On Mon, Dec 18, 2017 at 5:31 AM, <roup...@gmail.com> wrote:
>
> I want to write a c wrapper around a go code that has a callback
>
> func SomeGoComputation(address string, callback func(string,int)) {
> _, err = // do some computation with address, maybe go over the
> network
> if (err != nil) {
> callback(err.Error(), 0)
> }
> // I mean you get the gist
> callback("",1)
> }
>
> I've having trouble writing the callback signature which in c would be
> void(*c_callback)(*char, int)
>
> //export Ccomputation
> func Ccomputation(address *C.char, // how to write that callback) {
> SomeGoComputation(C.GoString(address), func(errString string, code int){
> //passing the go callback values to the c callback wrapper
> e := C.CString(errString)
> c := C.int(code)
> c_callback(e, c)
> // then free both e and c via unsafe pointer
> })
> }
>
>
> I look around and some (articles or not related answer from go posts) say to
> use an interface, so I did try `(C.char*, C.int)interface {}` but I did get
> an error missing , at line where the callback was declared in the wrapper.
>
> Any ideas, all advice are welcome thanks .. :)
As the docs say at https://golang.org/cmd/cgo, calling C function
pointers is not supported. You need some other mechanism. The
simplest is a C function that will call the C function pointer for
you. Give the function pointer a type uintptr in Go. Accept it from
C, and pass it to a C function that does the actual call.
Ian
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