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public class ASyncFileHashAlgorithm
{
protected HashAlgorithm hashAlgorithm;
protected byte[] hash;
protected bool cancel = false;
protected int bufferSize = 4096;
public delegate void FileHashingProgressHandler (object sender, FileHashingProgressArgs e);
public event FileHashingProgressHandler FileHashingProgress;
public ASyncFileHashAlgorithm(HashAlgorithm hashAlgorithm)
{
this.hashAlgorithm = hashAlgorithm;
}
public byte[] ComputeHash(Stream stream)
{
cancel = false;
hash = null;
int _bufferSize = bufferSize; // this makes it impossible to change the buffer size while computing
byte[] readAheadBuffer, buffer;
int readAheadBytesRead, bytesRead;
long size, totalBytesRead = 0;
size = stream.Length;
readAheadBuffer = new byte[_bufferSize];
readAheadBytesRead = stream.Read(readAheadBuffer, 0, readAheadBuffer.Length);
totalBytesRead += readAheadBytesRead;
do
{
bytesRead = readAheadBytesRead;
buffer = readAheadBuffer;
readAheadBuffer = new byte[_bufferSize];
readAheadBytesRead = stream.Read(readAheadBuffer, 0, readAheadBuffer.Length);
totalBytesRead += readAheadBytesRead;
if (readAheadBytesRead == 0)
hashAlgorithm.TransformFinalBlock(buffer, 0, bytesRead);
else
hashAlgorithm.TransformBlock(buffer, 0, bytesRead, buffer, 0);
FileHashingProgress(this, new FileHashingProgressArgs(totalBytesRead, size));
} while (readAheadBytesRead != 0 && !cancel);
if(cancel)
return hash = null;
return hash = hashAlgorithm.Hash;
}
public int BufferSize
{
get
{ return bufferSize; }
set
{ bufferSize = value; }
}
public byte[] Hash
{
get
{ return hash; }
}
public void Cancel()
{
cancel = true;
}
public override string ToString ()
{
string hex = "";
foreach(byte b in Hash)
hex += b.ToString("x2");
return hex;
}
}
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