2019-05-11 16:40:31 +05:30
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<html>
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<head><meta charset="utf-8"></head>
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<body>
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<script type="text/javascript">
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2019-06-27 01:39:46 +05:30
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console.log = (...params) => {
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document.write(params.join(" ")+"<br>");
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};
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2019-05-11 16:40:31 +05:30
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function reqAsPromise(req) {
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return new Promise((resolve, reject) => {
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req.onsuccess = () => resolve(req);
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req.onerror = (err) => reject(err);
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});
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}
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function txnAsPromise(txn) {
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return new Promise((resolve, reject) => {
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txn.addEventListener("complete", resolve);
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txn.addEventListener("abort", reject);
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});
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}
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function iterateCursor(cursor, processValue) {
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// TODO: does cursor already have a value here??
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return new Promise((resolve, reject) => {
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cursor.onerror = (event) => {
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reject(new Error("Query failed: " + event.target.errorCode));
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};
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// collect results
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cursor.onsuccess = (event) => {
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const cursor = event.target.result;
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if (!cursor) {
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resolve(false);
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return; // end of results
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}
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const {done, jumpTo} = processValue(cursor.value, cursor.key);
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if (done) {
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resolve(true);
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} else {
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cursor.continue(jumpTo);
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}
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};
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});
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}
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/**
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* Checks if a given set of keys exist.
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* Calls `callback(key, found)` for each key in `keys`, in an unspecified order.
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* If the callback returns true, the search is halted and callback won't be called again.
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*/
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async function findKeys(target, keys, backwards, callback) {
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const direction = backwards ? "prev" : "next";
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const compareKeys = (a, b) => backwards ? -indexedDB.cmp(a, b) : indexedDB.cmp(a, b);
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const sortedKeys = keys.slice().sort(compareKeys);
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console.log(sortedKeys);
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const firstKey = backwards ? sortedKeys[sortedKeys.length - 1] : sortedKeys[0];
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const lastKey = backwards ? sortedKeys[0] : sortedKeys[sortedKeys.length - 1];
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const cursor = target.openKeyCursor(IDBKeyRange.bound(firstKey, lastKey), direction);
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let i = 0;
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let consumerDone = false;
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await iterateCursor(cursor, (value, key) => {
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// while key is larger than next key, advance and report false
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while(i < sortedKeys.length && compareKeys(sortedKeys[i], key) < 0 && !consumerDone) {
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console.log("before match", sortedKeys[i]);
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consumerDone = callback(sortedKeys[i], false);
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++i;
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}
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if (i < sortedKeys.length && compareKeys(sortedKeys[i], key) === 0 && !consumerDone) {
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console.log("match", sortedKeys[i]);
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consumerDone = callback(sortedKeys[i], true);
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++i;
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}
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const done = consumerDone || i >= sortedKeys.length;
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const jumpTo = !done && sortedKeys[i];
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return {done, jumpTo};
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});
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// report null for keys we didn't to at the end
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while (!consumerDone && i < sortedKeys.length) {
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console.log("afterwards", sortedKeys[i]);
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consumerDone = callback(sortedKeys[i], false);
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++i;
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}
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}
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async function findFirstOrLastOccurringEventId(target, roomId, eventIds, findLast = false) {
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const keys = eventIds.map(eventId => [roomId, eventId]);
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const results = new Array(keys.length);
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let firstFoundEventId;
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// find first result that is found and has no undefined results before it
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function firstFoundAndPrecedingResolved() {
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let inc = findLast ? -1 : 1;
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let start = findLast ? results.length - 1 : 0;
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for(let i = start; i >= 0 && i < results.length; i += inc) {
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if (results[i] === undefined) {
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return;
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} else if(results[i] === true) {
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return keys[i];
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}
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}
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}
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await findKeys(target, keys, findLast, (key, found) => {
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const index = keys.indexOf(key);
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results[index] = found;
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firstFoundEventId = firstFoundAndPrecedingResolved();
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return !!firstFoundEventId;
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});
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return firstFoundEventId;
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}
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(async () => {
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let db;
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let isNew = false;
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// open db
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{
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const req = window.indexedDB.open("prototype-idb-continue-key");
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req.onupgradeneeded = (ev) => {
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const db = ev.target.result;
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db.createObjectStore("timeline", {keyPath: ["roomId", "eventId"]});
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isNew = true;
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};
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db = (await reqAsPromise(req)).result;
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}
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const roomId = "!abcdef:localhost";
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if (isNew) {
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const txn = db.transaction(["timeline"], "readwrite");
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const store = txn.objectStore("timeline");
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for (var i = 1; i <= 100; ++i) {
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store.add({roomId, eventId: `$${i * 10}`});
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}
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await txnAsPromise(txn);
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}
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console.log("show all in order we get them");
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{
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const txn = db.transaction(["timeline"], "readonly");
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const store = txn.objectStore("timeline");
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const cursor = store.openKeyCursor();
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await iterateCursor(cursor, (value, key) => {
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console.log(key);
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return {done: false};
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});
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}
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console.log("run findKeys");
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{
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const txn = db.transaction(["timeline"], "readonly");
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const store = txn.objectStore("timeline");
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const eventIds = ["$992", "$1000", "$1010", "$991", "$500", "$990"];
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// const eventIds = ["$992", "$1010"];
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const keys = eventIds.map(eventId => [roomId, eventId]);
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await findKeys(store, keys, false, (key, found) => {
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console.log(key, found);
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});
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}
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console.log("run findFirstOrLastOccurringEventId");
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{
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const txn = db.transaction(["timeline"], "readonly");
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const store = txn.objectStore("timeline");
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const eventIds = ["$992", "$1000", "$1010", "$991", "$500", "$990", "$123"];
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const firstMatch = await findFirstOrLastOccurringEventId(store, roomId, eventIds, false);
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console.log("firstMatch", firstMatch);
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const lastMatch = await findFirstOrLastOccurringEventId(store, roomId, eventIds, true);
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console.log("lastMatch", lastMatch);
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}
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})();
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</script>
|
|
|
|
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</body>
|
|
|
|
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</html>
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