From c79cc826d7f290cdfecdbd582bfab2639b15912f Mon Sep 17 00:00:00 2001
From: 0xb00bface <0xboobface@gmail.com>
Date: Mon, 28 Dec 2020 17:34:56 +0100
Subject: [PATCH] Improve bandwidth meter performance

---
 .../java/ctbrec/ui/CamrecApplication.java     |  5 +-
 .../main/java/ctbrec/io/BandwidthMeter.java   | 94 +++++++------------
 2 files changed, 37 insertions(+), 62 deletions(-)

diff --git a/client/src/main/java/ctbrec/ui/CamrecApplication.java b/client/src/main/java/ctbrec/ui/CamrecApplication.java
index 1278e97d..a02b75c6 100644
--- a/client/src/main/java/ctbrec/ui/CamrecApplication.java
+++ b/client/src/main/java/ctbrec/ui/CamrecApplication.java
@@ -366,8 +366,9 @@ public class CamrecApplication extends Application {
 
     private void registerBandwidthMeterListener() {
         BandwidthMeter.addListener((bytes, dur) -> {
-            long seconds = dur.getSeconds();
-            bytesPerSecond = bytes / (double)seconds;
+            long millis = dur.toMillis();
+            double bytesPerMilli = bytes / (double)millis;
+            bytesPerSecond = bytesPerMilli * 1000;
             updateStatus();
         });
     }
diff --git a/common/src/main/java/ctbrec/io/BandwidthMeter.java b/common/src/main/java/ctbrec/io/BandwidthMeter.java
index 779556c7..58472330 100644
--- a/common/src/main/java/ctbrec/io/BandwidthMeter.java
+++ b/common/src/main/java/ctbrec/io/BandwidthMeter.java
@@ -3,46 +3,55 @@ package ctbrec.io;
 import java.time.Duration;
 import java.time.Instant;
 import java.util.ArrayList;
-import java.util.Iterator;
 import java.util.List;
-import java.util.concurrent.locks.Lock;
-import java.util.concurrent.locks.ReentrantLock;
 
 public class BandwidthMeter {
 
     public static final Duration MEASURE_TIMEFRAME = Duration.ofSeconds(10);
-    private static List<Record> records = new ArrayList<>(100);
-    private static Lock lock = new ReentrantLock(true);
+    private static long[] records = new long[10000];
+    private static int head = 0;
+    private static int tail = 0;
     private static List<Listener> listeners = new ArrayList<>();
-    private static Instant lastUpdate = Instant.EPOCH;
+    private static long lastUpdate = 0;
+    private static long throughput = 0;
 
     private BandwidthMeter() {
     }
 
-    public static void add(long bytes) {
-        Record r = new Record(bytes);
-        lock.lock();
-        try {
-            records.add(r);
-        } finally {
-            lock.unlock();
-        }
+    public static synchronized void add(long bytes) {
+        int idx = getNextIndex();
+        records[idx] = bytes;
 
-        Instant oneSecondAgo = Instant.now().minus(Duration.ofSeconds(1));
-        if (lastUpdate.isBefore(oneSecondAgo)) {
-            fireEvent(getThroughput(), MEASURE_TIMEFRAME);
-            lastUpdate = Instant.now();
+        if (lastUpdate + 1000 < System.currentTimeMillis()) {
+            Instant last = Instant.ofEpochMilli(lastUpdate);
+            Instant now = Instant.now();
+            Duration d = Duration.between(last, now);
+            calculateThroughput();
+            fireEvent(getThroughput(), d);
         }
     }
 
-    public static void setThroughput(long bytes, Duration d) {
-        lock.lock();
-        try {
-            records.clear();
-            records.add(new Record(bytes));
-        } finally {
-            lock.unlock();
+    private static void calculateThroughput() {
+        throughput = 0;
+        while (tail != head) {
+            throughput += records[tail++];
+            if (tail == records.length) {
+                tail = 0;
+            }
         }
+        lastUpdate = System.currentTimeMillis();
+    }
+
+    private static int getNextIndex() {
+        head++;
+        if(head == records.length) {
+            head = 0;
+        }
+        return head;
+    }
+
+    public static void setThroughput(long bytes, Duration d) {
+        records[0] = bytes;
         fireEvent(bytes, d);
     }
 
@@ -57,31 +66,6 @@ public class BandwidthMeter {
      * @return throughput in bytes
      */
     public static long getThroughput() {
-        return getThroughput(MEASURE_TIMEFRAME);
-    }
-
-    /**
-     * Get the throughput over the given duration
-     * @return throughput in bytes
-     */
-    public static long getThroughput(Duration d) {
-        Instant now = Instant.now();
-        Instant measureStart = now.minus(d);
-        long throughput = 0;
-        lock.lock();
-        try {
-            for (Iterator<Record> iterator = records.iterator(); iterator.hasNext();) {
-                Record record = iterator.next();
-                if (record.timestamp.isBefore(measureStart)) {
-                    iterator.remove();
-                } else {
-                    throughput += record.bytes;
-                }
-            }
-
-        } finally {
-            lock.unlock();
-        }
         return throughput;
     }
 
@@ -93,16 +77,6 @@ public class BandwidthMeter {
         listeners.remove(l);
     }
 
-    private static class Record {
-        public Instant timestamp;
-        public long bytes;
-
-        public Record(long bytes) {
-            timestamp = Instant.now();
-            this.bytes = bytes;
-        }
-    }
-
     @FunctionalInterface
     public static interface Listener {
         void bandwidthCalculated(long bytes, Duration timeframe);