initial ugly implementation

README.md

+# cbor-gen
+
+Some basic utilities to generate fast path cbor codecs for your types.
+
+## License
+MIT

gen.go

+package typegen
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"reflect"
+)
+
+type ByteReader interface {
+	io.ByteReader
+	io.Reader
+}
+
+func CborReadHeader(br ByteReader) (byte, uint64, error) {
+	first, err := br.ReadByte()
+	if err != nil {
+		return 0, 0, err
+	}
+
+	maj := (first & 0xe0) >> 5
+	low := first & 0x1f
+
+	switch {
+	case low < 24:
+		return maj, uint64(low), nil
+	case low == 24:
+		next, err := br.ReadByte()
+		if err != nil {
+			return 0, 0, err
+		}
+		return maj, uint64(next), nil
+	case low == 25:
+		buf := make([]byte, 2)
+		if _, err := io.ReadFull(br, buf); err != nil {
+			return 0, 0, err
+		}
+		return maj, uint64(binary.BigEndian.Uint16(buf)), nil
+	case low == 26:
+		buf := make([]byte, 4)
+		if _, err := io.ReadFull(br, buf); err != nil {
+			return 0, 0, err
+		}
+		return maj, uint64(binary.BigEndian.Uint32(buf)), nil
+	case low == 27:
+		buf := make([]byte, 8)
+		if _, err := io.ReadFull(br, buf); err != nil {
+			return 0, 0, err
+		}
+		return maj, binary.BigEndian.Uint64(buf), nil
+	default:
+		return 0, 0, fmt.Errorf("invalid header: (%x)", first)
+	}
+}
+
+func CborEncodeMajorType(t byte, l uint64) []byte {
+	var b [9]byte
+	switch {
+	case l < 24:
+		b[0] = (t << 5) | byte(l)
+		return b[:1]
+	case l < (1 << 8):
+		b[0] = (t << 4) | 24
+		b[1] = byte(l)
+		return b[:2]
+	case l < (1 << 16):
+		b[0] = (t << 4) | 25
+		binary.BigEndian.PutUint16(b[1:3], uint16(l))
+		return b[:3]
+	case l < (1 << 32):
+		b[0] = (t << 4) | 26
+		binary.BigEndian.PutUint32(b[1:5], uint32(l))
+		return b[:5]
+	default:
+		b[0] = (t << 4) | 27
+		binary.BigEndian.PutUint64(b[1:], uint64(l))
+		return b[:]
+	}
+}
+
+func PrintHeaderAndUtilityMethods(w io.Writer, pkg string) error {
+	fmt.Fprintf(w, "package %s\n\n", pkg)
+
+	fmt.Fprintf(w, "import (\n")
+	fmt.Fprintf(w, "\t\"encoding/binary\"\n")
+	fmt.Fprintf(w, "\t\"fmt\"\n")
+	fmt.Fprintf(w, "\t\"io\"\n")
+	fmt.Fprintf(w, "\n\tcbg \"github.com/whyrusleeping/cbor-gen\"\n")
+	fmt.Fprintf(w, ")\n\n")
+
+	return nil
+}
+
+// Generates 'tuple representation' cbor encoders for the given type
+func GenTupleEncodersForType(i interface{}, w io.Writer) error {
+	t := reflect.TypeOf(i)
+
+	fmt.Fprintf(w, "func (t *%s) MarshalCBOR(w io.Writer) error {\n", t.Name())
+
+	if t.NumField() > 23 {
+		return fmt.Errorf("lazy programmer doesnt want to handle field counters > 23")
+	}
+
+	firstByte := (4 << 5) | byte(t.NumField())
+
+	fmt.Fprintf(w, "\tw.Write([]byte{0x%x})\n", firstByte)
+
+	for i := 0; i < t.NumField(); i++ {
+		f := t.Field(i)
+		fmt.Fprintf(w, "\t// t.%s (%s)\n", f.Name, f.Type)
+		switch f.Type.Kind() {
+		case reflect.String:
+			return fmt.Errorf("strings arent handled yet")
+		case reflect.Struct:
+			fmt.Fprintf(w, "\tif err := t.%s.MarshalCBOR(w); err != nil {\n", f.Name)
+			fmt.Fprintf(w, "\t\treturn err\n\t}\n\n")
+		case reflect.Uint64:
+			fmt.Fprintf(w, "\t w.Write(cbg.CborEncodeMajorType(0, t.%s))\n\n", f.Name)
+		case reflect.Slice:
+			e := f.Type.Elem()
+			if e.Kind() == reflect.Ptr {
+				e = e.Elem()
+			}
+
+			if e.Kind() == reflect.Uint8 {
+				fmt.Fprintf(w, "\tw.Write(cbg.CborEncodeMajorType(2, uint64(len(t.%s))))\n", f.Name)
+				fmt.Fprintf(w, "\tw.Write(t.%s)\n\n", f.Name)
+				continue
+			}
+
+			fmt.Fprintf(w, "\tw.Write(cbg.CborEncodeMajorType(4, uint64(len(t.%s))))\n", f.Name)
+			fmt.Fprintf(w, "\tfor i, v := range t.%s {\n", f.Name)
+			switch e.Kind() {
+			case reflect.Struct:
+				fmt.Fprintf(w, "\t\tif err := v.MarshalCBOR(w); err != nil {\n\t\t\treturn err\n\t\t}\n\t}\n\n")
+			default:
+				return fmt.Errorf("do not yet support slices of non-structs: %s %s", f.Type.Elem(), e.Kind())
+			}
+		default:
+			return fmt.Errorf("field %q of %q has unsupported kind %q", f.Name, t.Name(), f.Type.Kind())
+		}
+	}
+
+	fmt.Fprintf(w, "\treturn nil\n}\n\n")
+
+	// Now for the unmarshal
+
+	fmt.Fprintf(w, "func (t *%s) UnmarshalCBOR(br ByteReader) error {\n", t.Name())
+
+	fmt.Fprintf(w, "\tfirst, err := br.ReadByte()\n")
+	fmt.Fprintf(w, "\tif err != nil {\n\t\treturn err\n\t}\n\n")
+	fmt.Fprintf(w, "\tif first != 0x%x {\n", firstByte)
+	fmt.Fprintf(w, "\t\treturn fmt.Errorf(\"object had incorrect type or length\")\n\t}\n\n")
+
+	fmt.Fprintf(w, "\tvar maj byte\n\tvar extra uint64\n\n")
+	for i := 0; i < t.NumField(); i++ {
+		f := t.Field(i)
+		fmt.Fprintf(w, "\t// t.%s (%s)\n", f.Name, f.Type)
+		switch f.Type.Kind() {
+		case reflect.String:
+			return fmt.Errorf("strings arent handled yet")
+		case reflect.Struct:
+			fmt.Fprintf(w, "\tif err := t.%s.UnmarshalCBOR(br); err != nil {\n", f.Name)
+			fmt.Fprintf(w, "\t\treturn err\n\t}\n\n")
+		case reflect.Uint64:
+			fmt.Fprintf(w, "\tmaj, extra, err = cbg.CborReadHeader(br)\n\tif err != nil {\n\t\treturn err\n\t}\n\n")
+			fmt.Fprintf(w, "\tif maj != 0 {\n\t\treturn fmt.Errorf(\"wrong type for uint64 field\")\n\t}\n")
+			fmt.Fprintf(w, "\tt.%s = extra\n\n", f.Name)
+		case reflect.Slice:
+			e := f.Type.Elem()
+			if e.Kind() == reflect.Ptr {
+				e = e.Elem()
+			}
+
+			fmt.Fprintf(w, "\tmaj, extra, err = cbg.CborReadHeader(br)\n\tif err != nil {\n\t\treturn err\n\t}\n\n")
+			fmt.Fprintf(w, "\tif extra > 8192 {\n\t\treturn fmt.Errorf(\"array too large\")\n\t}\n")
+			if e.Kind() == reflect.Uint8 {
+				fmt.Fprintf(w, "\tt.%s = make([]byte, extra)\n", f.Name)
+				fmt.Fprintf(w, "\tif _, err := io.ReadFull(br, t.%s); err != nil {\n\t\treturn err\n\t}\n\n", f.Name)
+				continue
+			}
+
+			fmt.Fprintf(w, "\tt.%s = make([]%s, 0, extra)\n", f.Name, f.Type)
+			fmt.Fprintf(w, "\tfor i := 0; i < extra; i++ {\n")
+			switch e.Kind() {
+			case reflect.Struct:
+				fmt.Fprintf(w, "\t\tvar v %s\n", f.Type)
+				fmt.Fprintf(w, "\t\tif err := v.UnmarshalCBOR(br); err != nil {\n\t\t\treturn err\n\t\t}\n\n")
+				fmt.Fprintf(w, "\t\tt.%s = append(t.%s, v)\n", f.Name, f.Name)
+			default:
+				return fmt.Errorf("do not yet support slices of non-structs: %s", f.Type.Elem())
+			}
+			fmt.Fprintf(w, "\t}\n\n")
+		default:
+			return fmt.Errorf("field %q of %q has unsupported kind %q", f.Name, t.Name(), f.Type.Kind())
+		}
+	}
+
+	fmt.Fprintf(w, "\treturn nil\n}\n\n")
+
+	return nil
+}

go.mod

+module github.com/whyrusleeping/cbor-gen
+
+go 1.12