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A censored revision stored in a revlog should have the censored revlog index flag bit set. This implies we must know if a revision is censored before we add it to the revlog. When adding revisions from exchanged deltas, we would prefer to determine this flag without decoding every single full text. This change introduces a heuristic based on assumptions around the Mercurial delta format and filelog metadata. Since deltas which produce a censored revision must be full-replacement deltas, we can read the delta's first bytes to check the filelog metadata. Since "censored" is the alphabetically first filelog metadata key, censored filelog revisions have a well-known prefix we can look for. For more on the design and background of the censorship feature, see: http://mercurial.selenic.com/wiki/CensorPlan
130 lines
4.1 KiB
Python
130 lines
4.1 KiB
Python
# filelog.py - file history class for mercurial
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#
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# Copyright 2005-2007 Matt Mackall <mpm@selenic.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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import error, mdiff, revlog
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import re, struct
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_mdre = re.compile('\1\n')
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def parsemeta(text):
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"""return (metadatadict, keylist, metadatasize)"""
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# text can be buffer, so we can't use .startswith or .index
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if text[:2] != '\1\n':
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return None, None
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s = _mdre.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(": ", 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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keys = sorted(meta.iterkeys())
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metatext = "".join("%s: %s\n" % (k, meta[k]) for k in keys)
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return "\1\n%s\1\n%s" % (metatext, text)
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def _censoredtext(text):
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m, offs = parsemeta(text)
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return m and "censored" in m
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class filelog(revlog.revlog):
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def __init__(self, opener, path):
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super(filelog, self).__init__(opener,
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"/".join(("data", path + ".i")))
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def read(self, node):
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t = self.revision(node)
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if not t.startswith('\1\n'):
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return t
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s = t.index('\1\n', 2)
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return t[s + 2:]
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def add(self, text, meta, transaction, link, p1=None, p2=None):
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if meta or text.startswith('\1\n'):
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text = packmeta(meta, text)
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return self.addrevision(text, transaction, link, p1, p2)
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def renamed(self, node):
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if self.parents(node)[0] != revlog.nullid:
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return False
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t = self.revision(node)
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m = parsemeta(t)[0]
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if m and "copy" in m:
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return (m["copy"], revlog.bin(m["copyrev"]))
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return False
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def size(self, rev):
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"""return the size of a given revision"""
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# for revisions with renames, we have to go the slow way
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node = self.node(rev)
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if self.renamed(node):
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return len(self.read(node))
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if self.iscensored(rev):
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return 0
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# XXX if self.read(node).startswith("\1\n"), this returns (size+4)
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return super(filelog, self).size(rev)
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def cmp(self, node, text):
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"""compare text with a given file revision
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returns True if text is different than what is stored.
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"""
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t = text
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if text.startswith('\1\n'):
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t = '\1\n\1\n' + text
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samehashes = not super(filelog, self).cmp(node, t)
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if samehashes:
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return False
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# censored files compare against the empty file
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if self.iscensored(self.rev(node)):
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return text != ''
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# renaming a file produces a different hash, even if the data
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# remains unchanged. Check if it's the case (slow):
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if self.renamed(node):
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t2 = self.read(node)
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return t2 != text
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return True
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def checkhash(self, text, p1, p2, node, rev=None):
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try:
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super(filelog, self).checkhash(text, p1, p2, node, rev=rev)
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except error.RevlogError:
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if _censoredtext(text):
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raise error.CensoredNodeError(self.indexfile, node, text)
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raise
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def iscensored(self, rev):
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"""Check if a file revision is censored."""
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return self.flags(rev) & revlog.REVIDX_ISCENSORED
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def _peek_iscensored(self, baserev, delta, flush):
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"""Quickly check if a delta produces a censored revision."""
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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 = self.rawsize(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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