[foreign] RFR: Add a toString method to struct impl classes.

[Jorn Vernee]

Updated webrev: 
http://cr.openjdk.java.net/~jvernee/panama/webrevs/structtostring/webrev.02/

* Added static toString method to java.foreign.memory.Struct that 
reflectively walks getters declared in the struct's layout annotation to 
create a string representation.

Jorn

Jorn Vernee schreef op 2018-12-14 15:27:
> Hi,
> 
> During porting the binder to Windows I wrote a bunch of debugging
> code. I thought this might be useful to have in the future, and I'd
> like to handle these so I can remove them from my other local changes
> (less stuff to maintain), so I'm creating this RFR. There are 3
> subjects that I've split into 3 patches; This is the first one.
> 
> 1.) toString method generation for Structs. This adds generation of a
> toString method to StructImplGenerator, which uses the struct's
> getters to output the values of the struct e.g.
> 
> 
> @NativeStruct("[i32(get=one$get)(set=one$set)i32(get=two$get)(set=two$set)]")
>     public interface MyStruct extends Struct<MyStruct> {
>         int one$get();
>         void one$set(int i);
> 
>         int two$get();
>         void two$set(int i);
>     }
> 
>     public static void main(String[] args) throws 
> IllegalAccessException {
>         try(var scope = Scope.newNativeScope()) {
>             MyStruct s = scope.allocateStruct(MyStruct.class);
> 
>             s.one$set(10);
>             s.two$set(20);
> 
>             System.out.println(s);
>         }
>     }
> 
> Will output:
> 
>     Main$MyStruct{ one$get=10, two$get=20 }
> 
> Webrev:
> http://cr.openjdk.java.net/~jvernee/panama/webrevs/structtostring/webrev.01/
> 
> Please let me know what you think and if you want to have this in the
> repo, otherwise I will just throw it away.
> 
> Cheers,
> Jorn