Base64是一种用于将二进制数据编码为文本的编码方式。它将任意的二进制数据通过编码转换成由64个字符组成的ASCII字符串，这些字符包括大写字母、小写字母、数字和两个额外的符号。Base64编码后的字符串通常用于在文本协议中传输数据，例如电子邮件的传输编码、在URL中传递数据、在数据的存储和传输中避免乱码等场景。
Base64编码的特点包括：
可读性： 编码后的字符串可以由人类读取和处理，由于使用了ASCII字符集，能够避免一些特定编码的问题。
长度增加： 编码后的长度大约是原始数据的4/3倍，这是因为每3个字节的数据编码成4个Base64字符。
无损转换： Base64编码和解码是无损的，可以完全还原原始的二进制数据。
Base64编码使用的字符集包括：
大写字母 A-Z (26个字符)
小写字母 a-z (26个字符)
数字 0-9 (10个字符)
符号 + 和 /
总共64个字符，因此得名Base64
base64测试
我们对如下三种数据进行编解码测试：
"hello world abcdefg"
"hello ,,,,,,,,, world"
{0x81, 0x82, 0x83, 0x84}
#include
#include
#include
/* Base64编码映射表 */
conST char *const Base64Table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
int Base64Encode(const unsigned char *Bindata, int Binlen, char *const Base64Buf);
int Base64Decode(const char *Base64Buf, unsigned char *const Bindata);
int main(int argc, char **argv)
{
unsigned char base64_buf[128] = {0};
unsigned char bin_buf[128] = {0};
int base64_len = 0;
int bin_len = 0;
printf("\\n=================================test1==========================================\\n");
char *test_data1 = "hello world abcdefg";
printf("src data str = %s, src_data_len = %ld\\n", test_data1, strlen(test_data1));
memset(base64_buf, 0x00, sizeof(base64_buf));
memset(bin_buf, 0x00, sizeof(bin_buf));
base64_len = Base64Encode(test_data1, strlen(test_data1), base64_buf);
printf("after base64_encode, base64_buf = %s, base64_len = %d\\n", base64_buf, base64_len);
bin_len = Base64Decode(base64_buf, bin_buf);
printf("after base64_decode bin_buf = %s, bin_len = %d\\r\\n", bin_buf, bin_len);
printf("\\n=================================test2==========================================\\n");
char *test_data2 = "hello ,,,,,,,,, world";
printf("src data str = %s, src_data_len = %ld\\n", test_data2, strlen(test_data2));
memset(base64_buf, 0x00, sizeof(base64_buf));
memset(bin_buf, 0x00, sizeof(bin_buf));
base64_len = Base64Encode(test_data2, strlen(test_data2), base64_buf);
printf("after base64_encode, base64_buf = %s, base64_len = %d\\n", base64_buf, base64_len);
bin_len = Base64Decode(base64_buf, bin_buf);
printf("after base64_decode bin_buf = %s, bin_len = %d\\r\\n", bin_buf, bin_len);
printf("\\n=================================test3==========================================\\n");
unsigned char test_data3[4] = {0x81, 0x82, 0x83, 0x84};
printf("src data hex = ");
for (int i = 0; i < sizeof(test_data3); i++)
{
printf("%#02x ", test_data3[i]);
}
printf(" src_data_len = %ld\\n", sizeof(test_data3));
memset(base64_buf, 0x00, sizeof(base64_buf));
memset(bin_buf, 0x00, sizeof(bin_buf));
base64_len = Base64Encode(test_data3, sizeof(test_data3), base64_buf);
printf("after base64_encode, base64_buf = %s, base64_len = %d\\n", base64_buf, base64_len);
bin_len = Base64Decode(base64_buf, bin_buf);
printf("after base64_decode, data hex = ");
for (int i = 0; i < bin_len; i++)
{
printf("%#02x ", bin_buf[i]);
}
printf(" bin_len = %d\\n", bin_len);
printf("\\n");
return 0;
}
/********************************************************
*功能描述：Base64编码
*输入参数: Bindata：原始bin数据
Binlen：原始 bin数据长度
*输出参数：Base64Buf：base64编码数据
*返 回 值：base64编码后数据长度
*********************************************************/
int Base64Encode(const unsigned char *Bindata, int Binlen, char *const Base64Buf)
{
unsigned char s8CharIndex = 0;
int i=0, Len=0;
for ((i=0,Len=0); i3)
{
s8CharIndex = (Bindata[i]>>2);
s8CharIndex &= (unsigned char)0x3F;
Base64Buf[Len++] = Base64Table[(int)s8CharIndex];
s8CharIndex = ((unsigned char)(Bindata[i]<<4)) & ((unsigned char)0x30);
if ((i+1) >= Binlen)
{
Base64Buf[Len++] = Base64Table[(int)s8CharIndex];
Base64Buf[Len++] = '=';
Base64Buf[Len++] = '=';
break;
}
s8CharIndex |= ((unsigned char)(Bindata[i+1]>>4)) & ((unsigned char)0x0F);
Base64Buf[Len++] = Base64Table[(int)s8CharIndex];
s8CharIndex = ((unsigned char)(Bindata[i+1]<<2)) & ((unsigned char)0x3C);
if ((i+2) >= Binlen)
{
Base64Buf[Len++] = Base64Table[(int)s8CharIndex];
Base64Buf[Len++] = '=';
break;
}
s8CharIndex |= ((unsigned char)(Bindata[i+2]>>6) & ((unsigned char)0x03));
Base64Buf[Len++] = Base64Table[(int)s8CharIndex];
s8CharIndex = ((unsigned char)Bindata[i+2]) & ((unsigned char)0x3F) ;
Base64Buf[Len++] = Base64Table[(int)s8CharIndex];
}
return Len;
}
/********************************************************
*功能描述：Base64解码
*输入参数: Base64Buf：base64编码数据
*输出参数：Bindata：解码后bin数据
*返 回 值：解码后bin数据长度
*********************************************************/
int Base64Decode(const char *Base64Buf, unsigned char *const Bindata)
{
int i, Len=0;
unsigned char s8CharIndex = 0;
unsigned char temp[4] = {0};
for ((i=0,Len=0); Base64Buf[i]!='\\0'; i+=4)
{
memset(temp, 0xFF, sizeof(temp));
for (s8CharIndex=0; s8CharIndex<64; s8CharIndex++)
{
if (Base64Table[s8CharIndex] == Base64Buf[i])
temp[0]= s8CharIndex;
}
for (s8CharIndex=0; s8CharIndex<64; s8CharIndex++)
{
if (Base64Table[s8CharIndex] == Base64Buf[i+1])
temp[1]= s8CharIndex;
}
for (s8CharIndex=0; s8CharIndex<64; s8CharIndex++)
{
if (Base64Table[s8CharIndex] == Base64Buf[i+2])
temp[2]= s8CharIndex;
}
for (s8CharIndex=0; s8CharIndex<64; s8CharIndex++)
{
if (Base64Table[s8CharIndex] == Base64Buf[i+3])
temp[3]= s8CharIndex;
}
if ((0xFF==temp[0]) || (0xFF==temp[1]) || (0xFF==temp[2]) || (0xFF==temp[3]))
{
//printf("(%s:%d) already decode base64 Len:%d\\r\\n", __func__, __LINE__, i);
//break;//考虑到有些base64是经过变异的，不做退出处理
}
Bindata[Len++] = ((unsigned char)(((unsigned char)(temp[0] << 2))&0xFC)) |
((unsigned char)((unsigned char)(temp[1]>>4)&0x03));
if (Base64Buf[i+2] == '=')
{
printf("(%s:%d) already decode base64 Len:%d\\r\\n", __func__, __LINE__, i);
break;
}
Bindata[Len++] = ((unsigned char)(((unsigned char)(temp[1] << 4))&0xF0)) |
((unsigned char)((unsigned char)(temp[2]>>2)&0x0F));
if (Base64Buf[i+3] == '=')
{
printf("(%s:%d) already decode base64 Len:%d\\r\\n", __func__, __LINE__, i);
break;
}
Bindata[Len++] = ((unsigned char)(((unsigned char)(temp[2] << 6))&0xF0)) |
((unsigned char)(temp[3]&0x3F));
}
return Len;
}
base64测试
我们对如下三种数据进行编解码测试：免责声明: 凡注明来源本网的所有作品，均为本网合法拥有版权或有权使用的作品，欢迎转载，注明出处。非本网作品均来自互联网，转载目的在于传递更多信息，并不代表本网赞同其观点和对其真实性负责。
