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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"
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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package org.mvel2.asm;

/**
 * A visitor to visit a Java field. The methods of this class must be called in the following order:
 * ( {@code visitAnnotation} | {@code visitTypeAnnotation} | {@code visitAttribute} )* {@code
 * visitEnd}.
 *
 * @author Eric Bruneton
 */
public abstract class FieldVisitor {

    /**
     * The ASM API version implemented by this visitor. The value of this field must be one of {@link
     * Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
     */
    protected final int api;

    /** The field visitor to which this visitor must delegate method calls. May be null. */
    protected FieldVisitor fv;

    /**
     * Constructs a new {@link FieldVisitor}.
     *
     * @param api the ASM API version implemented by this visitor. Must be one of {@link
     *     Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
     */
    public FieldVisitor(final int api) {
        this(api, null);
    }

    /**
     * Constructs a new {@link FieldVisitor}.
     *
     * @param api the ASM API version implemented by this visitor. Must be one of {@link
     *     Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6} or {@link Opcodes#ASM7}.
     * @param fieldVisitor the field visitor to which this visitor must delegate method calls. May be
     *     null.
     */
    public FieldVisitor(final int api, final FieldVisitor fieldVisitor) {
        if (api != Opcodes.ASM6 && api != Opcodes.ASM5 && api != Opcodes.ASM4 && api != Opcodes.ASM7) {
            throw new IllegalArgumentException();
        }
        this.api = api;
        this.fv = fieldVisitor;
    }

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

    /**
     * Visits an annotation on the type of the field.
     *
     * @param typeRef a reference to the annotated type. The sort of this type reference must be
     *     {@link TypeReference#FIELD}. 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 {@literal null} if the annotation targets
     *     'typeRef' as a whole.
     * @param descriptor the class descriptor of the annotation class.
     * @param visible {@literal true} if the annotation is visible at runtime.
     * @return a visitor to visit the annotation values, or {@literal null} if this visitor is not
     *     interested in visiting this annotation.
     */
    public AnnotationVisitor visitTypeAnnotation(final int typeRef, final TypePath typePath, final String descriptor,
            final boolean visible) {
        if (api < Opcodes.ASM5) {
            throw new UnsupportedOperationException("This feature requires ASM5");
        }
        if (fv != null) {
            return fv.visitTypeAnnotation(typeRef, typePath, descriptor, visible);
        }
        return null;
    }

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

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