/// <summary>
/// Creates a new <see cref="SpongeState"/> specifying its size and rate.
/// </summary>
/// <param name="size">The size of the sponge state.</param>
/// <param name="rate">The rate of the sponge state, i.e. the number of bits which are impacted while absorbing
/// messages.</param>
/// <exception cref="ArgumentException"><paramref name="rate"/> is lower than one, or <paramref name="rate"/> is
/// greater than or equal to <paramref name="size"/>'s <see cref="SpongeSize.B"/>.</exception>
/// <remarks>
/// <para>The capacity of the state, i.e. the number of bits which are not impacted while absorbing messages, will
/// be <paramref name="size"/>.B - <paramref name="rate"/>.</para>
/// </remarks>
public SpongeState(SpongeSize size, int rate)
{
int b = size.B;
if ((rate < 1) || (rate >= b))
{
throw new ArgumentException($"Invalid rate {rate} for width {b}.", nameof(rate));
}
_size = size;
_rate = rate;
_bitstring = Bitstring.Zeroes(b);
}
private static SpongeState Iota(SpongeState state, int round)
{
int w = state.Size.W;
int l = state.Size.L;
Bitstring rc = Bitstring.Zeroes(w);
RoundT roundT;
int t;
int rnd = 7 * round;
for (int j = 0; j <= l; j++)
{
t = j + rnd;
roundT = new RoundT(round, t);
if (!_roundTConstants.ContainsKey(roundT))
{
_roundTConstants.Add(roundT, RoundConstant(t));
}
rc[(1 << j) - 1] = _roundTConstants[roundT];
}
state.XorLane(state.GetLane(0, 0), rc);
return(state);
}
