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1 /******************************************************************************
2  *
3  *  Copyright (C) 2014 Google, Inc.
4  *
5  *  Licensed under the Apache License, Version 2.0 (the "License");
6  *  you may not use this file except in compliance with the License.
7  *  You may obtain a copy of the License at:
8  *
9  *  http://www.apache.org/licenses/LICENSE-2.0
10  *
11  *  Unless required by applicable law or agreed to in writing, software
12  *  distributed under the License is distributed on an "AS IS" BASIS,
13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  *  See the License for the specific language governing permissions and
15  *  limitations under the License.
16  *
17  ******************************************************************************/
18 
19 #pragma once
20 
21 #include <stdint.h>
22 
23 typedef struct alarm_t alarm_t;
24 typedef uint64_t period_ms_t;
25 
26 // Prototype for the callback function.
27 typedef void (*alarm_callback_t)(void *data);
28 
29 // Creates a new alarm object. The returned object must be freed by calling
30 // |alarm_free|. Returns NULL on failure.
31 alarm_t *alarm_new(void);
32 
33 // Frees an alarm object created by |alarm_new|. |alarm| may be NULL. If the
34 // alarm is pending, it will be cancelled. It is not safe to call |alarm_free|
35 // from inside the callback of |alarm|.
36 void alarm_free(alarm_t *alarm);
37 
38 // Sets an alarm to fire |cb| after the given |deadline|. Note that |deadline| is the
39 // number of milliseconds relative to the current time. |data| is a context variable
40 // for the callback and may be NULL. |cb| will be called back in the context of an
41 // unspecified thread (i.e. it will not be called back in the same thread as the caller).
42 // |alarm| and |cb| may not be NULL.
43 void alarm_set(alarm_t *alarm, period_ms_t deadline, alarm_callback_t cb, void *data);
44 
45 // Like alarm_set, except the alarm repeats every |period| ms until it is cancelled or
46 // freed or |alarm_set| is called to set it non-periodically.
47 void alarm_set_periodic(alarm_t *alarm, period_ms_t period, alarm_callback_t cb, void *data);
48 
49 // This function cancels the |alarm| if it was previously set. When this call
50 // returns, the caller has a guarantee that the callback is not in progress and
51 // will not be called if it hasn't already been called. This function is idempotent.
52 // |alarm| may not be NULL.
53 void alarm_cancel(alarm_t *alarm);
54 
55 // Figure out how much time until next expiration.
56 // Returns 0 if not armed. |alarm| may not be NULL.
57 // TODO: Remove this function once PM timers can be re-factored
58 period_ms_t alarm_get_remaining_ms(const alarm_t *alarm);
59 
60 // Alarm-related state cleanup
61 void alarm_cleanup(void);
62