1 /*
2  * lib/reed_solomon/encode_rs.c
3  *
4  * Overview:
5  *   Generic Reed Solomon encoder / decoder library
6  *
7  * Copyright 2002, Phil Karn, KA9Q
8  * May be used under the terms of the GNU General Public License (GPL)
9  *
10  * Adaption to the kernel by Thomas Gleixner (tglx@linutronix.de)
11  *
12  * $Id: encode_rs.c,v 1.5 2005/11/07 11:14:59 gleixner Exp $
13  *
14  */
15 
16 /* Generic data width independent code which is included by the
17  * wrappers.
18  * int encode_rsX (struct rs_control *rs, uintX_t *data, int len, uintY_t *par)
19  */
20 {
21 	int i, j, pad;
22 	int nn = rs->nn;
23 	int nroots = rs->nroots;
24 	uint16_t *alpha_to = rs->alpha_to;
25 	uint16_t *index_of = rs->index_of;
26 	uint16_t *genpoly = rs->genpoly;
27 	uint16_t fb;
28 	uint16_t msk = (uint16_t) rs->nn;
29 
30 	/* Check length parameter for validity */
31 	pad = nn - nroots - len;
32 	if (pad < 0 || pad >= nn)
33 		return -ERANGE;
34 
35 	for (i = 0; i < len; i++) {
36 		fb = index_of[((((uint16_t) data[i])^invmsk) & msk) ^ par[0]];
37 		/* feedback term is non-zero */
38 		if (fb != nn) {
39 			for (j = 1; j < nroots; j++) {
40 				par[j] ^= alpha_to[rs_modnn(rs, fb +
41 							 genpoly[nroots - j])];
42 			}
43 		}
44 		/* Shift */
45 		memmove(&par[0], &par[1], sizeof(uint16_t) * (nroots - 1));
46 		if (fb != nn) {
47 			par[nroots - 1] = alpha_to[rs_modnn(rs,
48 							    fb + genpoly[0])];
49 		} else {
50 			par[nroots - 1] = 0;
51 		}
52 	}
53 	return 0;
54 }
55