positions introduced

pos_rune.go

@@ -0,0 +1,6 @@
+package bufr
+
+type posRune struct {
+	Rune rune
+	Pos  Position
+}

position.go

@@ -0,0 +1,17 @@
+package bufr
+
+type Position struct {
+	Index  int
+	Line   int
+	Column int
+}
+
+func (p *Position) Advance(rn rune) {
+	p.Index++
+	if rn == '\n' {
+		p.Line++
+		p.Column = 0
+	} else {
+		p.Column++
+	}
+}

reader.go

@@ -9,22 +9,36 @@ import (
 )
 
 type Reader struct {
-	buf *dstruct.Stack[rune]
+	buf *dstruct.Stack[posRune]
 	src *bufio.Reader
+	pos *Position
 }
 
 func NewReader(r io.Reader) *Reader {
 	return &Reader{
-		buf: new(dstruct.Stack[rune]),
+		buf: new(dstruct.Stack[posRune]),
 		src: bufio.NewReader(r),
+		pos: &Position{},
 	}
 }
 
+func (r *Reader) psrn(rn rune) posRune {
+	return posRune{
+		Rune: rn,
+		Pos:  *r.pos,
+	}
+}
+
+func (r *Reader) Pos() (index, line, column int) {
+	return r.pos.Index, r.pos.Line, r.pos.Column
+}
+
 // 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)
+		r.buf.Push(r.psrn(rn))
+		r.pos.Advance(rn)
 	}
 	return rn, err
 }
@@ -38,9 +52,12 @@ func (r *Reader) UnreadRune() error {
 	}
 
 	if err := r.src.UnreadRune(); err == nil {
-		r.buf.Pop()
+		rn := r.buf.Pop()
+		*r.pos = rn.Pos
 	} else {
-		r.src = prependRune(r.buf.Pop(), r.src)
+		rn := r.buf.Pop()
+		*r.pos = rn.Pos
+		r.src = prependRune(rn.Rune, r.src)
 	}
 
 	return nil

reader_test.go

@@ -0,0 +1,24 @@
+package bufr
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func TestPos(t *testing.T) {
+	r := NewReader(strings.NewReader("hello world\nsecond line"))
+
+	unread := false
+	for rn, err := r.Rune(); err == nil; rn, err = r.Rune() {
+		index, line, col := r.Pos()
+		fmt.Println(string(rn), index, line, col)
+
+		if !unread && rn == '\n' {
+			for i := 0; i < 5; i++ {
+				r.UnreadRune()
+			}
+			unread = true
+		}
+	}
+}