Atomic, high-resolution elapsed-time timer. More...

#include <elapsed_timer.h>

Collaboration diagram for vlink::ElapsedTimer:

Public Types
enum	Method : uint8_t { kCpuTimestamp = 0 , kCpuActiveTime = 1 }
	Selects the underlying clock source for time measurement. More...
enum	Accuracy : uint8_t { kMilli = 0 , kMicro = 1 , kNano = 2 }
	Selects the precision (resolution) of the timer values returned. More...

Public Member Functions
	ElapsedTimer () noexcept
	Constructs an `ElapsedTimer` with default method (`kCpuTimestamp`) and default accuracy (`kMilli`).
	ElapsedTimer (Method method) noexcept
	Constructs an `ElapsedTimer` with the specified clock source.
	ElapsedTimer (Accuracy accuracy) noexcept
	Constructs an `ElapsedTimer` with the specified precision.
	ElapsedTimer (Method method, Accuracy accuracy) noexcept
	Constructs an `ElapsedTimer` with the specified clock source and precision.
	ElapsedTimer (const ElapsedTimer &target) noexcept
	Copy constructor. Copies the current start-time snapshot, method, and accuracy.
	ElapsedTimer (ElapsedTimer &&target) noexcept
	Move constructor. Behaves identically to the copy constructor.
	~ElapsedTimer () noexcept
	Destructor.
ElapsedTimer &	operator= (const ElapsedTimer &target) noexcept
	Copy-assignment operator.
ElapsedTimer &	operator= (ElapsedTimer &&) noexcept
	Move-assignment operator.
Method	get_method () const noexcept
	Returns the clock source configured for this timer.
Accuracy	get_accuracy () const noexcept
	Returns the precision configured for this timer.
void	start () noexcept
	Starts the timer if it is not already active.
void	stop () noexcept
	Stops the timer, setting the internal start time to `-1`.
int64_t	restart () noexcept
	Atomically resets the start time to now and returns the elapsed time since the previous `start()` / `restart()` call.
bool	is_active () const noexcept
	Returns `true` when the timer has been started and not yet stopped.
int64_t	get () const noexcept
	Returns the elapsed time since `start()` was called.

Static Public Member Functions
static uint64_t	get_sys_timestamp (Accuracy accuracy=kMilli, bool high_resolution=true) noexcept
	Returns the current wall-clock (system) timestamp.
static uint64_t	get_cpu_timestamp (Accuracy accuracy=kMilli, bool high_resolution=true) noexcept
	Returns the current monotonic CPU timestamp.
static uint64_t	get_cpu_active_time (Accuracy accuracy=kMilli) noexcept
	Returns the accumulated CPU time (user + kernel) consumed by the current process.

Detailed Description

Atomic, high-resolution elapsed-time timer.

Measures elapsed time since start() using either a monotonic wall-clock (kCpuTimestamp) or the process CPU-active time (kCpuActiveTime). The class is final and not copyable (copy/move constructors are provided but only copy the snapshot value, not ownership semantics).

Member Enumeration Documentation

◆ Accuracy

enum vlink::ElapsedTimer::Accuracy : uint8_t

Selects the precision (resolution) of the timer values returned.

Enumerator
kMilli	Millisecond precision.
kMicro	Microsecond precision.
kNano	Nanosecond precision.

◆ Method

enum vlink::ElapsedTimer::Method : uint8_t

Selects the underlying clock source for time measurement.

Enumerator
kCpuTimestamp	Monotonic wall-clock (CLOCK_MONOTONIC_RAW on Linux).
kCpuActiveTime	Process CPU time (user + kernel, via getrusage).

Constructor & Destructor Documentation

◆ ElapsedTimer() [1/6]

vlink::ElapsedTimer::ElapsedTimer ( )

noexcept

Constructs an ElapsedTimer with default method (kCpuTimestamp) and default accuracy (kMilli).

The timer is not started after construction.

Here is the caller graph for this function:

◆ ElapsedTimer() [2/6]

vlink::ElapsedTimer::ElapsedTimer ( Method method )

explicitnoexcept

Constructs an ElapsedTimer with the specified clock source.

Parameters

method The clock source to use (kCpuTimestamp or kCpuActiveTime).

Here is the call graph for this function:

◆ ElapsedTimer() [3/6]

vlink::ElapsedTimer::ElapsedTimer ( Accuracy accuracy )

explicitnoexcept

Constructs an ElapsedTimer with the specified precision.

Parameters

accuracy The precision of time values (kMilli, kMicro, or kNano).

Here is the call graph for this function:

◆ ElapsedTimer() [4/6]

vlink::ElapsedTimer::ElapsedTimer	(	Method	method,
		Accuracy	accuracy )

explicitnoexcept

Constructs an ElapsedTimer with the specified clock source and precision.

Parameters

method	The clock source to use.
accuracy	The precision of time values.

Here is the call graph for this function:

◆ ElapsedTimer() [5/6]

vlink::ElapsedTimer::ElapsedTimer ( const ElapsedTimer & target )

noexcept

Copy constructor. Copies the current start-time snapshot, method, and accuracy.

Parameters

target The source timer.

Here is the call graph for this function:

◆ ElapsedTimer() [6/6]

vlink::ElapsedTimer::ElapsedTimer ( ElapsedTimer && target )

noexcept

Move constructor. Behaves identically to the copy constructor.

Parameters

target The source timer.

Here is the call graph for this function:

◆ ~ElapsedTimer()

vlink::ElapsedTimer::~ElapsedTimer ( )

noexcept

Destructor.

Here is the call graph for this function:

Member Function Documentation

◆ get()

int64_t vlink::ElapsedTimer::get ( ) const

nodiscardnoexcept

Returns the elapsed time since start() was called.

The value is computed as (current_time - start_time_) in the configured precision units. Returns -1 if the timer has not been started (or has been stopped).

Returns

Elapsed time in the configured units (>= 0) when active.
-1 when the timer is not active.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ get_accuracy()

Accuracy vlink::ElapsedTimer::get_accuracy ( ) const

nodiscardnoexcept

Returns the precision configured for this timer.

Returns: The Accuracy value set at construction.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ get_cpu_active_time()

uint64_t vlink::ElapsedTimer::get_cpu_active_time ( Accuracy accuracy = kMilli )

staticnodiscardnoexcept

Returns the accumulated CPU time (user + kernel) consumed by the current process.

Uses getrusage(RUSAGE_SELF) on POSIX or GetProcessTimes on Windows. The returned value is the total CPU time used so far in the process lifetime, not a delta. Use ElapsedTimer with kCpuActiveTime to measure deltas.

Parameters

accuracy Desired precision (default: kMilli).

Returns: Cumulative process CPU time in the requested unit.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ get_cpu_timestamp()

uint64_t vlink::ElapsedTimer::get_cpu_timestamp	(	Accuracy	accuracy = kMilli,
		bool	high_resolution = true )

staticnodiscardnoexcept

Returns the current monotonic CPU timestamp.

On Linux uses CLOCK_MONOTONIC_RAW (unaffected by NTP) when high_resolution is true; otherwise uses std::chrono::steady_clock. On Windows always uses std::chrono::steady_clock.

Parameters

accuracy	Desired precision (default: `kMilli`).
high_resolution	Whether to use `clock_gettime` (Linux only, default: `true`).

Returns: Current monotonic timestamp in the requested unit.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ get_method()

Method vlink::ElapsedTimer::get_method ( ) const

nodiscardnoexcept

Returns the clock source configured for this timer.

Returns: The Method value set at construction.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ get_sys_timestamp()

uint64_t vlink::ElapsedTimer::get_sys_timestamp	(	Accuracy	accuracy = kMilli,
		bool	high_resolution = true )

staticnodiscardnoexcept

Returns the current wall-clock (system) timestamp.

On Linux uses CLOCK_REALTIME via clock_gettime for maximum precision when high_resolution is true; otherwise uses std::chrono::system_clock. On Windows always uses std::chrono::system_clock.

Parameters

accuracy	Desired precision (default: `kMilli`).
high_resolution	Whether to use `clock_gettime` (Linux only, default: `true`).

Returns: Current system timestamp in the requested unit.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ is_active()

bool vlink::ElapsedTimer::is_active ( ) const

nodiscardnoexcept

Returns true when the timer has been started and not yet stopped.

Returns: true if active (start_time_ >= 0), false otherwise.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ operator=() [1/2]

ElapsedTimer & vlink::ElapsedTimer::operator= ( const ElapsedTimer & target )

noexcept

Copy-assignment operator.

Parameters

target The source timer.

Returns: A reference to *this.

Here is the call graph for this function:

◆ operator=() [2/2]

ElapsedTimer & vlink::ElapsedTimer::operator= ( ElapsedTimer && )

noexcept

Move-assignment operator.

Parameters

target The source timer (moved from).

Returns: A reference to *this.

Here is the call graph for this function:

◆ restart()

int64_t vlink::ElapsedTimer::restart ( )

noexcept

Atomically resets the start time to now and returns the elapsed time since the previous start() / restart() call.

This is equivalent to get() followed by start(), but performed atomically using exchange. If the timer was not active, returns a negative value (the raw start_time_ value, which is -1 when stopped).

Returns

Elapsed time in the configured units since the last start/restart, or
A negative value if the timer was not started before this call.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ start()

void vlink::ElapsedTimer::start ( )

noexcept

Starts the timer if it is not already active.

Records the current time as the start reference using a CAS on the internal atomic. If the timer is already active this call is a no-op. Call stop() first to reset and then start() again.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ stop()

void vlink::ElapsedTimer::stop ( )

noexcept

Stops the timer, setting the internal start time to -1.

After stop(), is_active() returns false and get() returns -1.

Here is the call graph for this function:

Here is the caller graph for this function:

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

include/vlink/base/elapsed_timer.h

Public Types

Public Member Functions

Static Public Member Functions

Detailed Description

Member Enumeration Documentation

◆ Accuracy

◆ Method

Constructor & Destructor Documentation

◆ ElapsedTimer() [1/6]

◆ ElapsedTimer() [2/6]

◆ ElapsedTimer() [3/6]

◆ ElapsedTimer() [4/6]

◆ ElapsedTimer() [5/6]

◆ ElapsedTimer() [6/6]

◆ ~ElapsedTimer()

Member Function Documentation

◆ get()

◆ get_accuracy()

◆ get_cpu_active_time()

◆ get_cpu_timestamp()

◆ get_method()

◆ get_sys_timestamp()

◆ is_active()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ restart()

◆ start()

◆ stop()