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node_modules/react-native-web/dist/vendor/react-native/JSEventLoopWatchdog/index.js

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+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * 
+ */
+'use strict';
+
+import infoLog from '../infoLog';
+import performanceNow from 'fbjs/lib/performanceNow';
+
+/**
+ * A utility for tracking stalls in the JS event loop that prevent timers and
+ * other events from being processed in a timely manner.
+ *
+ * The "stall" time is defined as the amount of time in access of the acceptable
+ * threshold, which is typically around 100-200ms. So if the treshold is set to
+ * 100 and a timer fires 150 ms later than it was scheduled because the event
+ * loop was tied up, that would be considered a 50ms stall.
+ *
+ * By default, logs stall events to the console when installed. Can also be
+ * queried with `getStats`.
+ */
+var JSEventLoopWatchdog = {
+  getStats: function getStats() {
+    return {
+      stallCount: stallCount,
+      totalStallTime: totalStallTime,
+      longestStall: longestStall,
+      acceptableBusyTime: acceptableBusyTime
+    };
+  },
+  reset: function reset() {
+    infoLog('JSEventLoopWatchdog: reset');
+    totalStallTime = 0;
+    stallCount = 0;
+    longestStall = 0;
+    lastInterval = performanceNow();
+  },
+  addHandler: function addHandler(handler) {
+    handlers.push(handler);
+  },
+  install: function install(_ref) {
+    var thresholdMS = _ref.thresholdMS;
+    acceptableBusyTime = thresholdMS;
+
+    if (installed) {
+      return;
+    }
+
+    installed = true;
+    lastInterval = performanceNow();
+
+    function iteration() {
+      var now = performanceNow();
+      var busyTime = now - lastInterval;
+
+      if (busyTime >= thresholdMS) {
+        var stallTime = busyTime - thresholdMS;
+        stallCount++;
+        totalStallTime += stallTime;
+        longestStall = Math.max(longestStall, stallTime);
+        var msg = "JSEventLoopWatchdog: JS thread busy for " + busyTime + "ms. " + (totalStallTime + "ms in " + stallCount + " stalls so far. ");
+        handlers.forEach(function (handler) {
+          msg += handler.onStall({
+            lastInterval: lastInterval,
+            busyTime: busyTime
+          }) || '';
+        });
+        infoLog(msg);
+      }
+
+      handlers.forEach(function (handler) {
+        handler.onIterate && handler.onIterate();
+      });
+      lastInterval = now;
+      setTimeout(iteration, thresholdMS / 5);
+    }
+
+    iteration();
+  }
+};
+var acceptableBusyTime = 0;
+var installed = false;
+var totalStallTime = 0;
+var stallCount = 0;
+var longestStall = 0;
+var lastInterval = 0;
+var handlers = [];
+export default JSEventLoopWatchdog;