/// <summary>
/// Initializes a new instance of the <see cref="LinearFeedbackShiftRegister32"/> class.
/// </summary>
/// <param name="seed">The seed to initialise the sequence with</param>
public LinearFeedbackShiftRegister32(UInt32 seed)
{
mostSignificantBits = new LinearFeedbackShiftRegister16((UInt16)seed);
leastSignificantBits = new LinearFeedbackShiftRegister16((UInt16)(seed >> 16));
repeatThreshold = mostSignificantBits.NextRandom();
lsb = leastSignificantBits.NextRandom();
}
/// <summary>
/// Initializes a new instance of the <see cref="LinearFeedbackShiftRegister32"/> class.
/// </summary>
/// <param name="seed">The seed to initialise the sequence with</param>
public LinearFeedbackShiftRegister32(uint seed)
{
_mostSignificantBits = new LinearFeedbackShiftRegister16((ushort)(seed & ushort.MaxValue));
_leastSignificantBits = new LinearFeedbackShiftRegister16((ushort)((seed >> 16) & ushort.MaxValue));
_repeatThreshold = _mostSignificantBits.NextRandom();
_lsb = _leastSignificantBits.NextRandom();
}
/// <summary>
/// Checks if this is implemented correctly
/// </summary>
public static void CorrectnessTest()
{
LinearFeedbackShiftRegister16 r = new LinearFeedbackShiftRegister16();
UInt16 first = r.NextRandom();
UInt16 value;
int period = 0;
do
{
value = r.NextRandom();
++period;
} while (value != first);
if (period != PERIOD)
{
throw new Exception("Period is incorrect");
}
}
/// <summary>
/// Gets the next random number in the sequence
/// </summary>
/// <returns></returns>
public UInt32 NextRandom()
{
UInt16 msb = mostSignificantBits.NextRandom();
if (msb == repeatThreshold)
{
lsb = leastSignificantBits.NextRandom();
}
int a = msb << 16 | lsb;
unsafe
{
return(*((UInt32 *)&a));
}
}
/// <summary>
/// Gets the next random number in the sequence
/// </summary>
/// <returns></returns>
public uint NextRandom()
{
ushort msb = _mostSignificantBits.NextRandom();
if (msb == _repeatThreshold)
{
_lsb = _leastSignificantBits.NextRandom();
}
int a = msb << 16 | _lsb;
unsafe
{
return(*((uint *)&a));
}
}
