namespace NetcodeIO.NET.Internal

{

/// <summary>

/// Helper class for protecting against packet replay

/// </summary>

internal sealed class NetcodeReplayProtection

{

private const int NETCODE_REPLAY_PROTECTION_BUFFER_SIZE = 256;

public ulong mostRecentSequence;

public ulong[] receivedPackets;

public NetcodeReplayProtection()

{

mostRecentSequence = 0;

receivedPackets = new ulong[NETCODE_REPLAY_PROTECTION_BUFFER_SIZE];

Reset();

}

/// <summary>

/// Reset the packet replay buffer

/// </summary>

public void Reset()

{

mostRecentSequence = 0;

for (int i = 0; i < receivedPackets.Length; i++)

receivedPackets[i] = ulong.MaxValue;

}

/// <summary>

/// Check if the given packet was already received. If not, store it in the replay buffer.

/// </summary>

public bool AlreadyReceived(ulong sequence)

{

if ((sequence & ((ulong)1 << 63)) != 0)

return false;

if (sequence + NETCODE_REPLAY_PROTECTION_BUFFER_SIZE <= mostRecentSequence)

return true;

int index = (int)(sequence % NETCODE_REPLAY_PROTECTION_BUFFER_SIZE);

if (receivedPackets[index] == 0xFFFFFFFFFFFFFFFF)

{

receivedPackets[index] = sequence;

return false;

}

if (receivedPackets[index] >= sequence)

return true;

receivedPackets[index] = sequence;

return false;

}

}

}