channelbuffer.java

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/*
      Copyright (C) 2002-2004 MySQL AB

      This program is free software; you can redistribute it and/or modify
      it under the terms of version 2 of the GNU General Public License as 
      published by the Free Software Foundation.

      There are special exceptions to the terms and conditions of the GPL 
      as it is applied to this software. View the full text of the 
      exception in file EXCEPTIONS-CONNECTOR-J in the directory of this 
      software distribution.

      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.

      You should have received a copy of the GNU General Public License
      along with this program; if not, write to the Free Software
      Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA



 */
package com.mysql.jdbc;

import java.io.UnsupportedEncodingException;
import java.nio.ByteBuffer;

import java.sql.SQLException;


/**
 * Buffer contains code to read and write packets from/to the MySQL server.
 *
 * @version $Id: ChannelBuffer.java,v 1.1.2.21 2004/10/21 19:52:36 mmatthew Exp $
 * @author Mark Matthews
 */
class ChannelBuffer extends Buffer {

    private int bufLength = 0;
    //private int position = 0;
    
    private ByteBuffer directBuffer;
    
    private byte[] asBytes = null;
    private boolean dirty = true;
    
	ChannelBuffer(byte[] buf) {
			this.directBuffer = ByteBuffer.wrap(buf);
			setBufLength(buf.length);
	}
		
    ChannelBuffer(int size, boolean direct) {
        
        if (direct) {
        	this.directBuffer = ByteBuffer.allocateDirect(size);
        } else {
        	this.directBuffer = ByteBuffer.allocate(size);
        }
        
       	//this.directBuffer.limit(size);
        setBufLength(size);
        //this.position = MysqlIO.HEADER_LENGTH;
        this.directBuffer.position(MysqlIO.HEADER_LENGTH);
    }

	public ByteBuffer getNioBuffer() {
		return this.directBuffer;
	}
	
    /**
     * Sets the array of bytes to use as a buffer to read from.
     *
     * @param byteBuffer the array of bytes to use as a buffer
     */
    public void setByteBuffer(byte[] byteBuffer) {
    	this.directBuffer = ByteBuffer.wrap(byteBuffer);
    }

    /**
     * Returns the array of bytes this Buffer is using to read from.
     *
     * @return byte array being read from
     */
    public byte[] getByteBuffer() {
        return bufferToArray();
    }

    /**
     * Set the current position to write to/ read from
     *
     * @param position the position (0-based index)
     */
    public void setPosition(int position) {
        //this.position = position;
        this.directBuffer.position(position);
    }

    /**
     * Returns the current position to write to/ read from
     *
     * @return the current position to write to/ read from
     */
    public int getPosition() {
    	//if (directBuffer.position() != this.position) {
    	//	System.err.println("WARN: directBuffer position != this.position");
    	//}
    	
        return this.directBuffer.position();
    }

    /**
     * Skip over a length-encoded string
     *
     * @return The position past the end of the string
     */
    public int fastSkipLenString() {
        long len = this.readFieldLength();

        //position += len;
		
		this.directBuffer.position((int)(this.directBuffer.position() + len));
		
        return (int) len; // this is safe, as this is only
    }

    final byte[] getBytes(int len) {
        byte[] b = new byte[len];
        byte[] nioByteBuffer = bufferToArray();
         
        try {
        
        	System.arraycopy(nioByteBuffer, this.directBuffer.position(), b, 0, len);
        	//this.position += len; // update cursor
			this.directBuffer.position((this.directBuffer.position() + len));
        } catch (ArrayIndexOutOfBoundsException aiobex) {
        	throw aiobex;
        }
		
        return b;
    }

    // 2000-06-05 Changed
    final boolean isLastDataPacket() {
    	boolean hasMarker =  ((this.directBuffer.get(0) & 0xff) == 254);

    	return (hasMarker && this.bufLength < 9);
    }

    final void clear() {
        this.directBuffer.position(MysqlIO.HEADER_LENGTH);
    }



    final void ensureCapacity(int additionalData) throws SQLException {
		int bufferCapacity = this.directBuffer.capacity();
		
		int currentPosition = this.directBuffer.position();
		
        if ((currentPosition + additionalData) > getBufLength()) {
            if ((currentPosition + additionalData) < bufferCapacity) {
                // byteBuffer.length is != getBufLength() all of the time
                // due to re-using of packets (we don't shrink them)
                //
                // If we can, don't re-alloc, just set buffer length 
                // to size of current buffer
                setBufLength(currentPosition + additionalData);
            } else {
                //
                // Otherwise, re-size, and pad so we can avoid
                // allocing again in the near future
                //
                
                
                int newLength = (int) (bufferCapacity * 1.25);

				if (newLength < 4096) {
					newLength = 4096;
				}
				
                if (newLength < (bufferCapacity + additionalData)) {
                    newLength = bufferCapacity
                        + (int) (additionalData * 1.25);
                }

                if (newLength < bufferCapacity) {
                    newLength = bufferCapacity + additionalData;
                }

                ByteBuffer largerBuffer = ByteBuffer.allocateDirect(newLength);
               
                this.directBuffer.position(0);
                largerBuffer.put(this.directBuffer);
                this.directBuffer = largerBuffer;
                this.directBuffer.position(currentPosition);
                	
                bufferCapacity = this.directBuffer.capacity(); // re-alloc'd
                setBufLength(bufferCapacity);
                
                
            }
        }
    }

    final long newReadLength() {
        int sw = this.directBuffer.get(this.directBuffer.position()) & 0xff;
        this.directBuffer.position(this.directBuffer.position() + 1);

        switch (sw) {
        case 251:
            return 0;

        case 252:
            return readInt();

        case 253:
            return readLongInt();

        case 254: // changed for 64 bit lengths
            return readLongLong();

        default:
            return sw;
        }
    }

    final byte readByte() {
        byte b = this.directBuffer.get();

        return b;
    }
    
    final byte readByte(int readAt) {
		return this.directBuffer.get(readAt);
    }

    final long readFieldLength() {
        int sw = this.directBuffer.get() & 0xff;

        switch (sw) {
        case 251:
            return NULL_LENGTH;

        case 252:
            return readInt();

        case 253:
            return readLongInt();

        case 254:
            return readLongLong();

        default:
            return sw;
        }
    }

    final int readInt() {
        return (this.directBuffer.get() & 0xff) | ((this.directBuffer.get() & 0xff) << 8);
    }

    final int readIntAsLong() {
        int i = (this.directBuffer.get() & 0xff) | ((this.directBuffer.get() & 0xff) << 8)
        | ((this.directBuffer.get() & 0xff) << 16)
        | ((this.directBuffer.get() & 0xff) << 24);
        
		//this.directBuffer.position(this.position);
        
		return i;
    }

    final byte[] readLenByteArray(int offset) {
        long len = this.readFieldLength();

        if (len == NULL_LENGTH) {
            return null;
        }

        if (len == 0) {
            return Constants.EMPTY_BYTE_ARRAY;
        }

        this.directBuffer.position(this.directBuffer.position() + offset);
        //this.directBuffer.position(this.position);
        
        return getBytes((int) len);
    }

    final long readLength() {
        int sw = this.directBuffer.get() & 0xff;
		//this.directBuffer.position(this.position);
		
        switch (sw) {
        case 251:
            return 0;

        case 252:
            return readInt();

        case 253:
            return readLongInt();

        case 254:
            return readLong();

        default:
            return sw;
        }
    }

    final long readLong() {
        long l = (this.directBuffer.get() & 0xff) | ((this.directBuffer.get() & 0xff) << 8)
        | ((this.directBuffer.get() & 0xff) << 16)
        | ((this.directBuffer.get() & 0xff) << 24);
        
		//this.directBuffer.position(this.position);
        
		return l;
    }

    final int readLongInt() {
        
        int i = (this.directBuffer.get() & 0xff) | ((this.directBuffer.get() & 0xff) << 8)
        | ((this.directBuffer.get() & 0xff) << 16);
        
		//this.directBuffer.position(this.position);