CODEWITHSUNDEEP
netty
Craig Day
Craig Day

Reputation: 2535

Setting ByteBuf ENDIANNESS in Netty4

In Netty 3 we enforced LITTLE_ENDIAN ChannelBuffers on each end using

bootstrap.setOption("child.bufferFactory", new HeapChannelBufferFactory(ByteOrder.LITTLE_ENDIAN));

but in Netty 4, configuration of ByteBuf now appears to be via ChannelOption.ALLOCATOR:

    bootstrap.option(ChannelOption.ALLOCATOR, someAllocator);

All we really want to do is decorate UnpooledByteBufAllocator, but it is final and the methods we need to decorate are protected, so we cant extend the class or delegate to it. We have had to resort to a proxy approach:

private static class AllocatorProxyHandler implements InvocationHandler {
    private final ByteBufAllocator allocator;

    public AllocatorProxyHandler(ByteBufAllocator allocator) {
        this.allocator = allocator;
    }

    public static ByteBufAllocator proxy(ByteBufAllocator allocator) {
        return (ByteBufAllocator) Proxy.newProxyInstance(AllocatorProxyHandler.class.getClassLoader(), new Class[]{ByteBufAllocator.class}, new AllocatorProxyHandler(allocator));
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        Object result = method.invoke(allocator, args);
        if (result instanceof ByteBuf) {
            return ((ByteBuf) result).order(ByteOrder.LITTLE_ENDIAN);
        } else {
            return result;
        }
    }
}

setting the Bootstrap option like this:

    bootstrap.option(ChannelOption.ALLOCATOR, AllocatorProxyHandler.proxy(UnpooledByteBufAllocator.DEFAULT));

Is there some other (better) way to do this we are missing?

Upvotes: 1

Views: 3080

Answers (1)

trustin
trustin

Reputation: 12351

Netty 4.0's ByteBuf is big-endian by default. You can get the little-endian view of the ByteBuf using the order(ByteOrder) method:

ByteBuf buf = ctx.alloc().buffer();
ByteBuf leBuf = buf.order(ByteOrder.LITTLE_ENDIAN);
leBuf.getByte(...);
...

This is by design to avoid any confusion caused by keeping byte order as a state variable. If there is a good reason why it has to provide a way to change the default byte order, please let us know so we can reconsider this decision.

Upvotes: 2

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