Possible to calculate MD5 (or other) hash with buffered reads?

Question

I need to calculate checksums of quite large files (gigabytes). This can be accomplished using the following method:

    private byte[] calcHash(string file         


        

Answer 1

I've just had to do something similar, but wanted to read the file asynchronously. It's using TransformBlock and TransformFinalBlock and is giving me answers consistent with Azure, so I think it is correct!

private static async Task CalculateMD5Async(string fullFileName)
{
  var block = ArrayPool.Shared.Rent(8192);
  try
  {
     using (var md5 = MD5.Create())
     {
         using (var stream = new FileStream(fullFileName, FileMode.Open, FileAccess.Read, FileShare.Read, 8192, true))
         {
            int length;
            while ((length = await stream.ReadAsync(block, 0, block.Length).ConfigureAwait(false)) > 0)
            {
               md5.TransformBlock(block, 0, length, null, 0);
            }
            md5.TransformFinalBlock(block, 0, 0);
         }
         var hash = md5.Hash;
         return Convert.ToBase64String(hash);
      }
   }
   finally
   {
      ArrayPool.Shared.Return(block);
   }
}