/*      $OpenBSD: unvis.c,v 1.17 2015/09/13 11:32:51 guenther 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 isoctal(c)      (((u_char)(c)) >= '0' && ((u_char)(c)) <= '7')

/*
 * 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_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 = 0;
                        *astate = S_GROUND;
                        return (0);
                case '\\':
                case '"':
                        *cp = c;
                        *astate = S_GROUND;
                        return (UNVIS_VALID);
                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);

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

/*
 * 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);
}