clock.cpp File Reference

#include <corecrt_internal_time.h>
#include <sys/timeb.h>
#include <sys/types.h>

Include dependency graph for clock.cpp:

Go to the source code of this file.

Functions
static long long	scale_count (long long count)
int __cdecl	__acrt_initialize_clock ()
	_CRT_LINKER_FORCE_INCLUDE (__acrt_clock_initializer)
clock_t __cdecl	clock ()

Variables
static long long	source_frequency
static long long	start_count

Function Documentation

__acrt_initialize_clock()

int __cdecl __acrt_initialize_clock

(

)

Definition at line 46 of file clock.cpp.

{
    LARGE_INTEGER local_frequency;
    LARGE_INTEGER local_start_count;
    if (!QueryPerformanceFrequency(&local_frequency) ||
        !QueryPerformanceCounter(&local_start_count) ||
        local_frequency.QuadPart == 0)
    {
        source_frequency = -1;
        start_count      = -1;
        return 0;
    }
 
    source_frequency = local_frequency.QuadPart;
    start_count      = local_start_count.QuadPart;
 
    return 0;
}

_CRT_LINKER_FORCE_INCLUDE()

_CRT_LINKER_FORCE_INCLUDE

(

__acrt_clock_initializer

)

clock()

clock_t __cdecl clock

(

void

)

Definition at line 74 of file clock.cpp.

{
    if (start_count == -1)
        return -1;
 
    LARGE_INTEGER current_count;
    if (!QueryPerformanceCounter(&current_count))
        return -1;
 
    long long const result = current_count.QuadPart - start_count;
    if (result < 0)
        return -1;
 
    long long const scaled_result = scale_count(result);
 
    // Per C11 7.27.2.1 ("The clock function")/3, "If the processor time used...
    // cannot be represented, the function returns the value (clock_t)(-1)."
    if (scaled_result > LONG_MAX)
        return -1;
 
    return static_cast<clock_t>(scaled_result);
}

Referenced by BaseRendererImpl_SetSyncSource(), CKsClockForwarder_Constructor(), DMUSIC_CreateReferenceClockImpl(), IDirectMusic8Impl_SetExternalMasterClock(), LIBXML_ATTR_FORMAT(), master_clock_create(), MediaStreamFilterImpl_GetSyncSource(), MediaStreamFilterImpl_SetSyncSource(), midi_IDirectMusicPort_GetLatencyClock(), QualityControlRender_SetClock(), startTimer(), SynthPortImpl_IDirectMusicPort_GetLatencyClock(), test_clock(), test_query_interface(), and test_wmreader_interfaces().

scale_count()

static long long scale_count ( long long  count )

static

Definition at line 25 of file clock.cpp.

{
    // Convert the count to seconds and multiply this by the destination frequency:
    long long scaled_count = (count / source_frequency) * CLOCKS_PER_SEC;
 
    // To reduce error introduced by scaling using integer division, separately
    // handle the remainder from the above division by multiplying the left-over
    // counter by the destination frequency, then diviting by the input frequency:
    count %= source_frequency;
 
    scaled_count += (count * CLOCKS_PER_SEC) / source_frequency;
 
    return scaled_count;
}

Referenced by clock().

Variable Documentation

source_frequency

long long source_frequency

static

Definition at line 17 of file clock.cpp.

Referenced by __acrt_initialize_clock(), and scale_count().

start_count

long long start_count

static

Definition at line 18 of file clock.cpp.

Referenced by __acrt_initialize_clock(), clock(), and TEXT_SkipChars().