| 1 | // SPDX-License-Identifier: GPL-2.0 |
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| 2 | /* |
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| 3 | * Generic Reed Solomon encoder / decoder library |
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| 4 | * |
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| 5 | * Copyright 2002, Phil Karn, KA9Q |
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| 6 | * May be used under the terms of the GNU General Public License (GPL) |
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| 7 | * |
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| 8 | * Adaption to the kernel by Thomas Gleixner (tglx@linutronix.de) |
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| 9 | * |
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| 10 | * Generic data width independent code which is included by the wrappers. |
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| 11 | */ |
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| 12 | { |
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| 13 | struct rs_codec *rs = rsc->codec; |
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| 14 | int i, j, pad; |
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| 15 | int nn = rs->nn; |
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| 16 | int nroots = rs->nroots; |
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| 17 | uint16_t *alpha_to = rs->alpha_to; |
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| 18 | uint16_t *index_of = rs->index_of; |
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| 19 | uint16_t *genpoly = rs->genpoly; |
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| 20 | uint16_t fb; |
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| 21 | uint16_t msk = (uint16_t) rs->nn; |
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| 22 | |
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| 23 | /* Check length parameter for validity */ |
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| 24 | pad = nn - nroots - len; |
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| 25 | if (pad < 0 || pad >= nn) |
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| 26 | return -ERANGE; |
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| 27 | |
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| 28 | for (i = 0; i < len; i++) { |
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| 29 | fb = index_of[((((uint16_t) data[i])^invmsk) & msk) ^ par[0]]; |
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| 30 | /* feedback term is non-zero */ |
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| 31 | if (fb != nn) { |
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| 32 | for (j = 1; j < nroots; j++) { |
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| 33 | par[j] ^= alpha_to[rs_modnn(rs, fb + |
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| 34 | genpoly[nroots - j])]; |
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| 35 | } |
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| 36 | } |
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| 37 | /* Shift */ |
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| 38 | memmove(&par[0], &par[1], sizeof(uint16_t) * (nroots - 1)); |
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| 39 | if (fb != nn) { |
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| 40 | par[nroots - 1] = alpha_to[rs_modnn(rs, |
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| 41 | fb + genpoly[0])]; |
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| 42 | } else { |
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| 43 | par[nroots - 1] = 0; |
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| 44 | } |
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| 45 | } |
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| 46 | return 0; |
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| 47 | } |
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| 48 | |
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