HasherManaged.cs :  » Business-Application » DC » DCSharp » Hashing » C# / CSharp Open Source

/*
 * Copyright (C) 2006-2007 Eskil Bylund
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

using System.IO;
using System.Security.Cryptography;
using System.Threading;

namespace DCSharp.Hashing{
  public class HasherManaged : Hasher
  {
    private const int MaxLevels = 10;
    private HashAlgorithm algorithm;
    
    public HasherManaged(HashAlgorithm algorithm)
    {
      this.algorithm = algorithm;
    }
    
    #region Properties
    
    private long bytesRemaining;
    
    public override long BytesRemaining
    {
      get
      {
        return bytesRemaining;
      }
    }
    
    #endregion
    
    #region Methods
    
    public override HashTree Hash(FileInfo fileInfo,
      ManualResetEvent abortHashingEvent)
    {
      try
      {
        return CreateHashTree(fileInfo, abortHashingEvent);
      }
      catch
      {
        bytesRemaining = 0;
        throw;
      }
    }
    
    private HashTree CreateHashTree(FileInfo fileInfo,
      ManualResetEvent abortHashingEvent)
    {
      long blockSize = HashTree.CalculateBlockSize(fileInfo.Length,
        MaxLevels);
      
      HashTree hashTree = new HashTree(algorithm, blockSize);
      
      using (FileStream stream = fileInfo.OpenRead())
      {
        bytesRemaining = stream.Length;
        
        int count;
        byte[] buffer = new byte[HashTree.SegmentSize * 8];
        do
        {
          count = stream.Read(buffer, 0, buffer.Length);
          if (count != 0)
          {
            hashTree.Update(buffer, 0, count);
            bytesRemaining -= count;
          }
        }
        while (count != 0 && !abortHashingEvent.WaitOne(0, false));
      }
      
      // The hashing was aborted
      if (bytesRemaining > 0 || abortHashingEvent.WaitOne(0, false))
      {
        bytesRemaining = 0;
        return null;
      }
      
      hashTree.CalculateRoot();
      return hashTree;
    }
    
    #endregion
  }
}