support for comparing char8_t with sentinel

Author: hanickadot

include/ctre/utf8.hpp

@@ -33,6 +33,10 @@ struct utf8_iterator {
 		auto operator--(int) noexcept -> self_type;
 		friend auto operator==(self_type, self_type) noexcept -> bool;
 		auto operator*() noexcept -> reference;
+		
+		friend constexpr auto operator==(self_type, const char8_t * ptr) noexcept {
+			return *ptr == char8_t{0};
+		}
 	};
 
 	const char8_t * ptr{nullptr};

single-header/ctre-unicode.hpp

@@ -3057,6 +3057,10 @@ struct utf8_iterator {
 		auto operator--(int) noexcept -> self_type;
 		friend auto operator==(self_type, self_type) noexcept -> bool;
 		auto operator*() noexcept -> reference;
+		
+		friend constexpr auto operator==(self_type, const char8_t * ptr) noexcept {
+			return *ptr == char8_t{0};
+		}
 	};
 
 	const char8_t * ptr{nullptr};

single-header/ctre.hpp

@@ -3054,6 +3054,10 @@ struct utf8_iterator {
 		auto operator--(int) noexcept -> self_type;
 		friend auto operator==(self_type, self_type) noexcept -> bool;
 		auto operator*() noexcept -> reference;
+		
+		friend constexpr auto operator==(self_type, const char8_t * ptr) noexcept {
+			return *ptr == char8_t{0};
+		}
 	};
 
 	const char8_t * ptr{nullptr};

tests/mode.cpp

@@ -41,4 +41,6 @@ static_assert(CTRE_TEST("y(?i)"));
 static_assert(CTRE_TEST("y(?ic)"));
 static_assert(CTRE_TEST("y(?icsm)"));
 
+static_assert(CTRE_TEST("(?i)Tom|Sawyer|Huckleberry|Finn"));
+