c语言base64编码

#include
#include

const char * base64char  = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
char * base64_encode( const unsigned char * originChar, char * base64, int originlength )//base64编码
{
    int i, j;
    unsigned char current;
 
    for ( i = 0, j = 0 ; i < originlength ; i += 3 )
    {
        current = (originChar[i] >> 2) ;
        current &= (unsigned char)0x3F;
        base64[j++] = base64char[(int)current];
 
        current = ( (unsigned char)(originChar[i] << 4 ) ) & ( (unsigned char)0x30 ) ;
        if ( i + 1 >= originlength )
        {
            base64[j++] = base64char[(int)current];
            base64[j++] = '=';
            base64[j++] = '=';
            break;
        }
        current |= ( (unsigned char)(originChar[i+1] >> 4) ) & ( (unsigned char) 0x0F );
        base64[j++] = base64char[(int)current];
 
        current = ( (unsigned char)(originChar[i+1] << 2) ) & ( (unsigned char)0x3C ) ;
        if ( i + 2 >= originlength )
        {
            base64[j++] = base64char[(int)current];
            base64[j++] = '=';
            break;
        }
        current |= ( (unsigned char)(originChar[i+2] >> 6) ) & ( (unsigned char) 0x03 );
        base64[j++] = base64char[(int)current];
 
        current = ( (unsigned char)originChar[i+2] ) & ( (unsigned char)0x3F ) ;
        base64[j++] = base64char[(int)current];
    }
    base64[j] = '';
    return base64;
}

int base64_decode( const char * base64, unsigned char * originChar )//base64解码
{
    int i, j;
    unsigned char k;
    unsigned char temp[4];
    for ( i = 0, j = 0; base64[i] != '' ; i += 4 )
    {
        memset( temp, 0xFF, sizeof(temp) );
        for ( k = 0 ; k < 64 ; k ++ )
        {
            if ( base64char[k] == base64[i] )
                temp[0]= k;
        }
        for ( k = 0 ; k < 64 ; k ++ )
        {
            if ( base64char[k] == base64[i+1] )
                temp[1]= k;
        }
        for ( k = 0 ; k < 64 ; k ++ )
        {
            if ( base64char[k] == base64[i+2] )
                temp[2]= k;
        }
        for ( k = 0 ; k < 64 ; k ++ )
        {
            if ( base64char[k] == base64[i+3] )
                temp[3]= k;
        }
 
        originChar[j++] = ((unsigned char)(((unsigned char)(temp[0] << 2))&0xFC)) |
                ((unsigned char)((unsigned char)(temp[1]>>4)&0x03));
        if ( base64[i+2] == '=' )
            break;
 
        originChar[j++] = ((unsigned char)(((unsigned char)(temp[1] << 4))&0xF0)) |
                ((unsigned char)((unsigned char)(temp[2]>>2)&0x0F));
        if ( base64[i+3] == '=' )
            break;
 
        originChar[j++] = ((unsigned char)(((unsigned char)(temp[2] << 6))&0xF0)) |
                ((unsigned char)(temp[3]&0x3F));
    }
    return j;
}

int main(){
    char *buff = "12345678";
    int len = sizeof(buff);
    char base64[len*4/3+2];

    char baes64[len*4/3+2];
    base64_encode(buff,base64,len);
    printf("base64 = %sn",base64);
    base64_decode(base64,baes64);
    printf("baes64 = %sn",baes64);
    return 0;
}

原文链接：https://blog.csdn.net/lly_3485390095/article/details/107043753