whatcanGOwrong

go/pkg/mod/github.com/cosiner/argv@v0.1.0/scanner.go

@@ -0,0 +1,206 @@
+package argv
+
+import (
+	"unicode"
+)
+
+// Scanner is a cmdline string scanner.
+//
+// It split cmdline string to tokens: space, string, pipe, reverse quote string.
+type Scanner struct {
+	text []rune
+	rpos int
+}
+
+// NewScanner create a scanner and init it's internal states.
+func NewScanner(text string) *Scanner {
+	return &Scanner{
+		text: []rune(text),
+	}
+}
+
+const _RuneEOF = 0
+
+func (s *Scanner) nextRune() rune {
+	if s.rpos >= len(s.text) {
+		return _RuneEOF
+	}
+
+	r := s.text[s.rpos]
+	s.rpos++
+	return r
+}
+
+func (s *Scanner) unreadRune(r rune) {
+	if r != _RuneEOF {
+		s.rpos--
+	}
+}
+
+func (s *Scanner) isEscapeChars(r rune) (rune, bool) {
+	switch r {
+	case 'a':
+		return '\a', true
+	case 'b':
+		return '\b', true
+	case 'f':
+		return '\f', true
+	case 'n':
+		return '\n', true
+	case 'r':
+		return '\r', true
+	case 't':
+		return '\t', true
+	case 'v':
+		return '\v', true
+	case '\\':
+		return '\\', true
+	case '$':
+		return '$', true
+	}
+	return r, false
+}
+
+// TokenType is the type of tokens recognized by the scanner.
+type TokenType uint32
+
+// Token is generated by the scanner with a type and value.
+type Token struct {
+	Type  TokenType
+	Value []rune
+}
+
+const (
+	// TokString for string
+	TokString TokenType = iota + 1
+	TokStringSingleQuote
+	TokStringDoubleQuote
+	// TokPipe is the '|' character
+	TokPipe
+	// TokBackQuote is reverse quoted string
+	TokBackQuote
+	// TokSpace represent space character sequence
+	TokSpace
+	// TokEOF means the input end.
+	TokEOF
+)
+
+// Next return next token, if it reach the end, TOK_EOF will be returned.
+//
+// Error is returned for invalid syntax such as unpaired quotes.
+func (s *Scanner) Next() (Token, error) {
+	const (
+		Initial = iota + 1
+		Space
+		BackQuote
+		String
+		StringSingleQuote
+		StringDoubleQuote
+	)
+
+	var (
+		tok Token
+
+		state uint8 = Initial
+	)
+	for {
+		r := s.nextRune()
+		switch state {
+		case Initial:
+			switch {
+			case r == _RuneEOF:
+				tok.Type = TokEOF
+				return tok, nil
+			case r == '|':
+				tok.Type = TokPipe
+				return tok, nil
+			case r == '`':
+				state = BackQuote
+			case unicode.IsSpace(r):
+				state = Space
+				s.unreadRune(r)
+			case r == '\'':
+				state = StringSingleQuote
+			case r == '"':
+				state = StringDoubleQuote
+			default:
+				state = String
+				s.unreadRune(r)
+			}
+		case Space:
+			if r == _RuneEOF || !unicode.IsSpace(r) {
+				s.unreadRune(r)
+				tok.Type = TokSpace
+				return tok, nil
+			}
+		case BackQuote:
+			switch r {
+			case _RuneEOF:
+				return tok, ErrInvalidSyntax
+			case '`':
+				tok.Type = TokBackQuote
+				return tok, nil
+			default:
+				tok.Value = append(tok.Value, r)
+			}
+		case String:
+			switch {
+			case r == _RuneEOF, r == '|', r == '`', r == '\'', r == '"', unicode.IsSpace(r):
+				tok.Type = TokString
+				s.unreadRune(r)
+				return tok, nil
+			case r == '\\':
+				nr := s.nextRune()
+				if nr == _RuneEOF {
+					return tok, ErrInvalidSyntax
+				}
+				tok.Value = append(tok.Value, nr)
+			default:
+				tok.Value = append(tok.Value, r)
+			}
+		case StringSingleQuote, StringDoubleQuote:
+			switch r {
+			case _RuneEOF:
+				return tok, ErrInvalidSyntax
+			case '\'', '"':
+				if singleQuote := state == StringSingleQuote; singleQuote == (r == '\'') {
+					if singleQuote {
+						tok.Type = TokStringSingleQuote
+					} else {
+						tok.Type = TokStringDoubleQuote
+					}
+					return tok, nil
+				} else {
+					tok.Value = append(tok.Value, r)
+				}
+			case '\\':
+				nr := s.nextRune()
+				if escape, ok := s.isEscapeChars(nr); ok {
+					tok.Value = append(tok.Value, escape)
+				} else {
+					tok.Value = append(tok.Value, r)
+					s.unreadRune(nr)
+				}
+			default:
+				tok.Value = append(tok.Value, r)
+			}
+		}
+	}
+}
+
+// Scan is a utility function help split input text as tokens.
+func Scan(text string) ([]Token, error) {
+	s := NewScanner(text)
+	var tokens []Token
+	for {
+		tok, err := s.Next()
+		if err != nil {
+			return nil, err
+		}
+		tokens = append(tokens, tok)
+		if tok.Type == TokEOF {
+			break
+		}
+	}
+	return tokens, nil
+}