones. XXX TODO: RBC 20060502 in the event of a # failure, reload the index or flush it or some such, to prevent # writing records that did complete twice. for version_id, options, pos, size, parents in versions: self._cache_version(version_id, options, pos, size, parents) def has_version(self, version_id): """True if the version is in the index.""" return (version_id in self._cache) def get_position(self, version_id): """Return data position and size of specified version.""" return (self._cache[version_id][2], \ self._cache[version_id][3]) def get_method(self, version_id): """Return compression method of specified version.""" options = self._cache[version_id][1] if 'fulltext' in options: return 'fulltext' else: assert 'line-delta' in options return 'line-delta' def get_options(self, version_id): return self._cache[version_id][1] def get_parents(self, version_id): """Return parents of specified version ignoring ghosts.""" return [parent for parent in self._cache[version_id][4] if parent in self._cache] def get_parents_with_ghosts(self, version_id): """Return parents of specified version with ghosts.""" return self._cache[version_id][4] def check_versions_present(self, version_ids): """Check that all specified versions are present.""" version_ids = set(version_ids) for version_id in list(version_ids): if version_id in self._cache: version_ids.remove(version_id) if version_ids: raise RevisionNotPresent(list(version_ids)[0], self.filename) class _KnitData(_KnitComponentFile): """Contents of the knit data file""" def __init__(self, transport, filename, mode, create=False, file_mode=None, create_parent_dir=False, delay_create=False, dir_mode=None): _KnitComponentFile.__init__(self, transport, filename, mode, file_mode=file_mode, create_parent_dir=create_parent_dir, dir_mode=dir_mode) self._checked = False # TODO: jam 20060713 conceptually, this could spill to disk # if the cached size gets larger than a certain amount # but it complicates the model a bit, so for now just use # a simple dictionary self._cache = {} self._do_cache = False if create: if delay_create: self._need_to_create = create else: self._transport.put_bytes_non_atomic(self._filename, '', mode=self._file_mode) def enable_cache(self): """Enable caching of reads.""" self._do_cache = True def clear_cache(self): """Clear the record cache.""" self._do_cache = False self._cache = {} def _open_file(self): try: return self._transport.get(self._filename) except NoSuchFile: pass return None def _record_to_data(self, version_id, digest, lines): """Convert version_id, digest, lines into a raw data block. :return: (len, a StringIO instance with the raw data ready to read.) """ sio = StringIO() data_file = GzipFile(None, mode='wb', fileobj=sio) version_id_utf8 = cache_utf8.encode(version_id) data_file.writelines(chain( ["version %s %d %s\n" % (version_id_utf8, len(lines), digest)], lines, ["end %s\n" % version_id_utf8])) data_file.close() length= sio.tell() sio.seek(0) return length, sio def add_raw_record(self, raw_data): """Append a prepared record to the data file. :return: the offset in the data file raw_data was written. """ assert isinstance(raw_data, str), 'data must be plain bytes' if not self._need_to_create: return self._transport.append_bytes(self._filename, raw_data) else: self._transport.put_bytes_non_atomic(self._filename, raw_data, create_parent_dir=self._create_parent_dir, mode=self._file_mode, dir_mode=self._dir_mode) self._need_to_create = False return 0 def add_record(self, version_id, digest, lines): """Write new text record to disk. Returns the position in the file where it was written.""" size, sio = self._record_to_data(version_id, digest, lines) # write to disk if not self._need_to_create: start_pos = self._transport.append_file(self._filename, sio) else: self._transport.put_file_non_atomic(self._filename, sio, create_parent_dir=self._create_parent_dir, mode=self._file_mode, dir_mode=self._dir_mode) self._need_to_create = False start_pos = 0 if self._do_cache: self._cache[version_id] = sio.getvalue() return start_pos, size def _parse_record_header(self, version_id, raw_data): """Parse a record header for consistency. :return: the header and the decompressor stream. as (stream, header_record) """ df = GzipFile(mode='rb', fileobj=StringIO(raw_data)) rec = df.readline().split() if len(rec) != 4: raise KnitCorrupt(self._filename, 'unexpected number of elements in record header') if cache_utf8.decode(rec[1]) != version_id: raise KnitCorrupt(self._filename, 'unexpected version, wanted %r, got %r' % ( version_id, rec[1])) return df, rec def _parse_record(self, version_id, data): # profiling notes: # 4168 calls in 2880 217 internal # 4168 calls to _parse_record_header in 2121 # 4168 calls to readlines in 330 df, rec = self._parse_record_header(version_id, data) record_contents = df.readlines() l = record_contents.pop() assert len(record_contents) == int(rec[2]) if l != 'end %s\n' % cache_utf8.encode(version_id): raise KnitCorrupt(self._filename, 'unexpected version end line %r, wanted %r' % (l, version_id)) df.close() return record_contents, rec[3] def read_records_iter_raw(self, records): """Read text records from data file and yield raw data. This unpacks enough of the text record to validate the id is as expected but thats all. """ # setup an iterator of the external records: # uses readv so nice and fast we hope. if len(records): # grab the disk data needed. if self._cache: # Don't check _cache if it is empty needed_offsets = [(pos, size) for version_id, pos, size in records if version_id not in self._cache] else: needed_offsets = [(pos, size) for version_id, pos, size in records] raw_records = self._transport.readv(self._filename, needed_offsets) for version_id, pos, size in records: if version_id in self._cache: # This data has already been validated data = self._cache[version_id] else: pos, data = raw_records.next() if self._do_cache: self._cache[version_id] = data # validate the header df, rec = self._parse_record_header(version_id, data) df.close() yield version_id, data def read_records_iter(self, records): """Read text records from data file and yield result. The result will be returned in whatever is the fastest to read. Not by the order requested. Also, multiple requests for the same record will only yield 1 response. :param records: A list of (version_id, pos, len) entries :return: Yields (version_id, contents, digest) in the order read, not the order requested """ if not records: return if self._cache: # Skip records we have alread seen yielded_records = set() needed_records = set() for record in records: if record[0] in self._cache: if record[0] in yielded_records: continue yielded_records.add(record[0]) data = self._cache[record[0]] content, digest = self._parse_record(record[0], data) yield (record[0], content, digest) else: needed_records.add(record) needed_records = sorted(needed_records, key=operator.itemgetter(1)) else: needed_records = sorted(set(records), key=operator.itemgetter(1)) if not needed_records: return # The transport optimizes the fetching as well # (ie, reads continuous ranges.) readv_response = self._transport.readv(self._filename, [(pos, size) for version_id, pos, size in needed_records]) for (version_id, pos, size), (pos, data) in \ izip(iter(needed_records), readv_response): content, digest = self._parse_record(version_id, data) if self._do_cache: self._cache[version_id] = data yield version_id, content, digest def read_records(self, records): """Read records into a dictionary.""" components = {} for record_id, content, digest in \ self.read_records_iter(records): components[record_id] = (content, digest) return components class InterKnit(InterVersionedFile): """Optimised code paths for knit to knit operations.""" _matching_file_from_factory = KnitVersionedFile _matching_file_to_factory = KnitVersionedFile @staticmethod def is_compatible(source, target): """Be compatible with knits. """ try: return (isinstance(source, KnitVersionedFile) and isinstance(target, KnitVersionedFile)) except AttributeError: return False def join(self, pb=None, msg=None, version_ids=None, ignore_missing=False): """See InterVersionedFile.join.""" assert isinstance(self.source, KnitVersionedFile) assert isinstance(self.target, KnitVersionedFile) version_ids = self._get_source_version_ids(version_ids, ignore_missing) if not version_ids: return 0 pb = bzrlib.ui.ui_factory.nested_progress_bar() try: version_ids = list(version_ids) if None in version_ids: version_ids.remove(None) self.source_ancestry = set(self.source.get_ancestry(version_ids)) this_versions = set(self.target._index.get_versions()) needed_versions = self.source_ancestry - this_versions cross_check_versions = self.source_ancestry.intersection(this_versions) mismatched_versions = set() for version in cross_check_versions: # scan to include needed parents. n1 = set(self.target.get_parents_with_ghosts(version)) n2 = set(self.source.get_parents_with_ghosts(version)) if n1 != n2: # FIXME TEST this check for cycles being introduced works # the logic is we have a cycle if in our graph we are an # ancestor of any of the n2 revisions. for parent in n2: if parent in n1: # safe continue else: parent_ancestors = self.source.get_ancestry(parent) if version in parent_ancestors: raise errors.GraphCycleError([parent, version]) # ensure this parent will be available later. new_parents = n2.difference(n1) needed_versions.update(new_parents.difference(this_versions)) mismatched_versions.add(version) if not needed_versions and not mismatched_versions: return 0 full_list = topo_sort(self.source.get_graph()) version_list = [i for i in full_list if (not self.target.has_version(i) and i in needed_versions)] # plan the join: copy_queue = [] copy_queue_records = [] copy_set = set() for version_id in version_list: options = self.source._index.get_options(version_id) parents = self.source._index.get_parents_with_ghosts(version_id) # check that its will be a consistent copy: for parent in parents: # if source has the parent, we must : # * already have it or # * have it scheduled already # otherwise we don't care assert (self.target.has_version(parent) or parent in copy_set or not self.source.has_version(parent)) data_pos, data_size = self.source._index.get_position(version_id) copy_queue_records.append((version_id, data_pos, data_size)) copy_queue.append((version_id, options, parents)) copy_set.add(version_id) # data suck the join: count = 0 total = len(version_list) raw_datum = [] raw_records = [] for (version_id, raw_data), \ (version_id2, options, parents) in \ izip(self.source._data.read_records_iter_raw(copy_queue_records), copy_queue): assert version_id == version_id2, 'logic error, inconsistent results' count = count + 1 pb.update("Joining knit", count, total) raw_records.append((version_id, options, parents, len(raw_data))) raw_datum.append(raw_data) self.target._add_raw_records(raw_records, ''.join(raw_datum)) for version in mismatched_versions: # FIXME RBC 20060309 is this needed? n1 = set(self.target.get_parents_with_ghosts(version)) n2 = set(self.source.get_parents_with_ghosts(version)) # write a combined record to our history preserving the current # parents as first in the list new_parents = self.target.get_parents_with_ghosts(version) + list(n2.difference(n1)) self.target.fix_parents(version, new_parents) return count finally: pb.finished() InterVersionedFile.register_optimiser(InterKnit) class WeaveToKnit(InterVersionedFile): """Optimised code paths for weave to knit operations.""" _matching_file_from_factory = bzrlib.weave.WeaveFile _matching_file_to_factory = KnitVersionedFile @staticmethod def is_compatible(source, target): """Be compatible with weaves to knits.""" try: return (isinstance(source, bzrlib.weave.Weave) and isinstance(target, KnitVersionedFile)) except AttributeError: return False def join(self, pb=None, msg=None, version_ids=None, ignore_missing=False): """See InterVersionedFile.join.""" assert isinstance(self.source, bzrlib.weave.Weave) assert isinstance(self.target, KnitVersionedFile) version_ids = self._get_source_version_ids(version_ids, ignore_missing) if not version_ids: return 0 pb = bzrlib.ui.ui_factory.nested_progress_bar() try: version_ids = list(version_ids) self.source_ancestry = set(self.source.get_ancestry(version_ids)) this_versions = set(self.target._index.get_versions()) needed_versions = self.source_ancestry - this_versions cross_check_versions = self.source_ancestry.intersection(this_versions) mismatched_versions = set() for version in cross_check_versions: # scan to include needed parents. n1 = set(self.target.get_parents_with_ghosts(version)) n2 = set(self.source.get_parents(version)) # if all of n2's parents are in n1, then its fine. if n2.difference(n1): # FIXME TEST this check for cycles being introduced works # the logic is we have a cycle if in our graph we are an # ancestor of any of the n2 revisions. for parent in n2: if parent in n1: # safe continue else: parent_ancestors = self.source.get_ancestry(parent) if version in parent_ancestors: raise errors.GraphCycleError([parent, version]) # ensure this parent will be available later. new_parents = n2.difference(n1) needed_versions.update(new_parents.difference(this_versions)) mismatched_versions.add(version) if not needed_versions and not mismatched_versions: return 0 full_list = topo_sort(self.source.get_graph()) version_list = [i for i in full_list if (not self.target.has_version(i) and i in needed_versions)] # do the join: count = 0 total = len(version_list) for version_id in version_list: pb.update("Converting to knit", count, total) parents = self.source.get_parents(version_id) # check that its will be a consistent copy: for parent in parents: # if source has the parent, we must already have it assert (self.target.has_version(parent)) self.target.add_lines( version_id, parents, self.source.get_lines(version_id)) count = count + 1 for version in mismatched_versions: # FIXME RBC 20060309 is this needed? n1 = set(self.target.get_parents_with_ghosts(version)) n2 = set(self.source.get_parents(version)) # write a combined record to our history preserving the current # parents as first in the list new_parents = self.target.get_parents_with_ghosts(version) + list(n2.difference(n1)) self.target.fix_parents(version, new_parents) return count finally: pb.finished() InterVersionedFile.register_optimiser(WeaveToKnit) class KnitSequenceMatcher(difflib.SequenceMatcher): """Knit tuned sequence matcher. This is based on profiling of difflib which indicated some improvements for our usage pattern. """ def find_longest_match(self, alo, ahi, blo, bhi): """Find longest matching block in a[alo:ahi] and b[blo:bhi]. If isjunk is not defined: Return (i,j,k) such that a[i:i+k] is equal to b[j:j+k], where alo <= i <= i+k <= ahi blo <= j <= j+k <= bhi and for all (i',j',k') meeting those conditions, k >= k' i <= i' and if i == i', j <= j' In other words, of all maximal matching blocks, return one that starts earliest in a, and of all those maximal matching blocks that start earliest in a, return the one that starts earliest in b. >>> s = SequenceMatcher(None, " abcd", "abcd abcd") >>> s.find_longest_match(0, 5, 0, 9) (0, 4, 5) If isjunk is defined, first the longest matching block is determined as above, but with the additional restriction that no junk element appears in the block. Then that block is extended as far as possible by matching (only) junk elements on both sides. So the resulting block never matches on junk except as identical junk happens to be adjacent to an "interesting" match. Here's the same example as before, but considering blanks to be junk. That prevents " abcd" from matching the " abcd" at the tail end of the second sequence directly. Instead only the "abcd" can match, and matches the leftmost "abcd" in the second sequence: >>> s = SequenceMatcher(lambda x: x==" ", " abcd", "abcd abcd") >>> s.find_longest_match(0, 5, 0, 9) (1, 0, 4) If no blocks match, return (alo, blo, 0). >>> s = SequenceMatcher(None, "ab", "c") >>> s.find_longest_match(0, 2, 0, 1) (0, 0, 0) """ # CAUTION: stripping common prefix or suffix would be incorrect. # E.g., # ab # acab # Longest matching block is "ab", but if common prefix is # stripped, it's "a" (tied with "b"). UNIX(tm) diff does so # strip, so ends up claiming that ab is changed to acab by # inserting "ca" in the middle. That's minimal but unintuitive: # "it's obvious" that someone inserted "ac" at the front. # Windiff ends up at the same place as diff, but by pairing up # the unique 'b's and then matching the first two 'a's. a, b, b2j, isbjunk = self.a, self.b, self.b2j, self.isbjunk besti, bestj, bestsize = alo, blo, 0 # find longest junk-free match # during an iteration of the loop, j2len[j] = length of longest # junk-free match ending with a[i-1] and b[j] j2len = {} # nothing = [] b2jget = b2j.get for i in xrange(alo, ahi): # look at all instances of a[i] in b; note that because # b2j has no junk keys, the loop is skipped if a[i] is junk j2lenget = j2len.get newj2len = {} # changing b2j.get(a[i], nothing) to a try:KeyError pair produced the # following improvement # 704 0 4650.5320 2620.7410 bzrlib.knit:1336(find_longest_match) # +326674 0 1655.1210 1655.1210 + # +76519 0 374.6700 374.6700 + # to # 704 0 3733.2820 2209.6520 bzrlib.knit:1336(find_longest_match) # +211400 0 1147.3520 1147.3520 + # +76519 0 376.2780 376.2780 + try: js = b2j[a[i]] except KeyError: pass else: for j in js: # a[i] matches b[j] if j >= blo: if j >= bhi: break k = newj2len[j] = 1 + j2lenget(-1 + j, 0) if k > bestsize: besti, bestj, bestsize = 1 + i-k, 1 + j-k, k j2len = newj2len # Extend the best by non-junk elements on each end. In particular, # "popular" non-junk elements aren't in b2j, which greatly speeds # the inner loop above, but also means "the best" match so far # doesn't contain any junk *or* popular non-junk elements. while besti > alo and bestj > blo and \ not isbjunk(b[bestj-1]) and \ a[besti-1] == b[bestj-1]: besti, bestj, bestsize = besti-1, bestj-1, bestsize+1 while besti+bestsize < ahi and bestj+bestsize < bhi and \ not isbjunk(b[bestj+bestsize]) and \ a[besti+bestsize] == b[bestj+bestsize]: bestsize += 1 # Now that we have a wholly interesting match (albeit possibly # empty!), we may as well suck up the matching junk on each # side of it too. Can't think of a good reason not to, and it # saves post-processing the (possibly considerable) expense of # figuring out what to do with it. In the case of an empty # interesting match, this is clearly the right thing to do, # because no other kind of match is possible in the regions. while besti > alo and bestj > blo and \ isbjunk(b[bestj-1]) and \ a[besti-1] == b[bestj-1]: besti, bestj, bestsize = besti-1, bestj-1, bestsize+1 while besti+bestsize < ahi and bestj+bestsize < bhi and \ isbjunk(b[bestj+bestsize]) and \ a[besti+bestsize] == b[bestj+bestsize]: bestsize = bestsize + 1 return besti, bestj, bestsize