+
−# 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, 2006 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 i18n import _
+
−import os, errno
+
−import error, util
+
−
+
−def active(func):
+
−    def _active(self, *args, **kwds):
+
−        if self.count == 0:
+
−            raise error.Abort(_(
+
−                'cannot use transaction when it is already committed/aborted'))
+
−        return func(self, *args, **kwds)
+
−    return _active
+
−
+
−def _playback(journal, report, opener, entries, unlink=True):
+
−    for f, o, ignore in entries:
+
−        if o or not unlink:
+
−            try:
+
−                fp = opener(f, 'a')
+
−                fp.truncate(o)
+
−                fp.close()
+
−            except IOError:
+
−                report(_("failed to truncate %s\n") % f)
+
−                raise
+
−        else:
+
−            try:
+
−                fp = opener(f)
+
−                fn = fp.name
+
−                fp.close()
+
−                util.unlink(fn)
+
−            except (IOError, OSError), inst:
+
−                if inst.errno != errno.ENOENT:
+
−                    raise
+
−    util.unlink(journal)
+
−
+
−class transaction(object):
+
−    def __init__(self, report, opener, journal, after=None, createmode=None):
+
−        self.count = 1
+
−        self.usages = 1
+
−        self.report = report
+
−        self.opener = opener
+
−        self.after = after
+
−        self.entries = []
+
−        self.map = {}
+
−        self.journal = journal
+
−        self._queue = []
+
−
+
−        self.file = util.posixfile(self.journal, "w")
+
−        if createmode is not None:
+
−            os.chmod(self.journal, createmode & 0666)
+
−
+
−    def __del__(self):
+
−        if self.journal:
+
−            self._abort()
+
−
+
−    @active
+
−    def startgroup(self):
+
−        self._queue.append([])
+
−
+
−    @active
+
−    def endgroup(self):
+
−        q = self._queue.pop()
+
−        d = ''.join(['%s\0%d\n' % (x[0], x[1]) for x in q])
+
−        self.entries.extend(q)
+
−        self.file.write(d)
+
−        self.file.flush()
+
−
+
−    @active
+
−    def add(self, file, offset, data=None):
+
−        if file in self.map:
+
−            return
+
−        if self._queue:
+
−            self._queue[-1].append((file, offset, data))
+
−            return
+
−
+
−        self.entries.append((file, offset, data))
+
−        self.map[file] = len(self.entries) - 1
+
−        # add enough data to the journal to do the truncate
+
−        self.file.write("%s\0%d\n" % (file, offset))
+
−        self.file.flush()
+
−
+
−    @active
+
−    def find(self, file):
+
−        if file in self.map:
+
−            return self.entries[self.map[file]]
+
−        return None
+
−
+
−    @active
+
−    def replace(self, file, offset, data=None):
+
−        '''
+
−        replace can only replace already committed entries
+
−        that are not pending in the queue
+
−        '''
+
−
+
−        if file not in self.map:
+
−            raise KeyError(file)
+
−        index = self.map[file]
+
−        self.entries[index] = (file, offset, data)
+
−        self.file.write("%s\0%d\n" % (file, offset))
+
−        self.file.flush()
+
−
+
−    @active
+
−    def nest(self):
+
−        self.count += 1
+
−        self.usages += 1
+
−        return self
+
−
+
−    def release(self):
+
−        if self.count > 0:
+
−            self.usages -= 1
+
−        # if the transaction scopes are left without being closed, fail
+
−        if self.count > 0 and self.usages == 0:
+
−            self._abort()
+
−
+
−    def running(self):
+
−        return self.count > 0
+
−
+
−    @active
+
−    def close(self):
+
−        '''commit the transaction'''
+
−        self.count -= 1
+
−        if self.count != 0:
+
−            return
+
−        self.file.close()
+
−        self.entries = []
+
−        if self.after:
+
−            self.after()
+
−        if os.path.isfile(self.journal):
+
−            util.unlink(self.journal)
+
−        self.journal = None
+
−
+
−    @active
+
−    def abort(self):
+
−        '''abort the transaction (generally called on error, or when the
+
−        transaction is not explicitly committed before going out of
+
−        scope)'''
+
−        self._abort()
+
−
+
−    def _abort(self):
+
−        self.count = 0
+
−        self.usages = 0
+
−        self.file.close()
+
−
+
−        try:
+
−            if not self.entries:
+
−                if self.journal:
+
−                    util.unlink(self.journal)
+
−                return
+
−
+
−            self.report(_("transaction abort!\n"))
+
−
+
−            try:
+
−                _playback(self.journal, self.report, self.opener,
+
−                          self.entries, False)
+
−                self.report(_("rollback completed\n"))
+
−            except:
+
−                self.report(_("rollback failed - please run hg recover\n"))
+
−        finally:
+
−            self.journal = None
+
−
+
−
+
−def rollback(opener, file, report):
+
−    entries = []
+
−
+
−    fp = util.posixfile(file)
+
−    lines = fp.readlines()
+
−    fp.close()
+
−    for l in lines:
+
−        f, o = l.split('\0')
+
−        entries.append((f, int(o), None))
+
−
+
−    _playback(file, report, opener, entries)