adler32.cpp
1.15 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
// adler32.cpp - written and placed in the public domain by Wei Dai
#include "pch.h"
#include "adler32.h"
NAMESPACE_BEGIN(CryptoPP)
void Adler32::Update(const byte *input, size_t length)
{
const unsigned long BASE = 65521;
unsigned long s1 = m_s1;
unsigned long s2 = m_s2;
if (length % 8 != 0)
{
do
{
s1 += *input++;
s2 += s1;
length--;
} while (length % 8 != 0);
if (s1 >= BASE)
s1 -= BASE;
s2 %= BASE;
}
while (length > 0)
{
s1 += input[0]; s2 += s1;
s1 += input[1]; s2 += s1;
s1 += input[2]; s2 += s1;
s1 += input[3]; s2 += s1;
s1 += input[4]; s2 += s1;
s1 += input[5]; s2 += s1;
s1 += input[6]; s2 += s1;
s1 += input[7]; s2 += s1;
length -= 8;
input += 8;
if (s1 >= BASE)
s1 -= BASE;
if (length % 0x8000 == 0)
s2 %= BASE;
}
assert(s1 < BASE);
assert(s2 < BASE);
m_s1 = (word16)s1;
m_s2 = (word16)s2;
}
void Adler32::TruncatedFinal(byte *hash, size_t size)
{
ThrowIfInvalidTruncatedSize(size);
switch (size)
{
default:
hash[3] = byte(m_s1);
case 3:
hash[2] = byte(m_s1 >> 8);
case 2:
hash[1] = byte(m_s2);
case 1:
hash[0] = byte(m_s2 >> 8);
case 0:
;
}
Reset();
}
NAMESPACE_END