path: root/Modules/_sre.c

/* -*- Mode: C; tab-width: 4 -*-
 *
 * Secret Labs' Regular Expression Engine
 * $Id$
 *
 * simple regular expression matching engine
 *
 * partial history:
 * 99-10-24 fl	created (based on the template matcher)
 * 99-11-13 fl	added categories, branching, and more (0.2)
 * 99-11-16 fl	some tweaks to compile on non-Windows platforms
 * 99-12-18 fl	non-literals, generic maximizing repeat (0.3)
 * 99-02-28 fl	tons of changes (not all to the better ;-) (0.4)
 * 99-03-06 fl	first alpha, sort of (0.5)
 * 99-03-14 fl	removed most compatibility stuff (0.6)
 * 99-05-10 fl	towards third alpha (0.8.2)
 * 99-05-13 fl	added experimental cursor stuff (0.8.3)
 * 99-05-27 fl	final bug hunt (0.8.4)
 *
 * Copyright (c) 1997-2000 by Secret Labs AB.  All rights reserved.
 *
 * This code can only be used for 1.6 alpha testing.  All other use
 * require explicit permission from Secret Labs AB.
 *
 * Portions of this engine have been developed in cooperation with
 * CNRI.  Hewlett-Packard provided funding for 1.6 integration and
 * other compatibility work.
 */

#ifndef SRE_RECURSIVE

char copyright[] = " SRE 0.8.4 Copyright (c) 1997-2000 by Secret Labs AB ";

#include "Python.h"

#include "sre.h"

#include "unicodeobject.h"

#if defined(HAVE_LIMITS_H)
#include <limits.h>
#else
#define INT_MAX 2147483647
#endif

#include <ctype.h>

/* defining this one enables tracing */
#undef DEBUG

#ifdef WIN32 /* FIXME: <fl> don't assume Windows == MSVC */
#pragma optimize("agtw", on) /* doesn't seem to make much difference... */
/* fastest possible local call under MSVC */
#define LOCAL(type) static __inline type __fastcall
#else
#define LOCAL(type) static type
#endif

/* error codes */
#define SRE_ERROR_ILLEGAL -1 /* illegal opcode */
#define SRE_ERROR_MEMORY -9 /* out of memory */

#ifdef	DEBUG
#define TRACE(v) printf v
#else
#define TRACE(v)
#endif
#define PTR(ptr) ((SRE_CHAR*) (ptr) - (SRE_CHAR*) state->beginning)

#define SRE_CODE unsigned short /* unsigned short or larger */

/* -------------------------------------------------------------------- */
/* search engine state */

/* unicode character predicates */
#define SRE_TO_LOWER(ch) Py_UNICODE_TOLOWER((Py_UNICODE)(ch))
#define SRE_IS_DIGIT(ch) Py_UNICODE_ISDIGIT((Py_UNICODE)(ch))
#define SRE_IS_SPACE(ch) Py_UNICODE_ISSPACE((Py_UNICODE)(ch))
#define SRE_IS_LINEBREAK(ch) ((ch) == '\n')
/* #define SRE_IS_LINEBREAK(ch) Py_UNICODE_ISLINEBREAK((Py_UNICODE)(ch)) */
#define SRE_IS_ALNUM(ch) ((ch) < 256 ? isalnum((ch)) : 0)
#define SRE_IS_WORD(ch) (SRE_IS_ALNUM((ch)) || (ch) == '_')

/* locale-specific character predicates */
#define SRE_LOC_TO_LOWER(ch) ((ch) < 256 ? tolower((ch)) : ch)
#define SRE_LOC_IS_DIGIT(ch) ((ch) < 256 ? isdigit((ch)) : 0)
#define SRE_LOC_IS_SPACE(ch) ((ch) < 256 ? isspace((ch)) : 0)
#define SRE_LOC_IS_LINEBREAK(ch) ((ch) == '\n')
#define SRE_LOC_IS_ALNUM(ch) ((ch) < 256 ? isalnum((ch)) : 0)
#define SRE_LOC_IS_WORD(ch) (SRE_LOC_IS_ALNUM((ch)) || (ch) == '_')

LOCAL(int)
sre_category(SRE_CODE category, unsigned int ch)
{
	switch (category) {
	case SRE_CATEGORY_DIGIT:
		return SRE_IS_DIGIT(ch);
	case SRE_CATEGORY_NOT_DIGIT:
		return !SRE_IS_DIGIT(ch);
	case SRE_CATEGORY_SPACE:
		return SRE_IS_SPACE(ch);
	case SRE_CATEGORY_NOT_SPACE:
		return !SRE_IS_SPACE(ch);
	case SRE_CATEGORY_WORD:
		return SRE_IS_WORD(ch);
	case SRE_CATEGORY_NOT_WORD:
		return !SRE_IS_WORD(ch);
	case SRE_CATEGORY_LINEBREAK:
		return SRE_IS_LINEBREAK(ch);
	case SRE_CATEGORY_NOT_LINEBREAK:
		return !SRE_IS_LINEBREAK(ch);
	case SRE_CATEGORY_LOC_DIGIT:
		return SRE_LOC_IS_DIGIT(ch);
	case SRE_CATEGORY_LOC_NOT_DIGIT:
		return !SRE_LOC_IS_DIGIT(ch);
	case SRE_CATEGORY_LOC_SPACE:
		return SRE_LOC_IS_SPACE(ch);
	case SRE_CATEGORY_LOC_NOT_SPACE:
		return !SRE_LOC_IS_SPACE(ch);
	case SRE_CATEGORY_LOC_WORD:
		return SRE_LOC_IS_WORD(ch);
	case SRE_CATEGORY_LOC_NOT_WORD:
		return !SRE_LOC_IS_WORD(ch);
	case SRE_CATEGORY_LOC_LINEBREAK:
		return SRE_LOC_IS_LINEBREAK(ch);
	case SRE_CATEGORY_LOC_NOT_LINEBREAK:
		return !SRE_LOC_IS_LINEBREAK(ch);
	}
	return 0;
}

/* helpers */

LOCAL(int)
_stack_free(SRE_STATE* state)
{
	if (state->stack) {
		TRACE(("release stack\n"));
		free(state->stack);
		state->stack = NULL;
	}
	state->stacksize = 0;
	return 0;
}

static int /* shouldn't be LOCAL */
_stack_extend(SRE_STATE* state, int lo, int hi)
{
	void** stack;
	int stacksize;

	/* grow the stack to a suitable size; we need at least lo entries,
	   at most hi entries.	if for some reason hi is lower than lo, lo
	   wins */

	stacksize = state->stacksize;

	if (stacksize == 0) {
		/* create new stack */
		stacksize = 512;
		if (stacksize < lo)
			stacksize = lo;
		else if (stacksize > hi)
			stacksize = hi;
		TRACE(("allocate stack %d\n", stacksize));
		stack = malloc(sizeof(void*) * stacksize);
	} else {
		/* grow the stack (typically by a factor of two) */
		while (stacksize < lo)
			stacksize = 2 * stacksize;
		/* FIXME: <fl> could trim size if it's larger than lo, and
		   much larger than hi */
		TRACE(("grow stack to %d\n", stacksize));
		stack = realloc(state->stack, sizeof(void*) * stacksize);
	}

	if (!stack) {
		_stack_free(state);
		return SRE_ERROR_MEMORY;
	}

	state->stack = stack;
	state->stacksize = stacksize;

	return 0;
}

/* generate 8-bit version */

#define SRE_CHAR unsigned char
#define SRE_AT sre_at
#define SRE_MEMBER sre_member
#define SRE_MATCH sre_match
#define SRE_SEARCH sre_search
#define SRE_RECURSIVE

#include "_sre.c"

#undef SRE_RECURSIVE
#undef SRE_SEARCH
#undef SRE_MATCH
#undef SRE_MEMBER
#undef SRE_AT
#undef SRE_CHAR

/* generate 16-bit unicode version */

#define SRE_CHAR Py_UNICODE
#define SRE_AT sre_uat
#define SRE_MEMBER sre_umember
#define SRE_MATCH sre_umatch
#define SRE_SEARCH sre_usearch

#endif /* SRE_RECURSIVE */

/* -------------------------------------------------------------------- */
/* String matching engine */

/* the following section is compiled twice, with different character
   settings */

LOCAL(int)
SRE_AT(SRE_STATE* state, SRE_CHAR* ptr, SRE_CODE at)
{
	/* check if pointer is at given position */

	int this, that;

	switch (at) {
	case SRE_AT_BEGINNING:
		return ((void*) ptr == state->beginning);
	case SRE_AT_BEGINNING_LINE:
		return ((void*) ptr == state->beginning ||
                SRE_IS_LINEBREAK((int) ptr[-1]));
	case SRE_AT_END:
		return ((void*) ptr == state->end);
	case SRE_AT_END_LINE:
		return ((void*) ptr == state->end ||
                SRE_IS_LINEBREAK((int) ptr[0]));
	case SRE_AT_BOUNDARY:
		if (state->beginning == state->end)
			return 0;
		that = ((void*) ptr > state->beginning) ?
			SRE_IS_WORD((int) ptr[-1]) : 0;
		this = ((void*) ptr < state->end) ?
			SRE_IS_WORD((int) ptr[0]) : 0;
		return this != that;
	case SRE_AT_NON_BOUNDARY:
		if (state->beginning == state->end)
			return 0;
		that = ((void*) ptr > state->beginning) ?
			SRE_IS_WORD((int) ptr[-1]) : 0;
		this = ((void*) ptr < state->end) ?
			SRE_IS_WORD((int) ptr[0]) : 0;
		return this == that;
	}

	return 0;
}

LOCAL(int)
SRE_MEMBER(SRE_CODE* set, SRE_CHAR ch)
{
	/* check if character is a member of the given set */

	int ok = 1;

	for (;;) {
		switch (*set++) {

		case SRE_OP_NEGATE:
			ok = !ok;
			break;

		case SRE_OP_FAILURE:
			return !ok;

		case SRE_OP_LITERAL:
			if (ch == (SRE_CHAR) set[0])
				return ok;
			set++;
			break;

		case SRE_OP_RANGE:
			if ((SRE_CHAR) set[0] <= ch && ch <= (SRE_CHAR) set[1])
				return ok;
			set += 2;
			break;

		case SRE_OP_CATEGORY:
			if (sre_category(set[0], (int) ch))
				return ok;
			set += 1;
			break;

		default:
			/* FIXME: internal error */
			return 0;
		}
	}
}

LOCAL(int)
SRE_MATCH(SRE_STATE* state, SRE_CODE* pattern)
{
	/* check if string matches the given pattern.  returns -1 for
	   error, 0 for failure, and 1 for success */

	SRE_CHAR* end = state->end;
	SRE_CHAR* ptr = state->ptr;
	int stacksize;
	int stackbase;
	int i, count;

    /* FIXME: this is one ugly hack */
    void* *mark = NULL;
    void* mark_data[64];

	for (;;) {

		switch (*pattern++) {

		case SRE_OP_FAILURE:
			/* immediate failure */
			TRACE(("%8d: failure\n", PTR(ptr)));
			goto failure;

		case SRE_OP_SUCCESS:
			/* end of pattern */
			TRACE(("%8d: success\n", PTR(ptr)));
			state->ptr = ptr;
			goto success;

		case SRE_OP_AT:
			/* match at given position */
			/* args: <at> */
			TRACE(("%8d: match at \\%c\n", PTR(ptr), *pattern));
			if (!SRE_AT(state, ptr, *pattern))
				goto failure;
			pattern++;
			break;

		case SRE_OP_CATEGORY:
			/* match at given category */
			/* args: <category> */
			TRACE(("%8d: category match at \\%c\n", PTR(ptr), *pattern));
			if (ptr >= end || !sre_category(pattern[0], ptr[0]))
				goto failure;
			pattern++;
            ptr++;
			break;

		case SRE_OP_LITERAL:
			/* match literal character */
			/* args: <code> */
			TRACE(("%8d: literal %c\n", PTR(ptr), (SRE_CHAR) *pattern));
			if (ptr >= end || *ptr != (SRE_CHAR) *pattern)
				goto failure;
			pattern++;
			ptr++;
			break;

		case SRE_OP_NOT_LITERAL:
			/* match anything that is not literal character */
			/* args: <code> */
			TRACE(("%8d: literal not %c\n", PTR(ptr), (SRE_CHAR) *pattern));
			if (ptr >= end || *ptr == (SRE_CHAR) *pattern)
				goto failure;
			pattern++;
			ptr++;
			break;

		case SRE_OP_ANY:
			/* match anything */
			TRACE(("%8d: any\n", PTR(ptr)));
			if (ptr >= end)
				goto failure;
			ptr++;
			break;

		case SRE_OP_IN:
			/* match set member (or non_member) */
			/* args: <skip> <set> */
			TRACE(("%8d: set %c\n", PTR(ptr), *ptr));
			if (ptr >= end || !SRE_MEMBER(pattern + 1, *ptr))
				goto failure;
			pattern += pattern[0];
			ptr++;
			break;

		case SRE_OP_GROUP:
			/* match backreference */
			TRACE(("%8d: group %d\n", PTR(ptr), pattern[0]));
			i = pattern[0];
			{
				/* FIXME: optimize! */
				SRE_CHAR* p = (SRE_CHAR*) state->mark[i+i];
				SRE_CHAR* e = (SRE_CHAR*) state->mark[i+i+1];
                TRACE(("%8d: group %p %p\n", PTR(ptr), p, e));
				if (!p || !e || e < p)
					goto failure;
				while (p < e) {
                    TRACE(("%8d: group test %c %c\n", PTR(ptr), *ptr, *p));
					if (ptr >= end || *ptr != *p)
						goto failure;
					p++; ptr++;
				}
			}
			pattern++;
			break;

		case SRE_OP_GROUP_IGNORE:
			/* match backreference */
			TRACE(("%8d: group ignore %d\n", PTR(ptr), pattern[0]));
			i = pattern[0];
			{
				/* FIXME: optimize! */
				SRE_CHAR* p = (SRE_CHAR*) state->mark[i+i];
				SRE_CHAR* e = (SRE_CHAR*) state->mark[i+i+1];
                TRACE(("%8d: group %p %p\n", PTR(ptr), p, e));
				if (!p || !e || e < p)
					goto failure;
				while (p < e) {
                    TRACE(("%8d: group test %c %c\n", PTR(ptr), *ptr, *p));
					if (ptr >= end || SRE_TO_LOWER(*ptr) != SRE_TO_LOWER(*p))
						goto failure;
					p++; ptr++;
				}
			}
			pattern++;
			break;

		case SRE_OP_LITERAL_IGNORE:
			TRACE(("%8d: literal lower(%c)\n", PTR(ptr), (SRE_CHAR) *pattern));
			if (ptr >= end || SRE_TO_LOWER(*ptr) != (SRE_CHAR) *pattern)
				goto failure;
			pattern++;
			ptr++;
			break;

		case SRE_OP_NOT_LITERAL_IGNORE:
			TRACE(("%8d: literal not lower(%c)\n", PTR(ptr),
				   (SRE_CHAR) *pattern));
			if (ptr >= end || SRE_TO_LOWER(*ptr) == (SRE_CHAR) *pattern)
				goto failure;
			pattern++;
			ptr++;
			break;

		case SRE_OP_IN_IGNORE:
			TRACE(("%8d: set lower(%c)\n", PTR(ptr), *ptr));
			if (ptr >= end
				|| !SRE_MEMBER(pattern+1, (SRE_CHAR) SRE_TO_LOWER(*ptr)))
				goto failure;
			pattern += pattern[0];
			ptr++;
			break;

		case SRE_OP_MARK:
			/* set mark */
			/* args: <mark> */
			TRACE(("%8d: set mark(%d)\n", PTR(ptr), pattern[0]));
            if (!mark) {
                mark = mark_data;
                memcpy(mark, state->mark, sizeof(state->mark));
            }
            state->mark[pattern[0]] = ptr;
			pattern++;
			break;

		case SRE_OP_JUMP:
			/* jump forward */
			/* args: <skip> */
			TRACE(("%8d: jump +%d\n", PTR(ptr), pattern[0]));
			pattern += pattern[0];
			break;

		case SRE_OP_CALL:
			/* match subpattern, without backtracking */
			/* args: <skip> <pattern> */
			TRACE(("%8d: match subpattern\n", PTR(ptr)));
			state->ptr = ptr;
			if (!SRE_MATCH(state, pattern + 1))
				goto failure;
			pattern += pattern[0];
			ptr = state->ptr;
			break;

		case SRE_OP_MAX_REPEAT_ONE:
			/* match repeated sequence (maximizing regexp) */
            /* this variant only works if the repeated item is exactly
			   one character wide, and we're not already collecting
			   backtracking points.  for other cases, use the
			   MAX_REPEAT operator instead */
			/* args: <skip> <min> <max> <step> */
			TRACE(("%8d: max repeat one {%d,%d}\n", PTR(ptr),
				   pattern[1], pattern[2]));

			count = 0;

			if (pattern[3] == SRE_OP_ANY) {
				/* repeated wildcard.  skip to the end of the target
				   string, and backtrack from there */
				/* FIXME: must look for line endings */
				if (ptr + pattern[1] > end)
					goto failure; /* cannot match */
				count = pattern[2];
				if (count > end - ptr)
					count = end - ptr;
				ptr += count;

			} else if (pattern[3] == SRE_OP_LITERAL) {
				/* repeated literal */
				SRE_CHAR chr = (SRE_CHAR) pattern[4];
				while (count < (int) pattern[2]) {
					if (ptr >= end || *ptr != chr)
						break;
					ptr++;
					count++;
				}

			} else if (pattern[3] == SRE_OP_LITERAL_IGNORE) {
				/* repeated literal */
				SRE_CHAR chr = (SRE_CHAR) pattern[4];
				while (count < (int) pattern[2]) {
					if (ptr >= end || (SRE_CHAR) SRE_TO_LOWER(*ptr) != chr)
						break;
					ptr++;
					count++;
				}

			} else if (pattern[3] == SRE_OP_NOT_LITERAL) {
				/* repeated non-literal */
				SRE_CHAR chr = (SRE_CHAR) pattern[4];
				while (count < (int) pattern[2]) {
					if (ptr >= end || *ptr == chr)
						break;
					ptr++;
					count++;
				}

			} else if (pattern[3] == SRE_OP_NOT_LITERAL_IGNORE) {
				/* repeated non-literal */
				SRE_CHAR chr = (SRE_CHAR) pattern[4];
				while (count < (int) pattern[2]) {
					if (ptr >= end || (SRE_CHAR) SRE_TO_LOWER(*ptr) == chr)
						break;
					ptr++;
					count++;
				}

			} else if (pattern[3] == SRE_OP_IN) {
				/* repeated set */
				while (count < (int) pattern[2]) {
					if (ptr >= end || !SRE_MEMBER(pattern + 5, *ptr))
						break;
					ptr++;
					count++;
				}

			} else {
				/* repeated single character pattern */
				state->ptr = ptr;
				while (count < (int) pattern[2]) {
					i = SRE_MATCH(state, pattern + 3);
					if (i < 0)
						goto failure;
					if (i == 0)
						break;
					count++;
				}
				state->ptr = ptr;
				ptr += count;
			}

			/* when we arrive here, count contains the number of
			   matches, and ptr points to the tail of the target
			   string.	check if the rest of the pattern matches, and
			   backtrack if not. */

			TRACE(("%8d: repeat %d found\n", PTR(ptr), count));

			if (count < (int) pattern[1])
				goto failure;

			if (pattern[pattern[0]] == SRE_OP_SUCCESS) {
				/* tail is empty.  we're finished */
				TRACE(("%8d: tail is empty\n", PTR(ptr)));
				state->ptr = ptr;
				goto success;

			} else if (pattern[pattern[0]] == SRE_OP_LITERAL) {
				/* tail starts with a literal. skip positions where
				   the rest of the pattern cannot possibly match */
				SRE_CHAR chr = (SRE_CHAR) pattern[pattern[0]+1];
				TRACE(("%8d: tail is literal %d\n", PTR(ptr), chr));
				for (;;) {
					TRACE(("%8d: scan for tail match\n", PTR(ptr)));
					while (count >= (int) pattern[1] &&
						   (ptr >= end || *ptr != chr)) {
						ptr--;
						count--;
					}
					TRACE(("%8d: check tail\n", PTR(ptr)));
					if (count < (int) pattern[1])
						break;
					state->ptr = ptr;
					i = SRE_MATCH(state, pattern + pattern[0]);
					if (i > 0) {
						TRACE(("%8d: repeat %d picked\n", PTR(ptr), count));
						goto success;
					}
					TRACE(("%8d: BACKTRACK\n", PTR(ptr)));
					ptr--;
					count--;
				}

			} else {
				/* general case */
				TRACE(("%8d: tail is pattern\n", PTR(ptr)));
				while (count >= (int) pattern[1]) {
					state->ptr = ptr;
					i = SRE_MATCH(state, pattern + pattern[0]);
					if (i > 0) {
						TRACE(("%8d: repeat %d picked\n", PTR(ptr), count));
						goto success;
					}
					TRACE(("%8d: BACKTRACK\n", PTR(ptr)));
					ptr--;
					count--;
				}
			}
			goto failure;

		case SRE_OP_MAX_REPEAT:
			/* match repeated sequence (maximizing regexp).	 repeated
			   group should end with a MAX_UNTIL code */

			TRACE(("%8d: max repeat %d %d\n", PTR(ptr),
				   pattern[1], pattern[2]));

			count = 0;
			state->ptr = ptr;

			/* FIXME: <fl> umm.	 what about matching the minimum
			   number of items before starting to collect backtracking
			   positions? */

			stackbase = state->stackbase;

			while (count < (int) pattern[2]) {
				/* store current position on the stack */
				TRACE(("%8d: push mark at index %d\n", PTR(ptr), count));
				if (stackbase + count >= state->stacksize) {
					i = _stack_extend(state, stackbase + count + 1,
									  stackbase + pattern[2]);
					if (i < 0)
						goto failure;
				}
				state->stack[stackbase + count] = ptr;
				/* check if we can match another item */
				state->stackbase += count + 1;
				i = SRE_MATCH(state, pattern + 3);
				state->stackbase = stackbase; /* rewind */
				if (i != 2)
					break;
				if (state->ptr == ptr) {
					/* if the match was successful but empty, set the
					   count to max and terminate the scanning loop */
					stacksize = count; /* actual size of stack */
					count = (int) pattern[2];
					goto check_tail; /* FIXME: <fl> eliminate goto */
				}
				count++;
				ptr = state->ptr;

			}

			stacksize = count; /* actual number of entries on the stack */

		  check_tail:

			/* when we get here, count is the number of matches,
			   stacksize is the number of match points on the stack
			   (usually same as count, but it might be smaller) and
			   ptr points to the tail. */

			if (count < (int) pattern[1])
				goto failure;

			/* make sure that rest of the expression matches.  if it
			   doesn't, backtrack */

			TRACE(("%8d: repeat %d found (stack size = %d)\n", PTR(ptr),
				   count, stacksize + 1));

			TRACE(("%8d: tail is pattern\n", PTR(ptr)));

			/* hope for the best */
			state->ptr = ptr;
			state->stackbase += stacksize + 1;
			i = SRE_MATCH(state, pattern + pattern[0]);
			state->stackbase = stackbase;
			if (i > 0) {
				TRACE(("%8d: repeat %d picked\n", PTR(ptr), count));
				goto success;
			}

			/* backtrack! */
			while (count >= (int) pattern[1]) {
				ptr = state->stack[stackbase + (count < stacksize ? count : stacksize)];
				state->ptr = ptr;
				count--;
				TRACE(("%8d: BACKTRACK\n", PTR(ptr)));
				state->stackbase += stacksize + 1;
				i = SRE_MATCH(state, pattern + pattern[0]);
				state->stackbase = stackbase;
				if (i > 0) {
					TRACE(("%8d: repeat %d picked\n", PTR(ptr), count));
					goto success;
				}
			}
			goto failure;

		case SRE_OP_MAX_UNTIL:
			/* match repeated sequence (maximizing regexp).	 repeated
			   group should end with a MAX_UNTIL code */

			TRACE(("%8d: max until\n", PTR(ptr)));
			state->ptr = ptr;
			goto success; /* always succeeds, for now... */

		case SRE_OP_MIN_REPEAT:
			/* match repeated sequence (minimizing regexp) */
            /* FIXME: HERE BE BUGS! */
			TRACE(("%8d: min repeat %d %d\n", PTR(ptr),
				   pattern[1], pattern[2]));
			count = 0;
			state->ptr = ptr;
			/* match minimum number of items */
			while (count < (int) pattern[1]) {
				i = SRE_MATCH(state, pattern + 3);
				if (i <= 0)
					goto failure;
				count++;
			}
			/* move forward until the tail matches. */
			while (count <= (int) pattern[2]) {
				ptr = state->ptr;
				i = SRE_MATCH(state, pattern + pattern[0]);
				if (i > 0) {
					TRACE(("%8d: repeat %d picked\n", PTR(ptr), count));
					goto success;
				}
				TRACE(("%8d: BACKTRACK\n", PTR(ptr)));
				state->ptr = ptr; /* backtrack */
				i = SRE_MATCH(state, pattern + 3);
				if (i <= 0)
					goto failure;
				count++;
			}
			goto failure;

		case SRE_OP_MIN_UNTIL:
			/* end of repeat group */
			TRACE(("%8d: min until\n", PTR(ptr)));
			state->ptr = ptr;
			goto success; /* always succeeds, for now... */

		case SRE_OP_BRANCH:
			/* match one of several subpatterns */
			/* format: <branch> <size> <head> ... <null> <tail> */
			TRACE(("%8d: branch\n", PTR(ptr)));
			while (*pattern) {
				if (pattern[1] != SRE_OP_LITERAL ||
					(ptr < end && *ptr == (SRE_CHAR) pattern[2])) {
					TRACE(("%8d: branch check\n", PTR(ptr)));
					state->ptr = ptr;
					i = SRE_MATCH(state, pattern + 1);
					if (i > 0) {
						TRACE(("%8d: branch succeeded\n", PTR(ptr)));
						goto success;
					}
				}
				pattern += *pattern;
			}
			TRACE(("%8d: branch failed\n", PTR(ptr)));
			goto failure;

		case SRE_OP_REPEAT:
			/* TEMPLATE: match repeated sequence (no backtracking) */
			/* format: <repeat> <skip> <min> <max> */
			TRACE(("%8d: repeat %d %d\n", PTR(ptr), pattern[1], pattern[2]));
			count = 0;
			state->ptr = ptr;
			while (count < (int) pattern[2]) {
				i = SRE_MATCH(state, pattern + 3);
				if (i <= 0)
					break;
				count++;
			}
			if (count <= (int) pattern[1])
				goto failure;
			TRACE(("%8d: repeat %d matches\n", PTR(ptr), count));
			pattern += pattern[0];
			ptr = state->ptr;
			break;

        default:
			return SRE_ERROR_ILLEGAL;
		}
	}

  failure:
    if (mark)
        memcpy(state->mark, mark, sizeof(state->mark));
    return 0;

  success:
    return 1;
}

LOCAL(int)
SRE_SEARCH(SRE_STATE* state, SRE_CODE* pattern)
{
	SRE_CHAR* ptr = state->start;
	SRE_CHAR* end = state->end;
	int status = 0;

	/* FIXME: <fl> add IGNORE cases (or implement full ASSERT support?	*/

	if (pattern[0] == SRE_OP_LITERAL) {
		/* pattern starts with a literal */
		SRE_CHAR chr = (SRE_CHAR) pattern[1];
		for (;;) {
			while (ptr < end && *ptr != chr)
				ptr++;
			if (ptr == end)
				return 0;
			TRACE(("%8d: search found literal\n", PTR(ptr)));
			state->start = ptr;
			state->ptr = ++ptr;
			status = SRE_MATCH(state, pattern + 2);
			if (status != 0)
				break;
		}

	} else if (pattern[0] == SRE_OP_IN) {
		/* pattern starts with a set */
		for (;;) {
			/* format: <in> <skip> <data> */
			while (ptr < end && !SRE_MEMBER(pattern + 2, *ptr))
				ptr++;
			if (ptr == end)
				return 0;
			TRACE(("%8d: search found set\n", PTR(ptr)));
			state->start = ptr;
			state->ptr = ++ptr;
			status = SRE_MATCH(state, pattern + pattern[1] + 1);
			if (status != 0)
				break;
		}

	} else
		while (ptr <= end) {
			TRACE(("%8d: search\n", PTR(ptr))); 
			state->start = state->ptr = ptr++;
			status = SRE_MATCH(state, pattern);
			if (status != 0)
				break;
		}

	return status;
}

#ifndef SRE_RECURSIVE

/* -------------------------------------------------------------------- */
/* factories and destructors */

/* see sre.h for object declarations */

staticforward PyTypeObject Pattern_Type;
staticforward PyTypeObject Match_Type;
staticforward PyTypeObject Cursor_Type;

static PyObject *
_compile(PyObject* self_, PyObject* args)
{
	/* "compile" pattern descriptor to pattern object */

	PatternObject* self;

	PyObject* pattern;
    int flags = 0;
	PyObject* code;
	int groups = 0;
	PyObject* groupindex = NULL;
	if (!PyArg_ParseTuple(args, "OiO!|iO", &pattern, &flags,
                          &PyString_Type, &code,
                          &groups, &groupindex))
		return NULL;

	self = PyObject_NEW(PatternObject, &Pattern_Type);
	if (self == NULL)

		return NULL;

	Py_INCREF(pattern);
	self->pattern = pattern;

    self->flags = flags;

	Py_INCREF(code);
	self->code = code;

	self->groups = groups;

	Py_XINCREF(groupindex);
	self->groupindex = groupindex;

	return (PyObject*) self;
}

static PyObject *
_getcodesize(PyObject* self_, PyObject* args)
{
	return Py_BuildValue("i", sizeof(SRE_CODE));
}

LOCAL(PyObject*)
_setup(SRE_STATE* state, PyObject* args)
{
	/* prepare state object */

	PyBufferProcs *buffer;
	int i, count;
	void* ptr;

	PyObject* string;
	int start = 0;
	int end = INT_MAX;
	if (!PyArg_ParseTuple(args, "O|ii", &string, &start, &end))
		return NULL;

	/* get pointer to string buffer */
	buffer = string->ob_type->tp_as_buffer;
	if (!buffer || !buffer->bf_getreadbuffer || !buffer->bf_getsegcount ||
		buffer->bf_getsegcount(string, NULL) != 1) {
		PyErr_SetString(PyExc_TypeError, "expected read-only buffer");
		return NULL;
	}

	/* determine buffer size */
	count = buffer->bf_getreadbuffer(string, 0, &ptr);
	if (count < 0) {
		/* sanity check */
		PyErr_SetString(PyExc_TypeError, "buffer has negative size");
		return NULL;
	}

	/* determine character size */
	state->charsize = (PyUnicode_Check(string) ? sizeof(Py_UNICODE) : 1);

	count /= state->charsize;

	/* adjust boundaries */
	if (start < 0)
		start = 0;
	else if (start > count)
		start = count;

	if (end < 0)
		end = 0;
	else if (end > count)
		end = count;

	state->beginning = ptr;

	state->start = (void*) ((char*) ptr + start * state->charsize);
	state->end = (void*) ((char*) ptr + end * state->charsize);

	/* FIXME: dynamic! */
	for (i = 0; i < 64; i++)
		state->mark[i] = NULL;

	state->stack = NULL;
	state->stackbase = 0;
	state->stacksize = 0;

	return string;
}

static PyObject*
_pattern_new_match(PatternObject* pattern, SRE_STATE* state,
                   PyObject* string, int status)
{
	/* create match object (from state object) */

	MatchObject* match;
	int i, j;

	TRACE(("status = %d\n", status));

	if (status > 0) {

		/* create match object (with room for extra group marks) */
		match = PyObject_NEW_VAR(MatchObject, &Match_Type, 2*pattern->groups);
		if (match == NULL)
			return NULL;

		Py_INCREF(pattern);
		match->pattern = pattern;

		Py_INCREF(string);
		match->string = string;

		match->groups = pattern->groups+1;

		/* group zero */
		match->mark[0] = ((char*) state->start -
						  (char*) state->beginning) / state->charsize;
		match->mark[1] = ((char*) state->ptr -
						  (char*) state->beginning) / state->charsize;

		/* fill in the rest of the groups */
		for (i = j = 0; i < pattern->groups; i++, j+=2)
			if (state->mark[j] != NULL && state->mark[j+1] != NULL) {
				match->mark[j+2] = ((char*) state->mark[j] -
									(char*) state->beginning) / state->charsize;
				match->mark[j+3] = ((char*) state->mark[j+1] -
									(char*) state->beginning) / state->charsize;
			} else
				match->mark[j+2] = match->mark[j+3] = -1; /* undefined */

		return (PyObject*) match;

	} else if (status < 0) {

		/* internal error */
		PyErr_SetString(
			PyExc_RuntimeError, "internal error in regular expression engine"
			);
		return NULL;

	}

	Py_INCREF(Py_None);
	return Py_None;
}

static PyObject*
_pattern_cursor(PyObject* pattern, PyObject* args)
{
	/* create search state object */

	CursorObject* self;
    PyObject* string;

    /* create match object (with room for extra group marks) */
    self = PyObject_NEW(CursorObject, &Cursor_Type);
    if (self == NULL)
        return NULL;

    string = _setup(&self->state, args);
    if (!string) {
        /* FIXME: dealloc cursor object */
        return NULL;
    }

    Py_INCREF(pattern);
    self->pattern = pattern;

    Py_INCREF(string);
    self->string = string;

	return (PyObject*) self;
}

static void
_pattern_dealloc(PatternObject* self)
{
	Py_XDECREF(self->code);
	Py_XDECREF(self->pattern);
	Py_XDECREF(self->groupindex);
	PyMem_DEL(self);
}

static PyObject*
_pattern_match(PatternObject* self, PyObject* args)
{
	SRE_STATE state;
	PyObject* string;
	int status;

	string = _setup(&state, args);
	if (!string)
		return NULL;

	state.ptr = state.start;

	if (state.charsize == 1) {
		status = sre_match(&state, PatternObject_GetCode(self));
	} else {
		status = sre_umatch(&state, PatternObject_GetCode(self));
	}

	_stack_free(&state);

	return _pattern_new_match(self, &state, string, status);
}

static PyObject*
_pattern_search(PatternObject* self, PyObject* args)
{
	SRE_STATE state;
	PyObject* string;
	int status;

	string = _setup(&state, args);
	if (!string)
		return NULL;

	if (state.charsize == 1) {
		status = sre_search(&state, PatternObject_GetCode(self));
	} else {
		status = sre_usearch(&state, PatternObject_GetCode(self));
	}

	_stack_free(&state);

	return _pattern_new_match(self, &state, string, status);
}

static PyObject*
call(char* function, PyObject* args)
{
    PyObject* name;
    PyObject* module;
    PyObject* func;
    PyObject* result;

    name = PyString_FromString("sre");
    if (!name)
        return NULL;
    module = PyImport_Import(name);
    Py_DECREF(name);
    if (!module)
        return NULL;
    func = PyObject_GetAttrString(module, function);
    Py_DECREF(module);
    if (!func)
        return NULL;
    result = PyObject_CallObject(func, args);
    Py_DECREF(func);
    Py_DECREF(args);
    return result;
}

static PyObject*
_pattern_sub(PatternObject* self, PyObject* args)
{
	PyObject* template;
	PyObject* string;
    PyObject* count;
	if (!PyArg_ParseTuple(args, "OOO", &template, &string, &count))
		return NULL;

    /* delegate to Python code */
    return call("_sub", Py_BuildValue("OOOO", self, template, string, count));
}

static PyObject*
_pattern_subn(PatternObject* self, PyObject* args)
{
	PyObject* template;
	PyObject* string;
    PyObject* count;
	if (!PyArg_ParseTuple(args, "OOO", &template, &string, &count))
		return NULL;

    /* delegate to Python code */
    return call("_subn", Py_BuildValue("OOOO", self, template, string, count));
}

static PyObject*
_pattern_split(PatternObject* self, PyObject* args)
{
	PyObject* string;
    PyObject* maxsplit;
	if (!PyArg_ParseTuple(args, "OO", &string, &maxsplit))
		return NULL;

    /* delegate to Python code */
    return call("_split", Py_BuildValue("OOO", self, string, maxsplit));
}

static PyObject*
_pattern_findall(PatternObject* self, PyObject* args)
{
	SRE_STATE state;
	PyObject* string;
	PyObject* list;
	int status;

	string = _setup(&state, args);
	if (!string)
		return NULL;

	list = PyList_New(0);

	while (state.start < state.end) {

		PyObject* item;
		
		state.ptr = state.start;

		if (state.charsize == 1) {
			status = sre_match(&state, PatternObject_GetCode(self));
		} else {
			status = sre_umatch(&state, PatternObject_GetCode(self));
		}

		if (status >= 0) {

			if (status == 0)
				state.ptr = (void*) ((char*) state.start + 1);

            /* FIXME: if one group is defined, slice that group
               instead.  if multiple groups are defined, add tuple
               containing all slices */

			item = PySequence_GetSlice(
				string,
				((char*) state.start - (char*) state.beginning),
				((char*) state.ptr - (char*) state.beginning));
			if (!item)
				goto error;
			if (PyList_Append(list, item) < 0)
				goto error;

			state.start = state.ptr;

		} else {

			/* internal error */
			PyErr_SetString(
				PyExc_RuntimeError,
				"internal error in regular expression engine"
				);
			goto error;

		}
	}

	_stack_free(&state);

	return list;

error:
	_stack_free(&state);
	return NULL;
	
}

static PyMethodDef _pattern_methods[] = {
	{"match", (PyCFunction) _pattern_match, 1},
	{"search", (PyCFunction) _pattern_search, 1},
	{"sub", (PyCFunction) _pattern_sub, 1},
	{"subn", (PyCFunction) _pattern_subn, 1},
	{"split", (PyCFunction) _pattern_split, 1},
	{"findall", (PyCFunction) _pattern_findall, 1},
    /* experimental */
	{"cursor", (PyCFunction) _pattern_cursor, 1},
	{NULL, NULL}
};

static PyObject*  
_pattern_getattr(PatternObject* self, char* name)
{
    PyObject* res;

	res = Py_FindMethod(_pattern_methods, (PyObject*) self, name);

	if (res)
		return res;

	PyErr_Clear();

    /* attributes */
	if (!strcmp(name, "pattern")) {
        Py_INCREF(self->pattern);
		return self->pattern;
    }

    if (!strcmp(name, "flags"))
		return Py_BuildValue("i", self->flags);

	if (!strcmp(name, "groupindex") && self->groupindex) {
        Py_INCREF(self->groupindex);
		return self->groupindex;
    }

	PyErr_SetString(PyExc_AttributeError, name);
	return NULL;
}

statichere PyTypeObject Pattern_Type = {
	PyObject_HEAD_INIT(NULL)
	0, "Pattern", sizeof(PatternObject), 0,
	(destructor)_pattern_dealloc, /*tp_dealloc*/
	0, /*tp_print*/
	(getattrfunc)_pattern_getattr, /*tp_getattr*/
};

/* -------------------------------------------------------------------- */
/* match methods */

static void
_match_dealloc(MatchObject* self)
{
	Py_XDECREF(self->string);
	Py_DECREF(self->pattern);
	PyMem_DEL(self);
}

static PyObject*
getslice_by_index(MatchObject* self, int index)
{
	if (index < 0 || index >= self->groups) {
		/* raise IndexError if we were given a bad group number */
		PyErr_SetString(
			PyExc_IndexError,
			"no such group"
			);
		return NULL;
	}

	if (self->string == Py_None || self->mark[index+index] < 0) {
		/* return None if the string or group is undefined */
		Py_INCREF(Py_None);
		return Py_None;
	}

	return PySequence_GetSlice(
		self->string, self->mark[index+index], self->mark[index+index+1]
		);
}

static PyObject*
getslice(MatchObject* self, PyObject* index)
{
	if (!PyInt_Check(index) && self->pattern->groupindex != NULL) {
		/* FIXME: resource leak? */
		index = PyObject_GetItem(self->pattern->groupindex, index);
		if (!index)
			return NULL;
	}

	if (PyInt_Check(index))
		return getslice_by_index(self, (int) PyInt_AS_LONG(index));

	return getslice_by_index(self, -1); /* signal error */
}

static PyObject*
_match_group(MatchObject* self, PyObject* args)
{
	PyObject* result;
	int i, size;

	size = PyTuple_GET_SIZE(args);

	switch (size) {
	case 0:
		result = getslice(self, Py_False); /* force error */
		break;
	case 1:
		result = getslice(self, PyTuple_GET_ITEM(args, 0));
		break;
	default:
		/* fetch multiple items */
		result = PyTuple_New(size);
		if (!result)
			return NULL;
		for (i = 0; i < size; i++) {
			PyObject* item = getslice(self, PyTuple_GET_ITEM(args, i));
			if (!item) {
				Py_DECREF(result);
				return NULL;
			}
			PyTuple_SET_ITEM(result, i, item);
		}
		break;
	}
	return result;
}

static PyObject*
_match_groups(MatchObject* self, PyObject* args)
{
	PyObject* result;
	int index;

    /* FIXME: <fl> handle default value! */

	result = PyTuple_New(self->groups-1);
	if (!result)
		return NULL;

	for (index = 1; index < self->groups; index++) {
		PyObject* item;
		/* FIXME: <fl> handle default! */
		item = getslice_by_index(self, index);
		if (!item) {
			Py_DECREF(result);
			return NULL;
		}
		PyTuple_SET_ITEM(result, index-1, item);
	}

	return result;
}

static PyObject*
_match_groupdict(MatchObject* self, PyObject* args)
{
	PyObject* result;
	PyObject* keys;
	int index;

    /* FIXME: <fl> handle default value! */

	result = PyDict_New();
	if (!result)
		return NULL;
	if (!self->pattern->groupindex)
		return result;

	keys = PyMapping_Keys(self->pattern->groupindex);
	if (!keys)
		return NULL;

	for (index = 0; index < PySequence_Length(keys); index++) {
		PyObject* key;
		PyObject* item;
		key = PySequence_GetItem(keys, index);
		if (!key) {
			Py_DECREF(keys);
			Py_DECREF(result);
			return NULL;
		}
		item = getslice(self, key);
		if (!item) {
			Py_DECREF(key);
			Py_DECREF(keys);
			Py_DECREF(result);
			return NULL;
		}
		/* FIXME: <fl> this can fail, right? */
		PyDict_SetItem(result, key, item);
	}

	Py_DECREF(keys);

	return result;
}

static PyObject*
_match_start(MatchObject* self, PyObject* args)
{
	int index = 0;
	if (!PyArg_ParseTuple(args, "|i", &index))
		return NULL;

	if (index < 0 || index >= self->groups) {
		PyErr_SetString(
			PyExc_IndexError,
			"no such group"
			);
		return NULL;
	}

	if (self->mark[index*2] < 0) {
		Py_INCREF(Py_None);
		return Py_None;
	}

	return Py_BuildValue("i", self->mark[index*2]);
}

static PyObject*
_match_end(MatchObject* self, PyObject* args)
{
	int index = 0;
	if (!PyArg_ParseTuple(args, "|i", &index))
		return NULL;

	if (index < 0 || index >= self->groups) {
		PyErr_SetString(
			PyExc_IndexError,
			"no such group"
			);
		return NULL;
	}

	if (self->mark[index*2] < 0) {
		Py_INCREF(Py_None);
		return Py_None;
	}

	return Py_BuildValue("i", self->mark[index*2+1]);
}

static PyObject*
_match_span(MatchObject* self, PyObject* args)
{
	int index = 0;
	if (!PyArg_ParseTuple(args, "|i", &index))
		return NULL;

	if (index < 0 || index >= self->groups) {
		PyErr_SetString(
			PyExc_IndexError,
			"no such group"
			);
		return NULL;
	}

	if (self->mark[index*2] < 0) {
		Py_INCREF(Py_None);
		Py_INCREF(Py_None);
        return Py_BuildValue("OO", Py_None, Py_None);
	}

	return Py_BuildValue("ii", self->mark[index*2], self->mark[index*2+1]);
}

static PyMethodDef _match_methods[] = {
	{"group", (PyCFunction) _match_group, 1},
	{"start", (PyCFunction) _match_start, 1},
	{"end", (PyCFunction) _match_end, 1},
	{"span", (PyCFunction) _match_span, 1},
	{"groups", (PyCFunction) _match_groups, 1},
	{"groupdict", (PyCFunction) _match_groupdict, 1},
	{NULL, NULL}
};

static PyObject*  
_match_getattr(MatchObject* self, char* name)
{
	PyObject* res;

	res = Py_FindMethod(_match_methods, (PyObject*) self, name);
	if (res)
		return res;

	PyErr_Clear();

	/* attributes */
	if (!strcmp(name, "string")) {
        Py_INCREF(self->string);
		return self->string;
    }

	if (!strcmp(name, "re")) {
        Py_INCREF(self->pattern);
		return (PyObject*) self->pattern;
    }

	if (!strcmp(name, "pos"))
		return Py_BuildValue("i", 0); /* FIXME */

	if (!strcmp(name, "endpos"))
		return Py_BuildValue("i", 0); /* FIXME */

	PyErr_SetString(PyExc_AttributeError, name);
	return NULL;
}

/* FIXME: implement setattr("string", None) as a special case (to
   detach the associated string, if any */

statichere PyTypeObject Match_Type = {
	PyObject_HEAD_INIT(NULL)
	0, "Match",
	sizeof(MatchObject), /* size of basic object */
	sizeof(int), /* space for group item */
	(destructor)_match_dealloc, /*tp_dealloc*/
	0, /*tp_print*/
	(getattrfunc)_match_getattr, /*tp_getattr*/
};

/* -------------------------------------------------------------------- */
/* cursor methods (experimental) */

static void
_cursor_dealloc(CursorObject* self)
{
	_stack_free(&self->state);
    Py_DECREF(self->string);
    Py_DECREF(self->pattern);
	PyMem_DEL(self);
}

static PyObject*
_cursor_match(CursorObject* self, PyObject* args)
{
    SRE_STATE* state = &self->state;
    PyObject* match;
    int status;

    state->ptr = state->start;

    if (state->charsize == 1) {
        status = sre_match(state, PatternObject_GetCode(self->pattern));
    } else {
        status = sre_umatch(state, PatternObject_GetCode(self->pattern));
    }

    match = _pattern_new_match((PatternObject*) self->pattern,
                               state, self->string, status);

    if (status >= 0)
        state->start = state->ptr;
    else
        state->start = (char*) state->ptr + state->charsize;

    return match;
}


static PyObject*
_cursor_search(CursorObject* self, PyObject* args)
{
    SRE_STATE* state = &self->state;
    PyObject* match;
    int status;

    state->ptr = state->start;

    if (state->charsize == 1) {
        status = sre_search(state, PatternObject_GetCode(self->pattern));
    } else {
        status = sre_usearch(state, PatternObject_GetCode(self->pattern));
    }

    match = _pattern_new_match((PatternObject*) self->pattern,
                               state, self->string, status);

    if (status >= 0)
        state->start = state->ptr;

    return match;
}

static PyMethodDef _cursor_methods[] = {
	{"match", (PyCFunction) _cursor_match, 0},
	{"search", (PyCFunction) _cursor_search, 0},
	{NULL, NULL}
};

static PyObject*  
_cursor_getattr(CursorObject* self, char* name)
{
	PyObject* res;

	res = Py_FindMethod(_cursor_methods, (PyObject*) self, name);
	if (res)
		return res;

	PyErr_Clear();

	/* attributes */
	if (!strcmp(name, "pattern")) {
        Py_INCREF(self->pattern);
		return self->pattern;
    }

	PyErr_SetString(PyExc_AttributeError, name);
	return NULL;
}

statichere PyTypeObject Cursor_Type = {
	PyObject_HEAD_INIT(NULL)
	0, "Cursor",
	sizeof(CursorObject), /* size of basic object */
	0,
	(destructor)_cursor_dealloc, /*tp_dealloc*/
	0, /*tp_print*/
	(getattrfunc)_cursor_getattr, /*tp_getattr*/
};

static PyMethodDef _functions[] = {
	{"compile", _compile, 1},
	{"getcodesize", _getcodesize, 1},
	{NULL, NULL}
};

void
#ifdef WIN32
__declspec(dllexport)
#endif
init_sre()
{
	/* Patch object types */
	Pattern_Type.ob_type = Match_Type.ob_type =
        Cursor_Type.ob_type = &PyType_Type;

	Py_InitModule("_sre", _functions);
}

#endif