Commit e9ababd4 authored by Pavel Pavlov's avatar Pavel Pavlov Committed by Jay Satiro
Browse files

timeval: Use high resolution timestamps on Windows 

- Use QueryPerformanceCounter on Windows Vista+

There is confusing info floating around that QueryPerformanceCounter
can leap etc, which might have been true long time ago, but no longer
the case nowadays (perhaps starting from WinXP?). Also, boost and
std::chrono::steady_clock use QueryPerformanceCounter in a similar way.

Prior to this change GetTickCount or GetTickCount64 was used, which has
lower resolution. That is still the case for <= XP.

Fixes https://github.com/curl/curl/issues/3309
Closes https://github.com/curl/curl/pull/3318
parent c98ee5f6

lib/timeval.c

+24 −17
Original line number Diff line number Diff line
@@ -21,29 +21,36 @@ 
 ***************************************************************************/



#include "timeval.h"

#include "system_win32.h"



#if defined(WIN32) && !defined(MSDOS)



struct curltime Curl_now(void)

{

  /*

  ** GetTickCount() is available on _all_ Windows versions from W95 up

  ** to nowadays. Returns milliseconds elapsed since last system boot,

  ** increases monotonically and wraps once 49.7 days have elapsed.

  */

  struct curltime now;

#if !defined(_WIN32_WINNT) || !defined(_WIN32_WINNT_VISTA) || \

    (_WIN32_WINNT < _WIN32_WINNT_VISTA) || \

    (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR))

  static LARGE_INTEGER freq;

  static int isVistaOrGreater = -1;

  if(isVistaOrGreater == -1) {

    if(Curl_verify_windows_version(6, 0, PLATFORM_WINNT,

                                   VERSION_GREATER_THAN_EQUAL)) {

      isVistaOrGreater = 1;

      QueryPerformanceFrequency(&freq);

    }

    else

      isVistaOrGreater = 0;

  }

  if(isVistaOrGreater == 1) { /* QPC timer might have issues pre-Vista */

    LARGE_INTEGER count;

    QueryPerformanceCounter(&count);

    now.tv_sec = (time_t)(count.QuadPart / freq.QuadPart);

    now.tv_usec =

      (int)((count.QuadPart % freq.QuadPart) * 1000000 / freq.QuadPart);

  }

  else {

    DWORD milliseconds = GetTickCount();

    now.tv_sec = milliseconds / 1000;

    now.tv_usec = (milliseconds % 1000) * 1000;

#else

  ULONGLONG milliseconds = GetTickCount64();

  now.tv_sec = (time_t) (milliseconds / 1000);

  now.tv_usec = (unsigned int) (milliseconds % 1000) * 1000;

#endif



  }

  return now;

}