Mercurial > hg > mercurial-crew-with-dirclash
view mercurial/transaction.py @ 456:d6ac88a738c4
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author | mpm@selenic.com |
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date | Thu, 23 Jun 2005 21:46:02 -0800 |
parents | 688d03d6997a |
children | 03f27b1381f9 |
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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 import util class transaction: def __init__(self, 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.opener = opener self.after = after self.entries = [] self.map = {} self.journal = journal 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 = [] if self.after: util.rename(self.journal, self.after) else: os.unlink(self.journal) def abort(self): if not self.entries: return print "transaction abort!" for f, o in self.entries: try: self.opener(f, "a").truncate(o) except: print "failed to truncate", f self.entries = [] print "rollback completed" def rollback(opener, file): for l in open(file).readlines(): f, o = l.split('\0') opener(f, "a").truncate(int(o)) os.unlink(file)