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using System;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;
namespace Org.BouncyCastle.Utilities
{
/**
* BigInteger utilities.
*/
public sealed class BigIntegers
{
private const int MaxIterations = 1000;
private BigIntegers()
{
}
/**
* Return the passed in value as an unsigned byte array.
*
* @param value value to be converted.
* @return a byte array without a leading zero byte if present in the signed encoding.
*/
public static byte[] AsUnsignedByteArray(
BigInteger n)
{
return n.ToByteArrayUnsigned();
}
/**
* Return a random BigInteger not less than 'min' and not greater than 'max'
*
* @param min the least value that may be generated
* @param max the greatest value that may be generated
* @param random the source of randomness
* @return a random BigInteger value in the range [min,max]
*/
public static BigInteger CreateRandomInRange(
BigInteger min,
BigInteger max,
// TODO Should have been just Random class
SecureRandom random)
{
int cmp = min.CompareTo(max);
if (cmp >= 0)
{
if (cmp > 0)
throw new ArgumentException("'min' may not be greater than 'max'");
return min;
}
if (min.BitLength > max.BitLength / 2)
{
return CreateRandomInRange(BigInteger.Zero, max.Subtract(min), random).Add(min);
}
for (int i = 0; i < MaxIterations; ++i)
{
BigInteger x = new BigInteger(max.BitLength, random);
if (x.CompareTo(min) >= 0 && x.CompareTo(max) <= 0)
{
return x;
}
}
// fall back to a faster (restricted) method
return new BigInteger(max.Subtract(min).BitLength - 1, random).Add(min);
}
}
}
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