Make ff_inverse stay with libavutil, and optional copy it to libavcodec.
The ff_inverse table is used by FASTDIV macro, defined in libavutil, but up
to now the table was defined only in libavcodec.
After this change, the main copy of ff_inverse is part of libavutil (just
like FASTDIV), but if CONFIG_SMALL is unset, then a different copy is made
available to libavcodec, to avoid the performance penalty of using an
external look up table.
Dynamic linking works, because the libraries are linked with -Bsymbolic, so
the local copy of the symbol has priority over the external; static linking
works because the table is on a standalone object file in both libraries,
so the linker is able to discard one of the two.
Tested on Linux/x86-64 and Mac OS X/x86-64.
Originally committed as revision 24383 to svn://svn.ffmpeg.org/ffmpeg/trunk
15 years ago
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/*
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* Inverse table
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* Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <stdint.h>
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Make ff_inverse stay with libavutil, and optional copy it to libavcodec.
The ff_inverse table is used by FASTDIV macro, defined in libavutil, but up
to now the table was defined only in libavcodec.
After this change, the main copy of ff_inverse is part of libavutil (just
like FASTDIV), but if CONFIG_SMALL is unset, then a different copy is made
available to libavcodec, to avoid the performance penalty of using an
external look up table.
Dynamic linking works, because the libraries are linked with -Bsymbolic, so
the local copy of the symbol has priority over the external; static linking
works because the table is on a standalone object file in both libraries,
so the linker is able to discard one of the two.
Tested on Linux/x86-64 and Mac OS X/x86-64.
Originally committed as revision 24383 to svn://svn.ffmpeg.org/ffmpeg/trunk
15 years ago
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/* a*inverse[b]>>32 == a/b for all 0<=a<=16909558 && 2<=b<=256
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* for a>16909558, is an overestimate by less than 1 part in 1<<24 */
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const uint32_t ff_inverse[257]={
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0, 4294967295U,2147483648U,1431655766, 1073741824, 858993460, 715827883, 613566757,
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536870912, 477218589, 429496730, 390451573, 357913942, 330382100, 306783379, 286331154,
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268435456, 252645136, 238609295, 226050911, 214748365, 204522253, 195225787, 186737709,
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178956971, 171798692, 165191050, 159072863, 153391690, 148102321, 143165577, 138547333,
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134217728, 130150525, 126322568, 122713352, 119304648, 116080198, 113025456, 110127367,
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107374183, 104755300, 102261127, 99882961, 97612894, 95443718, 93368855, 91382283,
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89478486, 87652394, 85899346, 84215046, 82595525, 81037119, 79536432, 78090315,
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76695845, 75350304, 74051161, 72796056, 71582789, 70409300, 69273667, 68174085,
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67108864, 66076420, 65075263, 64103990, 63161284, 62245903, 61356676, 60492498,
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59652324, 58835169, 58040099, 57266231, 56512728, 55778797, 55063684, 54366675,
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53687092, 53024288, 52377650, 51746594, 51130564, 50529028, 49941481, 49367441,
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48806447, 48258060, 47721859, 47197443, 46684428, 46182445, 45691142, 45210183,
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44739243, 44278014, 43826197, 43383509, 42949673, 42524429, 42107523, 41698712,
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41297763, 40904451, 40518560, 40139882, 39768216, 39403370, 39045158, 38693400,
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38347923, 38008561, 37675152, 37347542, 37025581, 36709123, 36398028, 36092163,
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35791395, 35495598, 35204650, 34918434, 34636834, 34359739, 34087043, 33818641,
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33554432, 33294321, 33038210, 32786010, 32537632, 32292988, 32051995, 31814573,
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31580642, 31350127, 31122952, 30899046, 30678338, 30460761, 30246249, 30034737,
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29826162, 29620465, 29417585, 29217465, 29020050, 28825284, 28633116, 28443493,
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28256364, 28071682, 27889399, 27709467, 27531842, 27356480, 27183338, 27012373,
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26843546, 26676816, 26512144, 26349493, 26188825, 26030105, 25873297, 25718368,
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25565282, 25414008, 25264514, 25116768, 24970741, 24826401, 24683721, 24542671,
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24403224, 24265352, 24129030, 23994231, 23860930, 23729102, 23598722, 23469767,
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23342214, 23216040, 23091223, 22967740, 22845571, 22724695, 22605092, 22486740,
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22369622, 22253717, 22139007, 22025474, 21913099, 21801865, 21691755, 21582751,
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21474837, 21367997, 21262215, 21157475, 21053762, 20951060, 20849356, 20748635,
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20648882, 20550083, 20452226, 20355296, 20259280, 20164166, 20069941, 19976593,
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19884108, 19792477, 19701685, 19611723, 19522579, 19434242, 19346700, 19259944,
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19173962, 19088744, 19004281, 18920561, 18837576, 18755316, 18673771, 18592933,
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18512791, 18433337, 18354562, 18276457, 18199014, 18122225, 18046082, 17970575,
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17895698, 17821442, 17747799, 17674763, 17602325, 17530479, 17459217, 17388532,
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17318417, 17248865, 17179870, 17111424, 17043522, 16976156, 16909321, 16843010,
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16777216
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};
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