48 lines · c
1// SPDX-License-Identifier: GPL-2.02/*3 * Generic Reed Solomon encoder / decoder library4 *5 * Copyright 2002, Phil Karn, KA9Q6 * 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 *10 * Generic data width independent code which is included by the wrappers.11 */12{13 struct rs_codec *rs = rsc->codec;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 */31 if (fb != nn) {32 for (j = 1; j < nroots; j++) {33 par[j] ^= alpha_to[rs_modnn(rs, fb +34 genpoly[nroots - j])];35 }36 }37 /* Shift */38 memmove(&par[0], &par[1], sizeof(uint16_t) * (nroots - 1));39 if (fb != nn) {40 par[nroots - 1] = alpha_to[rs_modnn(rs,41 fb + genpoly[0])];42 } else {43 par[nroots - 1] = 0;44 }45 }46 return 0;47}48