FreeBSD/Linux Kernel Cross Reference
sys/kern/cnmagic.c

     /*      $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;
   }

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