ByteBuf用法

 //初始化ByteBuf，读写索引都为0；
ByteBuf buf = Unpooled.buffer(10);//非池化10字节大小的ByteBuf
System.out.println(buf.toString());//UnpooledHeapByteBuf(ridx: 0, widx: 0, cap: 10)
System.out.println( Arrays.toString(buf.array()));//[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
//写入5个字节的数组，写索引变为5；
byte[] bytes = {1,2,3,4,5};
buf.writeBytes(bytes);
System.out.println(buf.toString());//UnpooledHeapByteBuf(ridx: 0, widx: 5, cap: 10)
System.out.println(Arrays.toString(buf.array()));//[1, 2, 3, 4, 5, 0, 0, 0, 0, 0]
//读取两个字节，写索引为5，读索引2
byte b1 = buf.readByte();
byte b2 = buf.readByte();
System.out.println(Arrays.toString(new byte[]{b1,b2}));
System.out.println(buf.toString());//UnpooledHeapByteBuf(ridx: 2, widx: 5, cap: 10)
System.out.println(Arrays.toString(buf.array()));//[1, 2, 3, 4, 5, 0, 0, 0, 0, 0]
//将读取的内容丢弃后，读索引0，写索引(5-2)=3
buf.discardReadBytes();//将读取的内容丢弃
System.out.println(buf.toString());//UnpooledHeapByteBuf(ridx: 0, widx: 3, cap: 10)
System.out.println(Arrays.toString(buf.array()));//[3, 4, 5, 4, 5, 0, 0, 0, 0, 0]
System.out.println(buf.readableBytes());//返回可读字节的个数；  3
System.out.println(buf.writableBytes());//返回可写字节的个数；  7
//清空读写指针，读写指针都为0，clear并不会清空缓冲区内容本身，主要用来操作指针；
buf.clear();
System.out.println(buf.toString());//UnpooledHeapByteBuf(ridx: 0, widx: 0, cap: 10)
System.out.println(Arrays.toString(buf.array()));//[3, 4, 5, 4, 5, 0, 0, 0, 0, 0]
//再次写入一段内容
byte[] bytes2 = {1,2,3};
buf.writeBytes(bytes2);
buf.readByte();
System.out.println(Arrays.toString(bytes2));
System.out.println(buf.toString());//UnpooledHeapByteBuf(ridx: 1, widx: 3, cap: 10)
System.out.println(Arrays.toString(buf.array()));//[1, 2, 3, 4, 5, 0, 0, 0, 0, 0]
// 将ByteBuf清零，读写索引都不变
buf.setZero(0,buf.capacity());
System.out.println(buf.toString());//UnpooledHeapByteBuf(ridx: 1, widx: 3, cap: 10)
System.out.println(Arrays.toString(buf.array()));//[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
Charset utf8 = Charset.forName("UTF-8");
ByteBuf buf1 = Unpooled.copiedBuffer("Netty in Action rocks!", utf8);
ByteBuf sliced = buf1.slice(0, 14);
ByteBuf copy = buf1.copy(0, 14);
System.out.println(buf1.toString(utf8));//Netty in Action rocks!
System.out.println("是否支持访问数组:"+buf1.hasArray());//false  访问非堆缓冲区ByteBuf的数组会导致UnsupportedOperationException,因此下面的访问方式会报错
//System.out.println(Arrays.toString(buf1.array()));
System.out.println(sliced.toString(utf8));//Netty in Actio
//System.out.println(Arrays.toString(sliced.array()));
System.out.println(copy.toString(utf8));//Netty in Actio
//System.out.println(Arrays.toString(copy.array()));
buf1.setByte(0, (byte)'J');//get和set操作读写指定索引的数据，而不会改变索引值。read和write操作读写指定索引数据，并且会改变索引的值
System.out.println(buf1.toString(utf8));//Jetty in Action rocks!
//由于数据是共享的，对一个ByteBuf的修改对原始的ByteBuf是可见的
System.out.println(sliced.toString(utf8));//Jetty in Actio
//copy方法会重新分配新的ByteBuf，对其的修改对原始的ByteBuf不可见。
System.out.println(copy.toString(utf8));//Netty in Actio
System.out.println(buf1.getByte(0)==sliced.getByte(0));//true
System.out.println(buf1.getByte(0)==copy.getByte(0));//false