(main~>lib.h)+header for data structures,~migrate lib.h

+some file handlers for writing and reading (may help with very large
renders by doing them piecemeal when I can)

lib.h

@@ -0,0 +1,22 @@
+#ifndef LIB_H
+#define LIB_H
+
+#include <stdbool.h>
+#include <stdlib.h>
+
+typedef struct State
+{
+  // Sandpiles
+  unsigned char *data;
+  size_t dwidth;
+
+  size_t window_len;
+  int multiplier;
+
+  bool thread_alive;
+} state_t;
+
+bool load_from_file(state_t *state, const char *filepath);
+bool write_to_file(state_t *state, const char *filepath);
+
+#endif

main.c

@@ -13,19 +13,7 @@
 #include <raylib.h>
 #include <raymath.h>
 
-struct State
-{
-  // Sandpiles
-  unsigned char *data;
-  size_t dwidth;
-
-  size_t window_len;
-  int multiplier;
-
-  bool thread_alive;
-};
-
-typedef struct State state_t;
+#include "./lib.h"
 
 void step(state_t *state)
 {