Protocol switch from using generators to stream-like objects.
This allows the the pull side to precisely control how much data is
read so that another encapsulation layer is not needed.
An http client gets a response with a finite size. Because ssh clients
need to keep the stream open, we must not read more data than is sent
in a response. But due to the streaming nature of the changegroup
scheme, only the piece that's parsing the data knows how far it's
allowed to read.
This means the generator scheme isn't fine-grained enough. Instead we
need file-like objects with a read(x) method. This switches everything
for push/pull over to using file-like objects rather than generators.
# 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 <mpm@selenic.com>
#
# 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, report, 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.report = report
self.opener = opener
self.after = after
self.entries = []
self.map = {}
self.journal = journal
self.file = open(self.journal, "w")
def __del__(self):
if self.journal:
if self.entries: self.abort()
self.file.close()
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)
self.journal = None
def abort(self):
if not self.entries: return
self.report("transaction abort!\n")
for f, o in self.entries:
try:
self.opener(f, "a").truncate(o)
except:
self.report("failed to truncate %s\n" % f)
self.entries = []
self.report("rollback completed\n")
def rollback(opener, file):
for l in open(file).readlines():
f, o = l.split('\0')
opener(f, "a").truncate(int(o))
os.unlink(file)