Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 1.4 2004/10/22 15:41:47 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 | } |