cvs2svn_lib/rcs_stream.py

   1 # (Be in -*- python -*- mode.)
   2 #
   3 # ====================================================================
   4 # Copyright (c) 2007 CollabNet.  All rights reserved.
   5 #
   6 # This software is licensed as described in the file COPYING, which
   7 # you should have received as part of this distribution.  The terms
   8 # are also available at http://subversion.tigris.org/license-1.html.
   9 # If newer versions of this license are posted there, you may use a
  10 # newer version instead, at your option.
  11 #
  12 # This software consists of voluntary contributions made by many
  13 # individuals.  For exact contribution history, see the revision
  14 # history and logs, available at http://cvs2svn.tigris.org/.
  15 # ====================================================================
  16
  17 """This module processes RCS diffs (deltas)."""
  18
  19
  20 import re
  21
  22 def msplit(s):
  23   """Split S into an array of lines.
  24
  25   Only \n is a line separator. The line endings are part of the lines."""
  26
  27   # return s.splitlines(True) clobbers \r
  28   re = [ i + "\n" for i in s.split("\n") ]
  29   re[-1] = re[-1][:-1]
  30   if not re[-1]:
  31     del re[-1]
  32   return re
  33
  34
  35 class MalformedDeltaException(Exception):
  36   """A malformed RCS delta was encountered."""
  37
  38   pass
  39
  40 class RCSStream:
  41   """This class represents a single file object to which RCS deltas can be
  42   applied in various ways."""
  43
  44   ad_command = re.compile(r'^([ad])(\d+)\s(\d+)\n$')
  45   a_command = re.compile(r'^a(\d+)\s(\d+)\n$')
  46
  47   def __init__(self, text):
  48     """Instantiate and initialize the file content with TEXT."""
  49
  50     self._texts = msplit(text)
  51
  52   def get_text(self):
  53     """Return the current file content."""
  54
  55     return "".join(self._texts)
  56
  57   def apply_diff(self, diff):
  58     """Apply the RCS diff DIFF to the current file content."""
  59
  60     ntexts = []
  61     ooff = 0
  62     diffs = msplit(diff)
  63     i = 0
  64     while i < len(diffs):
  65       admatch = self.ad_command.match(diffs[i])
  66       if not admatch:
  67         raise MalformedDeltaException('Bad ed command')
  68       i += 1
  69       sl = int(admatch.group(2))
  70       cn = int(admatch.group(3))
  71       if admatch.group(1) == 'd': # "d" - Delete command
  72         sl -= 1
  73         if sl < ooff:
  74           raise MalformedDeltaException('Deletion before last edit')
  75         if sl > len(self._texts):
  76           raise MalformedDeltaException('Deletion past file end')
  77         if sl + cn > len(self._texts):
  78           raise MalformedDeltaException('Deletion beyond file end')
  79         ntexts += self._texts[ooff:sl]
  80         ooff = sl + cn
  81       else: # "a" - Add command
  82         if sl < ooff: # Also catches same place
  83           raise MalformedDeltaException('Insertion before last edit')
  84         if sl > len(self._texts):
  85           raise MalformedDeltaException('Insertion past file end')
  86         ntexts += self._texts[ooff:sl] + diffs[i:i + cn]
  87         ooff = sl
  88         i += cn
  89     self._texts = ntexts + self._texts[ooff:]
  90
  91   def invert_diff(self, diff):
  92     """Apply the RCS diff DIFF to the current file content and simultaneously
  93     generate an RCS diff suitable for reverting the change."""
  94
  95     ntexts = []
  96     ooff = 0
  97     diffs = msplit(diff)
  98     ndiffs = []
  99     adjust = 0
 100     i = 0
 101     while i < len(diffs):
 102       admatch = self.ad_command.match(diffs[i])
 103       if not admatch:
 104         raise MalformedDeltaException('Bad ed command')
 105       i += 1
 106       sl = int(admatch.group(2))
 107       cn = int(admatch.group(3))
 108       if admatch.group(1) == 'd': # "d" - Delete command
 109         sl -= 1
 110         if sl < ooff:
 111           raise MalformedDeltaException('Deletion before last edit')
 112         if sl > len(self._texts):
 113           raise MalformedDeltaException('Deletion past file end')
 114         if sl + cn > len(self._texts):
 115           raise MalformedDeltaException('Deletion beyond file end')
 116         # Handle substitution explicitly, as add must come after del
 117         # (last add may end in no newline, so no command can follow).
 118         if i < len(diffs):
 119           amatch = self.a_command.match(diffs[i])
 120         else:
 121           amatch = None
 122         if amatch and int(amatch.group(1)) == sl + cn:
 123           cn2 = int(amatch.group(2))
 124           i += 1
 125           ndiffs += ["d%d %d\na%d %d\n" % \
 126                         (sl + 1 + adjust, cn2, sl + adjust + cn2, cn)] + \
 127                     self._texts[sl:sl + cn]
 128           ntexts += self._texts[ooff:sl] + diffs[i:i + cn2]
 129           adjust += cn2 - cn
 130           i += cn2
 131         else:
 132           ndiffs += ["a%d %d\n" % (sl + adjust, cn)] + \
 133                     self._texts[sl:sl + cn]
 134           ntexts += self._texts[ooff:sl]
 135           adjust -= cn
 136         ooff = sl + cn
 137       else: # "a" - Add command
 138         if sl < ooff: # Also catches same place
 139           raise MalformedDeltaException('Insertion before last edit')
 140         if sl > len(self._texts):
 141           raise MalformedDeltaException('Insertion past file end')
 142         ndiffs += ["d%d %d\n" % (sl + 1 + adjust, cn)]
 143         ntexts += self._texts[ooff:sl] + diffs[i:i + cn]
 144         ooff = sl
 145         adjust += cn
 146         i += cn
 147     self._texts = ntexts + self._texts[ooff:]
 148     return "".join(ndiffs)
 149