/*      $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;
}