all CRCs in one place

CUETools.Codecs/CRCs/CRC32.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace CUETools.Codecs
+{
+	public class Crc32
+	{
+		uint[] table = new uint[256];
+
+		public uint ComputeChecksum(uint crc, byte val)
+		{
+			return (crc >> 8) ^ table[(crc & 0xff) ^ val];
+		}
+
+		public uint ComputeChecksum(uint crc, byte[] bytes, int pos, int count)
+		{
+			for (int i = pos; i < pos + count; i++)
+				crc = ComputeChecksum(crc, bytes[i]);
+			return crc;
+		}
+
+		public uint ComputeChecksum(uint crc, uint s)
+		{
+			return ComputeChecksum(ComputeChecksum(ComputeChecksum(ComputeChecksum(
+				crc, (byte)s), (byte)(s >> 8)), (byte)(s >> 16)), (byte)(s >> 24));
+		}
+
+		public unsafe uint ComputeChecksum(uint crc, int * samples, uint count)
+		{
+			for (uint i = 0; i < count; i++)
+			{
+				int s1 = samples[2 * i], s2 = samples[2 * i + 1];
+				crc = ComputeChecksum(ComputeChecksum(ComputeChecksum(ComputeChecksum(
+					crc, (byte)s1), (byte)(s1 >> 8)), (byte)s2), (byte)(s2 >> 8));
+			}
+			return crc;
+		}
+
+		public unsafe uint ComputeChecksumWONULL(uint crc, int* samples, uint count)
+		{
+			for (uint i = 0; i < count; i++)
+			{
+				int s1 = samples[2 * i], s2 = samples[2 * i + 1];
+				if (s1 != 0)
+					crc = ComputeChecksum(ComputeChecksum(crc, (byte)s1), (byte)(s1 >> 8));
+				if (s2 != 0)
+					crc = ComputeChecksum(ComputeChecksum(crc, (byte)s2), (byte)(s2 >> 8));
+			}
+			return crc;
+		}
+
+		uint Reflect(uint val, int ch)
+		{
+			uint value = 0;
+			// Swap bit 0 for bit 7
+			// bit 1 for bit 6, etc.
+			for (int i = 1; i < (ch + 1); i++)
+			{
+				if (0 != (val & 1))
+					value |= 1U << (ch - i);
+				val >>= 1;
+			}
+			return value;
+		}
+
+		const uint ulPolynomial = 0x04c11db7;
+
+		public Crc32()
+		{
+			for (uint i = 0; i < table.Length; i++)
+			{
+				table[i] = Reflect(i, 8) << 24;
+				for (int j = 0; j < 8; j++)
+					table[i] = (table[i] << 1) ^ ((table[i] & (1U << 31)) == 0 ? 0 : ulPolynomial);
+				table[i] = Reflect(table[i], 32);
+			}
+		}
+	}
+}