fix: fix Infinity speed that would happen when data was read on same ms

Author: fent

lib/speedometer.js

@@ -8,6 +8,8 @@ module.exports = class Speedometer {
   constructor(per) {
     this.per = per;
     this.lasttime = null;
+    this.lastsize = 0;
+    this.lastlasttime = Date.now();
     this.total = 0;
     this.iteration = 0;
     this.speed = 0;
@@ -30,10 +32,20 @@ module.exports = class Speedometer {
       return;
     }
 
-    // Compare now to last time.
-    const speed = Math.round((data.length / (now - this.lasttime)) *
-                         this.per);
-    this.lasttime = now;
+    let speed;
+    if (now === this.lasttime) {
+      // If more data is read on the same ms, aggregate it.
+      this.lastsize += data.length;
+      speed = this.lastsize / (now - this.lastlasttime);
+
+    } else {
+      // Compare now to last time.
+      speed = data.length / (now - this.lasttime);
+      this.lastsize = data.length;
+      this.lastlasttime = this.lasttime;
+      this.lasttime = now;
+    }
+    speed = Math.round(speed * this.per);
 
     // Get average speed.
     this.total += speed;

test/single-test.js

@@ -93,6 +93,35 @@ describe('Read when stream speed is sporadic', () => {
   });
 });
 
+describe('Data is read on the same millisecond', () => {
+  it('Speed is accurately calculated', (done) => {
+    let clock = sinon.useFakeTimers();
+    after(clock.restore);
+
+    const ss = new StreamSpeed();
+    const rs = new MockStream();
+    ss.add(rs);
+
+    const spy = sinon.spy();
+    ss.on('speed', spy);
+
+    // Write at 2*400 bytes per second.
+    setTimeout(() => {
+      rs.write(Buffer.alloc(400), () => {
+        rs.write(Buffer.alloc(400), () => {
+          process.nextTick(rs.end.bind(rs));
+        });
+      });
+    }, 100);
+    process.nextTick(clock.tick.bind(clock, 100));
+
+    rs.on('end', () => {
+      assert.ok(spy.called);
+      done();
+    });
+  });
+});
+
 describe('Stream being monitored has an error', () => {
   it('Stream gets removed', () => {
     const ss = new StreamSpeed();