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93 lines
3.0 KiB
93 lines
3.0 KiB
6 years ago
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# -*- coding: utf-8 -*-
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"""
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pygments.regexopt
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~~~~~~~~~~~~~~~~~
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An algorithm that generates optimized regexes for matching long lists of
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literal strings.
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:copyright: Copyright 2006-2017 by the Pygments team, see AUTHORS.
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:license: BSD, see LICENSE for details.
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"""
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import re
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from re import escape
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from os.path import commonprefix
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from itertools import groupby
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from operator import itemgetter
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CS_ESCAPE = re.compile(r'[\^\\\-\]]')
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FIRST_ELEMENT = itemgetter(0)
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def make_charset(letters):
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return '[' + CS_ESCAPE.sub(lambda m: '\\' + m.group(), ''.join(letters)) + ']'
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def regex_opt_inner(strings, open_paren):
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"""Return a regex that matches any string in the sorted list of strings."""
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close_paren = open_paren and ')' or ''
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# print strings, repr(open_paren)
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if not strings:
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# print '-> nothing left'
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return ''
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first = strings[0]
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if len(strings) == 1:
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# print '-> only 1 string'
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return open_paren + escape(first) + close_paren
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if not first:
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# print '-> first string empty'
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return open_paren + regex_opt_inner(strings[1:], '(?:') \
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+ '?' + close_paren
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if len(first) == 1:
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# multiple one-char strings? make a charset
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oneletter = []
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rest = []
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for s in strings:
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if len(s) == 1:
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oneletter.append(s)
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else:
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rest.append(s)
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if len(oneletter) > 1: # do we have more than one oneletter string?
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if rest:
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# print '-> 1-character + rest'
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return open_paren + regex_opt_inner(rest, '') + '|' \
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+ make_charset(oneletter) + close_paren
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# print '-> only 1-character'
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return open_paren + make_charset(oneletter) + close_paren
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prefix = commonprefix(strings)
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if prefix:
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plen = len(prefix)
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# we have a prefix for all strings
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# print '-> prefix:', prefix
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return open_paren + escape(prefix) \
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+ regex_opt_inner([s[plen:] for s in strings], '(?:') \
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+ close_paren
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# is there a suffix?
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strings_rev = [s[::-1] for s in strings]
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suffix = commonprefix(strings_rev)
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if suffix:
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slen = len(suffix)
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# print '-> suffix:', suffix[::-1]
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return open_paren \
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+ regex_opt_inner(sorted(s[:-slen] for s in strings), '(?:') \
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+ escape(suffix[::-1]) + close_paren
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# recurse on common 1-string prefixes
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# print '-> last resort'
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return open_paren + \
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'|'.join(regex_opt_inner(list(group[1]), '')
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for group in groupby(strings, lambda s: s[0] == first[0])) \
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+ close_paren
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def regex_opt(strings, prefix='', suffix=''):
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"""Return a compiled regex that matches any string in the given list.
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The strings to match must be literal strings, not regexes. They will be
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regex-escaped.
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*prefix* and *suffix* are pre- and appended to the final regex.
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"""
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strings = sorted(strings)
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return prefix + regex_opt_inner(strings, '(') + suffix
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