board: Factor out Chunithm slider

board/slider-frame.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <windows.h>
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "hook/iobuf.h"
+
+enum {
+    SLIDER_FRAME_SYNC = 0xFF,
+};
+
+struct slider_hdr {
+    uint8_t sync;
+    uint8_t cmd;
+    uint8_t nbytes;
+};
+
+HRESULT slider_frame_decode(struct iobuf *dest, struct iobuf *src);
+
+HRESULT slider_frame_encode(
+        struct iobuf *dest,
+        const void *ptr,
+        size_t nbytes);