git ssb

1
/*
2
3
	This code is public domain software.
4
5
*/
6
7
#include "base64.h"
8
9
#include <stdlib.h>
10
#include <string.h>
11
#include <errno.h>
12
13
14
//  single base64 character conversion
15
//
16
static int POS(char c)
17
{
18
	if (c>='A' && c<='Z') return c - 'A';
19
	if (c>='a' && c<='z') return c - 'a' + 26;
20
	if (c>='0' && c<='9') return c - '0' + 52;
21
	if (c == '+') return 62;
22
	if (c == '/') return 63;
23
	if (c == '=') return -1;
24
	return -2;
25
}
26
27
//  base64 decoding
28
//
29
//  s:	     base64 string
30
//  str_len  size of the base64 string
31
//  data:    output buffer for decoded data
32
//  data_len expected size of decoded data
33
//  return:  0 on success, -1 on failure
34
//
35
int base64_decode(const char* s, size_t str_len, void *data, size_t data_len)
36
{
37
	const char *p, *str_end;
38
	unsigned char *q, *end;
39
	int n[4] = { 0, 0, 0, 0 };
40
41
	if (str_len % 4) { errno = EBADMSG; return -1; }
42
	q = (unsigned char*) data;
43
	end = q + data_len;
44
	str_end = s + str_len;
45
46
	for (p = s; p < str_end; ) {
47
		n[0] = POS(*p++);
48
		n[1] = POS(*p++);
49
		n[2] = POS(*p++);
50
		n[3] = POS(*p++);
51
52
		if (n[0] == -2 || n[1] == -2 || n[2] == -2 || n[3] == -2)
53
			{ errno = EBADMSG; return -1; }
54
55
		if (n[0] == -1 || n[1] == -1)
56
			{ errno = EBADMSG; return -1; }
57
58
		if (n[2] == -1 && n[3] != -1)
59
			{ errno = EBADMSG; return -1; }
60
61
		if (q >= end) { errno = EMSGSIZE; return -1; }
62
		q[0] = (n[0] << 2) + (n[1] >> 4);
63
		if (n[2] != -1) {
64
			if (q+1 >= end) { errno = EMSGSIZE; return -1; }
65
			q[1] = ((n[1] & 15) << 4) + (n[2] >> 2);
66
		}
67
		if (n[3] != -1) {
68
			if (q+2 >= end) { errno = EMSGSIZE; return -1; }
69
			q[2] = ((n[2] & 3) << 6) + n[3];
70
		}
71
		q += 3;
72
	}
73
74
	return 0;
75
}
76
77
int base64_encode(const void* buf, size_t size, char *str, size_t out_size) {
78
	static const char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
79
80
	char* p = str;
81
	const unsigned char* q = (const unsigned char*) buf;
82
	size_t i = 0;
83
84
	if ((size+3)*4/3 + 1 > out_size) {
85
		errno = EMSGSIZE;
86
		return -1;
87
	}
88
89
	while (i < size) {
90
		int c = q[i++];
91
		c *= 256;
92
		if (i < size)
93
            c += q[i];
94
		i++;
95
96
		c *= 256;
97
		if (i < size)
98
            c += q[i];
99
		i++;
100
101
		*p++ = base64[(c & 0x00fc0000) >> 18];
102
		*p++ = base64[(c & 0x0003f000) >> 12];
103
104
		if (i > size + 1)
105
			*p++ = '=';
106
		else
107
			*p++ = base64[(c & 0x00000fc0) >> 6];
108
109
		if (i > size)
110
			*p++ = '=';
111
		else
112
			*p++ = base64[c & 0x0000003f];
113
	}
114
115
	*p = 0;
116
117
	return 0;
118
}
119