/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2007 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 alterrs.asm;

/**
 * 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.
	 */
	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 {@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}.
	 * <p/>
	 * 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.
	 */
	int intVal;

	/**
	 * 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.
	 */
	String strVal1;

	/**
	 * 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.
	 */
	String strVal3;

	/**
	 * 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.
	 */
	Item next;

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

	/**
	 * 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.
	 * 
	 * @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.
	 * 
	 * @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.
	 * 
	 * @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.
	 * 
	 * @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.
	 * 
	 * @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.
	 * 
	 * @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.
	 */
	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.UTF8:
		case ClassWriter.STR:
		case ClassWriter.CLASS:
		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:
		default:
			hashCode = 0x7FFFFFFF & (type + strVal1.hashCode()
					* strVal2.hashCode() * strVal3.hashCode());
		}
	}

	/**
	 * 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.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.FIELD:
			// case ClassWriter.METH:
			// case ClassWriter.IMETH:
		default:
			return i.strVal1.equals(strVal1) && i.strVal2.equals(strVal2)
					&& i.strVal3.equals(strVal3);
		}
	}
}
