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Keep original reference of slice element #229

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merged 1 commit into from May 20, 2021
Merged

Keep original reference of slice element #229

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49 changes: 35 additions & 14 deletions decode_slice.go
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Expand Up @@ -49,9 +49,20 @@ func newSliceDecoder(dec decoder, elemType *rtype, size uintptr, structName, fie
}
}

func (d *sliceDecoder) newSlice() *sliceHeader {
func (d *sliceDecoder) newSlice(src *sliceHeader) *sliceHeader {
slice := d.arrayPool.Get().(*sliceHeader)
slice.len = 0
if src.len > 0 {
// copy original elem
if slice.cap < src.cap {
data := newArray(d.elemType, src.cap)
slice = &sliceHeader{data: data, len: src.len, cap: src.cap}
} else {
slice.len = src.len
}
copySlice(d.elemType, *slice, *src)
} else {
slice.len = 0
}
return slice
}

Expand Down Expand Up @@ -109,7 +120,8 @@ func (d *sliceDecoder) decodeStream(s *stream, depth int64, p unsafe.Pointer) er
return nil
}
idx := 0
slice := d.newSlice()
slice := d.newSlice((*sliceHeader)(p))
srcLen := slice.len
capacity := slice.cap
data := slice.data
for {
Expand All @@ -121,12 +133,17 @@ func (d *sliceDecoder) decodeStream(s *stream, depth int64, p unsafe.Pointer) er
copySlice(d.elemType, dst, src)
}
ep := unsafe.Pointer(uintptr(data) + uintptr(idx)*d.size)
if d.isElemPointerType {
**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
} else {
// assign new element to the slice
typedmemmove(d.elemType, ep, unsafe_New(d.elemType))

// if srcLen is greater than idx, keep the original reference
if srcLen <= idx {
if d.isElemPointerType {
**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
} else {
// assign new element to the slice
typedmemmove(d.elemType, ep, unsafe_New(d.elemType))
}
}

if err := d.valueDecoder.decodeStream(s, depth, ep); err != nil {
return err
}
Expand Down Expand Up @@ -212,7 +229,8 @@ func (d *sliceDecoder) decode(buf []byte, cursor, depth int64, p unsafe.Pointer)
return cursor, nil
}
idx := 0
slice := d.newSlice()
slice := d.newSlice((*sliceHeader)(p))
srcLen := slice.len
capacity := slice.cap
data := slice.data
for {
Expand All @@ -224,11 +242,14 @@ func (d *sliceDecoder) decode(buf []byte, cursor, depth int64, p unsafe.Pointer)
copySlice(d.elemType, dst, src)
}
ep := unsafe.Pointer(uintptr(data) + uintptr(idx)*d.size)
if d.isElemPointerType {
**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
} else {
// assign new element to the slice
typedmemmove(d.elemType, ep, unsafe_New(d.elemType))
// if srcLen is greater than idx, keep the original reference
if srcLen <= idx {
if d.isElemPointerType {
**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
} else {
// assign new element to the slice
typedmemmove(d.elemType, ep, unsafe_New(d.elemType))
}
}
c, err := d.valueDecoder.decode(buf, cursor, depth, ep)
if err != nil {
Expand Down
35 changes: 30 additions & 5 deletions decode_test.go
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Expand Up @@ -3052,7 +3052,7 @@ func TestMultipleDecodeWithRawMessage(t *testing.T) {
type intUnmarshaler int

func (u *intUnmarshaler) UnmarshalJSON(b []byte) error {
if *u != 0 {
if *u != 0 && *u != 10 {
return fmt.Errorf("failed to decode of slice with int unmarshaler")
}
*u = 10
Expand All @@ -3062,7 +3062,7 @@ func (u *intUnmarshaler) UnmarshalJSON(b []byte) error {
type arrayUnmarshaler [5]int

func (u *arrayUnmarshaler) UnmarshalJSON(b []byte) error {
if (*u)[0] != 0 {
if (*u)[0] != 0 && (*u)[0] != 10 {
return fmt.Errorf("failed to decode of slice with array unmarshaler")
}
(*u)[0] = 10
Expand All @@ -3072,22 +3072,24 @@ func (u *arrayUnmarshaler) UnmarshalJSON(b []byte) error {
type mapUnmarshaler map[string]int

func (u *mapUnmarshaler) UnmarshalJSON(b []byte) error {
if len(*u) != 0 {
if len(*u) != 0 && len(*u) != 1 {
return fmt.Errorf("failed to decode of slice with map unmarshaler")
}
*u = map[string]int{"a": 10}
return nil
}

type structUnmarshaler struct {
A int
A int
notFirst bool
}

func (u *structUnmarshaler) UnmarshalJSON(b []byte) error {
if u.A != 0 {
if !u.notFirst && u.A != 0 {
return fmt.Errorf("failed to decode of slice with struct unmarshaler")
}
u.A = 10
u.notFirst = true
return nil
}

Expand Down Expand Up @@ -3199,6 +3201,29 @@ func TestSliceElemUnmarshaler(t *testing.T) {
})
}

type keepRefTest struct {
A int
B string
}

func (t *keepRefTest) UnmarshalJSON(data []byte) error {
v := []interface{}{&t.A, &t.B}
return json.Unmarshal(data, &v)
}

func TestKeepReferenceSlice(t *testing.T) {
var v keepRefTest
if err := json.Unmarshal([]byte(`[54,"hello"]`), &v); err != nil {
t.Fatal(err)
}
if v.A != 54 {
t.Fatal("failed to keep reference for slice")
}
if v.B != "hello" {
t.Fatal("failed to keep reference for slice")
}
}

func TestInvalidTopLevelValue(t *testing.T) {
t.Run("invalid end of buffer", func(t *testing.T) {
var v struct{}
Expand Down