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1.1 root 1: /*
2: ** Packet check bytes calculation
3: */
4:
5: #ifdef vax
6: /*
7: ** Vax "crc" instruction look-up table for polynomial = 0120001
8: */
9:
10: unsigned long crc16t[] =
11: {
12: 0, 0146001, 0154001, 012000, 0170001, 036000, 024000, 0162001
13: ,0120001, 066000, 074000, 0132001, 050000, 0116001, 0104001, 042000
14: };
15:
16: /*ARGSUSED*/
17: int
18: crc(s, n)
19: unsigned char * s;
20: int n;
21: {
22: asm(" crc _crc16t,$0,8(ap),*4(ap) ");
23: asm(" cmpw r0,(r3) ");
24: asm(" beqlu OK ");
25: asm(" movw r0,(r3) ");
26: asm(" movl $1,r0 ");
27: asm(" ret ");
28: asm("OK:movw r0,(r3) ");
29: return 0;
30: }
31:
32: #else vax
33:
34:
35: /*
36: ** crc-16: x**16 + x**15 + x**2 + 1
37: */
38:
39: typedef unsigned char uchar;
40: typedef unsigned short ushort;
41:
42: #define lobyte(X) (X&0xff)
43: #define hibyte(X) ((X>>8)&0xff)
44:
45: ushort crc16t_32[2][16] =
46: {
47: 0, 0140301, 0140601, 0500, 0141401, 01700, 01200, 0141101,
48: 0143001, 03300, 003600, 0143501, 02400, 0142701, 0142201, 02100,
49: 0, 0146001, 0154001, 012000, 0170001, 036000, 024000, 0162001,
50: 0120001, 066000, 074000, 0132001, 050000, 0116001, 0104001, 042000
51: };
52:
53: /*#ifndef mc68000*/
54: int
55: crc(buffer, nbytes)
56: register uchar *buffer;
57: int nbytes;
58: {
59: register ushort tcrc = 0;
60: register int temp;
61: register int i;
62:
63: if ( (i = nbytes) > 0 )
64: do
65: {
66: temp = tcrc ^ *buffer++;
67: tcrc = crc16t_32[0][temp & 017]
68: ^ crc16t_32[1][(temp>>4) & 017]
69: ^ (tcrc>>8);
70: }
71: while
72: ( --i > 0 );
73:
74: if ( lobyte(tcrc) != *buffer )
75: i++;
76: *buffer++ = lobyte(tcrc);
77:
78: if ( hibyte(tcrc) != *buffer )
79: i++;
80: *buffer++ = hibyte(tcrc);
81:
82: return i;
83: }
84: /*#else mc68000
85: asm(" text ");
86: asm(" global crc ");
87: asm("crc: ");
88: asm(" link %fp,&crcF ");
89: asm(" movm.l &crcM,crcS(%fp) ");
90: asm(" mov.l 8(%fp),%a2 ");
91: asm(" mov.l &0,%d2 ");
92: asm(" mov.w 12(%fp),%d4 ");
93: asm(" ble crc%140 ");
94: asm("crc%170: ");
95: asm(" mov.b (%a2)+,%d3 ");
96: asm(" eor.b %d2,%d3 ");
97: asm(" mov.l &15,%d0 ");
98: asm(" and.b %d3,%d0 ");
99: asm(" add.l %d0,%d0 ");
100: asm(" mov.l &crc16t_3,%a1 ");
101: asm(" mov.w 0(%a1,%d0.l),%d0");
102: asm(" lsr.b &3,%d3 ");
103: asm(" and.w &30,%d3 ");
104: asm(" mov.l &crc16t_3+32,%a0");
105: asm(" mov.w 0(%a0,%d3.w),%d1");
106: asm(" eor.w %d0,%d1 ");
107: asm(" lsr.w &8,%d2 ");
108: asm(" eor.w %d1,%d2 ");
109: asm(" sub.w &1,%d4 ");
110: asm(" bgt crc%170 ");
111: asm("crc%140: ");
112: asm(" cmp.b %d2,(%a2) ");
113: asm(" beq crc%180 ");
114: asm(" add.w &1,%d4 ");
115: asm("crc%180: ");
116: asm(" mov.b %d2,(%a2)+ ");
117: asm(" lsr.w &8,%d2 ");
118: asm(" cmp.b %d2,(%a2) ");
119: asm(" beq crc%190 ");
120: asm(" add.w &1,%d4 ");
121: asm("crc%190: ");
122: asm(" mov.b %d2,(%a2)+ ");
123: asm(" mov.w %d4,%d0 ");
124: asm(" movm.l crcS(%fp),&crcM ");
125: asm(" unlk %fp ");
126: asm(" rts ");
127: asm(" set crcS,-16 ");
128: asm(" set crcF,-22 ");
129: asm(" set crcM,02034 ");
130: #endif mc68000 */
131: #endif vax
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