CRCs needed by ripper

CUETools.Ripper.SCSI/CRC16CCITT.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace CUETools.Ripper.SCSI
+{
+	public enum InitialCrcValue { Zeros, NonZero1 = 0xffff, NonZero2 = 0x1D0F }
+
+	class Crc16Ccitt
+	{
+		const ushort poly = 4129;
+		ushort[] table = new ushort[256];
+		ushort initialValue = 0;
+
+		public ushort ComputeChecksum(byte[] bytes, int pos, int count)
+		{
+			ushort crc = this.initialValue;
+			for (int i = pos; i < pos + count; i++)
+			{
+				crc = (ushort)((crc << 8) ^ table[((crc >> 8) ^ (0xff & bytes[i]))]);
+			}
+			return crc;
+		}
+
+		public byte[] ComputeChecksumBytes(byte[] bytes, int pos, int count)
+		{
+			ushort crc = ComputeChecksum(bytes, pos, count);
+			return new byte[] { (byte)(crc >> 8), (byte)(crc & 0x00ff) };
+		}
+
+		public Crc16Ccitt(InitialCrcValue initialValue)
+		{
+			this.initialValue = (ushort)initialValue;
+			ushort temp, a;
+			for (int i = 0; i < table.Length; i++)
+			{
+				temp = 0;
+				a = (ushort)(i << 8);
+				for (int j = 0; j < 8; j++)
+				{
+					if (((temp ^ a) & 0x8000) != 0)
+					{
+						temp = (ushort)((temp << 1) ^ poly);
+					}
+					else
+					{
+						temp <<= 1;
+					}
+					a <<= 1;
+				}
+				table[i] = temp;
+			}
+		}
+	}
+}