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mbed_chrono.h
1 
2 /*
3  * Copyright (c) 2015-2019, ARM Limited, All Rights Reserved
4  * SPDX-License-Identifier: Apache-2.0
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License"); you may
7  * not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
14  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18 
19 #ifndef __MBED_CHRONO_H__
20 #define __MBED_CHRONO_H__
21 
22 #include "mbed_toolchain.h"
23 #include <cstdint>
24 #include <cassert>
25 #include <ratio>
26 #include <chrono>
27 
28 /** \addtogroup platform-public-api */
29 /** @{*/
30 
31 /**
32  * \defgroup platform_chrono chrono utilities
33  *
34  * Additions and variations of std::chrono
35  *
36  * - unsigned 32-bit variants of standard signed 64-bit duration types
37  * - centiseconds and deciseconds
38  * @{
39  */
40 namespace mbed {
41 
42 /* Extensions declared in mbed::chrono, following pattern of std::chrono */
43 namespace chrono {
44 
45 /* Add deciseconds and centiseconds - may be
46  * useful to use lower precision when not messing with templating.
47  */
48 using deciseconds = std::chrono::duration<long long, std::deci>;
49 using centiseconds = std::chrono::duration<long long, std::centi>;
50 
51 /** 32-bit microsecond duration type
52  *
53  * Standard std::chrono::microseconds is signed 64-bit. For some purposes
54  * it's more efficient to process small times as 32-bit. And when doing so,
55  * as we likely need to worry about wrapping, use of an unsigned
56  * value to process modulo 2**32 is appropriate.
57  */
58 using microseconds_u32 = std::chrono::duration<std::uint32_t, std::micro>;
59 
60 /** 32-bit millisecond duration type
61  *
62  * Standard std::chrono::milliseconds is signed 64-bit. For some purposes
63  * it's more efficient to process times as 32-bit. And when doing so,
64  * as we likely need to worry about wrapping, use of an unsigned
65  * value to process modulo 2**32 is appropriate.
66  */
67 using milliseconds_u32 = std::chrono::duration<std::uint32_t, std::milli>;
68 
69 } // namespace chrono
70 
71 inline namespace literals {
72 
73 inline namespace chrono_literals {
74 
75 /** User-defined literal for deciseconds (1/10 of a second)
76  *
77  * Useful in case we might change kernel tick frequency to be slower - with tick frequency 1000Hz, it is
78  * possible to assign 500ms to a KernelClock::duration, but that would fail at slower rates.
79  *
80  * Example use:
81  *
82  * using namespace mbed::chrono_literals;
83  *
84  * ThisThread::sleep_for(5_ds);
85  */
86 constexpr chrono::deciseconds operator "" _ds(unsigned long long x)
87 {
88  chrono::deciseconds::rep val = static_cast<chrono::deciseconds::rep>(x);
89  assert(val >= 0 && static_cast<unsigned long long>(val) == x);
90  return chrono::deciseconds(val);
91 }
92 
93 /** User-defined literal for centiseconds (1/100 of a second)
94  *
95  * Useful in case we might change kernel tick frequency to be slower - with tick frequency 1000Hz, it is
96  * possible to assign 500ms to a KernelClock::duration, but that would fail at slower rates.
97  *
98  * Example use:
99  *
100  * using namespace mbed::chrono_literals;
101  *
102  * ThisThread::sleep_for(1_cs);
103  */
104 constexpr chrono::centiseconds operator "" _cs(unsigned long long x)
105 {
106  chrono::centiseconds::rep val = static_cast<chrono::centiseconds::rep>(x);
107  assert(val >= 0 && static_cast<unsigned long long>(val) == x);
108  return chrono::centiseconds(val);
109 }
110 
111 } // inline namespace chrono_literals
112 
113 } // inline namespace literals
114 
115 namespace chrono {
116 
117 using namespace chrono_literals;
118 
119 } // namespace chrono
120 
121 } // namespace mbed
122 
123 /**@}*/
124 
125 /**@}*/
126 
127 #endif // __MBED_CHRONO_H__
128 
chrono_literals
mbed
Definition: ATHandler.h:46
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