Passing a C++ Array to C# Layer through Net Core

Question

I have a native library and what I'm trying to do is to write a .NET Core wrapper to this native library.

On the native side i have an event called OnSpeechEnded :

virtual void OnSpeechEnded(SpeechEndInfo seInfo) = 0;

and native struct SpeechEndInfo has the following structure:

struct SpeechEndInfo
{
    std::vector<AudioData> UntouchedData;
    std::vector<AudioData> AudioAfterPostSpeechUntilSilenceTrigger;
};

Corresponding .NET Standard Class:

 public struct SpeechEndedInfo
    {
        public SpeechEndedInfo(short[] untouchedData, short[] audioAfterPostSpeechUntilSilenceTrigger)
        {
            UntouchedData = new short[untouchedData.Length];
            untouchedData.CopyTo(UntouchedData, 0);


            AudioAfterPostSpeechUntilSilenceTrigger = new short[audioAfterPostSpeechUntilSilenceTrigger.Length];
            audioAfterPostSpeechUntilSilenceTrigger.CopyTo(AudioAfterPostSpeechUntilSilenceTrigger, 0);


        }

        public short[] UntouchedData { get; set; }
        public short[] AudioAfterPostSpeechUntilSilenceTrigger { get; set; }
    };

On .NET Standard side, the following delegate is defined:

delegate void OnSpeechEndedInter(
            [In, MarshalAs(UnmanagedType.LPArray)] short[] untouched, 
            int untouchedSize, 
            [In, MarshalAs(UnmanagedType.LPArray)] short[] audioAfterPostSpeechUntilSilenceTrigger,
            int audioAfterPostSpeechUntilSilenceTriggerSize);

Declaring pinvoke:

[DllImport("VadLite.Pinvokable.dll", CallingConvention = CallingConvention.Cdecl)]
        private static extern void RegisterToSpeechEndedEvent(IntPtr parameters, [MarshalAs(UnmanagedType.FunctionPtr)]OnSpeechEndedInter onSpeechEndedInter);

Declaring _onSpeechEndedInter:

 private OnSpeechEndedInter _onSpeechEndedInter;

Assigning a method to the event:

 _onSpeechEndedInter = invokedMethod;

...

void invokedMethod(short[] untouchedData, 
            int untouchedSize, 
            short[] audioAfterPostSpeechUntilSilenceTrigger,
            int audioAfterPostSpeechUntilSilenceTriggerSize)
        {
            OnSpeechEnded?.Invoke(new SpeechEndedInfo(untouchedData, audioAfterPostSpeechUntilSilenceTrigger));
        }

Finally, the code where native arrays are sent:

RegisterToSpeechEndedEvent(
        void * possiblyOperations,
        void __stdcall onSpeechEndedListener(const int16_t* pUntouchedData, int pUntouchedDataSize, const int16_t *vAudioAfterPostSpeechUntilSilenceTrigger, int vAudioAfterPostSpeechUntilSilenceTriggerSize))
    {

        auto op = (OperationParameters *)possiblyOperations;
        op->OnSpeechEnded([onSpeechEndedListener](SpeechEndInfo ssInfo) {


            std::vector<int16_t> untouchedData;
            std::vector<int16_t> audioAfterPostSpeechUntilSilenceTrigger;

            for (auto & audioData : ssInfo.UntouchedData)
            {
                untouchedData.insert(untouchedData.end(), audioData.Samples, audioData.Samples + audioData.SampleCount);
            }


            for (auto & audioData : ssInfo.AudioAfterPostSpeechUntilSilenceTrigger)
            {
                audioAfterPostSpeechUntilSilenceTrigger.insert(audioAfterPostSpeechUntilSilenceTrigger.end(), audioData.Samples, audioData.Samples + audioData.SampleCount);
            }



            onSpeechEndedListener(untouchedData.empty() ? nullptr : untouchedData.data(),
                    (int)untouchedData.size(),
                    audioAfterPostSpeechUntilSilenceTrigger.empty() ? nullptr : audioAfterPostSpeechUntilSilenceTrigger.data(),
                    (int)audioAfterPostSpeechUntilSilenceTrigger.size());

        });

After running the test program and getting meaningful array sizes on the native side, C# arrays UntouchedData and AudioAfterPostSpeechUntilSilenceTrigger always seem to have size 1.

Probably there is a detail I have missed. I can provide further detail if it is required. Thanks.

fatihk · Accepted Answer · 2019-08-09 09:08:24Z

1

Great!, Finally I have found out the problem. In the delegate declaration, I just had to introduce parameter SizeParamIndex :

delegate void OnSpeechEndedInter(
            [In, MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] short[] untouched, 
            int untouchedSize, 
            [In, MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] short[] audioAfterPostSpeechUntilSilenceTrigger,
            int audioAfterPostSpeechUntilSilenceTriggerSize);

Because the marshaler cannot determine the size of an unmanaged array, we have to pass it in as a separate parameter considering the signature of the method and zero based indexing.

answered Aug 9, 2019 at 9:08

fatihk

7,9491 gold badge28 silver badges51 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Passing a C++ Array to C# Layer through Net Core

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related