com.google.code.jconts.instrument.util.IntroduceLocalsAdapter.java Source code

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Here is the source code for com.google.code.jconts.instrument.util.IntroduceLocalsAdapter.java

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/**
 * Copyright (C) 2011 Ivan Dubrov
 *
 * 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.code.jconts.instrument.util;

import org.objectweb.asm.Label;
import org.objectweb.asm.MethodAdapter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;

/**
 * Introduces local variables of given types at the beginning of the frame
 * (after "this" local for instance methods).
 * <p>
 * Since adding at arbitrary place requires extra bookkeeping, this class
 * supports introducing variables at the beginning only.
 */
public class IntroduceLocalsAdapter extends MethodAdapter {
    private final int shift;
    private final Object[] extraLocals;
    private final boolean isStatic;

    public IntroduceLocalsAdapter(MethodVisitor mv, boolean isStatic, Type... locals) {
        super(mv);

        this.isStatic = isStatic;

        // double & long could take two.
        int shift = 0;
        for (Type t : locals) {
            shift += t.getSize();
        }
        this.shift = shift;
        this.extraLocals = new Object[locals.length];
        for (int i = 0; i < locals.length; ++i) {
            extraLocals[i] = Frames.toFrameType(locals[i]);
        }
    }

    @Override
    public void visitVarInsn(int opcode, int var) {
        // Shift all indexes after "this"
        if (isStatic || var > 0) {
            var += shift;
        }
        super.visitVarInsn(opcode, var);
    }

    @Override
    public void visitIincInsn(int var, int increment) {
        // Shift all indexes after "this"
        if (isStatic || var > 0) {
            var += shift;
        }
        super.visitIincInsn(var, increment);
    }

    @Override
    public void visitFrame(int type, int nLocal, Object[] local, int nStack, Object[] stack) {
        if (type == Opcodes.F_FULL) {
            // FIXME:.... utils...
            Object[] newLocal = new Object[local.length + extraLocals.length];

            int off = 0;
            if (!isStatic) {
                newLocal[0] = local[0];
                off = 1;
            }
            System.arraycopy(extraLocals, 0, newLocal, off, extraLocals.length);
            System.arraycopy(local, off, newLocal, extraLocals.length + off, local.length - off);

            super.visitFrame(Opcodes.F_FULL, newLocal.length, newLocal, nStack, stack);
        } else {
            super.visitFrame(type, nLocal, local, nStack, stack);
        }
    }

    @Override
    public void visitLocalVariable(String name, String desc, String signature, Label start, Label end, int index) {
        // Shift all indexes after "this"
        if (isStatic || index > 0) {
            index += shift;
        }
        super.visitLocalVariable(name, desc, signature, start, end, index);
    }

    @Override
    public void visitMaxs(int maxStack, int maxLocals) {
        super.visitMaxs(maxStack, maxLocals + extraLocals.length);
    }
}