1 files changed, 53 insertions, 0 deletions
diff --git a/src/openvic-dataloader/detail/DetectUtf8.hpp b/src/openvic-dataloader/detail/DetectUtf8.hpp
new file mode 100644
index 0000000..2045b3c
--- /dev/null
+++ b/src/openvic-dataloader/detail/DetectUtf8.hpp
@@ -0,0 +1,53 @@
+#pragma once
+
+#include <lexy/action/match.hpp>
+#include <lexy/dsl.hpp>
+
+#include "detail/LexyLitRange.hpp"
+
+namespace ovdl::detail {
+	namespace detect_utf8 {
+
+		template<bool INCLUDE_ASCII>
+		struct DetectUtf8 {
+			struct not_utf8 {
+				static constexpr auto name = "not utf8";
+			};
+
+			static constexpr auto rule = [] {
+				constexpr auto is_not_ascii_flag = lexy::dsl::context_flag<DetectUtf8>;
+
+				// & 0b10000000 == 0b00000000
+				constexpr auto ascii_values = lexydsl::make_range<0b00000000, 0b01111111>();
+				// & 0b11100000 == 0b11000000
+				constexpr auto two_byte = lexydsl::make_range<0b11000000, 0b11011111>();
+				// & 0b11110000 == 0b11100000
+				constexpr auto three_byte = lexydsl::make_range<0b11100000, 0b11101111>();
+				// & 0b11111000 == 0b11110000
+				constexpr auto four_byte = lexydsl::make_range<0b11110000, 0b11110111>();
+				// & 0b11000000 == 0b10000000
+				constexpr auto check_bytes = lexydsl::make_range<0b10000000, 0b10111111>();
+
+				constexpr auto utf8_check =
+					((four_byte >> lexy::dsl::times<3>(check_bytes)) |
+						(three_byte >> lexy::dsl::times<2>(check_bytes)) |
+						(two_byte >> lexy::dsl::times<1>(check_bytes))) >>
+					is_not_ascii_flag.set();
+
+				return is_not_ascii_flag.template create<INCLUDE_ASCII>() +
+					   lexy::dsl::while_(utf8_check | ascii_values) +
+					   lexy::dsl::must(is_not_ascii_flag.is_set()).template error<not_utf8>;
+			}();
+		};
+	}
+
+	template<typename Input>
+	constexpr bool is_utf8_no_ascii(const Input& input) {
+		return lexy::match<detect_utf8::DetectUtf8<false>>(input);
+	}
+
+	template<typename Input>
+	constexpr bool is_utf8(const Input& input) {
+		return lexy::match<detect_utf8::DetectUtf8<true>>(input);
+	}
+}
+\ No newline at end of file