From 4b1dfa1c4dd05a3be79b3b609c7219be862b27d6 Mon Sep 17 00:00:00 2001
From: Daisuke Maki <lestrrat+github@gmail.com>
Date: Sun, 22 Feb 2026 00:26:02 +0900
Subject: [PATCH] fix: fast-path StripANSISequence to skip regexp when no ESC
 byte

Benchmark (10k lines):
  plain text: 1023us -> 37us (-96%), 1.7MiB -> 0B (-100%), 30k -> 0 allocs
  95% plain:  1064us -> 162us (-85%), 1720KiB -> 63KiB (-96%), 30.5k -> 2k allocs
---
 internal/util/bench_test.go | 40 +++++++++++++++++++++++++++++++++++++
 internal/util/util.go       |  8 +++++++-
 2 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 internal/util/bench_test.go

diff --git a/internal/util/bench_test.go b/internal/util/bench_test.go
new file mode 100644
index 0000000..bf621a6
--- /dev/null
+++ b/internal/util/bench_test.go
@@ -0,0 +1,40 @@
+package util
+
+import (
+	"fmt"
+	"testing"
+)
+
+func BenchmarkStripANSISequenceBulk(b *testing.B) {
+	b.Run("10k_plain_lines", func(b *testing.B) {
+		lines := make([]string, 10_000)
+		for i := range lines {
+			lines[i] = fmt.Sprintf("line %d: this is a typical line without any ansi codes at all padding", i)
+		}
+		b.ResetTimer()
+		b.ReportAllocs()
+		for b.Loop() {
+			for _, l := range lines {
+				StripANSISequence(l)
+			}
+		}
+	})
+
+	b.Run("10k_mixed_95pct_plain", func(b *testing.B) {
+		lines := make([]string, 10_000)
+		for i := range lines {
+			if i%20 == 0 {
+				lines[i] = fmt.Sprintf("\x1b[31mline %d\x1b[0m: this has ansi codes in it for color", i)
+			} else {
+				lines[i] = fmt.Sprintf("line %d: this is a typical line without any ansi codes at all padding", i)
+			}
+		}
+		b.ResetTimer()
+		b.ReportAllocs()
+		for b.Loop() {
+			for _, l := range lines {
+				StripANSISequence(l)
+			}
+		}
+	})
+}
diff --git a/internal/util/util.go b/internal/util/util.go
index 61e34da..3576e18 100644
--- a/internal/util/util.go
+++ b/internal/util/util.go
@@ -3,6 +3,7 @@ package util
 import (
 	"errors"
 	"regexp"
+	"strings"
 	"unicode"
 )
 
@@ -44,8 +45,13 @@ func ContainsUpper(query string) bool {
 // Global var used to strips ansi sequences
 var reANSIEscapeChars = regexp.MustCompile("\x1B\\[(?:[0-9]{1,2}(?:;[0-9]{1,2})?)*[a-zA-Z]")
 
-// StripANSISequence strips ANSI escape sequences from the given string
+// StripANSISequence strips ANSI escape sequences from the given string.
+// Fast-path: if the string contains no ESC byte, return it unchanged
+// to avoid a regexp allocation.
 func StripANSISequence(s string) string {
+	if !strings.Contains(s, "\x1b") {
+		return s
+	}
 	return reANSIEscapeChars.ReplaceAllString(s, "")
 }