cgo-callback/main.go

package main

import (
	"fmt"
	"sync"
	"unsafe"
)

/*
#cgo CFLAGS: -I .
#cgo LDFLAGS: -L .

#include "mylib.h"

void callOnMeGo_cgo(int n);
*/
import "C"

//export callOnMeGo
func callOnMeGo(n int) {
	printerCallback(n)
}

type Printer func(int)

var (
	printerCallback     Printer
	printerCallbackLock sync.RWMutex
)

func usePrinter(p Printer) {
	printerCallbackLock.Lock()
	printerCallback = p
	C.use_printer((C.printer_t)(unsafe.Pointer(C.callOnMeGo_cgo)))
	printerCallback = nil
	printerCallbackLock.Unlock()
}

var myPrinter Printer = Printer(func(n int) {
	for i := 0; i < n; i++ {
		fmt.Printf("%d\n", i)
	}
})

func main() {
	usePrinter(myPrinter)
}