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cnmagic.c revision 1.2 
      1 /*	$NetBSD: cnmagic.c,v 1.2 2000/12/19 04:39:19 mrg 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 #include <sys/kernel.h>
     36 
     37 #define ENCODE_STATE(c, n) (short)(((c)&0x1ff)|(((n)&0x7f)<<9))
     38 
     39 static unsigned short cn_magic[CNS_LEN];
     40 
     41 /*
     42  * Initialize a cnm_state_t.
     43  */
     44 void
     45 cn_init_magic(cnm_state_t *cnm) {
     46 	cnm->cnm_state = 0;
     47 	cnm->cnm_magic = cn_magic;
     48 }
     49 
     50 /*
     51  * Destroy a cnm_state_t.
     52  */
     53 void
     54 cn_destroy_magic(cnm_state_t *cnm) {
     55 	cnm->cnm_state = 0;
     56 	cnm->cnm_magic = NULL;
     57 }
     58 
     59 /*
     60  * Translate a magic string to a state
     61  * machine table.
     62  */
     63 int
     64 cn_set_magic(char *magic)
     65 {
     66 	unsigned int i, c, n;
     67 	unsigned short m[CNS_LEN];
     68 
     69 	for (i=0; i<CNS_LEN; i++) {
     70 		c = (*magic++)&0xff;
     71 		n = *magic ? i+1 : CNS_TERM;
     72 		switch (c) {
     73 		case 0:
     74 			/* End of string */
     75 			if (i == 0) {
     76 				/* empty string? */
     77 				cn_magic[0] = 0;
     78 #ifdef DEBUG
     79 				printf("cn_set_magic(): empty!\n");
     80 #endif
     81 				return (0);
     82 			}
     83 			do {
     84 				cn_magic[i] = m[i];
     85 			} while (i--);
     86 			return(0);
     87 		case 0x27:
     88 			/* Escape sequence */
     89 			c = (*magic++)&0xff;
     90 			n = *magic ? i+1 : CNS_TERM;
     91 			switch (c) {
     92 			case 0x27:
     93 				break;
     94 			case 0x01:
     95 				/* BREAK */
     96 				c = CNC_BREAK;
     97 				break;
     98 			case 0x02:
     99 				/* NUL */
    100 				c = 0;
    101 				break;
    102 			}
    103 			/* FALLTHROUGH */
    104 		default:
    105 			/* Transition to the next state. */
    106 #ifdef DEBUG
    107 			if (!cold)
    108 				printf("mag %d %x:%x\n", i, c, n);
    109 #endif
    110 			m[i] = ENCODE_STATE(c, n);
    111 			break;
    112 		}
    113 	}
    114 	return (EINVAL);
    115 }
    116 
    117 /*
    118  * Translatea state machine table back to
    119  * a magic string.
    120  */
    121 int
    122 cn_get_magic(char *magic, int maglen) {
    123 	unsigned int i, c;
    124 
    125 	for (i=0; i<CNS_LEN; i++) {
    126 		c = cn_magic[i];
    127 		/* Translate a character */
    128 		switch (CNS_MAGIC_VAL(c)) {
    129 		case CNC_BREAK:
    130 			*magic++ = 0x27;
    131 			*magic++ = 0x01;
    132 			break;
    133 		case 0:
    134 			*magic++ = 0x27;
    135 			*magic++ = 0x02;
    136 			break;
    137 		case 0x27:
    138 			*magic++ = 0x27;
    139 			*magic++ = 0x27;
    140 			break;
    141 		default:
    142 			*magic++ = (c&0x0ff);
    143 			break;
    144 		}
    145 		/* Now go to the next state */
    146 		i = CNS_MAGIC_NEXT(c);
    147 		if (i == CNS_TERM || i == 0) {
    148 			/* Either termination state or empty machine */
    149 			*magic++ = 0;
    150 			return (0);
    151 		}
    152 	}
    153 	return (EINVAL);
    154 }
    155 
    156