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1 | 1 | # transaction.py - simple journalling scheme for mercurial |
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2 | 2 | # |
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3 | 3 | # This transaction scheme is intended to gracefully handle program |
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4 | 4 | # errors and interruptions. More serious failures like system crashes |
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5 | 5 | # can be recovered with an fsck-like tool. As the whole repository is |
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6 | 6 | # effectively log-structured, this should amount to simply truncating |
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7 | 7 | # anything that isn't referenced in the changelog. |
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8 | 8 | # |
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9 | 9 | # Copyright 2005 Matt Mackall <mpm@selenic.com> |
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10 | 10 | # |
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11 | 11 | # This software may be used and distributed according to the terms |
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12 | 12 | # of the GNU General Public License, incorporated herein by reference. |
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13 | 13 | |
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14 | 14 | import os |
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15 | 15 | import util |
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16 | 16 | |
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17 | 17 | class transaction: |
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18 | 18 | def __init__(self, opener, journal, after = None): |
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19 | 19 | self.journal = None |
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20 | 20 | |
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21 | 21 | # abort here if the journal already exists |
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22 | 22 | if os.path.exists(journal): |
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23 | 23 | raise "journal already exists - run hg recover" |
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24 | 24 | |
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25 | 25 | self.opener = opener |
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26 | 26 | self.after = after |
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27 | 27 | self.entries = [] |
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28 | 28 | self.map = {} |
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29 | 29 | self.journal = journal |
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30 | 30 | |
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31 | 31 | self.file = open(self.journal, "w") |
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32 | 32 | |
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33 | 33 | def __del__(self): |
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34 | 34 | if self.journal: |
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35 | 35 | if self.entries: self.abort() |
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36 | 36 | self.file.close() |
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37 | 37 | try: os.unlink(self.journal) |
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38 | 38 | except: pass |
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39 | 39 | |
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40 | 40 | def add(self, file, offset): |
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41 | 41 | if file in self.map: return |
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42 | 42 | self.entries.append((file, offset)) |
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43 | 43 | self.map[file] = 1 |
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44 | 44 | # add enough data to the journal to do the truncate |
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45 | 45 | self.file.write("%s\0%d\n" % (file, offset)) |
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46 | 46 | self.file.flush() |
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47 | 47 | |
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48 | 48 | def close(self): |
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49 | 49 | self.file.close() |
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50 | 50 | self.entries = [] |
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51 | 51 | if self.after: |
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52 | 52 | util.rename(self.journal, self.after) |
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53 | 53 | else: |
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54 | 54 | os.unlink(self.journal) |
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55 | self.journal = None | |
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55 | 56 | |
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56 | 57 | def abort(self): |
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57 | 58 | if not self.entries: return |
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58 | 59 | |
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59 | 60 | print "transaction abort!" |
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60 | 61 | |
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61 | 62 | for f, o in self.entries: |
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62 | 63 | try: |
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63 | 64 | self.opener(f, "a").truncate(o) |
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64 | 65 | except: |
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65 | 66 | print "failed to truncate", f |
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66 | 67 | |
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67 | 68 | self.entries = [] |
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68 | 69 | |
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69 | 70 | print "rollback completed" |
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70 | 71 | |
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71 | 72 | def rollback(opener, file): |
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72 | 73 | for l in open(file).readlines(): |
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73 | 74 | f, o = l.split('\0') |
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74 | 75 | opener(f, "a").truncate(int(o)) |
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75 | 76 | os.unlink(file) |
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76 | 77 | |
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