ReadableStream 分块 SHA-256 校验与续写 OPFS 实践

概述对大文件进行分块校验并续写可提升可靠性。本文给出分块摘要与 OPFS 续写示例。分块摘要与续写async function sha256(bytes) { const buf = await crypto.subtle.digest('SHA-256', bytes); return Array.from(new Uint8Array(buf)).map(x=>x.toString(16).padStart(2,'0')).join(''); }

function openDB(name) { return new Promise((resolve, reject) => { const r = indexedDB.open(name, 1); r.onupgradeneeded = () => { const db = r.result; if (!db.objectStoreNames.contains('progress')) db.createObjectStore('progress'); }; r.onsuccess = () => resolve(r.result); r.onerror = () => reject(r.error); }); }

async function saveProgress(key, val) { const db = await openDB('resume'); const tx = db.transaction('progress','readwrite'); tx.objectStore('progress').put(val, key); await new Promise((res, rej) => { tx.oncomplete = res; tx.onerror = () => rej(tx.error); }); db.close(); }

async function loadProgress(key) { const db = await openDB('resume'); const tx = db.transaction('progress','readonly'); const req = tx.objectStore('progress').get(key); const v = await new Promise((res, rej) => { req.onsuccess = () => res(req.result||{ index:0 }); req.onerror = () => rej(req.error); }); db.close(); return v; }

async function resumeWrite(file, path, size = 1024*1024) {

const root = await navigator.storage.getDirectory();

const fh = await root.getFileHandle(path, { create: true });

const ws = await fh.createWritable();

const prog = await loadProgress(path);

let o = prog.index * size; let idx = prog.index;

while (o < file.size) {

const b = file.slice(o, o + size);

const ab = await b.arrayBuffer();

const hex = await sha256(new Uint8Array(ab));

await ws.write(new Uint8Array(ab));

idx++; o += size; await saveProgress(path, { index: idx, lastChunkHash: hex });

}

await ws.close();

}