| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | /* | ||
| 2 | * Lagged Fibonacci PRNG | ||
| 3 | * Copyright (c) 2008 Michael Niedermayer | ||
| 4 | * | ||
| 5 | * This file is part of FFmpeg. | ||
| 6 | * | ||
| 7 | * FFmpeg is free software; you can redistribute it and/or | ||
| 8 | * modify it under the terms of the GNU Lesser General Public | ||
| 9 | * License as published by the Free Software Foundation; either | ||
| 10 | * version 2.1 of the License, or (at your option) any later version. | ||
| 11 | * | ||
| 12 | * FFmpeg is distributed in the hope that it will be useful, | ||
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| 15 | * Lesser General Public License for more details. | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU Lesser General Public | ||
| 18 | * License along with FFmpeg; if not, write to the Free Software | ||
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | ||
| 20 | */ | ||
| 21 | |||
| 22 | #include <inttypes.h> | ||
| 23 | #include <limits.h> | ||
| 24 | #include <math.h> | ||
| 25 | #include "lfg.h" | ||
| 26 | #include "crc.h" | ||
| 27 | #include "md5.h" | ||
| 28 | #include "error.h" | ||
| 29 | #include "intreadwrite.h" | ||
| 30 | #include "attributes.h" | ||
| 31 | |||
| 32 | 347 | av_cold void av_lfg_init(AVLFG *c, unsigned int seed) | |
| 33 | { | ||
| 34 | 347 | uint8_t tmp[16] = { 0 }; | |
| 35 | int i; | ||
| 36 | |||
| 37 |
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5205 | for (i = 8; i < 64; i += 4) { |
| 38 | 4858 | AV_WL32(tmp, seed); | |
| 39 | 4858 | tmp[4] = i; | |
| 40 | 4858 | av_md5_sum(tmp, tmp, 16); | |
| 41 | 4858 | c->state[i ] = AV_RL32(tmp); | |
| 42 | 4858 | c->state[i + 1] = AV_RL32(tmp + 4); | |
| 43 | 4858 | c->state[i + 2] = AV_RL32(tmp + 8); | |
| 44 | 4858 | c->state[i + 3] = AV_RL32(tmp + 12); | |
| 45 | } | ||
| 46 | 347 | c->index = 0; | |
| 47 | 347 | } | |
| 48 | |||
| 49 | 500 | void av_bmg_get(AVLFG *lfg, double out[2]) | |
| 50 | { | ||
| 51 | double x1, x2, w; | ||
| 52 | |||
| 53 | do { | ||
| 54 | 676 | x1 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; | |
| 55 | 676 | x2 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; | |
| 56 | 676 | w = x1 * x1 + x2 * x2; | |
| 57 |
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676 | } while (w >= 1.0); |
| 58 | |||
| 59 | 500 | w = sqrt((-2.0 * log(w)) / w); | |
| 60 | 500 | out[0] = x1 * w; | |
| 61 | 500 | out[1] = x2 * w; | |
| 62 | 500 | } | |
| 63 | |||
| 64 | 33 | int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length) { | |
| 65 | unsigned int beg, end, segm; | ||
| 66 | const AVCRC *avcrc; | ||
| 67 | 33 | uint32_t crc = 1; | |
| 68 | |||
| 69 | /* avoid integer overflow in the loop below. */ | ||
| 70 |
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33 | if (length > (UINT_MAX / 128U)) return AVERROR(EINVAL); |
| 71 | |||
| 72 | 33 | c->index = 0; | |
| 73 | 33 | avcrc = av_crc_get_table(AV_CRC_32_IEEE); /* This can't fail. It's a well-defined table in crc.c */ | |
| 74 | |||
| 75 | /* across 64 segments of the incoming data, | ||
| 76 | * do a running crc of each segment and store the crc as the state for that slot. | ||
| 77 | * this works even if the length of the segment is 0 bytes. */ | ||
| 78 | 33 | beg = 0; | |
| 79 |
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2145 | for (segm = 0;segm < 64;segm++) { |
| 80 | 2112 | end = (((segm + 1) * length) / 64); | |
| 81 | 2112 | crc = av_crc(avcrc, crc, data + beg, end - beg); | |
| 82 | 2112 | c->state[segm] = (unsigned int)crc; | |
| 83 | 2112 | beg = end; | |
| 84 | } | ||
| 85 | |||
| 86 | 33 | return 0; | |
| 87 | } | ||
| 88 |