Use typedmemmove for copying element of slice

decode_slice.go

@@ -67,6 +67,12 @@ func copySlice(elemType *rtype, dst, src sliceHeader) int
 //go:linkname newArray reflect.unsafe_NewArray
 func newArray(*rtype, int) unsafe.Pointer
 
+//go:linkname typedmemmovepartial reflect.typedmemmovepartial
+func typedmemmovepartial(typ *rtype, dst, src unsafe.Pointer, off, size uintptr)
+
+//go:linkname typedmemmove reflect.typedmemmove
+func typedmemmove(t *rtype, dst, src unsafe.Pointer)
+
 func (d *sliceDecoder) errNumber(offset int64) *UnmarshalTypeError {
 	return &UnmarshalTypeError{
 		Value:  "number",
@@ -120,12 +126,8 @@ func (d *sliceDecoder) decodeStream(s *stream, depth int64, p unsafe.Pointer) er
 				}
 				ep := unsafe.Pointer(uintptr(data) + uintptr(idx)*d.size)
 				if d.isElemUnmarshalJSONType {
-					receiver := unsafe_New(d.elemType)
+					// assign new element to the slice
-					if d.elemType.Kind() == reflect.Slice {
+					typedmemmove(d.elemType, ep, unsafe_New(d.elemType))
-						**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = receiver
-					} else {
-						**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = **(**unsafe.Pointer)(unsafe.Pointer(&receiver))
-					}
 				} else if d.isElemPointerType {
 					**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
 				}
@@ -241,12 +243,8 @@ func (d *sliceDecoder) decode(buf []byte, cursor, depth int64, p unsafe.Pointer)
 				}
 				ep := unsafe.Pointer(uintptr(data) + uintptr(idx)*d.size)
 				if d.isElemUnmarshalJSONType {
-					receiver := unsafe_New(d.elemType)
+					// assign new element to the slice
-					if d.elemType.Kind() == reflect.Slice {
+					typedmemmove(d.elemType, ep, unsafe_New(d.elemType))
-						**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = receiver
-					} else {
-						**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = **(**unsafe.Pointer)(unsafe.Pointer(&receiver))
-					}
 				} else if d.isElemPointerType {
 					**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
 				}

decode_test.go

@@ -2996,6 +2996,53 @@ func TestDecodeMultipleUnmarshal(t *testing.T) {
 	})
 }
 
+func TestMultipleDecodeWithRawMessage(t *testing.T) {
+	original := []byte(`{
+		"Body": {
+			"List": [
+				{
+					"Returns": [
+						{
+							"Value": "10",
+							"nodeType": "Literal"
+						}
+					],
+					"nodeKind": "Return",
+					"nodeType": "Statement"
+				}
+			],
+			"nodeKind": "Block",
+			"nodeType": "Statement"
+		},
+		"nodeType": "Function"
+	}`)
+
+	var a map[string]json.RawMessage
+	if err := json.Unmarshal(original, &a); err != nil {
+		t.Fatal(err)
+	}
+	var b map[string]json.RawMessage
+	if err := json.Unmarshal(a["Body"], &b); err != nil {
+		t.Fatal(err)
+	}
+	var c []json.RawMessage
+	if err := json.Unmarshal(b["List"], &c); err != nil {
+		t.Fatal(err)
+	}
+	var d map[string]json.RawMessage
+	if err := json.Unmarshal(c[0], &d); err != nil {
+		t.Fatal(err)
+	}
+	var e []json.RawMessage
+	if err := json.Unmarshal(d["Returns"], &e); err != nil {
+		t.Fatal(err)
+	}
+	var f map[string]json.RawMessage
+	if err := json.Unmarshal(e[0], &f); err != nil {
+		t.Fatal(err)
+	}
+}
+
 type intUnmarshaler int
 
 func (u *intUnmarshaler) UnmarshalJSON(b []byte) error {