Refactoring the line parsing

scanner.go

@@ -0,0 +1,58 @@
+package ftp
+
+// A Scanner for fields delimited by one or more whitespace characters
+type Scanner struct {
+	bytes    []byte
+	position int
+}
+
+// NewScanner creates a new Scanner
+func NewScanner(str string) *Scanner {
+	return &Scanner{
+		bytes: []byte(str),
+	}
+}
+
+// NextFields returns the next `count` fields
+func (s *Scanner) NextFields(count int) []string {
+	fields := make([]string, 0, count)
+	for i := 0; i < count; i++ {
+		if field := s.Next(); field != "" {
+			fields = append(fields, field)
+		} else {
+			break
+		}
+	}
+	return fields
+}
+
+// Next returns the next field
+func (s *Scanner) Next() string {
+	sLen := len(s.bytes)
+
+	// skip trailing whitespace
+	for s.position < sLen {
+		if s.bytes[s.position] != ' ' {
+			break
+		}
+		s.position++
+	}
+
+	start := s.position
+
+	// skip non-whitespace
+	for s.position < sLen {
+		if s.bytes[s.position] == ' ' {
+			s.position++
+			return string(s.bytes[start : s.position-1])
+		}
+		s.position++
+	}
+
+	return string(s.bytes[start:s.position])
+}
+
+// Remaining returns the remaining string
+func (s *Scanner) Remaining() string {
+	return string(s.bytes[s.position:len(s.bytes)])
+}