view mercurial/transaction.py @ 13750:7eb82f88e157

# User Dan Villiom Podlaski Christiansen <[e-mail]>
# Date 1289564504 -3600
# Node ID b75264c15cc888cf38c3c7b8f619801e3c2589c7
# Parent  89b2e5d940f669e590096c6be70eee61c9172fff
revsets: overload the branch() revset to also take a branch name.

This should only change semantics in the specific case of a tag/branch
conflict where the tag wasn't done on the branch with the same
name. Previously, branch(whatever) would resolve to the branch of the
tag in that case, whereas now it will resolve to the branch of the
name. The previous behaviour, while documented, seemed very
counter-intuitive to me.

An alternate approach would be to introduce a new revset such as
branchname() or namedbranch(). While this would retain backwards
compatibility, the distinction between it and branch() would not be
readily apparent to users. The most intuitive behaviour would be to
have branch(x) require 'x' to be a branch name, and something like
branchof(x) or samebranch(x) do what branch(x) currently
does. Unfortunately, our backwards compatibility guarantees prevent us
from doing that.

Please note that while 'hg tag' guards against shadowing a branch, 'hg
branch' does not. Besides, even if it did, that wouldn't solve the
issue of conversions with such tags and branches...

# 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 <[e-mail]>
#
# 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)