view mercurial/ @ 558:0ceea19182a9

transaction: __del__ should do nothing if the journal already exists -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 transaction: __del__ should do nothing if the journal already exists manifest hash: c85f747ca762b7c446d306cbd7a20f8e566557fb -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (GNU/Linux) iD8DBQFCxXbTywK+sNU5EO8RAvjsAKCcTSzN9OjtoAdaZgtjDs9380ia7ACfcXsx FcNESqr4nX9b97WTGszJs48= =C2sL -----END PGP SIGNATURE-----
date Fri, 01 Jul 2005 09:01:07 -0800
parents 03f27b1381f9
children fbfbd4e506c3
line wrap: on
line source

# - 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 Matt Mackall <>
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

import os
import util

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

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

        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):
        if file in return
        self.entries.append((file, offset))[file] = 1
        # add enough data to the journal to do the truncate
        self.file.write("%s\0%d\n" % (file, offset))

    def close(self):
        self.entries = []
        if self.after:
            util.rename(self.journal, self.after)

    def abort(self):
        if not self.entries: return

        print "transaction abort!"

        for f, o in self.entries:
                self.opener(f, "a").truncate(o)
                print "failed to truncate", f

        self.entries = []

        print "rollback completed"

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