Mercurial > public > mercurial-scm > hg-stable

annotate mercurial/transaction.py @ 0:9117c6561b0b

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Add back links from file revisions to changeset revisions Add simple transaction support Add hg verify Improve caching in revlog Fix a bunch of bugs Self-hosting now that the metadata is close to finalized
author mpm@selenic.com
date Tue, 03 May 2005 13:16:10 -0800
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children 8b64243ee17b
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1 # transaction.py - simple journalling scheme for mercurial
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2 #
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3 # This transaction scheme is intended to gracefully handle program
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4 # errors and interruptions. More serious failures like system crashes
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5 # can be recovered with an fsck-like tool. As the whole repository is
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6 # effectively log-structured, this should amount to simply truncating
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7 # anything that isn't referenced in the changelog.
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8 #
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9 # Copyright 2005 Matt Mackall <mpm@selenic.com>
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10 #
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11 # This software may be used and distributed according to the terms
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12 # of the GNU General Public License, incorporated herein by reference.
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13
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14 import os
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15
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16 class transaction:
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17 def __init__(self, opener, journal):
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18 self.opener = opener
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19 self.entries = []
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20 self.journal = journal
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21
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22 # abort here if the journal already exists
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23 if os.path.exists(self.journal):
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24 raise "Journal already exists!"
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25 self.file = open(self.journal, "w")
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27 def __del__(self):
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28 if self.entries: self.abort()
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29
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30 def add(self, file, offset):
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31 self.entries.append((file, offset))
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32 # add enough data to the journal to do the truncate
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33 self.file.write("%s\0%d\n" % (file, offset))
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34 self.file.flush()
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35
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36 def close(self):
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37 self.file.close()
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38 self.entries = []
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39 os.unlink(self.journal)
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40
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41 def abort(self):
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42 if not self.entries: return
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43
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44 print "transaction abort!"
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45
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46 for f, o in self.entries:
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47 self.opener(f, "a").truncate(o)
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48
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49 self.entries = []
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50
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51 try:
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52 os.unlink(self.journal)
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53 self.file.close()
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54 except: pass
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55
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56 print "rollback completed"
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57
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58 def recover(self):
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59 for l in open(self.journal).readlines():
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60 f, o = l.split('\0')
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61 self.opener(f, "a").truncate(int(o))
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62