ClassVisitor.java

/***
 * 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;

/**
 * A visitor to visit a Java class. The methods of this class must be called in
 * the following order: <tt>visit</tt> [ <tt>visitSource</tt> ] [
 * <tt>visitOuterClass</tt> ] ( <tt>visitAnnotation</tt> |
 * <tt>visitTypeAnnotation</tt> | <tt>visitAttribute</tt> )* (
 * <tt>visitInnerClass</tt> | <tt>visitField</tt> | <tt>visitMethod</tt> )*
 * <tt>visitEnd</tt>.
 * 
 * @author Eric Bruneton
 */
public abstract class ClassVisitor {

    /**
     * The ASM API version implemented by this visitor. The value of this field
     * must be one of {@link Opcodes#ASM4} or {@link Opcodes#ASM5}.
     */
    protected final int api;

    /**
     * The class visitor to which this visitor must delegate method calls. May
     * be null.
     */
    protected ClassVisitor cv;

    /**
     * Constructs a new {@link ClassVisitor}.
     * 
     * @param api
     *            the ASM API version implemented by this visitor. Must be one
     *            of {@link Opcodes#ASM4} or {@link Opcodes#ASM5}.
     */
    public ClassVisitor(final int api) {
        this(api, null);
    }

    /**
     * Constructs a new {@link ClassVisitor}.
     * 
     * @param api
     *            the ASM API version implemented by this visitor. Must be one
     *            of {@link Opcodes#ASM4} or {@link Opcodes#ASM5}.
     * @param cv
     *            the class visitor to which this visitor must delegate method
     *            calls. May be null.
     */
    public ClassVisitor(final int api, final ClassVisitor cv) {
        if (api != Opcodes.ASM4 && api != Opcodes.ASM5) {
            throw new IllegalArgumentException();
        }
        this.api = api;
        this.cv = cv;
    }

    /**
     * Visits the header of the class.
     * 
     * @param version
     *            the class version.
     * @param access
     *            the class's access flags (see {@link Opcodes}). This parameter
     *            also indicates if the class is deprecated.
     * @param name
     *            the internal name of the class (see
     *            {@link Type#getInternalName() getInternalName}).
     * @param signature
     *            the signature of this class. May be <tt>null</tt> if the class
     *            is not a generic one, and does not extend or implement generic
     *            classes or interfaces.
     * @param superName
     *            the internal of name of the super class (see
     *            {@link Type#getInternalName() getInternalName}). For
     *            interfaces, the super class is {@link Object}. May be
     *            <tt>null</tt>, but only for the {@link Object} class.
     * @param interfaces
     *            the internal names of the class's interfaces (see
     *            {@link Type#getInternalName() getInternalName}). May be
     *            <tt>null</tt>.
     */
    public void visit(int version, int access, String name, String signature,
            String superName, String[] interfaces) {
        if (cv != null) {
            cv.visit(version, access, name, signature, superName, interfaces);
        }
    }

    /**
     * Visits the source of the class.
     * 
     * @param source
     *            the name of the source file from which the class was compiled.
     *            May be <tt>null</tt>.
     * @param debug
     *            additional debug information to compute the correspondance
     *            between source and compiled elements of the class. May be
     *            <tt>null</tt>.
     */
    public void visitSource(String source, String debug) {
        if (cv != null) {
            cv.visitSource(source, debug);
        }
    }

    /**
     * Visits the enclosing class of the class. This method must be called only
     * if the class has an enclosing class.
     * 
     * @param owner
     *            internal name of the enclosing class of the class.
     * @param name
     *            the name of the method that contains the class, or
     *            <tt>null</tt> if the class is not enclosed in a method of its
     *            enclosing class.
     * @param desc
     *            the descriptor of the method that contains the class, or
     *            <tt>null</tt> if the class is not enclosed in a method of its
     *            enclosing class.
     */
    public void visitOuterClass(String owner, String name, String desc) {
        if (cv != null) {
            cv.visitOuterClass(owner, name, desc);
        }
    }

    /**
     * Visits an annotation of the class.
     * 
     * @param desc
     *            the class descriptor of the annotation class.
     * @param visible
     *            <tt>true</tt> if the annotation is visible at runtime.
     * @return a visitor to visit the annotation values, or <tt>null</tt> if
     *         this visitor is not interested in visiting this annotation.
     */
    public AnnotationVisitor visitAnnotation(String desc, boolean visible) {
        if (cv != null) {
            return cv.visitAnnotation(desc, visible);
        }
        return null;
    }

    /**
     * Visits an annotation on a type in the class signature.
     * 
     * @param typeRef
     *            a reference to the annotated type. The sort of this type
     *            reference must be {@link TypeReference#CLASS_TYPE_PARAMETER
     *            CLASS_TYPE_PARAMETER},
     *            {@link TypeReference#CLASS_TYPE_PARAMETER_BOUND
     *            CLASS_TYPE_PARAMETER_BOUND} or
     *            {@link TypeReference#CLASS_EXTENDS CLASS_EXTENDS}. See
     *            {@link TypeReference}.
     * @param typePath
     *            the path to the annotated type argument, wildcard bound, array
     *            element type, or static inner type within 'typeRef'. May be
     *            <tt>null</tt> if the annotation targets 'typeRef' as a whole.
     * @param desc
     *            the class descriptor of the annotation class.
     * @param visible
     *            <tt>true</tt> if the annotation is visible at runtime.
     * @return a visitor to visit the annotation values, or <tt>null</tt> if
     *         this visitor is not interested in visiting this annotation.
     */
    public AnnotationVisitor visitTypeAnnotation(int typeRef,
            TypePath typePath, String desc, boolean visible) {
        if (api < Opcodes.ASM5) {
            throw new RuntimeException();
        }
        if (cv != null) {
            return cv.visitTypeAnnotation(typeRef, typePath, desc, visible);
        }
        return null;
    }

    /**
     * Visits a non standard attribute of the class.
     * 
     * @param attr
     *            an attribute.
     */
    public void visitAttribute(Attribute attr) {
        if (cv != null) {
            cv.visitAttribute(attr);
        }
    }

    /**
     * Visits information about an inner class. This inner class is not
     * necessarily a member of the class being visited.
     * 
     * @param name
     *            the internal name of an inner class (see
     *            {@link Type#getInternalName() getInternalName}).
     * @param outerName
     *            the internal name of the class to which the inner class
     *            belongs (see {@link Type#getInternalName() getInternalName}).
     *            May be <tt>null</tt> for not member classes.
     * @param innerName
     *            the (simple) name of the inner class inside its enclosing
     *            class. May be <tt>null</tt> for anonymous inner classes.
     * @param access
     *            the access flags of the inner class as originally declared in
     *            the enclosing class.
     */
    public void visitInnerClass(String name, String outerName,
            String innerName, int access) {
        if (cv != null) {
            cv.visitInnerClass(name, outerName, innerName, access);
        }
    }

    /**
     * Visits a field of the class.
     * 
     * @param access
     *            the field's access flags (see {@link Opcodes}). This parameter
     *            also indicates if the field is synthetic and/or deprecated.
     * @param name
     *            the field's name.
     * @param desc
     *            the field's descriptor (see {@link Type Type}).
     * @param signature
     *            the field's signature. May be <tt>null</tt> if the field's
     *            type does not use generic types.
     * @param value
     *            the field's initial value. This parameter, which may be
     *            <tt>null</tt> if the field does not have an initial value,
     *            must be an {@link Integer}, a {@link Float}, a {@link Long}, a
     *            {@link Double} or a {@link String} (for <tt>int</tt>,
     *            <tt>float</tt>, <tt>long</tt> or <tt>String</tt> fields
     *            respectively). <i>This parameter is only used for static
     *            fields</i>. Its value is ignored for non static fields, which
     *            must be initialized through bytecode instructions in
     *            constructors or methods.
     * @return a visitor to visit field annotations and attributes, or
     *         <tt>null</tt> if this class visitor is not interested in visiting
     *         these annotations and attributes.
     */
    public FieldVisitor visitField(int access, String name, String desc,
            String signature, Object value) {
        if (cv != null) {
            return cv.visitField(access, name, desc, signature, value);
        }
        return null;
    }

    /**
     * Visits a method of the class. This method <i>must</i> return a new
     * {@link MethodVisitor} instance (or <tt>null</tt>) each time it is called,
     * i.e., it should not return a previously returned visitor.
     * 
     * @param access
     *            the method's access flags (see {@link Opcodes}). This
     *            parameter also indicates if the method is synthetic and/or
     *            deprecated.
     * @param name
     *            the method's name.
     * @param desc
     *            the method's descriptor (see {@link Type Type}).
     * @param signature
     *            the method's signature. May be <tt>null</tt> if the method
     *            parameters, return type and exceptions do not use generic
     *            types.
     * @param exceptions
     *            the internal names of the method's exception classes (see
     *            {@link Type#getInternalName() getInternalName}). May be
     *            <tt>null</tt>.
     * @return an object to visit the byte code of the method, or <tt>null</tt>
     *         if this class visitor is not interested in visiting the code of
     *         this method.
     */
    public MethodVisitor visitMethod(int access, String name, String desc,
            String signature, String[] exceptions) {
        if (cv != null) {
            return cv.visitMethod(access, name, desc, signature, exceptions);
        }
        return null;
    }

    /**
     * Visits the end of the class. This method, which is the last one to be
     * called, is used to inform the visitor that all the fields and methods of
     * the class have been visited.
     */
    public void visitEnd() {
        if (cv != null) {
            cv.visitEnd();
        }
    }
}