c/ffi: add _demo

c/ffi/_demo/gofunc/main.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"unsafe"
+
+	"github.com/goplus/llgo/c/ffi"
+)
+
+type array struct {
+	x int
+	y int
+	z int
+	k int
+}
+
+type Func func(ar array, i interface{}, s string, slice []int) (int, float64)
+
+func demo(p1 array, p2 interface{}, p3 string, p4 []int) (int, float64) {
+	println(p1.x, p1.y, p1.z, p1.k)
+	println(p2)
+	println(p3)
+	println(p4)
+	for _, v := range p4 {
+		println(v)
+	}
+	return 200, 3.14
+}
+
+func main() {
+	sig, err := ffi.NewSignature(ffi.StructOf(ffi.TypeInt, ffi.TypeFloat64),
+		ffi.StructOf(ffi.TypeInt, ffi.TypeInt, ffi.TypeInt, ffi.TypeInt),
+		ffi.TypeInterface, ffi.TypeString, ffi.TypeSlice)
+	if err != nil {
+		panic(err)
+	}
+	fn := demo
+	closure := ffi.NewClosure()
+	defer closure.Free()
+	err = closure.Bind(sig, func(cif *ffi.Signature, ret unsafe.Pointer, args *unsafe.Pointer, userdata unsafe.Pointer) {
+		p1 := *(*array)(ffi.Index(args, 0))
+		p2 := *(*any)(ffi.Index(args, 1))
+		p3 := *(*string)(ffi.Index(args, 2))
+		p4 := *(*[]int)(ffi.Index(args, 3))
+		fn := *(*Func)(userdata)
+		p := (*struct {
+			i int
+			f float64
+		})(ret)
+		p.i, p.f = fn(p1, p2, p3, p4)
+	}, unsafe.Pointer(&fn))
+	var ret struct {
+		i int
+		f float64
+	}
+	p1 := array{1, 2, 3, 4}
+	var p2 any = 100
+	p3 := "hello world"
+	p4 := []int{100, 200, 300}
+	ffi.Call(sig, closure.Fn, unsafe.Pointer(&ret),
+		unsafe.Pointer(&p1), unsafe.Pointer(&p2), unsafe.Pointer(&p3), unsafe.Pointer(&p4))
+	println("ret:", ret.i, ret.f)
+}