From 2ed666ec58d9ac4050d8cfe85f3c386b93710a04 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: Sat, 25 Jul 2026 07:42:32 +0800 Subject: [PATCH] =?UTF-8?q?perf(gsub):=20parseChainFormat3=20coverage/reco?= =?UTF-8?q?rds=20=E6=95=B0=E7=BB=84=E6=8C=89=20count=20=E9=A2=84=E5=88=86?= =?UTF-8?q?=E9=85=8D?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit arr: number[][] 与 records 对象数组原用空数组 + push，fmt3 高频路径（每 subtable 三组 coverage + records）触发 GrowFastSmiOrObjectElements。改按已知 count/seqCount 预分配容量 + 下标赋值。 node --prof GrowFast 4.3%→3.6%、ArrayPrototypePush 3.7%→2.5%。FiraCode 输出字节 不变（acc 一致），29 用例 SSIM 全通过。 Co-Authored-By: Claude Opus 4.8 (1M context) --- backend/font_util/gsub-subset.ts | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/backend/font_util/gsub-subset.ts b/backend/font_util/gsub-subset.ts index 9125b11..bda3d2c 100644 --- a/backend/font_util/gsub-subset.ts +++ b/backend/font_util/gsub-subset.ts @@ -1178,13 +1178,14 @@ function parseChainFormat3( const readCovArr = (): number[][] | null => { const count = r.u16(p); p += 2; - const arr: number[][] = []; + /** 按 count 预分配容量，消除 push 触发的 GrowFast（fmt3 高频，每 subtable 三组 coverage） */ + const arr: number[][] = new Array(count); for (let k = 0; k < count; k++) { const covOff = off + dv.getUint16(p + k * 2, false); const newGids = readCoverageRemapped(r, covOff, gidLookup, covCache); /** coverage 全部 gid 落在子集外（原非空）→ 规则失效 */ if (newGids === null) return null; - arr.push(newGids); + arr[k] = newGids; } p += count * 2; return arr; @@ -1196,9 +1197,10 @@ function parseChainFormat3( const seqCount = r.u16(p); p += 2; - const records: Array<{ seq: number; lookup: number }> = []; + /** 按 seqCount 预分配，消除 records 对象数组 grow */ + const records: Array<{ seq: number; lookup: number }> = new Array<{ seq: number; lookup: number }>(seqCount); for (let k = 0; k < seqCount; k++) { - records.push({ seq: dv.getUint16(p + k * 4, false), lookup: dv.getUint16(p + k * 4 + 2, false) }); + records[k] = { seq: dv.getUint16(p + k * 4, false), lookup: dv.getUint16(p + k * 4 + 2, false) }; } return { backCovs, inputCovs, lookCovs, records }; }