1 files changed, 49 insertions, 0 deletions
diff --git a/src/square.c b/src/square.c
new file mode 100644
index 0000000..8aef283
--- /dev/null
+++ b/src/square.c
@@ -0,0 +1,49 @@
+#include <stdlib.h>
+#include <stddef.h>
+#include "square.h"
+
+struct square
+{
+    double width;
+};
+
+/* Shape interface */
+
+double shape_area_impl(struct shape *shape)
+{
+    struct square *square = ((void *)shape) + shape_sizeof();
+    return square_area(square);
+}
+
+void shape_destroy_impl(struct shape *shape)
+{
+    struct square *square = ((void *)shape) + shape_sizeof();
+    square_destroy(square);
+}
+
+struct shape *square_as_shape(struct square *square)
+{
+    return ((void *)square) - shape_sizeof();
+}
+
+/* End of shape interface */
+
+struct square *square_create(double width)
+{
+    struct shape *shape = malloc(shape_sizeof() + sizeof(struct square));
+    struct square *square = ((void *)shape) + shape_sizeof();
+    square->width = width;
+
+    shape_init(shape, shape_area_impl, shape_destroy_impl);
+    return square;
+}
+
+double square_area(struct square *square)
+{
+    return square->width * square->width;
+}
+
+void square_destroy(struct square *square)
+{
+    free(((void *)square) - shape_sizeof());
+}
+\ No newline at end of file