refactor(SmartCard): add null object constructor

WE2-716

Signed-off-by: Mart Somermaa <[email protected]>

Author: mrts

include/pcsc-cpp/pcsc-cpp-utils.hpp

@@ -57,3 +57,10 @@ inline std::string removeAbsolutePathPrefix(const std::string& filePath)
 
 #define THROW(ExceptionType, message)                                                              \
     THROW_WITH_CALLER_INFO(ExceptionType, message, __FILE__, __LINE__, __func__)
+
+#define REQUIRE_NON_NULL(val)                                                                      \
+    if (!val) {                                                                                    \
+        throw std::logic_error("Null " + std::string(#val) + " in "                                \
+                               + pcsc_cpp::removeAbsolutePathPrefix(__FILE__) + ':'                \
+                               + std::to_string(__LINE__) + ':' + __func__);                       \
+    }

include/pcsc-cpp/pcsc-cpp.hpp

@@ -207,7 +207,7 @@ constexpr uint8_t PIN_PAD_PIN_ENTRY_TIMEOUT = 90; // 1 minute, 30 seconds
 class SmartCard
 {
 public:
-    enum class Protocol { T0, T1 }; // AUTO = T0 | T1
+    enum class Protocol { UNDEFINED, T0, T1 }; // AUTO = T0 | T1
 
     using ptr = std::unique_ptr<SmartCard>;
 
@@ -229,6 +229,7 @@ class SmartCard
     };
 
     SmartCard(const ContextPtr& context, const string_t& readerName, byte_vector atr);
+    SmartCard(); // Null object constructor.
     ~SmartCard();
 
     // The rule of five.

src/SmartCard.cpp

@@ -273,20 +273,23 @@ SmartCard::SmartCard(const ContextPtr& contex, const string_t& readerName, byte_
     // TODO: debug("Card ATR -> " + bytes2hexstr(atr));
 }
 
+SmartCard::SmartCard() = default;
 SmartCard::~SmartCard() = default;
 
 SmartCard::TransactionGuard SmartCard::beginTransaction()
 {
+    REQUIRE_NON_NULL(card);
     return SmartCard::TransactionGuard {*card, transactionInProgress};
 }
 
 bool SmartCard::readerHasPinPad() const
 {
-    return card->readerHasPinPad();
+    return card ? card->readerHasPinPad() : false;
 }
 
 ResponseApdu SmartCard::transmit(const CommandApdu& command) const
 {
+    REQUIRE_NON_NULL(card);
     if (!transactionInProgress) {
         THROW(std::logic_error, "Call SmartCard::transmit() inside a transaction");
     }
@@ -296,6 +299,7 @@ ResponseApdu SmartCard::transmit(const CommandApdu& command) const
 
 ResponseApdu SmartCard::transmitCTL(const CommandApdu& command, uint16_t lang, uint8_t minlen) const
 {
+    REQUIRE_NON_NULL(card);
     if (!transactionInProgress) {
         THROW(std::logic_error, "Call SmartCard::transmit() inside a transaction");
     }