-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathrollsum.h
More file actions
87 lines (73 loc) · 2.52 KB
/
rollsum.h
File metadata and controls
87 lines (73 loc) · 2.52 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
78
79
80
81
82
83
84
85
86
87
/*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*-
*
* rollsum -- the librsync rolling checksum
*
* Copyright (C) 2003 by Donovan Baarda <[email protected]>
* based on work, Copyright (C) 2000, 2001 by Martin Pool <[email protected]>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef _ROLLSUM_H_
#define _ROLLSUM_H_
#ifdef WIN32
// disable type cast warnings for original librsync code
#pragma warning(disable:4267)
#endif
namespace librsync
{
#include <stddef.h>
#include <stdint.h>
/* We should make this something other than zero to improve the
* checksum algorithm: tridge suggests a prime number. */
#define ROLLSUM_CHAR_OFFSET 31
/* the Rollsum struct type*/
/** \private */
typedef struct _Rollsum {
size_t count; /* count of bytes included in sum */
uint_fast16_t s1; /* s1 part of sum */
uint_fast16_t s2; /* s2 part of sum */
} Rollsum;
void RollsumUpdate(Rollsum *sum, const unsigned char *buf, size_t len);
/* static inline implementations of simple routines */
static inline void RollsumInit(Rollsum *sum)
{
sum->count = sum->s1 = sum->s2 = 0;
}
static inline void RollsumRotate(Rollsum *sum, unsigned char out, unsigned char in)
{
sum->s1 += in - out;
sum->s2 += sum->s1 - sum->count * (out + ROLLSUM_CHAR_OFFSET);
}
static inline void RollsumRollin(Rollsum *sum, unsigned char in)
{
sum->s1 += in + ROLLSUM_CHAR_OFFSET;
sum->s2 += sum->s1;
sum->count++;
}
static inline void RollsumRollout(Rollsum *sum, unsigned char out)
{
sum->s1 -= out + ROLLSUM_CHAR_OFFSET;
sum->s2 -= sum->count * (out + ROLLSUM_CHAR_OFFSET);
sum->count--;
}
static inline uint32_t RollsumDigest(Rollsum *sum)
{
return ((uint32_t)sum->s2 << 16) | ((uint32_t)sum->s1 & 0xffff);
}
};
#ifdef WIN32
#pragma warning(default:4267)
#endif
#endif /* _ROLLSUM_H_ */