ThexCS - TTH (Tiger Tree Hash) Maker in C#

/*
 * 
 * Tiger Tree Hash Optimized - by Gil Schmidt.
 * 
 *  - this code was writtin based on:
 *    "Tree Hash EXchange format (THEX)" 
 *    http://www.open-content.net/specs/draft-jchapweske-thex-02.html
 * 
 *  - the tiger hash class was converted from visual basic code called TigerNet:
 *    http://www.hotpixel.net/software.html
 * 
 *  - Base32 class was taken from:
 *    http://msdn.microsoft.com/msdnmag/issues/04/07/CustomPreferences/default.aspx
 *    didn't want to waste my time on writing a Base32 class.
 * 
 *  - after making the first working TTH class i noticed that it was very slow,i decided 
 *    to improve the code by fixed size ('Block_Size') blocks and compress them into 1 hash 
 *    string. (save memory and makes the cpu works a little less in a smaller arrays).
 * 
 *  - increase 'Block_Size' for better performance but it will cost you by memory.
 * 
 *  - fixed code for 0 byte file (thanks Flow84).
 * 
 *  if you use this code please add my name and email to the references!
 *  [ contact me at Gil_Smdt@hotmali.com ]
 * 
 */

using System;
using System.Text;
using System.IO;
using System.Collections;

namespace ThexCS
{
	public class ThexOptimized
	{
        const   int        ZERO_BYTE_FILE  = 0;    //file with no data.
        const   int        Block_Size      = 64;   //64k 
		const   int        Leaf_Size       = 1024; //1k - don't change this.

		private int        Leaf_Count; //number of leafs.
		private byte[][]   HashValues; //array for hash values.
		private FileStream FilePtr;    //dest file stream pointer.

		public byte[] GetTTH(string Filename) 
		{
            byte[] TTH = null;

            try
			{
				if (!File.Exists(Filename)) 
				{
					System.Diagnostics.Debug.WriteLine("file doesn't exists " + Filename);
					return null;
				}

				//open the file.
				FilePtr = new FileStream(Filename,FileMode.Open,FileAccess.Read,FileShare.ReadWrite);
                
                //if the file is 0 byte long.
                if (FilePtr.Length == ZERO_BYTE_FILE)
                {
                    Tiger TG = new Tiger();

                    TTH = TG.ComputeHash(new byte[] { 0 });
                }

                //the file is smaller then a single leaf.
                else if (FilePtr.Length <= Leaf_Size * Block_Size)
                    TTH = CompressSmallBlock();

                //normal file.
                else
                {
                    Leaf_Count = (int)FilePtr.Length / Leaf_Size;
                    if (FilePtr.Length % Leaf_Size > 0) Leaf_Count++;

                    GetLeafHash(); //get leafs hash from file.
                    System.Diagnostics.Debug.WriteLine("===> [ Moving to internal hash. ]");
                    TTH = CompressHashBlock(HashValues, Leaf_Count);	//get root TTH from hash array.
                }
			}
			catch (Exception e)
			{
				System.Diagnostics.Debug.WriteLine("error while trying to get TTH for file: " + 
					Filename + ". (" + e.Message + ")");

                TTH = null;
			}

            if (FilePtr != null) FilePtr.Close();

            return TTH;
		}

		private void GetLeafHash() //gets the leafs from the file and hashes them.
		{
			int i;
			int Blocks_Count = (int) Leaf_Count / (Block_Size * 2);
			
			if (Leaf_Count % (Block_Size * 2) > 0) Blocks_Count++;
			HashValues = new byte[Blocks_Count][];

			byte[][] HashBlock = new byte[(int)Block_Size][];
			
			for (i = 0; i < (int) Leaf_Count / (Block_Size * 2); i++) //loops threw the blocks.
			{
				for (int LeafIndex = 0; LeafIndex < (int) Block_Size; LeafIndex++) //creates new block.
					HashBlock[LeafIndex] = GetNextLeafHash(); //extracts two leafs to a hash.

				HashValues[i] = CompressHashBlock(HashBlock,Block_Size); //compresses the block to hash.
			}

			if (i < Blocks_Count) HashValues[i] = CompressSmallBlock(); //this block wasn't big enough.
			
			Leaf_Count = Blocks_Count;
		}

		private byte[] GetNextLeafHash() //reads 2 leafs from the file and returns their combined hash.
		{
			byte[] LeafA = new byte[Leaf_Size];
			byte[] LeafB = new byte[Leaf_Size];
				
			
			int DataSize = FilePtr.Read(LeafA,0,Leaf_Size);
			//check if leaf is too small.
			if (DataSize < Leaf_Size) return (LeafHash(ByteExtract(LeafA,DataSize)));

			DataSize = FilePtr.Read(LeafB,0,Leaf_Size);

			if (DataSize < Leaf_Size)
				LeafB = ByteExtract(LeafB,DataSize);

			LeafA = LeafHash(LeafA);
			LeafB = LeafHash(LeafB);

			return InternalHash(LeafA,LeafB); //returns combined hash.
		}

		private byte[] CompressHashBlock(byte[][] HashBlock,int HashCount) //compresses hash blocks to hash.
		{
			if (HashBlock.Length == 0) return null;

			while (HashCount > 1) //until there's only 1 hash.
			{
				int TempBlockSize = (int) HashCount / 2;
				if (HashCount % 2 > 0) TempBlockSize++;

				byte[][] TempBlock = new byte[TempBlockSize][];

				int HashIndex = 0;
				for (int i = 0; i < (int) HashCount / 2; i++) //makes hash from pairs.
				{
					TempBlock[i] = InternalHash(HashBlock[HashIndex],HashBlock[HashIndex+1]);
					HashIndex += 2;
				}
			
				//this one doesn't have a pair :(
				if (HashCount % 2 > 0) TempBlock[TempBlockSize - 1] = HashBlock[HashCount - 1];

				HashBlock = TempBlock;
				HashCount = TempBlockSize;
			}
			return HashBlock[0];
		}

		private byte[] CompressSmallBlock() //compress a small block to hash.
		{
			long DataSize = (long) (FilePtr.Length - FilePtr.Position);
			
			int LeafCount = (int) DataSize / (Leaf_Size * 2);
			if (DataSize % (Leaf_Size * 2) > 0) LeafCount++;

			byte[][] SmallBlock = new byte[LeafCount][];		

			//extracts leafs from file.
			for (int i = 0; i < (int) DataSize / (Leaf_Size * 2); i++)
				SmallBlock[i] = GetNextLeafHash();

			if (DataSize % (Leaf_Size * 2) > 0) SmallBlock[LeafCount - 1] = GetNextLeafHash();

			return CompressHashBlock(SmallBlock,LeafCount); //gets hash from the small block.
		}
		private byte[] InternalHash(byte[] LeafA,byte[] LeafB) //internal hash.
		{ 
			byte[] Data = new byte[LeafA.Length + LeafB.Length + 1];

			Data[0] = 0x01; //internal hash mark.

			//combines two leafs.
			LeafA.CopyTo(Data,1);
			LeafB.CopyTo(Data,LeafA.Length + 1);

			//gets tiger hash value for combined leaf hash.
			Tiger TG = new Tiger();
			TG.Initialize();
			return TG.ComputeHash(Data);			
		}

		private byte[] LeafHash(byte[] Raw_Data) //leaf hash.
		{ 
			byte[] Data = new byte[Raw_Data.Length + 1];

			Data[0] = 0x00; //leaf hash mark.
			Raw_Data.CopyTo(Data,1);

			//gets tiger hash value for leafs blocks.
			Tiger TG = new Tiger();
			TG.Initialize();
			return TG.ComputeHash(Data);
		}

		private byte[] ByteExtract(byte[] Raw_Data,int Data_Length) //if we use the extra 0x00 in Raw_Data we will get wrong hash.
		{
			byte[] Data = new byte[Data_Length];

			for (int i = 0; i < Data_Length; i++)
				Data[i] = Raw_Data[i];

			return Data;
		}
	}
}