public static bool GetRandomBoolean(this IRandomNumberGenerator generator)
{
var buf = new byte[1]; // PERF: pre-allocate or pool or cache the buffers.
generator.FillWithRandomBytes(buf);
return(buf[0] >= 128); // Low values of the byte are false, high values are true.
}
// Implementation for GetRandom...() based on http://codereview.stackexchange.com/questions/6304/algorithm-to-convert-random-bytes-to-integers
#region GetRandom[U]Int32()
public static uint GetRandomUInt32(this IRandomNumberGenerator generator)
{
var buf = new byte[4]; // PERF: pre-allocate or pool or cache the buffers.
generator.FillWithRandomBytes(buf);
var i = BitConverter.ToUInt32(buf, 0);
return(i);
}
private static byte[] GetRandomBytesLarge(this IRandomNumberGenerator generator, int byteCount)
{
var result = new byte[byteCount];
int offset = 0;
while (offset < byteCount)
{
var remaining = byteCount - offset;
var bytesToGetThisTime = generator.MaxRequestBytes < remaining ? generator.MaxRequestBytes : remaining;
generator.FillWithRandomBytes(result, offset, bytesToGetThisTime);
offset = offset + bytesToGetThisTime;
}
return(result);
}
/// <summary>
/// Generates the requested number of random bytes.
/// </summary>
/// <param name="generator"></param>
/// <param name="byteCount"></param>
/// <returns></returns>
public static byte[] GetRandomBytes(this IRandomNumberGenerator generator, int byteCount)
{
// PERF: pre-allocate or pool or cache the buffers.
if (byteCount > generator.MaxRequestBytes)
{
// We need to loop for a larger request.
// For greater chance of inlining, we push the more complex logic to a separate method.
return(GetRandomBytesLarge(generator, byteCount));
}
var result = new byte[byteCount];
generator.FillWithRandomBytes(result);
return(result);
}
public static decimal GetRandomDecimal(this IRandomNumberGenerator generator)
{
// Generate 96 bits of randomness for the decimal (which is its full precision).
// However, 96 bits will sometimes exceed the required range of 0.0-1.0
// Masking off the top bit (giving 95 bits precision) gives a distribution of 0.0-0.25.
// And we multiply by 4 to spread that in the range 0.0-1.0 nicely.
// Note that the .038m part is based on looking at the final distribution and fitting to right up to the top.
// PERF: no loops! Just a bitwise and and decimal multiply.
// PERF: cache / reuse the byte array.
var rawBytes = new byte[12];
generator.FillWithRandomBytes(rawBytes);
var lo = BitConverter.ToInt32(rawBytes, 0);
var mid = BitConverter.ToInt32(rawBytes, 4);
var hi = BitConverter.ToInt32(rawBytes, 8) & 0x7ffffff;
var d = new decimal(lo, mid, hi, false, 28);
d = d * 4.038m;
return(d);
}