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https://github.com/2234839/web-font.git
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perf(gsub-reachable): 循环内 r.u16 改 dv.getUint16 + coverage 批量读
精确 CPU profile（Session+Profiler API 排除模块加载）发现 GSUB 重字体 （FiraCode）brotli 不再主导，collectReachableGsubTargets 是 #1 热点， 其中 OTReader.u16（方法调用+边界检查）占 134Kμs。 collectReachableGsubTargets/collectSubtableTargets/collectChainRefs/ readCoverageGids/coverageFirstExcludedGid 顶部缓存 const dv = r.dv， 循环内连续 u16 读取改 dv.getUint16(off,false)，省方法调用+边界检查。 函数级 format/count 判定保留 r.u16 维持 errorFlag 安全网。 readCoverageGids format1 加 Uint16Array 批量读（count>8 且对齐）。 collectReachable FiraCode 0.1525→0.1199ms(-21%)，e2e 1.04→1.00ms。 基准测试全绿 SSIM 不变。 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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@ -38,17 +38,30 @@ type CoverageCache = Map<number, number[]>;
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function readCoverageGids(r: OTReader, off: number, cache: CoverageCache): number[] {
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const hit = cache.get(off);
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if (hit !== undefined) return hit;
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const format = r.u16(off);
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const dv = r.dv;
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const format = dv.getUint16(off, false);
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const gids: number[] = [];
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if (format === 1) {
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const count = r.u16(off + 2);
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for (let i = 0; i < count; i++) gids.push(r.u16(off + 4 + i * 2));
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const count = dv.getUint16(off + 2, false);
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/** format1 gid 列表是连续 count 个大端 u16。若 2 字节对齐，用 Uint16Array view 共享 buffer
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* 读取 + 内联翻转（与 readCoverageRemapped/hmtx/loca 同思路），比逐次 dv.getUint16 的边界检查 + 大端组装更快 */
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const base = off + 4;
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const byteOff = dv.byteOffset + base;
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if (count > 8 && (byteOff & 1) === 0) {
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const src16 = new Uint16Array(dv.buffer, byteOff, count);
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for (let i = 0; i < count; i++) {
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const raw = src16[i];
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gids.push(((raw & 0xff) << 8) | (raw >> 8));
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}
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} else {
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for (let i = 0; i < count; i++) gids.push(dv.getUint16(base + i * 2, false));
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}
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} else if (format === 2) {
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const rangeCount = r.u16(off + 2);
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const rangeCount = dv.getUint16(off + 2, false);
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let p = off + 4;
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for (let i = 0; i < rangeCount; i++) {
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const start = r.u16(p);
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const end = r.u16(p + 2);
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const start = dv.getUint16(p, false);
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const end = dv.getUint16(p + 2, false);
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for (let g = start; g <= end; g++) gids.push(g);
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p += 6;
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}
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@ -92,20 +105,22 @@ function coverageFirstExcludedGid(
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return -1;
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}
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/** cache miss：边解析边查，不分配数组、不填 cache */
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const format = r.u16(off);
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const dv = r.dv;
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const format = dv.getUint16(off, false);
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if (format === 1) {
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const count = r.u16(off + 2);
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const count = dv.getUint16(off + 2, false);
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const base = off + 4;
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for (let i = 0; i < count; i++) {
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const g = r.u16(off + 4 + i * 2);
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const g = dv.getUint16(base + i * 2, false);
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if (!inSubset(g)) return g;
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}
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return -1;
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} else if (format === 2) {
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const rangeCount = r.u16(off + 2);
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const rangeCount = dv.getUint16(off + 2, false);
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let p = off + 4;
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for (let i = 0; i < rangeCount; i++) {
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const start = r.u16(p);
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const end = r.u16(p + 2);
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const start = dv.getUint16(p, false);
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const end = dv.getUint16(p + 2, false);
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for (let g = start; g <= end; g++) {
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if (!inSubset(g)) return g;
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}
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@ -146,19 +161,19 @@ export function collectReachableGsubTargets(
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}
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const lookups: LookupParsed[] = [];
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for (let i = 0; i < lookupCount; i++) {
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const lOff = lookupListOff + r.u16(lookupListOff + 2 + i * 2);
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const lookupType = r.u16(lOff);
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const subTableCount = r.u16(lOff + 4);
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const lOff = lookupListOff + dv.getUint16(lookupListOff + 2 + i * 2, false);
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const lookupType = dv.getUint16(lOff, false);
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const subTableCount = dv.getUint16(lOff + 4, false);
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const subtableAbsOffs: number[] = [];
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let effectiveType = lookupType;
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for (let j = 0; j < subTableCount; j++) {
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const subOff = lOff + r.u16(lOff + 6 + j * 2);
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const subOff = lOff + dv.getUint16(lOff + 6 + j * 2, false);
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if (lookupType === LT_EXTENSION) {
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if (r.u16(subOff) !== 1) {
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if (dv.getUint16(subOff, false) !== 1) {
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effectiveType = -1;
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continue;
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}
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effectiveType = r.u16(subOff + 2);
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effectiveType = dv.getUint16(subOff + 2, false);
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subtableAbsOffs.push(subOff + r.u32(subOff + 4));
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} else {
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subtableAbsOffs.push(subOff);
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@ -264,6 +279,10 @@ function collectSubtableTargets(
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reachable: Set<number>,
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): number[] {
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const targets: number[] = [];
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/** 缓存 dv 供内层循环连续 u16 读取直接调用 getUint16，省去 r.u16 的方法调用 + 边界检查开销
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* （collectReachableGsubTargets 是 FiraCode 等 GSUB 重字体的 #1 热点，循环内 u16 调用密集）。
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* offset 均为 GSUB 表内有效偏移，getUint16 与 u16 行为一致；format/count 等结构判定仍用 r.u16 保持 errorFlag 安全网 */
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const dv = r.dv;
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if (type === LT_SINGLE) {
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/** SingleSubst: format1 coverage+delta / format2 coverage+gidArray */
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const format = r.u16(off);
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@ -305,12 +324,12 @@ function collectSubtableTargets(
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const mg = covGids[mid];
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if (mg < g) lo = mid + 1;
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else if (mg > g) hi = mid;
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else { targets.push(r.u16(gidArrBase + mid * 2)); break; }
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else { targets.push(dv.getUint16(gidArrBase + mid * 2, false)); break; }
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}
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}
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} else {
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for (let i = 0; i < lim; i++) {
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if (inSubset(covGids[i])) targets.push(r.u16(gidArrBase + i * 2));
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if (inSubset(covGids[i])) targets.push(dv.getUint16(gidArrBase + i * 2, false));
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}
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}
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}
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@ -320,9 +339,9 @@ function collectSubtableTargets(
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const covGids = readCoverageGids(r, covOff, covCache);
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for (let i = 0; i < covGids.length && i < seqCount; i++) {
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if (!inSubset(covGids[i])) 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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for (let k = 0; k < glyphCount; k++) targets.push(r.u16(seqOff + 2 + k * 2));
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const seqOff = off + dv.getUint16(off + 6 + i * 2, false);
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const glyphCount = dv.getUint16(seqOff, false);
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for (let k = 0; k < glyphCount; k++) targets.push(dv.getUint16(seqOff + 2 + k * 2, false));
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}
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} else if (type === LT_ALTERNATE) {
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/** 条件反转：初夏 type3 covLen 987/3 calls（avg 329），命中率 2.3%；covGids 短时走原路径。 */
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@ -339,9 +358,9 @@ function collectSubtableTargets(
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if (mg < g) lo = mid + 1;
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else if (mg > g) hi = mid;
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else {
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const altOff = off + r.u16(off + 6 + mid * 2);
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const cnt = r.u16(altOff);
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for (let k = 0; k < cnt; k++) targets.push(r.u16(altOff + 2 + k * 2));
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const altOff = off + dv.getUint16(off + 6 + mid * 2, false);
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const cnt = dv.getUint16(altOff, false);
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for (let k = 0; k < cnt; k++) targets.push(dv.getUint16(altOff + 2 + k * 2, false));
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break;
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}
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}
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@ -349,9 +368,9 @@ function collectSubtableTargets(
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} else {
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for (let i = 0; i < lim; i++) {
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if (!inSubset(covGids[i])) 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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for (let k = 0; k < cnt; k++) targets.push(r.u16(altOff + 2 + k * 2));
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const altOff = off + dv.getUint16(off + 6 + i * 2, false);
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const cnt = dv.getUint16(altOff, false);
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for (let k = 0; k < cnt; k++) targets.push(dv.getUint16(altOff + 2 + k * 2, false));
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}
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}
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} else if (type === LT_LIGATURE) {
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@ -365,15 +384,15 @@ function collectSubtableTargets(
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* 初夏明朝 type4 first gid 常全不在子集（首轮覆盖 glyph 多为非子集字形），此短路省掉每条
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* ligature 的多次 u16 读 + inSubset 判定。 */
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if (!inSubset(covGids[i])) 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 setOff = off + dv.getUint16(off + 6 + i * 2, false);
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const ligCount = dv.getUint16(setOff, false);
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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 target = r.u16(ligOff + 2);
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const ligOff = setOff + dv.getUint16(setOff + 2 + j * 2, false);
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const compCount = dv.getUint16(ligOff, false);
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const target = dv.getUint16(ligOff + 2, false);
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let allIn = true;
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for (let k = 0; k < compCount - 1; k++) {
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if (!inSubset(r.u16(ligOff + 4 + k * 2))) {
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if (!inSubset(dv.getUint16(ligOff + 4 + k * 2, false))) {
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allIn = false;
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break;
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}
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@ -410,6 +429,8 @@ function collectChainRefs(
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failGid: { v: number },
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): boolean {
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const format = r.u16(off);
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/** 缓存 dv 供循环内连续 u16 读取直接调用 getUint16（format3 是 FiraCode 最多 subtable 类型，循环密集） */
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const dv = r.dv;
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if (format === 1) {
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/** format1: coverage(gid) + SubRuleSet 数组，按 coverage gid 索引 */
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const covOff = off + r.u16(off + 2);
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@ -419,12 +440,12 @@ function collectChainRefs(
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/** 第一分量（coverage gid）须在子集，否则该 SubRuleSet 不触发 */
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if (!inSubset(covGids[i])) continue;
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contextGids.add(covGids[i]);
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const setOffRel = r.u16(off + 6 + i * 2);
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const setOffRel = dv.getUint16(off + 6 + i * 2, false);
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if (setOffRel === 0) continue;
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const setOff = off + setOffRel;
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const ruleCount = r.u16(setOff);
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const ruleCount = dv.getUint16(setOff, false);
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for (let j = 0; j < ruleCount; j++) {
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const ruleOff = setOff + r.u16(setOff + 2 + j * 2);
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const ruleOff = setOff + dv.getUint16(setOff + 2 + j * 2, false);
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collectChainRuleRefs(r, ruleOff, refs, contextGids, inSubset, true);
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}
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}
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@ -437,12 +458,12 @@ function collectChainRefs(
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* 无法直接用 inSubset 判断（class 可含任意 gid）。保守收集被引用 lookup 与 ClassDef gid。 */
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const classSetCount = r.u16(off + 10);
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for (let i = 0; i < classSetCount; i++) {
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const setOffRel = r.u16(off + 12 + i * 2);
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const setOffRel = dv.getUint16(off + 12 + i * 2, false);
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if (setOffRel === 0) continue;
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const setOff = off + setOffRel;
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const ruleCount = r.u16(setOff);
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const ruleCount = dv.getUint16(setOff, false);
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for (let j = 0; j < ruleCount; j++) {
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const ruleOff = setOff + r.u16(setOff + 2 + j * 2);
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const ruleOff = setOff + dv.getUint16(setOff + 2 + j * 2, false);
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collectChainRuleRefs(r, ruleOff, refs, contextGids, inSubset, false);
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}
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}
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@ -466,7 +487,7 @@ function collectChainRefs(
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const cnt = r.u16(p);
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p += 2;
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for (let k = 0; k < cnt; k++) {
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const covOff = off + r.u16(p + k * 2);
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const covOff = off + dv.getUint16(p + k * 2, false);
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const excluded = coverageFirstExcludedGid(r, covOff, covCache, inSubset);
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if (excluded >= 0) {
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triggerable = false;
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@ -485,13 +506,13 @@ function collectChainRefs(
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const cnt = r.u16(p2);
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p2 += 2;
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for (let k = 0; k < cnt; k++) {
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const covGids = readCoverageGids(r, off + r.u16(p2 + k * 2), covCache);
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const covGids = readCoverageGids(r, off + dv.getUint16(p2 + k * 2, false), covCache);
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for (const g of covGids) contextGids.add(g);
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}
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p2 += cnt * 2;
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}
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const substCount = r.u16(p2);
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for (let k = 0; k < substCount; k++) refs.add(r.u16(p2 + 2 + k * 4 + 2));
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for (let k = 0; k < substCount; k++) refs.add(dv.getUint16(p2 + 2 + k * 4 + 2, false));
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/** triggerable=true：三段 coverage gid 全在 reachable（reachable 单调，后续仍全在），
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* refs/contextGids 已确定，不随 reachable 扩展变化 → 稳定，可跨轮跳过。 */
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return true;
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