Java tutorial
package com.tesora.dve.db.mysql.portal.protocol; /* * #%L * Tesora Inc. * Database Virtualization Engine * %% * Copyright (C) 2011 - 2014 Tesora Inc. * %% * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License, version 3, * as published by the Free Software Foundation. * * 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 Affero General Public License for more details. * * You should have received a copy of the GNU Affero General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. * #L% */ import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.ChannelHandlerContext; import io.netty.util.ReferenceCountUtil; import io.netty.util.internal.PlatformDependent; import java.nio.ByteOrder; /** * */ public class CachedAppendBuffer { public static final int SLAB_SIZE = 1024 * 8;//start with a 8K slab for transcoding outbound writes. static boolean PREFER_DIRECT = PlatformDependent.directBufferPreferred(); int appendStartedAtIndex; ByteBuf cachedSlab; public void allocateSlabIfNeeded(ChannelHandlerContext ctx) { if (cachedSlab != null) //we already have a slab. return; if (PREFER_DIRECT) { cachedSlab = ctx.alloc().ioBuffer(SLAB_SIZE); } else { cachedSlab = ctx.alloc().heapBuffer(SLAB_SIZE); } cachedSlab = cachedSlab.order(ByteOrder.LITTLE_ENDIAN); } public ByteBuf startAppend(ChannelHandlerContext ctx) { allocateSlabIfNeeded(ctx); //if we don't have any outbound slices holding references, reset to full slab. if (cachedSlab.refCnt() == 1) { cachedSlab.clear(); } appendStartedAtIndex = cachedSlab.writerIndex(); return cachedSlab; } public ByteBuf sliceWritableData() { int writtenLength = cachedSlab.writerIndex() - appendStartedAtIndex; if (writtenLength <= 0) return Unpooled.EMPTY_BUFFER; else { ByteBuf sliceSinceStarted = cachedSlab.slice(appendStartedAtIndex, writtenLength).retain(); //this will be written out to netty, so inc the ref count. return sliceSinceStarted; } } public void releaseSlab() { ReferenceCountUtil.release(cachedSlab); cachedSlab = null; } }