diff --git a/BizHawk.Emulation.DiscSystem/DiscHasher.cs b/BizHawk.Emulation.DiscSystem/DiscHasher.cs
index 82ef7d93f8..e553effbe9 100644
--- a/BizHawk.Emulation.DiscSystem/DiscHasher.cs
+++ b/BizHawk.Emulation.DiscSystem/DiscHasher.cs
@@ -13,55 +13,6 @@ namespace BizHawk.Emulation.DiscSystem
 
 		Disc disc;
 
-		class SpecialCRC32
-		{
-			private static readonly uint[] CRC32Table;
-
-			static SpecialCRC32()
-			{
-				CRC32Table = new uint[256];
-				for (uint i = 0; i < 256; ++i)
-				{
-					uint crc = i;
-					for (int j = 8; j > 0; --j)
-					{
-						if ((crc & 1) == 1)
-							crc = ((crc >> 1) ^ 0xEDB88320);
-						else
-							crc >>= 1;
-					}
-					CRC32Table[i] = crc;
-				}
-			}
-
-			uint current = 0xFFFFFFFF;
-			public unsafe void Add(byte[] data, int offset, int size)
-			{
-				if (offset + size > data.Length)
-					throw new ArgumentOutOfRangeException();
-				if(offset<0)
-					throw new ArgumentOutOfRangeException();
-				fixed(byte* pData = data)
-					for (int i = 0; i < size; i++)
-					{
-						byte b = pData[offset + i];
-						current = CRC32Table[(current ^ b) & 0xFF] ^ (current>>8);
-					}
-			}
-
-			byte[] smallbuf = new byte[8];
-			public void Add(int data)
-			{
-				smallbuf[0] = (byte)((data) & 0xFF);
-				smallbuf[1] = (byte)((data >> 8) & 0xFF);
-				smallbuf[2] = (byte)((data >> 16) & 0xFF);
-				smallbuf[3] = (byte)((data >> 24) & 0xFF);
-				Add(smallbuf, 0, 4);
-			}
-
-			public uint Result { get { return current ^ 0xFFFFFFFF; } }
-		}
-
 		/// <summary>
 		/// calculates the hash for quick PSX Disc identification
 		/// </summary>
@@ -73,7 +24,7 @@ namespace BizHawk.Emulation.DiscSystem
 			//the TOC isn't needed!
 			//but it will help detect dumps with mangled TOCs which are all too common
 			//
-			//a special CRC32 is used to help us match redump's DB elsewhere
+			//a possibly special CRC32 is used to help us match redump's DB elsewhere
 
 			SpecialCRC32 crc = new SpecialCRC32();
 			byte[] buffer2352 = new byte[2352];
@@ -144,5 +95,151 @@ namespace BizHawk.Emulation.DiscSystem
 			}
 			return "no data track found";
 		}
+
+		/// <summary>
+		/// A stateful special CRC32 calculator
+		/// This may be absolutely standard and not special at all. I don't know, there were some differences between it and other CRC code I found in bizhawk
+		/// </summary>
+		public class SpecialCRC32
+		{
+			private static readonly uint[] CRC32Table;
+
+			static SpecialCRC32()
+			{
+				CRC32Table = new uint[256];
+				for (uint i = 0; i < 256; ++i)
+				{
+					uint crc = i;
+					for (int j = 8; j > 0; --j)
+					{
+						if ((crc & 1) == 1)
+							crc = ((crc >> 1) ^ 0xEDB88320);
+						else
+							crc >>= 1;
+					}
+					CRC32Table[i] = crc;
+				}
+			}
+
+			uint current = 0xFFFFFFFF;
+			public unsafe void Add(byte[] data, int offset, int size)
+			{
+				if (offset + size > data.Length)
+					throw new ArgumentOutOfRangeException();
+				if (offset < 0)
+					throw new ArgumentOutOfRangeException();
+				fixed (byte* pData = data)
+					for (int i = 0; i < size; i++)
+					{
+						byte b = pData[offset + i];
+						current = CRC32Table[(current ^ b) & 0xFF] ^ (current >> 8);
+					}
+			}
+
+			byte[] smallbuf = new byte[8];
+			public void Add(int data)
+			{
+				smallbuf[0] = (byte)((data) & 0xFF);
+				smallbuf[1] = (byte)((data >> 8) & 0xFF);
+				smallbuf[2] = (byte)((data >> 16) & 0xFF);
+				smallbuf[3] = (byte)((data >> 24) & 0xFF);
+				Add(smallbuf, 0, 4);
+			}
+
+			/// <summary>
+			/// The negated output (the typical result of the CRC calculation)
+			/// </summary>
+			public uint Result { get { return current ^ 0xFFFFFFFF; } }
+
+			/// <summary>
+			/// The raw non-negated output
+			/// </summary>
+			public uint Current { get { return current; } set { current = value; } }
+
+			uint gf2_matrix_times(uint[] mat, uint vec)
+			{
+				int matIdx = 0;
+				uint sum = 0;
+				while (vec != 0)
+				{
+					if ((vec & 1) != 0)
+						sum ^= mat[matIdx];
+					vec >>= 1;
+					matIdx++;
+				}
+				return sum;
+			}
+
+			void gf2_matrix_square(uint[] square, uint[] mat)
+			{
+				int n;
+				for (n = 0; n < 32; n++)
+					square[n] = gf2_matrix_times(mat, mat[n]);
+			}
+
+			/// <summary>
+			/// Incorporates a pre-calculated CRC with the given length by combining crcs
+			/// It's a bit flaky, so be careful, but it works
+			/// </summary>
+			public void Incorporate(uint crc, int len)
+			{
+				current = crc32_combine(current, crc, len);
+			}
+
+			//tables used by crc32_combine
+			uint[] even, odd;
+
+			//algorithm from zlib's crc32_combine. read http://www.leapsecond.com/tools/crcomb.c for more
+			uint crc32_combine(uint crc1, uint crc2, int len2)
+			{
+				if (even == null) even = new uint[32];    // even-power-of-two zeros operator
+				if (odd == null) odd = new uint[32];    // odd-power-of-two zeros operator
+
+				// degenerate case
+				if (len2 == 0)
+					return crc1;
+
+				// put operator for one zero bit in odd
+				odd[0] = 0xedb88320;           //CRC-32 polynomial
+				uint row = 1;
+				for (int n = 1; n < 32; n++)
+				{
+					odd[n] = row;
+					row <<= 1;
+				}
+
+				//put operator for two zero bits in even
+				gf2_matrix_square(even, odd);
+
+				//put operator for four zero bits in odd
+				gf2_matrix_square(odd, even);
+
+				//apply len2 zeros to crc1 (first square will put the operator for one zero byte, eight zero bits, in even)
+				do
+				{
+					//apply zeros operator for this bit of len2
+					gf2_matrix_square(even, odd);
+					if ((len2 & 1) != 0)
+						crc1 = gf2_matrix_times(even, crc1);
+					len2 >>= 1;
+
+					//if no more bits set, then done
+					if (len2 == 0)
+						break;
+
+					//another iteration of the loop with odd and even swapped
+					gf2_matrix_square(odd, even);
+					if ((len2 & 1) != 0)
+						crc1 = gf2_matrix_times(odd, crc1);
+					len2 >>= 1;
+
+					//if no more bits set, then done
+				} while (len2 != 0);
+
+				//return combined crc
+				crc1 ^= crc2;
+				return crc1;
+			}
+		}
 	}
 }
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