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# storageutil.py - Storage functionality agnostic of backend implementation.
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#
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# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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from __future__ import absolute_import
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import hashlib
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import re
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import struct
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from ..i18n import _
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from ..node import (
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bin,
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nullid,
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nullrev,
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)
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from .. import (
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dagop,
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error,
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mdiff,
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pycompat,
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)
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from ..interfaces import repository
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_nullhash = hashlib.sha1(nullid)
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def hashrevisionsha1(text, p1, p2):
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"""Compute the SHA-1 for revision data and its parents.
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This hash combines both the current file contents and its history
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in a manner that makes it easy to distinguish nodes with the same
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content in the revision graph.
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"""
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# As of now, if one of the parent node is null, p2 is null
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if p2 == nullid:
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# deep copy of a hash is faster than creating one
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s = _nullhash.copy()
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s.update(p1)
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else:
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# none of the parent nodes are nullid
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if p1 < p2:
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a = p1
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b = p2
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else:
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a = p2
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b = p1
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s = hashlib.sha1(a)
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s.update(b)
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s.update(text)
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return s.digest()
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METADATA_RE = re.compile(b'\x01\n')
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def parsemeta(text):
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"""Parse metadata header from revision data.
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Returns a 2-tuple of (metadata, offset), where both can be None if there
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is no metadata.
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"""
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# text can be buffer, so we can't use .startswith or .index
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if text[:2] != b'\x01\n':
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return None, None
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s = METADATA_RE.search(text, 2).start()
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mtext = text[2:s]
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meta = {}
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for l in mtext.splitlines():
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k, v = l.split(b': ', 1)
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meta[k] = v
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return meta, s + 2
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def packmeta(meta, text):
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"""Add metadata to fulltext to produce revision text."""
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keys = sorted(meta)
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metatext = b''.join(b'%s: %s\n' % (k, meta[k]) for k in keys)
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return b'\x01\n%s\x01\n%s' % (metatext, text)
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def iscensoredtext(text):
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meta = parsemeta(text)[0]
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return meta and b'censored' in meta
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def filtermetadata(text):
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"""Extract just the revision data from source text.
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Returns ``text`` unless it has a metadata header, in which case we return
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a new buffer without hte metadata.
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"""
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if not text.startswith(b'\x01\n'):
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return text
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offset = text.index(b'\x01\n', 2)
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return text[offset + 2:]
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def filerevisioncopied(store, node):
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"""Resolve file revision copy metadata.
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Returns ``False`` if the file has no copy metadata. Otherwise a
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2-tuple of the source filename and node.
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"""
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if store.parents(node)[0] != nullid:
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return False
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meta = parsemeta(store.revision(node))[0]
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# copy and copyrev occur in pairs. In rare cases due to old bugs,
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# one can occur without the other. So ensure both are present to flag
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# as a copy.
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if meta and b'copy' in meta and b'copyrev' in meta:
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return meta[b'copy'], bin(meta[b'copyrev'])
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return False
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def filedataequivalent(store, node, filedata):
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"""Determines whether file data is equivalent to a stored node.
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Returns True if the passed file data would hash to the same value
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as a stored revision and False otherwise.
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When a stored revision is censored, filedata must be empty to have
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equivalence.
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When a stored revision has copy metadata, it is ignored as part
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of the compare.
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"""
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if filedata.startswith(b'\x01\n'):
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revisiontext = b'\x01\n\x01\n' + filedata
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else:
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revisiontext = filedata
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p1, p2 = store.parents(node)
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computednode = hashrevisionsha1(revisiontext, p1, p2)
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if computednode == node:
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return True
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# Censored files compare against the empty file.
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if store.iscensored(store.rev(node)):
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return filedata == b''
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# Renaming a file produces a different hash, even if the data
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# remains unchanged. Check if that's the case.
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if store.renamed(node):
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return store.read(node) == filedata
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return False
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def iterrevs(storelen, start=0, stop=None):
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"""Iterate over revision numbers in a store."""
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step = 1
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if stop is not None:
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if start > stop:
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step = -1
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stop += step
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if stop > storelen:
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stop = storelen
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else:
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stop = storelen
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return pycompat.xrange(start, stop, step)
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def fileidlookup(store, fileid, identifier):
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"""Resolve the file node for a value.
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``store`` is an object implementing the ``ifileindex`` interface.
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``fileid`` can be:
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* A 20 byte binary node.
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* An integer revision number
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* A 40 byte hex node.
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* A bytes that can be parsed as an integer representing a revision number.
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``identifier`` is used to populate ``error.LookupError`` with an identifier
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for the store.
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Raises ``error.LookupError`` on failure.
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"""
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if isinstance(fileid, int):
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try:
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return store.node(fileid)
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except IndexError:
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raise error.LookupError('%d' % fileid, identifier,
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_('no match found'))
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if len(fileid) == 20:
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try:
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store.rev(fileid)
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return fileid
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except error.LookupError:
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pass
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if len(fileid) == 40:
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try:
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rawnode = bin(fileid)
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store.rev(rawnode)
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return rawnode
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except TypeError:
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pass
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try:
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rev = int(fileid)
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if b'%d' % rev != fileid:
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raise ValueError
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try:
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return store.node(rev)
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except (IndexError, TypeError):
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pass
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except (ValueError, OverflowError):
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pass
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raise error.LookupError(fileid, identifier, _('no match found'))
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def resolvestripinfo(minlinkrev, tiprev, headrevs, linkrevfn, parentrevsfn):
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"""Resolve information needed to strip revisions.
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Finds the minimum revision number that must be stripped in order to
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strip ``minlinkrev``.
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Returns a 2-tuple of the minimum revision number to do that and a set
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of all revision numbers that have linkrevs that would be broken
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by that strip.
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``tiprev`` is the current tip-most revision. It is ``len(store) - 1``.
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``headrevs`` is an iterable of head revisions.
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``linkrevfn`` is a callable that receives a revision and returns a linked
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revision.
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``parentrevsfn`` is a callable that receives a revision number and returns
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an iterable of its parent revision numbers.
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"""
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brokenrevs = set()
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strippoint = tiprev + 1
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heads = {}
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futurelargelinkrevs = set()
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for head in headrevs:
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headlinkrev = linkrevfn(head)
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heads[head] = headlinkrev
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if headlinkrev >= minlinkrev:
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futurelargelinkrevs.add(headlinkrev)
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# This algorithm involves walking down the rev graph, starting at the
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# heads. Since the revs are topologically sorted according to linkrev,
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# once all head linkrevs are below the minlink, we know there are
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# no more revs that could have a linkrev greater than minlink.
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# So we can stop walking.
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while futurelargelinkrevs:
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strippoint -= 1
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linkrev = heads.pop(strippoint)
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if linkrev < minlinkrev:
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brokenrevs.add(strippoint)
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else:
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futurelargelinkrevs.remove(linkrev)
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for p in parentrevsfn(strippoint):
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if p != nullrev:
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plinkrev = linkrevfn(p)
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heads[p] = plinkrev
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if plinkrev >= minlinkrev:
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futurelargelinkrevs.add(plinkrev)
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return strippoint, brokenrevs
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def emitrevisions(store, nodes, nodesorder, resultcls, deltaparentfn=None,
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candeltafn=None, rawsizefn=None, revdifffn=None, flagsfn=None,
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deltamode=repository.CG_DELTAMODE_STD,
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revisiondata=False, assumehaveparentrevisions=False):
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"""Generic implementation of ifiledata.emitrevisions().
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Emitting revision data is subtly complex. This function attempts to
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encapsulate all the logic for doing so in a backend-agnostic way.
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``store``
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Object conforming to ``ifilestorage`` interface.
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``nodes``
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List of revision nodes whose data to emit.
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``resultcls``
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A type implementing the ``irevisiondelta`` interface that will be
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constructed and returned.
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``deltaparentfn`` (optional)
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Callable receiving a revision number and returning the revision number
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of a revision that the internal delta is stored against. This delta
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will be preferred over computing a new arbitrary delta.
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If not defined, a delta will always be computed from raw revision
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data.
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``candeltafn`` (optional)
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Callable receiving a pair of revision numbers that returns a bool
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indicating whether a delta between them can be produced.
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If not defined, it is assumed that any two revisions can delta with
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each other.
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``rawsizefn`` (optional)
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Callable receiving a revision number and returning the length of the
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``store.rawdata(rev)``.
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If not defined, ``len(store.rawdata(rev))`` will be called.
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``revdifffn`` (optional)
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Callable receiving a pair of revision numbers that returns a delta
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between them.
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If not defined, a delta will be computed by invoking mdiff code
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on ``store.revision()`` results.
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Defining this function allows a precomputed or stored delta to be
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used without having to compute on.
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``flagsfn`` (optional)
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Callable receiving a revision number and returns the integer flags
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value for it. If not defined, flags value will be 0.
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``deltamode``
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constaint on delta to be sent:
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* CG_DELTAMODE_STD - normal mode, try to reuse storage deltas,
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* CG_DELTAMODE_PREV - only delta against "prev",
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* CG_DELTAMODE_FULL - only issue full snapshot.
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Whether to send fulltext revisions instead of deltas, if allowed.
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``nodesorder``
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``revisiondata``
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``assumehaveparentrevisions``
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"""
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fnode = store.node
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frev = store.rev
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if nodesorder == 'nodes':
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revs = [frev(n) for n in nodes]
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elif nodesorder == 'linear':
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revs = set(frev(n) for n in nodes)
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revs = dagop.linearize(revs, store.parentrevs)
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else: # storage and default
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revs = sorted(frev(n) for n in nodes)
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prevrev = None
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if deltamode == repository.CG_DELTAMODE_PREV or assumehaveparentrevisions:
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prevrev = store.parentrevs(revs[0])[0]
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# Set of revs available to delta against.
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available = set()
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for rev in revs:
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if rev == nullrev:
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continue
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node = fnode(rev)
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p1rev, p2rev = store.parentrevs(rev)
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if deltaparentfn:
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deltaparentrev = deltaparentfn(rev)
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else:
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deltaparentrev = nullrev
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# Forced delta against previous mode.
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if deltamode == repository.CG_DELTAMODE_PREV:
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baserev = prevrev
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# We're instructed to send fulltext. Honor that.
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elif deltamode == repository.CG_DELTAMODE_FULL:
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baserev = nullrev
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# We're instructed to use p1. Honor that
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elif deltamode == repository.CG_DELTAMODE_P1:
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baserev = p1rev
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# There is a delta in storage. We try to use that because it
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# amounts to effectively copying data from storage and is
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# therefore the fastest.
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elif deltaparentrev != nullrev:
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# Base revision was already emitted in this group. We can
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# always safely use the delta.
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if deltaparentrev in available:
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baserev = deltaparentrev
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# Base revision is a parent that hasn't been emitted already.
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# Use it if we can assume the receiver has the parent revision.
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elif (assumehaveparentrevisions
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and deltaparentrev in (p1rev, p2rev)):
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baserev = deltaparentrev
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# No guarantee the receiver has the delta parent. Send delta
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# against last revision (if possible), which in the common case
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# should be similar enough to this revision that the delta is
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# reasonable.
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elif prevrev is not None:
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baserev = prevrev
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else:
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baserev = nullrev
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# Storage has a fulltext revision.
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# Let's use the previous revision, which is as good a guess as any.
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# There is definitely room to improve this logic.
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elif prevrev is not None:
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baserev = prevrev
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else:
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baserev = nullrev
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# But we can't actually use our chosen delta base for whatever
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# reason. Reset to fulltext.
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if baserev != nullrev and (candeltafn and not candeltafn(baserev, rev)):
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baserev = nullrev
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revision = None
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delta = None
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baserevisionsize = None
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if revisiondata:
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if store.iscensored(baserev) or store.iscensored(rev):
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try:
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revision = store.rawdata(node)
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except error.CensoredNodeError as e:
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revision = e.tombstone
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if baserev != nullrev:
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if rawsizefn:
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baserevisionsize = rawsizefn(baserev)
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else:
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baserevisionsize = len(store.rawdata(baserev))
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elif (baserev == nullrev
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and deltamode != repository.CG_DELTAMODE_PREV):
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revision = store.rawdata(node)
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available.add(rev)
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else:
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if revdifffn:
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delta = revdifffn(baserev, rev)
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else:
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delta = mdiff.textdiff(store.rawdata(baserev),
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store.rawdata(rev))
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available.add(rev)
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yield resultcls(
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node=node,
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p1node=fnode(p1rev),
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p2node=fnode(p2rev),
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basenode=fnode(baserev),
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flags=flagsfn(rev) if flagsfn else 0,
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baserevisionsize=baserevisionsize,
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revision=revision,
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delta=delta)
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prevrev = rev
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def deltaiscensored(delta, baserev, baselenfn):
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"""Determine if a delta represents censored revision data.
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``baserev`` is the base revision this delta is encoded against.
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``baselenfn`` is a callable receiving a revision number that resolves the
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length of the revision fulltext.
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Returns a bool indicating if the result of the delta represents a censored
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revision.
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"""
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# Fragile heuristic: unless new file meta keys are added alphabetically
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# preceding "censored", all censored revisions are prefixed by
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# "\1\ncensored:". A delta producing such a censored revision must be a
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# full-replacement delta, so we inspect the first and only patch in the
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# delta for this prefix.
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hlen = struct.calcsize(">lll")
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if len(delta) <= hlen:
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return False
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oldlen = baselenfn(baserev)
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newlen = len(delta) - hlen
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if delta[:hlen] != mdiff.replacediffheader(oldlen, newlen):
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return False
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add = "\1\ncensored:"
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addlen = len(add)
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return newlen >= addlen and delta[hlen:hlen + addlen] == add
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