commit 14e763c65a199689920030cc77b09ea16b6079ce
Author: Victor Timofei <victor@vtimothy.com>
Date:   Fri Jul 29 21:45:20 2022 +0300

    Initial commit

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..710e463
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+cgo-callback
+mylib.o
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..90d8c2c
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,13 @@
+GO=go
+
+.PHONY: all
+all: cgo-callback
+
+mylib.o: mylib.c
+
+cgo-callback: mylib.o mylib.h
+	$(GO) build
+
+.PHONY: clean
+clean:
+	rm -f mylib.o cgo-callback
diff --git a/cfuncs.go b/cfuncs.go
new file mode 100644
index 0000000..da794e7
--- /dev/null
+++ b/cfuncs.go
@@ -0,0 +1,13 @@
+package main
+
+/*
+#include <stdio.h>
+
+void callOnMeGo_cgo(int n)
+{
+  printf("callOnMeGo_cgo called\n");
+  void callOnMeGo(int);
+  callOnMeGo(n);
+}
+*/
+import "C"
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..f97c023
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.vtimothy.com/vtimofei/cgo-callback
+
+go 1.18
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..0c4eea4
--- /dev/null
+++ b/main.go
@@ -0,0 +1,45 @@
+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
+var 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)
+}
diff --git a/mylib.c b/mylib.c
new file mode 100644
index 0000000..e00bb2e
--- /dev/null
+++ b/mylib.c
@@ -0,0 +1,6 @@
+#include "mylib.h"
+
+void use_printer(printer_t p)
+{
+  p(14);
+}
diff --git a/mylib.h b/mylib.h
new file mode 100644
index 0000000..d767883
--- /dev/null
+++ b/mylib.h
@@ -0,0 +1,8 @@
+#ifndef MYLIB_H
+#define MYLIB_H 1
+
+typedef void (*printer_t)(int);
+
+void use_printer(printer_t);
+
+#endif