Add missing issue number in Misc/NEWS entry.
[python.git] / Lib / sre_parse.py
blob182d1eb44f8b9911fc652eebae8e6d52a1ee6854
2 # Secret Labs' Regular Expression Engine
4 # convert re-style regular expression to sre pattern
6 # Copyright (c) 1998-2001 by Secret Labs AB. All rights reserved.
8 # See the sre.py file for information on usage and redistribution.
11 """Internal support module for sre"""
13 # XXX: show string offset and offending character for all errors
15 import sys
17 from sre_constants import *
19 SPECIAL_CHARS = ".\\[{()*+?^$|"
20 REPEAT_CHARS = "*+?{"
22 DIGITS = set("0123456789")
24 OCTDIGITS = set("01234567")
25 HEXDIGITS = set("0123456789abcdefABCDEF")
27 WHITESPACE = set(" \t\n\r\v\f")
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("\\"))
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
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,
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 def opengroup(self, name=None):
73 gid = self.groups
74 self.groups = gid + 1
75 if name is not None:
76 ogid = self.groupdict.get(name, None)
77 if ogid is not None:
78 raise error, ("redefinition of group name %s as group %d; "
79 "was group %d" % (repr(name), gid, ogid))
80 self.groupdict[name] = gid
81 self.open.append(gid)
82 return gid
83 def closegroup(self, gid):
84 self.open.remove(gid)
85 def checkgroup(self, gid):
86 return gid < self.groups and gid not in self.open
88 class SubPattern:
89 # a subpattern, in intermediate form
90 def __init__(self, pattern, data=None):
91 self.pattern = pattern
92 if data is None:
93 data = []
94 self.data = data
95 self.width = None
96 def dump(self, level=0):
97 nl = 1
98 seqtypes = type(()), type([])
99 for op, av in self.data:
100 print level*" " + op,; nl = 0
101 if op == "in":
102 # member sublanguage
103 print; nl = 1
104 for op, a in av:
105 print (level+1)*" " + op, a
106 elif op == "branch":
107 print; nl = 1
108 i = 0
109 for a in av[1]:
110 if i > 0:
111 print level*" " + "or"
112 a.dump(level+1); nl = 1
113 i = i + 1
114 elif type(av) in seqtypes:
115 for a in av:
116 if isinstance(a, SubPattern):
117 if not nl: print
118 a.dump(level+1); nl = 1
119 else:
120 print a, ; nl = 0
121 else:
122 print av, ; nl = 0
123 if not nl: print
124 def __repr__(self):
125 return repr(self.data)
126 def __len__(self):
127 return len(self.data)
128 def __delitem__(self, index):
129 del self.data[index]
130 def __getitem__(self, index):
131 if isinstance(index, slice):
132 return SubPattern(self.pattern, self.data[index])
133 return self.data[index]
134 def __setitem__(self, index, code):
135 self.data[index] = code
136 def insert(self, index, code):
137 self.data.insert(index, code)
138 def append(self, code):
139 self.data.append(code)
140 def getwidth(self):
141 # determine the width (min, max) for this subpattern
142 if self.width:
143 return self.width
144 lo = hi = 0L
145 UNITCODES = (ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY)
146 REPEATCODES = (MIN_REPEAT, MAX_REPEAT)
147 for op, av in self.data:
148 if op is BRANCH:
149 i = sys.maxint
150 j = 0
151 for av in av[1]:
152 l, h = av.getwidth()
153 i = min(i, l)
154 j = max(j, h)
155 lo = lo + i
156 hi = hi + j
157 elif op is CALL:
158 i, j = av.getwidth()
159 lo = lo + i
160 hi = hi + j
161 elif op is SUBPATTERN:
162 i, j = av[1].getwidth()
163 lo = lo + i
164 hi = hi + j
165 elif op in REPEATCODES:
166 i, j = av[2].getwidth()
167 lo = lo + long(i) * av[0]
168 hi = hi + long(j) * av[1]
169 elif op in UNITCODES:
170 lo = lo + 1
171 hi = hi + 1
172 elif op == SUCCESS:
173 break
174 self.width = int(min(lo, sys.maxint)), int(min(hi, sys.maxint))
175 return self.width
177 class Tokenizer:
178 def __init__(self, string):
179 self.string = string
180 self.index = 0
181 self.__next()
182 def __next(self):
183 if self.index >= len(self.string):
184 self.next = None
185 return
186 char = self.string[self.index]
187 if char[0] == "\\":
188 try:
189 c = self.string[self.index + 1]
190 except IndexError:
191 raise error, "bogus escape (end of line)"
192 char = char + c
193 self.index = self.index + len(char)
194 self.next = char
195 def match(self, char, skip=1):
196 if char == self.next:
197 if skip:
198 self.__next()
199 return 1
200 return 0
201 def get(self):
202 this = self.next
203 self.__next()
204 return this
205 def tell(self):
206 return self.index, self.next
207 def seek(self, index):
208 self.index, self.next = index
210 def isident(char):
211 return "a" <= char <= "z" or "A" <= char <= "Z" or char == "_"
213 def isdigit(char):
214 return "0" <= char <= "9"
216 def isname(name):
217 # check that group name is a valid string
218 if not isident(name[0]):
219 return False
220 for char in name[1:]:
221 if not isident(char) and not isdigit(char):
222 return False
223 return True
225 def _class_escape(source, escape):
226 # handle escape code inside character class
227 code = ESCAPES.get(escape)
228 if code:
229 return code
230 code = CATEGORIES.get(escape)
231 if code:
232 return code
233 try:
234 c = escape[1:2]
235 if c == "x":
236 # hexadecimal escape (exactly two digits)
237 while source.next in HEXDIGITS and len(escape) < 4:
238 escape = escape + source.get()
239 escape = escape[2:]
240 if len(escape) != 2:
241 raise error, "bogus escape: %s" % repr("\\" + escape)
242 return LITERAL, int(escape, 16) & 0xff
243 elif c in OCTDIGITS:
244 # octal escape (up to three digits)
245 while source.next in OCTDIGITS and len(escape) < 4:
246 escape = escape + source.get()
247 escape = escape[1:]
248 return LITERAL, int(escape, 8) & 0xff
249 elif c in DIGITS:
250 raise error, "bogus escape: %s" % repr(escape)
251 if len(escape) == 2:
252 return LITERAL, ord(escape[1])
253 except ValueError:
254 pass
255 raise error, "bogus escape: %s" % repr(escape)
257 def _escape(source, escape, state):
258 # handle escape code in expression
259 code = CATEGORIES.get(escape)
260 if code:
261 return code
262 code = ESCAPES.get(escape)
263 if code:
264 return code
265 try:
266 c = escape[1:2]
267 if c == "x":
268 # hexadecimal escape
269 while source.next in HEXDIGITS and len(escape) < 4:
270 escape = escape + source.get()
271 if len(escape) != 4:
272 raise ValueError
273 return LITERAL, int(escape[2:], 16) & 0xff
274 elif c == "0":
275 # octal escape
276 while source.next in OCTDIGITS and len(escape) < 4:
277 escape = escape + source.get()
278 return LITERAL, int(escape[1:], 8) & 0xff
279 elif c in DIGITS:
280 # octal escape *or* decimal group reference (sigh)
281 if source.next in DIGITS:
282 escape = escape + source.get()
283 if (escape[1] in OCTDIGITS and escape[2] in OCTDIGITS and
284 source.next in OCTDIGITS):
285 # got three octal digits; this is an octal escape
286 escape = escape + source.get()
287 return LITERAL, int(escape[1:], 8) & 0xff
288 # not an octal escape, so this is a group reference
289 group = int(escape[1:])
290 if group < state.groups:
291 if not state.checkgroup(group):
292 raise error, "cannot refer to open group"
293 return GROUPREF, group
294 raise ValueError
295 if len(escape) == 2:
296 return LITERAL, ord(escape[1])
297 except ValueError:
298 pass
299 raise error, "bogus escape: %s" % repr(escape)
301 def _parse_sub(source, state, nested=1):
302 # parse an alternation: a|b|c
304 items = []
305 itemsappend = items.append
306 sourcematch = source.match
307 while 1:
308 itemsappend(_parse(source, state))
309 if sourcematch("|"):
310 continue
311 if not nested:
312 break
313 if not source.next or sourcematch(")", 0):
314 break
315 else:
316 raise error, "pattern not properly closed"
318 if len(items) == 1:
319 return items[0]
321 subpattern = SubPattern(state)
322 subpatternappend = subpattern.append
324 # check if all items share a common prefix
325 while 1:
326 prefix = None
327 for item in items:
328 if not item:
329 break
330 if prefix is None:
331 prefix = item[0]
332 elif item[0] != prefix:
333 break
334 else:
335 # all subitems start with a common "prefix".
336 # move it out of the branch
337 for item in items:
338 del item[0]
339 subpatternappend(prefix)
340 continue # check next one
341 break
343 # check if the branch can be replaced by a character set
344 for item in items:
345 if len(item) != 1 or item[0][0] != LITERAL:
346 break
347 else:
348 # we can store this as a character set instead of a
349 # branch (the compiler may optimize this even more)
350 set = []
351 setappend = set.append
352 for item in items:
353 setappend(item[0])
354 subpatternappend((IN, set))
355 return subpattern
357 subpattern.append((BRANCH, (None, items)))
358 return subpattern
360 def _parse_sub_cond(source, state, condgroup):
361 item_yes = _parse(source, state)
362 if source.match("|"):
363 item_no = _parse(source, state)
364 if source.match("|"):
365 raise error, "conditional backref with more than two branches"
366 else:
367 item_no = None
368 if source.next and not source.match(")", 0):
369 raise error, "pattern not properly closed"
370 subpattern = SubPattern(state)
371 subpattern.append((GROUPREF_EXISTS, (condgroup, item_yes, item_no)))
372 return subpattern
374 _PATTERNENDERS = set("|)")
375 _ASSERTCHARS = set("=!<")
376 _LOOKBEHINDASSERTCHARS = set("=!")
377 _REPEATCODES = set([MIN_REPEAT, MAX_REPEAT])
379 def _parse(source, state):
380 # parse a simple pattern
381 subpattern = SubPattern(state)
383 # precompute constants into local variables
384 subpatternappend = subpattern.append
385 sourceget = source.get
386 sourcematch = source.match
387 _len = len
388 PATTERNENDERS = _PATTERNENDERS
389 ASSERTCHARS = _ASSERTCHARS
390 LOOKBEHINDASSERTCHARS = _LOOKBEHINDASSERTCHARS
391 REPEATCODES = _REPEATCODES
393 while 1:
395 if source.next in PATTERNENDERS:
396 break # end of subpattern
397 this = sourceget()
398 if this is None:
399 break # end of pattern
401 if state.flags & SRE_FLAG_VERBOSE:
402 # skip whitespace and comments
403 if this in WHITESPACE:
404 continue
405 if this == "#":
406 while 1:
407 this = sourceget()
408 if this in (None, "\n"):
409 break
410 continue
412 if this and this[0] not in SPECIAL_CHARS:
413 subpatternappend((LITERAL, ord(this)))
415 elif this == "[":
416 # character set
417 set = []
418 setappend = set.append
419 ## if sourcematch(":"):
420 ## pass # handle character classes
421 if sourcematch("^"):
422 setappend((NEGATE, None))
423 # check remaining characters
424 start = set[:]
425 while 1:
426 this = sourceget()
427 if this == "]" and set != start:
428 break
429 elif this and this[0] == "\\":
430 code1 = _class_escape(source, this)
431 elif this:
432 code1 = LITERAL, ord(this)
433 else:
434 raise error, "unexpected end of regular expression"
435 if sourcematch("-"):
436 # potential range
437 this = sourceget()
438 if this == "]":
439 if code1[0] is IN:
440 code1 = code1[1][0]
441 setappend(code1)
442 setappend((LITERAL, ord("-")))
443 break
444 elif this:
445 if this[0] == "\\":
446 code2 = _class_escape(source, this)
447 else:
448 code2 = LITERAL, ord(this)
449 if code1[0] != LITERAL or code2[0] != LITERAL:
450 raise error, "bad character range"
451 lo = code1[1]
452 hi = code2[1]
453 if hi < lo:
454 raise error, "bad character range"
455 setappend((RANGE, (lo, hi)))
456 else:
457 raise error, "unexpected end of regular expression"
458 else:
459 if code1[0] is IN:
460 code1 = code1[1][0]
461 setappend(code1)
463 # XXX: <fl> should move set optimization to compiler!
464 if _len(set)==1 and set[0][0] is LITERAL:
465 subpatternappend(set[0]) # optimization
466 elif _len(set)==2 and set[0][0] is NEGATE and set[1][0] is LITERAL:
467 subpatternappend((NOT_LITERAL, set[1][1])) # optimization
468 else:
469 # XXX: <fl> should add charmap optimization here
470 subpatternappend((IN, set))
472 elif this and this[0] in REPEAT_CHARS:
473 # repeat previous item
474 if this == "?":
475 min, max = 0, 1
476 elif this == "*":
477 min, max = 0, MAXREPEAT
479 elif this == "+":
480 min, max = 1, MAXREPEAT
481 elif this == "{":
482 if source.next == "}":
483 subpatternappend((LITERAL, ord(this)))
484 continue
485 here = source.tell()
486 min, max = 0, MAXREPEAT
487 lo = hi = ""
488 while source.next in DIGITS:
489 lo = lo + source.get()
490 if sourcematch(","):
491 while source.next in DIGITS:
492 hi = hi + sourceget()
493 else:
494 hi = lo
495 if not sourcematch("}"):
496 subpatternappend((LITERAL, ord(this)))
497 source.seek(here)
498 continue
499 if lo:
500 min = int(lo)
501 if hi:
502 max = int(hi)
503 if max < min:
504 raise error, "bad repeat interval"
505 else:
506 raise error, "not supported"
507 # figure out which item to repeat
508 if subpattern:
509 item = subpattern[-1:]
510 else:
511 item = None
512 if not item or (_len(item) == 1 and item[0][0] == AT):
513 raise error, "nothing to repeat"
514 if item[0][0] in REPEATCODES:
515 raise error, "multiple repeat"
516 if sourcematch("?"):
517 subpattern[-1] = (MIN_REPEAT, (min, max, item))
518 else:
519 subpattern[-1] = (MAX_REPEAT, (min, max, item))
521 elif this == ".":
522 subpatternappend((ANY, None))
524 elif this == "(":
525 group = 1
526 name = None
527 condgroup = None
528 if sourcematch("?"):
529 group = 0
530 # options
531 if sourcematch("P"):
532 # python extensions
533 if sourcematch("<"):
534 # named group: skip forward to end of name
535 name = ""
536 while 1:
537 char = sourceget()
538 if char is None:
539 raise error, "unterminated name"
540 if char == ">":
541 break
542 name = name + char
543 group = 1
544 if not isname(name):
545 raise error, "bad character in group name"
546 elif sourcematch("="):
547 # named backreference
548 name = ""
549 while 1:
550 char = sourceget()
551 if char is None:
552 raise error, "unterminated name"
553 if char == ")":
554 break
555 name = name + char
556 if not isname(name):
557 raise error, "bad character in group name"
558 gid = state.groupdict.get(name)
559 if gid is None:
560 raise error, "unknown group name"
561 subpatternappend((GROUPREF, gid))
562 continue
563 else:
564 char = sourceget()
565 if char is None:
566 raise error, "unexpected end of pattern"
567 raise error, "unknown specifier: ?P%s" % char
568 elif sourcematch(":"):
569 # non-capturing group
570 group = 2
571 elif sourcematch("#"):
572 # comment
573 while 1:
574 if source.next is None or source.next == ")":
575 break
576 sourceget()
577 if not sourcematch(")"):
578 raise error, "unbalanced parenthesis"
579 continue
580 elif source.next in ASSERTCHARS:
581 # lookahead assertions
582 char = sourceget()
583 dir = 1
584 if char == "<":
585 if source.next not in LOOKBEHINDASSERTCHARS:
586 raise error, "syntax error"
587 dir = -1 # lookbehind
588 char = sourceget()
589 p = _parse_sub(source, state)
590 if not sourcematch(")"):
591 raise error, "unbalanced parenthesis"
592 if char == "=":
593 subpatternappend((ASSERT, (dir, p)))
594 else:
595 subpatternappend((ASSERT_NOT, (dir, p)))
596 continue
597 elif sourcematch("("):
598 # conditional backreference group
599 condname = ""
600 while 1:
601 char = sourceget()
602 if char is None:
603 raise error, "unterminated name"
604 if char == ")":
605 break
606 condname = condname + char
607 group = 2
608 if isname(condname):
609 condgroup = state.groupdict.get(condname)
610 if condgroup is None:
611 raise error, "unknown group name"
612 else:
613 try:
614 condgroup = int(condname)
615 except ValueError:
616 raise error, "bad character in group name"
617 else:
618 # flags
619 if not source.next in FLAGS:
620 raise error, "unexpected end of pattern"
621 while source.next in FLAGS:
622 state.flags = state.flags | FLAGS[sourceget()]
623 if group:
624 # parse group contents
625 if group == 2:
626 # anonymous group
627 group = None
628 else:
629 group = state.opengroup(name)
630 if condgroup:
631 p = _parse_sub_cond(source, state, condgroup)
632 else:
633 p = _parse_sub(source, state)
634 if not sourcematch(")"):
635 raise error, "unbalanced parenthesis"
636 if group is not None:
637 state.closegroup(group)
638 subpatternappend((SUBPATTERN, (group, p)))
639 else:
640 while 1:
641 char = sourceget()
642 if char is None:
643 raise error, "unexpected end of pattern"
644 if char == ")":
645 break
646 raise error, "unknown extension"
648 elif this == "^":
649 subpatternappend((AT, AT_BEGINNING))
651 elif this == "$":
652 subpattern.append((AT, AT_END))
654 elif this and this[0] == "\\":
655 code = _escape(source, this, state)
656 subpatternappend(code)
658 else:
659 raise error, "parser error"
661 return subpattern
663 def parse(str, flags=0, pattern=None):
664 # parse 're' pattern into list of (opcode, argument) tuples
666 source = Tokenizer(str)
668 if pattern is None:
669 pattern = Pattern()
670 pattern.flags = flags
671 pattern.str = str
673 p = _parse_sub(source, pattern, 0)
675 tail = source.get()
676 if tail == ")":
677 raise error, "unbalanced parenthesis"
678 elif tail:
679 raise error, "bogus characters at end of regular expression"
681 if flags & SRE_FLAG_DEBUG:
682 p.dump()
684 if not (flags & SRE_FLAG_VERBOSE) and p.pattern.flags & SRE_FLAG_VERBOSE:
685 # the VERBOSE flag was switched on inside the pattern. to be
686 # on the safe side, we'll parse the whole thing again...
687 return parse(str, p.pattern.flags)
689 return p
691 def parse_template(source, pattern):
692 # parse 're' replacement string into list of literals and
693 # group references
694 s = Tokenizer(source)
695 sget = s.get
696 p = []
697 a = p.append
698 def literal(literal, p=p, pappend=a):
699 if p and p[-1][0] is LITERAL:
700 p[-1] = LITERAL, p[-1][1] + literal
701 else:
702 pappend((LITERAL, literal))
703 sep = source[:0]
704 if type(sep) is type(""):
705 makechar = chr
706 else:
707 makechar = unichr
708 while 1:
709 this = sget()
710 if this is None:
711 break # end of replacement string
712 if this and this[0] == "\\":
713 # group
714 c = this[1:2]
715 if c == "g":
716 name = ""
717 if s.match("<"):
718 while 1:
719 char = sget()
720 if char is None:
721 raise error, "unterminated group name"
722 if char == ">":
723 break
724 name = name + char
725 if not name:
726 raise error, "bad group name"
727 try:
728 index = int(name)
729 if index < 0:
730 raise error, "negative group number"
731 except ValueError:
732 if not isname(name):
733 raise error, "bad character in group name"
734 try:
735 index = pattern.groupindex[name]
736 except KeyError:
737 raise IndexError, "unknown group name"
738 a((MARK, index))
739 elif c == "0":
740 if s.next in OCTDIGITS:
741 this = this + sget()
742 if s.next in OCTDIGITS:
743 this = this + sget()
744 literal(makechar(int(this[1:], 8) & 0xff))
745 elif c in DIGITS:
746 isoctal = False
747 if s.next in DIGITS:
748 this = this + sget()
749 if (c in OCTDIGITS and this[2] in OCTDIGITS and
750 s.next in OCTDIGITS):
751 this = this + sget()
752 isoctal = True
753 literal(makechar(int(this[1:], 8) & 0xff))
754 if not isoctal:
755 a((MARK, int(this[1:])))
756 else:
757 try:
758 this = makechar(ESCAPES[this][1])
759 except KeyError:
760 pass
761 literal(this)
762 else:
763 literal(this)
764 # convert template to groups and literals lists
765 i = 0
766 groups = []
767 groupsappend = groups.append
768 literals = [None] * len(p)
769 for c, s in p:
770 if c is MARK:
771 groupsappend((i, s))
772 # literal[i] is already None
773 else:
774 literals[i] = s
775 i = i + 1
776 return groups, literals
778 def expand_template(template, match):
779 g = match.group
780 sep = match.string[:0]
781 groups, literals = template
782 literals = literals[:]
783 try:
784 for index, group in groups:
785 literals[index] = s = g(group)
786 if s is None:
787 raise error, "unmatched group"
788 except IndexError:
789 raise error, "invalid group reference"
790 return sep.join(literals)