read throws exception when sp_nonblocking_read returns negative number in case of error

[cabbi]

This piece of code in util.dart does not handle error code in case sp_nonblocking_read fails

  static Uint8List read(int bytes, UtilFunc<ffi.Uint8> readFunc) {
    return ffi.using((arena) {
      final ptr = arena<ffi.Uint8>(bytes);
      final len = call(() => readFunc(ptr));
      return Uint8List.fromList(ptr.asTypedList(len));
    });
  }

This will fix the error:

      return Uint8List.fromList(ptr.asTypedList(len < 0 ? 0 : len));

[vinsfortunato]

I can confirm having this issue too. A workaround is to check for bytesAvailable before calling the read method in non-blocking mode:

// Check for bytes available before calling read.
if (serialPort.bytesAvailable > 0) {
   var bytes = serialPort.read(amountToRead);
   // Do something with the read bytes
}

However this is definitely not ideal and removing the root cause, as suggested by @cabbi would be better.

[cabbi]

In my case checking for bytesAvailable is not working.

The first read once data is available returns me an empty list and on a second read attempt I get this exception:

errorCode: 996
hashCode: 1152565821
message: "Overlapped I/O event is not in a signaled state."

[micheljung]

I think I'm hitting this as well:

[ERROR:flutter/runtime/dart_isolate.cc(1107)] Unhandled exception:
Invalid argument(s): length must be in the range [0, 4611686018427387903].
#0      _checkExternalTypedDataLength (dart:ffi-patch/ffi_patch.dart:62:5)
#1      Uint8Pointer.asTypedList (dart:ffi-patch/ffi_patch.dart:727:5)
#2      Util.read.<anonymous closure> (package:libserialport/src/util.dart:49:37)
#3      using (package:ffi/src/arena.dart:124:31)
#4      Util.read (package:libserialport/src/util.dart:46:16)
#5      _SerialPortReaderImpl._waitRead (package:libserialport/src/reader.dart:145:27)
#6      _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:300:17)
#7      _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)

len is -2