/// <summary>
/// Create a permutation using an encoded permutation
/// </summary>
///
/// <param name="Encoded">The encoded permutation</param>
public Permutation(byte[] Encoded)
{
if (Encoded.Length <= 4)
{
throw new ArgumentException("Permutation: Invalid encoding!");
}
int n = LittleEndian.OctetsToInt(Encoded, 0);
int size = BigMath.CeilLog256(n - 1);
if (Encoded.Length != 4 + n * size)
{
throw new ArgumentException("Permutation: Invalid encoding!");
}
_perm = new int[n];
for (int i = 0; i < n; i++)
{
_perm[i] = LittleEndian.OctetsToInt(Encoded, 4 + i * size, size);
}
if (!IsPermutation(_perm))
{
throw new ArgumentException("Permutation: Invalid encoding!");
}
}
/// <summary>
/// Encode this permutation as byte array
/// </summary>
///
/// <returns>The encoded permutation</returns>
public byte[] GetEncoded()
{
int n = _perm.Length;
int size = BigMath.CeilLog256(n - 1);
byte[] result = new byte[4 + n * size];
LittleEndian.IntToOctets(n, result, 0);
for (int i = 0; i < n; i++)
{
LittleEndian.IntToOctets(_perm[i], result, 4 + i * size, size);
}
return(result);
}