Update IXExponentialBackoffTest.cpp

ixwebsocket/IXExponentialBackoff.cpp

@@ -14,14 +14,27 @@ namespace ix
                                             uint32_t maxWaitBetweenReconnectionRetries,
                                             uint32_t minWaitBetweenReconnectionRetries)
     {
-        uint32_t waitTime = (retryCount < 26) ? (std::pow(2, retryCount) * 100) : 0;
+        // It's easy with a power function to go beyond 2^32, and then 
+        // have unexpected results, so prepare for that
+        const uint32_t maxRetryCountWithoutOverflow = 26;
+
+        uint32_t waitTime = 0;
+        if (retryCount < maxRetryCountWithoutOverflow)
+        {
+            waitTime = std::pow(2, retryCount) * 100;
+        }
 
         if (waitTime < minWaitBetweenReconnectionRetries)
         {
             waitTime = minWaitBetweenReconnectionRetries;
         }
 
-        if (waitTime > maxWaitBetweenReconnectionRetries || waitTime == 0)
+        if (waitTime > maxWaitBetweenReconnectionRetries)
+        {
+            waitTime = maxWaitBetweenReconnectionRetries;
+        }
+
+        if (retryCount >= maxRetryCountWithoutOverflow)
         {
             waitTime = maxWaitBetweenReconnectionRetries;
         }

test/CMakeLists.txt

@@ -23,6 +23,7 @@ set (TEST_TARGET_NAMES
   IXWebSocketSubProtocolTest
   # IXWebSocketBroadcastTest ## FIXME was depending on cobra / take a broadcast server from ws
   IXStrCaseCompareTest
+  IXExponentialBackoffTest
 )
 
 # Some unittest don't work on windows yet

test/IXExponentialBackoffTest.cpp

@@ -0,0 +1,39 @@
+/*
+ *  IXExponentialBackoffTest.cpp
+ *  Author: Benjamin Sergeant
+ *  Copyright (c) 2022 Machine Zone. All rights reserved.
+ */
+
+#include "IXTest.h"
+#include "catch.hpp"
+#include <iostream>
+#include <ixwebsocket/IXExponentialBackoff.h>
+#include <string.h>
+
+using namespace ix;
+
+namespace ix
+{
+    TEST_CASE("exponential_backoff", "[exponential_backoff]")
+    {
+        SECTION("1")
+        {
+            // First parameter is retrycount
+            REQUIRE(calculateRetryWaitMilliseconds(0, 10000, 100) == 100);
+            REQUIRE(calculateRetryWaitMilliseconds(1, 10000, 100) == 200);
+            REQUIRE(calculateRetryWaitMilliseconds(2, 10000, 100) == 400);
+            REQUIRE(calculateRetryWaitMilliseconds(3, 10000, 100) == 800);
+            REQUIRE(calculateRetryWaitMilliseconds(4, 10000, 100) == 1600);
+            REQUIRE(calculateRetryWaitMilliseconds(5, 10000, 100) == 3200);
+            REQUIRE(calculateRetryWaitMilliseconds(6, 10000, 100) == 6400);
+            REQUIRE(calculateRetryWaitMilliseconds(20, 10000, 100) == 10000);
+            REQUIRE(calculateRetryWaitMilliseconds(25, 10000, 100) == 10000);
+            
+            // Things get special after 26 retries
+            REQUIRE(calculateRetryWaitMilliseconds(26, 10000, 100) == 10000);
+            REQUIRE(calculateRetryWaitMilliseconds(27, 10000, 100) == 10000);
+            REQUIRE(calculateRetryWaitMilliseconds(27, 10000, 100) == 10000);
+        }
+    }
+
+} // namespace ix