System.IO.Pipes.PipeStream.ReadFileNative C# (CSharp) Method

        private unsafe int ReadFileNative(SafePipeHandle handle, byte[] buffer, int offset, int count,
                NativeOverlapped* overlapped, out int errorCode)
        {
            DebugAssertReadWriteArgs(buffer, offset, count, handle);
            Debug.Assert((_isAsync && overlapped != null) || (!_isAsync && overlapped == null), "Async IO parameter screwup in call to ReadFileNative.");

            // You can't use the fixed statement on an array of length 0. Note that async callers
            // check to avoid calling this first, so they can call user's callback
            if (buffer.Length == 0)
            {
                errorCode = 0;
                return 0;
            }

            int r = 0;
            int numBytesRead = 0;

            fixed (byte* p = buffer)
            {
                if (_isAsync)
                {
                    r = Interop.Kernel32.ReadFile(handle, p + offset, count, IntPtr.Zero, overlapped);
                }
                else
                {
                    r = Interop.Kernel32.ReadFile(handle, p + offset, count, out numBytesRead, IntPtr.Zero);
                }
            }

            if (r == 0)
            {
                errorCode = Marshal.GetLastWin32Error();

                // In message mode, the ReadFile can inform us that there is more data to come.
                if (errorCode == Interop.Errors.ERROR_MORE_DATA)
                {
                    return numBytesRead;
                }

                return -1;
            }
            else
            {
                errorCode = 0;
            }

            return numBytesRead;
        }