1 /* Provide gettimeofday for systems that don't have it or for which it's broken.
2
3 Copyright (C) 2001-2003, 2005-2007, 2009-2020 Free Software Foundation, Inc.
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3, or (at your option)
8 any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, see <https://www.gnu.org/licenses/>. */
17
18 /* written by Jim Meyering */
19
20 #include <config.h>
21
22 /* Specification. */
23 #include <sys/time.h>
24
25 #include <time.h>
26
27 #if defined _WIN32 && ! defined __CYGWIN__
28 # define WINDOWS_NATIVE
29 # include <windows.h>
30 #endif
31
32 #ifdef WINDOWS_NATIVE
33
34 /* Don't assume that UNICODE is not defined. */
35 # undef LoadLibrary
36 # define LoadLibrary LoadLibraryA
37
38 # if !(_WIN32_WINNT >= _WIN32_WINNT_WIN8)
39
40 /* Avoid warnings from gcc -Wcast-function-type. */
41 # define GetProcAddress \
42 (void *) GetProcAddress
43
44 /* GetSystemTimePreciseAsFileTime was introduced only in Windows 8. */
45 typedef void (WINAPI * GetSystemTimePreciseAsFileTimeFuncType) (FILETIME *lpTime);
46 static GetSystemTimePreciseAsFileTimeFuncType GetSystemTimePreciseAsFileTimeFunc = NULL;
47 static BOOL initialized = FALSE;
48
49 static void
initialize(void)50 initialize (void)
51 {
52 HMODULE kernel32 = LoadLibrary ("kernel32.dll");
53 if (kernel32 != NULL)
54 {
55 GetSystemTimePreciseAsFileTimeFunc =
56 (GetSystemTimePreciseAsFileTimeFuncType) GetProcAddress (kernel32, "GetSystemTimePreciseAsFileTime");
57 }
58 initialized = TRUE;
59 }
60
61 # else
62
63 # define GetSystemTimePreciseAsFileTimeFunc GetSystemTimePreciseAsFileTime
64
65 # endif
66
67 #endif
68
69 /* This is a wrapper for gettimeofday. It is used only on systems
70 that lack this function, or whose implementation of this function
71 causes problems.
72 Work around the bug in some systems whereby gettimeofday clobbers
73 the static buffer that localtime uses for its return value. The
74 gettimeofday function from Mac OS X 10.0.4 (i.e., Darwin 1.3.7) has
75 this problem. */
76
77 int
gettimeofday(struct timeval * restrict tv,void * restrict tz)78 gettimeofday (struct timeval *restrict tv, void *restrict tz)
79 {
80 #undef gettimeofday
81 #ifdef WINDOWS_NATIVE
82
83 /* On native Windows, there are two ways to get the current time:
84 GetSystemTimeAsFileTime
85 <https://docs.microsoft.com/en-us/windows/desktop/api/sysinfoapi/nf-sysinfoapi-getsystemtimeasfiletime>
86 or
87 GetSystemTimePreciseAsFileTime
88 <https://docs.microsoft.com/en-us/windows/desktop/api/sysinfoapi/nf-sysinfoapi-getsystemtimepreciseasfiletime>.
89 GetSystemTimeAsFileTime produces values that jump by increments of
90 15.627 milliseconds (!) on average.
91 Whereas GetSystemTimePreciseAsFileTime values usually jump by 1 or 2
92 microseconds.
93 More discussion on this topic:
94 <http://www.windowstimestamp.com/description>. */
95 FILETIME current_time;
96
97 # if !(_WIN32_WINNT >= _WIN32_WINNT_WIN8)
98 if (!initialized)
99 initialize ();
100 # endif
101 if (GetSystemTimePreciseAsFileTimeFunc != NULL)
102 GetSystemTimePreciseAsFileTimeFunc (¤t_time);
103 else
104 GetSystemTimeAsFileTime (¤t_time);
105
106 /* Convert from FILETIME to 'struct timeval'. */
107 /* FILETIME: <https://docs.microsoft.com/en-us/windows/desktop/api/minwinbase/ns-minwinbase-filetime> */
108 ULONGLONG since_1601 =
109 ((ULONGLONG) current_time.dwHighDateTime << 32)
110 | (ULONGLONG) current_time.dwLowDateTime;
111 /* Between 1601-01-01 and 1970-01-01 there were 280 normal years and 89 leap
112 years, in total 134774 days. */
113 ULONGLONG since_1970 =
114 since_1601 - (ULONGLONG) 134774 * (ULONGLONG) 86400 * (ULONGLONG) 10000000;
115 ULONGLONG microseconds_since_1970 = since_1970 / (ULONGLONG) 10;
116 tv->tv_sec = microseconds_since_1970 / (ULONGLONG) 1000000;
117 tv->tv_usec = microseconds_since_1970 % (ULONGLONG) 1000000;
118
119 return 0;
120
121 #else
122
123 # if HAVE_GETTIMEOFDAY
124
125 # if defined timeval /* 'struct timeval' overridden by gnulib? */
126 # undef timeval
127 struct timeval otv;
128 int result = gettimeofday (&otv, (struct timezone *) tz);
129 if (result == 0)
130 {
131 tv->tv_sec = otv.tv_sec;
132 tv->tv_usec = otv.tv_usec;
133 }
134 # else
135 int result = gettimeofday (tv, (struct timezone *) tz);
136 # endif
137
138 return result;
139
140 # else
141
142 # if !defined OK_TO_USE_1S_CLOCK
143 # error "Only 1-second nominal clock resolution found. Is that intended?" \
144 "If so, compile with the -DOK_TO_USE_1S_CLOCK option."
145 # endif
146 tv->tv_sec = time (NULL);
147 tv->tv_usec = 0;
148
149 return 0;
150
151 # endif
152 #endif
153 }
154