Thanks for the fast answer. :-)
On 30/05/16 11:14, Esteban Lorenzano wrote:
this is not the easiest part of FFI :)
this is the simplest way:
str := ExternalAddress new. “This will point to NULL”
self callToMyFunction: str.
pharoString := (str pointerAt: 1) readString.
callToMyFunction: str
self ffiCall: #( void function ( char ** str ) )
now, another way is to declare a value holder:
1) subclass FFIExternalValueHolder.
FFIExternalValueHolder subclass: #StringValueHolder.
2) implement class side method typeDesc
StringValueHolder class>>typeDesc
^ String
3) implement your method replacing char** for your value holder:
callToMyFunction: str
self ffiCall: #( void function ( StringValueHolder* str ) )
then you call like this:
str := StringValueHolder new.
self callToMyFunction: str.
pharoString := str value readString.
looks like too much steps for just economise the “pointeAt: 1” part, but is
useful when you have lots of this calls :)
I think I will use the second solution. It is cleaner isn't it?
Julien
