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GPOS/GSUB 表类 read 原用 reader.readBytes (= new Uint8Array(view.buffer, off, len).slice())， .slice() 拷贝整个表字节（初夏 GPOS 68KB、GSUB 31KB）。V8 中 68KB slice 耗 ~40μs， 而 subarray 零拷贝仅 ~0.3μs（130× 差距）。 GPOS/GSUB 是原始字节透传：subsetGPOS/subsetGSUB 只读 OTReader + 写全新 OTWriter， write 只 writeBytes 只读，optimize 不碰，整个 read→optimize→subset→write 生命周期 从不原地修改底层字节，故可安全返回共享 ArrayBuffer 的 subarray 视图。 初夏 full read 0.124→0.063ms (-49%)，readBuffer 0.165→0.098ms。 全基准 SSIM 与输出字节完全不变。 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
51 lines
2.4 KiB
TypeScript
51 lines
2.4 KiB
TypeScript
import fs from 'node:fs';
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import * as TTFReaderNS from './vendor/fonteditor-core/lib/ttf/ttfreader.js';
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const TTFReader: any = TTFReaderNS.default.default ?? TTFReaderNS.default;
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const support: any = (await import('./vendor/fonteditor-core/lib/ttf/table/support.js')).default.default ?? (await import('./vendor/fonteditor-core/lib/ttf/table/support.js')).default;
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const buf = fs.readFileSync('/mnt/d/字体资源/初夏明朝/初夏明朝-Regular.ttf');
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const ab = buf.buffer.slice(buf.byteOffset, buf.byteOffset+buf.byteLength) as ArrayBuffer;
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const cps = Array.from('，。！？、；：“”‘’').map(c => c.codePointAt(0)!);
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// 先拿到 reader + tables 目录
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const r0 = new (TTFReader as any)({ subset: cps, kerning: true });
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// 手动复刻 readBuffer 前半，拿 reader + tables
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const Reader = (await import('./vendor/fonteditor-core/lib/ttf/reader.js')).default.default ?? (await import('./vendor/fonteditor-core/lib/ttf/reader.js')).default;
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const Directory = (await import('./vendor/fonteditor-core/lib/ttf/directory.js')).default.default ?? (await import('./vendor/fonteditor-core/lib/ttf/directory.js')).default;
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function makeReader() {
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const reader = new Reader(ab, 0, ab.byteLength, false);
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reader.offset = 12;
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return reader;
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}
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// 各表独立计时
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function timeTable(tableName: string, iters = 15) {
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const TableClass = support[tableName];
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if (!TableClass) { console.log(` ${tableName}: 无 support 类`); return; }
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// warmup + 计时
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const ts: number[] = [];
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for (let i = 0; i < 5; i++) {
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const reader = makeReader();
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const dir = new Directory(12).read(reader, {});
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if (!dir[tableName]) return;
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const tc = new TableClass(dir[tableName].offset);
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tc.read(reader, { tables: dir, readOptions: { subset: cps, kerning: true } } as any);
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}
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for (let i = 0; i < iters; i++) {
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const reader = makeReader();
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const dir = new Directory(12).read(reader, {});
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const tc = new TableClass(dir[tableName].offset);
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const t0 = performance.now();
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tc.read(reader, { tables: dir, readOptions: { subset: cps, kerning: true } } as any);
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ts.push(performance.now() - t0);
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}
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ts.sort((a,b)=>a-b);
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console.log(` ${tableName}: ${ts[Math.floor(ts.length/2)].toFixed(3)}ms (min ${ts[0].toFixed(3)})`);
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}
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console.log('=== 初夏标点 各表 read 耗时 ===');
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for (const t of ['head','hhea','maxp','OS/2','name','cmap','hmtx','vmtx','GPOS','GSUB','post']) {
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timeTable(t);
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}
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