TransferPerfCounter made noncopyable, returns counters by references

libuavcan/include/uavcan/transport/perf_counter.hpp

@@ -7,13 +7,14 @@
 
 #include <uavcan/std.hpp>
 #include <uavcan/build_config.hpp>
+#include <uavcan/util/templates.hpp>
 
 namespace uavcan
 {
 
 #if UAVCAN_TINY
 
-class UAVCAN_EXPORT TransferPerfCounter
+class UAVCAN_EXPORT TransferPerfCounter : Noncopyable
 {
 public:
     void addTxTransfer() { }
@@ -27,7 +28,12 @@ public:
 
 #else
 
-class UAVCAN_EXPORT TransferPerfCounter
+/**
+ * The class is declared noncopyable for two reasons:
+ *  - to prevent accidental pass-by-value into a mutator
+ *  - to make the addresses of the counters fixed and exposable to the user of the library
+ */
+class UAVCAN_EXPORT TransferPerfCounter : Noncopyable
 {
     uint64_t transfers_tx_;
     uint64_t transfers_rx_;
@@ -50,9 +56,13 @@ public:
         errors_ += errors;
     }
 
-    uint64_t getTxTransferCount() const { return transfers_tx_; }
-    uint64_t getRxTransferCount() const { return transfers_rx_; }
-    uint64_t getErrorCount() const { return errors_; }
+    /**
+     * Returned references are guaranteed to be valid as long as this instance of Node exists.
+     * This is enforced by virtue of the class being Noncopyable.
+     */
+    const uint64_t& getTxTransferCount() const { return transfers_tx_; }
+    const uint64_t& getRxTransferCount() const { return transfers_rx_; }
+    const uint64_t& getErrorCount() const { return errors_; }
 };
 
 #endif