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Add decoding option for return type of data with an unknown tag
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Adds a decoding option to specify the preferred return type when unmarshalling a data with an unknown tag.
If this option is not set, Unmarshal returns a value of type Tag{}. This ensures backward compatibility.
If the option is set, Unmarshal returns the unmarshalled content.

Signed-off-by: Suriyan Subbarayan [email protected]
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@ssuriyan7
ssuriyan7 committed Jan 25, 2024
1 parent e5eaf7a commit bc12130
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Showing 2 changed files with 146 additions and 51 deletions.
131 changes: 80 additions & 51 deletions decode.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -446,6 +446,23 @@ func (fnbsm FieldNameByteStringMode) valid() bool {
return fnbsm >= 0 && fnbsm < maxFieldNameByteStringMode
}

// ReturnTypeForEmptyInterface specifies the type of the value to be returned when decoding into an empty interface
type ReturnTypeForEmptyInterface int

const (
// ReturnTagForEmptyInterface returns a value of type Tag
ReturnTagForEmptyInterface ReturnTypeForEmptyInterface = iota

// ReturnTagContentForEmptyInterface returns only the content of the Tag
ReturnTagContentForEmptyInterface

maxReturnTypesForEmptyInterface
)

func (rtfei ReturnTypeForEmptyInterface) valid() bool {
return rtfei >= 0 && rtfei < maxReturnTypesForEmptyInterface
}

// DecOptions specifies decoding options.
type DecOptions struct {
// DupMapKey specifies whether to enforce duplicate map key.
Expand Down Expand Up @@ -514,6 +531,9 @@ type DecOptions struct {
// FieldNameByteString specifies the behavior when decoding a CBOR byte string map key as a
// Go struct field name.
FieldNameByteString FieldNameByteStringMode

// ReturnTypeForEmptyIface specifies the type of the value to be returned when decoding into an empty interface
ReturnTypeForEmptyIface ReturnTypeForEmptyInterface
}

// DecMode returns DecMode with immutable options and no tags (safe for concurrency).
Expand Down Expand Up @@ -637,24 +657,28 @@ func (opts DecOptions) decMode() (*decMode, error) {
if !opts.FieldNameByteString.valid() {
return nil, errors.New("cbor: invalid FieldNameByteString " + strconv.Itoa(int(opts.FieldNameByteString)))
}
if !opts.ReturnTypeForEmptyIface.valid() {
return nil, errors.New("cbor: invalid ReturnTypeForEmptyIface " + strconv.Itoa(int(opts.ReturnTypeForEmptyIface)))
}
dm := decMode{
dupMapKey: opts.DupMapKey,
timeTag: opts.TimeTag,
maxNestedLevels: opts.MaxNestedLevels,
maxArrayElements: opts.MaxArrayElements,
maxMapPairs: opts.MaxMapPairs,
indefLength: opts.IndefLength,
tagsMd: opts.TagsMd,
intDec: opts.IntDec,
mapKeyByteString: opts.MapKeyByteString,
extraReturnErrors: opts.ExtraReturnErrors,
defaultMapType: opts.DefaultMapType,
utf8: opts.UTF8,
fieldNameMatching: opts.FieldNameMatching,
bigIntDec: opts.BigIntDec,
defaultByteStringType: opts.DefaultByteStringType,
byteStringToString: opts.ByteStringToString,
fieldNameByteString: opts.FieldNameByteString,
dupMapKey: opts.DupMapKey,
timeTag: opts.TimeTag,
maxNestedLevels: opts.MaxNestedLevels,
maxArrayElements: opts.MaxArrayElements,
maxMapPairs: opts.MaxMapPairs,
indefLength: opts.IndefLength,
tagsMd: opts.TagsMd,
intDec: opts.IntDec,
mapKeyByteString: opts.MapKeyByteString,
extraReturnErrors: opts.ExtraReturnErrors,
defaultMapType: opts.DefaultMapType,
utf8: opts.UTF8,
fieldNameMatching: opts.FieldNameMatching,
bigIntDec: opts.BigIntDec,
defaultByteStringType: opts.DefaultByteStringType,
byteStringToString: opts.ByteStringToString,
fieldNameByteString: opts.FieldNameByteString,
returnTypeForEmptyIface: opts.ReturnTypeForEmptyIface,
}
return &dm, nil
}
Expand Down Expand Up @@ -706,47 +730,49 @@ type DecMode interface {
}

type decMode struct {
tags tagProvider
dupMapKey DupMapKeyMode
timeTag DecTagMode
maxNestedLevels int
maxArrayElements int
maxMapPairs int
indefLength IndefLengthMode
tagsMd TagsMode
intDec IntDecMode
mapKeyByteString MapKeyByteStringMode
extraReturnErrors ExtraDecErrorCond
defaultMapType reflect.Type
utf8 UTF8Mode
fieldNameMatching FieldNameMatchingMode
bigIntDec BigIntDecMode
defaultByteStringType reflect.Type
byteStringToString ByteStringToStringMode
fieldNameByteString FieldNameByteStringMode
tags tagProvider
dupMapKey DupMapKeyMode
timeTag DecTagMode
maxNestedLevels int
maxArrayElements int
maxMapPairs int
indefLength IndefLengthMode
tagsMd TagsMode
intDec IntDecMode
mapKeyByteString MapKeyByteStringMode
extraReturnErrors ExtraDecErrorCond
defaultMapType reflect.Type
utf8 UTF8Mode
fieldNameMatching FieldNameMatchingMode
bigIntDec BigIntDecMode
defaultByteStringType reflect.Type
byteStringToString ByteStringToStringMode
fieldNameByteString FieldNameByteStringMode
returnTypeForEmptyIface ReturnTypeForEmptyInterface
}

var defaultDecMode, _ = DecOptions{}.decMode()

// DecOptions returns user specified options used to create this DecMode.
func (dm *decMode) DecOptions() DecOptions {
return DecOptions{
DupMapKey: dm.dupMapKey,
TimeTag: dm.timeTag,
MaxNestedLevels: dm.maxNestedLevels,
MaxArrayElements: dm.maxArrayElements,
MaxMapPairs: dm.maxMapPairs,
IndefLength: dm.indefLength,
TagsMd: dm.tagsMd,
IntDec: dm.intDec,
MapKeyByteString: dm.mapKeyByteString,
ExtraReturnErrors: dm.extraReturnErrors,
UTF8: dm.utf8,
FieldNameMatching: dm.fieldNameMatching,
BigIntDec: dm.bigIntDec,
DefaultByteStringType: dm.defaultByteStringType,
ByteStringToString: dm.byteStringToString,
FieldNameByteString: dm.fieldNameByteString,
DupMapKey: dm.dupMapKey,
TimeTag: dm.timeTag,
MaxNestedLevels: dm.maxNestedLevels,
MaxArrayElements: dm.maxArrayElements,
MaxMapPairs: dm.maxMapPairs,
IndefLength: dm.indefLength,
TagsMd: dm.tagsMd,
IntDec: dm.intDec,
MapKeyByteString: dm.mapKeyByteString,
ExtraReturnErrors: dm.extraReturnErrors,
UTF8: dm.utf8,
FieldNameMatching: dm.fieldNameMatching,
BigIntDec: dm.bigIntDec,
DefaultByteStringType: dm.defaultByteStringType,
ByteStringToString: dm.byteStringToString,
FieldNameByteString: dm.fieldNameByteString,
ReturnTypeForEmptyIface: dm.returnTypeForEmptyIface,
}
}

Expand Down Expand Up @@ -1426,6 +1452,9 @@ func (d *decoder) parse(skipSelfDescribedTag bool) (interface{}, error) { //noli
if err != nil {
return nil, err
}
if d.dm.returnTypeForEmptyIface == ReturnTagContentForEmptyInterface {
return content, nil
}
return Tag{tagNum, content}, nil
case cborTypePrimitives:
_, ai, val := d.getHead()
Expand Down
66 changes: 66 additions & 0 deletions decode_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8366,6 +8366,72 @@ func TestUnmarshalFieldNameByteString(t *testing.T) {
}
}

func TestDecModeInvalidReturnTypeForEmptyInterface(t *testing.T) {
for _, tc := range []struct {
name string
opts DecOptions
wantErrorMsg string
}{
{
name: "below range of valid modes",
opts: DecOptions{ReturnTypeForEmptyIface: -1},
wantErrorMsg: "cbor: invalid ReturnTypeForEmptyIface -1",
},
{
name: "above range of valid modes",
opts: DecOptions{ReturnTypeForEmptyIface: 101},
wantErrorMsg: "cbor: invalid ReturnTypeForEmptyIface 101",
},
} {
t.Run(tc.name, func(t *testing.T) {
_, err := tc.opts.DecMode()
if err == nil {
t.Errorf("DecMode() didn't return an error")
} else if err.Error() != tc.wantErrorMsg {
t.Errorf("DecMode() returned error %q, want %q", err.Error(), tc.wantErrorMsg)
}
})
}
}

func TestUnmarshalTaggedDataToEmptyInterfaceWithReturnType(t *testing.T) {
for _, tc := range []struct {
name string
opts DecOptions
in []byte
want interface{}
}{
{
name: "default to value of type Tag",
opts: DecOptions{},
in: hexDecode("d8ff00"),
want: Tag{},
},
{
name: "Tag's content",
opts: DecOptions{ReturnTypeForEmptyIface: ReturnTagContentForEmptyInterface},
in: hexDecode("d8ff00"),
want: uint64(0),
},
} {
t.Run(tc.name, func(t *testing.T) {
dm, err := tc.opts.DecMode()
if err != nil {
t.Fatal(err)
}

var got interface{}
if err := dm.Unmarshal(tc.in, &got); err != nil {
t.Errorf("unexpected error: %v", err)
}

if reflect.TypeOf(tc.want) != reflect.TypeOf(got) {
t.Errorf("got %s, want %s", reflect.TypeOf(got), reflect.TypeOf(tc.want))
}
})
}
}

func isCBORNil(data []byte) bool {
return len(data) > 0 && (data[0] == 0xf6 || data[0] == 0xf7)
}

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