/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.jk.core;

import java.io.IOException;

import org.apache.tomcat.util.buf.ByteChunk;
import org.apache.tomcat.util.buf.MessageBytes;


/**
 * A single packet for communication between the web server and the
 * container.
 *
 * In a more generic sense, it's the event that drives the processing chain.
 * XXX Use Event, make Msg a particular case.
 *
 * @author Henri Gomez [hgomez@apache.org]
 * @author Dan Milstein [danmil@shore.net]
 * @author Keith Wannamaker [Keith@Wannamaker.org]
 * @author Kevin Seguin
 * @author Costin Manolache
 */
public abstract class Msg {

    
    /**
     * Prepare this packet for accumulating a message from the container to
     * the web server.  Set the write position to just after the header
     * (but leave the length unwritten, because it is as yet unknown).
     */
    public abstract void reset();

    /**
     * For a packet to be sent to the web server, finish the process of
     * accumulating data and write the length of the data payload into
     * the header.  
     */
    public abstract void end();

    public abstract  void appendInt( int val );

    public abstract void appendByte( int val );
	
    public abstract void appendLongInt( int val );

    /**
     */
    public abstract void appendBytes(MessageBytes mb) throws IOException;

    public abstract void appendByteChunk(ByteChunk bc) throws IOException;
    
    /** 
     * Copy a chunk of bytes into the packet, starting at the current
     * write position.  The chunk of bytes is encoded with the length
     * in two bytes first, then the data itself, and finally a
     * terminating \0 (which is <B>not</B> included in the encoded
     * length).
     *
     * @param b The array from which to copy bytes.
     * @param off The offset into the array at which to start copying
     * @param numBytes The number of bytes to copy.  
     */
    public abstract void appendBytes( byte b[], int off, int numBytes );

    /**
     * Read an integer from packet, and advance the read position past
     * it.  Integers are encoded as two unsigned bytes with the
     * high-order byte first, and, as far as I can tell, in
     * little-endian order within each byte.  
     */
    public abstract int getInt();

    public abstract int peekInt();

    public abstract byte getByte();

    public abstract byte peekByte();

    public abstract void getBytes(MessageBytes mb);
    
    /**
     * Copy a chunk of bytes from the packet into an array and advance
     * the read position past the chunk.  See appendBytes() for details
     * on the encoding.
     *
     * @return The number of bytes copied.
     */
    public abstract int getBytes(byte dest[]);

    /**
     * Read a 32 bits integer from packet, and advance the read position past
     * it.  Integers are encoded as four unsigned bytes with the
     * high-order byte first, and, as far as I can tell, in
     * little-endian order within each byte.
     */
    public abstract int getLongInt();

    public abstract int getHeaderLength();

    public abstract int processHeader();

    public abstract byte[] getBuffer();

    public abstract int getLen();
    
    public abstract void dump(String msg);

    /* -------------------- Utilities -------------------- */
    // XXX Move to util package

    public static String hexLine( byte buf[], int start, int len ) {
        StringBuffer sb=new StringBuffer();
        for( int i=start; i< start+16 ; i++ ) {
            if( i < len + 4)
                sb.append( hex( buf[i] ) + " ");
            else
                sb.append( "   " );
        }
        sb.append(" | ");
        for( int i=start; i < start+16 && i < len + 4; i++ ) {
            if( ! Character.isISOControl( (char)buf[i] ))
                sb.append( new Character((char)buf[i]) );
            else
                sb.append( "." );
        }
        return sb.toString();
    }

    private  static String hex( int x ) {
        //	    if( x < 0) x=256 + x;
        String h=Integer.toHexString( x );
        if( h.length() == 1 ) h = "0" + h;
        return h.substring( h.length() - 2 );
    }


}