WebCrypto SHA-256 完整性校验与去重持久化

`title: WebCrypto SHA-256 完整性校验与去重持久化``categories: Web 开发/前端/数据管理``keywords: WebCrypto,SHA-256,完整性,去重,IndexedDB,OPFS``description: 使用 WebCrypto 计算 SHA-256 对资源与文件进行完整性校验，并以哈希索引实现去重持久化，减少重复存储与传输。`计算哈希async function sha256(bytes) {

const digest = await crypto.subtle.digest('SHA-256', bytes);

return Array.from(new Uint8Array(digest)).map(b => b.toString(16).padStart(2, '0')).join('');

}

去重写入async function dedupPut(db, name, bytes) {

const hash = await sha256(bytes);

// 查询是否已有同哈希记录

const exists = await hasHash(db, hash);

if (exists) return { skipped: true, hash };

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

const handle = await root.getFileHandle(name, { create: true });

const writable = await handle.createWritable();

await writable.write(bytes);

await writable.close();

await putMeta(db, { id: crypto.randomUUID(), name, hash, size: bytes.byteLength, ts: Date.now() });

return { skipped: false, hash };

}

索引与查询IndexedDB 以 `hash` 建索引，快速检测重复；读取时校验一致性并修复损坏。