build-sys: import build system from darvaza.org/core

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

runes/reader.go

@@ -2,7 +2,6 @@ package runes
 
 import (
 	"bytes"
-	"errors"
 	"io"
 	"strings"
 	"unicode/utf8"
@@ -19,14 +18,7 @@ const (
 
 // implemented interfaces
 var (
-	_ io.RuneReader  = (*Reader)(nil)
-	_ io.RuneScanner = (*Reader)(nil)
-)
-
-var (
-	// ErrInvalidUnreadRune indicates UnreadRune() was calls after an
-	// action other than a successful ReadRune()
-	ErrInvalidUnreadRune = errors.New("invalid UnreadRune() call")
+	_ io.RuneReader = (*Reader)(nil)
 )
 
 // Reader is a RuneReader aimed at implementing text parsers
@@ -36,8 +28,6 @@ type Reader struct {
 	buf    []byte
 	off    int
 	cursor int
-
-	lastRuneSize int
 }
 
 // String returns what's already Read but not yet emitted or discarded
@@ -64,9 +54,6 @@ func (b *Reader) Discard() {
 		// step
 		b.off = b.cursor
 	}
-
-	// and prevent UnreadRune()
-	b.lastRuneSize = -1
 }
 
 // ready tells how many bytes are ready to decode
@@ -152,8 +139,6 @@ func (b *Reader) ReadRune() (rune, int, error) {
 	for {
 		err := b.needsBytes(count)
 		if err != nil {
-			b.lastRuneSize = -1
-
 			return 0, 0, err
 		}
 
@@ -168,35 +153,9 @@ func (b *Reader) ReadRune() (rune, int, error) {
 
 	// decode rune
 	r, l := utf8.DecodeRune(b.buf[b.cursor:])
-
-	// and remember for UnreadRune()
-	b.lastRuneSize = l
-
 	return r, l, nil
 }
 
-// UnreadRune moves the cursor where it was before the last call to ReadRune
-func (b *Reader) UnreadRune() error {
-	if b.lastRuneSize > 0 {
-		b.cursor -= b.lastRuneSize
-		b.lastRuneSize = -1
-		return nil
-	}
-
-	return ErrInvalidUnreadRune
-}
-
-// 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 {