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src/core/profiler.js

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+/*
+# metrics profiler
+
+## timing
+
+```
+ var timer = Profiler.metric('resource:load')
+ time.start();
+ ...
+ time.end();
+```
+
+## counters
+
+```
+ var counter = Profiler.metric('requests')
+ counter.inc();   // 1
+ counter.inc(10); // 11
+ counter.dec()    // 10
+ counter.dec(10)  // 0
+```
+
+## Calls per second
+```
+  var fps = Profiler.metric('fps')
+  function render() {
+    fps.mark();
+  }
+```
+*/
+var MAX_HISTORY = 1024;
+function Profiler () {}
+Profiler.metrics = {};
+Profiler._backend = null;
+
+Profiler.get = function (name) {
+  return Profiler.metrics[name] || {
+    max: 0,
+    min: Number.MAX_VALUE,
+    avg: 0,
+    total: 0,
+    count: 0,
+    last: 0,
+    history: typeof (Float32Array) !== 'undefined' ? new Float32Array(MAX_HISTORY) : []
+  };
+};
+
+Profiler.backend = function (_) {
+  Profiler._backend = _;
+};
+
+Profiler.new_value = function (name, value, type, defer) {
+  type = type || 'i';
+  var t = Profiler.metrics[name] = Profiler.get(name);
+
+  t.max = Math.max(t.max, value);
+  t.min = Math.min(t.min, value);
+  t.total += value;
+  ++t.count;
+  t.avg = t.total / t.count;
+  t.history[t.count % MAX_HISTORY] = value;
+
+  if (!defer) {
+    Profiler._backend && Profiler._backend([type, name, value]);
+  } else {
+    var n = performance.now();
+    // don't allow to send stats quick
+    if (n - t.last > 1000) {
+      Profiler._backend && Profiler._backend([type, name, t.avg]);
+      t.last = n;
+    }
+  }
+};
+
+Profiler.print_stats = function () {
+  for (var k in Profiler.metrics) {
+    var t = Profiler.metrics[k];
+    console.log(' === ' + k + ' === ');
+    console.log(' max: ' + t.max);
+    console.log(' min: ' + t.min);
+    console.log(' avg: ' + t.avg);
+    console.log(' count: ' + t.count);
+    console.log(' total: ' + t.total);
+  }
+};
+
+function Metric (name) {
+  this.t0 = null;
+  this.name = name;
+  this.count = 0;
+}
+
+Metric.prototype = {
+
+  //
+  // start a time measurement
+  //
+  start: function () {
+    this.t0 = performance.now();
+    return this;
+  },
+
+  // elapsed time since start was called
+  _elapsed: function () {
+    return performance.now() - this.t0;
+  },
+
+  //
+  // finish a time measurement and register it
+  // ``start`` should be called first, if not this
+  // function does not take effect
+  //
+  end: function (defer) {
+    if (this.t0 !== null) {
+      Profiler.new_value(this.name, this._elapsed(), 't', defer);
+      this.t0 = null;
+    }
+  },
+
+  //
+  // increments the value
+  // qty: how many, default = 1
+  //
+  inc: function (qty) {
+    qty = qty === undefined ? 1 : qty;
+    Profiler.new_value(this.name, qty, 'i');
+  },
+
+  //
+  // decrements the value
+  // qty: how many, default = 1
+  //
+  dec: function (qty) {
+    qty = qty === undefined ? 1 : qty;
+    Profiler.new_value(this.name, qty, 'd');
+  },
+
+  //
+  // measures how many times per second this function is called
+  //
+  mark: function () {
+    ++this.count;
+    if (this.t0 === null) {
+      this.start();
+      return;
+    }
+    var elapsed = this._elapsed();
+    if (elapsed > 1) {
+      Profiler.new_value(this.name, this.count);
+      this.count = 0;
+      this.start();
+    }
+  }
+};
+
+Profiler.metric = function (name) {
+  return new Metric(name);
+};
+
+module.exports = Profiler;