Template NoteTxn Singleton make_ function

Author: zfields

src/NoteTxn.hpp

@@ -7,12 +7,6 @@
 class NoteTxn
 {
 public:
-    /**************************************************************************/
-    /*!
-        @brief  Type used to abstract specific hardware implementation types.
-    */
-    /**************************************************************************/
-    typedef void * param_t;
 
     virtual ~NoteTxn(void) {}
 
@@ -44,8 +38,7 @@ class NoteTxn
                the platform specific transaction implementation.
 */
 /******************************************************************************/
-NoteTxn * make_note_txn (
-    NoteTxn::param_t txn_parameters
-);
+template<typename T> NoteTxn * make_note_txn (T & txn_parameters);
+NoteTxn * make_note_txn (nullptr_t);
 
 #endif // NOTE_TXN_HPP

src/NoteTxn_Arduino.cpp

@@ -7,21 +7,43 @@
   #include "mock/mock-parameters.hpp"
 #endif
 
+// Singleton instance of the NoteTxn_Arduino class
+namespace instance {
+    inline NoteTxn* & note_txn (void) {
+        static NoteTxn* note_txn = nullptr;
+        return note_txn;
+    }
+};
+
 NoteTxn *
 make_note_txn (
-    NoteTxn::param_t txn_parameters_
-)
-{
-    static NoteTxn * note_txn = nullptr;
-    if (!txn_parameters_) {
+    nullptr_t
+) {
+    NoteTxn* & note_txn = instance::note_txn();
+    if (note_txn) {
+        delete note_txn;
+        note_txn = nullptr;
+    }
+    return note_txn;
+}
+
+template <typename T>
+NoteTxn *
+make_note_txn (
+    T & txn_pins_
+) {
+    NoteTxn* & note_txn = instance::note_txn();
+
+    if (txn_pins_[0] == txn_pins_[1]) {
+        // Invalid tuple invokes deletion
         if (note_txn) {
             delete note_txn;
             note_txn = nullptr;
         }
     } else if (!note_txn) {
-        const uint8_t * txn_pins = reinterpret_cast<uint8_t *>(txn_parameters_);
-        note_txn = new NoteTxn_Arduino(txn_pins[0], txn_pins[1]);
+        note_txn = new NoteTxn_Arduino(txn_pins_[0], txn_pins_[1]);
     }
+
     return note_txn;
 }
 
@@ -80,3 +102,7 @@ NoteTxn_Arduino::stop (
     // Float RTX pin
     ::pinMode(_rtx_pin, INPUT);
 }
+
+// Explicitly instantiate the template function for array types
+template NoteTxn * make_note_txn<uint8_t[2]>(uint8_t(&)[2]);
+template NoteTxn * make_note_txn<const uint8_t[2]>(const uint8_t(&)[2]);

test/NoteTxn_Arduino.test.cpp

@@ -16,7 +16,7 @@ int test_make_note_txn_instantiates_notetxn_object()
   uint8_t txn_pins[2] = {19, 79};
 
   // Action
-  notetxn = make_note_txn(reinterpret_cast<NoteTxn::param_t>(txn_pins));
+  notetxn = make_note_txn(txn_pins);
 
   // Assert
   if (nullptr != notetxn)
@@ -32,7 +32,8 @@ int test_make_note_txn_instantiates_notetxn_object()
   }
 
   // Clean-up
-  make_note_txn(nullptr);
+  uint8_t invalid_pins[2] = {0};
+  make_note_txn(invalid_pins);
 
   return result;
 }
@@ -43,11 +44,11 @@ int test_make_note_txn_enforces_singleton_by_returning_same_notetxn_object_for_a
 
   // Arrange
   uint8_t txn_pins_1[2] = {19, 79};
-  NoteTxn * const notetxn_1 = make_note_txn(reinterpret_cast<NoteTxn::param_t>(txn_pins_1));
+  NoteTxn * const notetxn_1 = make_note_txn(txn_pins_1);
 
   // Action
   uint8_t txn_pins_2[2] = {9, 17};
-  NoteTxn * const notetxn_2 = make_note_txn(reinterpret_cast<NoteTxn::param_t>(txn_pins_2));
+  NoteTxn * const notetxn_2 = make_note_txn(txn_pins_2);
 
   // Assert
   if (notetxn_1 == notetxn_2)
@@ -63,23 +64,25 @@ int test_make_note_txn_enforces_singleton_by_returning_same_notetxn_object_for_a
   }
 
   // Clean-up
-  make_note_txn(nullptr);
+  uint8_t invalid_pins[2] = {0};
+  make_note_txn(invalid_pins);
 
   return result;
 }
 
-//int test_make_note_txn_returns_nullptr_when_nullptr_is_passed_as_parameter()
-int test_make_note_txn_deletes_singleton_when_nullptr_is_passed_as_parameter()
+//int test_make_note_txn_returns_nullptr_when_same_pins_are_passed_as_parameter()
+int test_make_note_txn_deletes_singleton_when_same_pins_are_passed_as_parameter()
 {
   int result;
 
   // Arrange
   uint8_t txn_pins[2] = {19, 79};
-  NoteTxn * notetxn = make_note_txn(reinterpret_cast<NoteTxn::param_t>(txn_pins));
+  NoteTxn * notetxn = make_note_txn(txn_pins);
   assert(notetxn);
 
   // Action
-  notetxn = make_note_txn(nullptr);
+  uint8_t invalid_pins[2] = {0};
+  notetxn = make_note_txn(invalid_pins);
 
   // Assert
   if (nullptr == notetxn)
@@ -605,7 +608,7 @@ int main(void)
   TestFunction tests[] = {
       {test_make_note_txn_instantiates_notetxn_object, "test_make_note_txn_instantiates_notetxn_object"},
       {test_make_note_txn_enforces_singleton_by_returning_same_notetxn_object_for_all_calls, "test_make_note_txn_enforces_singleton_by_returning_same_notetxn_object_for_all_calls"},
-      {test_make_note_txn_deletes_singleton_when_nullptr_is_passed_as_parameter, "test_make_note_txn_deletes_singleton_when_nullptr_is_passed_as_parameter"},
+      {test_make_note_txn_deletes_singleton_when_same_pins_are_passed_as_parameter, "test_make_note_txn_deletes_singleton_when_same_pins_are_passed_as_parameter"},
       {test_notetxn_arduino_constructor_floats_ctx_pin, "test_notetxn_arduino_constructor_floats_ctx_pin"},
       {test_notetxn_arduino_constructor_floats_rtx_pin, "test_notetxn_arduino_constructor_floats_rtx_pin"},
       {test_notetxn_arduino_start_initially_configures_ctx_pin_as_input_pullup, "test_notetxn_arduino_start_initially_configures_ctx_pin_as_input_pullup"},

test/mock/NoteTxn_Mock.cpp

@@ -1,12 +1,26 @@
 #include "mock/NoteTxn_Mock.hpp"
 
-MakeNoteTxn_Parameters make_note_txn_Parameters;
+MakeNoteTxn_Parameters<const uint8_t [2]> make_note_txn_Parameters;
 NoteTxnStart_Parameters noteTxnStart_Parameters;
 NoteTxnStop_Parameters noteTxnStop_Parameters;
 
 NoteTxn *
 make_note_txn (
-    NoteTxn::param_t txn_parameters_
+    nullptr_t
+) {
+    // Record invocation(s)
+    ++make_note_txn_Parameters.invoked;
+
+    // Stash parameter(s)
+
+    // Return user-supplied result
+    return make_note_txn_Parameters.result;
+}
+
+template <typename T>
+NoteTxn *
+make_note_txn (
+    T & txn_parameters_
 )
 {
     // Record invocation(s)

test/mock/NoteTxn_Mock.hpp

@@ -13,12 +13,13 @@ class NoteTxn_Mock final : public NoteTxn
     void stop (void) override;
 };
 
+template <typename T>
 struct MakeNoteTxn_Parameters {
     MakeNoteTxn_Parameters(
         void
     ) :
         invoked(0),
-        txn_parameters(nullptr),
+        txn_parameters{0, 0},
         result(nullptr)
     { }
     void reset (
@@ -29,7 +30,7 @@ struct MakeNoteTxn_Parameters {
         result = nullptr;
     }
     size_t invoked;
-    NoteTxn::param_t txn_parameters;
+    T txn_parameters;
     NoteTxn * result;
 };
 
@@ -67,7 +68,7 @@ struct NoteTxnStop_Parameters {
     size_t invoked;
 };
 
-extern MakeNoteTxn_Parameters make_note_txn_Parameters;
+extern MakeNoteTxn_Parameters<const uint8_t [2]> make_note_txn_Parameters;
 extern NoteTxnStart_Parameters noteTxnStart_Parameters;
 extern NoteTxnStop_Parameters noteTxnStop_Parameters;