Allocate memory via C.malloc

Signed-off-by: Hiroshi Hatake <[email protected]>

Author: cosmo0920

examples/in_gdummy/in_gdummy.go

@@ -1,15 +1,29 @@
 package main
 
+/*
+#include <stdlib.h>
+*/
 import "C"
 import (
 	"fmt"
 	"time"
 	"reflect"
+	"runtime"
 	"unsafe"
 
 	"github.com/fluent/fluent-bit-go/input"
 )
 
+type Slice struct {
+	Data []byte
+	data *c_slice_t
+}
+
+type c_slice_t struct {
+	p unsafe.Pointer
+	n int
+}
+
 //export FLBPluginRegister
 func FLBPluginRegister(def unsafe.Pointer) int {
 	return input.FLBPluginRegister(def, "gdummy", "dummy GO!")
@@ -25,19 +39,28 @@ func FLBPluginInit(plugin unsafe.Pointer) int {
 	return input.FLB_OK
 }
 
-func MakePayload(packed []byte) (**C.void, int) {
-	var payload **C.void
+func alloc(size int) unsafe.Pointer {
+	return C.calloc(C.size_t(size), 1)
+}
+
+func makeSlice(p unsafe.Pointer, n int) *Slice {
+	data := &c_slice_t{p, n}
 
-	length := len(packed)
-	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&payload))
-	hdr.Data = uintptr(unsafe.Pointer(&packed))
-	hdr.Len = length
+	runtime.SetFinalizer(data, func(data *c_slice_t){
+		C.free(data.p)
+	})
+
+	s := &Slice{data: data}
+	h := (*reflect.SliceHeader)(unsafe.Pointer(&s.Data))
+	h.Data = uintptr(p)
+	h.Len = n
+	h.Cap = n
 
-	return payload, length
+	return s
 }
 
 //export FLBPluginInputCallback
-func FLBPluginInputCallback(data **C.void, size *C.size_t) int {
+func FLBPluginInputCallback(data *unsafe.Pointer, size *C.size_t) int {
 	now := time.Now()
 	flb_time := input.FLBTime{now}
 	message := map[string]string{"message": "dummy"}
@@ -51,9 +74,11 @@ func FLBPluginInputCallback(data **C.void, size *C.size_t) int {
 		return input.FLB_ERROR
 	}
 
-	payload, length := MakePayload(packed)
-
-	*data = *payload
+	length := len(packed)
+	p := alloc(length)
+	s := makeSlice(p, length)
+	copy(s.Data, packed)
+	*data = unsafe.Pointer(&s.Data[0])
 	*size = C.size_t(length)
 	// For emitting interval adjustment.
 	time.Sleep(1000 * time.Millisecond)