Migrate realtime-callbacks to TypeScript

src/realtime-callbacks.ts

@@ -0,0 +1,203 @@
+/*
+Copyright 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+/* A re-implementation of the javascript callback functions (setTimeout,
+ * clearTimeout; setInterval and clearInterval are not yet implemented) which
+ * try to improve handling of large clock jumps (as seen when
+ * suspending/resuming the system).
+ *
+ * In particular, if a timeout would have fired while the system was suspended,
+ * it will instead fire as soon as possible after resume.
+ */
+
+import { logger } from './logger';
+
+// we schedule a callback at least this often, to check if we've missed out on
+// some wall-clock time due to being suspended.
+const TIMER_CHECK_PERIOD_MS = 1000;
+
+// counter, for making up ids to return from setTimeout
+let count = 0;
+
+// the key for our callback with the real global.setTimeout
+let realCallbackKey;
+
+// a sorted list of the callbacks to be run.
+// each is an object with keys [runAt, func, params, key].
+const callbackList = [];
+
+// var debuglog = logger.log.bind(logger);
+const debuglog = function(...params: any[]) {};
+
+/**
+ * Replace the function used by this module to get the current time.
+ *
+ * Intended for use by the unit tests.
+ *
+ * @param {function} [f] function which should return a millisecond counter
+ *
+ * @internal
+ */
+export function setNow(f: () => number): void {
+    now = f || Date.now;
+}
+let now = Date.now;
+
+/**
+ * reimplementation of window.setTimeout, which will call the callback if
+ * the wallclock time goes past the deadline.
+ *
+ * @param {function} func   callback to be called after a delay
+ * @param {Number} delayMs  number of milliseconds to delay by
+ *
+ * @return {Number} an identifier for this callback, which may be passed into
+ *                   clearTimeout later.
+ */
+export function setTimeout(func: (...params: any[]) => void, delayMs: number, ...params: any[]): number {
+    delayMs = delayMs || 0;
+    if (delayMs < 0) {
+        delayMs = 0;
+    }
+
+    const runAt = now() + delayMs;
+    const key = count++;
+    debuglog("setTimeout: scheduling cb", key, "at", runAt,
+        "(delay", delayMs, ")");
+    const data = {
+        runAt: runAt,
+        func: func,
+        params: params,
+        key: key,
+    };
+
+    // figure out where it goes in the list
+    const idx = binarySearch(
+        callbackList, function(el) {
+            return el.runAt - runAt;
+        },
+    );
+
+    callbackList.splice(idx, 0, data);
+    scheduleRealCallback();
+
+    return key;
+}
+
+/**
+ * reimplementation of window.clearTimeout, which mirrors setTimeout
+ *
+ * @param {Number} key   result from an earlier setTimeout call
+ */
+export function clearTimeout(key: number): void {
+    if (callbackList.length === 0) {
+        return;
+    }
+
+    // remove the element from the list
+    let i;
+    for (i = 0; i < callbackList.length; i++) {
+        const cb = callbackList[i];
+        if (cb.key == key) {
+            callbackList.splice(i, 1);
+            break;
+        }
+    }
+
+    // iff it was the first one in the list, reschedule our callback.
+    if (i === 0) {
+        scheduleRealCallback();
+    }
+}
+
+// use the real global.setTimeout to schedule a callback to runCallbacks.
+function scheduleRealCallback(): void {
+    if (realCallbackKey) {
+        global.clearTimeout(realCallbackKey);
+    }
+
+    const first = callbackList[0];
+
+    if (!first) {
+        debuglog("scheduleRealCallback: no more callbacks, not rescheduling");
+        return;
+    }
+
+    const timestamp = now();
+    const delayMs = Math.min(first.runAt - timestamp, TIMER_CHECK_PERIOD_MS);
+
+    debuglog("scheduleRealCallback: now:", timestamp, "delay:", delayMs);
+    realCallbackKey = global.setTimeout(runCallbacks, delayMs);
+}
+
+function runCallbacks(): void {
+    let cb;
+    const timestamp = now();
+    debuglog("runCallbacks: now:", timestamp);
+
+    // get the list of things to call
+    const callbacksToRun = [];
+    // eslint-disable-next-line
+    while (true) {
+        const first = callbackList[0];
+        if (!first || first.runAt > timestamp) {
+            break;
+        }
+        cb = callbackList.shift();
+        debuglog("runCallbacks: popping", cb.key);
+        callbacksToRun.push(cb);
+    }
+
+    // reschedule the real callback before running our functions, to
+    // keep the codepaths the same whether or not our functions
+    // register their own setTimeouts.
+    scheduleRealCallback();
+
+    for (let i = 0; i < callbacksToRun.length; i++) {
+        cb = callbacksToRun[i];
+        try {
+            cb.func.apply(global, cb.params);
+        } catch (e) {
+            logger.error("Uncaught exception in callback function",
+                e.stack || e);
+        }
+    }
+}
+
+/* search in a sorted array.
+ *
+ * returns the index of the last element for which func returns
+ * greater than zero, or array.length if no such element exists.
+ */
+function binarySearch<T>(array: T[], func: (T) => number): number {
+    // min is inclusive, max exclusive.
+    let min = 0;
+    let max = array.length;
+
+    while (min < max) {
+        const mid = (min + max) >> 1;
+        const res = func(array[mid]);
+        if (res > 0) {
+            // the element at 'mid' is too big; set it as the new max.
+            max = mid;
+        } else {
+            // the element at 'mid' is too small. 'min' is inclusive, so +1.
+            min = mid + 1;
+        }
+    }
+    // presumably, min==max now.
+    return min;
+}