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862 lines
29 KiB
Python
862 lines
29 KiB
Python
#
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# Secret Labs' Regular Expression Engine
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#
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# convert re-style regular expression to sre pattern
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#
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# Copyright (c) 1998-2001 by Secret Labs AB. All rights reserved.
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#
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# See the sre.py file for information on usage and redistribution.
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#
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"""Internal support module for sre"""
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# XXX: show string offset and offending character for all errors
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from sre_constants import *
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from _sre import MAXREPEAT
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SPECIAL_CHARS = ".\\[{()*+?^$|"
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REPEAT_CHARS = "*+?{"
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DIGITS = frozenset("0123456789")
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OCTDIGITS = frozenset("01234567")
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HEXDIGITS = frozenset("0123456789abcdefABCDEF")
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WHITESPACE = frozenset(" \t\n\r\v\f")
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_REPEATCODES = frozenset((MIN_REPEAT, MAX_REPEAT))
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_UNITCODES = frozenset((ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY))
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ESCAPES = {
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r"\a": (LITERAL, ord("\a")),
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r"\b": (LITERAL, ord("\b")),
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r"\f": (LITERAL, ord("\f")),
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r"\n": (LITERAL, ord("\n")),
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r"\r": (LITERAL, ord("\r")),
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r"\t": (LITERAL, ord("\t")),
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r"\v": (LITERAL, ord("\v")),
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r"\\": (LITERAL, ord("\\"))
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}
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CATEGORIES = {
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r"\A": (AT, AT_BEGINNING_STRING), # start of string
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r"\b": (AT, AT_BOUNDARY),
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r"\B": (AT, AT_NON_BOUNDARY),
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r"\d": (IN, [(CATEGORY, CATEGORY_DIGIT)]),
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r"\D": (IN, [(CATEGORY, CATEGORY_NOT_DIGIT)]),
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r"\s": (IN, [(CATEGORY, CATEGORY_SPACE)]),
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r"\S": (IN, [(CATEGORY, CATEGORY_NOT_SPACE)]),
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r"\w": (IN, [(CATEGORY, CATEGORY_WORD)]),
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r"\W": (IN, [(CATEGORY, CATEGORY_NOT_WORD)]),
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r"\Z": (AT, AT_END_STRING), # end of string
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}
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FLAGS = {
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# standard flags
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"i": SRE_FLAG_IGNORECASE,
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"L": SRE_FLAG_LOCALE,
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"m": SRE_FLAG_MULTILINE,
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"s": SRE_FLAG_DOTALL,
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"x": SRE_FLAG_VERBOSE,
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# extensions
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"a": SRE_FLAG_ASCII,
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"t": SRE_FLAG_TEMPLATE,
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"u": SRE_FLAG_UNICODE,
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}
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class Pattern:
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# master pattern object. keeps track of global attributes
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def __init__(self):
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self.flags = 0
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self.open = []
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self.groups = 1
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self.groupdict = {}
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def opengroup(self, name=None):
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gid = self.groups
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self.groups = gid + 1
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if self.groups > MAXGROUPS:
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raise error("groups number is too large")
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if name is not None:
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ogid = self.groupdict.get(name, None)
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if ogid is not None:
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raise error("redefinition of group name %s as group %d; "
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"was group %d" % (repr(name), gid, ogid))
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self.groupdict[name] = gid
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self.open.append(gid)
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return gid
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def closegroup(self, gid):
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self.open.remove(gid)
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def checkgroup(self, gid):
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return gid < self.groups and gid not in self.open
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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 data is None:
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data = []
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self.data = data
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self.width = None
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def dump(self, level=0):
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nl = True
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seqtypes = (tuple, list)
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for op, av in self.data:
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print(level*" " + op, end='')
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if op == IN:
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# member sublanguage
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print()
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for op, a in av:
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print((level+1)*" " + op, a)
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elif op == BRANCH:
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print()
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for i, a in enumerate(av[1]):
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if i:
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print(level*" " + "or")
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a.dump(level+1)
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elif op == GROUPREF_EXISTS:
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condgroup, item_yes, item_no = av
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print('', condgroup)
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item_yes.dump(level+1)
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if item_no:
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print(level*" " + "else")
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item_no.dump(level+1)
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elif isinstance(av, seqtypes):
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nl = False
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for a in av:
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if isinstance(a, SubPattern):
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if not nl:
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print()
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a.dump(level+1)
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nl = True
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else:
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if not nl:
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print(' ', end='')
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print(a, end='')
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nl = False
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if not nl:
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print()
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else:
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print('', av)
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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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if isinstance(index, slice):
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return SubPattern(self.pattern, self.data[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 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 is not None:
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return self.width
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lo = hi = 0
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for op, av in self.data:
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if op is BRANCH:
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i = MAXREPEAT - 1
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j = 0
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for av in av[1]:
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l, h = av.getwidth()
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i = min(i, l)
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j = max(j, h)
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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 _REPEATCODES:
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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 _UNITCODES:
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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 = min(lo, MAXREPEAT - 1), min(hi, MAXREPEAT)
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return self.width
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class Tokenizer:
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def __init__(self, string):
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self.istext = isinstance(string, str)
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if not self.istext:
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string = str(string, 'latin1')
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self.string = string
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self.index = 0
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self.__next()
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def __next(self):
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index = self.index
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try:
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char = self.string[index]
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except IndexError:
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self.next = None
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return
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if char == "\\":
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index += 1
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try:
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char += self.string[index]
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except IndexError:
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raise error("bogus escape (end of line)")
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self.index = index + 1
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self.next = char
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def match(self, char):
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if char == self.next:
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self.__next()
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return True
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return False
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def get(self):
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this = self.next
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self.__next()
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return this
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def getwhile(self, n, charset):
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result = ''
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for _ in range(n):
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c = self.next
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if c not in charset:
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break
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result += c
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self.__next()
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return result
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def getuntil(self, terminator):
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result = ''
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while True:
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c = self.next
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self.__next()
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if c is None:
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raise error("unterminated name")
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if c == terminator:
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break
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result += c
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return result
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def tell(self):
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return self.index, self.next
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def seek(self, index):
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self.index, self.next = index
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# The following three functions are not used in this module anymore, but we keep
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# them here (with DeprecationWarnings) for backwards compatibility.
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def isident(char):
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import warnings
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warnings.warn('sre_parse.isident() will be removed in 3.5',
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DeprecationWarning, stacklevel=2)
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return "a" <= char <= "z" or "A" <= char <= "Z" or char == "_"
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def isdigit(char):
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import warnings
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warnings.warn('sre_parse.isdigit() will be removed in 3.5',
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DeprecationWarning, stacklevel=2)
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return "0" <= char <= "9"
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def isname(name):
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import warnings
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warnings.warn('sre_parse.isname() will be removed in 3.5',
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DeprecationWarning, stacklevel=2)
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# check that group name is a valid string
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if not isident(name[0]):
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return False
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for char in name[1:]:
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if not isident(char) and not isdigit(char):
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return False
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return True
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def _class_escape(source, escape):
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# handle escape code inside character class
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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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if code and code[0] is IN:
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return code
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try:
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c = escape[1:2]
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if c == "x":
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# hexadecimal escape (exactly two digits)
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escape += source.getwhile(2, HEXDIGITS)
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if len(escape) != 4:
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raise ValueError
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return LITERAL, int(escape[2:], 16)
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elif c == "u" and source.istext:
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# unicode escape (exactly four digits)
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escape += source.getwhile(4, HEXDIGITS)
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if len(escape) != 6:
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raise ValueError
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return LITERAL, int(escape[2:], 16)
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elif c == "U" and source.istext:
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# unicode escape (exactly eight digits)
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escape += source.getwhile(8, HEXDIGITS)
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if len(escape) != 10:
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raise ValueError
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c = int(escape[2:], 16)
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chr(c) # raise ValueError for invalid code
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return LITERAL, c
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elif c in OCTDIGITS:
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# octal escape (up to three digits)
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escape += source.getwhile(2, OCTDIGITS)
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c = int(escape[1:], 8)
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if c > 0o377:
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raise error('octal escape value %r outside of '
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'range 0-0o377' % escape)
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return LITERAL, c
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elif c in DIGITS:
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raise ValueError
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if len(escape) == 2:
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return LITERAL, ord(escape[1])
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except ValueError:
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pass
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raise error("bogus escape: %s" % repr(escape))
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def _escape(source, escape, state):
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# handle escape code in expression
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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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try:
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c = escape[1:2]
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if c == "x":
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# hexadecimal escape
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escape += source.getwhile(2, HEXDIGITS)
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if len(escape) != 4:
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raise ValueError
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return LITERAL, int(escape[2:], 16)
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elif c == "u" and source.istext:
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# unicode escape (exactly four digits)
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escape += source.getwhile(4, HEXDIGITS)
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if len(escape) != 6:
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raise ValueError
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return LITERAL, int(escape[2:], 16)
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elif c == "U" and source.istext:
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# unicode escape (exactly eight digits)
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escape += source.getwhile(8, HEXDIGITS)
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if len(escape) != 10:
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raise ValueError
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c = int(escape[2:], 16)
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chr(c) # raise ValueError for invalid code
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return LITERAL, c
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elif c == "0":
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# octal escape
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escape += source.getwhile(2, OCTDIGITS)
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return LITERAL, int(escape[1:], 8)
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elif c in DIGITS:
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# octal escape *or* decimal group reference (sigh)
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if source.next in DIGITS:
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escape += source.get()
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if (escape[1] in OCTDIGITS and escape[2] in OCTDIGITS and
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source.next in OCTDIGITS):
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# got three octal digits; this is an octal escape
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escape += source.get()
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c = int(escape[1:], 8)
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if c > 0o377:
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raise error('octal escape value %r outside of '
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'range 0-0o377' % escape)
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return LITERAL, c
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# not an octal escape, so this is a group reference
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group = int(escape[1:])
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if group < state.groups:
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if not state.checkgroup(group):
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raise error("cannot refer to open group")
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return GROUPREF, group
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raise ValueError
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if len(escape) == 2:
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return LITERAL, ord(escape[1])
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except ValueError:
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pass
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raise error("bogus escape: %s" % repr(escape))
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def _parse_sub(source, state, nested=True):
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# parse an alternation: a|b|c
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items = []
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itemsappend = items.append
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sourcematch = source.match
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while True:
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itemsappend(_parse(source, state))
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if not sourcematch("|"):
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break
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if nested and source.next is not None and source.next != ")":
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raise error("pattern not properly closed")
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if len(items) == 1:
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return items[0]
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subpattern = SubPattern(state)
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subpatternappend = subpattern.append
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# check if all items share a common prefix
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while True:
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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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subpatternappend(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] is not 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 (the compiler may optimize this even more)
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subpatternappend((IN, [item[0] for item in items]))
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return subpattern
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subpattern.append((BRANCH, (None, items)))
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return subpattern
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def _parse_sub_cond(source, state, condgroup):
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item_yes = _parse(source, state)
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if source.match("|"):
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item_no = _parse(source, state)
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if source.next == "|":
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raise error("conditional backref with more than two branches")
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else:
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item_no = None
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if source.next is not None and source.next != ")":
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raise error("pattern not properly closed")
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subpattern = SubPattern(state)
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subpattern.append((GROUPREF_EXISTS, (condgroup, item_yes, item_no)))
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return subpattern
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def _parse(source, state):
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# parse a simple pattern
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subpattern = SubPattern(state)
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# precompute constants into local variables
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subpatternappend = subpattern.append
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sourceget = source.get
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sourcematch = source.match
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_len = len
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_ord = ord
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verbose = state.flags & SRE_FLAG_VERBOSE
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while True:
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this = source.next
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if this is None:
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break # end of pattern
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if this in "|)":
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break # end of subpattern
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sourceget()
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if verbose:
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# skip whitespace and comments
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if this in WHITESPACE:
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continue
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if this == "#":
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while True:
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this = sourceget()
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if this is None or this == "\n":
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break
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continue
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if this[0] == "\\":
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code = _escape(source, this, state)
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subpatternappend(code)
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elif this not in SPECIAL_CHARS:
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subpatternappend((LITERAL, _ord(this)))
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elif this == "[":
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# character set
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set = []
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setappend = set.append
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## if sourcematch(":"):
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## pass # handle character classes
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if sourcematch("^"):
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setappend((NEGATE, None))
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# check remaining characters
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start = set[:]
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while True:
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this = sourceget()
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if this is None:
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raise error("unexpected end of regular expression")
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if this == "]" and set != start:
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break
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elif this[0] == "\\":
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code1 = _class_escape(source, this)
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else:
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code1 = LITERAL, _ord(this)
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if sourcematch("-"):
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# potential range
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this = sourceget()
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if this is None:
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raise error("unexpected end of regular expression")
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if this == "]":
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if code1[0] is IN:
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code1 = code1[1][0]
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setappend(code1)
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setappend((LITERAL, _ord("-")))
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break
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if this[0] == "\\":
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code2 = _class_escape(source, this)
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else:
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code2 = LITERAL, _ord(this)
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if code1[0] != LITERAL or code2[0] != LITERAL:
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raise error("bad character range")
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lo = code1[1]
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hi = code2[1]
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if hi < lo:
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raise error("bad character range")
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setappend((RANGE, (lo, hi)))
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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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setappend(code1)
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# XXX: <fl> should move set optimization to compiler!
|
|
if _len(set)==1 and set[0][0] is LITERAL:
|
|
subpatternappend(set[0]) # optimization
|
|
elif _len(set)==2 and set[0][0] is NEGATE and set[1][0] is LITERAL:
|
|
subpatternappend((NOT_LITERAL, set[1][1])) # optimization
|
|
else:
|
|
# XXX: <fl> should add charmap optimization here
|
|
subpatternappend((IN, set))
|
|
|
|
elif this in REPEAT_CHARS:
|
|
# repeat previous item
|
|
if this == "?":
|
|
min, max = 0, 1
|
|
elif this == "*":
|
|
min, max = 0, MAXREPEAT
|
|
|
|
elif this == "+":
|
|
min, max = 1, MAXREPEAT
|
|
elif this == "{":
|
|
if source.next == "}":
|
|
subpatternappend((LITERAL, _ord(this)))
|
|
continue
|
|
here = source.tell()
|
|
min, max = 0, MAXREPEAT
|
|
lo = hi = ""
|
|
while source.next in DIGITS:
|
|
lo += sourceget()
|
|
if sourcematch(","):
|
|
while source.next in DIGITS:
|
|
hi += sourceget()
|
|
else:
|
|
hi = lo
|
|
if not sourcematch("}"):
|
|
subpatternappend((LITERAL, _ord(this)))
|
|
source.seek(here)
|
|
continue
|
|
if lo:
|
|
min = int(lo)
|
|
if min >= MAXREPEAT:
|
|
raise OverflowError("the repetition number is too large")
|
|
if hi:
|
|
max = int(hi)
|
|
if max >= MAXREPEAT:
|
|
raise OverflowError("the repetition number is too large")
|
|
if max < min:
|
|
raise error("bad repeat interval")
|
|
else:
|
|
raise error("not supported")
|
|
# figure out which item to repeat
|
|
if subpattern:
|
|
item = subpattern[-1:]
|
|
else:
|
|
item = None
|
|
if not item or (_len(item) == 1 and item[0][0] == AT):
|
|
raise error("nothing to repeat")
|
|
if item[0][0] in _REPEATCODES:
|
|
raise error("multiple repeat")
|
|
if sourcematch("?"):
|
|
subpattern[-1] = (MIN_REPEAT, (min, max, item))
|
|
else:
|
|
subpattern[-1] = (MAX_REPEAT, (min, max, item))
|
|
|
|
elif this == ".":
|
|
subpatternappend((ANY, None))
|
|
|
|
elif this == "(":
|
|
group = 1
|
|
name = None
|
|
condgroup = None
|
|
if sourcematch("?"):
|
|
group = 0
|
|
# options
|
|
char = sourceget()
|
|
if char is None:
|
|
raise error("unexpected end of pattern")
|
|
if char == "P":
|
|
# python extensions
|
|
if sourcematch("<"):
|
|
# named group: skip forward to end of name
|
|
name = source.getuntil(">")
|
|
group = 1
|
|
if not name:
|
|
raise error("missing group name")
|
|
if not name.isidentifier():
|
|
raise error("bad character in group name %r" % name)
|
|
elif sourcematch("="):
|
|
# named backreference
|
|
name = source.getuntil(")")
|
|
if not name:
|
|
raise error("missing group name")
|
|
if not name.isidentifier():
|
|
raise error("bad character in backref group name "
|
|
"%r" % name)
|
|
gid = state.groupdict.get(name)
|
|
if gid is None:
|
|
msg = "unknown group name: {0!r}".format(name)
|
|
raise error(msg)
|
|
subpatternappend((GROUPREF, gid))
|
|
continue
|
|
else:
|
|
char = sourceget()
|
|
if char is None:
|
|
raise error("unexpected end of pattern")
|
|
raise error("unknown specifier: ?P%s" % char)
|
|
elif char == ":":
|
|
# non-capturing group
|
|
group = 2
|
|
elif char == "#":
|
|
# comment
|
|
while True:
|
|
if source.next is None:
|
|
raise error("unbalanced parenthesis")
|
|
if sourceget() == ")":
|
|
break
|
|
continue
|
|
elif char in "=!<":
|
|
# lookahead assertions
|
|
dir = 1
|
|
if char == "<":
|
|
char = sourceget()
|
|
if char is None or char not in "=!":
|
|
raise error("syntax error")
|
|
dir = -1 # lookbehind
|
|
p = _parse_sub(source, state)
|
|
if not sourcematch(")"):
|
|
raise error("unbalanced parenthesis")
|
|
if char == "=":
|
|
subpatternappend((ASSERT, (dir, p)))
|
|
else:
|
|
subpatternappend((ASSERT_NOT, (dir, p)))
|
|
continue
|
|
elif char == "(":
|
|
# conditional backreference group
|
|
condname = source.getuntil(")")
|
|
group = 2
|
|
if not condname:
|
|
raise error("missing group name")
|
|
if condname.isidentifier():
|
|
condgroup = state.groupdict.get(condname)
|
|
if condgroup is None:
|
|
msg = "unknown group name: {0!r}".format(condname)
|
|
raise error(msg)
|
|
else:
|
|
try:
|
|
condgroup = int(condname)
|
|
if condgroup < 0:
|
|
raise ValueError
|
|
except ValueError:
|
|
raise error("bad character in group name")
|
|
if not condgroup:
|
|
raise error("bad group number")
|
|
if condgroup >= MAXGROUPS:
|
|
raise error("the group number is too large")
|
|
elif char in FLAGS:
|
|
# flags
|
|
state.flags |= FLAGS[char]
|
|
while source.next in FLAGS:
|
|
state.flags |= FLAGS[sourceget()]
|
|
verbose = state.flags & SRE_FLAG_VERBOSE
|
|
else:
|
|
raise error("unexpected end of pattern " + char)
|
|
if group:
|
|
# parse group contents
|
|
if group == 2:
|
|
# anonymous group
|
|
group = None
|
|
else:
|
|
group = state.opengroup(name)
|
|
if condgroup:
|
|
p = _parse_sub_cond(source, state, condgroup)
|
|
else:
|
|
p = _parse_sub(source, state)
|
|
if not sourcematch(")"):
|
|
raise error("unbalanced parenthesis")
|
|
if group is not None:
|
|
state.closegroup(group)
|
|
subpatternappend((SUBPATTERN, (group, p)))
|
|
else:
|
|
while True:
|
|
char = sourceget()
|
|
if char is None:
|
|
raise error("unexpected end of pattern")
|
|
if char == ")":
|
|
break
|
|
raise error("unknown extension")
|
|
|
|
elif this == "^":
|
|
subpatternappend((AT, AT_BEGINNING))
|
|
|
|
elif this == "$":
|
|
subpattern.append((AT, AT_END))
|
|
|
|
else:
|
|
raise error("parser error")
|
|
|
|
return subpattern
|
|
|
|
def fix_flags(src, flags):
|
|
# Check and fix flags according to the type of pattern (str or bytes)
|
|
if isinstance(src, str):
|
|
if not flags & SRE_FLAG_ASCII:
|
|
flags |= SRE_FLAG_UNICODE
|
|
elif flags & SRE_FLAG_UNICODE:
|
|
raise ValueError("ASCII and UNICODE flags are incompatible")
|
|
else:
|
|
if flags & SRE_FLAG_UNICODE:
|
|
raise ValueError("can't use UNICODE flag with a bytes pattern")
|
|
return flags
|
|
|
|
def parse(str, flags=0, pattern=None):
|
|
# parse 're' pattern into list of (opcode, argument) tuples
|
|
|
|
source = Tokenizer(str)
|
|
|
|
if pattern is None:
|
|
pattern = Pattern()
|
|
pattern.flags = flags
|
|
pattern.str = str
|
|
|
|
p = _parse_sub(source, pattern, 0)
|
|
p.pattern.flags = fix_flags(str, p.pattern.flags)
|
|
|
|
if source.next is not None:
|
|
if source.next == ")":
|
|
raise error("unbalanced parenthesis")
|
|
else:
|
|
raise error("bogus characters at end of regular expression")
|
|
|
|
if flags & SRE_FLAG_DEBUG:
|
|
p.dump()
|
|
|
|
if not (flags & SRE_FLAG_VERBOSE) and p.pattern.flags & SRE_FLAG_VERBOSE:
|
|
# the VERBOSE flag was switched on inside the pattern. to be
|
|
# on the safe side, we'll parse the whole thing again...
|
|
return parse(str, p.pattern.flags)
|
|
|
|
return p
|
|
|
|
def parse_template(source, pattern):
|
|
# parse 're' replacement string into list of literals and
|
|
# group references
|
|
s = Tokenizer(source)
|
|
sget = s.get
|
|
groups = []
|
|
literals = []
|
|
literal = []
|
|
lappend = literal.append
|
|
def addgroup(index):
|
|
if literal:
|
|
literals.append(''.join(literal))
|
|
del literal[:]
|
|
groups.append((len(literals), index))
|
|
literals.append(None)
|
|
while True:
|
|
this = sget()
|
|
if this is None:
|
|
break # end of replacement string
|
|
if this[0] == "\\":
|
|
# group
|
|
c = this[1]
|
|
if c == "g":
|
|
name = ""
|
|
if s.match("<"):
|
|
name = s.getuntil(">")
|
|
if not name:
|
|
raise error("missing group name")
|
|
try:
|
|
index = int(name)
|
|
if index < 0:
|
|
raise error("negative group number")
|
|
if index >= MAXGROUPS:
|
|
raise error("the group number is too large")
|
|
except ValueError:
|
|
if not name.isidentifier():
|
|
raise error("bad character in group name")
|
|
try:
|
|
index = pattern.groupindex[name]
|
|
except KeyError:
|
|
msg = "unknown group name: {0!r}".format(name)
|
|
raise IndexError(msg)
|
|
addgroup(index)
|
|
elif c == "0":
|
|
if s.next in OCTDIGITS:
|
|
this += sget()
|
|
if s.next in OCTDIGITS:
|
|
this += sget()
|
|
lappend(chr(int(this[1:], 8) & 0xff))
|
|
elif c in DIGITS:
|
|
isoctal = False
|
|
if s.next in DIGITS:
|
|
this += sget()
|
|
if (c in OCTDIGITS and this[2] in OCTDIGITS and
|
|
s.next in OCTDIGITS):
|
|
this += sget()
|
|
isoctal = True
|
|
c = int(this[1:], 8)
|
|
if c > 0o377:
|
|
raise error('octal escape value %r outside of '
|
|
'range 0-0o377' % this)
|
|
lappend(chr(c))
|
|
if not isoctal:
|
|
addgroup(int(this[1:]))
|
|
else:
|
|
try:
|
|
this = chr(ESCAPES[this][1])
|
|
except KeyError:
|
|
pass
|
|
lappend(this)
|
|
else:
|
|
lappend(this)
|
|
if literal:
|
|
literals.append(''.join(literal))
|
|
if not isinstance(source, str):
|
|
# The tokenizer implicitly decodes bytes objects as latin-1, we must
|
|
# therefore re-encode the final representation.
|
|
literals = [None if s is None else s.encode('latin-1') for s in literals]
|
|
return groups, literals
|
|
|
|
def expand_template(template, match):
|
|
g = match.group
|
|
empty = match.string[:0]
|
|
groups, literals = template
|
|
literals = literals[:]
|
|
try:
|
|
for index, group in groups:
|
|
literals[index] = g(group) or empty
|
|
except IndexError:
|
|
raise error("invalid group reference")
|
|
return empty.join(literals)
|