nmarley · March 31, 2025 22:32 · Jul 26, 2019 · Jul 26, 2019
diff --git a/README.md b/README.md
@@ -4,9 +4,13 @@ This is an example of Go code calling to a C++ library with a C wrapper.
 
 ## Build
 
+```sh
 go build  # this only ensures it compiles
+```
 
 
 ## Test
 
+```sh
 go test  # actually runs tests
+```
diff --git a/README.md b/README.md
@@ -0,0 +1,12 @@
+# Go / C++ bindings example
+
+This is an example of Go code calling to a C++ library with a C wrapper.
+
+## Build
+
+go build  # this only ensures it compiles
+
+
+## Test
+
+go test  # actually runs tests
diff --git a/num.cpp b/num.cpp
@@ -0,0 +1,23 @@
+// num.cpp
+#include "nummer.hpp"
+#include "num.h"
+
+Num NumInit() {
+    cxxNum * ret = new cxxNum(1);
+    return (void*)ret;
+}
+
+void NumFree(Num n) {
+    cxxNum * num = (cxxNum*)n;
+    delete num;
+}
+
+void NumIncrement(Num n) {
+    cxxNum * num = (cxxNum*)n;
+    num->Increment();
+}
+
+int NumGetValue(Num n) {
+    cxxNum * num = (cxxNum*)n;
+    return num->GetValue();
+}
diff --git a/num.go b/num.go
@@ -0,0 +1,26 @@
+package num
+
+// #cgo LDFLAGS: -L. -lstdc++
+// #cgo CXXFLAGS: -std=c++14 -I.
+// #include "num.h"
+import "C"
+import "unsafe"
+
+type GoNum struct {
+	num C.Num
+}
+
+func New() GoNum {
+	var ret GoNum
+	ret.num = C.NumInit()
+	return ret
+}
+func (n GoNum) Free() {
+	C.NumFree((C.Num)(unsafe.Pointer(n.num)))
+}
+func (n GoNum) Inc() {
+	C.NumIncrement((C.Num)(unsafe.Pointer(n.num)))
+}
+func (n GoNum) GetValue() int {
+	return int(C.NumGetValue((C.Num)(unsafe.Pointer(n.num))))
+}
diff --git a/num.h b/num.h
@@ -0,0 +1,14 @@
+// num.h
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef void* Num;
+Num NumInit(void);
+void NumFree(Num);
+void NumIncrement(Num);
+int NumGetValue(Num);
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/num_test.go b/num_test.go
@@ -0,0 +1,27 @@
+package num
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestNum(t *testing.T) {
+	num := New()
+	num.Inc()
+	if num.GetValue() != 2 {
+		t.Error("unexpected value received")
+	}
+	num.Inc()
+	num.Inc()
+	num.Inc()
+	if num.GetValue() != 5 {
+		t.Error("unexpected value received")
+	}
+	value := num.GetValue()
+	num.Free()
+
+	typ := reflect.TypeOf(value)
+	if typ.Name() != "int" {
+		t.Error("got unexpected type")
+	}
+}
diff --git a/nummer.cpp b/nummer.cpp
@@ -0,0 +1,10 @@
+#include <iostream>
+#include "nummer.hpp"
+
+void cxxNum::Increment(void) {
+    this->value++;
+}
+
+int cxxNum::GetValue(void) {
+    return this->value;
+}
diff --git a/nummer.hpp b/nummer.hpp
@@ -0,0 +1,10 @@
+class cxxNum {
+private:
+    int value;
+
+public:
+    cxxNum(int _num):value(_num){};
+    ~cxxNum(){};
+    void Increment(void);
+    int GetValue(void);
+};
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