On Mon, Feb 15, 2021 at 12:39 PM changkun <h...@changkun.de> wrote:
>
> Thanks for the hint, but I have some follow-up questions:
>
>>
>> Even if there were a way to do this, an atomic variable is not a good
>> synchronization mechanism, because the other side has to poll the
>> variable.
>
> Indeed, it the other side will be a spin loop to poll the atomic variable,
> which ...
>
>
>>
>> You can do this as a last resort, but it doesn't sound like
>> you are at a last resort here. I suggest that you have your C
>> function call a Go function to write a value on a channel.
>
> seems easy to write than this (?).
>
> Say a Go function foo is called from the C side, to be able to send to the
> corresponding channel, C must pass that channel to the Go function, which
> brings to the initial question: pass a channel from Go to C, is it supported
> at the moment (?)
>
> How could a Go function be able to send content to differently allocated
> channels in correspondingly invoked C functions?
For example, on the Go side write
type chanToUse struct {
c chan int
}
//export MyGoFunction
func MyGoFunction(u unsafe.Pointer, val int) {
cu = (*chanToUse)(u)
cu.c <- val
}
ch := make(chan int)
...
C.MyCFunction(unsafe.Pointer(&chanToUse{ch}))
and on the C side write
void MyCFunction(void *goData) {
...
MyGoFunction(goData, 0);
}
Yes, it's more work. But it's not a good idea to poll an atomic
variable in Go. The Go scheduler reacts badly to busy loops.
Ian
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