netty buttyBuf的三种复制方式

copy 物理复制，复制数据构成新buf，且与原buf无关，大小等于数据长度

duplicate 逻辑复制，复制原buf的索引构成新buf，和原数据一模一样

slice 切片，获取原buf指定范围的映射，大小等于切片的数据长度

@Test
public void test2() {
	ByteBuf b = getBuf();
	System.out.println("原始数据:" + b);
	//原始数据:UnpooledByteBufAllocator$InstrumentedUnpooledUnsafeHeapByteBuf(ridx: 4, widx: 12, cap: 1024)


	b = getBuf();
	System.out.println("copy:" + b.copy());
	//copy:UnpooledByteBufAllocator$InstrumentedUnpooledUnsafeHeapByteBuf(ridx: 0, widx: 8, cap: 8)


	b = getBuf();
	System.out.println("duplicate：" + b.duplicate());
	//duplicate：UnpooledDuplicatedByteBuf(ridx: 4, widx: 12, cap: 1024, unwrapped: UnpooledByteBufAllocator$InstrumentedUnpooledUnsafeHeapByteBuf(ridx: 4, widx: 12, cap: 1024))


	b = getBuf();
	System.out.println("slice;" + b.slice());
	//slice;UnpooledSlicedByteBuf(ridx: 0, widx: 8, cap: 8/8, unwrapped: UnpooledByteBufAllocator$InstrumentedUnpooledUnsafeHeapByteBuf(ridx: 4, widx: 12, cap: 1024))

}

//返回一个总长度为1024，数据长度为12，读索引为4，写索引为12的bytebuf
public static ByteBuf getBuf() {
	ByteBuf b = Unpooled.buffer(1024);
	b.writeInt(1);
	b.writeInt(2);
	b.writeInt(3);
	b.readInt();
	return b;
}