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⚡ Bolt: [성능 개선] 정적 CSS 및 해시 계산 캐싱 (디렉토리 반복문 최적화) #196

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⚡ Bolt: [성능 개선] 정적 CSS 및 해시 계산 캐싱 (디렉토리 반복문 최적화) #196

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⚡ Bolt: [성능 개선] 정적 CSS 및 해시 계산 캐싱 (디렉토리 반복문 최적화)
seonghobae Jul 16, 2026
987a526
⚡ Bolt: [성능 개선] 정적 CSS 및 해시 계산 캐싱 (디렉토리 반복문 최적화)
seonghobae Jul 16, 2026
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3 changes: 3 additions & 0 deletions .jules/bolt.md
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Original file line number Diff line number Diff line change
Expand Up @@ -43,3 +43,6 @@
## 2025-01-24 - 단일 readAttributes 호출로 파일 속성 조회 최적화
**학습:** `isDirectory`, `!it.isDirectory()`, `isSymbolicLink` 3개의 개별적인 파일 시스템 I/O 호출을 수행하면 성능 저하가 큽니다. 이를 단일 `Files.readAttributes` 호출로 변경하여 메타데이터를 한 번에 조회함으로써 I/O 오버헤드를 대폭 줄일 수 있음을 확인했습니다.
**조치:** 디렉토리 순회 시 파일의 여러 속성을 확인할 때는 개별적인 stat 호출보다 `Files.readAttributes`를 사용하여 필요한 모든 속성을 한 번에 가져오는 방식을 우선적으로 고려해야 합니다.
## 2024-05-18 - Extracting Static Strings and Hashes in Kotlin Loops
**Learning:** When optimizing performance in directory processing loops (like `process_dir`), extracting large constant strings (e.g., static CSS) and deterministic calculations (e.g., SHA-256 hashing) into a `private object` using `@JvmField` prevents redundant allocations and CPU overhead per directory iteration.
**Action:** Always look for static strings and hash calculations inside loops and extract them to objects or companion objects to ensure they are computed exactly once per application run.
153 changes: 78 additions & 75 deletions src/main/kotlin/html4tree/main.kt
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Expand Up @@ -13,6 +13,82 @@ import com.github.ajalt.clikt.parameters.options.default
import com.github.ajalt.clikt.parameters.arguments.argument
import com.github.ajalt.clikt.parameters.types.int

private object StaticHtmlResources {
const val CSS_CONTENT = """
body {
font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
line-height: 1.5;
padding: 1rem;
color: #1f2328;
}
main {
max-width: 800px;
margin: 0 auto;
}
ul {
list-style-type: none;
padding-left: 0;
}
a.dir-link {
display: flex;
align-items: flex-start;
gap: 0.5rem;
width: 100%;
overflow-wrap: anywhere;
box-sizing: border-box;
}
.icon {
flex-shrink: 0;
width: 1.25rem;
text-align: center;
}
a {
padding: 0.5rem;
text-decoration: none;
color: #0969da;
border-radius: 4px;
transition: background-color 0.2s ease, outline-color 0.2s ease;
}
a:hover, a:focus-visible {
background-color: #f6f8fa;
text-decoration: underline;
outline: 2px solid #0969da;
outline-offset: -2px;
}
@media (prefers-reduced-motion: reduce) {
a {
transition: none;
}
}
@media (prefers-color-scheme: dark) {
body {
background-color: #0d1117;
color: #c9d1d9;
}
a {
color: #58a6ff;
}
a:hover, a:focus-visible {
background-color: #161b22;
outline-color: #58a6ff;
}
}
.empty-dir {
padding: 0.5rem;
opacity: 0.7;
font-style: italic;
}
"""

@JvmField
val STYLE_HASH = "sha256-" + Base64.getEncoder().encodeToString(MessageDigest.getInstance("SHA-256").digest(CSS_CONTENT.toByteArray(Charsets.UTF_8)))

val CSS = """
<style>
${CSS_CONTENT} </style>
"""
}

class Html4tree : CliktCommand() {
val maxLevel:Int by option(help="Number of levels deep for which to generate an index.html file", hidden = false).int().default(-1)
val topDir: String by argument(help="Top directory to crawl")
Expand Down Expand Up @@ -244,91 +320,18 @@ fun process_dir(curr_dir: File, excludeSet: Set<String>? = null, dirFiles: Array

val exclude: Set<String> = excludeSet ?: process_ignore_file(curr_dir)

val cssContent = """
body {
font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
line-height: 1.5;
padding: 1rem;
color: #1f2328;
}
main {
max-width: 800px;
margin: 0 auto;
}
ul {
list-style-type: none;
padding-left: 0;
}
a.dir-link {
display: flex;
align-items: flex-start;
gap: 0.5rem;
width: 100%;
overflow-wrap: anywhere;
box-sizing: border-box;
}
.icon {
flex-shrink: 0;
width: 1.25rem;
text-align: center;
}
a {
padding: 0.5rem;
text-decoration: none;
color: #0969da;
border-radius: 4px;
transition: background-color 0.2s ease, outline-color 0.2s ease;
}
a:hover, a:focus-visible {
background-color: #f6f8fa;
text-decoration: underline;
outline: 2px solid #0969da;
outline-offset: -2px;
}
@media (prefers-reduced-motion: reduce) {
a {
transition: none;
}
}
@media (prefers-color-scheme: dark) {
body {
background-color: #0d1117;
color: #c9d1d9;
}
a {
color: #58a6ff;
}
a:hover, a:focus-visible {
background-color: #161b22;
outline-color: #58a6ff;
}
}
.empty-dir {
padding: 0.5rem;
opacity: 0.7;
font-style: italic;
}
"""

val styleHash = "sha256-" + Base64.getEncoder().encodeToString(MessageDigest.getInstance("SHA-256").digest(cssContent.toByteArray(Charsets.UTF_8)))

val css = """
<style>
${cssContent} </style>
"""

val index_top = """<!doctype html>
<html lang="ko">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="color-scheme" content="light dark">
<!-- 보안 향상: 인라인 스크립트 실행 방지 -->
<meta http-equiv="Content-Security-Policy" content="default-src 'none'; style-src '${styleHash}'; base-uri 'none'; form-action 'none';">
<meta http-equiv="Content-Security-Policy" content="default-src 'none'; style-src '${StaticHtmlResources.STYLE_HASH}'; base-uri 'none'; form-action 'none';">
<!-- 보안 향상: 리퍼러를 통한 디렉토리 경로 노출 방지 -->
<meta name="referrer" content="no-referrer">
<title>${curr_dir.getName().escapeHtml()}</title>
${css}
${StaticHtmlResources.CSS}
</head>
<body>
<main>
Expand Down
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