111 lines · cpp
1//===-- Windows implementation of clock_getres ------------------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include "hdr/errno_macros.h"10#include "hdr/time_macros.h"11#include "hdr/types/clockid_t.h"12#include "hdr/types/struct_timespec.h"13 14#include "src/__support/CPP/limits.h"15#include "src/__support/common.h"16#include "src/__support/libc_errno.h"17#include "src/__support/macros/optimization.h"18#include "src/__support/time/units.h"19#include "src/__support/time/windows/performance_counter.h"20#include "src/time/clock_getres.h"21 22#define WIN32_LEAN_AND_MEAN23#define NOMINMAX24#include <Windows.h>25 26// add in dependencies for GetSystemTimeAdjustmentPrecise27#pragma comment(lib, "mincore.lib")28 29namespace LIBC_NAMESPACE_DECL {30LLVM_LIBC_FUNCTION(int, clock_getres, (clockid_t id, struct timespec *res)) {31 using namespace time_units;32 // POSIX allows nullptr to be passed as res, in which case the function should33 // do nothing.34 if (res == nullptr)35 return 0;36 constexpr unsigned long long HNS_PER_SEC = 1_s_ns / 100ULL;37 constexpr unsigned long long SEC_LIMIT =38 cpp::numeric_limits<decltype(res->tv_sec)>::max();39 // For CLOCK_MONOTONIC, we are using performance counter40 // https://learn.microsoft.com/en-us/windows/win32/sysinfo/acquiring-high-resolution-time-stamps41 // Hence, the resolution is given by the performance counter frequency.42 // For CLOCK_REALTIME, the precision is given by43 // GetSystemTimeAdjustmentPrecise44 // (https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsystemtimeadjustmentprecise)45 // For CLOCK_PROCESS_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID, the precision is46 // given by GetSystemTimeAdjustment47 // (https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsystemtimeadjustment)48 switch (id) {49 default:50 libc_errno = EINVAL;51 return -1;52 53 case CLOCK_MONOTONIC: {54 long long freq = performance_counter::get_ticks_per_second();55 __builtin_assume(freq != 0);56 // division of 1 second by frequency, rounded up.57 long long tv_sec = static_cast<long long>(freq == 1);58 long long tv_nsec =59 LIBC_LIKELY(freq != 1) ? 1ll + ((1_s_ns - 1ll) / freq) : 0ll;60 // not possible to overflow tv_sec, tv_nsec61 res->tv_sec = static_cast<decltype(res->tv_sec)>(tv_sec);62 res->tv_nsec = static_cast<decltype(res->tv_nsec)>(tv_nsec);63 break;64 }65 66 case CLOCK_REALTIME: {67 [[clang::uninitialized]] DWORD64 time_adjustment;68 [[clang::uninitialized]] DWORD64 time_increment;69 [[clang::uninitialized]] BOOL time_adjustment_disabled;70 if (!::GetSystemTimeAdjustmentPrecise(&time_adjustment, &time_increment,71 &time_adjustment_disabled)) {72 libc_errno = EINVAL;73 return -1;74 }75 DWORD64 tv_sec = time_increment / HNS_PER_SEC;76 DWORD64 tv_nsec = (time_increment % HNS_PER_SEC) * 100ULL;77 if (LIBC_UNLIKELY(tv_sec > SEC_LIMIT)) {78 libc_errno = EOVERFLOW;79 return -1;80 }81 res->tv_sec = static_cast<decltype(res->tv_sec)>(tv_sec);82 res->tv_nsec = static_cast<decltype(res->tv_nsec)>(tv_nsec);83 break;84 }85 case CLOCK_PROCESS_CPUTIME_ID:86 case CLOCK_THREAD_CPUTIME_ID: {87 [[clang::uninitialized]] DWORD time_adjustment;88 [[clang::uninitialized]] DWORD time_increment;89 [[clang::uninitialized]] BOOL time_adjustment_disabled;90 if (!::GetSystemTimeAdjustment(&time_adjustment, &time_increment,91 &time_adjustment_disabled)) {92 libc_errno = EINVAL;93 return -1;94 }95 DWORD hns_per_sec = static_cast<DWORD>(HNS_PER_SEC);96 DWORD sec_limit = static_cast<DWORD>(SEC_LIMIT);97 DWORD tv_sec = time_increment / hns_per_sec;98 DWORD tv_nsec = (time_increment % hns_per_sec) * 100UL;99 if (LIBC_UNLIKELY(tv_sec > sec_limit)) {100 libc_errno = EOVERFLOW;101 return -1;102 }103 res->tv_sec = static_cast<decltype(res->tv_sec)>(tv_sec);104 res->tv_nsec = static_cast<decltype(res->tv_nsec)>(tv_nsec);105 break;106 }107 }108 return 0;109}110} // namespace LIBC_NAMESPACE_DECL111