Mercurial > hg > mercurial-crew-with-dirclash
view mercurial/transaction.py @ 86:1b945e8ba67b
Friendlier exceptions for unknown node errors
author | mpm@selenic.com |
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date | Tue, 17 May 2005 12:20:29 -0800 |
parents | 42177b56b949 |
children | 589f507bb259 |
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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 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 class transaction: def __init__(self, opener, journal): self.opener = opener self.entries = [] self.map = {} self.journal = journal # abort here if the journal already exists if os.path.exists(self.journal): print "journal already exists, recovering" self.recover() self.file = open(self.journal, "w") def __del__(self): if self.entries: self.abort() 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 = [] os.unlink(self.journal) def abort(self): if not self.entries: return print "transaction abort!" for f, o in self.entries: self.opener(f, "a").truncate(o) self.entries = [] print "rollback completed" def recover(self): for l in open(self.journal).readlines(): f, o = l.split('\0') self.opener(f, "a").truncate(int(o)) os.unlink(self.journal)