Merge pull request #283 from goccy/feature/fix-282

Fix mapassign_faststr for indirect struct type

decode_test.go

@@ -3732,3 +3732,47 @@ func TestDecodeBinaryTypeWithEscapedChar(t *testing.T) {
 		}
 	})
 }
+
+func TestIssue282(t *testing.T) {
+	var J = []byte(`{
+  "a": {},
+  "b": {},
+  "c": {},
+  "d": {},
+  "e": {},
+  "f": {},
+  "g": {},
+  "h": {
+    "m": "1"
+  },
+  "i": {}
+}`)
+
+	type T4 struct {
+		F0 string
+		F1 string
+		F2 string
+		F3 string
+		F4 string
+		F5 string
+		F6 int
+	}
+	type T3 struct {
+		F0 string
+		F1 T4
+	}
+	type T2 struct {
+		F0 string `json:"m"`
+		F1 T3
+	}
+	type T0 map[string]T2
+
+	// T2 size is 136 bytes. This is indirect type.
+	var v T0
+	if err := json.Unmarshal(J, &v); err != nil {
+		t.Fatal(err)
+	}
+	if v["h"].F0 != "1" {
+		t.Fatalf("failed to assign map value")
+	}
+}

internal/decoder/map.go

@@ -12,7 +12,7 @@ type mapDecoder struct {
 	mapType                 *runtime.Type
 	keyType                 *runtime.Type
 	valueType               *runtime.Type
-	stringKeyType bool
+	canUseAssignFaststrType bool
 	keyDecoder              Decoder
 	valueDecoder            Decoder
 	structName              string
@@ -24,7 +24,7 @@ func newMapDecoder(mapType *runtime.Type, keyType *runtime.Type, keyDec Decoder,
 		mapType:                 mapType,
 		keyDecoder:              keyDec,
 		keyType:                 keyType,
-		stringKeyType: keyType.Kind() == reflect.String,
+		canUseAssignFaststrType: canUseAssignFaststrType(keyType, valueType),
 		valueType:               valueType,
 		valueDecoder:            valueDec,
 		structName:              structName,
@@ -32,6 +32,19 @@ func newMapDecoder(mapType *runtime.Type, keyType *runtime.Type, keyDec Decoder,
 	}
 }
 
+const (
+	mapMaxElemSize = 128
+)
+
+// See detail: https://github.com/goccy/go-json/pull/283
+func canUseAssignFaststrType(key *runtime.Type, value *runtime.Type) bool {
+	indirectElem := value.Size() > mapMaxElemSize
+	if indirectElem {
+		return false
+	}
+	return key.Kind() == reflect.String
+}
+
 //go:linkname makemap reflect.makemap
 func makemap(*runtime.Type, int) unsafe.Pointer
 
@@ -45,8 +58,8 @@ func mapassign_faststr(t *runtime.Type, m unsafe.Pointer, s string) unsafe.Point
 func mapassign(t *runtime.Type, m unsafe.Pointer, k, v unsafe.Pointer)
 
 func (d *mapDecoder) mapassign(t *runtime.Type, m, k, v unsafe.Pointer) {
-	if d.stringKeyType {
+	if d.canUseAssignFaststrType {
-		mapV := mapassign_faststr(d.mapType, m, *(*string)(k))
+		mapV := mapassign_faststr(t, m, *(*string)(k))
 		typedmemmove(d.valueType, mapV, v)
 	} else {
 		mapassign(t, m, k, v)