support fixed length strings

codec_test.go

@@ -252,32 +252,45 @@ func TestBasicStruct(t *testing.T) {
 
 func TestStructWithFixedLenMember(t *testing.T) {
  type MyStruct struct {
+ Str string `lcs:"len=2"`
  Bytes []byte `lcs:"len=4"`
  OptionalBytes []byte `lcs:"len=4,optional"`
  }
 
  runTest(t, []*testCase{
  {
  v: MyStruct{
+ Str: "12",
  Bytes: []byte{0x11, 0x22},
  },
  errMarshal: errors.New("actual len not equal to fixed len"),
- name: "struct with wrong fixed len",
+ name: "struct with wrong fixed len (bytes)",
  skipUnmarshal: true,
  },
  {
  v: MyStruct{
+ Str: "",
  Bytes: []byte{0x11, 0x22, 0x33, 0x44},
  },
- b: hexMustDecode("11223344 00"),
+ errMarshal: errors.New("actual len not equal to fixed len"),
+ name: "struct with wrong fixed len (string)",
+ skipUnmarshal: true,
+ },
+ {
+ v: MyStruct{
+ Str: "12",
+ Bytes: []byte{0x11, 0x22, 0x33, 0x44},
+ },
+ b: hexMustDecode("31 32 11223344 00"),
  name: "struct with fixed len",
  },
  {
  v: MyStruct{
+ Str: "12",
  Bytes: []byte{0x11, 0x22, 0x33, 0x44},
  OptionalBytes: []byte{0x55, 0x66, 0x77, 0x88},
  },
- b: hexMustDecode("11223344 01 55667788"),
+ b: hexMustDecode("3132 11223344 01 55667788"),
  name: "struct with optional fixed len",
  },
  })

decode.go

@@ -285,7 +285,7 @@ func (d *Decoder) decodeStruct(rv reflect.Value) (err error) {
  }
  }
  fixedLen := 0
- if fixedLenStr, ok := tag["len"]; ok && fv.Kind() == reflect.Slice {
+ if fixedLenStr, ok := tag["len"]; ok && (fv.Kind() == reflect.Slice || fv.Kind() == reflect.String) {
  fixedLen, err = strconv.Atoi(fixedLenStr)
  if err != nil {
  return errors.New("tag len parse error: " + err.Error())

encode.go

@@ -137,7 +137,7 @@ func (e *Encoder) encodeStruct(rv reflect.Value) (err error) {
  }
  }
  fixedLen := 0
- if fixedLenStr, ok := tag["len"]; ok && fv.Kind() == reflect.Slice {
+ if fixedLenStr, ok := tag["len"]; ok && (fv.Kind() == reflect.Slice || fv.Kind() == reflect.String) {
  fixedLen, err = strconv.Atoi(fixedLenStr)
  if err != nil {
  return errors.New("tag len parse error: " + err.Error())