initial commit

reader.go

@@ -0,0 +1,81 @@
+package bufr
+
+import (
+	"bufio"
+	"io"
+	"strings"
+
+	"git.tordarus.net/Tordarus/dstruct"
+)
+
+type Reader struct {
+	buf *dstruct.Stack[rune]
+	src *bufio.Reader
+}
+
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		buf: new(dstruct.Stack[rune]),
+		src: bufio.NewReader(r),
+	}
+}
+
+// Rune returns the next rune in r
+func (r *Reader) Rune() (rune, error) {
+	rn, _, err := r.src.ReadRune()
+	if err == nil {
+		r.buf.Push(rn)
+	}
+	return rn, err
+}
+
+// UnreadRune unreads the last rune.
+// The next read will include the unread rune.
+// It returns ErrNothingToUnread if there wasn't any read yet
+func (r *Reader) UnreadRune() error {
+	if r.buf.Empty() {
+		return ErrNothingToUnread.New()
+	}
+
+	if err := r.src.UnreadRune(); err == nil {
+		r.buf.Pop()
+	} else {
+		r.src = prependRune(r.buf.Pop(), r.src)
+	}
+
+	return nil
+}
+
+// UnreadString calls UnreadRune for each rune in str
+// The actual runes are irrelevant.
+// Only the rune count of str determines the amount of UnreadRune calls.
+// The first error occured will be returned immediately.
+func (r *Reader) UnreadString(str string) error {
+	for range str {
+		err := r.UnreadRune()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// StringWhile reads runes and calls f for each one.
+// It returns all runes as a string for which f returned true.
+// It stops when f returns false or an error occured.
+// The rune for which f returned false will not be unread.
+func (r *Reader) StringWhile(f func(rn rune) bool) (string, error) {
+	s := new(strings.Builder)
+
+	var err error
+	for rn, err := r.Rune(); err == nil && f(rn); rn, err = r.Rune() {
+		s.WriteRune(rn)
+	}
+
+	return s.String(), err
+}
+
+// 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) })
+}