src/share/classes/com/sun/tools/javac/code/TargetType.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package com.sun.tools.javac.code;

import com.sun.tools.javac.util.Assert;

/**
 * Describes the type of program element an extended annotation (or extended
 * compound attribute) targets.
 *
 * By comparison, a Tree.Kind has enum values for all elements in the AST, and
 * it does not provide enough resolution for type arguments (i.e., whether an
 * annotation targets a type argument in a local variable, method return type,
 * or a typecast).
 *
 *  <p><b>This is NOT part of any supported API.
 *  If you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
// Code duplicated in com.sun.tools.classfile.TypeAnnotation.TargetType
public enum TargetType {
    /** For annotations on a class type parameter declaration. */
    CLASS_TYPE_PARAMETER(0x00),

    /** For annotations on a method type parameter declaration. */
    METHOD_TYPE_PARAMETER(0x01),

    /** For annotations on the type of an "extends" or "implements" clause. */
    CLASS_EXTENDS(0x10),

    /** For annotations on a bound of a type parameter of a class. */
    CLASS_TYPE_PARAMETER_BOUND(0x11),

    /** For annotations on a bound of a type parameter of a method. */
    METHOD_TYPE_PARAMETER_BOUND(0x12),

    /** For annotations on a field. */
    FIELD(0x13),

    /** For annotations on a method return type. */
    METHOD_RETURN(0x14),

    /** For annotations on the method receiver. */
    METHOD_RECEIVER(0x15),

    /** For annotations on a method parameter. */
    METHOD_FORMAL_PARAMETER(0x16),

    /** For annotations on a throws clause in a method declaration. */
    THROWS(0x17),

    /** For annotations on a local variable. */
    LOCAL_VARIABLE(0x40, true),

    /** For annotations on a resource variable. */
    RESOURCE_VARIABLE(0x41, true),

    /** For annotations on an exception parameter. */
    EXCEPTION_PARAMETER(0x42, true),

    /** For annotations on a type test. */
    INSTANCEOF(0x43, true),

    /** For annotations on an object creation expression. */
    NEW(0x44, true),

    /** For annotations on a constructor reference receiver. */
    CONSTRUCTOR_REFERENCE(0x45, true),

    /** For annotations on a method reference receiver. */
    METHOD_REFERENCE(0x46, true),

    /** For annotations on a typecast. */
    CAST(0x47, true),

    /** For annotations on a type argument of an object creation expression. */
    CONSTRUCTOR_INVOCATION_TYPE_ARGUMENT(0x48, true),

    /** For annotations on a type argument of a method call. */
    METHOD_INVOCATION_TYPE_ARGUMENT(0x49, true),

    /** For annotations on a type argument of a constructor reference. */
    CONSTRUCTOR_REFERENCE_TYPE_ARGUMENT(0x4A, true),

    /** For annotations on a type argument of a method reference. */
    METHOD_REFERENCE_TYPE_ARGUMENT(0x4B, true),

    /** For annotations with an unknown target. */
    UNKNOWN(0xFF);

    private static final int MAXIMUM_TARGET_TYPE_VALUE = 0x4B;

    private final int targetTypeValue;
    private final boolean isLocal;

    private TargetType(int targetTypeValue) {
        this(targetTypeValue, false);
    }

    private TargetType(int targetTypeValue, boolean isLocal) {
        if (targetTypeValue < 0
                || targetTypeValue > 255)
                Assert.error("Attribute type value needs to be an unsigned byte: " + String.format("0x%02X", targetTypeValue));
        this.targetTypeValue = targetTypeValue;
        this.isLocal = isLocal;
    }

    /**
     * Returns whether or not this TargetType represents an annotation whose
     * target is exclusively a tree in a method body
     *
     * Note: wildcard bound targets could target a local tree and a class
     * member declaration signature tree
     */
    public boolean isLocal() {
        return isLocal;
    }

    public int targetTypeValue() {
        return this.targetTypeValue;
    }

    private static final TargetType[] targets;

    static {
        targets = new TargetType[MAXIMUM_TARGET_TYPE_VALUE + 1];
        TargetType[] alltargets = values();
        for (TargetType target : alltargets) {
            if (target.targetTypeValue != UNKNOWN.targetTypeValue)
                targets[target.targetTypeValue] = target;
        }
        for (int i = 0; i <= MAXIMUM_TARGET_TYPE_VALUE; ++i) {
            if (targets[i] == null)
                targets[i] = UNKNOWN;
        }
    }

    public static boolean isValidTargetTypeValue(int tag) {
        if (tag == UNKNOWN.targetTypeValue)
            return true;

        return (tag >= 0 && tag < targets.length);
    }

    public static TargetType fromTargetTypeValue(int tag) {
        if (tag == UNKNOWN.targetTypeValue)
            return UNKNOWN;

        if (tag < 0 || tag >= targets.length)
            Assert.error("Unknown TargetType: " + tag);
        return targets[tag];
    }
}