Android method metadata

extension/android/BUCK

@@ -8,6 +8,7 @@ non_fbcode_target(_kind = fb_android_library,
     srcs = [
         "executorch_android/src/main/java/org/pytorch/executorch/DType.java",
         "executorch_android/src/main/java/org/pytorch/executorch/EValue.java",
+        "executorch_android/src/main/java/org/pytorch/executorch/MethodMetadata.java",
         "executorch_android/src/main/java/org/pytorch/executorch/Module.java",
         "executorch_android/src/main/java/org/pytorch/executorch/Tensor.java",
         "executorch_android/src/main/java/org/pytorch/executorch/annotations/Experimental.java",

extension/android/executorch_android/src/androidTest/java/org/pytorch/executorch/ModuleE2ETest.kt

@@ -69,7 +69,7 @@ class ModuleE2ETest {
 
         val module = Module.load(getTestFilePath("/mv3_xnnpack_fp32.pte"))
         val expectedBackends = arrayOf("XnnpackBackend")
-        Assert.assertArrayEquals(expectedBackends, module.getUsedBackends("forward"))
+        Assert.assertArrayEquals(expectedBackends, module.getMethodMetadata("forward").getBackends())
     }
 
     @Test

extension/android/executorch_android/src/androidTest/java/org/pytorch/executorch/ModuleInstrumentationTest.kt

@@ -55,6 +55,15 @@ class ModuleInstrumentationTest {
         Assert.assertTrue(results[0].isTensor)
     }
 
+    @Test
+    @Throws(IOException::class, URISyntaxException::class)
+    fun testMethodMetadata() {
+        val module = Module.load(getTestFilePath(TEST_FILE_NAME))
+
+        Assert.assertArrayEquals(arrayOf("forward"), module.getMethods())
+        Assert.assertTrue(module.getMethodMetadata("forward").backends.isEmpty())
+    }
+
     @Test
     @Throws(IOException::class)
     fun testModuleLoadMethodAndForward() {
@@ -91,7 +100,7 @@ class ModuleInstrumentationTest {
         Assert.assertEquals(loadMethod.toLong(), INVALID_ARGUMENT.toLong())
     }
 
-    @Test
+    @Test(expected = RuntimeException::class)
     @Throws(IOException::class)
     fun testNonPteFile() {
         val module = Module.load(getTestFilePath(NON_PTE_FILE_NAME))

extension/android/executorch_android/src/main/java/org/pytorch/executorch/MethodMetadata.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package org.pytorch.executorch;
+
+/** Helper class to access the metadata for a method from a Module */
+public class MethodMetadata {
+  private String mName;
+
+  private String[] mBackends;
+
+  MethodMetadata setName(String name) {
+    mName = name;
+    return this;
+  }
+
+  /**
+   * @return Method name
+   */
+  public String getName() {
+    return mName;
+  }
+
+  MethodMetadata setBackends(String[] backends) {
+    mBackends = backends;
+    return this;
+  }
+
+  /**
+   * @return Backends used for this method
+   */
+  public String[] getBackends() {
+    return mBackends;
+  }
+}

extension/android/executorch_android/src/main/java/org/pytorch/executorch/Module.java

@@ -14,6 +14,8 @@
 import com.facebook.soloader.nativeloader.NativeLoader;
 import com.facebook.soloader.nativeloader.SystemDelegate;
 import java.io.File;
+import java.util.HashMap;
+import java.util.Map;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import org.pytorch.executorch.annotations.Experimental;
@@ -48,12 +50,27 @@ public class Module {
 
   private final HybridData mHybridData;
 
+  private final Map<String, MethodMetadata> mMethodMetadata;
+
   @DoNotStrip
   private static native HybridData initHybrid(
       String moduleAbsolutePath, int loadMode, int initHybrid);
 
   private Module(String moduleAbsolutePath, int loadMode, int numThreads) {
     mHybridData = initHybrid(moduleAbsolutePath, loadMode, numThreads);
+
+    mMethodMetadata = populateMethodMeta();
+  }
+
+  Map<String, MethodMetadata> populateMethodMeta() {
+    String[] methods = getMethods();
+    Map<String, MethodMetadata> metadata = new HashMap<String, MethodMetadata>();
+    for (int i = 0; i < methods.length; i++) {
+      String name = methods[i];
+      metadata.put(name, new MethodMetadata().setName(name).setBackends(getUsedBackends(name)));
+    }
+
+    return metadata;
   }
 
   /** Lock protecting the non-thread safe methods in mHybridData. */
@@ -158,13 +175,34 @@ public int loadMethod(String methodName) {
   private native int loadMethodNative(String methodName);
 
   /**
-   * Returns the names of the methods in a certain method.
+   * Returns the names of the backends in a certain method.
    *
    * @param methodName method name to query
    * @return an array of backend name
    */
   @DoNotStrip
-  public native String[] getUsedBackends(String methodName);
+  private native String[] getUsedBackends(String methodName);
+
+  /**
+   * Returns the names of methods.
+   *
+   * @return name of methods in this Module
+   */
+  @DoNotStrip
+  public native String[] getMethods();
+
+  /**
+   * Get the corresponding @MethodMetadata for a method
+   *
+   * @param name method name
+   * @return @MethodMetadata for this method
+   */
+  public MethodMetadata getMethodMetadata(String name) {
+    if (!mMethodMetadata.containsKey(name)) {
+      throw new RuntimeException("method " + name + "does not exist for this module");
+    }
+    return mMethodMetadata.get(name);
+  }
 
   /** Retrieve the in-memory log buffer, containing the most recent ExecuTorch log entries. */
   public String[] readLogBuffer() {

extension/android/jni/jni_layer.cpp

@@ -431,6 +431,26 @@ class ExecuTorchJni : public facebook::jni::HybridClass<ExecuTorchJni> {
     return false;
   }
 
+  facebook::jni::local_ref<facebook::jni::JArrayClass<jstring>> getMethods() {
+    const auto& names_result = module_->method_names();
+    if (!names_result.ok()) {
+      facebook::jni::throwNewJavaException(
+          facebook::jni::gJavaLangIllegalArgumentException,
+          "Cannot get load module");
+    }
+    const auto& methods = names_result.get();
+    facebook::jni::local_ref<facebook::jni::JArrayClass<jstring>> ret =
+        facebook::jni::JArrayClass<jstring>::newArray(methods.size());
+    int i = 0;
+    for (auto s : methods) {
+      facebook::jni::local_ref<facebook::jni::JString> method_name =
+          facebook::jni::make_jstring(s.c_str());
+      (*ret)[i] = method_name;
+      i++;
+    }
+    return ret;
+  }
+
   facebook::jni::local_ref<facebook::jni::JArrayClass<jstring>> getUsedBackends(
       facebook::jni::alias_ref<jstring> methodName) {
     auto methodMeta = module_->method_meta(methodName->toStdString()).get();
@@ -458,6 +478,7 @@ class ExecuTorchJni : public facebook::jni::HybridClass<ExecuTorchJni> {
         makeNativeMethod("loadMethodNative", ExecuTorchJni::load_method),
         makeNativeMethod("readLogBufferNative", ExecuTorchJni::readLogBuffer),
         makeNativeMethod("etdump", ExecuTorchJni::etdump),
+        makeNativeMethod("getMethods", ExecuTorchJni::getMethods),
         makeNativeMethod("getUsedBackends", ExecuTorchJni::getUsedBackends),
     });
   }