/// <summary>
/// Asynchronously reads bytes from the stream into the provided buffer.
/// </summary>
/// <param name="buffer">The buffer to read bytes into.</param>
/// <param name="offset">The offset in the buffer which is where bytes will be written to.</param>
/// <param name="count">The maximum number of bytes to read.</param>
/// <param name="cancellationToken">A cancellation token.</param>
/// <returns>The number of bytes read into the buffer.</returns>
public override async Task <int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
{
var actualCount = count;
if (Position + count > Length)
{
actualCount = (int)(Length - Position);
}
if (actualCount <= 0)
{
return(0);
}
return(await _rangeReader.ReadAsync(_position, buffer, offset, actualCount));
}
private async Task <int> GetBufferOffsetAsync(int count)
{
if (Position >= Length)
{
return(-1);
}
if (Position < BufferPosition)
{
// Determine the read offset by setting a desired buffer size.
var desiredBufferSize = Math.Max(count, _bufferSizeProvider.GetNextBufferSize());
if (desiredBufferSize > Length)
{
desiredBufferSize = (int)Length;
}
var available = Length - Position;
long readOffset;
if (available < desiredBufferSize)
{
readOffset = Math.Max(0, Length - desiredBufferSize);
}
else
{
readOffset = Position;
}
// Read up until the old position (or up to the end, if this is the first read).
var readCount = (int)(BufferPosition - readOffset);
var newBuffer = new byte[readCount];
var actualRead = await _rangeReader.ReadAsync(readOffset, newBuffer, 0, readCount);
_buffer.Prepend(newBuffer);
BufferPosition = readOffset;
}
return((int)(Position - BufferPosition));
}