Convert Int32.Maximum+ valued number to int32

Question

I want to covert a big number, which is bigger than int32 maximum range - to int32 using C#. So that if it is over than maximum range 2147483647, then it will start again from -2147483648. For now I am doing this like :

long val = 3903086636L;
long rem = val % 2147483648L;
long div = val / 2147483648L;
int result = div % 2 == 0 ? (int)rem - 1 : -2147483648 + (int)rem;

I am not sure that if I doing this correctly. Is there any utility function or quick way to doing this in C# ?

Answer 1

If you don't have checked mode enabled, just casting it will handle the overflow as you expect:

int i = (int)val;

Or, as suggested by Matthew Watson, to make it compiler-setting independent:

int i = unchecked((int)val);

This will not throw an exception. The integer will overflow and continue counting from int.MinValue.

Proof:

long val = (long)int.MaxValue + 1;
int result = (int)val;

Console.WriteLine(result == int.MinValue); // true