public byte[] Build()
{
var payload = this.BuildPayload();
byte[] checksum;
using (var crc = new Crc32(Crc32.DefaultPolynomialReversed, Crc32.DefaultSeed))
{
checksum = crc.ComputeHash(payload);
Array.Reverse(checksum);
}
var payloadLen = Buffer.ByteLength(payload);
var result = new byte[6 + payloadLen];
Buffer.SetByte(result, 0, 0x42); // "B"
Buffer.SetByte(result, 1, 0x45); // "E"
Buffer.BlockCopy(checksum, 0, result, 2, 4);
Buffer.BlockCopy(payload, 0, result, 6, payloadLen);
return result;
}
/// <summary>
/// Verifies that the CRC32 checksum of the datagram being processed is valid.
/// </summary>
/// <returns> True if the CRC32 checsum is valid; false otherwise. </returns>
public bool VerifyCrc()
{
int payloadLength = Buffer.ByteLength(this.buffer) - 6;
var payload = new byte[payloadLength];
Buffer.BlockCopy(this.buffer, 6, payload, 0, payloadLength);
byte[] computedChecksum;
using (var crc = new Crc32(Crc32.DefaultPolynomialReversed, Crc32.DefaultSeed))
{
computedChecksum = crc.ComputeHash(payload);
Array.Reverse(computedChecksum);
}
var originalChecksum = new byte[4];
Buffer.BlockCopy(this.buffer, 2, originalChecksum, 0, 4);
return computedChecksum.SequenceEqual(originalChecksum);
}