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
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
|
/*
* delta.h: headers for delta functionality
*
* Adapted from GIT for Bazaar by
* John Arbash Meinel <john@arbash-meinel.com> (C) 2009
*
* This code is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef DELTA_H
#define DELTA_H
/* opaque object for delta index */
struct delta_index;
struct source_info {
const void *buf; /* Pointer to the beginning of source data */
unsigned long size; /* Total length of source data */
unsigned long agg_offset; /* Start of source data as part of the
aggregate source */
};
/*
* create_delta_index: compute index data from given buffer
*
* This returns a pointer to a struct delta_index that should be passed to
* subsequent create_delta() calls, or to free_delta_index(). A NULL pointer
* is returned on failure. The given buffer must not be freed nor altered
* before free_delta_index() is called. The returned pointer must be freed
* using free_delta_index().
*/
extern struct delta_index *
create_delta_index(const struct source_info *src,
struct delta_index *old);
/*
* create_delta_index_from_delta: compute index data from given buffer
*
* This returns a pointer to a struct delta_index that should be passed to
* subsequent create_delta() calls, or to free_delta_index(). A NULL pointer
* is returned on failure.
* The bytes must be in the form of a delta structure, as generated by
* create_delta(). The generated index will only index the insert bytes, and
* not any of the control structures.
*/
extern struct delta_index *
create_delta_index_from_delta(const struct source_info *delta,
struct delta_index *old);
/*
* free_delta_index: free the index created by create_delta_index()
*
* Given pointer must be what create_delta_index() returned, or NULL.
*/
extern void free_delta_index(struct delta_index *index);
/*
* sizeof_delta_index: returns memory usage of delta index
*
* Given pointer must be what create_delta_index() returned, or NULL.
*/
extern unsigned long sizeof_delta_index(struct delta_index *index);
/*
* create_delta: create a delta from given index for the given buffer
*
* This function may be called multiple times with different buffers using
* the same delta_index pointer. If max_delta_size is non-zero and the
* resulting delta is to be larger than max_delta_size then NULL is returned.
* On success, a non-NULL pointer to the buffer with the delta data is
* returned and *delta_size is updated with its size. The returned buffer
* must be freed by the caller.
*/
extern void *
create_delta(const struct delta_index *index,
const void *buf, unsigned long bufsize,
unsigned long *delta_size, unsigned long max_delta_size);
/* the smallest possible delta size is 3 bytes
* Target size, Copy command, Copy length
*/
#define DELTA_SIZE_MIN 3
/*
* This must be called twice on the delta data buffer, first to get the
* expected source buffer size, and again to get the target buffer size.
*/
static unsigned long
get_delta_hdr_size(unsigned char **datap, const unsigned char *top)
{
unsigned char *data = *datap;
unsigned char cmd;
unsigned long size = 0;
int i = 0;
do {
cmd = *data++;
size |= (cmd & ~0x80) << i;
i += 7;
} while (cmd & 0x80 && data < top);
*datap = data;
return size;
}
#endif
|