void PreLoad(int count)
{
var remainInBuffer = (int)(_mem.Length - _mem.Position);
var buffer = _buffer;
if (remainInBuffer > 0)
{
Array.Copy(buffer, _mem.Position, buffer, 0, remainInBuffer);
}
_mem.SetLength(remainInBuffer);
_mem.Seek(remainInBuffer, SeekOrigin.Begin);
var downloadFrom = _position + remainInBuffer;
var availableInStream = _max - downloadFrom;
var bufferSize = _buffer.Length;
var download = Math.Min(bufferSize - remainInBuffer, availableInStream);
if (count > (remainInBuffer + download))
{
var message = string.Format(
"Buffer is too small. Cached {0}, requested {1}, cap {2}",
remainInBuffer, count,
_buffer.Length);
throw new InvalidOperationException(message);
}
_reader.DownloadRangeToStream(_mem, downloadFrom, (int)download);
_mem.Seek(0, SeekOrigin.Begin);
}
