Move RuneReader into bytes package

cursor/helper.go

@@ -1,10 +1,7 @@
 package cursor
 
 import (
-	"errors"
-	"fmt"
 	"io"
-	"unicode/utf8"
 )
 
 // BufferedReaderAt uses a buffer to supplement an io.Reader
@@ -25,31 +22,3 @@ func NewBufferedReaderAt(r io.Reader, minBuffer uint64) *BufferedReaderAt {
 func (b *BufferedReaderAt) ReadAt(dst []byte, offset int64) (int, error) {
 	return 0, nil
 }
-
-// RuneReader is an io.RuneReader backed by a Cursor, for compatibility
-// with the regexp package.
-type RuneReader struct {
-	cursor Cursor[byte]
-}
-
-func NewRuneReader(c Cursor[byte]) *RuneReader {
-	return &RuneReader{cursor: c}
-}
-
-func (rr *RuneReader) ReadRune() (r rune, size int, err error) {
-	var b [4]byte
-	s := b[:]
-	n, next, err := rr.cursor.Read(s)
-	if err != nil && !errors.Is(err, io.EOF) {
-		rr.cursor = next
-		return 0, 0, fmt.Errorf("ReadRune: %w", err)
-	}
-	s = s[:n]
-	r, size = utf8.DecodeRune(s)
-	rr.cursor = rr.cursor.At(rr.cursor.Pos() + uint64(size))
-	return r, size, err
-}
-
-func (rr *RuneReader) Cursor() Cursor[byte] {
-	return rr.cursor
-}