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cnmagic.c revision 1.1 
      1 /*	$NetBSD: cnmagic.c,v 1.1 2000/11/08 22:41:59 eeh Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2000 Eduardo Horvath
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *      This product includes software developed by Eduardo Horvath.
     18  * 4. The name of the author may not be used to endorse or promote products
     19  *    derived from this software without specific prior written permission
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 #include <sys/param.h>
     34 #include <sys/systm.h>
     35 
     36 #define ENCODE_STATE(c, n) (short)(((c)&0x1ff)|(((n)&0x7f)<<9))
     37 
     38 static unsigned short cn_magic[CNS_LEN];
     39 
     40 /*
     41  * Initialize a cnm_state_t.
     42  */
     43 void
     44 cn_init_magic(cnm_state_t *cnm) {
     45 	cnm->cnm_state = 0;
     46 	cnm->cnm_magic = cn_magic;
     47 }
     48 
     49 /*
     50  * Destroy a cnm_state_t.
     51  */
     52 void
     53 cn_destroy_magic(cnm_state_t *cnm) {
     54 	cnm->cnm_state = 0;
     55 	cnm->cnm_magic = NULL;
     56 }
     57 
     58 /*
     59  * Translate a magic string to a state
     60  * machine table.
     61  */
     62 int
     63 cn_set_magic(char *magic)
     64 {
     65 	unsigned int i, c, n;
     66 	unsigned short m[CNS_LEN];
     67 
     68 	for (i=0; i<CNS_LEN; i++) {
     69 		c = (*magic++)&0xff;
     70 		n = *magic ? i+1 : CNS_TERM;
     71 		switch (c) {
     72 		case 0:
     73 			/* End of string */
     74 			if (i == 0) {
     75 				/* empty string? */
     76 				cn_magic[0] = 0;
     77 #ifdef DEBUG
     78 				printf("cn_set_magic(): empty!\n");
     79 #endif
     80 				return (0);
     81 			}
     82 			do {
     83 				cn_magic[i] = m[i];
     84 			} while (i--);
     85 			return(0);
     86 		case 0x27:
     87 			/* Escape sequence */
     88 			c = (*magic++)&0xff;
     89 			n = *magic ? i+1 : CNS_TERM;
     90 			switch (c) {
     91 			case 0x27:
     92 				break;
     93 			case 0x01:
     94 				/* BREAK */
     95 				c = CNC_BREAK;
     96 				break;
     97 			case 0x02:
     98 				/* NUL */
     99 				c = 0;
    100 				break;
    101 			}
    102 			/* FALLTHROUGH */
    103 		default:
    104 			/* Transition to the next state. */
    105 #ifdef DEBUG
    106 			printf("mag %d %x:%x\n", i, c, n);
    107 #endif
    108 			m[i] = ENCODE_STATE(c, n);
    109 			break;
    110 		}
    111 	}
    112 	return (EINVAL);
    113 }
    114 
    115 /*
    116  * Translatea state machine table back to
    117  * a magic string.
    118  */
    119 int
    120 cn_get_magic(char *magic, int maglen) {
    121 	unsigned int i, c;
    122 
    123 	for (i=0; i<CNS_LEN; i++) {
    124 		c = cn_magic[i];
    125 		/* Translate a character */
    126 		switch (CNS_MAGIC_VAL(c)) {
    127 		case CNC_BREAK:
    128 			*magic++ = 0x27;
    129 			*magic++ = 0x01;
    130 			break;
    131 		case 0:
    132 			*magic++ = 0x27;
    133 			*magic++ = 0x02;
    134 			break;
    135 		case 0x27:
    136 			*magic++ = 0x27;
    137 			*magic++ = 0x27;
    138 			break;
    139 		default:
    140 			*magic++ = (c&0x0ff);
    141 			break;
    142 		}
    143 		/* Now go to the next state */
    144 		i = CNS_MAGIC_NEXT(c);
    145 		if (i == CNS_TERM || i == 0) {
    146 			/* Either termination state or empty machine */
    147 			*magic++ = 0;
    148 			return (0);
    149 		}
    150 	}
    151 	return (EINVAL);
    152 }
    153 
    154