Base64编码 c++

#include <stdio.h>
#include <string.h>
#include <assert.h>

typedef unsigned char uint8;
typedef unsigned long uint32;

static uint8 alphabet_map[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static uint8 reverse_map[] =
{
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255, 255, 255, 255,
255, 0, 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, 255, 255, 255, 255, 255,
255, 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, 255, 255, 255, 255, 255
};

uint32 base64_encode(const uint8 *text, uint32 text_len, uint8 *encode)
{
uint32 i, j;
for (i = 0, j = 0; i+3 <= text_len; i+=3)
{
encode[j++] = alphabet_map[text[i]>>2]; //取出第一个字符的前6位并找出对应的结果字符
encode[j++] = alphabet_map[((text[i]<<4)&0x30)|(text[i+1]>>4)]; //将第一个字符的后2位与第二个字符的前4位进行组合并找到对应的结果字符
encode[j++] = alphabet_map[((text[i+1]<<2)&0x3c)|(text[i+2]>>6)]; //将第二个字符的后4位与第三个字符的前2位组合并找出对应的结果字符
encode[j++] = alphabet_map[text[i+2]&0x3f]; //取出第三个字符的后6位并找出结果字符
}

if (i < text_len)
{
uint32 tail = text_len - i;
if (tail == 1)
{
encode[j++] = alphabet_map[text[i]>>2];
encode[j++] = alphabet_map[(text[i]<<4)&0x30];
encode[j++] = '=';
encode[j++] = '=';
}
else //tail==2
{
encode[j++] = alphabet_map[text[i]>>2];
encode[j++] = alphabet_map[((text[i]<<4)&0x30)|(text[i+1]>>4)];
encode[j++] = alphabet_map[(text[i+1]<<2)&0x3c];
encode[j++] = '=';
}
}
return j;
}

uint32 base64_decode(const uint8 *code, uint32 code_len, uint8 *plain)
{
assert((code_len&0x03) == 0); //如果它的条件返回错误，则终止程序执行。4的倍数。

uint32 i, j = 0;
uint8 quad[4];
for (i = 0; i < code_len; i+=4)
{
for (uint32 k = 0; k < 4; k++)
{
quad[k] = reverse_map[code[i+k]];//分组，每组四个分别依次转换为base64表内的十进制数
}

assert(quad[0]<64 && quad[1]<64);

plain[j++] = (quad[0]<<2)|(quad[1]>>4); //取出第一个字符对应base64表的十进制数的前6位与第二个字符对应base64表的十进制数的前2位进行组合

if (quad[2] >= 64)
break;
else if (quad[3] >= 64)
{
plain[j++] = (quad[1]<<4)|(quad[2]>>2); //取出第二个字符对应base64表的十进制数的后4位与第三个字符对应base64表的十进制数的前4位进行组合
break;
}
else
{
plain[j++] = (quad[1]<<4)|(quad[2]>>2);
plain[j++] = (quad[2]<<6)|quad[3];//取出第三个字符对应base64表的十进制数的后2位与第4个字符进行组合
}
}
return j;
}

/*int main(void)
{
char input[256];
while (true){
printf("Please input string: ");
scanf("%s", input);
uint8 *text = (uint8 *)input;
uint32 text_len = (uint32)strlen((char *)text);
uint8 buffer[1024], buffer2[4096];
uint32 size = base64_encode(text, text_len, buffer2);
buffer2[size] = 0;
printf("%s\n", buffer2);

size = base64_decode(buffer2, size, buffer);
buffer[size] = 0;
printf("%s\n", buffer);

}
return 0;
}*/
//编码
int main(void)
{
char input[256];
while (true){
printf("Please input what you want to decode: ");
scanf("%s", input);
uint8 *text = (uint8 *)input;
uint32 text_len = (uint32)strlen((char *)text);
uint8 buffer[1024],buffer2[4096];

uint32 size = base64_decode(text, text_len, buffer);
buffer[size] = 0;
printf("Decoded content: %s\n", buffer);
size = base64_encode(buffer, size, buffer2);
buffer2[size] = 0;
printf("Confirmation of the original content: %s\n", buffer2);
}
return 0;
}
//解码