Code clean-up for crc.c, lfg.c, log.c, random_see.d, rational.c and tree.c.
[libav.git] / libavutil / crc.c
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1/*
2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
3 *
2912e87a 4 * This file is part of Libav.
b78e7197 5 *
2912e87a 6 * Libav is free software; you can redistribute it and/or
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7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
b78e7197 9 * version 2.1 of the License, or (at your option) any later version.
04d7f601 10 *
2912e87a 11 * Libav is distributed in the hope that it will be useful,
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12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
2912e87a 17 * License along with Libav; if not, write to the Free Software
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18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
e503674c 21#include "config.h"
2ed6f399 22#include "common.h"
e503674c 23#include "bswap.h"
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24#include "crc.h"
25
b250f9c6 26#if CONFIG_HARDCODED_TABLES
3abe5fbd 27#include "crc_data.h"
08cb1950 28#else
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29static struct {
30 uint8_t le;
31 uint8_t bits;
32 uint32_t poly;
33} av_crc_table_params[AV_CRC_MAX] = {
34 [AV_CRC_8_ATM] = { 0, 8, 0x07 },
35 [AV_CRC_16_ANSI] = { 0, 16, 0x8005 },
36 [AV_CRC_16_CCITT] = { 0, 16, 0x1021 },
37 [AV_CRC_32_IEEE] = { 0, 32, 0x04C11DB7 },
38 [AV_CRC_32_IEEE_LE] = { 1, 32, 0xEDB88320 },
39};
40static AVCRC av_crc_table[AV_CRC_MAX][257];
08cb1950 41#endif
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42
43/**
49bd8e4b 44 * Initialize a CRC table.
7d685b48 45 * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
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46 * @param le If 1, the lowest bit represents the coefficient for the highest
47 * exponent of the corresponding polynomial (both for poly and
48 * actual CRC).
49 * If 0, you must swap the CRC parameter and the result of av_crc
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50 * if you need the standard representation (can be simplified in
51 * most cases to e.g. bswap16):
8fc0162a 52 * av_bswap32(crc << (32-bits))
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53 * @param bits number of bits for the CRC
54 * @param poly generator polynomial without the x**bits coefficient, in the
55 * representation as specified by le
e669590a 56 * @param ctx_size size of ctx in bytes
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57 * @return <0 on failure
58 */
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59int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
60{
8b19ae07 61 unsigned i, j;
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62 uint32_t c;
63
425b45d4 64 if (bits < 8 || bits > 32 || poly >= (1LL << bits))
43a80cce 65 return -1;
425b45d4 66 if (ctx_size != sizeof(AVCRC) * 257 && ctx_size != sizeof(AVCRC) * 1024)
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67 return -1;
68
69 for (i = 0; i < 256; i++) {
70 if (le) {
71 for (c = i, j = 0; j < 8; j++)
425b45d4 72 c = (c >> 1) ^ (poly & (-(c & 1)));
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73 ctx[i] = c;
74 } else {
75 for (c = i << 24, j = 0; j < 8; j++)
425b45d4 76 c = (c << 1) ^ ((poly << (32 - bits)) & (((int32_t) c) >> 31));
8fc0162a 77 ctx[i] = av_bswap32(c);
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78 }
79 }
425b45d4 80 ctx[256] = 1;
b250f9c6 81#if !CONFIG_SMALL
425b45d4 82 if (ctx_size >= sizeof(AVCRC) * 1024)
43a80cce 83 for (i = 0; i < 256; i++)
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84 for (j = 0; j < 3; j++)
85 ctx[256 *(j + 1) + i] =
86 (ctx[256 * j + i] >> 8) ^ ctx[ctx[256 * j + i] & 0xFF];
a08d38ee 87#endif
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88
89 return 0;
90}
91
45e3c163 92/**
49bd8e4b 93 * Get an initialized standard CRC table.
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94 * @param crc_id ID of a standard CRC
95 * @return a pointer to the CRC table or NULL on failure
96 */
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97const AVCRC *av_crc_get_table(AVCRCId crc_id)
98{
b250f9c6 99#if !CONFIG_HARDCODED_TABLES
425b45d4 100 if (!av_crc_table[crc_id][FF_ARRAY_ELEMS(av_crc_table[crc_id]) - 1])
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101 if (av_crc_init(av_crc_table[crc_id],
102 av_crc_table_params[crc_id].le,
103 av_crc_table_params[crc_id].bits,
104 av_crc_table_params[crc_id].poly,
105 sizeof(av_crc_table[crc_id])) < 0)
106 return NULL;
107#endif
108 return av_crc_table[crc_id];
109}
110
111/**
49bd8e4b 112 * Calculate the CRC of a block.
89c9ff50 113 * @param crc CRC of previous blocks if any or initial value for CRC
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114 * @return CRC updated with the data from the given block
115 *
116 * @see av_crc_init() "le" parameter
117 */
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118uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
119 const uint8_t *buffer, size_t length)
120{
121 const uint8_t *end = buffer + length;
43a80cce 122
b250f9c6 123#if !CONFIG_SMALL
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124 if (!ctx[256]) {
125 while (((intptr_t) buffer & 3) && buffer < end)
126 crc = ctx[((uint8_t) crc) ^ *buffer++] ^ (crc >> 8);
d468ff0f 127
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128 while (buffer < end - 3) {
129 crc ^= av_le2ne32(*(const uint32_t *) buffer); buffer += 4;
130 crc = ctx[3 * 256 + ( crc & 0xFF)] ^
131 ctx[2 * 256 + ((crc >> 8 ) & 0xFF)] ^
132 ctx[1 * 256 + ((crc >> 16) & 0xFF)] ^
133 ctx[0 * 256 + ((crc >> 24) )];
43a80cce 134 }
d468ff0f 135 }
a08d38ee 136#endif
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137 while (buffer < end)
138 crc = ctx[((uint8_t) crc) ^ *buffer++] ^ (crc >> 8);
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139
140 return crc;
141}
142
143#ifdef TEST
144#undef printf
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145int main(void)
146{
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147 uint8_t buf[1999];
148 int i;
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149 int p[4][3] = { { AV_CRC_32_IEEE_LE, 0xEDB88320, 0x3D5CDD04 },
150 { AV_CRC_32_IEEE , 0x04C11DB7, 0xC0F5BAE0 },
151 { AV_CRC_16_ANSI , 0x8005 , 0x1FBB },
152 { AV_CRC_8_ATM , 0x07 , 0xE3 }
153 };
3abe5fbd 154 const AVCRC *ctx;
43a80cce 155
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156 for (i = 0; i < sizeof(buf); i++)
157 buf[i] = i + i * i;
43a80cce 158
425b45d4 159 for (i = 0; i < 4; i++) {
3abe5fbd 160 ctx = av_crc_get_table(p[i][0]);
425b45d4 161 printf("crc %08X = %X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf)));
43a80cce 162 }
f3635240 163 return 0;
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164}
165#endif