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
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
|
/*
** 2014-06-13
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** This SQLite extension implements SQL compression functions
** compress() and uncompress() using ZLIB.
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <zlib.h>
/*
** Implementation of the "compress(X)" SQL function. The input X is
** compressed using zLib and the output is returned.
**
** The output is a BLOB that begins with a variable-length integer that
** is the input size in bytes (the size of X before compression). The
** variable-length integer is implemented as 1 to 5 bytes. There are
** seven bits per integer stored in the lower seven bits of each byte.
** More significant bits occur first. The most significant bit (0x80)
** is a flag to indicate the end of the integer.
**
** This function, SQLAR, and ZIP all use the same "deflate" compression
** algorithm, but each is subtly different:
**
** * ZIP uses raw deflate.
**
** * SQLAR uses the "zlib format" which is raw deflate with a two-byte
** algorithm-identification header and a four-byte checksum at the end.
**
** * This utility uses the "zlib format" like SQLAR, but adds the variable-
** length integer uncompressed size value at the beginning.
**
** This function might be extended in the future to support compression
** formats other than deflate, by providing a different algorithm-id
** mark following the variable-length integer size parameter.
*/
static void compressFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
const unsigned char *pIn;
unsigned char *pOut;
unsigned int nIn;
unsigned long int nOut;
unsigned char x[8];
int rc;
int i, j;
pIn = sqlite3_value_blob(argv[0]);
nIn = sqlite3_value_bytes(argv[0]);
nOut = 13 + nIn + (nIn+999)/1000;
pOut = sqlite3_malloc( nOut+5 );
for(i=4; i>=0; i--){
x[i] = (nIn >> (7*(4-i)))&0x7f;
}
for(i=0; i<4 && x[i]==0; i++){}
for(j=0; i<=4; i++, j++) pOut[j] = x[i];
pOut[j-1] |= 0x80;
rc = compress(&pOut[j], &nOut, pIn, nIn);
if( rc==Z_OK ){
sqlite3_result_blob(context, pOut, nOut+j, sqlite3_free);
}else{
sqlite3_free(pOut);
}
}
/*
** Implementation of the "uncompress(X)" SQL function. The argument X
** is a blob which was obtained from compress(Y). The output will be
** the value Y.
*/
static void uncompressFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
const unsigned char *pIn;
unsigned char *pOut;
unsigned int nIn;
unsigned long int nOut;
int rc;
int i;
pIn = sqlite3_value_blob(argv[0]);
nIn = sqlite3_value_bytes(argv[0]);
nOut = 0;
for(i=0; i<nIn && i<5; i++){
nOut = (nOut<<7) | (pIn[i]&0x7f);
if( (pIn[i]&0x80)!=0 ){ i++; break; }
}
pOut = sqlite3_malloc( nOut+1 );
rc = uncompress(pOut, &nOut, &pIn[i], nIn-i);
if( rc==Z_OK ){
sqlite3_result_blob(context, pOut, nOut, sqlite3_free);
}else{
sqlite3_free(pOut);
}
}
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_compress_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
(void)pzErrMsg; /* Unused parameter */
rc = sqlite3_create_function(db, "compress", 1,
SQLITE_UTF8 | SQLITE_INNOCUOUS,
0, compressFunc, 0, 0);
if( rc==SQLITE_OK ){
rc = sqlite3_create_function(db, "uncompress", 1,
SQLITE_UTF8 | SQLITE_INNOCUOUS | SQLITE_DETERMINISTIC,
0, uncompressFunc, 0, 0);
}
return rc;
}
|
