Commit() method implemented

reader.go

@@ -5,18 +5,18 @@ import (
 	"io"
 	"strings"
 
-	"git.tordarus.net/Tordarus/dstruct"
+	"git.milar.in/milarin/ds"
 )
 
 type Reader struct {
-	buf *dstruct.Stack[posRune]
+	buf ds.Stack[posRune]
 	src *bufio.Reader
 	pos *Position
 }
 
 func NewReader(r io.Reader) *Reader {
 	return &Reader{
-		buf: new(dstruct.Stack[posRune]),
+		buf: ds.NewArrayStack[posRune](),
 		src: bufio.NewReader(r),
 		pos: &Position{},
 	}
@@ -43,6 +43,21 @@ func (r *Reader) Rune() (rune, error) {
 	return rn, err
 }
 
+// PeekRune returns the next rune in r without advancing reader position.
+// The next read will return the same rune again.
+func (r *Reader) PeekRune() (rune, error) {
+	rn, err := r.Rune()
+	if err != nil {
+		return 0, err
+	}
+
+	if err := r.UnreadRune(); err != nil {
+		return 0, err
+	}
+
+	return rn, nil
+}
+
 // UnreadRune unreads the last rune.
 // The next read will include the unread rune.
 // It returns ErrNothingToUnread if there wasn't any read yet
@@ -93,7 +108,41 @@ func (r *Reader) StringWhile(f func(rn rune) bool) (string, error) {
 	return s.String(), err
 }
 
+// PeekStringWhile acts as StringWhile but does not advance reader position
+func (r *Reader) PeekStringWhile(f func(rn rune) bool) (string, error) {
+	str, err := r.StringWhile(f)
+	if err != nil {
+		return "", err
+	}
+
+	if err := r.UnreadString(str); err != nil {
+		return "", err
+	}
+
+	return str, nil
+}
+
 // StringUntil is a shorthand for r.StringWhile(func(rn rune) bool { return !f(rn) })
 func (r *Reader) StringUntil(f func(rn rune) bool) (string, error) {
 	return r.StringWhile(func(rn rune) bool { return !f(rn) })
 }
+
+// PeekStringUntil acts as StringUntil but does not advance reader position
+func (r *Reader) PeekStringUntil(f func(rn rune) bool) (string, error) {
+	str, err := r.StringUntil(f)
+	if err != nil {
+		return "", err
+	}
+
+	if err := r.UnreadString(str); err != nil {
+		return "", err
+	}
+
+	return str, nil
+}
+
+// Commit clears the internal buffer and therefore removes all data which were already read.
+// After calling Commit any unreads will return ErrNothingToUnread until another read occured.
+func (r *Reader) Commit() {
+	r.buf.Clear()
+}