什么是Base64？
出處：網(wǎng)絡(luò)整理 發(fā)布于：2024-07-22 17:34:16
Base64是一種用于將二進(jìn)制數(shù)據(jù)編碼為文本的編碼方式。它將任意的二進(jìn)制數(shù)據(jù)通過編碼轉(zhuǎn)換成由64個(gè)字符組成的ASCII字符串，這些字符包括大寫字母、小寫字母、數(shù)字和兩個(gè)額外的符號。Base64編碼后的字符串通常用于在文本協(xié)議中傳輸數(shù)據(jù)，例如電子郵件的傳輸編碼、在URL中傳遞數(shù)據(jù)、在數(shù)據(jù)的存儲(chǔ)和傳輸中避免亂碼等場景。
Base64編碼的特點(diǎn)包括：
可讀性： 編碼后的字符串可以由人類讀取和處理，由于使用了ASCII字符集，能夠避免一些特定編碼的問題。
長度增加： 編碼后的長度大約是原始數(shù)據(jù)的4/3倍，這是因?yàn)槊?個(gè)字節(jié)的數(shù)據(jù)編碼成4個(gè)Base64字符。
無損轉(zhuǎn)換： Base64編碼和解碼是無損的，可以完全還原原始的二進(jìn)制數(shù)據(jù)。
Base64編碼使用的字符集包括：
大寫字母 A-Z (26個(gè)字符)
小寫字母 a-z (26個(gè)字符)
數(shù)字 0-9 (10個(gè)字符)
符號 + 和 /
總共64個(gè)字符，因此得名Base64
base64測試
我們對如下三種數(shù)據(jù)進(jìn)行編解碼測試：
"hello world abcdefg"
"hello ,,,,,,,,, world"
{0x81, 0x82, 0x83, 0x84}
#include
#include
#include
/* Base64編碼映射表 */
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編碼
*輸入?yún)?shù): Bindata：原始bin數(shù)據(jù)
Binlen：原始 bin數(shù)據(jù)長度
*輸出參數(shù)：Base64Buf：base64編碼數(shù)據(jù)
*返 回 值：base64編碼后數(shù)據(jù)長度
*********************************************************/
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解碼
*輸入?yún)?shù): Base64Buf：base64編碼數(shù)據(jù)
*輸出參數(shù)：Bindata：解碼后bin數(shù)據(jù)
*返 回 值：解碼后bin數(shù)據(jù)長度
*********************************************************/
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;//考慮到有些base64是經(jīng)過變異的，不做退出處理
}
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測試
我們對如下三種數(shù)據(jù)進(jìn)行編解碼測試："hello world abcdefg"
"hello ,,,,,,,,, world"
{0x81, 0x82, 0x83, 0x84}
#include
#include
#include
/* Base64編碼映射表 */
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編碼
*輸入?yún)?shù): Bindata：原始bin數(shù)據(jù)
Binlen：原始 bin數(shù)據(jù)長度
*輸出參數(shù)：Base64Buf：base64編碼數(shù)據(jù)
*返 回 值：base64編碼后數(shù)據(jù)長度
*********************************************************/
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解碼
*輸入?yún)?shù): Base64Buf：base64編碼數(shù)據(jù)
*輸出參數(shù)：Bindata：解碼后bin數(shù)據(jù)
*返 回 值：解碼后bin數(shù)據(jù)長度
*********************************************************/
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;//考慮到有些base64是經(jīng)過變異的，不做退出處理
}
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;
}
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