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124 lines
3.4 KiB
Markdown
124 lines
3.4 KiB
Markdown
---
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title: "Clocks"
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---
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## Macros
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Default macro definitions.
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Define these in `etl_profile.h` to set your own duration types for the clocks.
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| Macro | Definition |
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| -------------------------------------------- | -------------------------- |
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| `ETL_CHRONO_SYSTEM_CLOCK_DURATION` | `etl::chrono::nanoseconds` |
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| `ETL_CHRONO_SYSTEM_CLOCK_IS_STEADY` | `true` |
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| `ETL_CHRONO_HIGH_RESOLUTION_CLOCK_DURATION` | `etl::chrono::nanoseconds` |
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| `ETL_CHRONO_HIGH_RESOLUTION_CLOCK_IS_STEADY` | `true` |
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| `ETL_CHRONO_STEADY_CLOCK_DURATION` | `etl::chrono::nanoseconds` |
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## Platform clock access
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Declarations of the functions that must be defined to interface the clocks with the underlying platform.
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```cpp
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extern "C" ETL_CHRONO_SYSTEM_CLOCK_DURATION::rep etl_get_system_clock();
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extern "C" ETL_CHRONO_HIGH_RESOLUTION_CLOCK_DURATION::rep etl_get_high_resolution_clock();
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extern "C" ETL_CHRONO_STEADY_CLOCK_DURATION::rep etl_get_steady_clock();
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```
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These functions must return the current count of the underlying clock. The value is in terms of the
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clock duration defined for that clock.
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**Example**
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If the `system_clock` duration is set to `etl::chrono::nanoseconds`, then a return value of `1000` represents `1000ns`.
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## system_clock
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```cpp
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class system_clock
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```
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### Member types
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```cpp
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using duration = ETL_CHRONO_SYSTEM_CLOCK_DURATION
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using rep = duration::rep
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using period = duration::period
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using time_point = time_point<system_clock, duration>
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```
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### Member functions
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```cpp
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static time_point now() ETL_NOEXCEPT
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static time_t to_time_t(const time_point& t) ETL_NOEXCEPT
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static time_point from_time_t(time_t t) ETL_NOEXCEPT
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```
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## high_resolution_clock
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```cpp
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class high_resolution_clock
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```
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### Member types
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```cpp
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using duration = ETL_CHRONO_HIGH_RESOLUTION_CLOCK_DURATION
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using rep = duration::rep
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using period = duration::period
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using time_point = time_point<high_resolution_clock, duration>
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```
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### Member functions
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```cpp
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static time_point now() ETL_NOEXCEPT
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```
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## steady_clock
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```cpp
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class steady_clock
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```
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### Member types
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```cpp
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using duration = ETL_CHRONO_STEADY_CLOCK_DURATION
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using rep = duration::rep
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using period = duration::period
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using time_point = time_point<steady_clock, duration>
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```
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### Member functions
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```cpp
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static time_point now() ETL_NOEXCEPT
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```
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## system_time
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```cpp
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template <typename Duration>
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using sys_time = etl::chrono::time_point<etl::chrono::system_clock, Duration>
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using sys_seconds = sys_time<etl::chrono::seconds>
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using sys_days = sys_time<etl::chrono::days>
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```
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## local_time
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```cpp
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struct local_t
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```
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```cpp
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template <typename TDuration>
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using local_time = etl::chrono::time_point<etl::chrono::local_t, TDuration>
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using local_seconds = local_time<etl::chrono::seconds>
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using local_days = local_time<etl::chrono::days>
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```
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## clock_cast
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Cast a time point from one clock to another.
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This implementation assumes all clock epochs are the same.
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```cpp
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template <typename TToClock,
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typename TFromClock,
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typename TFromDuration>
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ETL_CONSTEXPR14 etl::chrono::time_point<TToClock,
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typename TToClock::duration>
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clock_cast(const etl::chrono::time_point<TFromClock, TFromDuration>& from_time_point) ETL_NOEXCEPT
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```
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