ART: Add GetClassSignature

Add support to retrieve the signature of a JNI class.

Add a test.

Bug: 31684578
Test: m test-art-host-run-test-912-classes
Change-Id: I1cf946996f9089cb5d41e93b4f1064193e9d6350
diff --git a/test/912-classes/classes.cc b/test/912-classes/classes.cc
new file mode 100644
index 0000000..4bf329c
--- /dev/null
+++ b/test/912-classes/classes.cc
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2013 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 "classes.h"
+
+#include <stdio.h>
+
+#include "base/macros.h"
+#include "jni.h"
+#include "openjdkjvmti/jvmti.h"
+#include "ScopedLocalRef.h"
+
+#include "ti-agent/common_load.h"
+
+namespace art {
+namespace Test912Classes {
+
+extern "C" JNIEXPORT jobjectArray JNICALL Java_Main_getClassSignature(
+    JNIEnv* env, jclass Main_klass ATTRIBUTE_UNUSED, jclass klass) {
+  char* sig;
+  char* gen;
+  jvmtiError result = jvmti_env->GetClassSignature(klass, &sig, &gen);
+  if (result != JVMTI_ERROR_NONE) {
+    char* err;
+    jvmti_env->GetErrorName(result, &err);
+    printf("Failure running GetClassSignature: %s\n", err);
+    return nullptr;
+  }
+
+  ScopedLocalRef<jclass> obj_class(env, env->FindClass("java/lang/String"));
+  if (obj_class.get() == nullptr) {
+    return nullptr;
+  }
+
+  jobjectArray ret = env->NewObjectArray(2, obj_class.get(), nullptr);
+  if (ret == nullptr) {
+    return ret;
+  }
+
+  ScopedLocalRef<jstring> sig_str(env, sig == nullptr ? nullptr : env->NewStringUTF(sig));
+  ScopedLocalRef<jstring> gen_str(env, gen == nullptr ? nullptr : env->NewStringUTF(gen));
+
+  env->SetObjectArrayElement(ret, 0, sig_str.get());
+  env->SetObjectArrayElement(ret, 1, gen_str.get());
+
+  // Need to deallocate the strings.
+  if (sig != nullptr) {
+    jvmti_env->Deallocate(reinterpret_cast<unsigned char*>(sig));
+  }
+  if (gen != nullptr) {
+    jvmti_env->Deallocate(reinterpret_cast<unsigned char*>(gen));
+  }
+
+  return ret;
+}
+
+// Don't do anything
+jint OnLoad(JavaVM* vm,
+            char* options ATTRIBUTE_UNUSED,
+            void* reserved ATTRIBUTE_UNUSED) {
+  if (vm->GetEnv(reinterpret_cast<void**>(&jvmti_env), JVMTI_VERSION_1_0)) {
+    printf("Unable to get jvmti env!\n");
+    return 1;
+  }
+  return 0;
+}
+
+}  // namespace Test912Classes
+}  // namespace art