cpython/Python/pytime.c at pythoncapi · pythoncapi/cpython · GitHub

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#include "Python.h"

#ifdef MS_WINDOWS

#include <windows.h>

#endif

#if defined(__APPLE__)

#include <mach/mach_time.h> /* mach_absolute_time(), mach_timebase_info() */

#endif

#define _PyTime_check_mul_overflow(a, b) \

(assert(b > 0), \

(_PyTime_t)(a) < _PyTime_MIN / (_PyTime_t)(b) \

|| _PyTime_MAX / (_PyTime_t)(b) < (_PyTime_t)(a))

/* To millisecond (10^-3) */

#define SEC_TO_MS 1000

/* To microseconds (10^-6) */

#define MS_TO_US 1000

#define SEC_TO_US (SEC_TO_MS * MS_TO_US)

/* To nanoseconds (10^-9) */

#define US_TO_NS 1000

#define MS_TO_NS (MS_TO_US * US_TO_NS)

#define SEC_TO_NS (SEC_TO_MS * MS_TO_NS)

/* Conversion from nanoseconds */

#define NS_TO_MS (1000 * 1000)

#define NS_TO_US (1000)

static void

error_time_t_overflow(void)

{

PyErr_SetString(PyExc_OverflowError,

"timestamp out of range for platform time_t");

}

static void

_PyTime_overflow(void)

{

PyErr_SetString(PyExc_OverflowError,

"timestamp too large to convert to C _PyTime_t");

}

_PyTime_t

_PyTime_MulDiv(_PyTime_t ticks, _PyTime_t mul, _PyTime_t div)

{

_PyTime_t intpart, remaining;

/* Compute (ticks * mul / div) in two parts to prevent integer overflow:

compute integer part, and then the remaining part.

(ticks * mul) / div == (ticks / div) * mul + (ticks % div) * mul / div

The caller must ensure that "(div - 1) * mul" cannot overflow. */

intpart = ticks / div;

ticks %= div;

remaining = ticks * mul;

remaining /= div;

return intpart * mul + remaining;

}

time_t

_PyLong_AsTime_t(PyObject *obj)

{

#if SIZEOF_TIME_T == SIZEOF_LONG_LONG

long long val;

val = PyLong_AsLongLong(obj);

#else

long val;

Py_BUILD_ASSERT(sizeof(time_t) <= sizeof(long));

val = PyLong_AsLong(obj);

#endif

if (val == -1 && PyErr_Occurred()) {

if (PyErr_ExceptionMatches(PyExc_OverflowError)) {

error_time_t_overflow();

}

return -1;

}

return (time_t)val;

}

PyObject *

_PyLong_FromTime_t(time_t t)

{

#if SIZEOF_TIME_T == SIZEOF_LONG_LONG

return PyLong_FromLongLong((long long)t);

#else

Py_BUILD_ASSERT(sizeof(time_t) <= sizeof(long));

return PyLong_FromLong((long)t);

#endif

}

/* Round to nearest with ties going to nearest even integer

(_PyTime_ROUND_HALF_EVEN) */

static double

_PyTime_RoundHalfEven(double x)

{

double rounded = round(x);

if (fabs(x-rounded) == 0.5) {

/* halfway case: round to even */

rounded = 2.0*round(x/2.0);

}

return rounded;

}

static double

_PyTime_Round(double x, _PyTime_round_t round)

{

/* volatile avoids optimization changing how numbers are rounded */

volatile double d;

d = x;

if (round == _PyTime_ROUND_HALF_EVEN) {

d = _PyTime_RoundHalfEven(d);

}

else if (round == _PyTime_ROUND_CEILING) {

d = ceil(d);

}

else if (round == _PyTime_ROUND_FLOOR) {

d = floor(d);

}

else {

assert(round == _PyTime_ROUND_UP);

d = (d >= 0.0) ? ceil(d) : floor(d);

}

return d;

}

static int

_PyTime_DoubleToDenominator(double d, time_t *sec, long *numerator,

long idenominator, _PyTime_round_t round)

{

double denominator = (double)idenominator;

double intpart;

/* volatile avoids optimization changing how numbers are rounded */

volatile double floatpart;

floatpart = modf(d, &intpart);

floatpart *= denominator;

floatpart = _PyTime_Round(floatpart, round);

if (floatpart >= denominator) {

floatpart -= denominator;

intpart += 1.0;

}

else if (floatpart < 0) {

floatpart += denominator;

intpart -= 1.0;

}

assert(0.0 <= floatpart && floatpart < denominator);

if (!_Py_InIntegralTypeRange(time_t, intpart)) {

error_time_t_overflow();

return -1;

}

*sec = (time_t)intpart;

*numerator = (long)floatpart;

assert(0 <= *numerator && *numerator < idenominator);

return 0;

}

static int

_PyTime_ObjectToDenominator(PyObject *obj, time_t *sec, long *numerator,

long denominator, _PyTime_round_t round)

{

assert(denominator >= 1);

if (PyFloat_Check(obj)) {

double d = PyFloat_AsDouble(obj);

if (Py_IS_NAN(d)) {

*numerator = 0;

PyErr_SetString(PyExc_ValueError, "Invalid value NaN (not a number)");

return -1;

}

return _PyTime_DoubleToDenominator(d, sec, numerator,

denominator, round);

}

else {

*sec = _PyLong_AsTime_t(obj);

*numerator = 0;

if (*sec == (time_t)-1 && PyErr_Occurred()) {

return -1;

}

return 0;

}

int

_PyTime_ObjectToTime_t(PyObject *obj, time_t *sec, _PyTime_round_t round)

{

if (PyFloat_Check(obj)) {

double intpart;

/* volatile avoids optimization changing how numbers are rounded */

volatile double d;

d = PyFloat_AsDouble(obj);

if (Py_IS_NAN(d)) {

PyErr_SetString(PyExc_ValueError, "Invalid value NaN (not a number)");

return -1;

}

d = _PyTime_Round(d, round);

(void)modf(d, &intpart);

if (!_Py_InIntegralTypeRange(time_t, intpart)) {

error_time_t_overflow();

return -1;

}

*sec = (time_t)intpart;

return 0;

}

else {

*sec = _PyLong_AsTime_t(obj);

if (*sec == (time_t)-1 && PyErr_Occurred()) {

return -1;

}

return 0;

}

int

_PyTime_ObjectToTimespec(PyObject *obj, time_t *sec, long *nsec,

_PyTime_round_t round)

{

return _PyTime_ObjectToDenominator(obj, sec, nsec, SEC_TO_NS, round);

}

int

_PyTime_ObjectToTimeval(PyObject *obj, time_t *sec, long *usec,

_PyTime_round_t round)

{

return _PyTime_ObjectToDenominator(obj, sec, usec, SEC_TO_US, round);

}

_PyTime_t

_PyTime_FromSeconds(int seconds)

{

_PyTime_t t;

/* ensure that integer overflow cannot happen, int type should have 32

bits, whereas _PyTime_t type has at least 64 bits (SEC_TO_MS takes 30

bits). */

Py_BUILD_ASSERT(INT_MAX <= _PyTime_MAX / SEC_TO_NS);

Py_BUILD_ASSERT(INT_MIN >= _PyTime_MIN / SEC_TO_NS);

t = (_PyTime_t)seconds;

assert((t >= 0 && t <= _PyTime_MAX / SEC_TO_NS)

|| (t < 0 && t >= _PyTime_MIN / SEC_TO_NS));

t *= SEC_TO_NS;

return t;

}

_PyTime_t

_PyTime_FromNanoseconds(_PyTime_t ns)

{

/* _PyTime_t already uses nanosecond resolution, no conversion needed */

return ns;

}

int

_PyTime_FromNanosecondsObject(_PyTime_t *tp, PyObject *obj)

{

long long nsec;

_PyTime_t t;

if (!PyLong_Check(obj)) {

PyErr_Format(PyExc_TypeError, "expect int, got %s",

Py_TYPE(obj)->tp_name);

return -1;

}

Py_BUILD_ASSERT(sizeof(long long) == sizeof(_PyTime_t));

nsec = PyLong_AsLongLong(obj);

if (nsec == -1 && PyErr_Occurred()) {

if (PyErr_ExceptionMatches(PyExc_OverflowError)) {

_PyTime_overflow();

}

return -1;

}

/* _PyTime_t already uses nanosecond resolution, no conversion needed */

t = (_PyTime_t)nsec;

*tp = t;

return 0;

}

#ifdef HAVE_CLOCK_GETTIME

static int

pytime_fromtimespec(_PyTime_t *tp, struct timespec *ts, int raise)

{

_PyTime_t t, nsec;

int res = 0;

Py_BUILD_ASSERT(sizeof(ts->tv_sec) <= sizeof(_PyTime_t));

t = (_PyTime_t)ts->tv_sec;

if (_PyTime_check_mul_overflow(t, SEC_TO_NS)) {

if (raise) {

_PyTime_overflow();

}

res = -1;

t = (t > 0) ? _PyTime_MAX : _PyTime_MIN;

}

else {

t = t * SEC_TO_NS;

}

nsec = ts->tv_nsec;

/* The following test is written for positive only nsec */

assert(nsec >= 0);

if (t > _PyTime_MAX - nsec) {

if (raise) {

_PyTime_overflow();

}

res = -1;

t = _PyTime_MAX;

}

else {

t += nsec;

}

*tp = t;

return res;

}

int

_PyTime_FromTimespec(_PyTime_t *tp, struct timespec *ts)

{

return pytime_fromtimespec(tp, ts, 1);

}

#endif

#if !defined(MS_WINDOWS)

static int

pytime_fromtimeval(_PyTime_t *tp, struct timeval *tv, int raise)

{

_PyTime_t t, usec;

int res = 0;

Py_BUILD_ASSERT(sizeof(tv->tv_sec) <= sizeof(_PyTime_t));

t = (_PyTime_t)tv->tv_sec;

if (_PyTime_check_mul_overflow(t, SEC_TO_NS)) {

if (raise) {

_PyTime_overflow();

}

res = -1;

t = (t > 0) ? _PyTime_MAX : _PyTime_MIN;

}

else {

t = t * SEC_TO_NS;

}

usec = (_PyTime_t)tv->tv_usec * US_TO_NS;

/* The following test is written for positive only usec */

assert(usec >= 0);

if (t > _PyTime_MAX - usec) {

if (raise) {

_PyTime_overflow();

}

res = -1;

t = _PyTime_MAX;

}

else {

t += usec;

}

*tp = t;

return res;

}

int

_PyTime_FromTimeval(_PyTime_t *tp, struct timeval *tv)

{

return pytime_fromtimeval(tp, tv, 1);

}

#endif

static int

_PyTime_FromDouble(_PyTime_t *t, double value, _PyTime_round_t round,

long unit_to_ns)

{

/* volatile avoids optimization changing how numbers are rounded */

volatile double d;

/* convert to a number of nanoseconds */

d = value;

d *= (double)unit_to_ns;

d = _PyTime_Round(d, round);

if (!_Py_InIntegralTypeRange(_PyTime_t, d)) {

_PyTime_overflow();

return -1;

}

*t = (_PyTime_t)d;

return 0;

}

static int

_PyTime_FromObject(_PyTime_t *t, PyObject *obj, _PyTime_round_t round,

long unit_to_ns)

{

if (PyFloat_Check(obj)) {

double d;

d = PyFloat_AsDouble(obj);

if (Py_IS_NAN(d)) {

PyErr_SetString(PyExc_ValueError, "Invalid value NaN (not a number)");

return -1;

}

return _PyTime_FromDouble(t, d, round, unit_to_ns);

}

else {

long long sec;

Py_BUILD_ASSERT(sizeof(long long) <= sizeof(_PyTime_t));

sec = PyLong_AsLongLong(obj);

if (sec == -1 && PyErr_Occurred()) {

if (PyErr_ExceptionMatches(PyExc_OverflowError)) {

_PyTime_overflow();

}

return -1;

}

if (_PyTime_check_mul_overflow(sec, unit_to_ns)) {

_PyTime_overflow();

return -1;

}

*t = sec * unit_to_ns;

return 0;

}

int

_PyTime_FromSecondsObject(_PyTime_t *t, PyObject *obj, _PyTime_round_t round)

{

return _PyTime_FromObject(t, obj, round, SEC_TO_NS);

}

int

_PyTime_FromMillisecondsObject(_PyTime_t *t, PyObject *obj, _PyTime_round_t round)

{

return _PyTime_FromObject(t, obj, round, MS_TO_NS);

}

double

_PyTime_AsSecondsDouble(_PyTime_t t)

{

/* volatile avoids optimization changing how numbers are rounded */

volatile double d;

if (t % SEC_TO_NS == 0) {

_PyTime_t secs;

/* Divide using integers to avoid rounding issues on the integer part.

1e-9 cannot be stored exactly in IEEE 64-bit. */

secs = t / SEC_TO_NS;

d = (double)secs;

}

else {

d = (double)t;

d /= 1e9;

}

return d;

}

PyObject *

_PyTime_AsNanosecondsObject(_PyTime_t t)

{

Py_BUILD_ASSERT(sizeof(long long) >= sizeof(_PyTime_t));

return PyLong_FromLongLong((long long)t);

}

static _PyTime_t

_PyTime_Divide(const _PyTime_t t, const _PyTime_t k,

const _PyTime_round_t round)

{

assert(k > 1);

if (round == _PyTime_ROUND_HALF_EVEN) {

_PyTime_t x, r, abs_r;

x = t / k;

r = t % k;

abs_r = Py_ABS(r);

if (abs_r > k / 2 || (abs_r == k / 2 && (Py_ABS(x) & 1))) {

if (t >= 0) {

x++;

}

else {

x--;

}

return x;

}

else if (round == _PyTime_ROUND_CEILING) {

if (t >= 0) {

return (t + k - 1) / k;

}

else {

return t / k;

}

else if (round == _PyTime_ROUND_FLOOR){

if (t >= 0) {

return t / k;

}

else {

return (t - (k - 1)) / k;

}

else {

assert(round == _PyTime_ROUND_UP);

if (t >= 0) {

return (t + k - 1) / k;

}

else {

return (t - (k - 1)) / k;

}

_PyTime_t

_PyTime_AsMilliseconds(_PyTime_t t, _PyTime_round_t round)

{

return _PyTime_Divide(t, NS_TO_MS, round);

}

_PyTime_t

_PyTime_AsMicroseconds(_PyTime_t t, _PyTime_round_t round)

{

return _PyTime_Divide(t, NS_TO_US, round);

}

static int

_PyTime_AsTimeval_impl(_PyTime_t t, _PyTime_t *p_secs, int *p_us,

_PyTime_round_t round)

{

_PyTime_t secs, ns;

int usec;

int res = 0;

secs = t / SEC_TO_NS;

ns = t % SEC_TO_NS;

usec = (int)_PyTime_Divide(ns, US_TO_NS, round);

if (usec < 0) {

usec += SEC_TO_US;

if (secs != _PyTime_MIN) {

secs -= 1;

}

else {

res = -1;

}

else if (usec >= SEC_TO_US) {

usec -= SEC_TO_US;

if (secs != _PyTime_MAX) {

secs += 1;

}

else {

res = -1;

}

assert(0 <= usec && usec < SEC_TO_US);

*p_secs = secs;

*p_us = usec;

return res;

}

static int

_PyTime_AsTimevalStruct_impl(_PyTime_t t, struct timeval *tv,

_PyTime_round_t round, int raise)

{

_PyTime_t secs, secs2;

int us;

int res;

res = _PyTime_AsTimeval_impl(t, &secs, &us, round);

#ifdef MS_WINDOWS

tv->tv_sec = (long)secs;

#else

tv->tv_sec = secs;

#endif

tv->tv_usec = us;

secs2 = (_PyTime_t)tv->tv_sec;

if (res < 0 || secs2 != secs) {

if (raise) {

error_time_t_overflow();

}

return -1;

}

return 0;

}

int

_PyTime_AsTimeval(_PyTime_t t, struct timeval *tv, _PyTime_round_t round)

{

return _PyTime_AsTimevalStruct_impl(t, tv, round, 1);

}

int

_PyTime_AsTimeval_noraise(_PyTime_t t, struct timeval *tv, _PyTime_round_t round)

{

return _PyTime_AsTimevalStruct_impl(t, tv, round, 0);

}

int

_PyTime_AsTimevalTime_t(_PyTime_t t, time_t *p_secs, int *us,

_PyTime_round_t round)

{

_PyTime_t secs;

int res;

res = _PyTime_AsTimeval_impl(t, &secs, us, round);

*p_secs = secs;

if (res < 0 || (_PyTime_t)*p_secs != secs) {

error_time_t_overflow();

return -1;

}

return 0;

}

#if defined(HAVE_CLOCK_GETTIME) || defined(HAVE_KQUEUE)

int

_PyTime_AsTimespec(_PyTime_t t, struct timespec *ts)

{

_PyTime_t secs, nsec;

secs = t / SEC_TO_NS;

nsec = t % SEC_TO_NS;

if (nsec < 0) {

nsec += SEC_TO_NS;

secs -= 1;

}

ts->tv_sec = (time_t)secs;

assert(0 <= nsec && nsec < SEC_TO_NS);

ts->tv_nsec = nsec;

if ((_PyTime_t)ts->tv_sec != secs) {

error_time_t_overflow();

return -1;

}

return 0;

}

#endif

static int

pygettimeofday(_PyTime_t *tp, _Py_clock_info_t *info, int raise)

{

#ifdef MS_WINDOWS

FILETIME system_time;

ULARGE_INTEGER large;

assert(info == NULL || raise);

GetSystemTimeAsFileTime(&system_time);

large.u.LowPart = system_time.dwLowDateTime;

large.u.HighPart = system_time.dwHighDateTime;

/* 11,644,473,600,000,000,000: number of nanoseconds between

the 1st january 1601 and the 1st january 1970 (369 years + 89 leap

days). */

*tp = large.QuadPart * 100 - 11644473600000000000;

if (info) {

DWORD timeAdjustment, timeIncrement;

BOOL isTimeAdjustmentDisabled, ok;

info->implementation = "GetSystemTimeAsFileTime()";

info->monotonic = 0;

ok = GetSystemTimeAdjustment(&timeAdjustment, &timeIncrement,

&isTimeAdjustmentDisabled);

if (!ok) {

PyErr_SetFromWindowsErr(0);

return -1;

}

info->resolution = timeIncrement * 1e-7;

info->adjustable = 1;

}

#else /* MS_WINDOWS */

int err;

#ifdef HAVE_CLOCK_GETTIME

struct timespec ts;

#else

struct timeval tv;

#endif

assert(info == NULL || raise);

#ifdef HAVE_CLOCK_GETTIME

err = clock_gettime(CLOCK_REALTIME, &ts);

if (err) {

if (raise) {

PyErr_SetFromErrno(PyExc_OSError);

}

return -1;

}

if (pytime_fromtimespec(tp, &ts, raise) < 0) {

return -1;

}

if (info) {

struct timespec res;

info->implementation = "clock_gettime(CLOCK_REALTIME)";

info->monotonic = 0;

info->adjustable = 1;

if (clock_getres(CLOCK_REALTIME, &res) == 0) {

info->resolution = res.tv_sec + res.tv_nsec * 1e-9;

}

else {

info->resolution = 1e-9;

}

#else /* HAVE_CLOCK_GETTIME */

/* test gettimeofday() */

#ifdef GETTIMEOFDAY_NO_TZ

err = gettimeofday(&tv);

#else

err = gettimeofday(&tv, (struct timezone *)NULL);

#endif

if (err) {

if (raise) {

PyErr_SetFromErrno(PyExc_OSError);

}

return -1;

}

if (pytime_fromtimeval(tp, &tv, raise) < 0) {

return -1;

}

if (info) {

info->implementation = "gettimeofday()";

info->resolution = 1e-6;

info->monotonic = 0;

info->adjustable = 1;

}

#endif /* !HAVE_CLOCK_GETTIME */

#endif /* !MS_WINDOWS */

return 0;

}

_PyTime_t

_PyTime_GetSystemClock(void)

{

_PyTime_t t;

if (pygettimeofday(&t, NULL, 0) < 0) {

/* should not happen, _PyTime_Init() checked the clock at startup */

Py_UNREACHABLE();

}

return t;

}

int

_PyTime_GetSystemClockWithInfo(_PyTime_t *t, _Py_clock_info_t *info)

{

return pygettimeofday(t, info, 1);

}

static int

pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)

{

#if defined(MS_WINDOWS)

ULONGLONG ticks;

_PyTime_t t;

assert(info == NULL || raise);

ticks = GetTickCount64();

Py_BUILD_ASSERT(sizeof(ticks) <= sizeof(_PyTime_t));

t = (_PyTime_t)ticks;

if (_PyTime_check_mul_overflow(t, MS_TO_NS)) {

if (raise) {

_PyTime_overflow();

return -1;

}

/* Hello, time traveler! */

Py_UNREACHABLE();

}

*tp = t * MS_TO_NS;

if (info) {

DWORD timeAdjustment, timeIncrement;

BOOL isTimeAdjustmentDisabled, ok;

info->implementation = "GetTickCount64()";

info->monotonic = 1;

ok = GetSystemTimeAdjustment(&timeAdjustment, &timeIncrement,

&isTimeAdjustmentDisabled);

if (!ok) {

PyErr_SetFromWindowsErr(0);

return -1;

}

info->resolution = timeIncrement * 1e-7;

info->adjustable = 0;

}

#elif defined(__APPLE__)

static mach_timebase_info_data_t timebase;

static uint64_t t0 = 0;

uint64_t ticks;

if (timebase.denom == 0) {

/* According to the Technical Q&A QA1398, mach_timebase_info() cannot

fail: https://developer.apple.com/library/mac/#qa/qa1398/ */

(void)mach_timebase_info(&timebase);

/* Sanity check: should never occur in practice */

if (timebase.numer < 1 || timebase.denom < 1) {

PyErr_SetString(PyExc_RuntimeError,

"invalid mach_timebase_info");

return -1;

}

/* Check that timebase.numer and timebase.denom can be casted to

_PyTime_t. In practice, timebase uses uint32_t, so casting cannot

overflow. At the end, only make sure that the type is uint32_t

(_PyTime_t is 64-bit long). */

assert(sizeof(timebase.numer) < sizeof(_PyTime_t));

assert(sizeof(timebase.denom) < sizeof(_PyTime_t));

/* Make sure that (ticks * timebase.numer) cannot overflow in

_PyTime_MulDiv(), with ticks < timebase.denom.

Known time bases:

* always (1, 1) on Intel

* (1000000000, 33333335) or (1000000000, 25000000) on PowerPC

None of these time bases can overflow with 64-bit _PyTime_t, but

check for overflow, just in case. */

if ((_PyTime_t)timebase.numer > _PyTime_MAX / (_PyTime_t)timebase.denom) {

PyErr_SetString(PyExc_OverflowError,

"mach_timebase_info is too large");

return -1;

}

t0 = mach_absolute_time();

}

if (info) {

info->implementation = "mach_absolute_time()";

info->resolution = (double)timebase.numer / (double)timebase.denom * 1e-9;

info->monotonic = 1;

info->adjustable = 0;

}

ticks = mach_absolute_time();

/* Use a "time zero" to reduce precision loss when converting time

to floatting point number, as in time.monotonic(). */

ticks -= t0;

*tp = _PyTime_MulDiv(ticks,

(_PyTime_t)timebase.numer,

(_PyTime_t)timebase.denom);

#elif defined(__hpux)

hrtime_t time;

time = gethrtime();

if (time == -1) {

if (raise) {

PyErr_SetFromErrno(PyExc_OSError);

}

return -1;

}

*tp = time;

if (info) {

info->implementation = "gethrtime()";

info->resolution = 1e-9;

info->monotonic = 1;

info->adjustable = 0;

}

#else

struct timespec ts;

#ifdef CLOCK_HIGHRES

const clockid_t clk_id = CLOCK_HIGHRES;

const char *implementation = "clock_gettime(CLOCK_HIGHRES)";

#else

const clockid_t clk_id = CLOCK_MONOTONIC;

const char *implementation = "clock_gettime(CLOCK_MONOTONIC)";

#endif

assert(info == NULL || raise);

if (clock_gettime(clk_id, &ts) != 0) {

if (raise) {

PyErr_SetFromErrno(PyExc_OSError);

return -1;

}

return -1;

}

if (info) {

struct timespec res;

info->monotonic = 1;

info->implementation = implementation;

info->adjustable = 0;

if (clock_getres(clk_id, &res) != 0) {

PyErr_SetFromErrno(PyExc_OSError);

return -1;

}

info->resolution = res.tv_sec + res.tv_nsec * 1e-9;

}

if (pytime_fromtimespec(tp, &ts, raise) < 0) {

return -1;

}

#endif

return 0;

}

_PyTime_t

_PyTime_GetMonotonicClock(void)

{

_PyTime_t t;

if (pymonotonic(&t, NULL, 0) < 0) {

/* should not happen, _PyTime_Init() checked that monotonic clock at

startup */

Py_UNREACHABLE();

}

return t;

}

int

_PyTime_GetMonotonicClockWithInfo(_PyTime_t *tp, _Py_clock_info_t *info)

{

return pymonotonic(tp, info, 1);

}

#ifdef MS_WINDOWS

static int

win_perf_counter(_PyTime_t *tp, _Py_clock_info_t *info)

{

static LONGLONG frequency = 0;

static LONGLONG t0 = 0;

LARGE_INTEGER now;

LONGLONG ticksll;

_PyTime_t ticks;

if (frequency == 0) {

LARGE_INTEGER freq;

if (!QueryPerformanceFrequency(&freq)) {

PyErr_SetFromWindowsErr(0);

return -1;

}

frequency = freq.QuadPart;

/* Sanity check: should never occur in practice */

if (frequency < 1) {

PyErr_SetString(PyExc_RuntimeError,

"invalid QueryPerformanceFrequency");

return -1;

}

/* Check that frequency can be casted to _PyTime_t.

Make also sure that (ticks * SEC_TO_NS) cannot overflow in

_PyTime_MulDiv(), with ticks < frequency.

Known QueryPerformanceFrequency() values:

* 10,000,000 (10 MHz): 100 ns resolution

* 3,579,545 Hz (3.6 MHz): 279 ns resolution

None of these frequencies can overflow with 64-bit _PyTime_t, but

check for overflow, just in case. */

if (frequency > _PyTime_MAX

|| frequency > (LONGLONG)_PyTime_MAX / (LONGLONG)SEC_TO_NS) {

PyErr_SetString(PyExc_OverflowError,

"QueryPerformanceFrequency is too large");

return -1;

}

QueryPerformanceCounter(&now);

t0 = now.QuadPart;

}

if (info) {

info->implementation = "QueryPerformanceCounter()";

info->resolution = 1.0 / (double)frequency;

info->monotonic = 1;

info->adjustable = 0;

}

QueryPerformanceCounter(&now);

ticksll = now.QuadPart;

/* Use a "time zero" to reduce precision loss when converting time

to floatting point number, as in time.perf_counter(). */

ticksll -= t0;

/* Make sure that casting LONGLONG to _PyTime_t cannot overflow,

both types are signed */

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