IndexedDB 内容寻址存储与去重实践

概述内容寻址以数据哈希作为键，能够实现去重与快速引用。本文展示哈希计算与存储模型。哈希与存储async function digest(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('blobs')) db.createObjectStore('blobs', { keyPath: 'hash' }); };

r.onsuccess = () => resolve(r.result);

r.onerror = () => reject(r.error);

});

}

async function putBytes(bytes) {

const hash = await digest(bytes);

const db = await openDB('cas');

const tx = db.transaction('blobs', 'readwrite');

tx.objectStore('blobs').put({ hash, bytes });

await new Promise((resolve, reject) => { tx.oncomplete = resolve; tx.onerror = () => reject(tx.error); });

db.close();

return hash;

}

async function getBytes(hash) {

const db = await openDB('cas');

const tx = db.transaction('blobs', 'readonly');

const req = tx.objectStore('blobs').get(hash);

const rec = await new Promise((resolve, reject) => { req.onsuccess = () => resolve(req.result); req.onerror = () => reject(req.error); });

db.close();

return rec ? rec.bytes : null;

}