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#include "os/os.h"
#include <windows.h>
void os_clk_tck(long *clk_tck)
{
/*
* The timer resolution is variable on Windows. Try to query it
* or use 64 Hz, the clock frequency lower bound. See also
* https://carpediemsystems.co.uk/2019/07/18/windows-system-timer-granularity/.
*/
unsigned long minRes, maxRes, curRes;
HMODULE lib;
NTSTATUS NTAPI (*queryTimer)
(OUT PULONG MinimumResolution,
OUT PULONG MaximumResolution,
OUT PULONG CurrentResolution);
NTSTATUS NTAPI (*setTimer)
(IN ULONG DesiredResolution,
IN BOOLEAN SetResolution,
OUT PULONG CurrentResolution);
if (!(lib = LoadLibrary(TEXT("ntdll.dll"))) ||
!(queryTimer = (void *)GetProcAddress(lib, "NtQueryTimerResolution")) ||
!(setTimer = (void *)GetProcAddress(lib, "NtSetTimerResolution"))) {
dprint(FD_HELPERTHREAD,
"Failed to load ntdll library, set to lower bound 64 Hz\n");
*clk_tck = 64;
} else {
queryTimer(&minRes, &maxRes, &curRes);
dprint(FD_HELPERTHREAD,
"minRes = %lu, maxRes = %lu, curRes = %lu\n",
minRes, maxRes, curRes);
/* Use maximum resolution for most accurate timestamps */
setTimer(maxRes, 1, &curRes);
*clk_tck = (long) (10000000L / maxRes);
}
}
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