view mercurial/dirstateguard.py @ 45871:a985c4fb23ca

transaction: change list of journal entries into a dictionary

The transaction object used to keep a mapping table of path names to
journal entries and a list of journal entries consisting of path and
file offset to truncate on rollback. The offsets are used in three
cases. repair.strip and rollback process all of them in one go, but they
care about the order. For them, it is perfectly reasonable to read the
journal back from disk as both operations already involve at least one
system call per journal entry. The other consumer is the revlog logic
for moving from inline to external data storage. It doesn't care about
the order of the journal and just needs to original offset stored.
Further optimisations are possible here to move the in-memory journal to
a set(), but without memoisation of the original revlog size this could
turn it into O(n^2) behavior in worst case when many revlogs need to
migrated.

Differential Revision: https://phab.mercurial-scm.org/D9277

# dirstateguard.py - class to allow restoring dirstate after failure
#
# Copyright 2005-2007 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 __future__ import absolute_import

from .i18n import _

from . import (
    error,
    narrowspec,
    util,
)


class dirstateguard(util.transactional):
    '''Restore dirstate at unexpected failure.

    At the construction, this class does:

    - write current ``repo.dirstate`` out, and
    - save ``.hg/dirstate`` into the backup file

    This restores ``.hg/dirstate`` from backup file, if ``release()``
    is invoked before ``close()``.

    This just removes the backup file at ``close()`` before ``release()``.
    '''

    def __init__(self, repo, name):
        self._repo = repo
        self._active = False
        self._closed = False
        self._backupname = b'dirstate.backup.%s.%d' % (name, id(self))
        self._narrowspecbackupname = b'narrowspec.backup.%s.%d' % (
            name,
            id(self),
        )
        repo.dirstate.savebackup(repo.currenttransaction(), self._backupname)
        narrowspec.savewcbackup(repo, self._narrowspecbackupname)
        self._active = True

    def __del__(self):
        if self._active:  # still active
            # this may occur, even if this class is used correctly:
            # for example, releasing other resources like transaction
            # may raise exception before ``dirstateguard.release`` in
            # ``release(tr, ....)``.
            self._abort()

    def close(self):
        if not self._active:  # already inactivated
            msg = (
                _(b"can't close already inactivated backup: %s")
                % self._backupname
            )
            raise error.Abort(msg)

        self._repo.dirstate.clearbackup(
            self._repo.currenttransaction(), self._backupname
        )
        narrowspec.clearwcbackup(self._repo, self._narrowspecbackupname)
        self._active = False
        self._closed = True

    def _abort(self):
        narrowspec.restorewcbackup(self._repo, self._narrowspecbackupname)
        self._repo.dirstate.restorebackup(
            self._repo.currenttransaction(), self._backupname
        )
        self._active = False

    def release(self):
        if not self._closed:
            if not self._active:  # already inactivated
                msg = (
                    _(b"can't release already inactivated backup: %s")
                    % self._backupname
                )
                raise error.Abort(msg)
            self._abort()