org.objectweb.asm.commons.StaticInitMerger.java Source code

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Here is the source code for org.objectweb.asm.commons.StaticInitMerger.java

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// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 3. Neither the name of the copyright holders nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
package org.objectweb.asm.commons;

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

/**
 * A {@link ClassVisitor} that merges <clinit> methods into a single one. All the existing
 * <clinit> methods are renamed, and a new one is created, which calls all the renamed
 * methods.
 *
 * @author Eric Bruneton
 */
public class StaticInitMerger extends ClassVisitor {

    /** The internal name of the visited class. */
    private String owner;

    /** The prefix to use to rename the existing <clinit> methods. */
    private final String renamedClinitMethodPrefix;

    /** The number of <clinit> methods visited so far. */
    private int numClinitMethods;

    /** The MethodVisitor for the merged <clinit> method. */
    private MethodVisitor mergedClinitVisitor;

    /**
     * Constructs a new {@link StaticInitMerger}. <i>Subclasses must not use this constructor</i>.
     * Instead, they must use the {@link #StaticInitMerger(int, String, ClassVisitor)} version.
     *
     * @param prefix the prefix to use to rename the existing &lt;clinit&gt; methods.
     * @param classVisitor the class visitor to which this visitor must delegate method calls. May be
     *     null.
     */
    public StaticInitMerger(final String prefix, final ClassVisitor classVisitor) {
        this(/* latest api = */ Opcodes.ASM7, prefix, classVisitor);
    }

    /**
     * Constructs a new {@link StaticInitMerger}.
     *
     * @param api the ASM API version implemented by this visitor. Must be one of {@link
     *     Opcodes#ASM4}, {@link Opcodes#ASM5} or {@link Opcodes#ASM6}.
     * @param prefix the prefix to use to rename the existing &lt;clinit&gt; methods.
     * @param classVisitor the class visitor to which this visitor must delegate method calls. May be
     *     null.
     */
    protected StaticInitMerger(final int api, final String prefix, final ClassVisitor classVisitor) {
        super(api, classVisitor);
        this.renamedClinitMethodPrefix = prefix;
    }

    @Override
    public void visit(final int version, final int access, final String name, final String signature,
            final String superName, final String[] interfaces) {
        super.visit(version, access, name, signature, superName, interfaces);
        this.owner = name;
    }

    @Override
    public MethodVisitor visitMethod(final int access, final String name, final String descriptor,
            final String signature, final String[] exceptions) {
        MethodVisitor methodVisitor;
        if ("<clinit>".equals(name)) {
            int newAccess = Opcodes.ACC_PRIVATE + Opcodes.ACC_STATIC;
            String newName = renamedClinitMethodPrefix + numClinitMethods++;
            methodVisitor = super.visitMethod(newAccess, newName, descriptor, signature, exceptions);

            if (mergedClinitVisitor == null) {
                mergedClinitVisitor = super.visitMethod(newAccess, name, descriptor, null, null);
            }
            mergedClinitVisitor.visitMethodInsn(Opcodes.INVOKESTATIC, owner, newName, descriptor, false);
        } else {
            methodVisitor = super.visitMethod(access, name, descriptor, signature, exceptions);
        }
        return methodVisitor;
    }

    @Override
    public void visitEnd() {
        if (mergedClinitVisitor != null) {
            mergedClinitVisitor.visitInsn(Opcodes.RETURN);
            mergedClinitVisitor.visitMaxs(0, 0);
        }
        super.visitEnd();
    }
}