test/1975-hello-structural-transformation/src/art/Test1975.java - LeafOS-Project/android_art - Gitiles

 /*
  * 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.
  */

 package art;

 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
 import java.lang.ref.*;
 import java.lang.reflect.*;
 import java.util.*;

 public class Test1975 {
   public static void run() throws Exception {
     Redefinition.setTestConfiguration(Redefinition.Config.COMMON_REDEFINE);
     doTest();
   }

   private static final boolean PRINT_NONDETERMINISTIC = false;

   public static WeakHashMap<Object, Long> id_nums = new WeakHashMap<>();
   public static long next_id = 0;

   public static String printGeneric(Object o) {
     Long id = id_nums.get(o);
     if (id == null) {
       id = Long.valueOf(next_id++);
       id_nums.put(o, id);
     }
     if (o == null) {
       return "(ID: " + id + ") <NULL>";
     }
     Class oc = o.getClass();
     if (oc.isArray() && oc.getComponentType() == Byte.TYPE) {
       return "(ID: "
           + id
           + ") "
           + Arrays.toString(Arrays.copyOf((byte[]) o, 10)).replace(']', ',')
           + " ...]";
     } else {
       return "(ID: " + id + ") " + o.toString();
     }
   }

   // Since we are adding fields we redefine this class with the Transform1975 class to add new
   // field-reads.
   public static final class ReadTransformFields implements Runnable {
     public void run() {
       System.out.println("Read CUR_CLASS field: " + printGeneric(Transform1975.CUR_CLASS));
       System.out.println(
           "Read REDEFINED_DEX_BYTES field: " + printGeneric(Transform1975.REDEFINED_DEX_BYTES));
     }
   }

   /* Base64 encoded dex file for:
    * public static final class ReadTransformFields implements Runnable {
    *   public void run() {
    *     System.out.println("Read CUR_CLASS field: " + printGeneric(Transform1975.CUR_CLASS));
    *     System.out.println("Read REDEFINED_DEX_BYTES field: " + printGeneric(Transform1975.REDEFINED_DEX_BYTES));
    *     System.out.println("Read NEW_STRING field: " + printGeneric(Transform1975.NEW_STRING));
    *   }
    * }
    */
   private static final byte[] NEW_READ_BYTES =
       Base64.getDecoder()
           .decode(
               "ZGV4CjAzNQCHIfWvfkMos9E+Snhux5rSGhnDAbiVJlyYBgAAcAAAAHhWNBIAAAAAAAAAANQFAAAk"
                   + "AAAAcAAAAA4AAAAAAQAABQAAADgBAAAEAAAAdAEAAAgAAACUAQAAAQAAANQBAACkBAAA9AEAAO4C"
                   + "AAD2AgAAAQMAAAQDAAAIAwAALAMAADwDAABRAwAAdQMAAJUDAACsAwAAvwMAANMDAADpAwAA/QMA"
                   + "ABgEAAAsBAAAOAQAAE0EAABlBAAAfgQAAKAEAAC1BAAAxAQAAMcEAADLBAAAzwQAANwEAADkBAAA"
                   + "6gQAAO8EAAD9BAAABgUAAAsFAAAVBQAAHAUAAAQAAAAFAAAABgAAAAcAAAAIAAAACQAAAAoAAAAL"
                   + "AAAADAAAAA0AAAAOAAAADwAAABcAAAAZAAAAAgAAAAkAAAAAAAAAAwAAAAkAAADgAgAAAwAAAAoA"
                   + "AADoAgAAFwAAAAwAAAAAAAAAGAAAAAwAAADoAgAAAgAGAAEAAAACAAkAEAAAAAIADQARAAAACwAF"
                   + "AB0AAAAAAAMAAAAAAAAAAwAgAAAAAQABAB4AAAAFAAQAHwAAAAcAAwAAAAAACgADAAAAAAAKAAIA"
                   + "GwAAAAoAAAAhAAAAAAAAABEAAAAHAAAA2AIAABYAAADEBQAAowUAAAAAAAABAAEAAQAAAMYCAAAE"
                   + "AAAAcBAEAAAADgAFAAEAAgAAAMoCAABVAAAAYgADAGIBAABxEAIAAQAMASICCgBwEAUAAgAaAxIA"
                   + "biAGADIAbiAGABIAbhAHAAIADAFuIAMAEABiAAMAYgECAHEQAgABAAwBIgIKAHAQBQACABoDFABu"
                   + "IAYAMgBuIAYAEgBuEAcAAgAMAW4gAwAQAGIAAwBiAQEAcRACAAEADAEiAgoAcBAFAAIAGgMTAG4g"
                   + "BgAyAG4gBgASAG4QBwACAAwBbiADABAADgAEAA4ABgAOARwPARwPARwPAAABAAAACAAAAAEAAAAH"
                   + "AAAAAQAAAAkABjxpbml0PgAJQ1VSX0NMQVNTAAFMAAJMTAAiTGFydC9UZXN0MTk3NSRSZWFkVHJh"
                   + "bnNmb3JtRmllbGRzOwAOTGFydC9UZXN0MTk3NTsAE0xhcnQvVHJhbnNmb3JtMTk3NTsAIkxkYWx2"
                   + "aWsvYW5ub3RhdGlvbi9FbmNsb3NpbmdDbGFzczsAHkxkYWx2aWsvYW5ub3RhdGlvbi9Jbm5lckNs"
                   + "YXNzOwAVTGphdmEvaW8vUHJpbnRTdHJlYW07ABFMamF2YS9sYW5nL0NsYXNzOwASTGphdmEvbGFu"
                   + "Zy9PYmplY3Q7ABRMamF2YS9sYW5nL1J1bm5hYmxlOwASTGphdmEvbGFuZy9TdHJpbmc7ABlMamF2"
                   + "YS9sYW5nL1N0cmluZ0J1aWxkZXI7ABJMamF2YS9sYW5nL1N5c3RlbTsACk5FV19TVFJJTkcAE1JF"
                   + "REVGSU5FRF9ERVhfQllURVMAFlJlYWQgQ1VSX0NMQVNTIGZpZWxkOiAAF1JlYWQgTkVXX1NUUklO"
                   + "RyBmaWVsZDogACBSZWFkIFJFREVGSU5FRF9ERVhfQllURVMgZmllbGQ6IAATUmVhZFRyYW5zZm9y"
                   + "bUZpZWxkcwANVGVzdDE5NzUuamF2YQABVgACVkwAAltCAAthY2Nlc3NGbGFncwAGYXBwZW5kAARu"
                   + "YW1lAANvdXQADHByaW50R2VuZXJpYwAHcHJpbnRsbgADcnVuAAh0b1N0cmluZwAFdmFsdWUAdn5+"
                   + "RDh7ImNvbXBpbGF0aW9uLW1vZGUiOiJkZWJ1ZyIsIm1pbi1hcGkiOjEsInNoYS0xIjoiYTgzNTJm"
                   + "MjU0ODg1MzYyY2NkOGQ5MDlkMzUyOWM2MDA5NGRkODk2ZSIsInZlcnNpb24iOiIxLjYuMjAtZGV2"
                   + "In0AAgMBIhgBAgQCGgQZHBcVAAABAQCBgAT0AwEBjAQAAAAAAAAAAgAAAJQFAACaBQAAuAUAAAAA"
                   + "AAAAAAAAAAAAABAAAAAAAAAAAQAAAAAAAAABAAAAJAAAAHAAAAACAAAADgAAAAABAAADAAAABQAA"
                   + "ADgBAAAEAAAABAAAAHQBAAAFAAAACAAAAJQBAAAGAAAAAQAAANQBAAABIAAAAgAAAPQBAAADIAAA"
                   + "AgAAAMYCAAABEAAAAwAAANgCAAACIAAAJAAAAO4CAAAEIAAAAgAAAJQFAAAAIAAAAQAAAKMFAAAD"
                   + "EAAAAgAAALQFAAAGIAAAAQAAAMQFAAAAEAAAAQAAANQFAAA=");

   static void ReadFields() throws Exception {
     Runnable r = new ReadTransformFields();
     System.out.println("Reading with reflection.");
     for (Field f : Transform1975.class.getFields()) {
       System.out.println(f.toString() + " = " + printGeneric(f.get(null)));
     }
     System.out.println("Reading normally in same class.");
     Transform1975.readFields();
     System.out.println("Reading with native.");
     readNativeFields(Transform1975.class, getNativeFields(Transform1975.class.getFields()));
     System.out.println("Reading normally in other class.");
     r.run();
     System.out.println("Reading using method handles.");
     readMethodHandles(getMethodHandles(Transform1975.class.getFields()));
     System.out.println("Doing modification maybe");
     Transform1975.doSomething();
     System.out.println("Reading with reflection after possible modification.");
     for (Field f : Transform1975.class.getFields()) {
       System.out.println(f.toString() + " = " + printGeneric(f.get(null)));
     }
     System.out.println("Reading normally in same class after possible modification.");
     Transform1975.readFields();
     System.out.println("Reading with native after possible modification.");
     readNativeFields(Transform1975.class, getNativeFields(Transform1975.class.getFields()));
     System.out.println("Reading normally in other class after possible modification.");
     r.run();
     System.out.println("Reading using method handles.");
     readMethodHandles(getMethodHandles(Transform1975.class.getFields()));
   }

   public static final class MethodHandleWrapper {
     private MethodHandle mh;
     private Field f;
     public MethodHandleWrapper(MethodHandle mh, Field f) {
       this.f = f;
       this.mh = mh;
     }
     public MethodHandle getHandle() {
       return mh;
     }
     public Field getField() {
       return f;
     }
     public Object invoke() throws Throwable {
       return mh.invoke();
     }
     public String toString() {
       return mh.toString();
     }
   }

   public static MethodHandleWrapper[] getMethodHandles(Field[] fields) throws Exception {
     final MethodHandles.Lookup l = MethodHandles.lookup();
     MethodHandleWrapper[] res = new MethodHandleWrapper[fields.length];
     for (int i = 0; i < res.length; i++) {
       res[i] = new MethodHandleWrapper(l.unreflectGetter(fields[i]), fields[i]);;
     }
     return res;
   }

   public static void readMethodHandles(MethodHandleWrapper[] handles) throws Exception {
     for (MethodHandleWrapper h : handles) {
       try {
         System.out.println(printGeneric(h) + " (" + h.getField() + ") = " + printGeneric(h.invoke()));
       } catch (Throwable t) {
         if (t instanceof Exception) {
           throw (Exception)t;
         } else if (t instanceof Error) {
           throw (Error)t;
         } else {
           throw new RuntimeException("Unexpected throwable thrown!", t);
         }
       }
     }
   }
   public static void doTest() throws Exception {
     // TODO It would be good to have a test of invoke-custom too but since that requires smali and
     // internally we just store the resolved MethodHandle this should all be good enough.

     // Grab Field objects from before the transformation.
     Field[] old_fields = Transform1975.class.getFields();
     for (Field f : old_fields) {
       System.out.println("Saving Field object " + printGeneric(f) + " for later");
     }
     // Grab jfieldIDs from before the transformation.
     long[] old_native_fields = getNativeFields(Transform1975.class.getFields());
     // Grab MethodHandles from before the transformation.
     MethodHandleWrapper[] handles = getMethodHandles(Transform1975.class.getFields());
     for (MethodHandleWrapper h : handles) {
       System.out.println("Saving MethodHandle object " + printGeneric(h) + " for later");
     }
     // Grab a 'setter' MethodHandle from before the redefinition.
     Field cur_class_field = Transform1975.class.getDeclaredField("CUR_CLASS");
     MethodHandleWrapper write_wrapper = new MethodHandleWrapper(MethodHandles.lookup().unreflectSetter(cur_class_field), cur_class_field);
     System.out.println("Saving writable MethodHandle " + printGeneric(write_wrapper) + " for later");

     // Read the fields in all possible ways.
     System.out.println("Reading fields before redefinition");
     ReadFields();
     // Redefine the transform class. Also change the ReadTransformFields so we don't have to deal
     // with annoying compilation stuff.
     Redefinition.doCommonStructuralClassRedefinition(
         Transform1975.class, Transform1975.REDEFINED_DEX_BYTES);
     Redefinition.doCommonClassRedefinition(
         ReadTransformFields.class, new byte[] {}, NEW_READ_BYTES);
     // Read the fields in all possible ways.
     System.out.println("Reading fields after redefinition");
     ReadFields();
     // Check that the old Field, jfieldID, and MethodHandle objects were updated.
     System.out.println("reading reflectively with old reflection objects");
     for (Field f : old_fields) {
       System.out.println("OLD FIELD OBJECT: " + f.toString() + " = " + printGeneric(f.get(null)));
     }
     System.out.println("reading natively with old jfieldIDs");
     readNativeFields(Transform1975.class, old_native_fields);
     // Make sure the fields keep the same id.
     System.out.println("reading natively with new jfieldIDs");
     long[] new_fields = getNativeFields(Transform1975.class.getFields());
     Arrays.sort(old_native_fields);
     Arrays.sort(new_fields);
     boolean different = new_fields.length == old_native_fields.length;
     for (int i = 0; i < old_native_fields.length && !different; i++) {
       different = different || new_fields[i] != old_native_fields[i];
     }
     if (different) {
       System.out.println(
           "Missing expected fields! "
               + Arrays.toString(new_fields)
               + " vs "
               + Arrays.toString(old_native_fields));
     }
     // Make sure the old handles work.
     System.out.println("Reading with old method handles");
     readMethodHandles(handles);
     System.out.println("Reading with new method handles");
     readMethodHandles(getMethodHandles(Transform1975.class.getFields()));
     System.out.println("Writing " + printGeneric(Test1975.class) + " to CUR_CLASS with old method handle");
     try {
       write_wrapper.getHandle().invokeExact(Test1975.class);
     } catch (Throwable t) {
       throw new RuntimeException("something threw", t);
     }
     System.out.println("Reading changed value");
     System.out.println("CUR_CLASS is now " + printGeneric(Transform1975.CUR_CLASS));
   }

   private static void printNativeField(long id, Field f, Object value) {
     System.out.println(
         "Field" + (PRINT_NONDETERMINISTIC ? " " + id : "") + " " + f + " = " + printGeneric(value));
   }

   public static native long[] getNativeFields(Field[] fields);

   public static native void readNativeFields(Class<?> field_class, long[] sfields);
 }
	/*
	* 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.
	*/

	package art;

	import java.lang.invoke.MethodHandle;
	import java.lang.invoke.MethodHandles;
	import java.lang.ref.*;
	import java.lang.reflect.*;
	import java.util.*;

	public class Test1975 {
	public static void run() throws Exception {
	Redefinition.setTestConfiguration(Redefinition.Config.COMMON_REDEFINE);
	doTest();
	}

	private static final boolean PRINT_NONDETERMINISTIC = false;

	public static WeakHashMap<Object, Long> id_nums = new WeakHashMap<>();
	public static long next_id = 0;

	public static String printGeneric(Object o) {
	Long id = id_nums.get(o);
	if (id == null) {
	id = Long.valueOf(next_id++);
	id_nums.put(o, id);
	}
	if (o == null) {
	return "(ID: " + id + ") <NULL>";
	}
	Class oc = o.getClass();
	if (oc.isArray() && oc.getComponentType() == Byte.TYPE) {
	return "(ID: "
	+ id
	+ ") "
	+ Arrays.toString(Arrays.copyOf((byte[]) o, 10)).replace(']', ',')
	+ " ...]";
	} else {
	return "(ID: " + id + ") " + o.toString();
	}
	}

	// Since we are adding fields we redefine this class with the Transform1975 class to add new
	// field-reads.
	public static final class ReadTransformFields implements Runnable {
	public void run() {
	System.out.println("Read CUR_CLASS field: " + printGeneric(Transform1975.CUR_CLASS));
	System.out.println(
	"Read REDEFINED_DEX_BYTES field: " + printGeneric(Transform1975.REDEFINED_DEX_BYTES));
	}
	}

	/* Base64 encoded dex file for:
	* public static final class ReadTransformFields implements Runnable {
	* public void run() {
	* System.out.println("Read CUR_CLASS field: " + printGeneric(Transform1975.CUR_CLASS));
	* System.out.println("Read REDEFINED_DEX_BYTES field: " + printGeneric(Transform1975.REDEFINED_DEX_BYTES));
	* System.out.println("Read NEW_STRING field: " + printGeneric(Transform1975.NEW_STRING));
	* }
	* }
	*/
	private static final byte[] NEW_READ_BYTES =
	Base64.getDecoder()
	.decode(
	"ZGV4CjAzNQCHIfWvfkMos9E+Snhux5rSGhnDAbiVJlyYBgAAcAAAAHhWNBIAAAAAAAAAANQFAAAk"
	+ "AAAAcAAAAA4AAAAAAQAABQAAADgBAAAEAAAAdAEAAAgAAACUAQAAAQAAANQBAACkBAAA9AEAAO4C"
	+ "AAD2AgAAAQMAAAQDAAAIAwAALAMAADwDAABRAwAAdQMAAJUDAACsAwAAvwMAANMDAADpAwAA/QMA"
	+ "ABgEAAAsBAAAOAQAAE0EAABlBAAAfgQAAKAEAAC1BAAAxAQAAMcEAADLBAAAzwQAANwEAADkBAAA"
	+ "6gQAAO8EAAD9BAAABgUAAAsFAAAVBQAAHAUAAAQAAAAFAAAABgAAAAcAAAAIAAAACQAAAAoAAAAL"
	+ "AAAADAAAAA0AAAAOAAAADwAAABcAAAAZAAAAAgAAAAkAAAAAAAAAAwAAAAkAAADgAgAAAwAAAAoA"
	+ "AADoAgAAFwAAAAwAAAAAAAAAGAAAAAwAAADoAgAAAgAGAAEAAAACAAkAEAAAAAIADQARAAAACwAF"
	+ "AB0AAAAAAAMAAAAAAAAAAwAgAAAAAQABAB4AAAAFAAQAHwAAAAcAAwAAAAAACgADAAAAAAAKAAIA"
	+ "GwAAAAoAAAAhAAAAAAAAABEAAAAHAAAA2AIAABYAAADEBQAAowUAAAAAAAABAAEAAQAAAMYCAAAE"
	+ "AAAAcBAEAAAADgAFAAEAAgAAAMoCAABVAAAAYgADAGIBAABxEAIAAQAMASICCgBwEAUAAgAaAxIA"
	+ "biAGADIAbiAGABIAbhAHAAIADAFuIAMAEABiAAMAYgECAHEQAgABAAwBIgIKAHAQBQACABoDFABu"
	+ "IAYAMgBuIAYAEgBuEAcAAgAMAW4gAwAQAGIAAwBiAQEAcRACAAEADAEiAgoAcBAFAAIAGgMTAG4g"
	+ "BgAyAG4gBgASAG4QBwACAAwBbiADABAADgAEAA4ABgAOARwPARwPARwPAAABAAAACAAAAAEAAAAH"
	+ "AAAAAQAAAAkABjxpbml0PgAJQ1VSX0NMQVNTAAFMAAJMTAAiTGFydC9UZXN0MTk3NSRSZWFkVHJh"
	+ "bnNmb3JtRmllbGRzOwAOTGFydC9UZXN0MTk3NTsAE0xhcnQvVHJhbnNmb3JtMTk3NTsAIkxkYWx2"
	+ "aWsvYW5ub3RhdGlvbi9FbmNsb3NpbmdDbGFzczsAHkxkYWx2aWsvYW5ub3RhdGlvbi9Jbm5lckNs"
	+ "YXNzOwAVTGphdmEvaW8vUHJpbnRTdHJlYW07ABFMamF2YS9sYW5nL0NsYXNzOwASTGphdmEvbGFu"
	+ "Zy9PYmplY3Q7ABRMamF2YS9sYW5nL1J1bm5hYmxlOwASTGphdmEvbGFuZy9TdHJpbmc7ABlMamF2"
	+ "YS9sYW5nL1N0cmluZ0J1aWxkZXI7ABJMamF2YS9sYW5nL1N5c3RlbTsACk5FV19TVFJJTkcAE1JF"
	+ "REVGSU5FRF9ERVhfQllURVMAFlJlYWQgQ1VSX0NMQVNTIGZpZWxkOiAAF1JlYWQgTkVXX1NUUklO"
	+ "RyBmaWVsZDogACBSZWFkIFJFREVGSU5FRF9ERVhfQllURVMgZmllbGQ6IAATUmVhZFRyYW5zZm9y"
	+ "bUZpZWxkcwANVGVzdDE5NzUuamF2YQABVgACVkwAAltCAAthY2Nlc3NGbGFncwAGYXBwZW5kAARu"
	+ "YW1lAANvdXQADHByaW50R2VuZXJpYwAHcHJpbnRsbgADcnVuAAh0b1N0cmluZwAFdmFsdWUAdn5+"
	+ "RDh7ImNvbXBpbGF0aW9uLW1vZGUiOiJkZWJ1ZyIsIm1pbi1hcGkiOjEsInNoYS0xIjoiYTgzNTJm"
	+ "MjU0ODg1MzYyY2NkOGQ5MDlkMzUyOWM2MDA5NGRkODk2ZSIsInZlcnNpb24iOiIxLjYuMjAtZGV2"
	+ "In0AAgMBIhgBAgQCGgQZHBcVAAABAQCBgAT0AwEBjAQAAAAAAAAAAgAAAJQFAACaBQAAuAUAAAAA"
	+ "AAAAAAAAAAAAABAAAAAAAAAAAQAAAAAAAAABAAAAJAAAAHAAAAACAAAADgAAAAABAAADAAAABQAA"
	+ "ADgBAAAEAAAABAAAAHQBAAAFAAAACAAAAJQBAAAGAAAAAQAAANQBAAABIAAAAgAAAPQBAAADIAAA"
	+ "AgAAAMYCAAABEAAAAwAAANgCAAACIAAAJAAAAO4CAAAEIAAAAgAAAJQFAAAAIAAAAQAAAKMFAAAD"
	+ "EAAAAgAAALQFAAAGIAAAAQAAAMQFAAAAEAAAAQAAANQFAAA=");

	static void ReadFields() throws Exception {
	Runnable r = new ReadTransformFields();
	System.out.println("Reading with reflection.");
	for (Field f : Transform1975.class.getFields()) {
	System.out.println(f.toString() + " = " + printGeneric(f.get(null)));
	}
	System.out.println("Reading normally in same class.");
	Transform1975.readFields();
	System.out.println("Reading with native.");
	readNativeFields(Transform1975.class, getNativeFields(Transform1975.class.getFields()));
	System.out.println("Reading normally in other class.");
	r.run();
	System.out.println("Reading using method handles.");
	readMethodHandles(getMethodHandles(Transform1975.class.getFields()));
	System.out.println("Doing modification maybe");
	Transform1975.doSomething();
	System.out.println("Reading with reflection after possible modification.");
	for (Field f : Transform1975.class.getFields()) {
	System.out.println(f.toString() + " = " + printGeneric(f.get(null)));
	}
	System.out.println("Reading normally in same class after possible modification.");
	Transform1975.readFields();
	System.out.println("Reading with native after possible modification.");
	readNativeFields(Transform1975.class, getNativeFields(Transform1975.class.getFields()));
	System.out.println("Reading normally in other class after possible modification.");
	r.run();
	System.out.println("Reading using method handles.");
	readMethodHandles(getMethodHandles(Transform1975.class.getFields()));
	}

	public static final class MethodHandleWrapper {
	private MethodHandle mh;
	private Field f;
	public MethodHandleWrapper(MethodHandle mh, Field f) {
	this.f = f;
	this.mh = mh;
	}
	public MethodHandle getHandle() {
	return mh;
	}
	public Field getField() {
	return f;
	}
	public Object invoke() throws Throwable {
	return mh.invoke();
	}
	public String toString() {
	return mh.toString();
	}
	}

	public static MethodHandleWrapper[] getMethodHandles(Field[] fields) throws Exception {
	final MethodHandles.Lookup l = MethodHandles.lookup();
	MethodHandleWrapper[] res = new MethodHandleWrapper[fields.length];
	for (int i = 0; i < res.length; i++) {
	res[i] = new MethodHandleWrapper(l.unreflectGetter(fields[i]), fields[i]);;
	}
	return res;
	}

	public static void readMethodHandles(MethodHandleWrapper[] handles) throws Exception {
	for (MethodHandleWrapper h : handles) {
	try {
	System.out.println(printGeneric(h) + " (" + h.getField() + ") = " + printGeneric(h.invoke()));
	} catch (Throwable t) {
	if (t instanceof Exception) {
	throw (Exception)t;
	} else if (t instanceof Error) {
	throw (Error)t;
	} else {
	throw new RuntimeException("Unexpected throwable thrown!", t);
	}
	}
	}
	}
	public static void doTest() throws Exception {
	// TODO It would be good to have a test of invoke-custom too but since that requires smali and
	// internally we just store the resolved MethodHandle this should all be good enough.

	// Grab Field objects from before the transformation.
	Field[] old_fields = Transform1975.class.getFields();
	for (Field f : old_fields) {
	System.out.println("Saving Field object " + printGeneric(f) + " for later");
	}
	// Grab jfieldIDs from before the transformation.
	long[] old_native_fields = getNativeFields(Transform1975.class.getFields());
	// Grab MethodHandles from before the transformation.
	MethodHandleWrapper[] handles = getMethodHandles(Transform1975.class.getFields());
	for (MethodHandleWrapper h : handles) {
	System.out.println("Saving MethodHandle object " + printGeneric(h) + " for later");
	}
	// Grab a 'setter' MethodHandle from before the redefinition.
	Field cur_class_field = Transform1975.class.getDeclaredField("CUR_CLASS");
	MethodHandleWrapper write_wrapper = new MethodHandleWrapper(MethodHandles.lookup().unreflectSetter(cur_class_field), cur_class_field);
	System.out.println("Saving writable MethodHandle " + printGeneric(write_wrapper) + " for later");

	// Read the fields in all possible ways.
	System.out.println("Reading fields before redefinition");
	ReadFields();
	// Redefine the transform class. Also change the ReadTransformFields so we don't have to deal
	// with annoying compilation stuff.
	Redefinition.doCommonStructuralClassRedefinition(
	Transform1975.class, Transform1975.REDEFINED_DEX_BYTES);
	Redefinition.doCommonClassRedefinition(
	ReadTransformFields.class, new byte[] {}, NEW_READ_BYTES);
	// Read the fields in all possible ways.
	System.out.println("Reading fields after redefinition");
	ReadFields();
	// Check that the old Field, jfieldID, and MethodHandle objects were updated.
	System.out.println("reading reflectively with old reflection objects");
	for (Field f : old_fields) {
	System.out.println("OLD FIELD OBJECT: " + f.toString() + " = " + printGeneric(f.get(null)));
	}
	System.out.println("reading natively with old jfieldIDs");
	readNativeFields(Transform1975.class, old_native_fields);
	// Make sure the fields keep the same id.
	System.out.println("reading natively with new jfieldIDs");
	long[] new_fields = getNativeFields(Transform1975.class.getFields());
	Arrays.sort(old_native_fields);
	Arrays.sort(new_fields);
	boolean different = new_fields.length == old_native_fields.length;
	for (int i = 0; i < old_native_fields.length && !different; i++) {
	different = different \|\| new_fields[i] != old_native_fields[i];
	}
	if (different) {
	System.out.println(
	"Missing expected fields! "
	+ Arrays.toString(new_fields)
	+ " vs "
	+ Arrays.toString(old_native_fields));
	}
	// Make sure the old handles work.
	System.out.println("Reading with old method handles");
	readMethodHandles(handles);
	System.out.println("Reading with new method handles");
	readMethodHandles(getMethodHandles(Transform1975.class.getFields()));
	System.out.println("Writing " + printGeneric(Test1975.class) + " to CUR_CLASS with old method handle");
	try {
	write_wrapper.getHandle().invokeExact(Test1975.class);
	} catch (Throwable t) {
	throw new RuntimeException("something threw", t);
	}
	System.out.println("Reading changed value");
	System.out.println("CUR_CLASS is now " + printGeneric(Transform1975.CUR_CLASS));
	}

	private static void printNativeField(long id, Field f, Object value) {
	System.out.println(
	"Field" + (PRINT_NONDETERMINISTIC ? " " + id : "") + " " + f + " = " + printGeneric(value));
	}

	public static native long[] getNativeFields(Field[] fields);

	public static native void readNativeFields(Class<?> field_class, long[] sfields);
	}