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cnmagic.c revision 1.9 
      1 /*	$NetBSD: cnmagic.c,v 1.9 2006/11/01 10:17:58 yamt 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/cdefs.h>
     34 __KERNEL_RCSID(0, "$NetBSD: cnmagic.c,v 1.9 2006/11/01 10:17:58 yamt Exp $");
     35 
     36 #include <sys/param.h>
     37 #include <sys/systm.h>
     38 #include <sys/kernel.h>
     39 
     40 #define ENCODE_STATE(c, n) (short)(((c)&0x1ff)|(((n)&0x7f)<<9))
     41 
     42 static unsigned short cn_magic[CNS_LEN];
     43 
     44 /*
     45  * Initialize a cnm_state_t.
     46  */
     47 void
     48 cn_init_magic(cnm_state_t *cnm)
     49 {
     50 	cnm->cnm_state = 0;
     51 	cnm->cnm_magic = cn_magic;
     52 }
     53 
     54 /*
     55  * Destroy a cnm_state_t.
     56  */
     57 void
     58 cn_destroy_magic(cnm_state_t *cnm)
     59 {
     60 	cnm->cnm_state = 0;
     61 	cnm->cnm_magic = NULL;
     62 }
     63 
     64 /*
     65  * Translate a magic string to a state
     66  * machine table.
     67  */
     68 int
     69 cn_set_magic(const char *magic)
     70 {
     71 	unsigned int i, c, n;
     72 	unsigned short m[CNS_LEN];
     73 
     74 	for (i = 0; i < CNS_LEN; i++) {
     75 		c = (*magic++) & 0xff;
     76 		n = *magic ? i+1 : CNS_TERM;
     77 		switch (c) {
     78 		case 0:
     79 			/* End of string */
     80 			if (i == 0) {
     81 				/* empty string? */
     82 				cn_magic[0] = 0;
     83 #ifdef DEBUG
     84 				printf("cn_set_magic(): empty!\n");
     85 #endif
     86 				return (0);
     87 			}
     88 			do {
     89 				cn_magic[i] = m[i];
     90 			} while (i--);
     91 			return(0);
     92 		case 0x27:
     93 			/* Escape sequence */
     94 			c = (*magic++) & 0xff;
     95 			n = *magic ? i+1 : CNS_TERM;
     96 			switch (c) {
     97 			case 0x27:
     98 				break;
     99 			case 0x01:
    100 				/* BREAK */
    101 				c = CNC_BREAK;
    102 				break;
    103 			case 0x02:
    104 				/* NUL */
    105 				c = 0;
    106 				break;
    107 			}
    108 			/* FALLTHROUGH */
    109 		default:
    110 			/* Transition to the next state. */
    111 #ifdef DEBUG
    112 			if (!cold)
    113 				printf("mag %d %x:%x\n", i, c, n);
    114 #endif
    115 			m[i] = ENCODE_STATE(c, n);
    116 			break;
    117 		}
    118 	}
    119 	return (EINVAL);
    120 }
    121 
    122 /*
    123  * Translatea state machine table back to
    124  * a magic string.
    125  */
    126 int
    127 cn_get_magic(char *magic, size_t maglen)
    128 {
    129 	size_t i, c;
    130 
    131 	for (i = 0; i < CNS_LEN;) {
    132 		c = cn_magic[i];
    133 		/* Translate a character */
    134 		switch (CNS_MAGIC_VAL(c)) {
    135 		case CNC_BREAK:
    136 			*magic++ = 0x27;
    137 			*magic++ = 0x01;
    138 			break;
    139 		case 0:
    140 			*magic++ = 0x27;
    141 			*magic++ = 0x02;
    142 			break;
    143 		case 0x27:
    144 			*magic++ = 0x27;
    145 			*magic++ = 0x27;
    146 			break;
    147 		default:
    148 			*magic++ = (c & 0x0ff);
    149 			break;
    150 		}
    151 		/* Now go to the next state */
    152 		i = CNS_MAGIC_NEXT(c);
    153 		if (i == CNS_TERM || i == 0) {
    154 			/* Either termination state or empty machine */
    155 			*magic++ = 0;
    156 			return (0);
    157 		}
    158 	}
    159 	return (EINVAL);
    160 }
    161 
    162