com.google.gwt.dev.shell.rewrite.RewriteRefsToJsoClasses.java Source code

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Here is the source code for com.google.gwt.dev.shell.rewrite.RewriteRefsToJsoClasses.java

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/*
 * Copyright 2008 Google Inc.
 *
 * 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 com.google.gwt.dev.shell.rewrite;

import com.google.gwt.dev.shell.rewrite.HostedModeClassRewriter.InstanceMethodOracle;

import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.commons.Remapper;

import java.util.Set;

/**
 * Rewrites references to modified JSO subtypes.
 *
 * <ol>
 * <li>Changes the owner type for instructions that reference items in a JSO
 * class to the implementation class.</li>
 * <li>Rewrites instance calls to JSO classes into static calls.</li>
 * <li>Updates the descriptor for such call sites to includes a synthetic
 * <code>this</code> parameter. This modified method has same stack behavior
 * as the original instance method.</li>
 * </ol>
 */
class RewriteRefsToJsoClasses extends ClassVisitor {

    /**
     * A method body rewriter to actually rewrite call sites.
     */
    private class MyMethodAdapter extends MethodVisitor {

        private Remapper remapper = new Remapper() {
            @Override
            public String map(String typeName) {
                if (jsoDescriptors.contains(typeName)) {
                    return HostedModeClassRewriter.JAVASCRIPTOBJECT_IMPL_DESC;
                }
                return typeName;
            }
        };

        public MyMethodAdapter(MethodVisitor mv) {
            super(Opcodes.ASM6, mv);
        }

        @Override
        public void visitFieldInsn(int opcode, String owner, String name, String desc) {
            if (jsoDescriptors.contains(owner)) {
                // Change the owner to the rewritten class.
                owner += "$";
            }
            super.visitFieldInsn(opcode, owner, name, desc);
        }

        @Override
        public void visitLdcInsn(Object cst) {
            cst = remapper.mapValue(cst);
            super.visitLdcInsn(cst);
        }

        @Override
        public void visitMethodInsn(int opcode, String owner, String name, String desc, boolean dintf) {
            if (jsoDescriptors.contains(owner)) {
                // Find the class that actually declared the method.
                if (opcode == Opcodes.INVOKEVIRTUAL) {
                    owner = mapper.findOriginalDeclaringClass(owner, name + desc);
                }
                if (!owner.equals("java/lang/Object")) {
                    if (opcode == Opcodes.INVOKEVIRTUAL || opcode == Opcodes.INVOKESPECIAL) {
                        // Instance/super call to JSO; rewrite as static.
                        opcode = Opcodes.INVOKESTATIC;
                        desc = HostedModeClassRewriter.addSyntheticThisParam(owner, desc);
                        name += "$";
                    }
                    // Change the owner to implementation class.
                    owner += "$";
                }
            }
            super.visitMethodInsn(opcode, owner, name, desc, dintf);
        }

        @Override
        public void visitMultiANewArrayInsn(String desc, int dims) {
            desc = remapper.mapType(desc);
            super.visitMultiANewArrayInsn(desc, dims);
        }

        @Override
        public void visitTypeInsn(int opcode, String type) {
            if (opcode == Opcodes.ANEWARRAY) {
                type = remapper.mapType(type);
            }
            super.visitTypeInsn(opcode, type);
        }
    }

    /**
     * An unmodifiable set of descriptors containing <code>JavaScriptObject</code>
     * and all subclasses.
     */
    protected final Set<String> jsoDescriptors;

    /**
     * Maps methods to the class in which they are declared.
     */
    private InstanceMethodOracle mapper;

    /**
     * Construct a new rewriter instance.
     *
     * @param cv the visitor to chain to
     * @param jsoDescriptors an unmodifiable set of descriptors containing
     *          <code>JavaScriptObject</code> and all subclasses
     * @param mapper maps methods to the class in which they are declared
     */
    public RewriteRefsToJsoClasses(ClassVisitor cv, Set<String> jsoDescriptors, InstanceMethodOracle mapper) {
        super(Opcodes.ASM6, cv);
        this.jsoDescriptors = jsoDescriptors;
        this.mapper = mapper;
    }

    @Override
    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
        // Wrap the returned method visitor in my own.
        MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions);
        return new MyMethodAdapter(mv);
    }

}