add hack for nocopy for string <-> slice

hack/hack.go

@@ -0,0 +1,27 @@
+package hack
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// no copy to change slice to string
+// use your own risk
+func String(b []byte) (s string) {
+	pbytes := (*reflect.SliceHeader)(unsafe.Pointer(&b))
+	pstring := (*reflect.StringHeader)(unsafe.Pointer(&s))
+	pstring.Data = pbytes.Data
+	pstring.Len = pbytes.Len
+	return
+}
+
+// no copy to change string to slice
+// use your own risk
+func Slice(s string) (b []byte) {
+	pbytes := (*reflect.SliceHeader)(unsafe.Pointer(&b))
+	pstring := (*reflect.StringHeader)(unsafe.Pointer(&s))
+	pbytes.Data = pstring.Data
+	pbytes.Len = pstring.Len
+	pbytes.Cap = pstring.Len
+	return
+}

hack/hack_test.go

@@ -0,0 +1,36 @@
+package hack
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestString(t *testing.T) {
+	b := []byte("hello world")
+	a := String(b)
+
+	if a != "hello world" {
+		t.Fatal(a)
+	}
+
+	b[0] = 'a'
+
+	if a != "aello world" {
+		t.Fatal(a)
+	}
+
+	b = append(b, "abc"...)
+	if a != "aello world" {
+		t.Fatal(a)
+	}
+}
+
+func TestByte(t *testing.T) {
+	a := "hello world"
+
+	b := Slice(a)
+
+	if !bytes.Equal(b, []byte("hello world")) {
+		t.Fatal(string(b))
+	}
+}