Buat API Tugas Anda sendiri

Mirip dengan Native API, untuk membangun objek API, klien perlu memberikan informasi berikut dengan memperluas BaseTaskApi , yang menyediakan penanganan JNI untuk semua Java Task API.

• Tentukan I/O API - Ini biasanya mencerminkan antarmuka asli. misalnya BertQuestionAnswerer mengambil (String context, String question) sebagai input dan output List<QaAnswer> . Implementasinya memanggil fungsi asli pribadi dengan tanda tangan yang serupa, kecuali ia memiliki parameter tambahan long nativeHandle , yang merupakan pointer yang dikembalikan dari C++.

  class BertQuestionAnswerer extends BaseTaskApi {
    public List<QaAnswer> answer(String context, String question) {
      return answerNative(getNativeHandle(), context, question);
    }
  
    private static native List<QaAnswer> answerNative(
                                          long nativeHandle, // C++ pointer
                                          String context, String question // API I/O
                                         );
  
  }
  

• Buat fungsi pabrik API - Ini juga mencerminkan fungsi pabrik asli, kecuali fungsi pabrik Android juga perlu mengambil Context untuk akses file. Implementasinya memanggil salah satu utilitas di TaskJniUtils untuk membangun objek C++ API yang sesuai dan meneruskan penunjuknya ke konstruktor BaseTaskApi .

    class BertQuestionAnswerer extends BaseTaskApi {
      private static final String BERT_QUESTION_ANSWERER_NATIVE_LIBNAME =
                                                "bert_question_answerer_jni";
  
      // Extending super constructor by providing the
      // native handle(pointer of corresponding C++ API object)
      private BertQuestionAnswerer(long nativeHandle) {
        super(nativeHandle);
      }
  
      public static BertQuestionAnswerer createBertQuestionAnswerer(
                                          Context context, // Accessing Android files
                                          String pathToModel, String pathToVocab) {
        return new BertQuestionAnswerer(
            // The util first try loads the JNI module with name
            // BERT_QUESTION_ANSWERER_NATIVE_LIBNAME, then opens two files,
            // converts them into ByteBuffer, finally ::initJniWithBertByteBuffers
            // is called with the buffer for a C++ API object pointer
            TaskJniUtils.createHandleWithMultipleAssetFilesFromLibrary(
                context,
                BertQuestionAnswerer::initJniWithBertByteBuffers,
                BERT_QUESTION_ANSWERER_NATIVE_LIBNAME,
                pathToModel,
                pathToVocab));
      }
  
      // modelBuffers[0] is tflite model file buffer, and modelBuffers[1] is vocab file buffer.
      // returns C++ API object pointer casted to long
      private static native long initJniWithBertByteBuffers(ByteBuffer... modelBuffers);
  
    }
  

• Menerapkan modul JNI untuk fungsi asli - Semua metode asli Java diimplementasikan dengan memanggil fungsi asli yang sesuai dari modul JNI. Fungsi pabrik akan membuat objek API asli dan mengembalikan penunjuknya sebagai tipe panjang ke Java. Dalam panggilan selanjutnya ke Java API, penunjuk tipe panjang diteruskan kembali ke JNI dan dilemparkan kembali ke objek API asli. Hasil API asli kemudian dikonversi kembali ke hasil Java.

  Misalnya, ini adalah bagaimana bert_question_answerer_jni diterapkan.

    // Implements BertQuestionAnswerer::initJniWithBertByteBuffers
    extern "C" JNIEXPORT jlong JNICALL
    Java_org_tensorflow_lite_task_text_qa_BertQuestionAnswerer_initJniWithBertByteBuffers(
        JNIEnv* env, jclass thiz, jobjectArray model_buffers) {
      // Convert Java ByteBuffer object into a buffer that can be read by native factory functions
      absl::string_view model =
          GetMappedFileBuffer(env, env->GetObjectArrayElement(model_buffers, 0));
  
      // Creates the native API object
      absl::StatusOr<std::unique_ptr<QuestionAnswerer>> status =
          BertQuestionAnswerer::CreateFromBuffer(
              model.data(), model.size());
      if (status.ok()) {
        // converts the object pointer to jlong and return to Java.
        return reinterpret_cast<jlong>(status->release());
      } else {
        return kInvalidPointer;
      }
    }
  
    // Implements BertQuestionAnswerer::answerNative
    extern "C" JNIEXPORT jobject JNICALL
    Java_org_tensorflow_lite_task_text_qa_BertQuestionAnswerer_answerNative(
    JNIEnv* env, jclass thiz, jlong native_handle, jstring context, jstring question) {
    // Convert long to native API object pointer
    QuestionAnswerer* question_answerer = reinterpret_cast<QuestionAnswerer*>(native_handle);
  
    // Calls the native API
    std::vector<QaAnswer> results = question_answerer->Answer(JStringToString(env, context),
                                           JStringToString(env, question));
  
    // Converts native result(std::vector<QaAnswer>) to Java result(List<QaAnswerer>)
    jclass qa_answer_class =
      env->FindClass("org/tensorflow/lite/task/text/qa/QaAnswer");
    jmethodID qa_answer_ctor =
      env->GetMethodID(qa_answer_class, "<init>", "(Ljava/lang/String;IIF)V");
    return ConvertVectorToArrayList<QaAnswer>(
      env, results,
      [env, qa_answer_class, qa_answer_ctor](const QaAnswer& ans) {
        jstring text = env->NewStringUTF(ans.text.data());
        jobject qa_answer =
            env->NewObject(qa_answer_class, qa_answer_ctor, text, ans.pos.start,
                           ans.pos.end, ans.pos.logit);
        env->DeleteLocalRef(text);
        return qa_answer;
      });
    }
  
    // Implements BaseTaskApi::deinitJni by delete the native object
    extern "C" JNIEXPORT void JNICALL Java_task_core_BaseTaskApi_deinitJni(
        JNIEnv* env, jobject thiz, jlong native_handle) {
      delete reinterpret_cast<QuestionAnswerer*>(native_handle);
    }
  

API iOS

Buat API iOS dengan membungkus objek API asli menjadi objek API ObjC. Objek API yang dibuat dapat digunakan di ObjC atau Swift. iOS API membutuhkan API asli untuk dibuat terlebih dahulu.

Contoh penggunaan

Berikut adalah contoh menggunakan ObjC TFLBertQuestionAnswerer untuk MobileBert di Swift.

  static let mobileBertModelPath = "path/to/model.tflite";
  // Create the API from a model file and vocabulary file
  let mobileBertAnswerer = TFLBertQuestionAnswerer.mobilebertQuestionAnswerer(
      modelPath: mobileBertModelPath)

  static let context = ...; // context of a question to be answered
  static let question = ...; // question to be answered
  // ask a question
  let answers = mobileBertAnswerer.answer(
      context: TFLBertQuestionAnswererTest.context, question: TFLBertQuestionAnswererTest.question)
  // answers.[0].text is the best answer

Membangun API

Gambar 4. API Tugas iOS

iOS API adalah pembungkus ObjC sederhana di atas API asli. Bangun API dengan mengikuti langkah-langkah di bawah ini:

• Tentukan pembungkus ObjC - Tentukan kelas ObjC dan delegasikan implementasinya ke objek API asli yang sesuai. Perhatikan bahwa dependensi asli hanya dapat muncul dalam file .mm karena Swift tidak dapat melakukan interop dengan C++.

  • file .h

    @interface TFLBertQuestionAnswerer : NSObject
  
    // Delegate calls to the native BertQuestionAnswerer::CreateBertQuestionAnswerer
    + (instancetype)mobilebertQuestionAnswererWithModelPath:(NSString*)modelPath
                                                  vocabPath:(NSString*)vocabPath
        NS_SWIFT_NAME(mobilebertQuestionAnswerer(modelPath:vocabPath:));
  
    // Delegate calls to the native BertQuestionAnswerer::Answer
    - (NSArray<TFLQAAnswer*>*)answerWithContext:(NSString*)context
                                       question:(NSString*)question
        NS_SWIFT_NAME(answer(context:question:));
  }
  

  • file .mm

    using BertQuestionAnswererCPP = ::tflite::task::text::BertQuestionAnswerer;
  
    @implementation TFLBertQuestionAnswerer {
      // define an iVar for the native API object
      std::unique_ptr<QuestionAnswererCPP> _bertQuestionAnswerwer;
    }
  
    // Initialize the native API object
    + (instancetype)mobilebertQuestionAnswererWithModelPath:(NSString *)modelPath
                                            vocabPath:(NSString *)vocabPath {
      absl::StatusOr<std::unique_ptr<QuestionAnswererCPP>> cQuestionAnswerer =
          BertQuestionAnswererCPP::CreateBertQuestionAnswerer(MakeString(modelPath),
                                                              MakeString(vocabPath));
      _GTMDevAssert(cQuestionAnswerer.ok(), @"Failed to create BertQuestionAnswerer");
      return [[TFLBertQuestionAnswerer alloc]
          initWithQuestionAnswerer:std::move(cQuestionAnswerer.value())];
    }
  
    // Calls the native API and converts C++ results into ObjC results
    - (NSArray<TFLQAAnswer *> *)answerWithContext:(NSString *)context question:(NSString *)question {
      std::vector<QaAnswerCPP> results =
        _bertQuestionAnswerwer->Answer(MakeString(context), MakeString(question));
      return [self arrayFromVector:results];
    }
  }