8245121: (bf) XBuffer.put(Xbuffer src) can give unexpected result when storage overlaps

[Paul Sandoz]

There we go :-) I found it took me a couple rounds of writing tests to settle on a few useful patterns. Generally it would be useful if we had a test library for creating combinations, permutations, zipping etc. (CC’ing Pavel)

I have one other request and one comment, both of which you can choose to ignore if you wanna wrap this up.

- change the implementations of MyRandom.next$Type to use next(<size-of-type-in-bits>) rather than your use your own shifting logic.

- typeToAttr can be constructed using Map.of:
  Map.of(
    byte.class, TypeAttr.of(ByteBuffer.class, Byte.BYTES, “Byte”),
    char.class, …
    …,
  )
In fact TypeAttr really really wants to be a record (nominal tuple). I believe we can use preview features in tests, and it is worthwhile to do so (gaining more coverage).

Paul.


> On May 28, 2020, at 5:57 PM, Brian Burkhalter <brian.burkhalter at oracle.com> wrote:
> 
> 
>> On May 28, 2020, at 5:21 PM, Paul Sandoz <paul.sandoz at oracle.com <mailto:paul.sandoz at oracle.com>> wrote:
>> 
>> Here’s a tip, rather than creating a fixed size array upfront:
>> 
>> - create a List<Object[]> to add argument list combinations to
>> - add with args.add(new Object[] {proxy})
>> - at the end do args.toArray(Object[][]::new)
> 
> Cool - thanks!
> 
>> For:
>> 
>>  281             List<BufferProxy> proxies1 = getProxies(type);
>>  282             List<BufferProxy> proxies2 = getProxies(type);
>>  283             for (BufferProxy proxy1 : proxies1) {
>>  284                 for (BufferProxy proxy2 : proxies2) {
>>  285                     data[index][0] = proxy1;
>>  286                     data[index++][1] = proxy2;
>>  287                 }
>>  288             }
>> 
>> Can you reuse proxy1 since the list is not modified and the proxy is stateless w.r.t. Buffers? Is it necessary to test when proxy1 == proxy2 i.e. the diagonal?
> 
> Good point. Yes I think it can be re-used as there is no relevant state. I don’t think it’s necessary to check for proxy1 == proxy2: we want to test the case where both are the same type, kind, and order.
> 
>> It’s useful to try the streams approach as an exercise, I can imagine some people might find nested flatMaps a little jarring. The nested loops are fine here.
> 
> The updated version is at
> 
> http://cr.openjdk.java.net/~bpb/ <http://cr.openjdk.java.net/~bpb/>8245121/webrev.04/
> 
> It keeps getting shorter!
> 
> Thanks,
> 
> Brian

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