tool_util: Improve Windows version of tvnow()

- Change tool_util.c tvnow() for Windows to match more closely to
  timeval.c Curl_now().

- Create a win32 init function for the tool, since some initialization
  is required for the tvnow() changes.

Prior to this change the monotonic time function used by curl in Windows
was determined at build-time and not runtime. That was a problem because
when curl was built targeted for compatibility with old versions of
Windows (eg _WIN32_WINNT < 0x0600) it would use GetTickCount which wraps
every 49.7 days that Windows has been running.

This change makes curl behave similar to libcurl's tvnow function, which
determines at runtime whether the OS is Vista+ and if so calls
QueryPerformanceCounter instead. (Note QueryPerformanceCounter is used
because it has higher resolution than the more obvious candidate
GetTickCount64). The changes to tvnow are basically a copy and paste but
the types in some cases are different.

Ref: https://github.com/curl/curl/issues/3309

Closes https://github.com/curl/curl/pull/4847

1 files changed, 25 insertions, 17 deletions

diff --git a/src/tool_util.c b/src/tool_util.c
index 04d73e4e3..ec99bf3f6 100644
--- a/src/tool_util.c
+++ b/src/tool_util.c
@@ -27,27 +27,35 @@
 
 #if defined(WIN32) && !defined(MSDOS)
 
+/* set in win32_init() */
+extern LARGE_INTEGER Curl_freq;
+extern bool Curl_isVistaOrGreater;
+
+/* In case of bug fix this function has a counterpart in timeval.c */
 struct timeval tvnow(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.
-  **
-  ** GetTickCount64() is available on Windows version from Windows Vista
-  ** and Windows Server 2008 up to nowadays. The resolution of the
-  ** function is limited to the resolution of the system timer, which
-  ** is typically in the range of 10 milliseconds to 16 milliseconds.
-  */
   struct timeval now;
-#if defined(_WIN32_WINNT) && (_WIN32_WINNT >= 0x0600) && \
-    (!defined(__MINGW32__) || defined(__MINGW64_VERSION_MAJOR))
-  ULONGLONG milliseconds = GetTickCount64();
-#else
-  DWORD milliseconds = GetTickCount();
+  if(Curl_isVistaOrGreater) { /* QPC timer might have issues pre-Vista */
+    LARGE_INTEGER count;
+    QueryPerformanceCounter(&count);
+    now.tv_sec = (long)(count.QuadPart / Curl_freq.QuadPart);
+    now.tv_usec = (long)((count.QuadPart % Curl_freq.QuadPart) * 1000000 /
+                         Curl_freq.QuadPart);
+  }
+  else {
+    /* Disable /analyze warning that GetTickCount64 is preferred  */
+#if defined(_MSC_VER)
+#pragma warning(push)
+#pragma warning(disable:28159)
+#endif
+    DWORD milliseconds = GetTickCount();
+#if defined(_MSC_VER)
+#pragma warning(pop)
 #endif
-  now.tv_sec = (long)(milliseconds / 1000);
-  now.tv_usec = (long)((milliseconds % 1000) * 1000);
+
+    now.tv_sec = (long)(milliseconds / 1000);
+    now.tv_usec = (long)((milliseconds % 1000) * 1000);
+  }
   return now;
 }