Ubah String Binary ke hexa

Hari ini mau tulis snipet code kecil yakni untuk mengubah string biner ke hexa.
Contohnya "1000" => 0x08
Langsung liat ke kode di bawah ini :

unsigned char gethexa(unsigned char *strhex) {
    int i;
    unsigned char arrbin[16][5]= {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"};
    unsigned char byte[16] = {0x0, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F};

    for(i = 0; i < 16; i++)
       if(strcmp(strhex, arrbin[i]) == 0) return byte[i];

    return 0x0;
}
/************************************************
* Change string biner to hexa.
* e.x : "1000" => 0x08
* Params :
* - binstr   = string biner
* - binhex = hexa biner
*
*/
int strbin2hex(unsigned char *binstr, unsigned char *binhex) {
        int i, j = 0, len;

        unsigned char bintmp[5];
        unsigned char hextmp;

        memset(bintmp, 0x0, sizeof(bintmp));

        for(i = 0; i < strlen(binstr); i+=8) {
                memcpy(bintmp, &binstr[i], 4);
                hextmp = gethexa(bintmp);
                hextmp <<= 4;

                memcpy(bintmp, &binstr[i+4], 4);
                hextmp |= gethexa(bintmp);
                binhex[j] = hextmp;
                printf("binhex[%d] %x\n", j, binhex[j]);
                len = ++j;
        }
        return len ;
}

Ubah Long Long Int ke String dan sebaliknya

Sore ini mau tulis kode cara convert string ke long long int dan sebaliknya. Kenapa menggunakan long long int itu karena pada kasus saya, saya membutuhkan 8 byte.
Langsung aja ke kode

/*******************************************************************
* Convert unsigned long long int to string.
* Params :
* - in : varible unsigned long long int that wil be converted [INPUT]
* - oBuff : buffer array [OUTPUT]
* - len_byte : length of buffer array [INPUT]
* return 
* - len as length of buffer array
*       
*/              
int ullint2str(unsigned long long int in, unsigned char *oBuff, int len_byte) {
        int len, i;
        unsigned long long int tmp = 0x0L;
        
        len = len_byte;
        tmp = in;

        for (i = len - 1; i >= 0; i--) {
                oBuff[i] = tmp;
                if (i != 0) tmp >>= 8;
        }

        return len;
}