package com.de22.javabytecode;

import com.de22.javabytecode.attribute.*;
import com.de22.javabytecode.constant.*;

/**
 * Copyright Wynne Crisman 1999,2006<p>
 * Defines an attribute in any of the attribute collections.
 * See the JVM specification 4.7.
 * Subclasses of this type will provided additional functionality.
 */
public abstract class CodeAttribute extends Component {
	/** The index of the attribute's name in the constant collection. */
	private short nameIndex = -1;
/**
 * CodeAttribute constructor.
 */
public CodeAttribute(Type type) {
	super(type);
}//CodeAttribute()//
/**
 * Gets the attribute's default name as it is stored in the class bytes.
 * @return The default name identifying the attribute's type.
 */
public abstract String getDefaultName();
/**
 * Gets the index of the attribute's name in the type's constant pool.
 * @return The index of the attribute name.
 */
public short getNameIndex() {
	return nameIndex;
}//getNameIndex()//
/* (non-Javadoc)
 * @see com.de22.javabytecode.ITypeComponent#getSize()
 */
public abstract int getSize();
/**
 * Reads an attribute from the given stream.
 * @param type The type object that the attribute will belong to.
 * @param in The input stream to read the attribute from.
 */
protected static CodeAttribute readAttribute(Type type, java.io.ObjectInput in) throws java.io.IOException, ClassNotFoundException {
	CodeAttribute attribute = null;
	short nameIndex = in.readShort();
	Constant constant = type.getConstant(nameIndex);
	ConstantUtf8 constantUtf8 = constant instanceof ConstantUtf8 ? (ConstantUtf8) constant : constant instanceof ConstantString ? (ConstantUtf8) type.getConstant(((ConstantString) constant).getStringIndex()) : null;
	
	//This should never occur, but seems to for some compiled java code (probably due to a bad compiler).  We will simply replace the missing string with an empty string.//
	if(constantUtf8 == null) {
//		System.out.println("Null constant found (index = " + nameIndex + ") while reading an unidentified attribute.");
		attribute = new Unidentified(type, "");
		attribute.nameIndex = nameIndex;
		attribute.readExternal(in);
	}//if//
	else {
		String name = constantUtf8.getValue();
		
		if(name.equalsIgnoreCase("SourceFile")) {
			attribute = new SourceFile(type);
		}//if//
		else if(name.equalsIgnoreCase("Code")) {
			attribute = new Code(type);
		}//else if//
		else if(name.equalsIgnoreCase("Exceptions")) {
			attribute = new ExceptionIndexes(type);
		}//else if//
		else if(name.equalsIgnoreCase("LineNumberTable")) {
			attribute = new LineNumberTable(type);
		}//else if//
		else if(name.equalsIgnoreCase("LocalVariableTable")) {
			attribute = new LocalVariableTable(type);
		}//else if//
		else if(name.equalsIgnoreCase("InnerClasses")) {
			attribute = new InnerClasses(type);
		}//else if//
		else if(name.equalsIgnoreCase("ConstantValue")) {
			attribute = new ConstantValue(type);
		}//else if//
		else if(name.equalsIgnoreCase("Synthetic")) {
			attribute = new Synthetic(type);
		}//else if//
		else {
			attribute = new Unidentified(type, name);
		}//else//
	
		attribute.nameIndex = nameIndex;
		attribute.readExternal(in);
	}//else//

	return attribute;
}//readAttribute()//
/**
 * Reads this object from the given stream.
 * @param in The input stream to read this object from.
 */
public void readExternal(java.io.ObjectInput in) throws java.io.IOException, ClassNotFoundException {
	if(this.nameIndex == -1) {
		//There is usually no need to read the name index since it is read in the readAttribute(Type, ObjectInput) method.//
		nameIndex = in.readShort();
	}//if//

	//Note: We leave it to the attribute to read the length of the attribute because some will require this info and most will ignore it.//
}//readExternal()//
/**
 * Sets the index of the attribute's name in the type's constant pool.
 * @param nameIndex The index of the attribute name.
 */
public void setNameIndex(short nameIndex) {
	this.nameIndex = nameIndex;
}//setNameIndex()//
/**
 * Writes this object to the given stream.
 * @param out The output stream to write this object to.
 */
public void writeExternal(java.io.ObjectOutput out) throws java.io.IOException {
	short nameIndex = getType().getConstantIndex(new ConstantUtf8(getType(), getDefaultName()));
	
	//Write the constant index referenceing the attribute name.//
	out.writeShort(nameIndex);
	//Write size in bytes of the attribute.//
	out.writeInt(getSize());
}//writeExternal()//
}//CodeAttribute//