Hey Ian,
Thanks again for replying, however I'm a bit confused by the code you've
provided. am I passing the go callback into that function ?
I have few questions:
1- * I tried to do the do the following *
/*
#include <stdio.h>
#include <stdlib.h>
void parse(char* err, int status) {
// will get called by the go function
}
*/
import "C"
func SomeGoComputation(address string) {
_, err = // do some computation with address, maybe go over the
network
if (err != nil) {
C.parse(C.CString(err.Error()), C.int(0)) //<-- call the function
in the preamble
}
// I mean you get the gist
C.parse(C.CString(""),C.int(1))
}
//export C_compute
func C_compute(C.char* address) {
SomeGoComputation(C.GoString(address))
}
*However, when I builded the go code to a shared object this I get this
error *
/*
# command-line-arguments
duplicate symbol _aBlock in:
$WORK/command-line-arguments/_obj/_cgo_export.o
$WORK/command-line-arguments/_obj/mygo.cgo2.o
duplicate symbol _notification_parsing in:
$WORK/command-line-arguments/_obj/_cgo_export.o
$WORK/command-line-arguments/_obj/mygo.cgo2.o
ld: 2 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see
invocation)
*/
2 - *Do all functions added into the preamble get exported to the header
and the shared object that go build creates? *
Thanks
On Tuesday, December 19, 2017 at 10:35:49 PM UTC-5, Ian Lance Taylor wrote:
>
> On Tue, Dec 19, 2017 at 9:40 AM, <rou...@gmail.com <javascript:>> wrote:
> >
> > Thanks for your response, are you referring to something like this:
> > /*
> > #include <stdio.h>
> > #include <stdlib.h>
> >
> > void parse(char* err, int status) {
> > // do work
> > }
> > */
> >
> >
> >
> >
> > func Ccomputation(address *C.char) {
> >
> > ptr := uintptr(unsafe.Pointer(C.parse))
> >
> > 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)
> > // then free both e and c via unsafe pointer
> > ptr(e, c)
> > })
> > }
> >
>
> No, I mean write a C function like
>
> void callback(uintptr_t fn, char* err, int status) {
> pfn = (void (*)(char*, int))fn;
> pfn(err, status);
> }
>
> and write Go code like
> C.callback(callback, e, c)
>
> Ian
>
>
> > On Monday, December 18, 2017 at 10:03:47 PM UTC-5, rou...@gmail.com
> wrote:
> >>
> >> Hey guys,
> >>
> >> 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 .. :)
> >
> > --
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