src/port/gettimeofday.c

   1 /*
   2  * gettimeofday.c
   3  *        Win32 gettimeofday() replacement
   4  *
   5  * src/port/gettimeofday.c
   6  *
   7  * Copyright (c) 2003 SRA, Inc.
   8  * Copyright (c) 2003 SKC, Inc.
   9  *
  10  * Permission to use, copy, modify, and distribute this software and
  11  * its documentation for any purpose, without fee, and without a
  12  * written agreement is hereby granted, provided that the above
  13  * copyright notice and this paragraph and the following two
  14  * paragraphs appear in all copies.
  15  *
  16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
  17  * INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
  18  * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
  19  * DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
  20  * OF THE POSSIBILITY OF SUCH DAMAGE.
  21  *
  22  * THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  24  * A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
  25  * IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
  26  * SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  27  */
  28
  29 #include "c.h"
  30
  31 #include <sys/time.h>
  32
  33 /* FILETIME of Jan 1 1970 00:00:00, the PostgreSQL epoch */
  34 static const unsigned __int64 epoch = UINT64CONST(116444736000000000);
  35
  36 /*
  37  * FILETIME represents the number of 100-nanosecond intervals since
  38  * January 1, 1601 (UTC).
  39  */
  40 #define FILETIME_UNITS_PER_SEC  10000000L
  41 #define FILETIME_UNITS_PER_USEC 10
  42
  43 /*
  44  * Both GetSystemTimeAsFileTime and GetSystemTimePreciseAsFileTime share a
  45  * signature, so we can just store a pointer to whichever we find. This
  46  * is the pointer's type.
  47  */
  48 typedef VOID(WINAPI * PgGetSystemTimeFn) (LPFILETIME);
  49
  50 /* One-time initializer function, must match that signature. */
  51 static void WINAPI init_gettimeofday(LPFILETIME lpSystemTimeAsFileTime);
  52
  53 /* Storage for the function we pick at runtime */
  54 static PgGetSystemTimeFn pg_get_system_time = &init_gettimeofday;
  55
  56 /*
  57  * One time initializer.  Determine whether GetSystemTimePreciseAsFileTime
  58  * is available and if so, plan to use it; if not, fall back to
  59  * GetSystemTimeAsFileTime.
  60  */
  61 static void WINAPI
  62 init_gettimeofday(LPFILETIME lpSystemTimeAsFileTime)
  63 {
  64         /*
  65          * Because it's guaranteed that kernel32.dll will be linked into our
  66          * address space already, we don't need to LoadLibrary it and worry about
  67          * closing it afterwards, so we're not using Pg's dlopen/dlsym() wrapper.
  68          *
  69          * We'll just look up the address of GetSystemTimePreciseAsFileTime if
  70          * present.
  71          *
  72          * While we could look up the Windows version and skip this on Windows
  73          * versions below Windows 8 / Windows Server 2012 there isn't much point,
  74          * and determining the windows version is its self somewhat Windows
  75          * version and development SDK specific...
  76          */
  77         pg_get_system_time = (PgGetSystemTimeFn) GetProcAddress(GetModuleHandle(TEXT("kernel32.dll")),
  78                                                                                                                         "GetSystemTimePreciseAsFileTime");
  79         if (pg_get_system_time == NULL)
  80         {
  81                 /*
  82                  * The expected error from GetLastError() is ERROR_PROC_NOT_FOUND, if
  83                  * the function isn't present. No other error should occur.
  84                  *
  85                  * We can't report an error here because this might be running in
  86                  * frontend code; and even if we're in the backend, it's too early to
  87                  * elog(...) if we get some unexpected error.  Also, it's not a
  88                  * serious problem, so just silently fall back to
  89                  * GetSystemTimeAsFileTime irrespective of why the failure occurred.
  90                  */
  91                 pg_get_system_time = &GetSystemTimeAsFileTime;
  92         }
  93
  94         (*pg_get_system_time) (lpSystemTimeAsFileTime);
  95 }
  96
  97 /*
  98  * timezone information is stored outside the kernel so tzp isn't used anymore.
  99  *
 100  * Note: this function is not for Win32 high precision timing purposes. See
 101  * elapsed_time().
 102  */
 103 int
 104 gettimeofday(struct timeval *tp, struct timezone *tzp)
 105 {
 106         FILETIME        file_time;
 107         ULARGE_INTEGER ularge;
 108
 109         (*pg_get_system_time) (&file_time);
 110         ularge.LowPart = file_time.dwLowDateTime;
 111         ularge.HighPart = file_time.dwHighDateTime;
 112
 113         tp->tv_sec = (long) ((ularge.QuadPart - epoch) / FILETIME_UNITS_PER_SEC);
 114         tp->tv_usec = (long) (((ularge.QuadPart - epoch) % FILETIME_UNITS_PER_SEC)
 115                                                   / FILETIME_UNITS_PER_USEC);
 116
 117         return 0;
 118 }