1 files changed, 98 insertions, 0 deletions
diff --git a/libhw_generic/include/libhw/generic/alarmclock.h b/libhw_generic/include/libhw/generic/alarmclock.h
new file mode 100644
index 0000000..a9d816b
--- /dev/null
+++ b/libhw_generic/include/libhw/generic/alarmclock.h
@@ -0,0 +1,98 @@
+/* libhw/generic/alarmclock.h - Device-independent alarmclock definitions
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#ifndef _LIBHW_GENERIC_ALARMCLOCK_H_
+#define _LIBHW_GENERIC_ALARMCLOCK_H_
+
+#include <stdbool.h> /* for bool */
+#include <stdint.h>  /* for uint{n}_t and UINT{n}_C */
+
+#include <libmisc/private.h>
+#include <libmisc/vcall.h>
+
+/* Useful constants ***********************************************************/
+
+#define NS_PER_S UINT64_C(1000000000) /* needs at least log₂(10⁹) ≈ 29.9 bits */
+#define US_PER_S UINT64_C(1000000)    /* needs at least log₂(10⁶) ≈ 19.9 bits */
+#define MS_PER_S UINT64_C(1000)       /* needs at least log₂(10³) ≈  9.9 bits */
+
+/* Structs ********************************************************************/
+
+struct alarmclock_trigger;
+struct alarmclock_trigger {
+	BEGIN_PRIVATE(LIBHW_GENERIC_ALARMCLOCK_H)
+	void                            *alarmclock;
+	struct alarmclock_trigger       *prev, *next;
+
+	uint64_t                         fire_at_ns;
+	void                             (*cb)(void *);
+	void                            *cb_arg;
+	END_PRIVATE(LIBHW_GENERIC_ALARMCLOCK_H)
+};
+
+/* Interface ******************************************************************/
+
+struct alarmclock_vtable;
+
+typedef struct {
+	struct alarmclock_vtable     *vtable;
+} implements_alarmclock;
+
+struct alarmclock_vtable {
+	/**
+	 * (2⁶⁴-1 nanoseconds is more than 500 years; there is little
+	 * risk of this overflowing)
+	 */
+	uint64_t (*get_time_ns)(implements_alarmclock *self);
+
+	/**
+	 * Returns true on error.
+	 *
+	 * Implementations may return an error if fire_at_ns is more
+	 * than UINT32_MAX µs (72 minutes) in the future.
+	 *
+	 * If fire_at_ns is in the past, then it will fire
+	 * immediately.
+	 */
+	bool     (*add_trigger)(implements_alarmclock *self, struct alarmclock_trigger *trigger,
+	                        uint64_t   fire_at_ns,
+	                        void       (*cb)(void *),
+	                        void      *cb_arg);
+
+	void     (*del_trigger)(implements_alarmclock *self, struct alarmclock_trigger *trigger);
+};
+
+/* Utilities ******************************************************************/
+
+void alarmclock_sleep_until_ns(implements_alarmclock *clock, uint64_t abstime_ns);
+
+static inline void alarmclock_sleep_for_ns(implements_alarmclock *clock, uint64_t delta_ns) {
+	alarmclock_sleep_until_ns(clock, VCALL(clock, get_time_ns) + delta_ns);
+}
+
+static inline void alarmclock_sleep_for_us(implements_alarmclock *clock, uint64_t delta_us) {
+	alarmclock_sleep_for_ns(clock, delta_us * (NS_PER_S/US_PER_S));
+}
+
+static inline void alarmclock_sleep_for_ms(implements_alarmclock *clock, uint64_t delta_ms) {
+	alarmclock_sleep_for_ns(clock, delta_ms * (NS_PER_S/MS_PER_S));
+}
+
+static inline void alarmclock_sleep_for_s(implements_alarmclock *clock, uint64_t delta_s) {
+	alarmclock_sleep_for_ns(clock, delta_s * NS_PER_S);
+}
+
+/* Globals ********************************************************************/
+
+extern implements_alarmclock *bootclock;
+
+#define sleep_until_ns(t) alarmclock_sleep_until_ns(bootclock, t)
+#define sleep_for_ns(t)   alarmclock_sleep_for_ns(bootclock, t)
+#define sleep_for_us(t)   alarmclock_sleep_for_us(bootclock, t)
+#define sleep_for_ms(t)   alarmclock_sleep_for_ms(bootclock, t)
+#define sleep_for_s(t)    alarmclock_sleep_for_s(bootclock, t)
+
+#endif /* _LIBHW_GENERIC_ALARMCLOCK_H_ */