/*	$OpenBSD: unvis.c,v 1.13 2010/08/21 18:59:15 djm Exp $ */
/*-
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <ctype.h>
#include <vis.h>

/*
 * decode driven by state machine
 */
#define	S_GROUND	0	/* haven't seen escape char */
#define	S_START		1	/* start decoding special sequence */
#define	S_META		2	/* metachar started (M) */
#define	S_META1		3	/* metachar more, regular char (-) */
#define	S_CTRL		4	/* control char started (^) */
#define	S_OCTAL2	5	/* octal digit 2 */
#define	S_OCTAL3	6	/* octal digit 3 */
#define	S_HEX1		7	/* hex digit 1 */
#define	S_HEX2		8	/* hex digit 2 */

#define	isoctal(c)	(((u_char)(c)) >= '0' && ((u_char)(c)) <= '7')
#define	ishex(c)	((((u_char)(c)) >= '0' && ((u_char)(c)) <= '9') || \
			 (((u_char)(c)) >= 'a' && ((u_char)(c)) <= 'f') || \
			 (((u_char)(c)) >= 'A' && ((u_char)(c)) <= 'F'))

static u_int
dehex(u_int c)
{
	if (c >= '0' && c <= '9')
		return c - '0';
	if (c >= 'a' && c <= 'f')
		return 10 + c - 'a';
	if (c >= 'A' && c <= 'F')
		return 10 + c - 'A';
	return 0;
}

/*
 * unvis - decode characters previously encoded by vis
 */
int
unvis(char *cp, char c, int *astate, int flag)
{

	if (flag & UNVIS_END) {
		if (*astate == S_OCTAL2 || *astate == S_OCTAL3 ||
		    *astate == S_HEX1 || *astate == S_HEX2) {
			*astate = S_GROUND;
			return (UNVIS_VALID);
		} 
		return (*astate == S_GROUND ? UNVIS_NOCHAR : UNVIS_SYNBAD);
	}

	switch (*astate) {

	case S_GROUND:
		*cp = 0;
		if (c == '\\') {
			*astate = S_START;
			return (0);
		} 
		*cp = c;
		return (UNVIS_VALID);

	case S_START:
		switch(c) {
		case '\\':
			*cp = c;
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case 'x':
			*astate = S_HEX1;
			return (0);
		case '0': case '1': case '2': case '3':
		case '4': case '5': case '6': case '7':
			*cp = (c - '0');
			*astate = S_OCTAL2;
			return (0);
		case 'M':
			*cp = (char) 0200;
			*astate = S_META;
			return (0);
		case '^':
			*astate = S_CTRL;
			return (0);
		case 'n':
			*cp = '\n';
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case 'r':
			*cp = '\r';
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case 'b':
			*cp = '\b';
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case 'a':
			*cp = '\007';
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case 'v':
			*cp = '\v';
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case 't':
			*cp = '\t';
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case 'f':
			*cp = '\f';
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case 's':
			*cp = ' ';
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case 'E':
			*cp = '\033';
			*astate = S_GROUND;
			return (UNVIS_VALID);
		case '\n':
			/*
			 * hidden newline
			 */
			*astate = S_GROUND;
			return (UNVIS_NOCHAR);
		case '$':
			/*
			 * hidden marker
			 */
			*astate = S_GROUND;
			return (UNVIS_NOCHAR);
		}
		*astate = S_GROUND;
		return (UNVIS_SYNBAD);
		 
	case S_META:
		if (c == '-')
			*astate = S_META1;
		else if (c == '^')
			*astate = S_CTRL;
		else {
			*astate = S_GROUND;
			return (UNVIS_SYNBAD);
		}
		return (0);
		 
	case S_META1:
		*astate = S_GROUND;
		*cp |= c;
		return (UNVIS_VALID);
		 
	case S_CTRL:
		if (c == '?')
			*cp |= 0177;
		else
			*cp |= c & 037;
		*astate = S_GROUND;
		return (UNVIS_VALID);

	case S_OCTAL2:	/* second possible octal digit */
		if (isoctal(c)) {
			/* 
			 * yes - and maybe a third 
			 */
			*cp = (*cp << 3) + (c - '0');
			*astate = S_OCTAL3;	
			return (0);
		} 
		/* 
		 * no - done with current sequence, push back passed char 
		 */
		*astate = S_GROUND;
		return (UNVIS_VALIDPUSH);

	case S_OCTAL3:	/* third possible octal digit */
		*astate = S_GROUND;
		if (isoctal(c)) {
			*cp = (*cp << 3) + (c - '0');
			return (UNVIS_VALID);
		}
		/*
		 * we were done, push back passed char
		 */
		return (UNVIS_VALIDPUSH);

	case S_HEX1:	/* first possible hex digit */
		if (ishex(c)) {
			/* 
			 * yes - and maybe a second
			 */
			*cp = dehex(c);
			*astate = S_HEX2;	
			return (0);
		} 
		/* 
		 * no - done with current sequence, push back passed char 
		 */
		*astate = S_GROUND;
		return (UNVIS_VALIDPUSH);

	case S_HEX2:	/* second possible hex digit */
		*astate = S_GROUND;
		if (ishex(c)) {
			*cp = ((u_int)*cp << 4) + dehex(c);
			return (UNVIS_VALID);
		}
		/*
		 * we were done, push back passed char
		 */
		return (UNVIS_VALIDPUSH);

	default:	
		/* 
		 * decoder in unknown state - (probably uninitialized) 
		 */
		*astate = S_GROUND;
		return (UNVIS_SYNBAD);
	}
}

/*
 * strunvis - decode src into dst 
 *
 *	Number of chars decoded into dst is returned, -1 on error.
 *	Dst is null terminated.
 */

int
strunvis(char *dst, const char *src)
{
	char c;
	char *start = dst;
	int state = 0;

	while ((c = *src++)) {
	again:
		switch (unvis(dst, c, &state, 0)) {
		case UNVIS_VALID:
			dst++;
			break;
		case UNVIS_VALIDPUSH:
			dst++;
			goto again;
		case 0:
		case UNVIS_NOCHAR:
			break;
		default:
			*dst = '\0';
			return (-1);
		}
	}
	if (unvis(dst, c, &state, UNVIS_END) == UNVIS_VALID)
		dst++;
	*dst = '\0';
	return (dst - start);
}

ssize_t
strnunvis(char *dst, const char *src, size_t sz)
{
	char c, p;
	char *start = dst, *end = dst + sz - 1;
	int state = 0;

	if (sz > 0)
		*end = '\0';
	while ((c = *src++)) {
	again:
		switch (unvis(&p, c, &state, 0)) {
		case UNVIS_VALID:
			if (dst < end)
				*dst = p;
			dst++;
			break;
		case UNVIS_VALIDPUSH:
			if (dst < end)
				*dst = p;
			dst++;
			goto again;
		case 0:
		case UNVIS_NOCHAR:
			break;
		default:
			if (dst <= end)
				*dst = '\0';
			return (-1);
		}
	}
	if (unvis(&p, c, &state, UNVIS_END) == UNVIS_VALID) {
		if (dst < end)
			*dst = p;
		dst++;
	}
	if (dst <= end)
		*dst = '\0';
	return (dst - start);
}