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497 lines
12 KiB
Python
497 lines
12 KiB
Python
#
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# Secret Labs' Regular Expression Engine
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# $Id$
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#
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# convert re-style regular expression to SRE template. the current
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# implementation is somewhat incomplete, and not very fast. should
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# definitely be rewritten before Python 1.6 goes beta.
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#
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# Copyright (c) 1998-2000 by Secret Labs AB. All rights reserved.
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#
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# This code can only be used for 1.6 alpha testing. All other use
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# require explicit permission from Secret Labs AB.
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#
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# Portions of this engine have been developed in cooperation with
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# CNRI. Hewlett-Packard provided funding for 1.6 integration and
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# other compatibility work.
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#
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# FIXME: comments marked with the FIXME tag are open issues. all such
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# issues should be closed before the final beta.
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import string, sys
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from sre_constants import *
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SPECIAL_CHARS = ".\\[{()*+?^$|"
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REPEAT_CHARS = "*+?{"
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# FIXME: string in tuple tests may explode with if char is unicode :-(
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DIGITS = tuple(string.digits)
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OCTDIGITS = tuple("01234567")
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HEXDIGITS = tuple("0123456789abcdefABCDEF")
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ESCAPES = {
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"\\a": (LITERAL, chr(7)),
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"\\b": (LITERAL, chr(8)),
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"\\f": (LITERAL, chr(12)),
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"\\n": (LITERAL, chr(10)),
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"\\r": (LITERAL, chr(13)),
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"\\t": (LITERAL, chr(9)),
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"\\v": (LITERAL, chr(11))
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}
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CATEGORIES = {
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"\\A": (AT, AT_BEGINNING), # start of string
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"\\b": (AT, AT_BOUNDARY),
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"\\B": (AT, AT_NON_BOUNDARY),
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"\\d": (IN, [(CATEGORY, CATEGORY_DIGIT)]),
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"\\D": (IN, [(CATEGORY, CATEGORY_NOT_DIGIT)]),
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"\\s": (IN, [(CATEGORY, CATEGORY_SPACE)]),
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"\\S": (IN, [(CATEGORY, CATEGORY_NOT_SPACE)]),
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"\\w": (IN, [(CATEGORY, CATEGORY_WORD)]),
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"\\W": (IN, [(CATEGORY, CATEGORY_NOT_WORD)]),
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"\\Z": (AT, AT_END), # end of string
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}
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class Pattern:
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# FIXME: <fl> rename class, and store flags in here too!
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def __init__(self):
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self.flags = []
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self.groups = 1
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self.groupdict = {}
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def getgroup(self, name=None):
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gid = self.groups
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self.groups = gid + 1
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if name:
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self.groupdict[name] = gid
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return gid
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def setflag(self, flag):
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if flag in self.flags:
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self.flags.append(flag)
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class SubPattern:
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# a subpattern, in intermediate form
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def __init__(self, pattern, data=None):
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self.pattern = pattern
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if not data:
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data = []
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self.data = data
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self.flags = []
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self.width = None
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def __repr__(self):
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return repr(self.data)
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def __len__(self):
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return len(self.data)
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def __delitem__(self, index):
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del self.data[index]
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def __getitem__(self, index):
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return self.data[index]
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def __setitem__(self, index, code):
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self.data[index] = code
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def __getslice__(self, start, stop):
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return SubPattern(self.pattern, self.data[start:stop])
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def insert(self, index, code):
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self.data.insert(index, code)
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def append(self, code):
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self.data.append(code)
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def getwidth(self):
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# determine the width (min, max) for this subpattern
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if self.width:
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return self.width
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lo = hi = 0L
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for op, av in self.data:
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if op is BRANCH:
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l = sys.maxint
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h = 0
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for av in av[1]:
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i, j = av.getwidth()
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l = min(l, i)
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h = min(h, j)
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lo = lo + i
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hi = hi + j
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elif op is CALL:
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i, j = av.getwidth()
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lo = lo + i
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hi = hi + j
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elif op is SUBPATTERN:
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i, j = av[1].getwidth()
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lo = lo + i
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hi = hi + j
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elif op in (MIN_REPEAT, MAX_REPEAT):
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i, j = av[2].getwidth()
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lo = lo + i * av[0]
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hi = hi + j * av[1]
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elif op in (ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY):
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lo = lo + 1
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hi = hi + 1
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elif op == SUCCESS:
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break
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self.width = int(min(lo, sys.maxint)), int(min(hi, sys.maxint))
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return self.width
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def set(self, flag):
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if not flag in self.flags:
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self.flags.append(flag)
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def reset(self, flag):
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if flag in self.flags:
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self.flags.remove(flag)
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class Tokenizer:
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def __init__(self, string):
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self.string = list(string)
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self.next = self.__next()
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def __next(self):
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if not self.string:
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return None
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char = self.string[0]
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if char[0] == "\\":
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try:
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c = self.string[1]
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except IndexError:
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raise SyntaxError, "bogus escape"
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char = char + c
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try:
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if c == "x":
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# hexadecimal constant
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for i in xrange(2, sys.maxint):
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c = self.string[i]
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if str(c) not in HEXDIGITS:
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break
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char = char + c
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elif str(c) in DIGITS:
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# decimal (or octal) number
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for i in xrange(2, sys.maxint):
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c = self.string[i]
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# FIXME: if larger than current number of
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# groups, interpret as an octal number
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if str(c) not in DIGITS:
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break
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char = char + c
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except IndexError:
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pass # use what we've got this far
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del self.string[0:len(char)]
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return char
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def match(self, char):
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if char == self.next:
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self.next = self.__next()
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return 1
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return 0
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def match_set(self, set):
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if self.next and self.next in set:
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self.next = self.__next()
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return 1
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return 0
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def get(self):
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this = self.next
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self.next = self.__next()
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return this
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def _fixescape(escape, character_class=0):
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# convert escape to (type, value)
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if character_class:
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# inside a character class, we'll look in the character
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# escapes dictionary first
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code = ESCAPES.get(escape)
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if code:
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return code
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code = CATEGORIES.get(escape)
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else:
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code = CATEGORIES.get(escape)
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if code:
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return code
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code = ESCAPES.get(escape)
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if code:
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return code
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if not character_class:
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try:
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group = int(escape[1:])
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# FIXME: only valid if group <= current number of groups
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return GROUP, group
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except ValueError:
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pass
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try:
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if escape[1:2] == "x":
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escape = escape[2:]
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return LITERAL, chr(int(escape[-2:], 16) & 0xff)
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elif str(escape[1:2]) in DIGITS:
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return LITERAL, chr(int(escape[1:], 8) & 0xff)
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elif len(escape) == 2:
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return LITERAL, escape[1]
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except ValueError:
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pass
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raise SyntaxError, "bogus escape: %s" % repr(escape)
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def _branch(subpattern, items):
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# form a branch operator from a set of items (FIXME: move this
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# optimization to the compiler module!)
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# check if all items share a common prefix
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while 1:
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prefix = None
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for item in items:
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if not item:
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break
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if prefix is None:
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prefix = item[0]
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elif item[0] != prefix:
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break
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else:
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# all subitems start with a common "prefix".
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# move it out of the branch
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for item in items:
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del item[0]
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subpattern.append(prefix)
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continue # check next one
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break
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# check if the branch can be replaced by a character set
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for item in items:
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if len(item) != 1 or item[0][0] != LITERAL:
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break
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else:
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# we can store this as a character set instead of a
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# branch (FIXME: use a range if possible)
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set = []
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for item in items:
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set.append(item[0])
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subpattern.append((IN, set))
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return
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subpattern.append((BRANCH, (None, items)))
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def _parse(source, pattern, flags=()):
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# parse regular expression pattern into an operator list.
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subpattern = SubPattern(pattern)
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this = None
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while 1:
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if str(source.next) in ("|", ")"):
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break # end of subpattern
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this = source.get()
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if this is None:
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break # end of pattern
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if this and this[0] not in SPECIAL_CHARS:
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subpattern.append((LITERAL, this))
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elif this == "[":
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# character set
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set = []
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## if source.match(":"):
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## pass # handle character classes
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if source.match("^"):
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set.append((NEGATE, None))
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# check remaining characters
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start = set[:]
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while 1:
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this = source.get()
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if this == "]" and set != start:
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break
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elif this and this[0] == "\\":
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code1 = _fixescape(this, 1)
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elif this:
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code1 = LITERAL, this
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else:
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raise SyntaxError, "unexpected end of regular expression"
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if source.match("-"):
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# potential range
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this = source.get()
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if this == "]":
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set.append(code1)
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set.append((LITERAL, "-"))
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break
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else:
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if this[0] == "\\":
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code2 = _fixescape(this, 1)
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else:
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code2 = LITERAL, this
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if code1[0] != LITERAL or code2[0] != LITERAL:
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raise SyntaxError, "illegal range"
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if len(code1[1]) != 1 or len(code2[1]) != 1:
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raise SyntaxError, "illegal range"
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set.append((RANGE, (code1[1], code2[1])))
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else:
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if code1[0] is IN:
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code1 = code1[1][0]
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set.append(code1)
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# FIXME: <fl> move set optimization to support function
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if len(set)==1 and set[0][0] is LITERAL:
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subpattern.append(set[0]) # optimization
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elif len(set)==2 and set[0][0] is NEGATE and set[1][0] is LITERAL:
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subpattern.append((NOT_LITERAL, set[1][1])) # optimization
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else:
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# FIXME: <fl> add charmap optimization
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subpattern.append((IN, set))
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elif this and this[0] in REPEAT_CHARS:
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# repeat previous item
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if this == "?":
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min, max = 0, 1
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elif this == "*":
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min, max = 0, sys.maxint
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elif this == "+":
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min, max = 1, sys.maxint
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elif this == "{":
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min, max = 0, sys.maxint
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lo = hi = ""
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while str(source.next) in DIGITS:
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lo = lo + source.get()
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if source.match(","):
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while str(source.next) in DIGITS:
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hi = hi + source.get()
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else:
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hi = lo
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if not source.match("}"):
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raise SyntaxError, "bogus range"
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if lo:
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min = int(lo)
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if hi:
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max = int(hi)
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# FIXME: <fl> check that hi >= lo!
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else:
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raise SyntaxError, "not supported"
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# figure out which item to repeat
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# FIXME: should back up to the right mark, right?
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if subpattern:
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index = len(subpattern)-1
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while subpattern[index][0] is MARK:
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index = index - 1
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item = subpattern[index:index+1]
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else:
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raise SyntaxError, "nothing to repeat"
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if source.match("?"):
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subpattern[index] = (MIN_REPEAT, (min, max, item))
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else:
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subpattern[index] = (MAX_REPEAT, (min, max, item))
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elif this == ".":
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subpattern.append((ANY, None))
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elif this == "(":
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group = 1
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name = None
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if source.match("?"):
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group = 0
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# options
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if source.match("P"):
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# named group: skip forward to end of name
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if source.match("<"):
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name = ""
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while 1:
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char = source.get()
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if char is None or char == ">":
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break
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name = name + char
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group = 1
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elif source.match(":"):
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# non-capturing group
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group = 2
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elif source.match_set("iI"):
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pattern.setflag("i")
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elif source.match_set("lL"):
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pattern.setflag("l")
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elif source.match_set("mM"):
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pattern.setflag("m")
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elif source.match_set("sS"):
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pattern.setflag("s")
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elif source.match_set("xX"):
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pattern.setflag("x")
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if group:
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# parse group contents
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b = []
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if group == 2:
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# anonymous group
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group = None
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else:
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group = pattern.getgroup(name)
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if group:
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subpattern.append((MARK, (group-1)*2))
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while 1:
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p = _parse(source, pattern, flags)
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if source.match(")"):
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if b:
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b.append(p)
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_branch(subpattern, b)
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else:
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subpattern.append((SUBPATTERN, (group, p)))
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break
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elif source.match("|"):
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b.append(p)
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else:
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raise SyntaxError, "group not properly closed"
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if group:
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subpattern.append((MARK, (group-1)*2+1))
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else:
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# FIXME: should this really be a while loop?
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while 1:
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char = source.get()
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if char is None or char == ")":
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break
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elif this == "^":
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subpattern.append((AT, AT_BEGINNING))
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elif this == "$":
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subpattern.append((AT, AT_END))
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elif this and this[0] == "\\":
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code =_fixescape(this)
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subpattern.append(code)
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else:
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raise SyntaxError, "parser error"
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return subpattern
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def parse(source, flags=()):
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s = Tokenizer(source)
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g = Pattern()
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b = []
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while 1:
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p = _parse(s, g, flags)
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tail = s.get()
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if tail == "|":
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b.append(p)
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elif tail == ")":
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raise SyntaxError, "unbalanced parenthesis"
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elif tail is None:
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if b:
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b.append(p)
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p = SubPattern(g)
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_branch(p, b)
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break
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else:
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raise SyntaxError, "bogus characters at end of regular expression"
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return p
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if __name__ == "__main__":
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from pprint import pprint
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from testpatterns import PATTERNS
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a = b = c = 0
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for pattern, flags in PATTERNS:
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if flags:
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continue
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print "-"*68
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try:
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p = parse(pattern)
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print repr(pattern), "->"
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pprint(p.data)
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import sre_compile
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try:
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code = sre_compile.compile(p)
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c = c + 1
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except:
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pass
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a = a + 1
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except SyntaxError, v:
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print "**", repr(pattern), v
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b = b + 1
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print "-"*68
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print a, "of", b, "patterns successfully parsed"
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print c, "of", b, "patterns successfully compiled"
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