Cleanup of redefinition testing

Move redefine logic into a single common function and perform some
other cleanup.

Test: mma -j40 test-art-host
Change-Id: I8618bda4f392b683ce198374066e356b87578e7b
diff --git a/test/ti-agent/common_helper.cc b/test/ti-agent/common_helper.cc
new file mode 100644
index 0000000..3e2b168
--- /dev/null
+++ b/test/ti-agent/common_helper.cc
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2016 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 "ti-agent/common_helper.h"
+
+#include <stdio.h>
+
+#include "jni.h"
+#include "openjdkjvmti/jvmti.h"
+#include "ti-agent/common_load.h"
+#include "utils.h"
+
+namespace art {
+bool RuntimeIsJVM;
+
+bool IsJVM() {
+  return RuntimeIsJVM;
+}
+
+void SetAllCapabilities(jvmtiEnv* env) {
+  jvmtiCapabilities caps;
+  env->GetPotentialCapabilities(&caps);
+  env->AddCapabilities(&caps);
+}
+
+namespace common_redefine {
+
+using RedefineDirectFunction = jvmtiError (*)(jvmtiEnv*, jclass, jint, const unsigned char*);
+static void DoClassTransformation(jvmtiEnv* jvmti_env, JNIEnv* env,
+                                  jclass target,
+                                  jbyteArray class_file_bytes,
+                                  jbyteArray dex_file_bytes) {
+  jbyteArray desired_array = IsJVM() ? class_file_bytes : dex_file_bytes;
+  jint len = static_cast<jint>(env->GetArrayLength(desired_array));
+  const unsigned char* redef_bytes = reinterpret_cast<const unsigned char*>(
+      env->GetByteArrayElements(desired_array, nullptr));
+  jvmtiError res;
+  if (IsJVM()) {
+    jvmtiClassDefinition def;
+    def.klass = target;
+    def.class_byte_count = static_cast<jint>(len);
+    def.class_bytes = redef_bytes;
+    res = jvmti_env->RedefineClasses(1, &def);
+  } else {
+    RedefineDirectFunction f =
+        reinterpret_cast<RedefineDirectFunction>(jvmti_env->functions->reserved3);
+    res = f(jvmti_env, target, len, redef_bytes);
+  }
+  if (res != JVMTI_ERROR_NONE) {
+    printf("Redefinition failed!");
+  }
+}
+
+// Magic JNI export that classes can use for redefining classes.
+// To use classes should declare this as a native function with signature (Ljava/lang/Class;[B[B)V
+extern "C" JNIEXPORT void JNICALL Java_Main_doCommonClassRedefinition(JNIEnv* env,
+                                                                      jclass,
+                                                                      jclass target,
+                                                                      jbyteArray class_file_bytes,
+                                                                      jbyteArray dex_file_bytes) {
+  DoClassTransformation(jvmti_env, env, target, class_file_bytes, dex_file_bytes);
+}
+
+// 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;
+  }
+  SetAllCapabilities(jvmti_env);
+  return 0;
+}
+
+}  // namespace common_redefine
+
+}  // namespace art