ioc: add instance counter tools to IOC shell

ioc/iochooks.cpp

@@ -128,6 +128,79 @@ void pvxsi() {
     }
 }
 
+namespace {
+
+void pvxrefshow() {
+    auto refs(instanceSnapshot());
+    for(auto& pair : refs) {
+        if(pair.second>0u)
+            printf("%s\t= %zu\n", pair.first.c_str(), pair.second);
+    }
+}
+
+struct RefTrack {
+    epicsMutex lock;
+    std::map<std::string, size_t> refs;
+} *refTrack;
+
+epicsThreadOnceId refSavedOnce = EPICS_THREAD_ONCE_INIT;
+
+void refSavedInit(void *) {
+    refTrack = new RefTrack();
+}
+
+void pvxrefsave() {
+    epicsThreadOnce(&refSavedOnce, &refSavedInit, nullptr);
+    epicsGuard<epicsMutex> G(refTrack->lock);
+    refTrack->refs = instanceSnapshot();
+}
+
+void pvxrefdiff() {
+    auto cur(instanceSnapshot());
+    std::map<std::string, int64_t> diff;
+
+    epicsThreadOnce(&refSavedOnce, &refSavedInit, nullptr);
+    {
+        epicsGuard<epicsMutex> G(refTrack->lock);
+
+        auto& prev(refTrack->refs);
+
+        // Both std::map will iterate in the same order.  So co-iterate.
+        // Some keys may appear in one but not the other.
+        auto itC = cur.begin();
+        auto itP = prev.begin();
+        while(true) {
+            bool haveC = itC!=cur.end();
+            bool haveP = itP!=prev.end();
+            int ord = haveC && haveP ? itC->first.compare(itP->first) : 0;
+
+            if(haveC && haveP && ord==0) {
+                diff[itC->first] = int64_t(itC->second) - int64_t(itP->second);
+                ++itC;
+                ++itP;
+
+            } else if(haveP && (!haveC || ord > 0)) { // !cur || cur > prev
+                diff[itP->first] = -int64_t(itP->second);
+                ++itP;
+
+            } else if(haveC && (!haveP || ord < 0)) { // !prev || cur < prev
+                diff[itC->first] = int64_t(itC->second);
+                ++itC;
+
+            } else {
+                break;
+            }
+        }
+    }
+
+    for(auto& pair : diff) {
+        if(pair.second!=0u)
+            printf("%s\t= %lld\n", pair.first.c_str(), (long long)pair.second);
+    }
+}
+
+} // namespace
+
 /**
  * Initialise and control state of pvxs ioc server instance in response to iocInitHook events.
  * Installed on the initHookState hook this function will respond to the following events:
@@ -219,6 +292,13 @@ void pvxsBaseRegistrar() {
                 .implementation<&pvxsr>();
         IOCShCommand<>("pvxsi", "Show detailed server information\n").implementation<&pvxsi>();
 
+        IOCShCommand<>("pvxrefshow",
+                       "Show instance counts for various internal data structures.\n").implementation<&pvxrefshow>();
+        IOCShCommand<>("pvxrefsave",
+                       "Save the current set of instance counters for reference by later pvxrefdiff.\n").implementation<&pvxrefsave>();
+        IOCShCommand<>("pvxrefdiff",
+                       "Show different of current instance counts with those when pvxrefsave was called.\n").implementation<&pvxrefdiff>();
+
         // Initialise the PVXS Server
         initialisePvxsServer();