Merge pull request #428 from blinklabs-io/feat/cbor-constructor

feat: direct marshal/unmarshal for cbor.Constructor

Author: agaffney

cbor/cbor.go

@@ -36,6 +36,14 @@ const (
 	CborTagRational = 30
 	CborTagSet      = 258
 	CborTagMap      = 259
+
+	// Tag ranges for "alternatives"
+	// https://www.ietf.org/archive/id/draft-bormann-cbor-notable-tags-07.html#name-enumerated-alternative-data
+	CborTagAlternative1Min = 121
+	CborTagAlternative1Max = 127
+	CborTagAlternative2Min = 1280
+	CborTagAlternative2Max = 1400
+	CborTagAlternative3    = 101
 )
 
 // Create an alias for RawMessage for convenience

cbor/value.go

@@ -73,35 +73,15 @@ func (v *Value) UnmarshalCBOR(data []byte) error {
 		case CborTagMap:
 			return v.processMap(tmpTag.Content)
 		default:
-			// Parse the tag value via our custom Value object to handle problem types
-			tmpValue := Value{}
-			if _, err := Decode(tmpTag.Content, &tmpValue); err != nil {
-				return err
-			}
-			// These tag numbers correspond to the Enumerated Alternative Data Items notable CBOR tags. These
-			// are often used in Plutus script datums
-			// https://www.ietf.org/archive/id/draft-bormann-cbor-notable-tags-07.html#name-enumerated-alternative-data
-			if tmpTag.Number >= 121 && tmpTag.Number <= 127 {
-				// Alternatives 0-6
-				v.value = Constructor{
-					constructor: uint(tmpTag.Number - 121),
-					value:       &tmpValue,
-				}
-			} else if tmpTag.Number >= 1280 && tmpTag.Number <= 1400 {
-				// Alternatives 7-127
-				v.value = Constructor{
-					constructor: uint(tmpTag.Number - 1280 + 7),
-					value:       &tmpValue,
-				}
-			} else if tmpTag.Number == 101 {
-				// Alternatives 128+
-				newValue := Value{
-					value: tmpValue.Value().([]interface{})[1],
-				}
-				v.value = Constructor{
-					constructor: tmpValue.Value().([]interface{})[0].(uint),
-					value:       &newValue,
+			if (tmpTag.Number >= CborTagAlternative1Min && tmpTag.Number <= CborTagAlternative1Max) ||
+				(tmpTag.Number >= CborTagAlternative2Min && tmpTag.Number <= CborTagAlternative2Max) ||
+				tmpTag.Number == CborTagAlternative3 {
+				// Constructors/alternatives
+				var tmpConstr Constructor
+				if _, err := Decode(data, &tmpConstr); err != nil {
+					return err
 				}
+				v.value = tmpConstr
 			} else {
 				// Fall back to standard CBOR tag parsing for our supported types
 				var tmpTagDecode interface{}
@@ -263,6 +243,18 @@ type Constructor struct {
 	value       *Value
 }
 
+func NewConstructor(constructor uint, value any) Constructor {
+	c := Constructor{
+		constructor: constructor,
+	}
+	if value != nil {
+		c.value = &Value{
+			value: value,
+		}
+	}
+	return c
+}
+
 func (v Constructor) Constructor() uint {
 	return v.constructor
 }
@@ -271,6 +263,63 @@ func (v Constructor) Fields() []any {
 	return v.value.Value().([]any)
 }
 
+func (c Constructor) FieldsCbor() []byte {
+	return c.value.Cbor()
+}
+
+func (c *Constructor) UnmarshalCBOR(data []byte) error {
+	// Parse as a raw tag to get number and nested CBOR data
+	tmpTag := RawTag{}
+	if _, err := Decode(data, &tmpTag); err != nil {
+		return err
+	}
+	// Parse the tag value via our custom Value object to handle problem types
+	tmpValue := Value{}
+	if _, err := Decode(tmpTag.Content, &tmpValue); err != nil {
+		return err
+	}
+	if tmpTag.Number >= CborTagAlternative1Min && tmpTag.Number <= CborTagAlternative1Max {
+		// Alternatives 0-6
+		c.constructor = uint(tmpTag.Number - CborTagAlternative1Min)
+		c.value = &tmpValue
+	} else if tmpTag.Number >= CborTagAlternative2Min && tmpTag.Number <= CborTagAlternative2Max {
+		// Alternatives 7-127
+		c.constructor = uint(tmpTag.Number - CborTagAlternative2Min + 7)
+		c.value = &tmpValue
+	} else if tmpTag.Number == CborTagAlternative3 {
+		// Alternatives 128+
+		tmpValues := tmpValue.Value().([]any)
+		c.constructor = uint(tmpValues[0].(uint64))
+		newValue := Value{
+			value: tmpValues[1],
+		}
+		c.value = &newValue
+	} else {
+		return fmt.Errorf("unsupported tag: %d", tmpTag.Number)
+	}
+	return nil
+}
+
+func (c Constructor) MarshalCBOR() ([]byte, error) {
+	var tmpTag Tag
+	if c.constructor <= 6 {
+		// Alternatives 0-6
+		tmpTag.Number = uint64(c.constructor + CborTagAlternative1Min)
+		tmpTag.Content = c.value.Value()
+	} else if c.constructor >= 7 && c.constructor <= 127 {
+		// Alternatives 7-127
+		tmpTag.Number = uint64(c.constructor + CborTagAlternative2Min - 7)
+		tmpTag.Content = c.value.Value()
+	} else if c.constructor >= 128 {
+		tmpTag.Number = CborTagAlternative3
+		tmpTag.Content = []any{
+			c.constructor,
+			c.value.Value(),
+		}
+	}
+	return Encode(&tmpTag)
+}
+
 func (v Constructor) MarshalJSON() ([]byte, error) {
 	tmpJson := fmt.Sprintf(`{"constructor":%d,"fields":[`, v.constructor)
 	tmpList := [][]byte{}

cbor/value_test.go

@@ -253,3 +253,77 @@ func TestLazyValueMarshalJSON(t *testing.T) {
 		}
 	}
 }
+
+var constructorTestDefs = []struct {
+	cborHex     string
+	expectedObj cbor.Constructor
+}{
+	{
+		// 122([1, 2, 3])
+		cborHex: "D87A83010203",
+		expectedObj: cbor.NewConstructor(
+			1,
+			[]any{uint64(1), uint64(2), uint64(3)},
+		),
+	},
+	{
+		// 1288([3, 4, 5])
+		cborHex: "D9050883030405",
+		expectedObj: cbor.NewConstructor(
+			15,
+			[]any{uint64(3), uint64(4), uint64(5)},
+		),
+	},
+	{
+		// 101([999, [6, 7]])
+		cborHex: "D865821903E7820607",
+		expectedObj: cbor.NewConstructor(
+			999,
+			[]any{uint64(6), uint64(7)},
+		),
+	},
+}
+
+func TestConstructorDecode(t *testing.T) {
+	for _, testDef := range constructorTestDefs {
+		cborData, err := hex.DecodeString(testDef.cborHex)
+		if err != nil {
+			t.Fatalf("failed to decode CBOR hex: %s", err)
+		}
+		var tmpConstr cbor.Constructor
+		if _, err := cbor.Decode(cborData, &tmpConstr); err != nil {
+			t.Fatalf("failed to decode CBOR data: %s", err)
+		}
+		if tmpConstr.Constructor() != testDef.expectedObj.Constructor() {
+			t.Fatalf(
+				"did not get expected constructor number, got %d, wanted %d",
+				tmpConstr.Constructor(),
+				testDef.expectedObj.Constructor(),
+			)
+		}
+		if !reflect.DeepEqual(tmpConstr.Fields(), testDef.expectedObj.Fields()) {
+			t.Fatalf(
+				"did not decode to expected fields\n  got: %#v\n  wanted: %#v",
+				tmpConstr.Fields(),
+				testDef.expectedObj.Fields(),
+			)
+		}
+	}
+}
+
+func TestConstructorEncode(t *testing.T) {
+	for _, testDef := range constructorTestDefs {
+		cborData, err := cbor.Encode(&testDef.expectedObj)
+		if err != nil {
+			t.Fatalf("failed to encode object to CBOR: %s", err)
+		}
+		cborDataHex := hex.EncodeToString(cborData)
+		if cborDataHex != strings.ToLower(testDef.cborHex) {
+			t.Fatalf(
+				"did not encode to expected CBOR\n  got: %s\n  wanted: %s",
+				cborDataHex,
+				strings.ToLower(testDef.cborHex),
+			)
+		}
+	}
+}