Add a new NNAPI sample for R features.

Add a new sample app demonstrating the usage of the NNAPI R features.

Additionally rename the directory and fix some typos.

nn-samples/basic/src/main/cpp/nn_sample.cpp

@@ -0,0 +1,89 @@
+/**
+ * Copyright 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <jni.h>
+#include <string>
+#include <iomanip>
+#include <sstream>
+#include <fcntl.h>
+
+#include <android/asset_manager_jni.h>
+#include <android/log.h>
+#include <android/sharedmem.h>
+#include <sys/mman.h>
+
+#include "simple_model.h"
+
+extern "C"
+JNIEXPORT jlong
+JNICALL
+Java_com_example_android_basic_MainActivity_initModel(
+        JNIEnv *env,
+        jobject /* this */,
+        jobject _assetManager,
+        jstring _assetName) {
+    // Get the file descriptor of the model data file.
+    AAssetManager *assetManager = AAssetManager_fromJava(env, _assetManager);
+    const char *assetName = env->GetStringUTFChars(_assetName, NULL);
+    AAsset *asset = AAssetManager_open(assetManager, assetName, AASSET_MODE_BUFFER);
+    if(asset == nullptr) {
+        __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, "Failed to open the asset.");
+        return 0;
+    }
+    env->ReleaseStringUTFChars(_assetName, assetName);
+    off_t offset, length;
+    int fd = AAsset_openFileDescriptor(asset, &offset, &length);
+    AAsset_close(asset);
+    if (fd < 0) {
+        __android_log_print(ANDROID_LOG_ERROR, LOG_TAG,
+                            "Failed to open the model_data file descriptor.");
+        return 0;
+    }
+    SimpleModel* nn_model = new SimpleModel(length, PROT_READ, fd, offset);
+    if (!nn_model->CreateCompiledModel()) {
+        __android_log_print(ANDROID_LOG_ERROR, LOG_TAG,
+                            "Failed to prepare the model.");
+        return 0;
+    }
+
+    return (jlong)(uintptr_t)nn_model;
+}
+
+extern "C"
+JNIEXPORT jfloat
+JNICALL
+Java_com_example_android_basic_MainActivity_startCompute(
+        JNIEnv *env,
+        jobject /* this */,
+        jlong _nnModel,
+        jfloat inputValue1,
+        jfloat inputValue2) {
+    SimpleModel* nn_model = (SimpleModel*) _nnModel;
+    float result = 0.0f;
+    nn_model->Compute(inputValue1, inputValue2, &result);
+    return result;
+}
+
+extern "C"
+JNIEXPORT void
+JNICALL
+Java_com_example_android_basic_MainActivity_destroyModel(
+        JNIEnv *env,
+        jobject /* this */,
+        jlong _nnModel) {
+    SimpleModel* nn_model = (SimpleModel*) _nnModel;
+    delete(nn_model);
+}