/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdi.internal.jdwp;


import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.eclipse.jdi.internal.VirtualMachineImpl;


/**
 * From this class all Java Debug Wire Protocol (JDWP) IDs 
 * declared by the JDWP specification are derived.
 *
 */
public abstract class JdwpID {
	/** Tag Constants. */
	public static final byte NULL_TAG = 91;			// Used for tagged null values.	
	public static final byte ARRAY_TAG = 91;			// '[' - an array object (objectID size).	
	public static final byte BYTE_TAG = 66;				// 'B' - a byte value (1 byte).	
	public static final byte CHAR_TAG = 67;				// 'C' - a character value (2 bytes).	
	public static final byte OBJECT_TAG = 76;			// 'L' - an object (objectID size).	
	public static final byte FLOAT_TAG = 70;			// 'F' - a float value (4 bytes).	
	public static final byte DOUBLE_TAG = 68;			// 'D' - a double value (8 bytes).	
	public static final byte INT_TAG = 73;				// 'I' - an int value (4 bytes).	
	public static final byte LONG_TAG = 74;				// 'J' - a long value (8 bytes).	
	public static final byte SHORT_TAG = 83;			// 'S' - a short value (2 bytes).	
	public static final byte VOID_TAG = 86;				// 'V' - a void value (no bytes).	
	public static final byte BOOLEAN_TAG = 90;			// 'Z' - a boolean value (1 byte).	
	public static final byte STRING_TAG = 115;			// 's' - a String object (objectID size).	
	public static final byte THREAD_TAG = 116;			// 't' - a Thread object (objectID size).	
	public static final byte THREAD_GROUP_TAG = 103;	// 'g' - a ThreadGroup object (objectID size).	
	public static final byte CLASS_LOADER_TAG = 108;	// 'l' - a ClassLoader object (objectID size).	
	public static final byte CLASS_OBJECT_TAG = 99;		// 'c' - a class object object (objectID size).	
	
	/** TypeTag Constants. */
	public static final byte TYPE_TAG_CLASS = 1;		// ReferenceType is a class.	
	public static final byte TYPE_TAG_INTERFACE = 2;	// ReferenceType is an interface.	
	public static final byte TYPE_TAG_ARRAY = 3;		// ReferenceType is an array.	

	/** Mapping of command codes to strings. */
	private static HashMap fTagMap = null;
	private static HashMap fTypeTagMap = null;

	/** Jdwp representation of null ID. */
	protected static final int VALUE_NULL = 0;

	/** The value of the ID */
	protected long fValue = VALUE_NULL;
	/** The virtual machine of the mirror object that uses this ID (needed for ID sizes. */
	protected VirtualMachineImpl fVirtualMachine;
	
	/**
	 * Creates new JdwpID.
	 */
	public JdwpID(VirtualMachineImpl vmImpl) {
		fVirtualMachine = vmImpl;
	}
	
	/**
	 * @return Returns true if two IDs refer to the same entity in the target VM.
	 * @see java.lang.Object#equals(Object)
	 */
	public boolean equals(Object object) {
		return object instanceof JdwpID && fValue == ((JdwpID)object).fValue;
	}
	
	/**
	 * @return Returns a has code for this object.
	 * @see java.lang.Object#hashCode
	 */
	public int hashCode() {
		return (int)fValue;
 	}
 	
	/**
	 * @return Returns value of ID.
	 */
	public final long value() {
		return fValue;
 	}
	
	/**
	 * @return Returns string representation.
	 */
	public String toString() {
		return new Long(fValue).toString();
	}

	/**
	 * @return Returns VM specific size of ID.
	 */
	protected abstract int getSize();

	/**
	 * @return Returns true if ID is null.
	 */
	public abstract boolean isNull();
	
	/**
	 * Reads ID.
	 */
	public void read(DataInputStream inStream) throws IOException {
		fValue = 0;
		int size = getSize();
		for (int i = 0; i < size; i++) {
			int b = inStream.readUnsignedByte();	// Note that the byte must be treated as unsigned.
			fValue = fValue << 8 | b;
		}
	}

	/**
	 * Writes ID.
	 */
	public void write(DataOutputStream outStream) throws IOException {
		int size = getSize();
		for (int i = size - 1; i >= 0; i--) {
			byte b = (byte)(fValue >>> 8 * i);	// Note that >>> must be used because fValue must be treated as unsigned.
			outStream.write(b);
		}
	}
	
	/**
	 * Retrieves constant mappings.
	 */
	public static void getConstantMaps() {
		if (fTagMap != null)
			return;
		
		java.lang.reflect.Field[] fields = JdwpID.class.getDeclaredFields();
		fTagMap = new HashMap();
		fTypeTagMap = new HashMap();
		for (int i = 0; i < fields.length; i++) {
			java.lang.reflect.Field field = fields[i];
			if ((field.getModifiers() & java.lang.reflect.Modifier.PUBLIC) == 0 || (field.getModifiers() & java.lang.reflect.Modifier.STATIC) == 0 || (field.getModifiers() & java.lang.reflect.Modifier.FINAL) == 0)
				continue;
				
			try {
				String name = field.getName();
				Integer intValue = new Integer(field.getInt(null));
				if (name.startsWith("TYPE_TAG_")) { //$NON-NLS-1$
					name = name.substring(9);
					fTypeTagMap.put(intValue, name);
				} else if (name.endsWith("_TAG")) { //$NON-NLS-1$
					fTagMap.put(intValue, name);
				}
			} catch (IllegalAccessException e) {
				// Will not occur for own class.
			} catch (IllegalArgumentException e) {
				// Should not occur.
				// We should take care that all public static final constants
				// in this class are numbers that are convertible to int.
			}
		}
	}
	
	/**
	 * @return Returns a map with string representations of tags.
	 */
	 public static Map tagMap() {
	 	getConstantMaps();
	 	return fTagMap;
	 }

	/**
	 * @return Returns a map with string representations of type tags.
	 */
	 public static Map typeTagMap() {
	 	getConstantMaps();
	 	return fTypeTagMap;
	 }
}