mercurial/transaction.py

Propagate file list through dodiff

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Propagate file list through dodiff

This speeds up operations like 'hg diff Makefile'. Previously it would
walk the entire directory tree looking for changes. Now it will only
stat Makefile. Further, if Makefile appears untouched, it will skip
reading the manifest.

manifest hash: ab22a70a5511ed2d7a647f2cd15d129a88dccabf
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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 <[e-mail]>
#
# 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.map = {}
        self.journal = journal

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

    def __del__(self):
        if self.entries: self.abort()
        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:
            util.rename(self.journal, self.after)
        else:
            os.unlink(self.journal)

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

        print "transaction abort!"

        for f, o in self.entries:
            try:
                self.opener(f, "a").truncate(o)
            except:
                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))
    os.unlink(file)