A Fast Random Number Generator Based on BigInteger
using System;
using System.Numerics;
using System.Security.Cryptography;
public struct RandomX
{
private readonly RNGCryptoServiceProvider _crng;
private int _maxByteWidth;
private int _bitWidth;
public RandomX(int bitWidth)
{
MaxValue = BigIntegerHelper.GetMaxValueBitWidth(bitWidth);
_maxByteWidth = bitWidth >> 3;
OddsOnly = false;
Unsigned = false;
_crng = new RNGCryptoServiceProvider();
_bitWidth = bitWidth;
}
public bool OddsOnly;
public bool Unsigned;
public int BitWidth
{
get => _bitWidth;
set
{
_bitWidth = value;
MaxValue = BigIntegerHelper.GetMaxValueBitWidth(_bitWidth);
_maxByteWidth = _bitWidth >> 3;
}
}
public BigInteger MaxValue;
public bool NextBool()
{
return Sample() < .5;
}
public char NextChar(char maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 16)
BitWidth = 16;
return (char) (Sample() * maxValue);
}
public char NextChar(char minValue, char maxValue)
{
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 16)
BitWidth = 16;
return (char) Next(minValue, maxValue);
}
public sbyte NextInt8()
{
if (Unsigned)
Unsigned = false;
if (_bitWidth < 8)
BitWidth = 8;
return (sbyte) Internal();
}
public sbyte NextInt8(sbyte maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
if (Unsigned)
Unsigned = false;
if (_bitWidth < 8)
BitWidth = 8;
return (sbyte) (Sample() * maxValue);
}
public sbyte NextInt8(sbyte minValue, sbyte maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (Unsigned)
Unsigned = false;
if (_bitWidth < 8)
BitWidth = 8;
return (sbyte) Next(minValue, maxValue);
}
public byte NextUInt8()
{
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 8)
BitWidth = 8;
var n = Internal();
return (byte) n;
}
public byte NextUInt8(byte maxValue)
{
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 8)
BitWidth = 8;
return (byte) (Sample() * maxValue);
}
public byte NextUInt8(byte minValue, byte maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 8)
BitWidth = 8;
return (byte) Next(minValue, maxValue);
}
public short NextInt16()
{
if (_bitWidth < 16)
BitWidth = 16;
if (Unsigned)
Unsigned = false;
return (short) Internal();
}
public short NextInt16(short maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
if (Unsigned)
Unsigned = false;
if (_bitWidth < 16)
BitWidth = 16;
return (short) (Sample() * maxValue);
}
public short NextInt16(short minValue, short maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (Unsigned)
Unsigned = false;
if (_bitWidth < 16)
BitWidth = 16;
return (short) Next(minValue, maxValue);
}
public ushort NextUInt16()
{
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 16)
BitWidth = 16;
return (ushort) Internal();
}
public ushort NextUInt16(ushort maxValue)
{
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 16)
BitWidth = 16;
return (ushort) (Sample() * maxValue);
}
public ushort NextUInt16(ushort minValue, ushort maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 16)
BitWidth = 16;
return (ushort) Next(minValue, maxValue);
}
public int NextInt24()
{
BitWidth = 24;
if (Unsigned)
Unsigned = false;
return (int) Internal();
}
public int NextInt24(int maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
if (Unsigned)
Unsigned = false;
BitWidth = 24;
return (int) (Sample() * maxValue);
}
public int NextInt24(int minValue, int maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (Unsigned)
Unsigned = false;
BitWidth = 24;
return (int) Next(minValue, maxValue);
}
public uint NextUInt24()
{
if (!Unsigned)
Unsigned = true;
BitWidth = 24;
return (uint) Internal();
}
public uint NextUInt24(uint maxValue)
{
if (!Unsigned)
Unsigned = true;
BitWidth = 24;
return (uint) (Sample() * maxValue);
}
public uint NextUInt24(uint minValue, uint maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (!Unsigned)
Unsigned = true;
BitWidth = 24;
return (uint) Next(minValue, maxValue);
}
public uint NextUInt32()
{
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 32)
BitWidth = 32;
return (uint) Internal();
}
public uint NextUInt32(uint maxValue)
{
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 32)
BitWidth = 32;
return (uint) (Sample() * maxValue);
}
public uint NextUInt32(uint minValue, uint maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 32)
BitWidth = 32;
return (uint) Next(minValue, maxValue);
}
public int NextInt32()
{
if (Unsigned)
Unsigned = false;
if (_bitWidth < 32)
BitWidth = 32;
return (int) Internal();
}
public int NextInt32(int maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
if (Unsigned)
Unsigned = false;
if (_bitWidth < 32)
BitWidth = 32;
return (int) (Sample() * maxValue);
}
public int NextInt32(int minValue, int maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (Unsigned)
Unsigned = false;
if (_bitWidth < 32)
BitWidth = 32;
return (int) Next(minValue, maxValue);
}
public long NextUInt40()
{
if (!Unsigned)
Unsigned = true;
BitWidth = 40;
return (long) Internal();
}
public long NextUInt40(long maxValue)
{
if (!Unsigned)
Unsigned = true;
BitWidth = 40;
return (long) (Sample() * maxValue);
}
public long NextUInt40(long minValue, long maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (!Unsigned)
Unsigned = true;
BitWidth = 40;
return (long) Next(minValue, maxValue);
}
public long NextInt40()
{
if (Unsigned)
Unsigned = false;
BitWidth = 40;
return (long) Internal();
}
public long NextInt40(long maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
if (Unsigned)
Unsigned = false;
BitWidth = 40;
return (long) (Sample() * maxValue);
}
public long NextInt40(long minValue, long maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (Unsigned)
Unsigned = false;
BitWidth = 40;
return (long) Next(minValue, maxValue);
}
public ulong NextUInt48()
{
if (!Unsigned)
Unsigned = true;
BitWidth = 48;
return (ulong) Internal();
}
public ulong NextUInt48(ulong maxValue)
{
if (!Unsigned)
Unsigned = true;
BitWidth = 48;
return (ulong) (Sample() * maxValue);
}
public ulong NextUInt48(ulong minValue, ulong maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (!Unsigned)
Unsigned = true;
BitWidth = 48;
return (ulong) Next(minValue, maxValue);
}
public long NextInt48()
{
if (Unsigned)
Unsigned = false;
BitWidth = 48;
return (long) Internal();
}
public long NextInt48(long maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
if (Unsigned)
Unsigned = false;
BitWidth = 48;
return (long) (Sample() * maxValue);
}
public ulong NextUInt56()
{
if (!Unsigned)
Unsigned = true;
BitWidth = 56;
return (ulong) Internal();
}
public ulong NextUInt56(ulong maxValue)
{
if (!Unsigned)
Unsigned = true;
BitWidth = 56;
return (ulong) (Sample() * maxValue);
}
public ulong NextUInt56(ulong minValue, ulong maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (!Unsigned)
Unsigned = true;
BitWidth = 56;
return (uint) Next(minValue, maxValue);
}
public long NextInt56()
{
if (Unsigned)
Unsigned = false;
BitWidth = 56;
return (long) Internal();
}
public long NextInt56(long maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
if (Unsigned)
Unsigned = false;
BitWidth = 56;
return (long) (Sample() * maxValue);
}
public long NextInt56(long minValue, long maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (Unsigned)
Unsigned = false;
BitWidth = 48;
return (long) Next(minValue, maxValue);
}
public long NextInt64()
{
if (Unsigned)
Unsigned = false;
if (_bitWidth < 64)
BitWidth = 64;
return (long) Internal();
}
public long NextInt64(long maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
if (Unsigned)
Unsigned = false;
if (_bitWidth < 64)
BitWidth = 64;
return (long) (Sample() * maxValue);
}
public long NextInt64(long minValue, long maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (Unsigned)
Unsigned = false;
if (_bitWidth < 64)
BitWidth = 64;
return (long) Next(minValue, maxValue);
}
public ulong NextUInt64()
{
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 64)
BitWidth = 64;
return (ulong) Internal();
}
public ulong NextUInt64(ulong maxValue)
{
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 64)
BitWidth = 64;
return (ulong) (Sample() * maxValue);
}
public ulong NextUInt64(ulong minValue, ulong maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
if (!Unsigned)
Unsigned = true;
if (_bitWidth < 64)
BitWidth = 64;
return (ulong) Next(minValue, maxValue);
}
public BigInteger Next()
{
return Internal();
}
public BigInteger Next(BigInteger minValue, BigInteger maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
return (BigInteger) (Sample() * (maxValue - minValue)) + minValue;
}
public UInt512 Next(UInt512 minValue, UInt512 maxValue)
{
if (minValue > maxValue)
throw new ArgumentException("maxValue must be greater than or equal to minValue");
var s = Sample();
var f = (BigDecimal) ((BigInteger) maxValue - (BigInteger) minValue);
return (BigInteger) (s * f);
}
public BigInteger Next(BigInteger maxValue)
{
if (maxValue < 0)
throw new ArgumentException("maxValue must be greater than zero.");
return (BigInteger) (Sample() * maxValue);
}
public unsafe double NextDouble()
{
var buf = new byte[8];
GetBytes(buf);
fixed (byte* ptr = buf)
{
return *(ulong*) ptr * (1.0 / ulong.MaxValue) * ulong.MaxValue;
}
}
public BigRational NextBigRational()
{
return new BigRational(Internal(), Internal());
}
public decimal NextDecimal()
{
return new decimal(NextInt32(), NextInt32(), NextInt32(), NextBool(), NextUInt8(255));
}
public BigDecimal NextBigDecimal()
{
return Sample();
}
public byte[] GetNextByteArray(int size)
{
var ba = new byte[size];
_crng.GetBytes(ba);
return ba;
}
public char[] GetNextCharArray(int size)
{
var xbc = new byte[1];
var ca = new char[size];
var ptr = 0;
do
{
_crng.GetBytes(xbc);
var c = xbc[0];
if (c >= 0x20 && c <= 0x7F)
ca[ptr++] = (char) c;
} while (ptr < size);
return ca;
}
public char NextChar()
{
var xbc = new byte[1];
while (true)
{
_crng.GetBytes(xbc);
var c = xbc[0];
if (c >= 0x20 && c <= 0x7F)
return (char) c;
}
}
public string GetRandomString(int minLen, int maxLen)
{
return minLen == maxLen ? new string(GetNextCharArray(minLen)) : new string(GetNextCharArray((int) NextUInt32((uint) minLen, (uint) maxLen)));
}
private BigDecimal Sample()
{
var i = Internal();
var s = i * (BigDecimal.One / MaxValue);
if (s.Sign == -1)
s = s * -1;
if (s.IsZero)
throw new Exception("Sample is zero.");
return s;
}
public void GetBytes(byte[] data)
{
if (data == null)
throw new ArgumentException("The buffer cannot be null.");
_crng.GetBytes(data);
}
private BigInteger Internal()
{
if (Unsigned)
{
var buffer = new byte[_maxByteWidth + 1];
_crng.GetBytes(buffer);
buffer[_maxByteWidth] = 0;
var n = new BigInteger(buffer);
return !OddsOnly ? n : n | 1;
}
else
{
var buffer = new byte[_maxByteWidth];
_crng.GetBytes(buffer);
var n = new BigInteger(buffer);
return !OddsOnly ? n : n | 1;
}
}
}