Code clean-up for crc.c, lfg.c, log.c, random_see.d, rational.c and tree.c.
[libav.git] / libavutil / crc.c
1 /*
2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
3 *
4 * This file is part of Libav.
5 *
6 * Libav is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * Libav is distributed in the hope that it will be useful,
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
17 * License along with Libav; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21 #include "config.h"
22 #include "common.h"
23 #include "bswap.h"
24 #include "crc.h"
25
26 #if CONFIG_HARDCODED_TABLES
27 #include "crc_data.h"
28 #else
29 static 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 };
40 static AVCRC av_crc_table[AV_CRC_MAX][257];
41 #endif
42
43 /**
44 * Initialize a CRC table.
45 * @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
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
50 * if you need the standard representation (can be simplified in
51 * most cases to e.g. bswap16):
52 * av_bswap32(crc << (32-bits))
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
56 * @param ctx_size size of ctx in bytes
57 * @return <0 on failure
58 */
59 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
60 {
61 unsigned i, j;
62 uint32_t c;
63
64 if (bits < 8 || bits > 32 || poly >= (1LL << bits))
65 return -1;
66 if (ctx_size != sizeof(AVCRC) * 257 && ctx_size != sizeof(AVCRC) * 1024)
67 return -1;
68
69 for (i = 0; i < 256; i++) {
70 if (le) {
71 for (c = i, j = 0; j < 8; j++)
72 c = (c >> 1) ^ (poly & (-(c & 1)));
73 ctx[i] = c;
74 } else {
75 for (c = i << 24, j = 0; j < 8; j++)
76 c = (c << 1) ^ ((poly << (32 - bits)) & (((int32_t) c) >> 31));
77 ctx[i] = av_bswap32(c);
78 }
79 }
80 ctx[256] = 1;
81 #if !CONFIG_SMALL
82 if (ctx_size >= sizeof(AVCRC) * 1024)
83 for (i = 0; i < 256; i++)
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];
87 #endif
88
89 return 0;
90 }
91
92 /**
93 * Get an initialized standard CRC table.
94 * @param crc_id ID of a standard CRC
95 * @return a pointer to the CRC table or NULL on failure
96 */
97 const AVCRC *av_crc_get_table(AVCRCId crc_id)
98 {
99 #if !CONFIG_HARDCODED_TABLES
100 if (!av_crc_table[crc_id][FF_ARRAY_ELEMS(av_crc_table[crc_id]) - 1])
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 /**
112 * Calculate the CRC of a block.
113 * @param crc CRC of previous blocks if any or initial value for CRC
114 * @return CRC updated with the data from the given block
115 *
116 * @see av_crc_init() "le" parameter
117 */
118 uint32_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;
122
123 #if !CONFIG_SMALL
124 if (!ctx[256]) {
125 while (((intptr_t) buffer & 3) && buffer < end)
126 crc = ctx[((uint8_t) crc) ^ *buffer++] ^ (crc >> 8);
127
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) )];
134 }
135 }
136 #endif
137 while (buffer < end)
138 crc = ctx[((uint8_t) crc) ^ *buffer++] ^ (crc >> 8);
139
140 return crc;
141 }
142
143 #ifdef TEST
144 #undef printf
145 int main(void)
146 {
147 uint8_t buf[1999];
148 int i;
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 };
154 const AVCRC *ctx;
155
156 for (i = 0; i < sizeof(buf); i++)
157 buf[i] = i + i * i;
158
159 for (i = 0; i < 4; i++) {
160 ctx = av_crc_get_table(p[i][0]);
161 printf("crc %08X = %X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf)));
162 }
163 return 0;
164 }
165 #endif