/
base64.h
143 lines (137 loc) · 3.65 KB
/
base64.h
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/*
In rfc2045
Value Encoding Value Encoding Value Encoding Value Encoding
0 A 17 R 34 i 51 z
1 B 18 S 35 j 52 0
2 C 19 T 36 k 53 1
3 D 20 U 37 l 54 2
4 E 21 V 38 m 55 3
5 F 22 W 39 n 56 4
6 G 23 X 40 o 57 5
7 H 24 Y 41 p 58 6
8 I 25 Z 42 q 59 7
9 J 26 a 43 r 60 8
10 K 27 b 44 s 61 9
11 L 28 c 45 t 62 +
12 M 29 d 46 u 63 /
13 N 30 e 47 v
14 O 31 f 48 w (pad) =
15 P 32 g 49 x
16 Q 33 h 50 y
*/
#include <stdlib.h>
#include <string.h>
char *char_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
char char_table_flip[128];
char *error_table[] = {
"OK",
"Length is not 4 or 4's", // 1
"Empty string", // 2
"not enough memory", // 3
};
char * base64encode(void * s, int len)
{
// printf("encode '%s'(%d)\n", s, len);
if (len <= 0)
{
return NULL;
}
int n;
if (len % 3 == 0)
{
n = len / 3;
} else {
n = len / 3 + 1;
}
char *ret = malloc(sizeof(char)*n*4+1); // string must have an end
if (ret == NULL)
{
return NULL;
}
// expand 3 bytes to 4 bytes
char *sp = (char *)s;
int i;
for (i = 0; i < n; ++i)
{
unsigned a0 = sp[i*3];
unsigned a1 = i*3+1 >= len ? 0 : sp[i*3+1]; // 0 for padding
unsigned a2 = i*3+2 >= len ? 0 : sp[i*3+2];
// printf("('%c', 0x%x) ('%c', 0x%x) ('%c', 0x%x)\n", a0, a0, a1, a1, a2, a2);
int i0, i1, i2, i3;
char b0, b1, b2, b3;
i0 = a0 >> 2;
i1 = ((a0 & 0x3) << 4) | (a1 >> 4);
i2 = ((a1 & 0xF) << 2) | (a2 >> 6);
i3 = a2 & 0x3F;
ret[i*4+0] = b0 = char_table[i0];
ret[i*4+1] = b1 = char_table[i1];
ret[i*4+2] = b2 = char_table[i2];
ret[i*4+3] = b3 = char_table[i3];
// ret[i*4+4] = 0;
// printf("('%c',%d) ('%c',%d) ('%c',%d) ('%c',%d)\n", b0, i0, b1, i1, b2, i2, b3, i3);
// printf("%s\n", ret+i*4);
// 如果最后剩下两个输入数据，在编码结果后加1个“=”；
// 如果最后剩下一个输入数据，编码结果后加2个“=”；
if (i*3+1 >= len)
{
ret[i*4+2] = '=';
ret[i*4+3] = '=';
}
else if (i*3+2 >= len)
{
ret[i*4+3] = '=';
}
}
ret[i*4] = 0;
return ret;
}
void init_char_table_flip()
{
for (int i = 0; i < strlen(char_table); ++i)
{
char_table_flip[char_table[i]] = i;
}
char_table_flip['='] = 0;
}
// return error code, 0 is OK
int base64decode(char *src, void **data_p, int *size_p)
{
int len = strlen(src);
if (len == 0) {
return 2;
}
if (len % 4 != 0)
{
return 1;
}
int size = len/4*3;
char *ret = malloc(sizeof(char)*size);
if (ret == NULL)
{
return 3;
}
init_char_table_flip();
// assume no padding
for (int i = 0; i < len/4; ++i)
{
unsigned a0 = char_table_flip[ src[i*4+0] ];
unsigned a1 = char_table_flip[ src[i*4+1] ];
unsigned a2 = char_table_flip[ src[i*4+2] ];
unsigned a3 = char_table_flip[ src[i*4+3] ];
char b0, b1, b2;
ret[i*3+0] = b0 = (char) (a0 << 2) | a1 >> 4;
ret[i*3+1] = b1 = (char) ((a1 & 0xF) << 4) | (a2 >> 2);
ret[i*3+2] = b2 = (char) ((a2 & 0x3) << 6) | a3;
}
*data_p = ret;
if (src[len-2] == '=') // two =
{
size -= 2;
}
if (src[len-1] == '=') // only one =
{
size -= 1;
}
*size_p = size;
return 0;
}