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dc8f923e | 1 | // SPDX-License-Identifier: GPL-2.0 |
03ead842 | 2 | /* |
3413e189 | 3 | * Generic Reed Solomon encoder / decoder library |
03ead842 | 4 | * |
1da177e4 LT |
5 | * Copyright 2002, Phil Karn, KA9Q |
6 | * May be used under the terms of the GNU General Public License (GPL) | |
7 | * | |
8 | * Adaption to the kernel by Thomas Gleixner (tglx@linutronix.de) | |
9 | * | |
3413e189 | 10 | * Generic data width independent code which is included by the wrappers. |
1da177e4 LT |
11 | */ |
12 | { | |
21633981 | 13 | struct rs_codec *rs = rsc->codec; |
1da177e4 LT |
14 | int i, j, pad; |
15 | int nn = rs->nn; | |
16 | int nroots = rs->nroots; | |
17 | uint16_t *alpha_to = rs->alpha_to; | |
18 | uint16_t *index_of = rs->index_of; | |
19 | uint16_t *genpoly = rs->genpoly; | |
20 | uint16_t fb; | |
21 | uint16_t msk = (uint16_t) rs->nn; | |
22 | ||
23 | /* Check length parameter for validity */ | |
24 | pad = nn - nroots - len; | |
25 | if (pad < 0 || pad >= nn) | |
26 | return -ERANGE; | |
27 | ||
28 | for (i = 0; i < len; i++) { | |
29 | fb = index_of[((((uint16_t) data[i])^invmsk) & msk) ^ par[0]]; | |
30 | /* feedback term is non-zero */ | |
03ead842 | 31 | if (fb != nn) { |
1da177e4 | 32 | for (j = 1; j < nroots; j++) { |
03ead842 | 33 | par[j] ^= alpha_to[rs_modnn(rs, fb + |
1da177e4 LT |
34 | genpoly[nroots - j])]; |
35 | } | |
36 | } | |
37 | /* Shift */ | |
38 | memmove(&par[0], &par[1], sizeof(uint16_t) * (nroots - 1)); | |
39 | if (fb != nn) { | |
03ead842 | 40 | par[nroots - 1] = alpha_to[rs_modnn(rs, |
1da177e4 LT |
41 | fb + genpoly[0])]; |
42 | } else { | |
43 | par[nroots - 1] = 0; | |
44 | } | |
45 | } | |
46 | return 0; | |
47 | } |