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125 lines
1.9 KiB
Go
125 lines
1.9 KiB
Go
package main
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import (
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"errors"
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"fmt"
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"io"
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"strings"
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)
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type tokenType int
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const (
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t_error tokenType = iota // a stored lex error
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t_string // a string literal
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)
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type stateFn func(*lexer) (stateFn, error)
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type token struct {
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t tokenType
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s string
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}
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type lexer struct {
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in io.RuneReader
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out chan token
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buf []rune // running buffer for current lexeme
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}
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func (l *lexer) lex() {
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defer close(l.out)
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var err error
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fn := lexRoot
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for {
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fn, err = fn(l)
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switch err {
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case nil:
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case io.EOF:
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return
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default:
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l.out <- token{t_error, err.Error()}
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return
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}
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}
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}
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func (l *lexer) next() (rune, error) {
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r, _, err := l.in.ReadRune()
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return r, err
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}
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func (l *lexer) keep(r rune) {
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if l.buf == nil {
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l.buf = make([]rune, 0, 18)
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}
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l.buf = append(l.buf, r)
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}
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func (l *lexer) emit(t tokenType) {
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l.out <- token{t, string(l.buf)}
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l.buf = l.buf[0:0]
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}
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func lexString(in string) chan token {
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r := strings.NewReader(in)
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return lex(r)
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}
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func lex(r io.RuneReader) chan token {
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l := lexer{
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in: r,
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out: make(chan token),
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}
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go l.lex()
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return l.out
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}
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func fullTokens(c chan token) ([]token, error) {
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tokens := make([]token, 0, 32)
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for t := range c {
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if t.t == t_error {
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return nil, errors.New(t.s)
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}
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tokens = append(tokens, t)
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}
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return tokens, nil
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}
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func lexRoot(l *lexer) (stateFn, error) {
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r, err := l.next()
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if err != nil {
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return nil, err
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}
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switch r {
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case '"', '`':
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return lexStringLiteral(r), nil
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default:
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return nil, fmt.Errorf("unexpected rune in lexRoot: %c", r)
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}
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}
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func lexStringLiteral(delim rune) stateFn {
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return func(l *lexer) (stateFn, error) {
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r, err := l.next()
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if err != nil {
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return nil, err
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}
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switch r {
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case delim:
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l.emit(t_string)
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return lexRoot, nil
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case '\\':
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r, err := l.next()
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if err != nil {
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return nil, err
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}
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l.keep(r)
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return lexStringLiteral(delim), nil
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default:
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l.keep(r)
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return lexStringLiteral(delim), nil
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}
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}
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}
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