Library.Io.UnbufferedFileStream.Read C# (CSharp) Method

        public override int Read(byte[] buffer, int offset, int count)
        {
            if (_disposed) throw new ObjectDisposedException(this.GetType().FullName);
            if (offset < 0 || buffer.Length < offset) throw new ArgumentOutOfRangeException(nameof(offset));
            if (count < 0 || (buffer.Length - offset) < count) throw new ArgumentOutOfRangeException(nameof(count));
            if (count == 0) return 0;

            if (_blockInfo.IsUpdated)
            {
                this.Flush();
            }

            count = (int)Math.Min(count, _length - _position);

            int readSumLength = 0;

            while (count > 0)
            {
                long p = (_position / SectorSize) * SectorSize;

                if (_blockInfo.Position != p)
                {
                    _blockInfo.Position = p;
                    _blockInfo.Offset = 0;

                    _stream.Seek(_blockInfo.Position, SeekOrigin.Begin);

                    var readLength = _stream.Read(_blockInfo.Value, 0, SectorSize);
                    readLength = (int)Math.Min(_length - _blockInfo.Position, readLength);

                    _blockInfo.Count = readLength;
                }

                int blockReadPosition = (int)(_position - p);
                int length = Math.Min(SectorSize - blockReadPosition, count);
                Unsafe.Copy(_blockInfo.Value, blockReadPosition, buffer, offset, length);

                offset += length;
                count -= length;

                _position += length;

                readSumLength += length;
            }

            return readSumLength;
        }