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1 | /* |
2 | * Compute the Adler-32 checksum of a data stream. | |
3 | * This is a modified version based on adler32.c from the zlib library. | |
4 | * | |
5 | * Copyright (C) 1995 Mark Adler | |
6 | * | |
7 | * This software is provided 'as-is', without any express or implied | |
8 | * warranty. In no event will the authors be held liable for any damages | |
9 | * arising from the use of this software. | |
10 | * | |
11 | * Permission is granted to anyone to use this software for any purpose, | |
12 | * including commercial applications, and to alter it and redistribute it | |
13 | * freely, subject to the following restrictions: | |
14 | * | |
15 | * 1. The origin of this software must not be misrepresented; you must not | |
16 | * claim that you wrote the original software. If you use this software | |
17 | * in a product, an acknowledgment in the product documentation would be | |
18 | * appreciated but is not required. | |
19 | * 2. Altered source versions must be plainly marked as such, and must not be | |
20 | * misrepresented as being the original software. | |
21 | * 3. This notice may not be removed or altered from any source distribution. | |
22 | */ | |
23 | ||
24 | /** | |
25 | * @file | |
26 | * Computes the Adler-32 checksum of a data stream | |
27 | * | |
28 | * This is a modified version based on adler32.c from the zlib library. | |
29 | * @author Mark Adler | |
30 | * @ingroup lavu_adler32 | |
31 | */ | |
32 | ||
33 | #include "config.h" | |
34 | #include "adler32.h" | |
35 | #include "common.h" | |
36 | #include "intreadwrite.h" | |
37 | ||
38 | #define BASE 65521L /* largest prime smaller than 65536 */ | |
39 | ||
40 | #define DO1(buf) { s1 += *buf++; s2 += s1; } | |
41 | #define DO4(buf) DO1(buf); DO1(buf); DO1(buf); DO1(buf); | |
42 | #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf); | |
43 | ||
44 | unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf, | |
45 | unsigned int len) | |
46 | { | |
47 | unsigned long s1 = adler & 0xffff; | |
48 | unsigned long s2 = adler >> 16; | |
49 | ||
50 | while (len > 0) { | |
51 | #if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL | |
52 | unsigned len2 = FFMIN((len-1) & ~7, 23*8); | |
53 | if (len2) { | |
54 | uint64_t a1= 0; | |
55 | uint64_t a2= 0; | |
56 | uint64_t b1= 0; | |
57 | uint64_t b2= 0; | |
58 | len -= len2; | |
59 | s2 += s1*len2; | |
60 | while (len2 >= 8) { | |
61 | uint64_t v = AV_RN64(buf); | |
62 | a2 += a1; | |
63 | b2 += b1; | |
64 | a1 += v &0x00FF00FF00FF00FF; | |
65 | b1 += (v>>8)&0x00FF00FF00FF00FF; | |
66 | len2 -= 8; | |
67 | buf+=8; | |
68 | } | |
69 | ||
70 | //We combine the 8 interleaved adler32 checksums without overflows | |
71 | //Decreasing the number of iterations would allow below code to be | |
72 | //simplified but would likely be slower due to the fewer iterations | |
73 | //of the inner loop | |
74 | s1 += ((a1+b1)*0x1000100010001)>>48; | |
75 | s2 += ((((a2&0xFFFF0000FFFF)+(b2&0xFFFF0000FFFF)+((a2>>16)&0xFFFF0000FFFF)+((b2>>16)&0xFFFF0000FFFF))*0x800000008)>>32) | |
76 | #if HAVE_BIGENDIAN | |
77 | + 2*((b1*0x1000200030004)>>48) | |
78 | + ((a1*0x1000100010001)>>48) | |
79 | + 2*((a1*0x0000100020003)>>48); | |
80 | #else | |
81 | + 2*((a1*0x4000300020001)>>48) | |
82 | + ((b1*0x1000100010001)>>48) | |
83 | + 2*((b1*0x3000200010000)>>48); | |
84 | #endif | |
85 | } | |
86 | #else | |
87 | while (len > 4 && s2 < (1U << 31)) { | |
88 | DO4(buf); | |
89 | len -= 4; | |
90 | } | |
91 | #endif | |
92 | DO1(buf); len--; | |
93 | s1 %= BASE; | |
94 | s2 %= BASE; | |
95 | } | |
96 | return (s2 << 16) | s1; | |
97 | } | |
98 | ||
99 | #ifdef TEST | |
100 | // LCOV_EXCL_START | |
101 | #include <string.h> | |
102 | #include "log.h" | |
103 | #include "timer.h" | |
104 | #define LEN 7001 | |
105 | ||
106 | static volatile int checksum; | |
107 | ||
108 | int main(int argc, char **argv) | |
109 | { | |
110 | int i; | |
111 | char data[LEN]; | |
112 | ||
113 | av_log_set_level(AV_LOG_DEBUG); | |
114 | ||
115 | for (i = 0; i < LEN; i++) | |
116 | data[i] = ((i * i) >> 3) + 123 * i; | |
117 | ||
118 | if (argc > 1 && !strcmp(argv[1], "-t")) { | |
119 | for (i = 0; i < 1000; i++) { | |
120 | START_TIMER; | |
121 | checksum = av_adler32_update(1, data, LEN); | |
122 | STOP_TIMER("adler"); | |
123 | } | |
124 | } else { | |
125 | checksum = av_adler32_update(1, data, LEN); | |
126 | } | |
127 | ||
128 | av_log(NULL, AV_LOG_DEBUG, "%X (expected 50E6E508)\n", checksum); | |
129 | return checksum == 0x50e6e508 ? 0 : 1; | |
130 | } | |
131 | // LCOV_EXCL_STOP | |
132 | #endif |