Mercurial > hg
view mercurial/filelog.py @ 30446:b324b4e431e5
posix: give checkexec a fast path; keep the check files and test read only
Before, Mercurial would create a new temporary file every time, stat it, change
its exec mode, stat it again, and delete it. Most of this dance was done to
handle the rare and not-so-essential case of VFAT mounts on unix. The cost of
that was paid by the much more common and important case of using normal file
systems.
Instead, try to create and preserve .hg/cache/checkisexec and
.hg/cache/checknoexec with and without exec flag set. If the files exist and
have correct exec flags set, we can conclude that that file system supports the
exec flag. Best case, the whole exec check can thus be done with two stat
calls. Worst case, we delete the wrong files and check as usual. That will be
because temporary loss of exec bit or on file systems without support for the
exec bit. In that case we check as we did before, with the additional overhead
of one extra stat call.
It is possible that this different test algorithm in some cases on odd file
systems will give different behaviour. Again, I think it will be rare and
special cases and I think it is worth the risk.
test-clone.t happens to show the situation where checkisexec is left behind
from the old style check, while checknoexec only will be created next time a
exec check will be performed.
author | Mads Kiilerich <madski@unity3d.com> |
---|---|
date | Wed, 14 Jan 2015 01:15:26 +0100 |
parents | 34bd1a5eef5b |
children | be5b2098a817 |
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# filelog.py - file history class for mercurial # # Copyright 2005-2007 Matt Mackall <mpm@selenic.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from __future__ import absolute_import import re import struct from . import ( error, mdiff, revlog, ) _mdre = re.compile('\1\n') def parsemeta(text): """return (metadatadict, keylist, metadatasize)""" # text can be buffer, so we can't use .startswith or .index if text[:2] != '\1\n': return None, None s = _mdre.search(text, 2).start() mtext = text[2:s] meta = {} for l in mtext.splitlines(): k, v = l.split(": ", 1) meta[k] = v return meta, (s + 2) def packmeta(meta, text): keys = sorted(meta.iterkeys()) metatext = "".join("%s: %s\n" % (k, meta[k]) for k in keys) return "\1\n%s\1\n%s" % (metatext, text) def _censoredtext(text): m, offs = parsemeta(text) return m and "censored" in m class filelog(revlog.revlog): def __init__(self, opener, path): super(filelog, self).__init__(opener, "/".join(("data", path + ".i"))) def read(self, node): t = self.revision(node) if not t.startswith('\1\n'): return t s = t.index('\1\n', 2) return t[s + 2:] def add(self, text, meta, transaction, link, p1=None, p2=None): if meta or text.startswith('\1\n'): text = packmeta(meta, text) return self.addrevision(text, transaction, link, p1, p2) def renamed(self, node): if self.parents(node)[0] != revlog.nullid: return False t = self.revision(node) m = parsemeta(t)[0] if m and "copy" in m: return (m["copy"], revlog.bin(m["copyrev"])) return False def size(self, rev): """return the size of a given revision""" # for revisions with renames, we have to go the slow way node = self.node(rev) if self.renamed(node): return len(self.read(node)) if self.iscensored(rev): return 0 # XXX if self.read(node).startswith("\1\n"), this returns (size+4) return super(filelog, self).size(rev) def cmp(self, node, text): """compare text with a given file revision returns True if text is different than what is stored. """ t = text if text.startswith('\1\n'): t = '\1\n\1\n' + text samehashes = not super(filelog, self).cmp(node, t) if samehashes: return False # censored files compare against the empty file if self.iscensored(self.rev(node)): return text != '' # renaming a file produces a different hash, even if the data # remains unchanged. Check if it's the case (slow): if self.renamed(node): t2 = self.read(node) return t2 != text return True def checkhash(self, text, p1, p2, node, rev=None): try: super(filelog, self).checkhash(text, p1, p2, node, rev=rev) except error.RevlogError: if _censoredtext(text): raise error.CensoredNodeError(self.indexfile, node, text) raise def iscensored(self, rev): """Check if a file revision is censored.""" return self.flags(rev) & revlog.REVIDX_ISCENSORED def _peek_iscensored(self, baserev, delta, flush): """Quickly check if a delta produces a censored revision.""" # Fragile heuristic: unless new file meta keys are added alphabetically # preceding "censored", all censored revisions are prefixed by # "\1\ncensored:". A delta producing such a censored revision must be a # full-replacement delta, so we inspect the first and only patch in the # delta for this prefix. hlen = struct.calcsize(">lll") if len(delta) <= hlen: return False oldlen = self.rawsize(baserev) newlen = len(delta) - hlen if delta[:hlen] != mdiff.replacediffheader(oldlen, newlen): return False add = "\1\ncensored:" addlen = len(add) return newlen >= addlen and delta[hlen:hlen + addlen] == add