/*
 * Copyright  2000-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); 
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License. 
 *
 */
package org.apache.bcel.classfile;

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

import org.apache.bcel.Constants;

/**
 * This class represents a reference to an unknown (i.e., application-specific)
 * attribute of a class. It is instantiated from the
 * <em>Attribute.readAttribute()</em> method. Applications that need to read in
 * application-specific attributes should create an <a
 * href="./AttributeReader.html">AttributeReader</a> implementation and attach
 * it via <a href="./Attribute.html#addAttributeReader(java.lang.String,
 * org.apache.bcel.classfile.AttributeReader)">Attribute.addAttributeReader</a>.
 * 
 * 
 * @version $Id: Unknown.java 386056 2006-03-15 11:31:56Z tcurdt $
 * @see org.apache.bcel.classfile.Attribute
 * @see org.apache.bcel.classfile.AttributeReader
 * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
 */
public final class Unknown extends Attribute {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private byte[] bytes;
	private String name;
	private static Map<String, Unknown> unknown_attributes = new HashMap<String, Unknown>();

	/**
	 * @return array of unknown attributes, but just one for each kind.
	 */
	static Unknown[] getUnknownAttributes() {
		Unknown[] unknowns = new Unknown[unknown_attributes.size()];
		Iterator<Unknown> entries = unknown_attributes.values().iterator();
		for (int i = 0; entries.hasNext(); i++) {
			unknowns[i] = entries.next();
		}
		unknown_attributes.clear();
		return unknowns;
	}

	/**
	 * Initialize from another object. Note that both objects use the same
	 * references (shallow copy). Use clone() for a physical copy.
	 */
	public Unknown(Unknown c) {
		this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
	}

	/**
	 * Create a non-standard attribute.
	 * 
	 * @param name_index
	 *            Index in constant pool
	 * @param length
	 *            Content length in bytes
	 * @param bytes
	 *            Attribute contents
	 * @param constant_pool
	 *            Array of constants
	 */
	public Unknown(int name_index, int length, byte[] bytes,
			ConstantPool constant_pool) {
		super(Constants.ATTR_UNKNOWN, name_index, length, constant_pool);
		this.bytes = bytes;
		name = ((ConstantUtf8) constant_pool.getConstant(name_index,
				Constants.CONSTANT_Utf8)).getBytes();
		unknown_attributes.put(name, this);
	}

	/**
	 * Construct object from file stream.
	 * 
	 * @param name_index
	 *            Index in constant pool
	 * @param length
	 *            Content length in bytes
	 * @param file
	 *            Input stream
	 * @param constant_pool
	 *            Array of constants
	 * @throws IOException
	 */
	Unknown(int name_index, int length, DataInputStream file,
			ConstantPool constant_pool) throws IOException {
		this(name_index, length, (byte[]) null, constant_pool);
		if (length > 0) {
			bytes = new byte[length];
			file.readFully(bytes);
		}
	}

	/**
	 * Called by objects that are traversing the nodes of the tree implicitely
	 * defined by the contents of a Java class. I.e., the hierarchy of methods,
	 * fields, attributes, etc. spawns a tree of objects.
	 * 
	 * @param v
	 *            Visitor object
	 */
	@Override
	public void accept(Visitor v) {
		v.visitUnknown(this);
	}

	/**
	 * Dump unknown bytes to file stream.
	 * 
	 * @param file
	 *            Output file stream
	 * @throws IOException
	 */
	@Override
	public final void dump(DataOutputStream file) throws IOException {
		super.dump(file);
		if (length > 0) {
			file.write(bytes, 0, length);
		}
	}

	/**
	 * @return data bytes.
	 */
	public final byte[] getBytes() {
		return bytes;
	}

	/**
	 * @return name of attribute.
	 */
	public final String getName() {
		return name;
	}

	/**
	 * @param bytes
	 *            the bytes to set
	 */
	public final void setBytes(byte[] bytes) {
		this.bytes = bytes;
	}

	/**
	 * @return String representation.
	 */
	@Override
	public final String toString() {
		if (length == 0 || bytes == null) {
			return "(Unknown attribute " + name + ")";
		}
		String hex;
		if (length > 10) {
			byte[] tmp = new byte[10];
			System.arraycopy(bytes, 0, tmp, 0, 10);
			hex = Utility.toHexString(tmp) + "... (truncated)";
		} else {
			hex = Utility.toHexString(bytes);
		}
		return "(Unknown attribute " + name + ": " + hex + ")";
	}

	/**
	 * @return deep copy of this attribute
	 */
	@Override
	public Attribute copy(ConstantPool _constant_pool) {
		Unknown c = (Unknown) clone();
		if (bytes != null) {
			c.bytes = new byte[bytes.length];
			System.arraycopy(bytes, 0, c.bytes, 0, bytes.length);
		}
		c.constant_pool = _constant_pool;
		return c;
	}
}
