v1::time_stamp_count Class Reference

#include <hikogui/time/time_stamp_count.hpp>

Data Structures
struct	inplace
struct	inplace_with_cpu_id
struct	inplace_with_thread_id

Public Member Functions
constexpr	time_stamp_count (uint64_t count, uint32_t aux) noexcept
	time_stamp_count (time_stamp_count::inplace) noexcept
	Use a constructor to in-place create the timestamp.
	time_stamp_count (time_stamp_count::inplace_with_cpu_id) noexcept
	Use a constructor to in-place create the timestamp.
	time_stamp_count (time_stamp_count::inplace_with_thread_id) noexcept
	Use a constructor to in-place create the timestamp.
ssize_t	cpu_id () const noexcept
	Get the logical CPU index.
constexpr uint32_t	thread_id () const noexcept
	Get the thread id.
constexpr uint64_t	count () const noexcept
	Get the count since epoch.
std::chrono::nanoseconds	time_since_epoch () const noexcept
	Convert to nanoseconds since epoch.
constexpr time_stamp_count &	operator+= (uint64_t rhs) noexcept
constexpr time_stamp_count	operator+ (uint64_t rhs) const noexcept

Static Public Member Functions
static time_stamp_count	now () noexcept
	Get the current count from the CPU's time stamp count.
static std::chrono::nanoseconds	duration_from_count (uint64_t count) noexcept
	Convert a time-stamp count to a duration.
static std::pair< utc_nanoseconds, time_stamp_count >	time_stamp_utc_sample ()
	Get a good quality time sample.
static uint64_t	measure_frequency (std::chrono::milliseconds sample_duration)
	Measure the frequency of the time_stamp_count.
static void	set_frequency (uint64_t frequency) noexcept
static std::pair< uint64_t, bool >	start_subsystem ()
	Start the time_stamp_count subsystem.

Detailed Description

Since Window's 10 QueryPerformanceCounter() counts at only 10MHz which is too low to measure performance in many cases.

Instead we will use the TSC.

Constructor & Destructor Documentation

time_stamp_count() [1/3]

v1::time_stamp_count::time_stamp_count ( time_stamp_count::inplace )

inlineexplicitnoexcept

Use a constructor to in-place create the timestamp.

time_stamp_count() [2/3]

v1::time_stamp_count::time_stamp_count ( time_stamp_count::inplace_with_cpu_id )

inlineexplicitnoexcept

Use a constructor to in-place create the timestamp.

time_stamp_count() [3/3]

v1::time_stamp_count::time_stamp_count ( time_stamp_count::inplace_with_thread_id )

inlineexplicitnoexcept

Use a constructor to in-place create the timestamp.

Member Function Documentation

count()

constexpr uint64_t v1::time_stamp_count::count ( ) const

inlineconstexprnoexcept

Get the count since epoch.

The epoch is the same as the TSC count's epoch. In most cases the epoch is at system startup time.

cpu_id()

ssize_t v1::time_stamp_count::cpu_id ( ) const

inlinenoexcept

Get the logical CPU index.

This is logical CPU id that the operating system uses for things like thread affinity.

Returns

the processor index, or -1 if the processor index is unknown.

duration_from_count()

static std::chrono::nanoseconds v1::time_stamp_count::duration_from_count ( uint64_t count )

inlinestaticnoexcept

Convert a time-stamp count to a duration.

Parameters

count

The number clock ticks.

Returns

A period of nanoseconds representing the count of clock ticks.

measure_frequency()

static uint64_t v1::time_stamp_count::measure_frequency ( std::chrono::milliseconds sample_duration )

inlinestatic

Measure the frequency of the time_stamp_count.

Frequency drift from TSC is 1ppm

Parameters

sample_duration

The time between samples to determine the frequency longer duration gives a better quality but may increase application start-up time.

Returns

The clock frequency of the TSC in Hz.

now()

static time_stamp_count v1::time_stamp_count::now ( )

inlinestaticnoexcept

Get the current count from the CPU's time stamp count.

Returns

The current clock count and CPU-id.

start_subsystem()

static std::pair< uint64_t, bool > v1::time_stamp_count::start_subsystem ( )

inlinestatic

Start the time_stamp_count subsystem.

Returns

The time-stamp-counter frequency

Exceptions

os_error

When the time-stamp-counter does not work. AUX is the same as the cpu-id.

thread_id()

constexpr uint32_t v1::time_stamp_count::thread_id ( ) const

inlineconstexprnoexcept

Get the thread id.

Precondition

Must call time_stamp_count(time_stamp_count::inplace_with_thread_id) first.

time_since_epoch()

std::chrono::nanoseconds v1::time_stamp_count::time_since_epoch ( ) const

inlinenoexcept

Convert to nanoseconds since epoch.

The epoch is the same as the TSC count's epoch. In most cases the epoch is at system startup time.

time_stamp_utc_sample()

static std::pair< utc_nanoseconds, time_stamp_count > v1::time_stamp_count::time_stamp_utc_sample ( )

inlinestatic

Get a good quality time sample.

Precondition

The CPU affinity must be set to a single CPU.

Returns

The current UTC time in nanoseconds, the current time-stamp count.

Exceptions

os_error

When there is a problem getting a time-sample.

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The documentation for this class was generated from the following file:

• hikogui/src/hikogui/time/time_stamp_count.hpp