Verify register and mask parameters

funreg.hpp

@@ -14,17 +14,29 @@
  */
 #define FUNREG_ENABLE_EXTERNAL_IO
 
+/**
+ * Comment to disable compile-time error checks, which are mostly concepts
+ * to verify proper library usage.
+ */
+#define FUNREG_ENABLE_ERROR_CHECKS
+
 #include <stdint.h>
 
 #ifdef FUNREG_ENABLE_EXTERNAL_IO
 #include <type_traits>
 #endif
 
+#ifdef FUNREG_ENABLE_ERROR_CHECKS
+#include <concepts>
+#endif
+
 namespace fr {
 
 // A utility to measure a bit-mask's offset from bit zero.
 template<auto Mask, unsigned int N = 0>
-constexpr auto BitOffset = []() constexpr {
+requires(std::unsigned_integral<decltype(Mask)> &&
+         (N < 8 * sizeof(Mask)))
+constexpr auto BitOffset = []() constexpr -> unsigned int {
     if constexpr (Mask & 1)
         return N;
     else
@@ -41,6 +53,7 @@ constexpr auto BitOffset = []() constexpr {
  * structure as a template.
  */
 template<typename T, uintptr_t Addr>
+requires(std::unsigned_integral<T>)
 struct MemoryIO {
     using type = T;
     constexpr static auto addr = Addr;
@@ -60,6 +73,54 @@ struct MemoryIO {
     }
 };
 
+template<typename T>
+concept IsAccess = requires(typename T::type x) {
+    requires std::same_as<decltype(T::addr), const uintptr_t>;
+    {T::read()} -> std::same_as<typename T::type>;
+    {T::write(x)} -> std::same_as<void>;
+};
+
+#ifdef FUNREG_ENABLE_EXTERNAL_IO
+template<typename Access>
+requires IsAccess<Access>
+struct Register;
+
+template<typename T>
+concept IsRegister =
+    IsAccess<typename T::access> &&
+    std::same_as<T, Register<typename T::access>>;
+#else
+template<typename T, uintptr_t Addr>
+requires(std::unsigned_integral<T>)
+class Register;
+
+template<typename T>
+concept IsRegister =
+    std::unsigned_integral<typename T::type> &&
+    IsAccess<typename T::Access>;
+#endif
+
+template<typename Reg, typename Reg::type Mask>
+requires IsRegister<Reg>
+struct RegisterMask;
+
+template<typename T>
+concept IsRegisterMask =
+    IsRegister<typename T::reg> &&
+    std::same_as<T, RegisterMask<typename T::reg, T::mask>>;
+
+template<typename M, typename R>
+concept UsesRegister =
+    IsRegisterMask<M> &&
+    IsRegister<R> &&
+    std::same_as<typename M::reg, R>;
+
+template<typename M, typename... Rs>
+concept UsesSomeRegister =
+    IsRegisterMask<M> &&
+    (IsRegister<Rs>, ...) &&
+    (std::same_as<typename M::reg, Rs> || ...);
+
 /**
  * @struct Register
  * @brief  Defines a register, given how to access it.
@@ -70,16 +131,22 @@ struct MemoryIO {
  */
 #ifdef FUNREG_ENABLE_EXTERNAL_IO
 template<typename Access>
-struct Register {
+requires IsAccess<Access>
+class Register {
+public:
     using access = Access;
     using T = typename Access::type;
     constexpr static auto Addr = Access::addr;
 #else
 template<typename T, uintptr_t Addr>
-struct Register {
-    using RegAccess = MemoryIO<T, Addr>;
+requires(std::unsigned_integral<T>)
+class Register {
+public:
+    using Access = MemoryIO<T, Addr>;
 #endif // FUNREG_ENABLE_EXTERNAL_IO
 
+    using type = T;
+
     /**
      * Gets a pointer to the register.
      */
@@ -98,6 +165,8 @@ struct Register {
      * Sets register bits to '1' according to the given RegisterMasks.
      */
     template<typename... Masks>
+    requires((IsRegisterMask<Masks>, ...) &&
+             (UsesRegister<Masks, Register<Access>>, ...))
     static void set() {
         apply<Masks...>([](auto r, auto m) { return r | m; });
     }
@@ -113,6 +182,8 @@ struct Register {
      * Clears register bits to '0' according to the given RegisterMasks.
      */
     template<typename... Masks>
+    requires((IsRegisterMask<Masks>, ...) &&
+             (UsesRegister<Masks, Register<Access>>, ...))
     static void clear() {
         apply<Masks...>([](auto r, auto m) { return r & ~m; });
     }
@@ -128,6 +199,8 @@ struct Register {
      * Toggles bits in the register according to the given RegisterMasks.
      */
     template<typename... Masks>
+    requires((IsRegisterMask<Masks>, ...) &&
+             (UsesRegister<Masks, Register<Access>>, ...))
     static void toggle() {
         apply<Masks...>([](auto r, auto m) { return r ^m; });
     }
@@ -145,6 +218,8 @@ struct Register {
      * If no masks are given, all register bits are returned.
      */
     template<typename... Masks>
+    requires((IsRegisterMask<Masks>, ...) &&
+             (UsesRegister<Masks, Register<Access>>, ...))
     static auto read() {
         if constexpr (sizeof...(Masks) > 0)
             return read() & mergeMasks<Masks...>();
@@ -157,6 +232,8 @@ struct Register {
      * If no masks are given, tests if the register has a non-zero value.
      */
     template<typename... Masks>
+    requires((IsRegisterMask<Masks>, ...) &&
+             (UsesRegister<Masks, Register<Access>>, ...))
     static bool test() {
         if constexpr (sizeof...(Masks) > 0) {
             auto mask = mergeMasks<Masks...>();
@@ -185,16 +262,16 @@ struct Register {
         }
     }
 
-    // Below is meant for internal use only.
-
+    // Internal use only.
     // Applies bit-masks to the register through the provided function.
-    // The provided function receives a pointer to the register's data and a
-    // bit-mask created by merging all provided bit-masks.
+    // All masks meant for this register are merged together; then, `fn`
+    // will receive the register's current value and the mask to carry out
+    // the operation. The result is written back to the register.
     // If no masks are given, a mask selecting all bits is used.
     template<typename... Masks>
-    static void apply(auto fn) {
+    constexpr static void apply(auto fn) {
         if constexpr (sizeof...(Masks) > 0) {
-            auto mask = mergeMasks<Masks...>();
+            constexpr auto mask = mergeMasks<Masks...>();
             if constexpr (mask)
                 write(fn(read(), mask));
         } else {
@@ -202,10 +279,11 @@ struct Register {
         }
     }
 
+private:
     // Takes a list of bit-masks, and returns a merged mask of those which are
     // meant for this register.
     template<typename... Masks>
-    static auto mergeMasks() {
+    constexpr static auto mergeMasks() {
         if constexpr (sizeof...(Masks) > 0) {
             if constexpr ((isThis<typename Masks::reg> | ...)) {
                 auto mask =
@@ -224,20 +302,20 @@ struct Register {
 #ifdef FUNREG_ENABLE_EXTERNAL_IO
     // Determines if the given register matches this one.
     template<typename Reg>
+    requires(IsRegister<Reg>)
     constexpr static bool isThis = [] {
         return std::is_same_v<typename Reg::access, access> && Addr == Reg::Addr;
     }();
 #else
     // Determines if the given register matches this one.
     template<typename Reg>
+    requires(IsRegister<Reg>)
     constexpr static bool isThis = [] {
         return Addr == Reg::Addr;
     }();
 #endif // FUNREG_ENABLE_EXTERNAL_IO
 
     Register() = delete;
-
-    using type = T;
 };
 
 /**
@@ -251,6 +329,7 @@ struct Register {
  *     using LED_RED = RegisterMask<GPIO_OUT, (1 << 2)>;
  */
 template<typename Reg, typename Reg::type Mask>
+requires IsRegister<Reg>
 struct RegisterMask
 {
     using T = typename Reg::type;
@@ -373,6 +452,7 @@ struct RegisterMask
  * @tparam value The value to be used for the given Mask.
  */
 template<typename Mask, Mask::T value>
+requires(IsRegisterMask<Mask>)
 struct RegisterMaskValue
 {
     /**
@@ -406,6 +486,7 @@ struct RegisterMaskValue
  * each register.
  */
 template<typename... Registers>
+requires(IsRegister<Registers>, ...)
 class RegisterGroup
 {
 public:
@@ -415,6 +496,8 @@ public:
      * only written once.
      */
     template<typename... Masks>
+    requires((IsRegisterMask<Masks>, ...) &&
+             (UsesSomeRegister<Masks, Registers...>, ...))
     static void set() {
         apply<Masks...>([](auto r, auto m) { return r | m; });
     }
@@ -425,6 +508,8 @@ public:
      * Only reads and writes each register once; see set().
      */
     template<typename... Masks>
+    requires((IsRegisterMask<Masks>, ...) &&
+             (UsesSomeRegister<Masks, Registers...>, ...))
     static void clear() {
         apply<Masks...>([](auto r, auto m) { return r & ~m; });
     }
@@ -435,6 +520,8 @@ public:
      * Only reads and writes each register once; see set().
      */
     template<typename... Masks>
+    requires((IsRegisterMask<Masks>, ...) &&
+             (UsesSomeRegister<Masks, Registers...>, ...))
     static void toggle() {
         apply<Masks...>([](auto r, auto m) { return r ^ m; });
     }
@@ -453,6 +540,8 @@ public:
 
 private:
     template<typename... Masks>
+    requires((IsRegisterMask<Masks>, ...) &&
+             (UsesSomeRegister<Masks, Registers...>, ...))
     static void apply(auto fn) {
         (Registers::template apply<Masks...>(fn), ...);
     }
@@ -465,6 +554,7 @@ private:
  * register.
  */
 template<typename... RegMasks>
+requires(IsRegisterMask<RegMasks>, ...)
 constexpr auto Masks = (RegMasks::mask | ...);
 
 #ifdef FUNREG_ENABLE_EXTERNAL_IO
@@ -501,4 +591,3 @@ using MemRegister = Register<T, Addr>;
 } // namespace fr
 
 #endif // FUNCTIONAL_REGISTER_IO_H
-