chore: upgrade coredns version (#550)

vendor/github.com/expr-lang/expr/parser/lexer/lexer.go

@@ -0,0 +1,230 @@
+package lexer
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/expr-lang/expr/file"
+)
+
+func Lex(source file.Source) ([]Token, error) {
+	l := &lexer{
+		source: source,
+		tokens: make([]Token, 0),
+		start:  0,
+		end:    0,
+	}
+	l.commit()
+
+	for state := root; state != nil; {
+		state = state(l)
+	}
+
+	if l.err != nil {
+		return nil, l.err.Bind(source)
+	}
+
+	return l.tokens, nil
+}
+
+type lexer struct {
+	source     file.Source
+	tokens     []Token
+	start, end int
+	err        *file.Error
+}
+
+const eof rune = -1
+
+func (l *lexer) commit() {
+	l.start = l.end
+}
+
+func (l *lexer) next() rune {
+	if l.end >= len(l.source) {
+		l.end++
+		return eof
+	}
+	r := l.source[l.end]
+	l.end++
+	return r
+}
+
+func (l *lexer) peek() rune {
+	r := l.next()
+	l.backup()
+	return r
+}
+
+func (l *lexer) backup() {
+	l.end--
+}
+
+func (l *lexer) emit(t Kind) {
+	l.emitValue(t, l.word())
+}
+
+func (l *lexer) emitValue(t Kind, value string) {
+	l.tokens = append(l.tokens, Token{
+		Location: file.Location{From: l.start, To: l.end},
+		Kind:     t,
+		Value:    value,
+	})
+	l.commit()
+}
+
+func (l *lexer) emitEOF() {
+	from := l.end - 2
+	if from < 0 {
+		from = 0
+	}
+	to := l.end - 1
+	if to < 0 {
+		to = 0
+	}
+	l.tokens = append(l.tokens, Token{
+		Location: file.Location{From: from, To: to},
+		Kind:     EOF,
+	})
+	l.commit()
+}
+
+func (l *lexer) skip() {
+	l.commit()
+}
+
+func (l *lexer) word() string {
+	// TODO: boundary check is NOT needed here, but for some reason CI fuzz tests are failing.
+	if l.start > len(l.source) || l.end > len(l.source) {
+		return "__invalid__"
+	}
+	return string(l.source[l.start:l.end])
+}
+
+func (l *lexer) accept(valid string) bool {
+	if strings.ContainsRune(valid, l.next()) {
+		return true
+	}
+	l.backup()
+	return false
+}
+
+func (l *lexer) acceptRun(valid string) {
+	for strings.ContainsRune(valid, l.next()) {
+	}
+	l.backup()
+}
+
+func (l *lexer) skipSpaces() {
+	r := l.peek()
+	for ; r == ' '; r = l.peek() {
+		l.next()
+	}
+	l.skip()
+}
+
+func (l *lexer) acceptWord(word string) bool {
+	pos := l.end
+
+	l.skipSpaces()
+
+	for _, ch := range word {
+		if l.next() != ch {
+			l.end = pos
+			return false
+		}
+	}
+	if r := l.peek(); r != ' ' && r != eof {
+		l.end = pos
+		return false
+	}
+
+	return true
+}
+
+func (l *lexer) error(format string, args ...any) stateFn {
+	if l.err == nil { // show first error
+		l.err = &file.Error{
+			Location: file.Location{
+				From: l.end - 1,
+				To:   l.end,
+			},
+			Message: fmt.Sprintf(format, args...),
+		}
+	}
+	return nil
+}
+
+func digitVal(ch rune) int {
+	switch {
+	case '0' <= ch && ch <= '9':
+		return int(ch - '0')
+	case 'a' <= lower(ch) && lower(ch) <= 'f':
+		return int(lower(ch) - 'a' + 10)
+	}
+	return 16 // larger than any legal digit val
+}
+
+func lower(ch rune) rune { return ('a' - 'A') | ch } // returns lower-case ch iff ch is ASCII letter
+
+func (l *lexer) scanDigits(ch rune, base, n int) rune {
+	for n > 0 && digitVal(ch) < base {
+		ch = l.next()
+		n--
+	}
+	if n > 0 {
+		l.error("invalid char escape")
+	}
+	return ch
+}
+
+func (l *lexer) scanEscape(quote rune) rune {
+	ch := l.next() // read character after '/'
+	switch ch {
+	case 'a', 'b', 'f', 'n', 'r', 't', 'v', '\\', quote:
+		// nothing to do
+		ch = l.next()
+	case '0', '1', '2', '3', '4', '5', '6', '7':
+		ch = l.scanDigits(ch, 8, 3)
+	case 'x':
+		ch = l.scanDigits(l.next(), 16, 2)
+	case 'u':
+		ch = l.scanDigits(l.next(), 16, 4)
+	case 'U':
+		ch = l.scanDigits(l.next(), 16, 8)
+	default:
+		l.error("invalid char escape")
+	}
+	return ch
+}
+
+func (l *lexer) scanString(quote rune) (n int) {
+	ch := l.next() // read character after quote
+	for ch != quote {
+		if ch == '\n' || ch == eof {
+			l.error("literal not terminated")
+			return
+		}
+		if ch == '\\' {
+			ch = l.scanEscape(quote)
+		} else {
+			ch = l.next()
+		}
+		n++
+	}
+	return
+}
+
+func (l *lexer) scanRawString(quote rune) (n int) {
+	ch := l.next() // read character after back tick
+	for ch != quote {
+		if ch == eof {
+			l.error("literal not terminated")
+			return
+		}
+		ch = l.next()
+		n++
+	}
+	l.emitValue(String, string(l.source[l.start+1:l.end-1]))
+	return
+}