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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
class DatabaseUtils {
/** Wrap an IndexedDB request into a Promise.
*
* This should not be used for open().
*
* @param {IDBRequest} request the request to be wrapped
* @returns {Promise<Object>} promise that resolves with the request's result,
* or rejects with an error
*/
static async promiseForRequest(request) {
return new Promise((resolve, reject) => {
request.onsuccess = event => { resolve(event.target.result); };
request.onerror = event => { reject(event.target.error); };
request.onblocked = event => {
reject(event.target.error ||
(new Error("blocked by other database connections")));
};
request.onupgradeneeded = event => {
reject(event.target.error ||
(new Error("unexpected upgradeneeded event")));
};
});
}
/** Wrap an IndexedDB database open request into a Promise.
*
* This is intended to be used by open().
*
* @param {IDBOpenDBRequest} request the request to be wrapped
* @returns {Promise<{database: idbDatabase, transaction: IDBTransaction?}>}
* promise that resolves with an object whose "database" property is the
* newly opened database; if an upgradeneeded event is received, the
* "transaction" property holds the upgrade transaction
*/
static async promiseForOpenRequest(request) {
return new Promise((resolve, reject) => {
request.onsuccess = event => {
resolve({ database: event.target.result, transaction: null });
};
request.onerror = event => { reject(event.target.error); };
request.onblocked = event => {
reject(event.target.error ||
(new Error("blocked by other database connections")));
};
request.onupgradeneeded = event => {
resolve({
database: event.target.result,
transaction: event.target.transaction
});
};
});
}
/** Wrap an IndexedDB transaction into a Promise.
*
* @param {IDBTransaction} transaction the transaction to be wrapped
* @returns {Promise<Object>} promise that resolves with undefined when the
* transaction is completed, or rejects with an error if the transaction
* is aborted or errors out
*/
static async promiseForTransaction(transaction) {
return new Promise((resolve, reject) => {
transaction.oncomplete = () => { resolve(); };
transaction.onabort = event => { reject(event.target.error); };
transaction.onerror = event => { reject(event.target.error); };
});
}
}
class Database {
/** Open a database.
*
* @param {string} dbName the name of the database to be opened
* @return {Promise<Database>} promise that resolves with a new Database
* instance for the open database
*/
static async open(dbName) {
const request = indexedDB.open(dbName, 1);
const result = await DatabaseUtils.promiseForOpenRequest(request);
if (result.transaction !== null) {
fail("expected db to exist");
return;
}
return new Database(dbName, result.database);
}
/** Do not instantiate directly. Use Database.open() instead.
*
* @param {string} dbName the database's name
* @param {IDBDatabase} idbDatabase the IndexedDB instance wrapped by this
*/
constructor(dbName, idbDatabase) {
this._dbName = dbName;
this._idbDatabase = idbDatabase;
}
/** Closes the underlying database. All future operations will fail. */
close() {
this._idbDatabase.close();
}
/** Reads from a store by iterating a cursor.
*
* @param {string} storeName the name of the store being read
* @param {{index?: string, range?: IDBKeyRange}} query narrows down the data
* being read
* @param {function(IDBCursor): boolean} cursorCallback called for each cursor
* yielded by the iteration; must return a truthy value to continue
* iteration, or a falsey value to stop iterating
*/
async iterateCursor(storeName, query, cursorCallback) {
const transaction = this._idbDatabase.transaction([storeName], 'readonly');
const transactionPromise = DatabaseUtils.promiseForTransaction(transaction);
const objectStore = transaction.objectStore(storeName);
const dataSource = ('index' in query) ? objectStore.index(query.index)
: objectStore;
const request = ('range' in query) ? dataSource.openCursor(query.range)
: dataSource.openCursor();
while (true) {
const cursor = await DatabaseUtils.promiseForRequest(request);
if (!cursor)
break; // The iteration completed.
const willContinue = cursorCallback(cursor);
if (!willContinue)
break;
cursor.continue();
}
await transactionPromise;
return true;
}
async read() {
const status = document.getElementById('status');
status.textContent = 'Started reading items';
let i = 0;
const result = await this.iterateCursor('store', {}, cursor => {
i += 1;
if (cursor.primaryKey !== i) {
status.textContent =
`Incorrect primaryKey - wanted ${i} got ${cursor.primaryKey}`;
return false;
}
if (cursor.key !== i) {
status.textContent = `Incorrect key - wanted ${i} got ${cursor.key}`;
return false;
}
if (cursor.value.id !== i) {
status.textContent =
`Incorrect value.id - wanted ${i} got ${cursor.key}`;
return false;
}
return true;
});
if (!result) {
status.textContent = `Failed to read items`;
return false;
}
status.textContent = `Done reading ${i} items`;
return true;
}
};
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