ResultSetHeaderPacket.java

/*
 * Copyright 2015 Liu Huanting.
 * 
 * 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 fm.liu.timo.mysql.packet;

import java.nio.ByteBuffer;
import fm.liu.timo.mysql.BufferUtil;
import fm.liu.timo.mysql.MySQLMessage;

/**
 * From server to client after command, if no error and result set -- that is, if the command was a
 * query which returned a result set. The Result Set Header Packet is the first of several, possibly
 * many, packets that the server sends for result sets. The order of packets for a result set is:
 * 
 * <pre>
 * (Result Set Header Packet)   the number of columns
 * (Field Packets)              column descriptors
 * (EOF Packet)                 marker: end of Field Packets
 * (Row Data Packets)           row contents
 * (EOF Packet)                 marker: end of Data Packets
 * 
 * Bytes                        Name
 * -----                        ----
 * 1-9   (Length-Coded-Binary)  field_count
 * 1-9   (Length-Coded-Binary)  extra
 * 
 * @see http://forge.mysql.com/wiki/MySQL_Internals_ClientServer_Protocol#Result_Set_Header_Packet
 * </pre>
 * 
 */
public class ResultSetHeaderPacket extends ResultSetPacket {

    public int  fieldCount;
    public long extra;

    @Override
    protected void readBody(MySQLMessage mm) {
        this.fieldCount = (int) mm.readLength();
        if (mm.hasRemaining()) {
            this.extra = mm.readLength();
        }
    }

    @Override
    public int calcPacketSize() {
        int size = BufferUtil.getLength(fieldCount);
        if (extra > 0) {
            size += BufferUtil.getLength(extra);
        }
        return size;
    }

    @Override
    protected String getPacketInfo() {
        return "MySQL ResultSetHeader Packet";
    }

    @Override
    protected void writeBody(ByteBuffer buffer) {
        BufferUtil.writeLength(buffer, fieldCount);
        if (extra > 0) {
            BufferUtil.writeLength(buffer, extra);
        }
    }

}