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"""
pygments.regexopt
~~~~~~~~~~~~~~~~~
An algorithm that generates optimized regexes for matching long lists of
literal strings.
:copyright: Copyright 2006-2021 by the Pygments team, see AUTHORS.
:license: BSD, see LICENSE for details.
"""
import re
from re import escape
from os.path import commonprefix
from itertools import groupby
from operator import itemgetter
CS_ESCAPE = re.compile(r'[\[\^\\\-\]]')
FIRST_ELEMENT = itemgetter(0)
def make_charset(letters):
return '[' + CS_ESCAPE.sub(lambda m: '\\' + m.group(), ''.join(letters)) + ']'
def regex_opt_inner(strings, open_paren):
"""Return a regex that matches any string in the sorted list of strings."""
close_paren = open_paren and ')' or ''
# print strings, repr(open_paren)
if not strings:
# print '-> nothing left'
return ''
first = strings[0]
if len(strings) == 1:
# print '-> only 1 string'
return open_paren + escape(first) + close_paren
if not first:
# print '-> first string empty'
return open_paren + regex_opt_inner(strings[1:], '(?:') \
+ '?' + close_paren
if len(first) == 1:
# multiple one-char strings? make a charset
oneletter = []
rest = []
for s in strings:
if len(s) == 1:
oneletter.append(s)
else:
rest.append(s)
if len(oneletter) > 1: # do we have more than one oneletter string?
if rest:
# print '-> 1-character + rest'
return open_paren + regex_opt_inner(rest, '') + '|' \
+ make_charset(oneletter) + close_paren
# print '-> only 1-character'
return open_paren + make_charset(oneletter) + close_paren
prefix = commonprefix(strings)
if prefix:
plen = len(prefix)
# we have a prefix for all strings
# print '-> prefix:', prefix
return open_paren + escape(prefix) \
+ regex_opt_inner([s[plen:] for s in strings], '(?:') \
+ close_paren
# is there a suffix?
strings_rev = [s[::-1] for s in strings]
suffix = commonprefix(strings_rev)
if suffix:
slen = len(suffix)
# print '-> suffix:', suffix[::-1]
return open_paren \
+ regex_opt_inner(sorted(s[:-slen] for s in strings), '(?:') \
+ escape(suffix[::-1]) + close_paren
# recurse on common 1-string prefixes
# print '-> last resort'
return open_paren + \
'|'.join(regex_opt_inner(list(group[1]), '')
for group in groupby(strings, lambda s: s[0] == first[0])) \
+ close_paren
def regex_opt(strings, prefix='', suffix=''):
"""Return a compiled regex that matches any string in the given list.
The strings to match must be literal strings, not regexes. They will be
regex-escaped.
*prefix* and *suffix* are pre- and appended to the final regex.
"""
strings = sorted(strings)
return prefix + regex_opt_inner(strings, '(') + suffix
|
