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      1 /*
      2  * Copyright (C) 2018 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.dx.mockito.inline;
     18 
     19 import android.os.Build;
     20 import android.os.Debug;
     21 
     22 import java.io.IOException;
     23 import java.lang.reflect.InvocationTargetException;
     24 import java.security.ProtectionDomain;
     25 import java.util.ArrayList;
     26 
     27 import dalvik.system.BaseDexClassLoader;
     28 
     29 /**
     30  * Interface to the native jvmti agent in agent.cc
     31  */
     32 class StaticJvmtiAgent {
     33     private static final String AGENT_LIB_NAME = "libstaticjvmtiagent.so";
     34 
     35     private static final Object lock = new Object();
     36 
     37     /**
     38      * Registered byte code transformers
     39      */
     40     private final ArrayList<StaticClassTransformer> transformers = new ArrayList<>();
     41 
     42     /**
     43      * Enable jvmti and load agent.
     44      * <p><b>If there are more than agent transforming classes the other agent might remove
     45      * transformations added by this agent.</b>
     46      *
     47      * @throws IOException If jvmti could not be enabled or agent could not be loaded
     48      */
     49     StaticJvmtiAgent() throws IOException {
     50         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.P) {
     51             throw new IOException("Requires API level " + Build.VERSION_CODES.P + ". API level is "
     52                     + Build.VERSION.SDK_INT);
     53         }
     54 
     55         ClassLoader cl = StaticJvmtiAgent.class.getClassLoader();
     56         if (!(cl instanceof BaseDexClassLoader)) {
     57             throw new IOException("Could not load jvmti plugin as StaticJvmtiAgent class was not loaded "
     58                     + "by a BaseDexClassLoader");
     59         }
     60 
     61         Debug.attachJvmtiAgent(AGENT_LIB_NAME, null, cl);
     62         nativeRegisterTransformerHook();
     63     }
     64 
     65     private native void nativeRegisterTransformerHook();
     66 
     67     private native void nativeUnregisterTransformerHook();
     68 
     69     @Override
     70     protected void finalize() throws Throwable {
     71         nativeUnregisterTransformerHook();
     72     }
     73 
     74     /**
     75      * Ask the agent to trigger transformation of some classes. This will extract the byte code of
     76      * the classes and the call back the {@link #addTransformer(StaticClassTransformer)
     77      * transformers} for each individual class.
     78      *
     79      * @param classes The classes to transform
     80      * @throws UnmodifiableClassException If one of the classes can not be transformed
     81      */
     82     void requestTransformClasses(Class<?>[] classes) throws UnmodifiableClassException {
     83         synchronized (lock) {
     84             try {
     85                 nativeRetransformClasses(classes);
     86             } catch (RuntimeException e) {
     87                 throw new UnmodifiableClassException(e);
     88             }
     89         }
     90     }
     91 
     92     // called by JNI
     93     @SuppressWarnings("unused")
     94     public boolean shouldTransform(Class<?> classBeingRedefined) {
     95         for (StaticClassTransformer transformer : transformers) {
     96             if (transformer.shouldTransform(classBeingRedefined)) {
     97                 return true;
     98             }
     99         }
    100 
    101         return false;
    102     }
    103 
    104     /**
    105      * Register a transformer. These are called for each class when a transformation was triggered
    106      * via {@link #requestTransformClasses(Class[])}.
    107      *
    108      * @param transformer the transformer to add.
    109      */
    110     void addTransformer(StaticClassTransformer transformer) {
    111         transformers.add(transformer);
    112     }
    113 
    114     // called by JNI
    115     @SuppressWarnings("unused")
    116     public byte[] runTransformers(ClassLoader loader, String className,
    117                                   Class<?> classBeingRedefined, ProtectionDomain protectionDomain,
    118                                   byte[] classfileBuffer) throws IllegalClassFormatException {
    119         byte[] transformedByteCode = classfileBuffer;
    120         for (StaticClassTransformer transformer : transformers) {
    121             transformedByteCode = transformer.transform(classBeingRedefined, transformedByteCode);
    122         }
    123 
    124         return transformedByteCode;
    125     }
    126 
    127     private native void nativeRetransformClasses(Class<?>[] classes);
    128 }
    129