view mercurial/transaction.py @ 859:6390c377a9e6

Trap OSError when deleting env vars On the other OS, it seems that case insensitivity for environment vars can bite users when using some unknown combination of python 2.4.1 and win2kSP4+minsys (and probably other vversions of these softwares). The best way to avoid problems in those weird cases is to ignore OSError exception during env var deletion.
author Edouard Gomez <ed.gomez@free.fr>
date Tue, 09 Aug 2005 09:36:34 -0800
parents 0902ffece4b4
children 6d5a62a549fa
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# transaction.py - 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 <mpm@selenic.com>
#
# 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, report, 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.report = report
        self.opener = opener
        self.after = after
        self.entries = []
        self.map = {}
        self.journal = journal

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

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

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

    def close(self):
        self.file.close()
        self.entries = []
        if self.after:
            self.after()
        else:
            os.unlink(self.journal)
        self.journal = None

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

        self.report("transaction abort!\n")

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

        self.entries = []

        self.report("rollback completed\n")

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