NativeHandler

/**
* Copyright (c) 2008 Greg Whalin
* All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the BSD license
*
* This library 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.
*
* You should have received a copy of the BSD License along with this
* library.
*
* @author Greg Whalin <[e-mail]>
*/
package com.yulong.memcached;

import java.util.Date;
import org.apache.log4j.Logger;

/**
* Handle encoding standard Java types directly which can result in significant
* memory savings:
*
* Currently the Memcached driver for Java supports the setSerialize() option.
* This can increase performance in some situations but has a few issues:
*
* Code that performs class casting will throw ClassCastExceptions when
* setSerialize is enabled. For example:
*
*     mc.set( "foo", new Integer( 1 ) ); Integer output = (Integer)mc.get("foo");
*
* Will work just file when setSerialize is true but when its false will just throw
* a ClassCastException.
*
* Also internally it doesn't support Boolean and since toString is called wastes a
* lot of memory and causes additional performance issue.  For example an Integer
* can take anywhere from 1 byte to 10 bytes.
*
* Due to the way the memcached slab allocator works it seems like a LOT of wasted
* memory to store primitive types as serialized objects (from a performance and
* memory perspective).  In our applications we have millions of small objects and
* wasted memory would become a big problem.
*
* For example a Serialized Boolean takes 47 bytes which means it will fit into the
* 64byte LRU.  Using 1 byte means it will fit into the 8 byte LRU thus saving 8x
* the memory.  This also saves the CPU performance since we don't have to
* serialize bytes back and forth and we can compute the byte[] value directly.
*
* One problem would be when the user calls get() because doing so would require
* the app to know the type of the object stored as a bytearray inside memcached
* (since the user will probably cast).
*
* If we assume the basic types are interned we could use the first byte as the
* type with the remaining bytes as the value.  Then on get() we could read the
* first byte to determine the type and then construct the correct object for it.
* This would prevent the ClassCastException I talked about above.
*
* We could remove the setSerialize() option and just assume that standard VM types
* are always internd in this manner.
*
* mc.set( "foo", new Boolean.TRUE ); Boolean b = (Boolean)mc.get( "foo" );
*
* And the type casts would work because internally we would create a new Boolean
* to return back to the client.
*
* This would reduce memory footprint and allow for a virtual implementation of the
* Externalizable interface which is much faster than Serialzation.
*
* Currently the memory improvements would be:
*
* java.lang.Boolean - 8x performance improvement (now just two bytes)
* java.lang.Integer - 16x performance improvement (now just 5 bytes)
*
* Most of the other primitive types would benefit from this optimization.
* java.lang.Character being another obvious example.
*
* I know it seems like I'm being really picky here but for our application I'd
* save 1G of memory right off the bat.  We'd go down from 1.152G of memory used
* down to 144M of memory used which is much better IMO.
*
* http://java.sun.com/docs/books/tutorial/native1.1/integrating/types.html
*
* @author <a href="mailto:[e-mail]">Kevin A. Burton</a>
* @author Greg Whalin <[e-mail]>
*/
public class NativeHandler {

// logger
private static Logger log =
Logger.getLogger( NativeHandler.class.getName() );

/**
* Detemine of object can be natively serialized by this class.
*
* @param value Object to test.
* @return true/false
*/
public static boolean isHandled( Object value ) {

return (
value instanceof Byte            ||
value instanceof Boolean         ||
value instanceof Integer         ||
value instanceof Long            ||
value instanceof Character       ||
value instanceof String          ||
value instanceof StringBuffer    ||
value instanceof Float           ||
value instanceof Short           ||
value instanceof Double          ||
value instanceof Date            ||
value instanceof StringBuilder   ||
value instanceof byte[]
)
? true
: false;
    }

/**
* Returns the flag for marking the type of the byte array.
*
* @param value Object we are storing.
* @return int marker
*/
public static int getMarkerFlag( Object value ) {

if ( value instanceof Byte )
return MemcachedClient.MARKER_BYTE;

if ( value instanceof Boolean )
return MemcachedClient.MARKER_BOOLEAN;

if ( value instanceof Integer )
return MemcachedClient.MARKER_INTEGER;

if ( value instanceof Long )
return MemcachedClient.MARKER_LONG;

if ( value instanceof Character )
return MemcachedClient.MARKER_CHARACTER;

if ( value instanceof String )
return MemcachedClient.MARKER_STRING;

if ( value instanceof StringBuffer )
return MemcachedClient.MARKER_STRINGBUFFER;

if ( value instanceof Float )
return MemcachedClient.MARKER_FLOAT;

if ( value instanceof Short )
return MemcachedClient.MARKER_SHORT;

if ( value instanceof Double )
return MemcachedClient.MARKER_DOUBLE;

if ( value instanceof Date )
return MemcachedClient.MARKER_DATE;

if ( value instanceof StringBuilder )
return MemcachedClient.MARKER_STRINGBUILDER;

if ( value instanceof byte[] )
return MemcachedClient.MARKER_BYTEARR;

return -1;
}

/**
* Encodes supported types
*
* @param value Object to encode.
* @return byte array
*
* @throws Exception If fail to encode.
*/
public static byte[] encode( Object value ) throws Exception {

if ( value instanceof Byte )
return encode( (Byte)value );

if ( value instanceof Boolean )
return encode( (Boolean)value );

if ( value instanceof Integer )
return encode( ((Integer)value).intValue() );

if ( value instanceof Long )
return encode( ((Long)value).longValue() );

if ( value instanceof Character )
return encode( (Character)value );

if ( value instanceof String )
return encode( (String)value );

if ( value instanceof StringBuffer )
return encode( (StringBuffer)value );

if ( value instanceof Float )
return encode( ((Float)value).floatValue() );

if ( value instanceof Short )
return encode( (Short)value );

if ( value instanceof Double )
return encode( ((Double)value).doubleValue() );

if ( value instanceof Date )
return encode( (Date)value);

if ( value instanceof StringBuilder )
return encode( (StringBuilder)value );

if ( value instanceof byte[] )
return encode( (byte[])value );

return null;
}

protected static byte[] encode( Byte value ) {
byte[] b = new byte[1];
b[0] = value.byteValue();
return b;
}

protected static byte[] encode( Boolean value ) {
byte[] b = new byte[1];

if ( value.booleanValue() )
b[0] = 1;
else
b[0] = 0;

return b;
}

protected static byte[] encode( int value ) {
return getBytes( value );
}

protected static byte[] encode( long value ) throws Exception {
return getBytes( value );
}

protected static byte[] encode( Date value ) {
return getBytes( value.getTime() );
}

protected static byte[] encode( Character value ) {
return encode( value.charValue() );
}

protected static byte[] encode( String value ) throws Exception {
return value.getBytes( "UTF-8" );
}

protected static byte[] encode( StringBuffer value ) throws Exception {
return encode( value.toString() );
}

protected static byte[] encode( float value ) throws Exception {
return encode( (int)Float.floatToIntBits( value ) );
}

protected static byte[] encode( Short value ) throws Exception {
return encode( (int)value.shortValue() );
}

protected static byte[] encode( double value ) throws Exception {
return encode( (long)Double.doubleToLongBits( value ) );
}

protected static byte[] encode( StringBuilder value ) throws Exception {
return encode( value.toString() );
}

protected static byte[] encode( byte[] value ) {
return value;
}

protected static byte[] getBytes( long value ) {
byte[] b = new byte[8];
b[0] = (byte)((value >> 56) & 0xFF);
b[1] = (byte)((value >> 48) & 0xFF);
b[2] = (byte)((value >> 40) & 0xFF);
b[3] = (byte)((value >> 32) & 0xFF);
b[4] = (byte)((value >> 24) & 0xFF);
b[5] = (byte)((value >> 16) & 0xFF);
b[6] = (byte)((value >> & 0xFF);
b[7] = (byte)((value >> 0) & 0xFF);
return b;
}

protected static byte[] getBytes( int value ) {
byte[] b = new byte[4];
b[0] = (byte)((value >> 24) & 0xFF);
b[1] = (byte)((value >> 16) & 0xFF);
b[2] = (byte)((value >> & 0xFF);
b[3] = (byte)((value >> 0) & 0xFF);
return b;
}

/**
* Decodes byte array using memcache flag to determine type.
*
* @param b
* @param marker
* @return
* @throws Exception
*/
public static Object decode( byte[] b, int flag ) throws Exception {

if ( b.length < 1 )
return null;


if ( ( flag & MemcachedClient.MARKER_BYTE ) == MemcachedClient.MARKER_BYTE )
return decodeByte( b );

if ( ( flag & MemcachedClient.MARKER_BOOLEAN ) == MemcachedClient.MARKER_BOOLEAN )
return decodeBoolean( b );

if ( ( flag & MemcachedClient.MARKER_INTEGER ) == MemcachedClient.MARKER_INTEGER )
return decodeInteger( b );

if ( ( flag & MemcachedClient.MARKER_LONG ) == MemcachedClient.MARKER_LONG )
return decodeLong( b );

if ( ( flag & MemcachedClient.MARKER_CHARACTER ) == MemcachedClient.MARKER_CHARACTER )
return decodeCharacter( b );

if ( ( flag & MemcachedClient.MARKER_STRING ) == MemcachedClient.MARKER_STRING )
return decodeString( b );

if ( ( flag & MemcachedClient.MARKER_STRINGBUFFER ) == MemcachedClient.MARKER_STRINGBUFFER )
return decodeStringBuffer( b );

if ( ( flag & MemcachedClient.MARKER_FLOAT ) == MemcachedClient.MARKER_FLOAT )
return decodeFloat( b );

if ( ( flag & MemcachedClient.MARKER_SHORT ) == MemcachedClient.MARKER_SHORT )
return decodeShort( b );

if ( ( flag & MemcachedClient.MARKER_DOUBLE ) == MemcachedClient.MARKER_DOUBLE )
return decodeDouble( b );

if ( ( flag & MemcachedClient.MARKER_DATE ) == MemcachedClient.MARKER_DATE )
return decodeDate( b );

if ( ( flag & MemcachedClient.MARKER_STRINGBUILDER ) == MemcachedClient.MARKER_STRINGBUILDER )
return decodeStringBuilder( b );

if ( ( flag & MemcachedClient.MARKER_BYTEARR ) == MemcachedClient.MARKER_BYTEARR )
return decodeByteArr( b );

return null;
}

// decode methods
protected static Byte decodeByte( byte[] b ) {
return new Byte( b[0] );
}

protected static Boolean decodeBoolean( byte[] b ) {
boolean value = b[0] == 1;
return ( value ) ? Boolean.TRUE : Boolean.FALSE;
}

protected static Integer decodeInteger( byte[] b ) {
return new Integer( toInt( b ) );
}

protected static Long decodeLong( byte[] b ) throws Exception {
return new Long( toLong( b ) );
}

protected static Character decodeCharacter( byte[] b ) {
return new Character( (char)decodeInteger( b ).intValue() );
}

protected static String decodeString( byte[] b ) throws Exception {
return new String( b, "UTF-8" );
}

protected static StringBuffer decodeStringBuffer( byte[] b ) throws Exception {
return new StringBuffer( decodeString( b ) );
}

protected static Float decodeFloat( byte[] b ) throws Exception {
Integer l = decodeInteger( b );
return new Float( Float.intBitsToFloat( l.intValue() ) );
}

protected static Short decodeShort( byte[] b ) throws Exception {
return new Short( (short)decodeInteger( b ).intValue() );
}

protected static Double decodeDouble( byte[] b ) throws Exception {
Long l = decodeLong( b );
return new Double( Double.longBitsToDouble( l.longValue() ) );
}

protected static Date decodeDate( byte[] b ) {
return new Date( toLong( b ) );
}

protected static StringBuilder decodeStringBuilder( byte[] b ) throws Exception {
return new StringBuilder( decodeString( b ) );
}

protected static byte[] decodeByteArr( byte[] b ) {
return b;
}

/**
* This works by taking each of the bit patterns and converting them to
* ints taking into account 2s complement and then adding them..
*
* @param b
* @return
*/
protected static int toInt( byte[] b ) {
return (((((int) b[3]) & 0xFF) << 32) +
((((int) b[2]) & 0xFF) << 40) +
((((int) b[1]) & 0xFF) << 48) +
((((int) b[0]) & 0xFF) << 56));
}   

protected static long toLong( byte[] b ) {
return ((((long) b[7]) & 0xFF) +
((((long) b[6]) & 0xFF) << +
((((long) b[5]) & 0xFF) << 16) +
((((long) b[4]) & 0xFF) << 24) +
((((long) b[3]) & 0xFF) << 32) +
((((long) b[2]) & 0xFF) << 40) +
((((long) b[1]) & 0xFF) << 48) +
((((long) b[0]) & 0xFF) << 56));
}   
}