add mask

src/mask.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <cstdint>
+#include <vector>
+
+namespace freling {
+
+struct Mask {
+    uint32_t width;
+    uint32_t height;
+    std::vector<bool> data;  // std::vector is specialized for bool
+
+    Mask(uint32_t width, uint32_t height);
+
+    void fill(bool b);
+    void set(int x, int y, bool b);
+    bool get(int x, int y);
+};
+
+}  // namespace freling