WIP

Signed-off-by: Alejandro Mery <amery@jpi.io>

lexer/lexer.go

@@ -0,0 +1,17 @@
+// Package lexer provides basic helpers to implement parsers
+package lexer
+
+// StateFn is a State Function of the parser
+type StateFn func() (StateFn, error)
+
+// Run runs a state machine until the state function either
+// returns nil or an error
+func Run(fn StateFn) error {
+	var err error
+
+	for fn != nil && err == nil {
+		fn, err = fn()
+	}
+
+	return err
+}

runes/reader.go

@@ -9,7 +9,7 @@ import (
 
 const (
 	// ReadBufferSize indicates the initial buffer size
-	ReadBufferSize = 1 << 7 // 128B
+	ReadBufferSize = 2 // 1 << 7 // 128B
 
 	// DoublingBufferSizeLimit indicates when we stop doubling
 	// and just add instead
@@ -18,7 +18,8 @@ const (
 
 // implemented interfaces
 var (
-	_ io.RuneReader = (*Reader)(nil)
+	_ io.RuneReader  = (*Reader)(nil)
+	_ io.RuneScanner = (*Reader)(nil)
 )
 
 // Reader is a RuneReader aimed at implementing text parsers
@@ -156,6 +157,22 @@ func (b *Reader) ReadRune() (rune, int, error) {
 	return r, l, nil
 }
 
+// UnreadRune moves the cursor where it was before the last call to ReadRune
+func (*Reader) UnreadRune() error {
+	return nil
+}
+
+// PeekRune returns information about the next rune without moving the
+// cursor
+func (b *Reader) PeekRune() (rune, int, error) {
+	r, l, err := b.ReadRune()
+	if err != nil {
+		return r, l, err
+	}
+	err = b.UnreadRune()
+	return r, l, err
+}
+
 // NewReader creates a new runes [Reader] using the given [io.Reader]
 func NewReader(r io.Reader) *Reader {
 	if r == nil {