src/art/Test1916.java

/*
 * Copyright (C) 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.
 */

package art;

import java.lang.reflect.Constructor;
import java.lang.reflect.Executable;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.util.concurrent.Semaphore;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Set;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.util.function.Consumer;

public class Test1916 {
    public static final int SET_VALUE = 1337;
    public static final String TARGET_VAR = "TARGET";

    public static void reportValue(Object val) {
        System.out.println("\tValue is '" + val + "'");
    }

    public static class IntRunner implements Runnable {
        private volatile boolean continueBusyLoop;
        private volatile boolean inBusyLoop;
        public IntRunner() {
            this.continueBusyLoop = true;
            this.inBusyLoop = false;
        }
        public void run() {
            int TARGET = 42;
            // We will suspend the thread during this loop.
            while (continueBusyLoop) {
                inBusyLoop = true;
            }
            reportValue(TARGET);
        }
        public void waitForBusyLoopStart() { while (!inBusyLoop) {} }
        public void finish() { continueBusyLoop = false; }
    }

    public static void run() throws Exception {
        Locals.EnableLocalVariableAccess();
        runGet();
        runSet();
    }

    public static void runGet() throws Exception {
        Method target = IntRunner.class.getDeclaredMethod("run");
        // Get Int
        IntRunner int_runner = new IntRunner();
        Thread target_get = new Thread(int_runner, "GetLocalInt - Target");
        target_get.start();
        int_runner.waitForBusyLoopStart();
        try {
            Suspension.suspend(target_get);
        } catch (Exception e) {
            System.out.println("FAIL: got " + e);
            e.printStackTrace();
            int_runner.finish();
            target_get.join();
            return;
        }
        try {
            StackTrace.StackFrameData frame = FindStackFrame(target_get, target);
            int depth = frame.depth;
            if (depth != 0) { throw new Error("Expected depth 0 but got " + depth); }
            int slot = FindSlot(frame);
            int value = Locals.GetLocalVariableInt(target_get, depth, slot);
            System.out.println("From GetLocalInt(), value is " + value);
        } finally {
            Suspension.resume(target_get);
            int_runner.finish();
            target_get.join();
        }
    }

    public static void runSet() throws Exception {
        Method target = IntRunner.class.getDeclaredMethod("run");
        // Set Int
        IntRunner int_runner = new IntRunner();
        Thread target_set = new Thread(int_runner, "SetLocalInt - Target");
        target_set.start();
        int_runner.waitForBusyLoopStart();
        try {
            Suspension.suspend(target_set);
        } catch (Exception e) {
            System.out.println("FAIL: got " + e);
            e.printStackTrace();
            int_runner.finish();
            target_set.join();
            return;
        }
        try {
            StackTrace.StackFrameData frame = FindStackFrame(target_set, target);
            int depth = frame.depth;
            if (depth != 0) { throw new Error("Expected depth 0 but got " + depth); }
            int slot = FindSlot(frame);
            System.out.println("Setting TARGET to " + SET_VALUE);
            Locals.SetLocalVariableInt(target_set, depth, slot, SET_VALUE);
        } finally {
            Suspension.resume(target_set);
            int_runner.finish();
            target_set.join();
        }
    }

    public static int FindSlot(StackTrace.StackFrameData frame) throws Exception {
        long loc = frame.current_location;
        for (Locals.VariableDescription var : Locals.GetLocalVariableTable(frame.method)) {
            if (var.start_location <= loc &&
                    var.length + var.start_location > loc &&
                    var.name.equals(TARGET_VAR)) {
                return var.slot;
            }
        }
        throw new Error(
                "Unable to find variable " + TARGET_VAR + " in " + frame.method + " at loc " + loc);
    }

    private static StackTrace.StackFrameData FindStackFrame(Thread thr, Method target) {
        for (StackTrace.StackFrameData frame : StackTrace.GetStackTrace(thr)) {
            if (frame.method.equals(target)) {
                return frame;
            }
        }
        throw new Error("Unable to find stack frame in method " + target + " on thread " + thr);
    }
}