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diff --git a/src/hook.h b/src/hook.h
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+/*
+ * Copyright © 2021 Michael Smith <mikesmiffy128@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef INC_HOOK_H
+#define INC_HOOK_H
+
+#include "intdefs.h"
+
+/*
+ * Replaces a vtable entry with a target function and returns the original
+ * function.
+ */
+static inline void *hook_vtable(void **vtable, usize off, void *target) {
+	void *orig = vtable[off];
+	vtable[off] = target;
+	return orig;
+}
+
+/*
+ * Puts an original function back after hooking.
+ */
+static inline void unhook_vtable(void **vtable, usize off, void *orig) {
+	vtable[off] = orig;
+}
+
+/*
+ * Returns a trampoline pointer, or null if hooking failed. Unlike hook_vtable,
+ * handles memory protection for you.
+ */
+void *hook_inline(void *func, void *target);
+
+/*
+ * Reverts the function to its original unhooked state. Takes the pointer to the
+ * callable "original" function, i.e. the trampoline, NOT the initial function
+ * pointer from before hooking.
+ */
+void unhook_inline(void *orig);
+
+#endif
+
+// vi: sw=4 ts=4 noet tw=80 cc=80