/*      $NetBSD: cnmagic.c,v 1.14 2017/05/04 11:01:16 kamil Exp $       */

/*
 * Copyright (c) 2000 Eduardo Horvath
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: cnmagic.c,v 1.14 2017/05/04 11:01:16 kamil Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>

#define ENCODE_STATE(c, n) (short)(((c)&0x1ff)|(((n)&0x7f)<<9))

static unsigned short cn_magic[CNS_LEN];

/*
 * Initialize a cnm_state_t.
 */
void
cn_init_magic(cnm_state_t *cnm)
{
        cnm->cnm_state = 0;
        cnm->cnm_magic = cn_magic;
}

/*
 * Destroy a cnm_state_t.
 */
void
cn_destroy_magic(cnm_state_t *cnm)
{
        cnm->cnm_state = 0;
        cnm->cnm_magic = NULL;
}

/*
 * Translate a magic string to a state
 * machine table.
 */
int
cn_set_magic(const char *smagic)
{
        const unsigned char *magic = (const unsigned char *)smagic;
        unsigned short i, c, n;
        unsigned short m[CNS_LEN];

        for (i = 0; i < CNS_LEN; i++) {
                c = *magic++;
                switch (c) {
                case 0:
                        /* End of string */
                        if (i == 0) {
                                /* empty string? */
#ifdef DEBUG
                                printf("cn_set_magic(): empty!\n");
#endif
                        }
                        cn_magic[i] = 0;
                        while (i--)
                                cn_magic[i] = m[i];
                        return 0;
                case 0x27:
                        /* Escape sequence */
                        c = *magic++;
                        switch (c) {
                        case 0x27:
                                break;
                        case 0x01:
                                /* BREAK */
                                c = CNC_BREAK;
                                break;
                        case 0x02:
                                /* NUL */
                                c = 0;
                                break;
                        }
                        /* FALLTHROUGH */
                default:
                        /* Transition to the next state. */
                        n = *magic ? i + 1 : CNS_TERM;
#ifdef DEBUG
                        if (!cold)
                                aprint_normal("mag %d %x:%x\n", i, c, n);
#endif
                        m[i] = ENCODE_STATE(c, n);
                        break;
                }
        }
        return EINVAL;
}

/*
 * Translate a state machine table back to
 * a magic string.
 */
int
cn_get_magic(char *magic, size_t maglen)
{
        size_t i, n = 0;

#define ADD_CHAR(x) \
do \
        if (n < maglen) \
                magic[n++] = (x); \
        else \
                goto error; \
while (/*CONSTCOND*/0)

        for (i = 0; i < CNS_LEN; /* empty */) {
                unsigned short c = cn_magic[i];
                i = CNS_MAGIC_NEXT(c);
                if (i == 0)
                        goto finish;

                /* Translate a character */
                switch (CNS_MAGIC_VAL(c)) {
                case CNC_BREAK:
                        ADD_CHAR(0x27);
                        ADD_CHAR(0x01);
                        break;
                case 0:
                        ADD_CHAR(0x27);
                        ADD_CHAR(0x02);
                        break;
                case 0x27:
                        ADD_CHAR(0x27);
                        ADD_CHAR(0x27);
                        break;
                default:
                        ADD_CHAR(c);
                        break;
                }
                /* Now go to the next state */
                if (i == CNS_TERM)
                        goto finish;
        }

error:
        return EINVAL;

finish:
        /* Either termination state or empty machine */
        ADD_CHAR('\0');
        return 0;
}