generate: Add Any type to parser and syntax tree

Reviewed-on: #3

design/pdl-language.md

@@ -30,6 +30,7 @@ PDL allows defining a protocol using HOPP and TAPE.
 | []\<TYPE\> | OTA     |  * | Array of any type[^1]
 | Table      | KTV     |  * | Table with undefined schema
 | {...}      | KTV     |  * | Table with defined schema
+| Any        | *       |  * | Value of an undefined type
 
 [^1]: Excluding SI and SBA. I5 and U5 cannot be used in an array, but String and
 Buffer are simply forced to use their "long" variant.

generate/generate.go

@@ -627,7 +627,7 @@ func (this *Generator) generateDecodeValue(typ Type, typeName, valueSource, tagS
 	case TypeTable:
 		// KTV: <length: UN> (<key: U16> <tag: Tag> <value>)*
 		nn, err := this.iprintf(
-			"nn, err = tape.DecodeAny(decoder, %s, %s)\n",
+			"nn, err = tape.DecodeAnyInto(decoder, %s, %s)\n",
 			valueSource, tagSource)
 		n += nn; if err != nil { return n, err }
 		nn, err = this.generateErrorCheck()

generate/parse.go

@@ -116,6 +116,7 @@ func (this *parser) parseType() (Type, error) {
 		case "String": return TypeString { }, this.Next()
 		case "Buffer": return TypeBuffer { }, this.Next()
 		case "Table":  return TypeTable { }, this.Next()
+		case "Any":    return TypeAny { }, this.Next()
 		}
 		return this.parseTypeNamed()
 	case TokenLBracket:

generate/parse_test.go

@@ -31,6 +31,7 @@ func TestParse(test *testing.T) {
 			0x0002: Field { Name: "Followers", Type: TypeInt { Bits: 32 } },
 		},
 	}
+	correct.Types["Anything"] = TypeAny { }
 	test.Log("CORRECT:", &correct)
 	
 	got, err := ParseReader("test.pdl", strings.NewReader(`
@@ -48,6 +49,8 @@ func TestParse(test *testing.T) {
 		0001 Bio       String,
 		0002 Followers U32,
 	}
+
+	Anything Any
 	`))
 	if err != nil { test.Fatal(parse.Format(err)) }
 	test.Log("GOT:    ", got)

generate/protocol.go

@@ -99,6 +99,12 @@ func (typ TypeNamed) String() string {
 	return typ.Name
 }
 
+type TypeAny struct { }
+
+func (typ TypeAny) String() string {
+	return "Any"
+}
+
 func HashType(typ Type) [16]byte {
 	// TODO: if we ever want to make the compiler more efficient, this would
 	// be a good place to start, complex string concatenation in a hot path

tape/dynamic.go

@@ -86,9 +86,9 @@ func EncodeAny(encoder *Encoder, value any, tag Tag) (n int, err error) {
 	return n, fmt.Errorf("cannot encode type %T", value)
 }
 
-// DecodeAny decodes data and places it into destination, which must be a
+// DecodeAnyInto decodes data and places it into destination, which must be a
 // pointer to a supported type. See [EncodeAny] for a list of supported types.
-func DecodeAny(decoder *Decoder, destination any, tag Tag) (n int, err error) {
+func DecodeAnyInto(decoder *Decoder, destination any, tag Tag) (n int, err error) {
 	reflectDestination := reflect.ValueOf(destination)
 	if reflectDestination.Kind() != reflect.Pointer {
 		return n, fmt.Errorf("expected pointer destination, not %v", destination)
@@ -96,6 +96,16 @@ func DecodeAny(decoder *Decoder, destination any, tag Tag) (n int, err error) {
 	return decodeAny(decoder, reflectDestination.Elem(), tag)
 }
 
+// DecodeAny is like [DecodeAnyInto], but it automatically creates the
+// destination from the tag and data.
+func DecodeAny(decoder *Decoder, tag Tag) (value any, n int, err error) {
+	destination, err := skeletonValue(decoder, tag)
+	if err != nil { return nil, n, err }
+	nn, err := DecodeAnyInto(decoder, destination, tag)
+	n += nn; if err != nil { return nil, n, err }
+	return destination, n, err
+}
+
 // unknownSlicePlaceholder is inserted by skeletonValue and informs the program
 // that the destination for the slice needs to be generated based on the item
 // tag in the OTA.

tape/dynamic_test.go

@@ -104,7 +104,7 @@ func TestDecodeWrongType(test *testing.T) {
 		// integers should only assign to other integers
 		if index > 8 {
 			cas := func(destination any) {
-				n, err := DecodeAny(NewDecoder(bytes.NewBuffer(data[1:])), destination, Tag(data[0]))
+				n, err := DecodeAnyInto(NewDecoder(bytes.NewBuffer(data[1:])), destination, Tag(data[0]))
 				if err != nil { test.Fatalf("error: %v | n: %d", err, n) }
 				reflectValue := reflect.ValueOf(destination).Elem()
 				if reflectValue.CanInt() {
@@ -138,7 +138,7 @@ func TestDecodeWrongType(test *testing.T) {
 			{ var dest uint64; cas(&dest) }
 		}
 		arrayCase := func(destination any) {
-			n, err := DecodeAny(NewDecoder(bytes.NewBuffer(data[1:])), destination, Tag(data[0]))
+			n, err := DecodeAnyInto(NewDecoder(bytes.NewBuffer(data[1:])), destination, Tag(data[0]))
 			if err != nil { test.Fatalf("error: %v | n: %d", err, n) }
 			reflectDestination := reflect.ValueOf(destination)
 			reflectValue := reflectDestination.Elem()
@@ -256,7 +256,7 @@ func decAny(data []byte) (Tag, any, int, error) {
 	destination := map[uint16] any { }
 	tag, err := TagAny(destination)
 	if err != nil { return 0, nil, 0, err }
-	n, err := DecodeAny(NewDecoder(bytes.NewBuffer(data)), &destination, tag)
+	n, err := DecodeAnyInto(NewDecoder(bytes.NewBuffer(data)), &destination, tag)
 	if err != nil { return 0, nil, n, err }
 	return tag, destination, n, nil
 }