JLNTV_IPD/web-font
4
0
Fork 0
mirror of https://github.com/2234839/web-font.git synced 2026-09-04 23:02:27 +08:00
Code Issues Projects Releases Wiki Activity

perf(gsub): parseChainFormat3 coverage/records 数组按 count 预分配

Browse Source 
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) <noreply@anthropic.com>
This commit is contained in:
崮生（子虚） 2026-07-25 07:42:32 +08:00
parent 98102bc3be
commit 2ed666ec58
1 changed files with 6 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
backend/font_util/gsub-subset.ts
View File

@ -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<number[]>(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 };
}