From 694364769e8a5f1d26817450ccf87bca84af4fec Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=B4=AE=E7=94=9F=EF=BC=88=E5=AD=90=E8=99=9A=EF=BC=89?=
 <2234839456@qq.com>
Date: Fri, 24 Jul 2026 16:34:08 +0800
Subject: [PATCH] =?UTF-8?q?perf(gsub-reachable):=20=E5=90=88=E5=B9=B6=20lo?=
 =?UTF-8?q?okupRelOffs=20=E8=AF=BB=E5=8F=96=E5=88=B0=20lookup=20parse=20?=
 =?UTF-8?q?=E4=B8=BB=E5=BE=AA=E7=8E=AF?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

原实现先收集 lookupRelOffs 到中间数组，主循环再按下标回读。合并后直接在
主循环内读取偏移，省去中间数组分配与一次回读。FiraCode collectReachable
-2.3%（0.116→0.113ms），reachable 集合 sha256 不变

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 backend/font_util/gsub-reachable.ts | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/backend/font_util/gsub-reachable.ts b/backend/font_util/gsub-reachable.ts
index 318853b..31625e3 100644
--- a/backend/font_util/gsub-reachable.ts
+++ b/backend/font_util/gsub-reachable.ts
@@ -104,19 +104,16 @@ export function collectReachableGsubTargets(
   const lookupListOff = r.u16(8);
 
   const lookupCount = r.u16(lookupListOff);
-  const lookupRelOffs: number[] = [];
-  for (let i = 0; i < lookupCount; i++) {
-    lookupRelOffs.push(r.u16(lookupListOff + 2 + i * 2));
-  }
 
-  /** 解析每个 lookup 的 (effectiveType, subtableAbsOffs) */
+  /** 解析每个 lookup 的 (effectiveType, subtableAbsOffs)。
+   *  合并 lookupRelOffs 读取到主循环（避免先收集到中间数组再按下标回读）。 */
   interface LookupParsed {
     effectiveType: number;
     subtableAbsOffs: number[];
   }
   const lookups: LookupParsed[] = [];
   for (let i = 0; i < lookupCount; i++) {
-    const lOff = lookupListOff + lookupRelOffs[i];
+    const lOff = lookupListOff + r.u16(lookupListOff + 2 + i * 2);
     const lookupType = r.u16(lOff);
     const subTableCount = r.u16(lOff + 4);
     const subtableAbsOffs: number[] = [];