[perf] Optimize AWK-style tokenizer for --nth

Approx. 50% less memory footprint and 40% improvement in query time

1 files changed, 7 insertions, 0 deletions

diff --git a/src/util/chars.go b/src/util/chars.go
index 25a15ddd..6034ee53 100644
--- a/src/util/chars.go
+++ b/src/util/chars.go
@@ -111,3 +111,10 @@ func (chars *Chars) ToRunes() []rune {
 	}
 	return runes
 }
+
+func (chars *Chars) Slice(b int, e int) Chars {
+	if chars.runes != nil {
+		return Chars{runes: chars.runes[b:e]}
+	}
+	return Chars{bytes: chars.bytes[b:e]}
+}