2 * Compute the Adler-32 checksum of a data stream.
3 * This is a modified version based on adler32.c from the zlib library.
5 * Copyright (C) 1995 Mark Adler
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.
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:
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.
26 * Computes the Adler-32 checksum of a data stream
28 * This is a modified version based on adler32.c from the zlib library.
30 * @ingroup lavu_adler32
36 #include "intreadwrite.h"
38 #define BASE 65521L /* largest prime smaller than 65536 */
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);
44 unsigned long av_adler32_update(unsigned long adler
, const uint8_t * buf
,
47 unsigned long s1
= adler
& 0xffff;
48 unsigned long s2
= adler
>> 16;
51 #if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL
52 unsigned len2
= FFMIN((len
-1) & ~7, 23*8);
61 uint64_t v
= AV_RN64(buf
);
64 a1
+= v
&0x00FF00FF00FF00FF;
65 b1
+= (v
>>8)&0x00FF00FF00FF00FF;
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
74 s1
+= ((a1
+b1
)*0x1000100010001)>>48;
75 s2
+= ((((a2
&0xFFFF0000FFFF)+(b2
&0xFFFF0000FFFF)+((a2
>>16)&0xFFFF0000FFFF)+((b2
>>16)&0xFFFF0000FFFF))*0x800000008)>>32)
77 + 2*((b1
*0x1000200030004)>>48)
78 + ((a1
*0x1000100010001)>>48)
79 + 2*((a1
*0x0000100020003)>>48);
81 + 2*((a1
*0x4000300020001)>>48)
82 + ((b1
*0x1000100010001)>>48)
83 + 2*((b1
*0x3000200010000)>>48);
87 while (len
> 4 && s2
< (1U << 31)) {
96 return (s2
<< 16) | s1
;
106 static volatile int checksum
;
108 int main(int argc
, char **argv
)
113 av_log_set_level(AV_LOG_DEBUG
);
115 for (i
= 0; i
< LEN
; i
++)
116 data
[i
] = ((i
* i
) >> 3) + 123 * i
;
118 if (argc
> 1 && !strcmp(argv
[1], "-t")) {
119 for (i
= 0; i
< 1000; i
++) {
121 checksum
= av_adler32_update(1, data
, LEN
);
125 checksum
= av_adler32_update(1, data
, LEN
);
128 av_log(NULL
, AV_LOG_DEBUG
, "%X (expected 50E6E508)\n", checksum
);
129 return checksum
== 0x50e6e508 ? 0 : 1;