Improve unicode support

Author: Julian LALU

interface/core/allocators/memory_allocation.h

@@ -86,8 +86,7 @@ namespace hud
          */
         HD_FORCEINLINE constexpr memory_allocation &operator=(memory_allocation &&other) noexcept
         {
-            if (this != &other) [[likely]]
-            {
+            if (this != &other) [[likely]] {
                 begin_ptr_ = other.begin_ptr_;
                 other.begin_ptr_ = nullptr;
                 end_ptr_ = other.end_ptr_;
@@ -128,13 +127,24 @@ namespace hud
         {
             return begin_ptr_;
         }
+        /** Retrieves a pointer to the beginning of the sequence. */
+        [[nodiscard]] HD_FORCEINLINE constexpr const type_t *data_const() const noexcept
+        {
+            return begin_ptr_;
+        }
 
         /** Retrieves a pointer to the end of the sequence. */
         [[nodiscard]] HD_FORCEINLINE constexpr type_t *data_end() const noexcept
         {
             return end_ptr_;
         }
 
+        /** Retrieves a pointer to the end of the sequence. */
+        [[nodiscard]] HD_FORCEINLINE constexpr const type_t *data_end_const() const noexcept
+        {
+            return end_ptr_;
+        }
+
         /**
          * Retrieves a pointer to the element at the given `index` of the sequence.
          * A special case is allowed when `data_at(count())` is called.
@@ -193,23 +203,40 @@ namespace hud
         }
 
         /** Convert the allocation to a slice. */
-        [[nodiscard]] HD_FORCEINLINE constexpr slice<type_t> to_slice() const noexcept
+        [[nodiscard]] HD_FORCEINLINE constexpr slice<const type_t> as_slice() const noexcept
         {
-            return slice(begin_ptr_, count());
+            return slice(data_const(), count());
+        }
+        /** Convert the allocation to a slice. */
+        [[nodiscard]] HD_FORCEINLINE constexpr slice<type_t> as_slice() noexcept
+        {
+            return slice(data(), count());
         }
 
-        /** Retrieves an iterator_type to the beginning of the slice. */
-        [[nodiscard]] HD_FORCEINLINE constexpr iterator_type begin() const noexcept
+        /** Retrieves an iterator_type to the beginning of the allocation. */
+        [[nodiscard]] HD_FORCEINLINE constexpr iterator_type begin() noexcept
         {
             return iterator_type(begin_ptr_);
         }
 
-        /** Retrieves an iterator_type to the end of the slice. */
-        [[nodiscard]] HD_FORCEINLINE constexpr iterator_type end() const noexcept
+        /** Retrieves an const_iterator_type to the beginning of the allocation. */
+        [[nodiscard]] HD_FORCEINLINE constexpr const_iterator_type begin() const noexcept
+        {
+            return const_iterator_type(begin_ptr_);
+        }
+
+        /** Retrieves an iterator_type to the end of the allocation. */
+        [[nodiscard]] HD_FORCEINLINE constexpr iterator_type end() noexcept
         {
             return iterator_type(end_ptr_);
         }
 
+        /** Retrieves an const_iterator_type to the end of the allocation. */
+        [[nodiscard]] HD_FORCEINLINE constexpr const_iterator_type end() const noexcept
+        {
+            return const_iterator_type(end_ptr_);
+        }
+
     private:
         memory_allocation(const memory_allocation &) = delete;
         memory_allocation &operator=(const memory_allocation &) = delete;

interface/core/character/character.h

@@ -5,32 +5,36 @@ namespace hud
 {
     struct character
     {
-
         static constexpr char8 ANSI_NULL_CHARACTER = '\0';
         static constexpr wchar WIDE_NULL_CHARACTER = L'\0';
+        static constexpr char16 CHAR16_NULL_CHARACTER = u'\0';
+        static constexpr char32 CHAR32_NULL_CHARACTER = U'\0';
 
         /** Check whether the character is a pure ansi character. */
-        static HD_FORCEINLINE constexpr bool is_ascii(const char8 character) noexcept
-        {
-            return (character & 0x80) == 0;
-        }
-
-        /** Check whether the character is a pure ansi character. */
-        static HD_FORCEINLINE constexpr bool is_ascii(const wchar character) noexcept
+        template<typename char_t>
+        requires(hud::is_one_of_types_v<char_t, char8, wchar, char16, char32>)
+        static HD_FORCEINLINE constexpr bool is_ascii(const char_t character) noexcept
         {
             return (character & ~0x7F) == 0;
         }
 
         /** Check whether the character is a null character '\0'. */
-        static HD_FORCEINLINE constexpr bool is_null(const char8 character) noexcept
-        {
-            return character == '\0';
-        }
-
-        /** Check whether the character is a null character '\0'. */
-        static HD_FORCEINLINE constexpr bool is_null(const wchar character) noexcept
-        {
-            return character == L'\0';
+        template<typename char_t>
+        requires hud::is_one_of_types_v<char_t, char8, wchar, char16, char32>
+        static HD_FORCEINLINE constexpr bool is_null(const char_t character) noexcept
+        {
+            if constexpr (std::is_same_v<char_t, char8>) {
+                return character == ANSI_NULL_CHARACTER;
+            }
+            else if constexpr (std::is_same_v<char_t, wchar>) {
+                return character == WIDE_NULL_CHARACTER;
+            }
+            else if constexpr (std::is_same_v<char_t, char16>) {
+                return character == CHAR16_NULL_CHARACTER;
+            }
+            else if constexpr (std::is_same_v<char_t, char32>) {
+                return character == CHAR32_NULL_CHARACTER;
+            }
         }
 
         /**