view mercurial/ @ 3420:52617d992eed

Report branch for hg log and friends
author Matt Mackall <>
date Tue, 17 Oct 2006 18:30:18 -0500
parents 345bac2bc4ec
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# - simple journalling scheme for mercurial
# This transaction scheme is intended to gracefully handle program
# errors and interruptions. More serious failures like system crashes
# can be recovered with an fsck-like tool. As the whole repository is
# effectively log-structured, this should amount to simply truncating
# anything that isn't referenced in the changelog.
# Copyright 2005, 2006 Matt Mackall <>
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

from demandload import demandload
from i18n import gettext as _
demandload(globals(), 'os')

class transaction(object):
    def __init__(self, report, opener, journal, after=None):
        self.journal = None

        # abort here if the journal already exists
        if os.path.exists(journal):
            raise AssertionError(_("journal already exists - run hg recover"))

        self.count = 1 = report
        self.opener = opener
        self.after = after
        self.entries = [] = {}
        self.journal = journal

        self.file = open(self.journal, "w")

    def __del__(self):
        if self.journal:
            if self.entries: self.abort()
            try: os.unlink(self.journal)
            except: pass

    def add(self, file, offset, data=None):
        if file in return
        self.entries.append((file, offset, data))[file] = len(self.entries) - 1
        # add enough data to the journal to do the truncate
        self.file.write("%s\0%d\n" % (file, offset))

    def find(self, file):
        if file in
            return self.entries[[file]]
        return None

    def replace(self, file, offset, data=None):
        if file not in
            raise KeyError(file)
        index =[file]
        self.entries[index] = (file, offset, data)
        self.file.write("%s\0%d\n" % (file, offset))

    def nest(self):
        self.count += 1
        return self

    def running(self):
        return self.count > 0

    def close(self):
        self.count -= 1
        if self.count != 0:
        self.entries = []
        if self.after:
        self.journal = None

    def abort(self):
        if not self.entries: return"transaction abort!\n"))

        for f, o, ignore in self.entries:
                self.opener(f, "a").truncate(o)
      "failed to truncate %s\n") % f)

        self.entries = []"rollback completed\n"))

def rollback(opener, file):
    files = {}
    for l in open(file).readlines():
        f, o = l.split('\0')
        files[f] = o
    for f in files:
        o = files[f]
        opener(f, "a").truncate(int(o))