MbedCRC: improve default constructors

Original default constructor implementation wasn't quite working
properly; it didn't cope with the new "mode_limit" parameter.

Change mechanism so that this now works:

    MbedCRC<POLY32_BIT_ANSI_CRC, 32, CrcMode::TABLE> crc;

Author: kjbracey

TESTS/mbed_drivers/crc/main.cpp

@@ -143,6 +143,28 @@ void test_partial_crc()
     }
 }
 
+void test_mode_limit()
+{
+    const char test[] = "123456789";
+    uint32_t crc;
+
+    {
+        MbedCRC<POLY_32BIT_ANSI, 32, CrcMode::BITWISE> ct;
+        TEST_ASSERT_EQUAL(0, ct.compute(test, strlen(test), &crc));
+        TEST_ASSERT_EQUAL(0xCBF43926, crc);
+    }
+    {
+        MbedCRC<POLY_32BIT_ANSI, 32, CrcMode::TABLE> ct;
+        TEST_ASSERT_EQUAL(0, ct.compute(test, strlen(test), &crc));
+        TEST_ASSERT_EQUAL(0xCBF43926, crc);
+    }
+    {
+        MbedCRC<POLY_32BIT_ANSI, 32, CrcMode::HARDWARE> ct;
+        TEST_ASSERT_EQUAL(0, ct.compute(test, strlen(test), &crc));
+        TEST_ASSERT_EQUAL(0xCBF43926, crc);
+    }
+}
+
 void test_sd_crc()
 {
     MbedCRC<POLY_7BIT_SD, 7> crc7;
@@ -232,6 +254,7 @@ void test_thread_safety()
 Case cases[] = {
     Case("Test supported polynomials", test_supported_polynomials),
     Case("Test partial CRC", test_partial_crc),
+    Case("Test mode-limited CRC", test_mode_limit),
     Case("Test SD CRC polynomials", test_sd_crc),
 #if defined(MBED_CONF_RTOS_PRESENT)
     Case("Test thread safety", test_thread_safety),

drivers/MbedCRC.h

@@ -186,8 +186,34 @@ class MbedCRC  {
     {
     }
 
-    constexpr
-    MbedCRC();
+    /* Default values for different types of polynomials
+    */
+    // *INDENT-OFF*
+    template<uint32_t poly = polynomial, std::enable_if_t<poly == POLY_32BIT_ANSI && width == 32, int> = 0>
+    constexpr MbedCRC() : MbedCRC(0xFFFFFFFF, 0xFFFFFFFF, true, true)
+    {
+    }
+
+    template<uint32_t poly = polynomial, std::enable_if_t<poly == POLY_16BIT_IBM && width == 16, int> = 0>
+    constexpr MbedCRC() : MbedCRC(0, 0, true, true)
+    {
+    }
+
+    template<uint32_t poly = polynomial, std::enable_if_t<poly == POLY_16BIT_CCITT && width == 16, int> = 0>
+    constexpr MbedCRC() : MbedCRC(0xFFFF, 0, false, false)
+    {
+    }
+
+    template<uint32_t poly = polynomial, std::enable_if_t<poly == POLY_7BIT_SD && width == 7, int> = 0>
+    constexpr MbedCRC() : MbedCRC(0, 0, false, false)
+    {
+    }
+
+    template<uint32_t poly = polynomial, std::enable_if_t<poly == POLY_8BIT_CCITT && width == 8, int> = 0>
+    constexpr MbedCRC() : MbedCRC(0, 0, false, false)
+    {
+    }
+    // *INDENT-ON*
 
     /** Compute CRC for the data input
      *  Compute CRC performs the initialization, computation and collection of
@@ -842,38 +868,6 @@ const uint32_t MbedCRC<POLY_32BIT_ANSI, 32, CrcMode::TABLE>::_crc_table[MBED_CRC
 
 #endif // !defined(DOXYGEN_ONLY)
 
-/* Default values for different types of polynomials
-*/
-template<>
-inline MSTD_CONSTEXPR_FN_14
-MbedCRC<POLY_32BIT_ANSI, 32>::MbedCRC() : MbedCRC(0xFFFFFFFF, 0xFFFFFFFF, true, true)
-{
-}
-
-template<>
-inline MSTD_CONSTEXPR_FN_14
-MbedCRC<POLY_16BIT_IBM, 16>::MbedCRC() : MbedCRC(0, 0, true, true)
-{
-}
-
-template<>
-inline MSTD_CONSTEXPR_FN_14
-MbedCRC<POLY_16BIT_CCITT, 16>::MbedCRC() : MbedCRC(0xFFFF, 0, false, false)
-{
-}
-
-template<>
-inline MSTD_CONSTEXPR_FN_14
-MbedCRC<POLY_7BIT_SD, 7>::MbedCRC(): MbedCRC(0, 0, false, false)
-{
-}
-
-template<>
-inline MSTD_CONSTEXPR_FN_14
-MbedCRC<POLY_8BIT_CCITT, 8>::MbedCRC(): MbedCRC(0, 0, false, false)
-{
-}
-
 /** @}*/
 /** @}*/