ASM: a very small and fast Java bytecode manipulation framework
Copyright (c) 2000-2011 INRIA, France Telecom
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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;

A constant pool item. Constant pool items can be created with the 'newXXX' methods in the ClassWriter class. 
Author:
Eric Bruneton/**
 * A constant pool item. Constant pool items can be created with the 'newXXX'
 * methods in the {@link ClassWriter} class.
 * 
 * @author Eric Bruneton
 */
final class Item {

    
Index of this item in the constant pool.
/**
     * Index of this item in the constant pool.
     */
    int index;

    
Type of this constant pool item. A single class is used to represent all constant pool item types, in order to minimize the bytecode size of this package. The value of this field is one of ClassWriter.INT, ClassWriter.LONG, ClassWriter.FLOAT, ClassWriter.DOUBLE, ClassWriter.UTF8, ClassWriter.STR, ClassWriter.CLASS, ClassWriter.NAME_TYPE, ClassWriter.FIELD, ClassWriter.METH, ClassWriter.IMETH, ClassWriter.MTYPE, ClassWriter.INDY. MethodHandle constant 9 variations are stored using a range of 9 values from ClassWriter.HANDLE_BASE + 1 to ClassWriter.HANDLE_BASE + 9. Special Item types are used for Items that are stored in the ClassWriter ClassWriter.typeTable, instead of the constant pool, in order to avoid clashes with normal constant pool items in the ClassWriter constant pool's hash table. These special item types are ClassWriter.TYPE_NORMAL, ClassWriter.TYPE_UNINIT and ClassWriter.TYPE_MERGED. /**
     * Type of this constant pool item. A single class is used to represent all
     * constant pool item types, in order to minimize the bytecode size of this
     * package. The value of this field is one of {@link ClassWriter#INT},
     * {@link ClassWriter#LONG}, {@link ClassWriter#FLOAT},
     * {@link ClassWriter#DOUBLE}, {@link ClassWriter#UTF8},
     * {@link ClassWriter#STR}, {@link ClassWriter#CLASS},
     * {@link ClassWriter#NAME_TYPE}, {@link ClassWriter#FIELD},
     * {@link ClassWriter#METH}, {@link ClassWriter#IMETH},
     * {@link ClassWriter#MTYPE}, {@link ClassWriter#INDY}.
     * 
     * MethodHandle constant 9 variations are stored using a range of 9 values
     * from {@link ClassWriter#HANDLE_BASE} + 1 to
     * {@link ClassWriter#HANDLE_BASE} + 9.
     * 
     * Special Item types are used for Items that are stored in the ClassWriter
     * {@link ClassWriter#typeTable}, instead of the constant pool, in order to
     * avoid clashes with normal constant pool items in the ClassWriter constant
     * pool's hash table. These special item types are
     * {@link ClassWriter#TYPE_NORMAL}, {@link ClassWriter#TYPE_UNINIT} and
     * {@link ClassWriter#TYPE_MERGED}.
     */
    int type;

    
Value of this item, for an integer item.
/**
     * Value of this item, for an integer item.
     */
    int intVal;

    
Value of this item, for a long item.
/**
     * Value of this item, for a long item.
     */
    long longVal;

    
First part of the value of this item, for items that do not hold a
primitive value.
/**
     * First part of the value of this item, for items that do not hold a
     * primitive value.
     */
    String strVal1;

    
Second part of the value of this item, for items that do not hold a
primitive value.
/**
     * Second part of the value of this item, for items that do not hold a
     * primitive value.
     */
    String strVal2;

    
Third part of the value of this item, for items that do not hold a
primitive value.
/**
     * Third part of the value of this item, for items that do not hold a
     * primitive value.
     */
    String strVal3;

    
The hash code value of this constant pool item.
/**
     * The hash code value of this constant pool item.
     */
    int hashCode;

    
Link to another constant pool item, used for collision lists in the
constant pool's hash table.
/**
     * Link to another constant pool item, used for collision lists in the
     * constant pool's hash table.
     */
    Item next;

    
Constructs an uninitialized Item. /**
     * Constructs an uninitialized {@link Item}.
     */
    Item() {
    }

    
Constructs an uninitialized Item for constant pool element at given position. 
Params:
index – 
           index of the item to be constructed./**
     * Constructs an uninitialized {@link Item} for constant pool element at
     * given position.
     * 
     * @param index
     *            index of the item to be constructed.
     */
    Item(final int index) {
        this.index = index;
    }

    
Constructs a copy of the given item.
Params:
index – 
           index of the item to be constructed.
i – 
           the item that must be copied into the item to be constructed./**
     * Constructs a copy of the given item.
     * 
     * @param index
     *            index of the item to be constructed.
     * @param i
     *            the item that must be copied into the item to be constructed.
     */
    Item(final int index, final Item i) {
        this.index = index;
        type = i.type;
        intVal = i.intVal;
        longVal = i.longVal;
        strVal1 = i.strVal1;
        strVal2 = i.strVal2;
        strVal3 = i.strVal3;
        hashCode = i.hashCode;
    }

    
Sets this item to an integer item.
Params:
intVal – 
           the value of this item./**
     * Sets this item to an integer item.
     * 
     * @param intVal
     *            the value of this item.
     */
    void set(final int intVal) {
        this.type = ClassWriter.INT;
        this.intVal = intVal;
        this.hashCode = 0x7FFFFFFF & (type + intVal);
    }

    
Sets this item to a long item.
Params:
longVal – 
           the value of this item./**
     * Sets this item to a long item.
     * 
     * @param longVal
     *            the value of this item.
     */
    void set(final long longVal) {
        this.type = ClassWriter.LONG;
        this.longVal = longVal;
        this.hashCode = 0x7FFFFFFF & (type + (int) longVal);
    }

    
Sets this item to a float item.
Params:
floatVal – 
           the value of this item./**
     * Sets this item to a float item.
     * 
     * @param floatVal
     *            the value of this item.
     */
    void set(final float floatVal) {
        this.type = ClassWriter.FLOAT;
        this.intVal = Float.floatToRawIntBits(floatVal);
        this.hashCode = 0x7FFFFFFF & (type + (int) floatVal);
    }

    
Sets this item to a double item.
Params:
doubleVal – 
           the value of this item./**
     * Sets this item to a double item.
     * 
     * @param doubleVal
     *            the value of this item.
     */
    void set(final double doubleVal) {
        this.type = ClassWriter.DOUBLE;
        this.longVal = Double.doubleToRawLongBits(doubleVal);
        this.hashCode = 0x7FFFFFFF & (type + (int) doubleVal);
    }

    
Sets this item to an item that do not hold a primitive value.
Params:
type – 
           the type of this item.
strVal1 – 
           first part of the value of this item.
strVal2 – 
           second part of the value of this item.
strVal3 – 
           third part of the value of this item./**
     * Sets this item to an item that do not hold a primitive value.
     * 
     * @param type
     *            the type of this item.
     * @param strVal1
     *            first part of the value of this item.
     * @param strVal2
     *            second part of the value of this item.
     * @param strVal3
     *            third part of the value of this item.
     */
    @SuppressWarnings("fallthrough")
    void set(final int type, final String strVal1, final String strVal2,
            final String strVal3) {
        this.type = type;
        this.strVal1 = strVal1;
        this.strVal2 = strVal2;
        this.strVal3 = strVal3;
        switch (type) {
        case ClassWriter.CLASS:
            this.intVal = 0;     // intVal of a class must be zero, see visitInnerClass
        case ClassWriter.UTF8:
        case ClassWriter.STR:
        case ClassWriter.MTYPE:
        case ClassWriter.TYPE_NORMAL:
            hashCode = 0x7FFFFFFF & (type + strVal1.hashCode());
            return;
        case ClassWriter.NAME_TYPE: {
            hashCode = 0x7FFFFFFF & (type + strVal1.hashCode()
                    * strVal2.hashCode());
            return;
        }
        // ClassWriter.FIELD:
        // ClassWriter.METH:
        // ClassWriter.IMETH:
        // ClassWriter.HANDLE_BASE + 1..9
        default:
            hashCode = 0x7FFFFFFF & (type + strVal1.hashCode()
                    * strVal2.hashCode() * strVal3.hashCode());
        }
    }

    
Sets the item to an InvokeDynamic item.
Params:
name – 
           invokedynamic's name.
desc – 
           invokedynamic's desc.
bsmIndex – 
           zero based index into the class attribute BootrapMethods./**
     * Sets the item to an InvokeDynamic item.
     * 
     * @param name
     *            invokedynamic's name.
     * @param desc
     *            invokedynamic's desc.
     * @param bsmIndex
     *            zero based index into the class attribute BootrapMethods.
     */
    void set(String name, String desc, int bsmIndex) {
        this.type = ClassWriter.INDY;
        this.longVal = bsmIndex;
        this.strVal1 = name;
        this.strVal2 = desc;
        this.hashCode = 0x7FFFFFFF & (ClassWriter.INDY + bsmIndex
                * strVal1.hashCode() * strVal2.hashCode());
    }

    
Sets the item to a BootstrapMethod item.
Params:
position – 
           position in byte in the class attribute BootrapMethods.
hashCode – 
           hashcode of the item. This hashcode is processed from the
           hashcode of the bootstrap method and the hashcode of all
           bootstrap arguments./**
     * Sets the item to a BootstrapMethod item.
     * 
     * @param position
     *            position in byte in the class attribute BootrapMethods.
     * @param hashCode
     *            hashcode of the item. This hashcode is processed from the
     *            hashcode of the bootstrap method and the hashcode of all
     *            bootstrap arguments.
     */
    void set(int position, int hashCode) {
        this.type = ClassWriter.BSM;
        this.intVal = position;
        this.hashCode = hashCode;
    }

    
Indicates if the given item is equal to this one. This method assumes that the two items have the same type.
Params:
i –  the item to be compared to this one. Both items must have the same type.
Returns:
true if the given item if equal to this one,
        false otherwise./**
     * Indicates if the given item is equal to this one. <i>This method assumes
     * that the two items have the same {@link #type}</i>.
     * 
     * @param i
     *            the item to be compared to this one. Both items must have the
     *            same {@link #type}.
     * @return <tt>true</tt> if the given item if equal to this one,
     *         <tt>false</tt> otherwise.
     */
    boolean isEqualTo(final Item i) {
        switch (type) {
        case ClassWriter.UTF8:
        case ClassWriter.STR:
        case ClassWriter.CLASS:
        case ClassWriter.MTYPE:
        case ClassWriter.TYPE_NORMAL:
            return i.strVal1.equals(strVal1);
        case ClassWriter.TYPE_MERGED:
        case ClassWriter.LONG:
        case ClassWriter.DOUBLE:
            return i.longVal == longVal;
        case ClassWriter.INT:
        case ClassWriter.FLOAT:
            return i.intVal == intVal;
        case ClassWriter.TYPE_UNINIT:
            return i.intVal == intVal && i.strVal1.equals(strVal1);
        case ClassWriter.NAME_TYPE:
            return i.strVal1.equals(strVal1) && i.strVal2.equals(strVal2);
        case ClassWriter.INDY: {
            return i.longVal == longVal && i.strVal1.equals(strVal1)
                    && i.strVal2.equals(strVal2);
        }
        // case ClassWriter.FIELD:
        // case ClassWriter.METH:
        // case ClassWriter.IMETH:
        // case ClassWriter.HANDLE_BASE + 1..9
        default:
            return i.strVal1.equals(strVal1) && i.strVal2.equals(strVal2)
                    && i.strVal3.equals(strVal3);
        }
    }

}