/*
 * re.c - compile regular expressions.
 */

/* 
 * Copyright (C) 1991-2002 the Free Software Foundation, Inc.
 * 
 * This file is part of GAWK, the GNU implementation of the
 * AWK Programming Language.
 * 
 * GAWK is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * GAWK is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA
 */

#include "awk.h"

static reg_syntax_t syn;

/* make_regexp --- generate compiled regular expressions */

Regexp *
make_regexp(char *s, size_t len, int ignorecase, int dfa)
{
	Regexp *rp;
	const char *rerr;
	char *src = s;
	char *temp;
	char *end = s + len;
	register char *dest;
	register int c, c2;
#ifdef MBS_SUPPORT
	/* The number of bytes in the current multbyte character.
	   It is 0, when the current character is a singlebyte character.  */
	size_t is_multibyte = 0;
	mbstate_t mbs;
	if (MB_CUR_MAX > 1)
		memset(&mbs, 0, sizeof(mbstate_t)); /* Initialize.  */
#endif

	/* Handle escaped characters first. */

	/*
	 * Build a copy of the string (in dest) with the
	 * escaped characters translated, and generate the regex
	 * from that.  
	 */
	emalloc(dest, char *, len + 2, "make_regexp");
	temp = dest;

	while (src < end) {
#ifdef MBS_SUPPORT
		if (MB_CUR_MAX > 1 && !is_multibyte) {
			/* The previous byte is a singlebyte character, or last byte
			   of a multibyte character.  We check the next character.  */
			is_multibyte = mbrlen(src, end - src, &mbs);
			if ((is_multibyte == 1) || (is_multibyte == (size_t) -1)
				|| (is_multibyte == (size_t) -2 || (is_multibyte == 0))) {
				/* We treat it as a singlebyte character.  */
				is_multibyte = 0;
			}
		}
#endif

#ifdef MBS_SUPPORT
		/* We skip multibyte character, since it must not be a special
		   character.  */
		if ((MB_CUR_MAX == 1 || !is_multibyte) && (*src == '\\')) {
#else
		if (*src == '\\') {
#endif
			c = *++src;
			switch (c) {
			case 'a':
			case 'b':
			case 'f':
			case 'n':
			case 'r':
			case 't':
			case 'v':
			case 'x':
			case '0':
			case '1':
			case '2':
			case '3':
			case '4':
			case '5':
			case '6':
			case '7':
				c2 = parse_escape(&src);
				if (c2 < 0)
					cant_happen();
				/*
				 * Unix awk treats octal (and hex?) chars
				 * literally in re's, so escape regexp
				 * metacharacters.
				 */
				if (do_traditional && ! do_posix && (ISDIGIT(c) || c == 'x')
				    && strchr("()|*+?.^$\\[]", c2) != NULL)
					*dest++ = '\\';
				*dest++ = (char) c2;
				break;
			case '8':
			case '9':	/* a\9b not valid */
				*dest++ = c;
				src++;
				break;
			case 'y':	/* normally \b */
				/* gnu regex op */
				if (! do_traditional) {
					*dest++ = '\\';
					*dest++ = 'b';
					src++;
					break;
				}
				/* else, fall through */
			default:
				*dest++ = '\\';
				*dest++ = (char) c;
				src++;
				break;
			} /* switch */
		} else
			*dest++ = *src++;	/* not '\\' */
#ifdef MBS_SUPPORT
		if (MB_CUR_MAX > 1 && is_multibyte)
			is_multibyte--;
#endif
	} /* for */

	*dest = '\0' ;	/* Only necessary if we print dest ? */
	emalloc(rp, Regexp *, sizeof(*rp), "make_regexp");
	memset((char *) rp, 0, sizeof(*rp));
	rp->pat.allocated = 0;	/* regex will allocate the buffer */
	emalloc(rp->pat.fastmap, char *, 256, "make_regexp");

	if (ignorecase)
		rp->pat.translate = casetable;
	else
		rp->pat.translate = NULL;
	len = dest - temp;
	if ((rerr = re_compile_pattern(temp, len, &(rp->pat))) != NULL)
		fatal("%s: /%s/", gettext(rerr), temp);

	/* gack. this must be done *after* re_compile_pattern */
	rp->pat.newline_anchor = FALSE; /* don't get \n in middle of string */
	if (dfa && ! ignorecase) {
		dfacomp(temp, len, &(rp->dfareg), TRUE);
		rp->dfa = TRUE;
	} else
		rp->dfa = FALSE;

	free(temp);
	return rp;
}

/* research --- do a regexp search. use dfa if possible */

int
research(Regexp *rp, register char *str, int start,
	register size_t len, int need_start)
{
	char *ret = str;
	int try_backref;

	/*
	 * Always do dfa search if can; if it fails, then even if
	 * need_start is true, we won't bother with the regex search.
	 */
	if (rp->dfa) {
		char save;
		int count = 0;

		/*
		 * dfa likes to stick a '\n' right after the matched
		 * text.  So we just save and restore the character.
		 */
		save = str[start+len];
		ret = dfaexec(&(rp->dfareg), str+start, str+start+len, TRUE,
					&count, &try_backref);
		str[start+len] = save;
	}
	if (ret) {
		if (need_start || rp->dfa == FALSE || try_backref) {
			int res = re_search(&(rp->pat), str, start+len,
					start, len, &(rp->regs));

			/*
			 * A return of -2 indicates that a heuristic in
			 * regex decided it might allocate too much memory
			 * on the C stack. This doesn't apply to gawk, which
			 * uses REGEX_MALLOC. This is dealt with by the
			 * assignment to re_max_failures in resetup().
			 * Naetheless, we keep this code here as a fallback.
			 */
			if (res == -2) {
				/* the 10 here is arbitrary */
				fatal(_("regex match failed, not enough memory to match string \"%.*s%s\""),
						len > 10 ? 10 : len, str + start,
						len > 10 ? "..." : "");
			}
			return res;
		} else
			return 1;
	} else
		return -1;
}

/* refree --- free up the dynamic memory used by a compiled regexp */

void
refree(Regexp *rp)
{
	free(rp->pat.buffer);
	free(rp->pat.fastmap);
	if (rp->regs.start)
		free(rp->regs.start);
	if (rp->regs.end)
		free(rp->regs.end);
	if (rp->dfa)
		dfafree(&(rp->dfareg));
	free(rp);
}

/* dfaerror --- print an error message for the dfa routines */

void
dfaerror(const char *s)
{
	fatal("%s", s);
}

/* re_update --- recompile a dynamic regexp */

Regexp *
re_update(NODE *t)
{
	NODE *t1;

	if ((t->re_flags & CASE) == IGNORECASE) {
		if ((t->re_flags & CONST) != 0) {
			assert(t->type == Node_regex);
			return t->re_reg;
		}
		t1 = force_string(tree_eval(t->re_exp));
		if (t->re_text != NULL) {
			if (cmp_nodes(t->re_text, t1) == 0) {
				free_temp(t1);
				return t->re_reg;
			}
			unref(t->re_text);
		}
		t->re_text = dupnode(t1);
		free_temp(t1);
	}
	if (t->re_reg != NULL)
		refree(t->re_reg);
	if (t->re_cnt > 0)
		t->re_cnt++;
	if (t->re_cnt > 10)
		t->re_cnt = 0;
	if (t->re_text == NULL || (t->re_flags & CASE) != IGNORECASE) {
		t1 = force_string(tree_eval(t->re_exp));
		unref(t->re_text);
		t->re_text = dupnode(t1);
		free_temp(t1);
	}
	t->re_reg = make_regexp(t->re_text->stptr, t->re_text->stlen,
				IGNORECASE, t->re_cnt);
	t->re_flags &= ~CASE;
	t->re_flags |= IGNORECASE;
	return t->re_reg;
}

/* resetup --- choose what kind of regexps we match */

void
resetup()
{
	if (do_posix)
		syn = RE_SYNTAX_POSIX_AWK;	/* strict POSIX re's */
	else if (do_traditional)
		syn = RE_SYNTAX_AWK;		/* traditional Unix awk re's */
	else
		syn = RE_SYNTAX_GNU_AWK;	/* POSIX re's + GNU ops */

	/*
	 * Interval expressions are off by default, since it's likely to
	 * break too many old programs to have them on.
	 */
	if (do_intervals)
		syn |= RE_INTERVALS;

	(void) re_set_syntax(syn);
	dfasyntax(syn, FALSE, '\n');
}

/* avoid_dfa --- FIXME: temporary kludge function until we have a new dfa.c */

int
avoid_dfa(NODE *re, char *str, size_t len)
{
	char *restr;
	int relen;
	int anchor, i;
	char *end;

	if ((re->re_flags & CONST) != 0) {
		restr = re->re_exp->stptr;
		relen = re->re_exp->stlen;
	} else {
		restr = re->re_text->stptr;
		relen = re->re_text->stlen;
	}

	for (anchor = FALSE, i = 0; i < relen; i++) {
		if (restr[i] == '^' || restr[i] == '$') {
			anchor = TRUE;
			break;
		}
	}
	if (! anchor)
		return FALSE;

	for (end = str + len; str < end; str++)
		if (*str == '\n')
			return TRUE;

	return FALSE;
}

/* reisstring --- return TRUE if the RE match is a simple string match */

int
reisstring(char *text, size_t len, Regexp *re, char *buf)
{
	static char metas[] = ".*+(){}[]|?^$\\";
	int i;
	int has_meta = FALSE;
	int res;
	char *matched;

	/* simple checking for has meta characters in re */
	for (i = 0; i < len; i++) {
		if (strchr(metas, text[i]) != NULL) {
			has_meta = TRUE;
			break;
		}
	}

	/* make accessable to gdb */
	matched = &buf[RESTART(re, buf)];

	if (has_meta)
		return FALSE;	/* give up early, can't be string match */

	res = STREQN(text, matched, len);

	return res;
}
