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

[Jorn Vernee]

I agree with these arguments as well. Especially the native read might 
be problematic if toString() is called to haphazardly, better to make it 
more explicit.

I will change the implementation then.

Jorn

Sundararajan Athijegannathan schreef op 2018-12-14 16:06:
> This is primarily a debug utility. So it could be a static utility
> method on java.foreign.memory.Struct. i.e., we can walk through getter
> methods by reflection and call those to compute toString.
> 
> That way:
> 
> * we could avoid generating toString in every struct impl. class
> * possible issues with calling getters (which are native memory reads)
> from toString
> * Default toString can distinguish different instances of the same
> struct type (with the same field values)
> because of identity hash code. That is useful for debugging at times
> (involving struct copy/assignment for eg).
> 
> -Sundar
> 
> 
> On 14/12/18, 7:57 PM, Jorn Vernee wrote:
>> 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