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/*
* Copyright (C) 2018 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 transformer;
import annotations.BootstrapMethod;
import annotations.CalledByIndy;
import annotations.Constant;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.invoke.MethodType;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.HashMap;
import java.util.Map;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Handle;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
/**
* Class for inserting invoke-dynamic instructions in annotated Java class files.
*
* <p>This class replaces static method invocations of annotated methods with invoke-dynamic
* instructions. Suppose a method is annotated as: <code>
*
* @CalledByIndy(
* bootstrapMethod =
* @BootstrapMethod(
* enclosingType = TestLinkerMethodMinimalArguments.class,
* parameterTypes = {MethodHandles.Lookup.class, String.class, MethodType.class},
* name = "linkerMethod"
* ),
* fieldOdMethodName = "magicAdd",
* returnType = int.class,
* argumentTypes = {int.class, int.class}
* )
* private int add(int x, int y) {
* throw new UnsupportedOperationException(e);
* }
*
* private int magicAdd(int x, int y) {
* return x + y;
* }
*
* </code> Then invokestatic bytecodes targeting the add() method will be replaced invokedynamic
* instructions targetting the CallSite that is construction by the bootstrap method described by
* the @CalledByIndy annotation.
*
* <p>In the example above, this results in add() being replaced by invocations of magicAdd().
*/
public class IndyTransformer {
static class BootstrapBuilder extends ClassVisitor {
private final Map<String, CalledByIndy> callsiteMap;
private final Map<String, Handle> bsmMap = new HashMap<>();
public BootstrapBuilder(int api, Map<String, CalledByIndy> callsiteMap) {
this(api, null, callsiteMap);
}
public BootstrapBuilder(int api, ClassVisitor cv, Map<String, CalledByIndy> callsiteMap) {
super(api, cv);
this.callsiteMap = callsiteMap;
}
@Override
public MethodVisitor visitMethod(
int access, String name, String desc, String signature, String[] exceptions) {
MethodVisitor mv = cv.visitMethod(access, name, desc, signature, exceptions);
return new MethodVisitor(this.api, mv) {
@Override
public void visitMethodInsn(
int opcode, String owner, String name, String desc, boolean itf) {
if (opcode == org.objectweb.asm.Opcodes.INVOKESTATIC) {
CalledByIndy callsite = callsiteMap.get(name);
if (callsite != null) {
insertIndy(callsite.fieldOrMethodName(), desc, callsite);
return;
}
}
mv.visitMethodInsn(opcode, owner, name, desc, itf);
}
private void insertIndy(String name, String desc, CalledByIndy callsite) {
Handle bsm = buildBootstrapMethodHandle(callsite.bootstrapMethod()[0]);
Object[] bsmArgs =
buildBootstrapArguments(callsite.constantArgumentsForBootstrapMethod());
mv.visitInvokeDynamicInsn(name, desc, bsm, bsmArgs);
}
private Handle buildBootstrapMethodHandle(BootstrapMethod bootstrapMethod) {
String className = Type.getInternalName(bootstrapMethod.enclosingType());
String methodName = bootstrapMethod.name();
String methodType =
MethodType.methodType(
bootstrapMethod.returnType(),
bootstrapMethod.parameterTypes())
.toMethodDescriptorString();
return new Handle(
Opcodes.H_INVOKESTATIC,
className,
methodName,
methodType,
false /* itf */);
}
private Object decodeConstant(int index, Constant constant) {
if (constant.booleanValue().length == 1) {
return constant.booleanValue()[0];
} else if (constant.byteValue().length == 1) {
return constant.byteValue()[0];
} else if (constant.charValue().length == 1) {
return constant.charValue()[0];
} else if (constant.shortValue().length == 1) {
return constant.shortValue()[0];
} else if (constant.intValue().length == 1) {
return constant.intValue()[0];
} else if (constant.longValue().length == 1) {
return constant.longValue()[0];
} else if (constant.floatValue().length == 1) {
return constant.floatValue()[0];
} else if (constant.doubleValue().length == 1) {
return constant.doubleValue()[0];
} else if (constant.stringValue().length == 1) {
return constant.stringValue()[0];
} else if (constant.classValue().length == 1) {
return Type.getType(constant.classValue()[0]);
} else {
throw new Error("Bad constant at index " + index);
}
}
private Object[] buildBootstrapArguments(Constant[] bootstrapMethodArguments) {
Object[] args = new Object[bootstrapMethodArguments.length];
for (int i = 0; i < bootstrapMethodArguments.length; ++i) {
args[i] = decodeConstant(i, bootstrapMethodArguments[i]);
}
return args;
}
};
}
}
private static void transform(Path inputClassPath, Path outputClassPath) throws Throwable {
URL url = inputClassPath.getParent().toUri().toURL();
URLClassLoader classLoader =
new URLClassLoader(new URL[] {url}, ClassLoader.getSystemClassLoader());
String inputClassName = inputClassPath.getFileName().toString().replace(".class", "");
Class<?> inputClass = classLoader.loadClass(inputClassName);
Map<String, CalledByIndy> callsiteMap = new HashMap<>();
for (Method m : inputClass.getDeclaredMethods()) {
CalledByIndy calledByIndy = m.getAnnotation(CalledByIndy.class);
if (calledByIndy == null) {
continue;
}
if (calledByIndy.fieldOrMethodName() == null) {
throw new Error("CallByIndy annotation does not specify a field or method name");
}
final int PRIVATE_STATIC = Modifier.STATIC | Modifier.PRIVATE;
if ((m.getModifiers() & PRIVATE_STATIC) != PRIVATE_STATIC) {
throw new Error(
"Method whose invocations should be replaced should be private and static");
}
callsiteMap.put(m.getName(), calledByIndy);
}
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
try (InputStream is = Files.newInputStream(inputClassPath)) {
ClassReader cr = new ClassReader(is);
cr.accept(new BootstrapBuilder(Opcodes.ASM9, cw, callsiteMap), 0);
}
try (OutputStream os = Files.newOutputStream(outputClassPath)) {
os.write(cw.toByteArray());
}
}
public static void main(String[] args) throws Throwable {
transform(Paths.get(args[0]), Paths.get(args[1]));
}
}
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