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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, 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)
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