From bb89ad6c73341a2677b42d6c0a735837c739105a Mon Sep 17 00:00:00 2001
From: seonghobae <8172694+seonghobae@users.noreply.github.com>
Date: Sat, 4 Jul 2026 20:54:27 +0000
Subject: [PATCH] =?UTF-8?q?=EC=84=B1=EB=8A=A5=20=EA=B0=9C=EC=84=A0:=20`esc?=
 =?UTF-8?q?apeHtml`=20=ED=95=A8=EC=88=98=EC=9D=98=20=EC=97=AC=EB=9F=AC=20`?=
 =?UTF-8?q?replace`=20=ED=98=B8=EC=B6=9C=20=EC=B5=9C=EC=A0=81=ED=99=94?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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- 여러 번의 `.replace()` 호출로 인한 중간 문자열 할당 방지
- 단일 패스 루프와 지연 초기화(lazy-initialization)된 `StringBuilder` 사용
- 테스트 통과 및 JaCoCo 100% 커버리지 확인
---
 .jules/bolt.md                    |  4 ++++
 src/main/kotlin/html4tree/main.kt | 31 +++++++++++++++++++++++++------
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/.jules/bolt.md b/.jules/bolt.md
index 83cc604..1e61273 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -5,3 +5,7 @@
 ## 2024-05-24 - Loop Allocation Hot Paths
 **Learning:** Rendering directory entries with repeated string concatenation and list-based exclusion lookups creates avoidable allocation and lookup cost in large directories.
 **Action:** Use `StringBuilder` for entry rendering and a `Set` for excluded file names.
+
+## 2024-08-01 - Chained String Replace
+**Learning:** Using chained `.replace()` calls on a String for frequent operations (like HTML escaping) is inefficient due to multiple intermediate allocations.
+**Action:** Use a single-pass loop with a lazily-initialized `StringBuilder` for string manipulation functions called frequently on hot paths to minimize allocations and improve performance.
diff --git a/src/main/kotlin/html4tree/main.kt b/src/main/kotlin/html4tree/main.kt
index 2e2809f..b237de5 100644
--- a/src/main/kotlin/html4tree/main.kt
+++ b/src/main/kotlin/html4tree/main.kt
@@ -49,12 +49,31 @@ fun go(topDir: String, maxLevel: Int)  {
 }
 
 fun String.escapeHtml(): String {
-    return this.replace("&", "&amp;")
-               .replace("<", "&lt;")
-               .replace(">", "&gt;")
-               .replace("\"", "&quot;")
-               .replace("'", "&#x27;")
-               .replace("`", "&#x60;")
+    // ⚡ Bolt: Use a single-pass loop with a lazily-initialized StringBuilder
+    // to avoid intermediate string allocations from chained replace calls.
+    var sb: java.lang.StringBuilder? = null
+    for (i in this.indices) {
+        val c = this[i]
+        val replacement = when (c) {
+            '&' -> "&amp;"
+            '<' -> "&lt;"
+            '>' -> "&gt;"
+            '"' -> "&quot;"
+            '\'' -> "&#x27;"
+            '`' -> "&#x60;"
+            else -> null
+        }
+        if (replacement != null) {
+            if (sb == null) {
+                sb = java.lang.StringBuilder(this.length + 16)
+                sb.append(this, 0, i)
+            }
+            sb.append(replacement)
+        } else {
+            sb?.append(c)
+        }
+    }
+    return sb?.toString() ?: this
 }
 
 fun String.urlEncodePath(): String {