1 files changed, 65 insertions, 0 deletions
diff --git a/src/chunklets/fastspin.h b/src/chunklets/fastspin.h
new file mode 100644
index 0000000..6c0c5f7
--- /dev/null
+++ b/src/chunklets/fastspin.h
@@ -0,0 +1,65 @@
+/*
+ * Copyright © 2023 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_CHUNKLETS_FASTSPIN_H
+#define INC_CHUNKLETS_FASTSPIN_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Raises an event through p to 0 or more callers of fastspin_wait().
+ * val must be positive, and can be used to signal a specific condition.
+ */
+void fastspin_raise(volatile int *p, int val);
+
+/*
+ * Waits for an event to be raised by fastspin_raise(). Allows this and possibly
+ * some other threads to wait for one other thread to signal its status.
+ *
+ * Returns the positive value that was passed to fastspin_raise().
+ */
+int fastspin_wait(volatile int *p);
+
+/*
+ * Takes a mutual exclusion, i.e. a lock. *p must be initialised to 0 before
+ * anything starts using it as a lock.
+ */
+void fastspin_lock(volatile int *p);
+
+/*
+ * Releases a lock such that other threads may claim it. Immediately as a lock
+ * is released, its value will be 0, as though it had just been initialised.
+ */
+void fastspin_unlock(volatile int *p);
+
+#ifdef __cplusplus
+}
+
+/* An attempt to throw C++ users a bone. Should be self-explanatory. */
+struct fastspin_lock_guard {
+	fastspin_lock_guard(volatile int &i): _p(&i) { fastspin_lock(_p); }
+	fastspin_lock_guard() = delete;
+	~fastspin_lock_guard() { fastspin_unlock(_p); }
+	volatile int *_p;
+};
+
+#endif
+
+#endif
+
+// vi: sw=4 ts=4 noet tw=80 cc=80