add vendor data

vendor/github.com/dunglas/httpsfv/decode.go

@@ -0,0 +1,63 @@
+package httpsfv
+
+import (
+	"errors"
+	"fmt"
+)
+
+// ErrUnexpectedEndOfString is returned when the end of string is unexpected.
+var ErrUnexpectedEndOfString = errors.New("unexpected end of string")
+
+// ErrUnrecognizedCharacter is returned when an unrecognized character in encountered.
+var ErrUnrecognizedCharacter = errors.New("unrecognized character")
+
+// UnmarshalError contains the underlying parsing error and the position at which it occurred.
+type UnmarshalError struct {
+	off int
+	err error
+}
+
+func (e *UnmarshalError) Error() string {
+	if e.err != nil {
+		return fmt.Sprintf("%s: character %d", e.err, e.off)
+	}
+
+	return fmt.Sprintf("unmarshal error: character %d", e.off)
+}
+
+func (e *UnmarshalError) Unwrap() error {
+	return e.err
+}
+
+type scanner struct {
+	data string
+	off  int
+}
+
+// scanWhileSp consumes spaces.
+func (s *scanner) scanWhileSp() {
+	for !s.eof() {
+		if s.data[s.off] != ' ' {
+			return
+		}
+
+		s.off++
+	}
+}
+
+// scanWhileOWS consumes optional white space (OWS) characters.
+func (s *scanner) scanWhileOWS() {
+	for !s.eof() {
+		c := s.data[s.off]
+		if c != ' ' && c != '\t' {
+			return
+		}
+
+		s.off++
+	}
+}
+
+// eof returns true if the parser consumed all available characters.
+func (s *scanner) eof() bool {
+	return s.off == len(s.data)
+}