1 files changed, 39 insertions, 0 deletions
diff --git a/lib/nes/app/input/modifier-mask.hh b/lib/nes/app/input/modifier-mask.hh
new file mode 100644
index 0000000..e18cddb
--- /dev/null
+++ b/lib/nes/app/input/modifier-mask.hh
@@ -0,0 +1,39 @@
+#pragma once
+
+#include "nes/common/types.hh"
+
+namespace nes::app
+{
+	/// Keyboard modifiers.
+	class modifier_mask
+	{
+		u8 raw_value_{ 0 };
+
+	public:
+		constexpr explicit modifier_mask() = default;
+
+		static constexpr auto from_raw_value(u8 const raw_value) -> modifier_mask
+		{
+			return modifier_mask{ raw_value };
+		}
+
+		constexpr auto add(modifier_mask const other) -> void { raw_value_ |= other.raw_value_; }
+		constexpr auto remove(modifier_mask const other) -> void { raw_value_ ^= other.raw_value_; }
+		constexpr auto contains(modifier_mask const other) const -> bool { return (raw_value_ & other.raw_value_) == other.raw_value_; }
+		constexpr auto is_empty() const -> bool { return raw_value_ == 0; }
+		constexpr auto get_raw_value() const -> u8 { return raw_value_; }
+
+	private:
+		constexpr explicit modifier_mask(u8 const raw_value)
+			: raw_value_{ raw_value }
+		{
+		}
+	};
+
+	namespace modifiers
+	{
+		inline constexpr auto control = modifier_mask::from_raw_value(1 << 0);
+		inline constexpr auto shift = modifier_mask::from_raw_value(1 << 1);
+		inline constexpr auto alt = modifier_mask::from_raw_value(1 << 2);
+	} // namespace modifiers
+} // namespace nes::app
+\ No newline at end of file