Mercurial > hg > mercurial-crew-with-dirclash

annotate mercurial/transaction.py @ 147:b6d8ed7aeba0

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A new ancestor algorithm The old ancestor algorithm could get fooled into returning ancestors closer to root than it ought to. Hopefully this one, which strictly orders its search by distance from room, will be foolproof.
author mpm@selenic.com
date Tue, 24 May 2005 23:11:44 -0800
parents 8d55c2d72c7c
children 5dcbe4d9a30c
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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, after = None):
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18 self.opener = opener
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19 self.after = after
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20 self.entries = []
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21 self.map = {}
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22 self.journal = journal
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23
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24 # abort here if the journal already exists
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25 if os.path.exists(self.journal):
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26 raise "journal already exists!"
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27
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28 self.file = open(self.journal, "w")
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30 def __del__(self):
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31 if self.entries: self.abort()
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32 try: os.unlink(self.journal)
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33 except: pass
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34
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35 def add(self, file, offset):
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36 if file in self.map: return
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37 self.entries.append((file, offset))
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38 self.map[file] = 1
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39 # add enough data to the journal to do the truncate
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40 self.file.write("%s\0%d\n" % (file, offset))
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41 self.file.flush()
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42
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43 def close(self):
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44 self.file.close()
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45 self.entries = []
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46 if self.after:
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47 os.rename(self.journal, self.after)
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48 else:
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49 os.unlink(self.journal)
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51 def abort(self):
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52 if not self.entries: return
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53
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54 print "transaction abort!"
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55
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56 for f, o in self.entries:
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57 try:
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58 self.opener(f, "a").truncate(o)
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59 except:
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60 print "failed to truncate", f
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62 self.entries = []
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63
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64 print "rollback completed"
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65
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66 def recover(self):
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67 for l in open(self.journal).readlines():
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68 f, o = l.split('\0')
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69 self.opener(f, "a").truncate(int(o))
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70 os.unlink(self.journal)
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