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perf(gsub-subset): serializeSingle/Multiple/Alternate/Ligature 改用 gidLookup 数组查找
serializeSingleSubst/MultipleSubst/AlternateSubst/LigatureSubst 原用 remapGid(origToNew Map) 对每个 coverage gid + 分量 gid 做哈希查询。subsetGSUB 入口已构建 gidLookup 数组 （下标=原gid，值=新gid/-1，比 Map.get 快 ~2×），但这四个函数未使用，仍传 origToNew Map。 serializeLigatureSubst 是 CJK ligature 子集化热点（50gid 子集占 subsetGSUB 65%， 每条 ligature 对全部分量密集 remapGid）。改为收 gidLookup 参数，remapGid(Map.get) → gidLookup[gid]（数组索引，-1 即子集外）。 四个函数签名 origToNew: Map → gidLookup: GidLookup，serializeSubtable 调度相应更新。 ChainContext format1 的两处 remapGid（serializeChain/parseChainRuleFormat1or2）暂未改 （FiraCode 路径 serialize 占比小，readCoverageRemapped 是主瓶颈）。 验证：基准测试 29 用例 SSIM 全部无回归；4 用例 sha256 输出字节逐字节等价。 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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崮生（子虚）
parent
51f969d3f0
commit
44f84e5659
@ -269,7 +269,7 @@ function serializeSingleSubst(
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w: Writer,
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r: Reader,
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off: number,
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origToNew: Map<number, number>,
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gidLookup: GidLookup,
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): boolean {
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const format = r.u16(off);
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const covOff = off + r.u16(off + 2);
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@ -280,16 +280,16 @@ function serializeSingleSubst(
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if (format === 1) {
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const delta = r.i16(off + 4);
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for (const g of covGids) {
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const fromNew = remapGid(origToNew, g);
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const toNew = remapGid(origToNew, (g + delta) & 0xffff);
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if (fromNew !== null && toNew !== null) entries.push({ from: fromNew, to: toNew });
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const fromNew = gidLookup[g];
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const toNew = gidLookup[(g + delta) & 0xffff];
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if (fromNew >= 0 && toNew >= 0) entries.push({ from: fromNew, to: toNew });
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}
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} else if (format === 2) {
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const count = r.u16(off + 4);
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for (let i = 0; i < covGids.length && i < count; i++) {
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const fromNew = remapGid(origToNew, covGids[i]);
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const toNew = remapGid(origToNew, r.u16(off + 6 + i * 2));
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if (fromNew !== null && toNew !== null) entries.push({ from: fromNew, to: toNew });
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const fromNew = gidLookup[covGids[i]];
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const toNew = gidLookup[r.u16(off + 6 + i * 2)];
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if (fromNew >= 0 && toNew >= 0) entries.push({ from: fromNew, to: toNew });
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}
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} else {
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return false;
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@ -362,7 +362,7 @@ function serializeMultipleSubst(
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w: Writer,
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r: Reader,
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off: number,
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origToNew: Map<number, number>,
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gidLookup: GidLookup,
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): boolean {
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const covOff = off + r.u16(off + 2);
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const seqCount = r.u16(off + 4);
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@ -371,14 +371,14 @@ function serializeMultipleSubst(
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/** 逐 coverage 字形读取其 sequence，重映射后保留有效项 */
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const entries: Array<{ from: number; seq: number[] }> = [];
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for (let i = 0; i < covGids.length && i < seqCount; i++) {
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const fromNew = remapGid(origToNew, covGids[i]);
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if (fromNew === null) continue;
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const fromNew = gidLookup[covGids[i]];
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if (fromNew < 0) continue;
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const seqOff = off + r.u16(off + 6 + i * 2);
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const glyphCount = r.u16(seqOff);
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const newSeq: number[] = [];
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for (let k = 0; k < glyphCount; k++) {
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const g = remapGid(origToNew, r.u16(seqOff + 2 + k * 2));
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if (g !== null) newSeq.push(g);
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const g = gidLookup[r.u16(seqOff + 2 + k * 2)];
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if (g >= 0) newSeq.push(g);
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}
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/** 序列至少 1 个目标 gid 才有意义 */
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if (newSeq.length > 0) entries.push({ from: fromNew, seq: newSeq });
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@ -412,7 +412,7 @@ function serializeAlternateSubst(
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w: Writer,
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r: Reader,
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off: number,
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origToNew: Map<number, number>,
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gidLookup: GidLookup,
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): boolean {
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const covOff = off + r.u16(off + 2);
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const altCount = r.u16(off + 4);
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@ -420,14 +420,14 @@ function serializeAlternateSubst(
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const entries: Array<{ from: number; alts: number[] }> = [];
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for (let i = 0; i < covGids.length && i < altCount; i++) {
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const fromNew = remapGid(origToNew, covGids[i]);
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if (fromNew === null) continue;
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const fromNew = gidLookup[covGids[i]];
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if (fromNew < 0) continue;
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const altOff = off + r.u16(off + 6 + i * 2);
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const cnt = r.u16(altOff);
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const newAlts: number[] = [];
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for (let k = 0; k < cnt; k++) {
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const g = remapGid(origToNew, r.u16(altOff + 2 + k * 2));
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if (g !== null) newAlts.push(g);
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const g = gidLookup[r.u16(altOff + 2 + k * 2)];
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if (g >= 0) newAlts.push(g);
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}
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if (newAlts.length > 0) entries.push({ from: fromNew, alts: newAlts });
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}
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@ -461,7 +461,7 @@ function serializeLigatureSubst(
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w: Writer,
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r: Reader,
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off: number,
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origToNew: Map<number, number>,
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gidLookup: GidLookup,
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): boolean {
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const covOff = off + r.u16(off + 2);
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const setCount = r.u16(off + 4);
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@ -470,22 +470,24 @@ function serializeLigatureSubst(
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/** 每个 coverage 字形收集有效 ligature 列表 */
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const entries: Array<{ from: number; ligs: Array<{ comp: number[]; lig: number }> }> = [];
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for (let i = 0; i < covGids.length && i < setCount; i++) {
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const fromNew = remapGid(origToNew, covGids[i]);
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if (fromNew === null) continue;
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/** gidLookup[origGid] = 新gid 或 -1（不在子集）。数组索引比 Map.get 快 ~2×，
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* serializeLigatureSubst 对每条 ligature 的全部分量密集 remapGid，是 CJK ligature 子集热点。 */
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const fromNew = gidLookup[covGids[i]];
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if (fromNew < 0) continue;
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const setOff = off + r.u16(off + 6 + i * 2);
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const ligCount = r.u16(setOff);
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const newLigs: Array<{ comp: number[]; lig: number }> = [];
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for (let j = 0; j < ligCount; j++) {
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const ligOff = setOff + r.u16(setOff + 2 + j * 2);
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const compCount = r.u16(ligOff);
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const ligNew = remapGid(origToNew, r.u16(ligOff + 2));
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if (ligNew === null) continue;
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const ligNew = gidLookup[r.u16(ligOff + 2)];
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if (ligNew < 0) continue;
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/** components 从第 2 字形开始（第 1 字形即 coverage 字形），compCount 含第 1 字形 */
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const compNew: number[] = [fromNew];
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let ok = true;
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for (let k = 0; k < compCount - 1; k++) {
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const c = remapGid(origToNew, r.u16(ligOff + 4 + k * 2));
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if (c === null) {
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const c = gidLookup[r.u16(ligOff + 4 + k * 2)];
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if (c < 0) {
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ok = false;
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break;
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}
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@ -1079,16 +1081,16 @@ function serializeSubtable(
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let ok: boolean;
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switch (type) {
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case LT_SINGLE:
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ok = serializeSingleSubst(w, r, off, origToNew);
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ok = serializeSingleSubst(w, r, off, gidLookup);
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break;
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case LT_MULTIPLE:
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ok = serializeMultipleSubst(w, r, off, origToNew);
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ok = serializeMultipleSubst(w, r, off, gidLookup);
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break;
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case LT_ALTERNATE:
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ok = serializeAlternateSubst(w, r, off, origToNew);
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ok = serializeAlternateSubst(w, r, off, gidLookup);
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break;
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case LT_LIGATURE:
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ok = serializeLigatureSubst(w, r, off, origToNew);
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ok = serializeLigatureSubst(w, r, off, gidLookup);
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break;
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case LT_CHAIN:
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ok = serializeChainedContextSubst(w, r, off, origToNew, covCache, gidLookup);
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