1 # 2 # Secret Labs' Regular Expression Engine 3 # 4 # convert re-style regular expression to sre pattern 5 # 6 # Copyright (c) 1998-2001 by Secret Labs AB. All rights reserved. 7 # 8 # See the sre.py file for information on usage and redistribution. 9 # 10 11 """Internal support module for sre""" 12 13 # XXX: show string offset and offending character for all errors 14 15 import sys 16 17 from sre_constants import * 18 19 SPECIAL_CHARS = ".\\[{()*+?^$|" 20 REPEAT_CHARS = "*+?{" 21 22 DIGITS = set("0123456789") 23 24 OCTDIGITS = set("01234567") 25 HEXDIGITS = set("0123456789abcdefABCDEF") 26 27 WHITESPACE = set(" \t\n\r\v\f") 28 29 ESCAPES = { 30 r"\a": (LITERAL, ord("\a")), 31 r"\b": (LITERAL, ord("\b")), 32 r"\f": (LITERAL, ord("\f")), 33 r"\n": (LITERAL, ord("\n")), 34 r"\r": (LITERAL, ord("\r")), 35 r"\t": (LITERAL, ord("\t")), 36 r"\v": (LITERAL, ord("\v")), 37 r"\\": (LITERAL, ord("\\")) 38 } 39 40 CATEGORIES = { 41 r"\A": (AT, AT_BEGINNING_STRING), # start of string 42 r"\b": (AT, AT_BOUNDARY), 43 r"\B": (AT, AT_NON_BOUNDARY), 44 r"\d": (IN, [(CATEGORY, CATEGORY_DIGIT)]), 45 r"\D": (IN, [(CATEGORY, CATEGORY_NOT_DIGIT)]), 46 r"\s": (IN, [(CATEGORY, CATEGORY_SPACE)]), 47 r"\S": (IN, [(CATEGORY, CATEGORY_NOT_SPACE)]), 48 r"\w": (IN, [(CATEGORY, CATEGORY_WORD)]), 49 r"\W": (IN, [(CATEGORY, CATEGORY_NOT_WORD)]), 50 r"\Z": (AT, AT_END_STRING), # end of string 51 } 52 53 FLAGS = { 54 # standard flags 55 "i": SRE_FLAG_IGNORECASE, 56 "L": SRE_FLAG_LOCALE, 57 "m": SRE_FLAG_MULTILINE, 58 "s": SRE_FLAG_DOTALL, 59 "x": SRE_FLAG_VERBOSE, 60 # extensions 61 "t": SRE_FLAG_TEMPLATE, 62 "u": SRE_FLAG_UNICODE, 63 } 64 65 class Pattern: 66 # master pattern object. keeps track of global attributes 67 def __init__(self): 68 self.flags = 0 69 self.open = [] 70 self.groups = 1 71 self.groupdict = {} 72 self.str = None 73 def opengroup(self, name=None): 74 gid = self.groups 75 self.groups = gid + 1 76 if name is not None: 77 ogid = self.groupdict.get(name, None) 78 if ogid is not None: 79 raise error, ("redefinition of group name %s as group %d; " 80 "was group %d" % (repr(name), gid, ogid)) 81 self.groupdict[name] = gid 82 self.open.append(gid) 83 return gid 84 def closegroup(self, gid): 85 self.open.remove(gid) 86 def checkgroup(self, gid): 87 return gid < self.groups and gid not in self.open 88 89 class SubPattern: 90 # a subpattern, in intermediate form 91 def __init__(self, pattern, data=None): 92 self.pattern = pattern 93 if data is None: 94 data = [] 95 self.data = data 96 self.width = None 97 def dump(self, level=0): 98 nl = 1 99 seqtypes = type(()), type([]) 100 for op, av in self.data: 101 print level*" " + op,; nl = 0 102 if op == "in": 103 # member sublanguage 104 print; nl = 1 105 for op, a in av: 106 print (level+1)*" " + op, a 107 elif op == "branch": 108 print; nl = 1 109 i = 0 110 for a in av[1]: 111 if i > 0: 112 print level*" " + "or" 113 a.dump(level+1); nl = 1 114 i = i + 1 115 elif type(av) in seqtypes: 116 for a in av: 117 if isinstance(a, SubPattern): 118 if not nl: print 119 a.dump(level+1); nl = 1 120 else: 121 print a, ; nl = 0 122 else: 123 print av, ; nl = 0 124 if not nl: print 125 def __repr__(self): 126 return repr(self.data) 127 def __len__(self): 128 return len(self.data) 129 def __delitem__(self, index): 130 del self.data[index] 131 def __getitem__(self, index): 132 if isinstance(index, slice): 133 return SubPattern(self.pattern, self.data[index]) 134 return self.data[index] 135 def __setitem__(self, index, code): 136 self.data[index] = code 137 def insert(self, index, code): 138 self.data.insert(index, code) 139 def append(self, code): 140 self.data.append(code) 141 def getwidth(self): 142 # determine the width (min, max) for this subpattern 143 if self.width: 144 return self.width 145 lo = hi = 0L 146 UNITCODES = (ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY) 147 REPEATCODES = (MIN_REPEAT, MAX_REPEAT) 148 for op, av in self.data: 149 if op is BRANCH: 150 i = sys.maxint 151 j = 0 152 for av in av[1]: 153 l, h = av.getwidth() 154 i = min(i, l) 155 j = max(j, h) 156 lo = lo + i 157 hi = hi + j 158 elif op is CALL: 159 i, j = av.getwidth() 160 lo = lo + i 161 hi = hi + j 162 elif op is SUBPATTERN: 163 i, j = av[1].getwidth() 164 lo = lo + i 165 hi = hi + j 166 elif op in REPEATCODES: 167 i, j = av[2].getwidth() 168 lo = lo + long(i) * av[0] 169 hi = hi + long(j) * av[1] 170 elif op in UNITCODES: 171 lo = lo + 1 172 hi = hi + 1 173 elif op == SUCCESS: 174 break 175 self.width = int(min(lo, sys.maxint)), int(min(hi, sys.maxint)) 176 return self.width 177 178 class Tokenizer: 179 def __init__(self, string): 180 self.string = string 181 self.index = 0 182 self.__next() 183 def __next(self): 184 if self.index >= len(self.string): 185 self.next = None 186 return 187 char = self.string[self.index] 188 if char[0] == "\\": 189 try: 190 c = self.string[self.index + 1] 191 except IndexError: 192 raise error, "bogus escape (end of line)" 193 char = char + c 194 self.index = self.index + len(char) 195 self.next = char 196 def match(self, char, skip=1): 197 if char == self.next: 198 if skip: 199 self.__next() 200 return 1 201 return 0 202 def get(self): 203 this = self.next 204 self.__next() 205 return this 206 def tell(self): 207 return self.index, self.next 208 def seek(self, index): 209 self.index, self.next = index 210 211 def isident(char): 212 return "a" <= char <= "z" or "A" <= char <= "Z" or char == "_" 213 214 def isdigit(char): 215 return "0" <= char <= "9" 216 217 def isname(name): 218 # check that group name is a valid string 219 if not isident(name[0]): 220 return False 221 for char in name[1:]: 222 if not isident(char) and not isdigit(char): 223 return False 224 return True 225 226 def _class_escape(source, escape): 227 # handle escape code inside character class 228 code = ESCAPES.get(escape) 229 if code: 230 return code 231 code = CATEGORIES.get(escape) 232 if code: 233 return code 234 try: 235 c = escape[1:2] 236 if c == "x": 237 # hexadecimal escape (exactly two digits) 238 while source.next in HEXDIGITS and len(escape) < 4: 239 escape = escape + source.get() 240 escape = escape[2:] 241 if len(escape) != 2: 242 raise error, "bogus escape: %s" % repr("\\" + escape) 243 return LITERAL, int(escape, 16) & 0xff 244 elif c in OCTDIGITS: 245 # octal escape (up to three digits) 246 while source.next in OCTDIGITS and len(escape) < 4: 247 escape = escape + source.get() 248 escape = escape[1:] 249 return LITERAL, int(escape, 8) & 0xff 250 elif c in DIGITS: 251 raise error, "bogus escape: %s" % repr(escape) 252 if len(escape) == 2: 253 return LITERAL, ord(escape[1]) 254 except ValueError: 255 pass 256 raise error, "bogus escape: %s" % repr(escape) 257 258 def _escape(source, escape, state): 259 # handle escape code in expression 260 code = CATEGORIES.get(escape) 261 if code: 262 return code 263 code = ESCAPES.get(escape) 264 if code: 265 return code 266 try: 267 c = escape[1:2] 268 if c == "x": 269 # hexadecimal escape 270 while source.next in HEXDIGITS and len(escape) < 4: 271 escape = escape + source.get() 272 if len(escape) != 4: 273 raise ValueError 274 return LITERAL, int(escape[2:], 16) & 0xff 275 elif c == "0": 276 # octal escape 277 while source.next in OCTDIGITS and len(escape) < 4: 278 escape = escape + source.get() 279 return LITERAL, int(escape[1:], 8) & 0xff 280 elif c in DIGITS: 281 # octal escape *or* decimal group reference (sigh) 282 if source.next in DIGITS: 283 escape = escape + source.get() 284 if (escape[1] in OCTDIGITS and escape[2] in OCTDIGITS and 285 source.next in OCTDIGITS): 286 # got three octal digits; this is an octal escape 287 escape = escape + source.get() 288 return LITERAL, int(escape[1:], 8) & 0xff 289 # not an octal escape, so this is a group reference 290 group = int(escape[1:]) 291 if group < state.groups: 292 if not state.checkgroup(group): 293 raise error, "cannot refer to open group" 294 return GROUPREF, group 295 raise ValueError 296 if len(escape) == 2: 297 return LITERAL, ord(escape[1]) 298 except ValueError: 299 pass 300 raise error, "bogus escape: %s" % repr(escape) 301 302 def _parse_sub(source, state, nested=1): 303 # parse an alternation: a|b|c 304 305 items = [] 306 itemsappend = items.append 307 sourcematch = source.match 308 while 1: 309 itemsappend(_parse(source, state)) 310 if sourcematch("|"): 311 continue 312 if not nested: 313 break 314 if not source.next or sourcematch(")", 0): 315 break 316 else: 317 raise error, "pattern not properly closed" 318 319 if len(items) == 1: 320 return items[0] 321 322 subpattern = SubPattern(state) 323 subpatternappend = subpattern.append 324 325 # check if all items share a common prefix 326 while 1: 327 prefix = None 328 for item in items: 329 if not item: 330 break 331 if prefix is None: 332 prefix = item[0] 333 elif item[0] != prefix: 334 break 335 else: 336 # all subitems start with a common "prefix". 337 # move it out of the branch 338 for item in items: 339 del item[0] 340 subpatternappend(prefix) 341 continue # check next one 342 break 343 344 # check if the branch can be replaced by a character set 345 for item in items: 346 if len(item) != 1 or item[0][0] != LITERAL: 347 break 348 else: 349 # we can store this as a character set instead of a 350 # branch (the compiler may optimize this even more) 351 set = [] 352 setappend = set.append 353 for item in items: 354 setappend(item[0]) 355 subpatternappend((IN, set)) 356 return subpattern 357 358 subpattern.append((BRANCH, (None, items))) 359 return subpattern 360 361 def _parse_sub_cond(source, state, condgroup): 362 item_yes = _parse(source, state) 363 if source.match("|"): 364 item_no = _parse(source, state) 365 if source.match("|"): 366 raise error, "conditional backref with more than two branches" 367 else: 368 item_no = None 369 if source.next and not source.match(")", 0): 370 raise error, "pattern not properly closed" 371 subpattern = SubPattern(state) 372 subpattern.append((GROUPREF_EXISTS, (condgroup, item_yes, item_no))) 373 return subpattern 374 375 _PATTERNENDERS = set("|)") 376 _ASSERTCHARS = set("=!<") 377 _LOOKBEHINDASSERTCHARS = set("=!") 378 _REPEATCODES = set([MIN_REPEAT, MAX_REPEAT]) 379 380 def _parse(source, state): 381 # parse a simple pattern 382 subpattern = SubPattern(state) 383 384 # precompute constants into local variables 385 subpatternappend = subpattern.append 386 sourceget = source.get 387 sourcematch = source.match 388 _len = len 389 PATTERNENDERS = _PATTERNENDERS 390 ASSERTCHARS = _ASSERTCHARS 391 LOOKBEHINDASSERTCHARS = _LOOKBEHINDASSERTCHARS 392 REPEATCODES = _REPEATCODES 393 394 while 1: 395 396 if source.next in PATTERNENDERS: 397 break # end of subpattern 398 this = sourceget() 399 if this is None: 400 break # end of pattern 401 402 if state.flags & SRE_FLAG_VERBOSE: 403 # skip whitespace and comments 404 if this in WHITESPACE: 405 continue 406 if this == "#": 407 while 1: 408 this = sourceget() 409 if this in (None, "\n"): 410 break 411 continue 412 413 if this and this[0] not in SPECIAL_CHARS: 414 subpatternappend((LITERAL, ord(this))) 415 416 elif this == "[": 417 # character set 418 set = [] 419 setappend = set.append 420 ## if sourcematch(":"): 421 ## pass # handle character classes 422 if sourcematch("^"): 423 setappend((NEGATE, None)) 424 # check remaining characters 425 start = set[:] 426 while 1: 427 this = sourceget() 428 if this == "]" and set != start: 429 break 430 elif this and this[0] == "\\": 431 code1 = _class_escape(source, this) 432 elif this: 433 code1 = LITERAL, ord(this) 434 else: 435 raise error, "unexpected end of regular expression" 436 if sourcematch("-"): 437 # potential range 438 this = sourceget() 439 if this == "]": 440 if code1[0] is IN: 441 code1 = code1[1][0] 442 setappend(code1) 443 setappend((LITERAL, ord("-"))) 444 break 445 elif this: 446 if this[0] == "\\": 447 code2 = _class_escape(source, this) 448 else: 449 code2 = LITERAL, ord(this) 450 if code1[0] != LITERAL or code2[0] != LITERAL: 451 raise error, "bad character range" 452 lo = code1[1] 453 hi = code2[1] 454 if hi < lo: 455 raise error, "bad character range" 456 setappend((RANGE, (lo, hi))) 457 else: 458 raise error, "unexpected end of regular expression" 459 else: 460 if code1[0] is IN: 461 code1 = code1[1][0] 462 setappend(code1) 463 464 # XXX: <fl> should move set optimization to compiler! 465 if _len(set)==1 and set[0][0] is LITERAL: 466 subpatternappend(set[0]) # optimization 467 elif _len(set)==2 and set[0][0] is NEGATE and set[1][0] is LITERAL: 468 subpatternappend((NOT_LITERAL, set[1][1])) # optimization 469 else: 470 # XXX: <fl> should add charmap optimization here 471 subpatternappend((IN, set)) 472 473 elif this and this[0] in REPEAT_CHARS: 474 # repeat previous item 475 if this == "?": 476 min, max = 0, 1 477 elif this == "*": 478 min, max = 0, MAXREPEAT 479 480 elif this == "+": 481 min, max = 1, MAXREPEAT 482 elif this == "{": 483 if source.next == "}": 484 subpatternappend((LITERAL, ord(this))) 485 continue 486 here = source.tell() 487 min, max = 0, MAXREPEAT 488 lo = hi = "" 489 while source.next in DIGITS: 490 lo = lo + source.get() 491 if sourcematch(","): 492 while source.next in DIGITS: 493 hi = hi + sourceget() 494 else: 495 hi = lo 496 if not sourcematch("}"): 497 subpatternappend((LITERAL, ord(this))) 498 source.seek(here) 499 continue 500 if lo: 501 min = int(lo) 502 if hi: 503 max = int(hi) 504 if max < min: 505 raise error, "bad repeat interval" 506 else: 507 raise error, "not supported" 508 # figure out which item to repeat 509 if subpattern: 510 item = subpattern[-1:] 511 else: 512 item = None 513 if not item or (_len(item) == 1 and item[0][0] == AT): 514 raise error, "nothing to repeat" 515 if item[0][0] in REPEATCODES: 516 raise error, "multiple repeat" 517 if sourcematch("?"): 518 subpattern[-1] = (MIN_REPEAT, (min, max, item)) 519 else: 520 subpattern[-1] = (MAX_REPEAT, (min, max, item)) 521 522 elif this == ".": 523 subpatternappend((ANY, None)) 524 525 elif this == "(": 526 group = 1 527 name = None 528 condgroup = None 529 if sourcematch("?"): 530 group = 0 531 # options 532 if sourcematch("P"): 533 # python extensions 534 if sourcematch("<"): 535 # named group: skip forward to end of name 536 name = "" 537 while 1: 538 char = sourceget() 539 if char is None: 540 raise error, "unterminated name" 541 if char == ">": 542 break 543 name = name + char 544 group = 1 545 if not isname(name): 546 raise error, "bad character in group name" 547 elif sourcematch("="): 548 # named backreference 549 name = "" 550 while 1: 551 char = sourceget() 552 if char is None: 553 raise error, "unterminated name" 554 if char == ")": 555 break 556 name = name + char 557 if not isname(name): 558 raise error, "bad character in group name" 559 gid = state.groupdict.get(name) 560 if gid is None: 561 raise error, "unknown group name" 562 subpatternappend((GROUPREF, gid)) 563 continue 564 else: 565 char = sourceget() 566 if char is None: 567 raise error, "unexpected end of pattern" 568 raise error, "unknown specifier: ?P%s" % char 569 elif sourcematch(":"): 570 # non-capturing group 571 group = 2 572 elif sourcematch("#"): 573 # comment 574 while 1: 575 if source.next is None or source.next == ")": 576 break 577 sourceget() 578 if not sourcematch(")"): 579 raise error, "unbalanced parenthesis" 580 continue 581 elif source.next in ASSERTCHARS: 582 # lookahead assertions 583 char = sourceget() 584 dir = 1 585 if char == "<": 586 if source.next not in LOOKBEHINDASSERTCHARS: 587 raise error, "syntax error" 588 dir = -1 # lookbehind 589 char = sourceget() 590 p = _parse_sub(source, state) 591 if not sourcematch(")"): 592 raise error, "unbalanced parenthesis" 593 if char == "=": 594 subpatternappend((ASSERT, (dir, p))) 595 else: 596 subpatternappend((ASSERT_NOT, (dir, p))) 597 continue 598 elif sourcematch("("): 599 # conditional backreference group 600 condname = "" 601 while 1: 602 char = sourceget() 603 if char is None: 604 raise error, "unterminated name" 605 if char == ")": 606 break 607 condname = condname + char 608 group = 2 609 if isname(condname): 610 condgroup = state.groupdict.get(condname) 611 if condgroup is None: 612 raise error, "unknown group name" 613 else: 614 try: 615 condgroup = int(condname) 616 except ValueError: 617 raise error, "bad character in group name" 618 else: 619 # flags 620 if not source.next in FLAGS: 621 raise error, "unexpected end of pattern" 622 while source.next in FLAGS: 623 state.flags = state.flags | FLAGS[sourceget()] 624 if group: 625 # parse group contents 626 if group == 2: 627 # anonymous group 628 group = None 629 else: 630 group = state.opengroup(name) 631 if condgroup: 632 p = _parse_sub_cond(source, state, condgroup) 633 else: 634 p = _parse_sub(source, state) 635 if not sourcematch(")"): 636 raise error, "unbalanced parenthesis" 637 if group is not None: 638 state.closegroup(group) 639 subpatternappend((SUBPATTERN, (group, p))) 640 else: 641 while 1: 642 char = sourceget() 643 if char is None: 644 raise error, "unexpected end of pattern" 645 if char == ")": 646 break 647 raise error, "unknown extension" 648 649 elif this == "^": 650 subpatternappend((AT, AT_BEGINNING)) 651 652 elif this == "$": 653 subpattern.append((AT, AT_END)) 654 655 elif this and this[0] == "\\": 656 code = _escape(source, this, state) 657 subpatternappend(code) 658 659 else: 660 raise error, "parser error" 661 662 return subpattern 663 664 def parse(str, flags=0, pattern=None): 665 # parse 're' pattern into list of (opcode, argument) tuples 666 667 source = Tokenizer(str) 668 669 if pattern is None: 670 pattern = Pattern() 671 pattern.flags = flags 672 pattern.str = str 673 674 p = _parse_sub(source, pattern, 0) 675 676 tail = source.get() 677 if tail == ")": 678 raise error, "unbalanced parenthesis" 679 elif tail: 680 raise error, "bogus characters at end of regular expression" 681 682 if flags & SRE_FLAG_DEBUG: 683 p.dump() 684 685 if not (flags & SRE_FLAG_VERBOSE) and p.pattern.flags & SRE_FLAG_VERBOSE: 686 # the VERBOSE flag was switched on inside the pattern. to be 687 # on the safe side, we'll parse the whole thing again... 688 return parse(str, p.pattern.flags) 689 690 return p 691 692 def parse_template(source, pattern): 693 # parse 're' replacement string into list of literals and 694 # group references 695 s = Tokenizer(source) 696 sget = s.get 697 p = [] 698 a = p.append 699 def literal(literal, p=p, pappend=a): 700 if p and p[-1][0] is LITERAL: 701 p[-1] = LITERAL, p[-1][1] + literal 702 else: 703 pappend((LITERAL, literal)) 704 sep = source[:0] 705 if type(sep) is type(""): 706 makechar = chr 707 else: 708 makechar = unichr 709 while 1: 710 this = sget() 711 if this is None: 712 break # end of replacement string 713 if this and this[0] == "\\": 714 # group 715 c = this[1:2] 716 if c == "g": 717 name = "" 718 if s.match("<"): 719 while 1: 720 char = sget() 721 if char is None: 722 raise error, "unterminated group name" 723 if char == ">": 724 break 725 name = name + char 726 if not name: 727 raise error, "bad group name" 728 try: 729 index = int(name) 730 if index < 0: 731 raise error, "negative group number" 732 except ValueError: 733 if not isname(name): 734 raise error, "bad character in group name" 735 try: 736 index = pattern.groupindex[name] 737 except KeyError: 738 raise IndexError, "unknown group name" 739 a((MARK, index)) 740 elif c == "0": 741 if s.next in OCTDIGITS: 742 this = this + sget() 743 if s.next in OCTDIGITS: 744 this = this + sget() 745 literal(makechar(int(this[1:], 8) & 0xff)) 746 elif c in DIGITS: 747 isoctal = False 748 if s.next in DIGITS: 749 this = this + sget() 750 if (c in OCTDIGITS and this[2] in OCTDIGITS and 751 s.next in OCTDIGITS): 752 this = this + sget() 753 isoctal = True 754 literal(makechar(int(this[1:], 8) & 0xff)) 755 if not isoctal: 756 a((MARK, int(this[1:]))) 757 else: 758 try: 759 this = makechar(ESCAPES[this][1]) 760 except KeyError: 761 pass 762 literal(this) 763 else: 764 literal(this) 765 # convert template to groups and literals lists 766 i = 0 767 groups = [] 768 groupsappend = groups.append 769 literals = [None] * len(p) 770 for c, s in p: 771 if c is MARK: 772 groupsappend((i, s)) 773 # literal[i] is already None 774 else: 775 literals[i] = s 776 i = i + 1 777 return groups, literals 778 779 def expand_template(template, match): 780 g = match.group 781 sep = match.string[:0] 782 groups, literals = template 783 literals = literals[:] 784 try: 785 for index, group in groups: 786 literals[index] = s = g(group) 787 if s is None: 788 raise error, "unmatched group" 789 except IndexError: 790 raise error, "invalid group reference" 791 return sep.join(literals)