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sre_parse.py
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# # Secret Labs' Regular Expression Engine # # convert re-style regular expression to sre pattern # # Copyright (c) 1998-2001 by Secret Labs AB. All rights reserved. # # See the sre.py file for information on usage and redistribution. # """Internal support module for sre""" # XXX: show string offset and offending character for all errors import sys from sre_constants import * SPECIAL_CHARS = ".\\[{()*+?^$|" REPEAT_CHARS = "*+?{" DIGITS = set("0123456789") OCTDIGITS = set("01234567") HEXDIGITS = set("0123456789abcdefABCDEF") WHITESPACE = set(" \t\n\r\v\f") ESCAPES = { r"\a": (LITERAL, ord("\a")), r"\b": (LITERAL, ord("\b")), r"\f": (LITERAL, ord("\f")), r"\n": (LITERAL, ord("\n")), r"\r": (LITERAL, ord("\r")), r"\t": (LITERAL, ord("\t")), r"\v": (LITERAL, ord("\v")), r"\\": (LITERAL, ord("\\")) } CATEGORIES = { r"\A": (AT, AT_BEGINNING_STRING), # start of string r"\b": (AT, AT_BOUNDARY), r"\B": (AT, AT_NON_BOUNDARY), r"\d": (IN, [(CATEGORY, CATEGORY_DIGIT)]), r"\D": (IN, [(CATEGORY, CATEGORY_NOT_DIGIT)]), r"\s": (IN, [(CATEGORY, CATEGORY_SPACE)]), r"\S": (IN, [(CATEGORY, CATEGORY_NOT_SPACE)]), r"\w": (IN, [(CATEGORY, CATEGORY_WORD)]), r"\W": (IN, [(CATEGORY, CATEGORY_NOT_WORD)]), r"\Z": (AT, AT_END_STRING), # end of string } FLAGS = { # standard flags "i": SRE_FLAG_IGNORECASE, "L": SRE_FLAG_LOCALE, "m": SRE_FLAG_MULTILINE, "s": SRE_FLAG_DOTALL, "x": SRE_FLAG_VERBOSE, # extensions "t": SRE_FLAG_TEMPLATE, "u": SRE_FLAG_UNICODE, } class Pattern: # master pattern object. keeps track of global attributes def __init__(self): self.flags = 0 self.open = [] self.groups = 1 self.groupdict = {} self.lookbehind = 0 def opengroup(self, name=None): gid = self.groups self.groups = gid + 1 if name is not None: ogid = self.groupdict.get(name, None) if ogid is not None: raise error, ("redefinition of group name %s as group %d; " "was group %d" % (repr(name), gid, ogid)) self.groupdict[name] = gid self.open.append(gid) return gid def closegroup(self, gid): self.open.remove(gid) def checkgroup(self, gid): return gid < self.groups and gid not in self.open class SubPattern: # a subpattern, in intermediate form def __init__(self, pattern, data=None): self.pattern = pattern if data is None: data = [] self.data = data self.width = None def dump(self, level=0): seqtypes = (tuple, list) for op, av in self.data: print level*" " + op, if op == IN: # member sublanguage print for op, a in av: print (level+1)*" " + op, a elif op == BRANCH: print for i, a in enumerate(av[1]): if i: print level*" " + "or" a.dump(level+1) elif op == GROUPREF_EXISTS: condgroup, item_yes, item_no = av print condgroup item_yes.dump(level+1) if item_no: print level*" " + "else" item_no.dump(level+1) elif isinstance(av, seqtypes): nl = 0 for a in av: if isinstance(a, SubPattern): if not nl: print a.dump(level+1) nl = 1 else: print a, nl = 0 if not nl: print else: print av def __repr__(self): return repr(self.data) def __len__(self): return len(self.data) def __delitem__(self, index): del self.data[index] def __getitem__(self, index): if isinstance(index, slice): return SubPattern(self.pattern, self.data[index]) return self.data[index] def __setitem__(self, index, code): self.data[index] = code def insert(self, index, code): self.data.insert(index, code) def append(self, code): self.data.append(code) def getwidth(self): # determine the width (min, max) for this subpattern if self.width: return self.width lo = hi = 0 UNITCODES = (ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY) REPEATCODES = (MIN_REPEAT, MAX_REPEAT) for op, av in self.data: if op is BRANCH: i = MAXREPEAT - 1 j = 0 for av in av[1]: l, h = av.getwidth() i = min(i, l) j = max(j, h) lo = lo + i hi = hi + j elif op is CALL: i, j = av.getwidth() lo = lo + i hi = hi + j elif op is SUBPATTERN: i, j = av[1].getwidth() lo = lo + i hi = hi + j elif op in REPEATCODES: i, j = av[2].getwidth() lo = lo + i * av[0] hi = hi + j * av[1] elif op in UNITCODES: lo = lo + 1 hi = hi + 1 elif op == SUCCESS: break self.width = min(lo, MAXREPEAT - 1), min(hi, MAXREPEAT) return self.width class Tokenizer: def __init__(self, string): self.string = string self.index = 0 self.__next() def __next(self): if self.index >= len(self.string): self.next = None return char = self.string[self.index] if char[0] == "\\": try: c = self.string[self.index + 1] except IndexError: raise error, "bogus escape (end of line)" char = char + c self.index = self.index + len(char) self.next = char def match(self, char, skip=1): if char == self.next: if skip: self.__next() return 1 return 0 def get(self): this = self.next self.__next() return this def tell(self): return self.index, self.next def seek(self, index): self.index, self.next = index def isident(char): return "a" <= char <= "z" or "A" <= char <= "Z" or char == "_" def isdigit(char): return "0" <= char <= "9" def isname(name): # check that group name is a valid string if not isident(name[0]): return False for char in name[1:]: if not isident(char) and not isdigit(char): return False return True def _class_escape(source, escape): # handle escape code inside character class code = ESCAPES.get(escape) if code: return code code = CATEGORIES.get(escape) if code and code[0] == IN: return code try: c = escape[1:2] if c == "x": # hexadecimal escape (exactly two digits) while source.next in HEXDIGITS and len(escape) < 4: escape = escape + source.get() escape = escape[2:] if len(escape) != 2: raise error, "bogus escape: %s" % repr("\\" + escape) return LITERAL, int(escape, 16) & 0xff elif c in OCTDIGITS: # octal escape (up to three digits) while source.next in OCTDIGITS and len(escape) < 4: escape = escape + source.get() escape = escape[1:] return LITERAL, int(escape, 8) & 0xff elif c in DIGITS: raise error, "bogus escape: %s" % repr(escape) if len(escape) == 2: return LITERAL, ord(escape[1]) except ValueError: pass raise error, "bogus escape: %s" % repr(escape) def _escape(source, escape, state): # handle escape code in expression code = CATEGORIES.get(escape) if code: return code code = ESCAPES.get(escape) if code: return code try: c = escape[1:2] if c == "x": # hexadecimal escape while source.next in HEXDIGITS and len(escape) < 4: escape = escape + source.get() if len(escape) != 4: raise ValueError return LITERAL, int(escape[2:], 16) & 0xff elif c == "0": # octal escape while source.next in OCTDIGITS and len(escape) < 4: escape = escape + source.get() return LITERAL, int(escape[1:], 8) & 0xff elif c in DIGITS: # octal escape *or* decimal group reference (sigh) if source.next in DIGITS: escape = escape + source.get() if (escape[1] in OCTDIGITS and escape[2] in OCTDIGITS and source.next in OCTDIGITS): # got three octal digits; this is an octal escape escape = escape + source.get() return LITERAL, int(escape[1:], 8) & 0xff # not an octal escape, so this is a group reference group = int(escape[1:]) if group < state.groups: if not state.checkgroup(group): raise error, "cannot refer to open group" if state.lookbehind: import warnings warnings.warn('group references in lookbehind ' 'assertions are not supported', RuntimeWarning) return GROUPREF, group raise ValueError if len(escape) == 2: return LITERAL, ord(escape[1]) except ValueError: pass raise error, "bogus escape: %s" % repr(escape) def _parse_sub(source, state, nested=1): # parse an alternation: a|b|c items = [] itemsappend = items.append sourcematch = source.match while 1: itemsappend(_parse(source, state)) if sourcematch("|"): continue if not nested: break if not source.next or sourcematch(")", 0): break else: raise error, "pattern not properly closed" if len(items) == 1: return items[0] subpattern = SubPattern(state) subpatternappend = subpattern.append # check if all items share a common prefix while 1: prefix = None for item in items: if not item: break if prefix is None: prefix = item[0] elif item[0] != prefix: break else: # all subitems start with a common "prefix". # move it out of the branch for item in items: del item[0] subpatternappend(prefix) continue # check next one break # check if the branch can be replaced by a character set for item in items: if len(item) != 1 or item[0][0] != LITERAL: break else: # we can store this as a character set instead of a # branch (the compiler may optimize this even more) set = [] setappend = set.append for item in items: setappend(item[0]) subpatternappend((IN, set)) return subpattern subpattern.append((BRANCH, (None, items))) return subpattern def _parse_sub_cond(source, state, condgroup): item_yes = _parse(source, state) if source.match("|"): item_no = _parse(source, state) if source.match("|"): raise error, "conditional backref with more than two branches" else: item_no = None if source.next and not source.match(")", 0): raise error, "pattern not properly closed" subpattern = SubPattern(state) subpattern.append((GROUPREF_EXISTS, (condgroup, item_yes, item_no))) return subpattern _PATTERNENDERS = set("|)") _ASSERTCHARS = set("=!<") _LOOKBEHINDASSERTCHARS = set("=!") _REPEATCODES = set([MIN_REPEAT, MAX_REPEAT]) def _parse(source, state): # parse a simple pattern subpattern = SubPattern(state) # precompute constants into local variables subpatternappend = subpattern.append sourceget = source.get sourcematch = source.match _len = len PATTERNENDERS = _PATTERNENDERS ASSERTCHARS = _ASSERTCHARS LOOKBEHINDASSERTCHARS = _LOOKBEHINDASSERTCHARS REPEATCODES = _REPEATCODES while 1: if source.next in PATTERNENDERS: break # end of subpattern this = sourceget() if this is None: break # end of pattern if state.flags & SRE_FLAG_VERBOSE: # skip whitespace and comments if this in WHITESPACE: continue if this == "#": while 1: this = sourceget() if this in (None, "\n"): break continue if this and this[0] not in SPECIAL_CHARS: subpatternappend((LITERAL, ord(this))) elif this == "[": # character set set = [] setappend = set.append ## if sourcematch(":"): ## pass # handle character classes if sourcematch("^"): setappend((NEGATE, None)) # check remaining characters start = set[:] while 1: this = sourceget() if this == "]" and set != start: break elif this and this[0] == "\\": code1 = _class_escape(source, this) elif this: code1 = LITERAL, ord(this) else: raise error, "unexpected end of regular expression" if sourcematch("-"): # potential range this = sourceget() if this == "]": if code1[0] is IN: code1 = code1[1][0] setappend(code1) setappend((LITERAL, ord("-"))) break elif this: if this[0] == "\\": code2 = _class_escape(source, this) else: code2 = LITERAL, ord(this) if code1[0] != LITERAL or code2[0] != LITERAL: raise error, "bad character range" lo = code1[1] hi = code2[1] if hi < lo: raise error, "bad character range" setappend((RANGE, (lo, hi))) else: raise error, "unexpected end of regular expression" else: if code1[0] is IN: code1 = code1[1][0] setappend(code1) # 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 and this[0] 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 = lo + source.get() if sourcematch(","): while source.next in DIGITS: hi = 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 if sourcematch("P"): # python extensions if sourcematch("<"): # named group: skip forward to end of name name = "" while 1: char = sourceget() if char is None: raise error, "unterminated name" if char == ">": break name = name + char group = 1 if not name: raise error("missing group name") if not isname(name): raise error("bad character in group name %r" % name) elif sourcematch("="): # named backreference name = "" while 1: char = sourceget() if char is None: raise error, "unterminated name" if char == ")": break name = name + char if not name: raise error("missing group name") if not isname(name): 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) if state.lookbehind: import warnings warnings.warn('group references in lookbehind ' 'assertions are not supported', RuntimeWarning) 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 sourcematch(":"): # non-capturing group group = 2 elif sourcematch("#"): # comment while 1: if source.next is None or source.next == ")": break sourceget() if not sourcematch(")"): raise error, "unbalanced parenthesis" continue elif source.next in ASSERTCHARS: # lookahead assertions char = sourceget() dir = 1 if char == "<": if source.next not in LOOKBEHINDASSERTCHARS: raise error, "syntax error" dir = -1 # lookbehind char = sourceget() state.lookbehind += 1 p = _parse_sub(source, state) if dir < 0: state.lookbehind -= 1 if not sourcematch(")"): raise error, "unbalanced parenthesis" if char == "=": subpatternappend((ASSERT, (dir, p))) else: subpatternappend((ASSERT_NOT, (dir, p))) continue elif sourcematch("("): # conditional backreference group condname = "" while 1: char = sourceget() if char is None: raise error, "unterminated name" if char == ")": break condname = condname + char group = 2 if not condname: raise error("missing group name") if isname(condname): 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) except ValueError: raise error, "bad character in group name" if state.lookbehind: import warnings warnings.warn('group references in lookbehind ' 'assertions are not supported', RuntimeWarning) else: # flags if not source.next in FLAGS: raise error, "unexpected end of pattern" while source.next in FLAGS: state.flags = state.flags | FLAGS[sourceget()] 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 1: 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)) elif this and this[0] == "\\": code = _escape(source, this, state) subpatternappend(code) else: raise error, "parser error" return subpattern 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) tail = source.get() if tail == ")": raise error, "unbalanced parenthesis" elif tail: raise error, "bogus characters at end of regular expression" 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) if flags & SRE_FLAG_DEBUG: p.dump() return p def parse_template(source, pattern): # parse 're' replacement string into list of literals and # group references s = Tokenizer(source) sget = s.get p = [] a = p.append def literal(literal, p=p, pappend=a): if p and p[-1][0] is LITERAL: p[-1] = LITERAL, p[-1][1] + literal else: pappend((LITERAL, literal)) sep = source[:0] if type(sep) is type(""): makechar = chr else: makechar = unichr while 1: this = sget() if this is None: break # end of replacement string if this and this[0] == "\\": # group c = this[1:2] if c == "g": name = "" if s.match("<"): while 1: char = sget() if char is None: raise error, "unterminated group name" if char == ">": break name = name + char if not name: raise error, "missing group name" try: index = int(name) if index < 0: raise error, "negative group number" except ValueError: if not isname(name): 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) a((MARK, index)) elif c == "0": if s.next in OCTDIGITS: this = this + sget() if s.next in OCTDIGITS: this = this + sget() literal(makechar(int(this[1:], 8) & 0xff)) elif c in DIGITS: isoctal = False if s.next in DIGITS: this = this + sget() if (c in OCTDIGITS and this[2] in OCTDIGITS and s.next in OCTDIGITS): this = this + sget() isoctal = True literal(makechar(int(this[1:], 8) & 0xff)) if not isoctal: a((MARK, int(this[1:]))) else: try: this = makechar(ESCAPES[this][1]) except KeyError: pass literal(this) else: literal(this) # convert template to groups and literals lists i = 0 groups = [] groupsappend = groups.append literals = [None] * len(p) for c, s in p: if c is MARK: groupsappend((i, s)) # literal[i] is already None else: literals[i] = s i = i + 1 return groups, literals def expand_template(template, match): g = match.group sep = match.string[:0] groups, literals = template literals = literals[:] try: for index, group in groups: literals[index] = s = g(group) if s is None: raise error, "unmatched group" except IndexError: raise error, "invalid group reference" return sep.join(literals)