"""Determines the extent of differences between two strings.

Returns a pair containing the offset at which the changes start,

and the negative offset at which the changes end.

If the two strings have neither a common prefix nor a common

suffix, ``(0, 0)`` is returned.

"""

start = 0

limit = min(len(str1), len(str2))

while start < limit and str1[start] == str2[start]:

start += 1

end = -1

limit = limit - start

while -end <= limit and str1[end] == str2[end]:

end -= 1

ignore_blank_lines=False, ignore_case=False,

ignore_space_changes=False):

"""Retrieve differences in the form of `difflib.SequenceMatcher`

opcodes, grouped according to the ``context`` and ``ignore_*``

parameters.

:param fromlines: list of lines corresponding to the old content

:param tolines: list of lines corresponding to the new content

:param ignore_blank_lines: differences about empty lines only are ignored

:param ignore_case: upper case / lower case only differences are ignored

:param ignore_space_changes: differences in amount of spaces are ignored

:param context: the number of "equal" lines kept for representing

the context of the change

:return: generator of grouped `difflib.SequenceMatcher` opcodes

If none of the ``ignore_*`` parameters is `True`, there's nothing

to filter out the results will come straight from the

SequenceMatcher.

"""

if ignore_space_changes:

fromlines = map(_norm_space_changes, fromlines)

tolines = map(_norm_space_changes, tolines)

if ignore_case:

fromlines = [l.lower() for l in fromlines]

tolines = [l.lower() for l in tolines]

hunks = get_hunks(fromlines, tolines, context)

if ignore_blank_lines:

hunks = filter_ignorable_lines(hunks, fromlines, tolines, context,

ignore_blank_lines, False, False)

"""Generator yielding grouped opcodes describing differences .

See `get_filtered_hunks` for the parameter descriptions.

"""

matcher = difflib.SequenceMatcher(None, fromlines, tolines)

if context is None:

return (hunk for hunk in [matcher.get_opcodes()])

else:

ignore_blank_lines, ignore_case,

ignore_space_changes):

"""Detect line changes that should be ignored and emits them as

tagged as "equal", possibly joined with the preceding and/or

following "equal" block.

See `get_filtered_hunks` for the parameter descriptions.

"""

def is_ignorable(tag, fromlines, tolines):

if ignore_blank_lines:

if tag == 'delete':

return not any(fromlines)

if tag == 'insert':

return not any(tolines)

if (ignore_case or ignore_space_changes) and tag == 'replace':

if len(fromlines) != len(tolines):

return False

def f(str):

if ignore_case:

str = str.lower()

if ignore_space_changes:

str = _norm_space_changes(str)

return str

for i in range(len(fromlines)):

if f(fromlines[i]) != f(tolines[i]):

return False

return True

hunks = list(hunks)

opcodes = []

ignored_lines = False

prev = None

for hunk in hunks:

for tag, i1, i2, j1, j2 in hunk:

if tag == 'equal':

if prev:

prev = (tag, prev[1], i2, prev[3], j2)

else:

prev = (tag, i1, i2, j1, j2)

else:

if is_ignorable(tag, fromlines[i1:i2], tolines[j1:j2]):

ignored_lines = True

if prev:

prev = 'equal', prev[1], i2, prev[3], j2

else:

prev = 'equal', i1, i2, j1, j2

continue

if prev:

opcodes.append(prev)

opcodes.append((tag, i1, i2, j1, j2))

prev = None

if prev:

opcodes.append(prev)

if ignored_lines:

if context is None:

yield opcodes

else:

# we leave at most n lines with the tag 'equal' before and after

# every change

n = context

nn = n + n

group = []

def all_equal():

all(op[0] == 'equal' for op in group)

for idx, (tag, i1, i2, j1, j2) in enumerate(opcodes):

if idx == 0 and tag == 'equal': # Fixup leading unchanged block

i1, j1 = max(i1, i2 - n), max(j1, j2 - n)

elif tag == 'equal' and i2 - i1 > nn:

group.append((tag, i1, min(i2, i1 + n), j1,

min(j2, j1 + n)))

if not all_equal():

yield group

group = []

i1, j1 = max(i1, i2 - n), max(j1, j2 - n)

group.append((tag, i1, i2, j1, j2))

if group and not (len(group) == 1 and group[0][0] == 'equal'):

if group[-1][0] == 'equal': # Fixup trailing unchanged block

tag, i1, i2, j1, j2 = group[-1]

group[-1] = tag, i1, min(i2, i1 + n), j1, min(j2, j1 + n)

if not all_equal():

yield group

else:

for hunk in hunks:

ignore_blank_lines=0, ignore_case=0, ignore_space_changes=0):

"""Return an array that is adequate for adding to the data dictionary

See `get_filtered_hunks` for the parameter descriptions.

See also the diff_div.html template.

"""

type_map = {'replace': 'mod', 'delete': 'rem', 'insert': 'add',

'equal': 'unmod'}

space_re = re.compile(' ( +)|^ ')

def htmlify(match):

div, mod = divmod(len(match.group(0)), 2)

return div * '&nbsp; ' + mod * '&nbsp;'

def markup_intraline_changes(opcodes):

for tag, i1, i2, j1, j2 in opcodes:

if tag == 'replace' and i2 - i1 == j2 - j1:

for i in range(i2 - i1):

fromline, toline = fromlines[i1 + i], tolines[j1 + i]

(start, end) = get_change_extent(fromline, toline)

if start != 0 or end != 0:

last = end + len(fromline)

fromlines[i1 + i] = (

fromline[:start] + '\0' + fromline[start:last] +

'\1' + fromline[last:])

last = end+len(toline)

tolines[j1 + i] = (

toline[:start] + '\0' + toline[start:last] +

'\1' + toline[last:])

yield tag, i1, i2, j1, j2

changes = []

for group in get_filtered_hunks(fromlines, tolines, context,

ignore_blank_lines, ignore_case,

ignore_space_changes):

blocks = []

last_tag = None

for tag, i1, i2, j1, j2 in markup_intraline_changes(group):

if tag != last_tag:

blocks.append({'type': type_map[tag],

'base': {'offset': i1, 'lines': []},

'changed': {'offset': j1, 'lines': []}})

if tag == 'equal':

for line in fromlines[i1:i2]:

line = line.expandtabs(tabwidth)

line = space_re.sub(htmlify, escape(line, quotes=False))

blocks[-1]['base']['lines'].append(Markup(unicode(line)))

for line in tolines[j1:j2]:

line = line.expandtabs(tabwidth)

line = space_re.sub(htmlify, escape(line, quotes=False))

blocks[-1]['changed']['lines'].append(Markup(unicode(line)))

else:

if tag in ('replace', 'delete'):

for line in fromlines[i1:i2]:

line = expandtabs(line, tabwidth, '\0\1')

line = escape(line, quotes=False)

line = '<del>'.join([space_re.sub(htmlify, seg)

for seg in line.split('\0')])

line = line.replace('\1', '</del>')

blocks[-1]['base']['lines'].append(

Markup(unicode(line)))

if tag in ('replace', 'insert'):

for line in tolines[j1:j2]:

line = expandtabs(line, tabwidth, '\0\1')

line = escape(line, quotes=False)

line = '<ins>'.join([space_re.sub(htmlify, seg)

for seg in line.split('\0')])

line = line.replace('\1', '</ins>')

blocks[-1]['changed']['lines'].append(

Markup(unicode(line)))

changes.append(blocks)

ignore_case=0, ignore_space_changes=0):

"""Generator producing lines corresponding to a textual diff.

See `get_filtered_hunks` for the parameter descriptions.

"""

for group in get_filtered_hunks(fromlines, tolines, context,

ignore_blank_lines, ignore_case,

ignore_space_changes):

i1, i2, j1, j2 = group[0][1], group[-1][2], group[0][3], group[-1][4]

if i1 == 0 and i2 == 0:

i1, i2 = -1, -1 # support for 'A'dd changes

yield '@@ -%d,%d +%d,%d @@' % (i1 + 1, i2 - i1, j1 + 1, j2 - j1)

for tag, i1, i2, j1, j2 in group:

if tag == 'equal':

for line in fromlines[i1:i2]:

yield ' ' + line

else:

if tag in ('replace', 'delete'):

for line in fromlines[i1:i2]:

yield '-' + line

if tag in ('replace', 'insert'):

for line in tolines[j1:j2]:

"""Retrieve user preferences for diffs.

:return: ``(style, options, data)`` triple.

``style``

can be ``'inline'`` or ``'sidebyside'``,

``options``

a sequence of "diff" flags,

``data``

the style and options information represented as

key/value pairs in dictionaries, for example::

{'style': u'sidebyside',

'options': {'contextall': 1, 'contextlines': 2,

'ignorecase': 0, 'ignoreblanklines': 0,

'ignorewhitespace': 1}}

"""

options_data = {}

data = {'options': options_data}

def get_bool_option(name, default=0):

pref = int(req.session.get('diff_' + name, default))

arg = int(name in req.args)

if 'update' in req.args and arg != pref:

req.session.set('diff_' + name, arg, default)

else:

arg = pref

return arg

pref = req.session.get('diff_style', 'inline')

style = req.args.get('style', pref)

if 'update' in req.args and style != pref:

req.session.set('diff_style', style, 'inline')

data['style'] = style

pref = int(req.session.get('diff_contextlines', 2))

try:

context = int(req.args.get('contextlines', pref))

except ValueError:

context = -1

if 'update' in req.args and context != pref:

req.session.set('diff_contextlines', context, 2)

options_data['contextlines'] = context

arg = int(req.args.get('contextall', 0))

options_data['contextall'] = arg

options = ['-U%d' % (-1 if arg else context)]

arg = get_bool_option('ignoreblanklines')

if arg:

options.append('-B')

options_data['ignoreblanklines'] = arg

arg = get_bool_option('ignorecase')

if arg:

options.append('-i')

options_data['ignorecase'] = arg

arg = get_bool_option('ignorewhitespace')

if arg:

options.append('-b')

options_data['ignorewhitespace'] = arg