| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | /* | ||
| 2 | * This file is part of FFmpeg. | ||
| 3 | * | ||
| 4 | * FFmpeg is free software; you can redistribute it and/or | ||
| 5 | * modify it under the terms of the GNU Lesser General Public | ||
| 6 | * License as published by the Free Software Foundation; either | ||
| 7 | * version 2.1 of the License, or (at your option) any later version. | ||
| 8 | * | ||
| 9 | * FFmpeg is distributed in the hope that it will be useful, | ||
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| 12 | * Lesser General Public License for more details. | ||
| 13 | * | ||
| 14 | * You should have received a copy of the GNU Lesser General Public | ||
| 15 | * License along with FFmpeg; if not, write to the Free Software | ||
| 16 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | ||
| 17 | */ | ||
| 18 | |||
| 19 | #ifndef AVUTIL_CRC_INTERNAL_H | ||
| 20 | #define AVUTIL_CRC_INTERNAL_H | ||
| 21 | |||
| 22 | #include <stdint.h> | ||
| 23 | #include "libavutil/attributes.h" | ||
| 24 | #include "libavutil/reverse.h" | ||
| 25 | |||
| 26 | 48 | static uint64_t reverse(uint64_t p, unsigned int deg) | |
| 27 | { | ||
| 28 | 48 | uint64_t ret = 0; | |
| 29 | int i; | ||
| 30 |
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188 | for (i = 0; i < (deg / 8); i += 1) { |
| 31 | 140 | ret = (ret << 8) | (ff_reverse[p & 0xff]); | |
| 32 | 140 | p >>= 8; | |
| 33 | } | ||
| 34 | 48 | int rem = (deg + 1) - 8 * i; | |
| 35 | 48 | ret = (ret << rem) | (ff_reverse[p & 0xff] >> (8 - rem)); | |
| 36 | 48 | return ret; | |
| 37 | } | ||
| 38 | |||
| 39 | 20 | av_unused static uint64_t xnmodp(unsigned n, uint64_t poly, unsigned deg, | |
| 40 | uint64_t *div, int bitreverse) | ||
| 41 | { | ||
| 42 | uint64_t mod, mask, high; | ||
| 43 | |||
| 44 |
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20 | if (n < deg) { |
| 45 | ✗ | *div = 0; | |
| 46 | ✗ | return poly; | |
| 47 | } | ||
| 48 | 20 | mask = ((uint64_t)1 << deg) - 1; | |
| 49 | 20 | poly &= mask; | |
| 50 | 20 | mod = poly; | |
| 51 | 20 | *div = 1; | |
| 52 | 20 | deg--; | |
| 53 |
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4756 | while (--n > deg) { |
| 54 | 4736 | high = (mod >> deg) & 1; | |
| 55 | 4736 | *div = (*div << 1) | high; | |
| 56 | 4736 | mod <<= 1; | |
| 57 |
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4736 | if (high) |
| 58 | 2392 | mod ^= poly; | |
| 59 | } | ||
| 60 | 20 | uint64_t ret = mod & mask; | |
| 61 |
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20 | if (bitreverse) { |
| 62 | 20 | *div = reverse(*div, deg) << 1; | |
| 63 | 20 | return reverse(ret, deg) << 1; | |
| 64 | } | ||
| 65 | ✗ | return ret; | |
| 66 | } | ||
| 67 | |||
| 68 | #endif /* AVUTIL_CRC_INTERNAL_H */ | ||
| 69 |