| /* |
| * Lagged Fibonacci PRNG |
| * Copyright (c) 2008 Michael Niedermayer |
| * |
| * This file is part of FFmpeg. |
| * |
| * FFmpeg is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU Lesser General Public |
| * License as published by the Free Software Foundation; either |
| * version 2.1 of the License, or (at your option) any later version. |
| * |
| * FFmpeg is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public |
| * License along with FFmpeg; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| |
| #include <inttypes.h> |
| #include <limits.h> |
| #include <math.h> |
| #include "lfg.h" |
| #include "crc.h" |
| #include "md5.h" |
| #include "error.h" |
| #include "intreadwrite.h" |
| #include "attributes.h" |
| |
| av_cold void av_lfg_init(AVLFG *c, unsigned int seed) |
| { |
| uint8_t tmp[16] = { 0 }; |
| int i; |
| |
| for (i = 8; i < 64; i += 4) { |
| AV_WL32(tmp, seed); |
| tmp[4] = i; |
| av_md5_sum(tmp, tmp, 16); |
| c->state[i ] = AV_RL32(tmp); |
| c->state[i + 1] = AV_RL32(tmp + 4); |
| c->state[i + 2] = AV_RL32(tmp + 8); |
| c->state[i + 3] = AV_RL32(tmp + 12); |
| } |
| c->index = 0; |
| } |
| |
| void av_bmg_get(AVLFG *lfg, double out[2]) |
| { |
| double x1, x2, w; |
| |
| do { |
| x1 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; |
| x2 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; |
| w = x1 * x1 + x2 * x2; |
| } while (w >= 1.0); |
| |
| w = sqrt((-2.0 * log(w)) / w); |
| out[0] = x1 * w; |
| out[1] = x2 * w; |
| } |
| |
| int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length) { |
| unsigned int beg, end, segm; |
| const AVCRC *avcrc; |
| uint32_t crc = 1; |
| |
| /* avoid integer overflow in the loop below. */ |
| if (length > (UINT_MAX / 128U)) return AVERROR(EINVAL); |
| |
| c->index = 0; |
| avcrc = av_crc_get_table(AV_CRC_32_IEEE); /* This can't fail. It's a well-defined table in crc.c */ |
| |
| /* across 64 segments of the incoming data, |
| * do a running crc of each segment and store the crc as the state for that slot. |
| * this works even if the length of the segment is 0 bytes. */ |
| beg = 0; |
| for (segm = 0;segm < 64;segm++) { |
| end = (((segm + 1) * length) / 64); |
| crc = av_crc(avcrc, crc, data + beg, end - beg); |
| c->state[segm] = (unsigned int)crc; |
| beg = end; |
| } |
| |
| return 0; |
| } |