I'm trying to generate a number based on a seed in C#. The only problem is that the seed is too big to be an int32. Is there a way I can use a long as the seed?
And yes, the seed MUST be a long.
Here's a C# version of Java.Util.Random
that I ported from the Java Specification.
The best thing to do is to write a Java program to generate a load of numbers and check that this C# version generates the same numbers.
public sealed class JavaRng
{
public JavaRng(long seed)
{
_seed = (seed ^ LARGE_PRIME) & ((1L << 48) - 1);
}
public int NextInt(int n)
{
if (n <= 0)
throw new ArgumentOutOfRangeException("n", n, "n must be positive");
if ((n & -n) == n) // i.e., n is a power of 2
return (int)((n * (long)next(31)) >> 31);
int bits, val;
do
{
bits = next(31);
val = bits % n;
} while (bits - val + (n-1) < 0);
return val;
}
private int next(int bits)
{
_seed = (_seed*LARGE_PRIME + SMALL_PRIME) & ((1L << 48) - 1);
return (int) (((uint)_seed) >> (48 - bits));
}
private long _seed;
private const long LARGE_PRIME = 0x5DEECE66DL;
private const long SMALL_PRIME = 0xBL;
}