Hi Max
2015-04-26 19:29 GMT+02:00 Max Leske <[email protected]>:
> Hi guys
>
> I have a problem with NBExternalArray. AFAICT the generated assembly
> should be able to handle arbitrary elements in the array (as long as they
> are all of the same type). The operations required to read / write an
> element are given by the external type specified for the collection (e.g
> ‘char’ or ‘int’). All of this works wonderfully for char, int,
> NBExternalAddress etc. But I’m trying to get it working for strings. So
> here is the code that I would expect to work:
>
> arrayClass := NBExternalArray anonymousSubclassInitElementType: 'String'.
> array := arrayClass new: 1.
> array at: 1 put: ‘foo'.
> array at: 1. “—> should procude ‘foo’, but produces arbitrary strings”
>
interesting
>
> I can make it work with NBExternalAddress of course but I don’t want to if
> I can avoid it.
>
How would you use NBExternalAddress in this case?
>
> I’d appreciate it if someone (Nicolai?) could take a look at
> NBExternalArray>>emitRead / emitWrite and see if there’s an easy solution.
> Especially for strings I don’t think it should be too hard since all that’s
> needed is already present in the string handling facilities.
>
Somehow it only works half the way, either write the String / or read the
String.
this one:
arrayClass := NBExternalArray ofType: 'String'.
array := arrayClass new: 1.
array at: 1 put: 'foo'.
array at:1
reads the data back to a string object, but I think the data was written
wrong.
this one:
arrayClass := NBExternalArray ofType: 'char*'.
array := arrayClass new: 1.
array at: 1 put: 'foo'.
at least writes the right data, but now array at:1 contains an external
address and it is not automatically converted back to a string.
You can confirm that the data is written correctly by explicitly creating a
string from the external address.
(array at:1) readString -> 'foo'
Now, why is the String data written wrong in the first case?
(Maybe this has something to do with #pointerArity. I think
NBExternalString should have pointerArity 1.
I changed this for NBExternalString, but it seems this does not make a
difference - and may break other things).
It looks like some "double conversion" ST-String -> char*, that is, it
converts a String as NBExternalString
and uses this to do the conversion again:
I played it bit with the code (NB makes really fun, no irony, it really
makes fun, it is a nice piece of work).
and created a new NBExternalArray subclass StringArray:
NBExternalArray subclass: #StringArray
instanceVariableNames: ''
classVariableNames: ''
category: 'NativeBoost-Core-Objects'
define the class initialize method
initialize
self initElementType: #String
and overwrite emitWrite, the same code as in NBExternalArray, but replace
function: ' oop ( oop value , uint32 index , void * data , ' , self
class elementType , ' value )'
with
function: ' oop ( oop value , uint32 index , void * data , char*
value )'
now, this works:
arrayClass := StringArray.
array := arrayClass new: 1.
array at: 1 put: 'foo'.
(array at:1) -> 'foo'
So, maybe the default function prototype in NBExternalArray>>#emitWrite is
responsible for the double
conversion or the pointer arity.
I don't fully understand what is going on :), but maybe this helps.
nicolai
>
> Cheers,
> Max
>
