WrappedStream.Read C# (CSharp) Method

    public override int Read(byte[] buffer, int offset, int count)
    {
        if (CanRead)
        {
            try
            {
                return _baseStream.Read(buffer, offset, count);
            }
            catch (ObjectDisposedException ex)
            {
                throw new NotSupportedException("This stream does not support reading", ex);
            }
        }
        else throw new NotSupportedException("This stream does not support reading");
    }

        public override int Read(byte[] buffer, int offset, int count)
        {
            int startOffset = (int)(_position % _blockSize);

            if (startOffset == 0 && (count % _blockSize == 0 || _position + count == Length))
            {
                // Aligned read - pass through to underlying stream.
                WrappedStream.Position = _position;
                int numRead = WrappedStream.Read(buffer, offset, count);
                _position += numRead;
                return(numRead);
            }

            long startPos = MathUtilities.RoundDown(_position, _blockSize);
            long endPos   = MathUtilities.RoundUp(_position + count, _blockSize);

            if (endPos - startPos > int.MaxValue)
            {
                throw new IOException("Oversized read, after alignment");
            }

            byte[] tempBuffer = new byte[endPos - startPos];

            WrappedStream.Position = startPos;
            int read      = WrappedStream.Read(tempBuffer, 0, tempBuffer.Length);
            int available = Math.Min(count, read - startOffset);

            Array.Copy(tempBuffer, startOffset, buffer, offset, available);

            _position += available;
            return(available);
        }