Question

String ntohl(int i)
{
    int i1 = i % (256);
    int i2 = (i %(65536))/(256);
    int i3 = (i %(16777216))/(65536);
    int i4 = (i)/(16777216);

    int i5 = i % (2^8);
    int i6 = (i %(2^16))/(2^8);
    int i7 = (i %(2^24))/(2^16);
    int i8 = i/(2^24);

    Log.d(TAG, "i:"+i+"   "+i1+"."+i2+"."+i3+"."+i4);
    Log.d(TAG, "i:"+i+"   "+i5+"."+i6+"."+i7+"."+i8);
    return ""+i1+"."+i2+"."+i3+"."+i4;
}

Hi,

I have a method listed above which returns an ipv4 address. I’ve done the calculation however i5 i6 i7 i8 is not like i1 i2 i3 i4.

Answer 1

Using modulus can return negative numbers which you might not expect. Try using the following pattern

    int i0 = i & 0xFF;
    int i1 = (i >> 8) & 0xFF;
    int i2 = (i >> 16) & 0xFF;
    int i3 = (i >> 24) & 0xFF;