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# (Be in -*- python -*- mode.)
#
# ====================================================================
# Copyright (c) 2007 CollabNet. All rights reserved.
#
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution. The terms
# are also available at http://subversion.tigris.org/license-1.html.
# If newer versions of this license are posted there, you may use a
# newer version instead, at your option.
#
# This software consists of voluntary contributions made by many
# individuals. For exact contribution history, see the revision
# history and logs, available at http://cvs2svn.tigris.org/.
# ====================================================================
"""This module processes RCS diffs (deltas)."""
import re
def msplit(s):
"""Split S into an array of lines.
Only \n is a line separator. The line endings are part of the lines."""
# return s.splitlines(True) clobbers \r
re = [ i + "\n" for i in s.split("\n") ]
re[-1] = re[-1][:-1]
if not re[-1]:
del re[-1]
return re
class MalformedDeltaException(Exception):
"""A malformed RCS delta was encountered."""
pass
class RCSStream:
"""This class represents a single file object to which RCS deltas can be
applied in various ways."""
ad_command = re.compile(r'^([ad])(\d+)\s(\d+)\n$')
a_command = re.compile(r'^a(\d+)\s(\d+)\n$')
def __init__(self, text):
"""Instantiate and initialize the file content with TEXT."""
self._texts = msplit(text)
def get_text(self):
"""Return the current file content."""
return "".join(self._texts)
def apply_diff(self, diff):
"""Apply the RCS diff DIFF to the current file content."""
ntexts = []
ooff = 0
diffs = msplit(diff)
i = 0
while i < len(diffs):
admatch = self.ad_command.match(diffs[i])
if not admatch:
raise MalformedDeltaException('Bad ed command')
i += 1
sl = int(admatch.group(2))
cn = int(admatch.group(3))
if admatch.group(1) == 'd': # "d" - Delete command
sl -= 1
if sl < ooff:
raise MalformedDeltaException('Deletion before last edit')
if sl > len(self._texts):
raise MalformedDeltaException('Deletion past file end')
if sl + cn > len(self._texts):
raise MalformedDeltaException('Deletion beyond file end')
ntexts += self._texts[ooff:sl]
ooff = sl + cn
else: # "a" - Add command
if sl < ooff: # Also catches same place
raise MalformedDeltaException('Insertion before last edit')
if sl > len(self._texts):
raise MalformedDeltaException('Insertion past file end')
ntexts += self._texts[ooff:sl] + diffs[i:i + cn]
ooff = sl
i += cn
self._texts = ntexts + self._texts[ooff:]
def invert_diff(self, diff):
"""Apply the RCS diff DIFF to the current file content and simultaneously
generate an RCS diff suitable for reverting the change."""
ntexts = []
ooff = 0
diffs = msplit(diff)
ndiffs = []
adjust = 0
i = 0
while i < len(diffs):
admatch = self.ad_command.match(diffs[i])
if not admatch:
raise MalformedDeltaException('Bad ed command')
i += 1
sl = int(admatch.group(2))
cn = int(admatch.group(3))
if admatch.group(1) == 'd': # "d" - Delete command
sl -= 1
if sl < ooff:
raise MalformedDeltaException('Deletion before last edit')
if sl > len(self._texts):
raise MalformedDeltaException('Deletion past file end')
if sl + cn > len(self._texts):
raise MalformedDeltaException('Deletion beyond file end')
# Handle substitution explicitly, as add must come after del
# (last add may end in no newline, so no command can follow).
if i < len(diffs):
amatch = self.a_command.match(diffs[i])
else:
amatch = None
if amatch and int(amatch.group(1)) == sl + cn:
cn2 = int(amatch.group(2))
i += 1
ndiffs += ["d%d %d\na%d %d\n" % \
(sl + 1 + adjust, cn2, sl + adjust + cn2, cn)] + \
self._texts[sl:sl + cn]
ntexts += self._texts[ooff:sl] + diffs[i:i + cn2]
adjust += cn2 - cn
i += cn2
else:
ndiffs += ["a%d %d\n" % (sl + adjust, cn)] + \
self._texts[sl:sl + cn]
ntexts += self._texts[ooff:sl]
adjust -= cn
ooff = sl + cn
else: # "a" - Add command
if sl < ooff: # Also catches same place
raise MalformedDeltaException('Insertion before last edit')
if sl > len(self._texts):
raise MalformedDeltaException('Insertion past file end')
ndiffs += ["d%d %d\n" % (sl + 1 + adjust, cn)]
ntexts += self._texts[ooff:sl] + diffs[i:i + cn]
ooff = sl
adjust += cn
i += cn
self._texts = ntexts + self._texts[ooff:]
return "".join(ndiffs)
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