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//===-- Windows implementation of clock_getres ------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "hdr/errno_macros.h"
#include "hdr/time_macros.h"
#include "hdr/types/clockid_t.h"
#include "hdr/types/struct_timespec.h"
#include "src/__support/CPP/limits.h"
#include "src/__support/common.h"
#include "src/__support/libc_errno.h"
#include "src/__support/macros/optimization.h"
#include "src/__support/time/units.h"
#include "src/__support/time/windows/performance_counter.h"
#include "src/time/clock_getres.h"
#define WIN32_LEAN_AND_MEAN
#define NOMINMAX
#include <Windows.h>
// add in dependencies for GetSystemTimeAdjustmentPrecise
#pragma comment(lib, "mincore.lib")
namespace LIBC_NAMESPACE_DECL {
LLVM_LIBC_FUNCTION(int, clock_getres, (clockid_t id, struct timespec *res)) {
using namespace time_units;
// POSIX allows nullptr to be passed as res, in which case the function should
// do nothing.
if (res == nullptr)
return 0;
constexpr unsigned long long HNS_PER_SEC = 1_s_ns / 100ULL;
constexpr unsigned long long SEC_LIMIT =
cpp::numeric_limits<decltype(res->tv_sec)>::max();
// For CLOCK_MONOTONIC, we are using performance counter
// https://learn.microsoft.com/en-us/windows/win32/sysinfo/acquiring-high-resolution-time-stamps
// Hence, the resolution is given by the performance counter frequency.
// For CLOCK_REALTIME, the precision is given by
// GetSystemTimeAdjustmentPrecise
// (https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsystemtimeadjustmentprecise)
// For CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID, the precision is
// given by GetSystemTimeAdjustment
// (https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsystemtimeadjustment)
switch (id) {
default:
libc_errno = EINVAL;
return -1;
case CLOCK_MONOTONIC: {
long long freq = performance_counter::get_ticks_per_second();
__builtin_assume(freq != 0);
// division of 1 second by frequency, rounded up.
long long tv_sec = static_cast<long long>(freq == 1);
long long tv_nsec =
LIBC_LIKELY(freq != 1) ? 1ll + ((1_s_ns - 1ll) / freq) : 0ll;
// not possible to overflow tv_sec, tv_nsec
res->tv_sec = static_cast<decltype(res->tv_sec)>(tv_sec);
res->tv_nsec = static_cast<decltype(res->tv_nsec)>(tv_nsec);
break;
}
case CLOCK_REALTIME: {
[[clang::uninitialized]] DWORD64 time_adjustment;
[[clang::uninitialized]] DWORD64 time_increment;
[[clang::uninitialized]] BOOL time_adjustment_disabled;
if (!::GetSystemTimeAdjustmentPrecise(&time_adjustment, &time_increment,
&time_adjustment_disabled)) {
libc_errno = EINVAL;
return -1;
}
DWORD64 tv_sec = time_increment / HNS_PER_SEC;
DWORD64 tv_nsec = (time_increment % HNS_PER_SEC) * 100ULL;
if (LIBC_UNLIKELY(tv_sec > SEC_LIMIT)) {
libc_errno = EOVERFLOW;
return -1;
}
res->tv_sec = static_cast<decltype(res->tv_sec)>(tv_sec);
res->tv_nsec = static_cast<decltype(res->tv_nsec)>(tv_nsec);
break;
}
case CLOCK_PROCESS_CPUTIME_ID:
case CLOCK_THREAD_CPUTIME_ID: {
[[clang::uninitialized]] DWORD time_adjustment;
[[clang::uninitialized]] DWORD time_increment;
[[clang::uninitialized]] BOOL time_adjustment_disabled;
if (!::GetSystemTimeAdjustment(&time_adjustment, &time_increment,
&time_adjustment_disabled)) {
libc_errno = EINVAL;
return -1;
}
DWORD hns_per_sec = static_cast<DWORD>(HNS_PER_SEC);
DWORD sec_limit = static_cast<DWORD>(SEC_LIMIT);
DWORD tv_sec = time_increment / hns_per_sec;
DWORD tv_nsec = (time_increment % hns_per_sec) * 100UL;
if (LIBC_UNLIKELY(tv_sec > sec_limit)) {
libc_errno = EOVERFLOW;
return -1;
}
res->tv_sec = static_cast<decltype(res->tv_sec)>(tv_sec);
res->tv_nsec = static_cast<decltype(res->tv_nsec)>(tv_nsec);
break;
}
}
return 0;
}
} // namespace LIBC_NAMESPACE_DECL
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