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/**
*
* Adapted from https://github.com/mozilla-b2g/gaia/blob/f09993563fb5fec4393eb71816ce76cb00463190/shared/js/async_storage.js
* (converted to use Promises instead of callbacks).
*
* This file defines an asynchronous version of the localStorage API, backed by
* an IndexedDB database. It creates a global asyncStorage object that has
* methods like the localStorage object.
*
* To store a value use setItem:
*
* asyncStorage.setItem("key", "value");
*
* This returns a promise in case you want confirmation that the value has been stored.
*
* asyncStorage.setItem("key", "newvalue").then(function() {
* console.log("new value stored");
* });
*
* To read a value, call getItem(), but note that you must wait for a promise
* resolution for the value to be retrieved.
*
* asyncStorage.getItem("key").then(function(value) {
* console.log("The value of key is:", value);
* });
*
* Note that unlike localStorage, asyncStorage does not allow you to store and
* retrieve values by setting and querying properties directly. You cannot just
* write asyncStorage.key; you have to explicitly call setItem() or getItem().
*
* removeItem(), clear(), length(), and key() are like the same-named methods of
* localStorage, and all return a promise.
*
* The asynchronous nature of getItem() makes it tricky to retrieve multiple
* values. But unlike localStorage, asyncStorage does not require the values you
* store to be strings. So if you need to save multiple values and want to
* retrieve them together, in a single asynchronous operation, just group the
* values into a single object. The properties of this object may not include
* DOM elements, but they may include things like Blobs and typed arrays.
*
*/
"use strict";
const Promise = require("promise");
const DBNAME = "devtools-async-storage";
const DBVERSION = 1;
const STORENAME = "keyvaluepairs";
var db = null;
function withStore(type, onsuccess, onerror) {
if (db) {
let transaction = db.transaction(STORENAME, type);
let store = transaction.objectStore(STORENAME);
onsuccess(store);
} else {
let openreq = indexedDB.open(DBNAME, DBVERSION);
openreq.onerror = function withStoreOnError() {
onerror();
};
openreq.onupgradeneeded = function withStoreOnUpgradeNeeded() {
// First time setup: create an empty object store
openreq.result.createObjectStore(STORENAME);
};
openreq.onsuccess = function withStoreOnSuccess() {
db = openreq.result;
let transaction = db.transaction(STORENAME, type);
let store = transaction.objectStore(STORENAME);
onsuccess(store);
};
}
}
function getItem(itemKey) {
return new Promise((resolve, reject) => {
let req;
withStore("readonly", (store) => {
store.transaction.oncomplete = function onComplete() {
let value = req.result;
if (value === undefined) {
value = null;
}
resolve(value);
};
req = store.get(itemKey);
req.onerror = function getItemOnError() {
reject("Error in asyncStorage.getItem(): ", req.error.name);
};
}, reject);
});
}
function setItem(itemKey, value) {
return new Promise((resolve, reject) => {
withStore("readwrite", (store) => {
store.transaction.oncomplete = resolve;
let req = store.put(value, itemKey);
req.onerror = function setItemOnError() {
reject("Error in asyncStorage.setItem(): ", req.error.name);
};
}, reject);
});
}
function removeItem(itemKey) {
return new Promise((resolve, reject) => {
withStore("readwrite", (store) => {
store.transaction.oncomplete = resolve;
let req = store.delete(itemKey);
req.onerror = function removeItemOnError() {
reject("Error in asyncStorage.removeItem(): ", req.error.name);
};
}, reject);
});
}
function clear() {
return new Promise((resolve, reject) => {
withStore("readwrite", (store) => {
store.transaction.oncomplete = resolve;
let req = store.clear();
req.onerror = function clearOnError() {
reject("Error in asyncStorage.clear(): ", req.error.name);
};
}, reject);
});
}
function length() {
return new Promise((resolve, reject) => {
let req;
withStore("readonly", (store) => {
store.transaction.oncomplete = function onComplete() {
resolve(req.result);
};
req = store.count();
req.onerror = function lengthOnError() {
reject("Error in asyncStorage.length(): ", req.error.name);
};
}, reject);
});
}
function key(n) {
return new Promise((resolve, reject) => {
if (n < 0) {
resolve(null);
return;
}
let req;
withStore("readonly", (store) => {
store.transaction.oncomplete = function onComplete() {
let cursor = req.result;
resolve(cursor ? cursor.key : null);
};
let advanced = false;
req = store.openCursor();
req.onsuccess = function keyOnSuccess() {
let cursor = req.result;
if (!cursor) {
// this means there weren"t enough keys
return;
}
if (n === 0 || advanced) {
// Either 1) we have the first key, return it if that's what they
// wanted, or 2) we"ve got the nth key.
return;
}
// Otherwise, ask the cursor to skip ahead n records
advanced = true;
cursor.advance(n);
};
req.onerror = function keyOnError() {
reject("Error in asyncStorage.key(): ", req.error.name);
};
}, reject);
});
}
exports.getItem = getItem;
exports.setItem = setItem;
exports.removeItem = removeItem;
exports.clear = clear;
exports.length = length;
exports.key = key;
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