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/*
* 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
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