all: refactor attributes

attribute_errorcode.go

@@ -2,39 +2,88 @@ package stun
 
 // ErrorCodeAttribute represents ERROR-CODE attribute.
 type ErrorCodeAttribute struct {
-	Code   int
+	Code   ErrorCode
 	Reason []byte
 }
 
+// constants for ERROR-CODE encoding.
+const (
+	errorCodeReasonStart = 4
+	errorCodeClassByte   = 2
+	errorCodeNumberByte  = 3
+	errorCodeReasonMaxB  = 763
+	errorCodeModulo      = 100
+)
+
+// AddTo adds ERROR-CODE to m.
+func (c *ErrorCodeAttribute) AddTo(m *Message) error {
+	value := make([]byte,
+		errorCodeReasonStart, errorCodeReasonMaxB,
+	)
+	number := byte(c.Code % errorCodeModulo) // error code modulo 100
+	class := byte(c.Code / errorCodeModulo)  // hundred digit
+	value[errorCodeClassByte] = class
+	value[errorCodeNumberByte] = number
+	value = append(value, c.Reason...)
+	m.Add(AttrErrorCode, value)
+	return nil
+}
+
+// GetFrom decodes ERROR-CODE from m.
+func (c *ErrorCodeAttribute) GetFrom(m *Message) error {
+	v, err := m.Get(AttrErrorCode)
+	if err != nil {
+		return err
+	}
+	var (
+		class  = uint16(v[errorCodeClassByte])
+		number = uint16(v[errorCodeNumberByte])
+		code   = int(class*errorCodeModulo + number)
+		reason = v[errorCodeReasonStart:]
+	)
+	c.Code = ErrorCode(code)
+	c.Reason = reason
+	return nil
+}
+
 // ErrorCode is code for ERROR-CODE attribute.
 type ErrorCode int
 
+// ErrNoDefaultReason means that default reason for provided error code
+// is not defined in RFC.
+const ErrNoDefaultReason Error = "No default reason for ErrorCode"
+
+// AddTo adds ERROR-CODE with default reason to m. If there
+// is no default reason, returns ErrNoDefaultReason.
+func (c ErrorCode) AddTo(m *Message) error {
+	reason := errorReasons[c]
+	if reason == nil {
+		return ErrNoDefaultReason
+	}
+	a := &ErrorCodeAttribute{
+		Code:   c,
+		Reason: reason,
+	}
+	return a.AddTo(m)
+}
+
 // Possible error codes.
 const (
-	CodeTryAlternate     = 300
-	CodeBadRequest       = 400
-	CodeUnauthorised     = 401
-	CodeUnknownAttribute = 420
-	CodeStaleNonce       = 428
-	CodeRoleConflict     = 478
-	CodeServerError      = 500
+	CodeTryAlternate     ErrorCode = 300
+	CodeBadRequest       ErrorCode = 400
+	CodeUnauthorised     ErrorCode = 401
+	CodeUnknownAttribute ErrorCode = 420
+	CodeStaleNonce       ErrorCode = 428
+	CodeRoleConflict     ErrorCode = 478
+	CodeServerError      ErrorCode = 500
 )
 
-var errorReasons = map[int]string{
-	CodeTryAlternate:     "Try Alternate",
-	CodeBadRequest:       "Bad Request",
-	CodeUnauthorised:     "Unauthorised",
-	CodeUnknownAttribute: "Unknown Attribute",
-	CodeStaleNonce:       "Stale Nonce",
-	CodeServerError:      "Server Error",
-	CodeRoleConflict:     "Role Conflict",
-}
-
-// Reason returns recommended reason string.
-func (c ErrorCode) Reason() string {
-	reason, ok := errorReasons[int(c)]
-	if !ok {
-		return "Unknown Error"
-	}
-	return reason
+var errorReasons = map[ErrorCode][]byte{
+	CodeTryAlternate:     []byte("Try Alternate"),
+	CodeBadRequest:       []byte("Bad Request"),
+	CodeUnauthorised:     []byte("Unauthorised"),
+	CodeUnknownAttribute: []byte("Unknown Attribute"),
+	CodeStaleNonce:       []byte("Stale Nonce"),
+	CodeServerError:      []byte("Server Error"),
+	CodeRoleConflict:     []byte("Role Conflict"),
 }