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
|
#include <stddef.h>
#include <util/alloc.h>
#include <util/base64.h>
static size_t div_up(size_t dividend, size_t divisor) {
return dividend / divisor + (dividend % divisor != 0);
}
static const char base64_alphabet[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
size_t gv_base64_size(size_t source_size) { return div_up(source_size, 3) * 4; }
char *gv_base64(const unsigned char *source, size_t size) {
size_t buf_i = 0;
char *buf = gv_alloc(gv_base64_size(size) + 1);
for (size_t data_i = 0; data_i < size; data_i += 3) {
unsigned char d0 = source[data_i];
int v = (d0 & 0xFC) >> 2; // 1111_1100
buf[buf_i++] = base64_alphabet[v];
unsigned char d1 = data_i + 1 < size ? source[data_i + 1] : 0;
v = (d0 & 0x03) << 4 // 0000_0011
| (d1 & 0xF0) >> 4; // 1111_0000
buf[buf_i++] = base64_alphabet[v];
if (size <= data_i + 1) {
goto end;
}
unsigned char d2 = data_i + 2 < size ? source[data_i + 2] : 0;
v = (d1 & 0x0F) << 2 // 0000_1111
| (d2 & 0xC0) >> 6; // 1100_0000
buf[buf_i++] = base64_alphabet[v];
if (size <= data_i + 2) {
goto end;
}
v = d2 & 0x3F; // 0011_1111
buf[buf_i++] = base64_alphabet[v];
}
end:
while (buf_i % 4 != 0) {
buf[buf_i++] = base64_alphabet[64];
}
// Write a string terminator. This is not strictly necessary, but is a
// backstop against callers who do not use `gv_base64_size` and assume they
// can e.g. `fputs` the returned data.
buf[buf_i++] = '\0';
return buf;
}
|
