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 Lesser General Public License as published by
7 the Free Software Foundation; either version 2.1, 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 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser 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 #include "localtime-buffer.h"
33
34 #ifdef WINDOWS_NATIVE
35
36 # if !(_WIN32_WINNT >= _WIN32_WINNT_WIN8)
37
38 /* Avoid warnings from gcc -Wcast-function-type. */
39 # define GetProcAddress \
40 (void *) GetProcAddress
41
42 /* GetSystemTimePreciseAsFileTime was introduced only in Windows 8. */
43 typedef void (WINAPI * GetSystemTimePreciseAsFileTimeFuncType) (FILETIME *lpTime);
44 static GetSystemTimePreciseAsFileTimeFuncType GetSystemTimePreciseAsFileTimeFunc = NULL;
45 static BOOL initialized = FALSE;
46
47 static void
initialize(void)48 initialize (void)
49 {
50 HMODULE kernel32 = LoadLibrary ("kernel32.dll");
51 if (kernel32 != NULL)
52 {
53 GetSystemTimePreciseAsFileTimeFunc =
54 (GetSystemTimePreciseAsFileTimeFuncType) GetProcAddress (kernel32, "GetSystemTimePreciseAsFileTime");
55 }
56 initialized = TRUE;
57 }
58
59 # else
60
61 # define GetSystemTimePreciseAsFileTimeFunc GetSystemTimePreciseAsFileTime
62
63 # endif
64
65 #endif
66
67 /* This is a wrapper for gettimeofday. It is used only on systems
68 that lack this function, or whose implementation of this function
69 causes problems.
70 Work around the bug in some systems whereby gettimeofday clobbers
71 the static buffer that localtime uses for its return value. The
72 gettimeofday function from Mac OS X 10.0.4 (i.e., Darwin 1.3.7) has
73 this problem. */
74
75 int
gettimeofday(struct timeval * restrict tv,void * restrict tz)76 gettimeofday (struct timeval *restrict tv, void *restrict tz)
77 {
78 #undef gettimeofday
79 #ifdef WINDOWS_NATIVE
80
81 /* On native Windows, there are two ways to get the current time:
82 GetSystemTimeAsFileTime
83 <https://docs.microsoft.com/en-us/windows/desktop/api/sysinfoapi/nf-sysinfoapi-getsystemtimeasfiletime>
84 or
85 GetSystemTimePreciseAsFileTime
86 <https://docs.microsoft.com/en-us/windows/desktop/api/sysinfoapi/nf-sysinfoapi-getsystemtimepreciseasfiletime>.
87 GetSystemTimeAsFileTime produces values that jump by increments of
88 15.627 milliseconds (!) on average.
89 Whereas GetSystemTimePreciseAsFileTime values usually jump by 1 or 2
90 microseconds.
91 More discussion on this topic:
92 <http://www.windowstimestamp.com/description>. */
93 FILETIME current_time;
94
95 # if !(_WIN32_WINNT >= _WIN32_WINNT_WIN8)
96 if (!initialized)
97 initialize ();
98 # endif
99 if (GetSystemTimePreciseAsFileTimeFunc != NULL)
100 GetSystemTimePreciseAsFileTimeFunc (¤t_time);
101 else
102 GetSystemTimeAsFileTime (¤t_time);
103
104 /* Convert from FILETIME to 'struct timeval'. */
105 /* FILETIME: <https://docs.microsoft.com/en-us/windows/desktop/api/minwinbase/ns-minwinbase-filetime> */
106 ULONGLONG since_1601 =
107 ((ULONGLONG) current_time.dwHighDateTime << 32)
108 | (ULONGLONG) current_time.dwLowDateTime;
109 /* Between 1601-01-01 and 1970-01-01 there were 280 normal years and 89 leap
110 years, in total 134774 days. */
111 ULONGLONG since_1970 =
112 since_1601 - (ULONGLONG) 134774 * (ULONGLONG) 86400 * (ULONGLONG) 10000000;
113 ULONGLONG microseconds_since_1970 = since_1970 / (ULONGLONG) 10;
114 tv->tv_sec = microseconds_since_1970 / (ULONGLONG) 1000000;
115 tv->tv_usec = microseconds_since_1970 % (ULONGLONG) 1000000;
116
117 return 0;
118
119 #else
120
121 # if HAVE_GETTIMEOFDAY
122 # if GETTIMEOFDAY_CLOBBERS_LOCALTIME
123 /* Save and restore the contents of the buffer used for localtime's
124 result around the call to gettimeofday. */
125 struct tm save = *localtime_buffer_addr;
126 # endif
127
128 # if defined timeval /* 'struct timeval' overridden by gnulib? */
129 # undef timeval
130 struct timeval otv;
131 int result = gettimeofday (&otv, (struct timezone *) tz);
132 if (result == 0)
133 {
134 tv->tv_sec = otv.tv_sec;
135 tv->tv_usec = otv.tv_usec;
136 }
137 # else
138 int result = gettimeofday (tv, (struct timezone *) tz);
139 # endif
140
141 # if GETTIMEOFDAY_CLOBBERS_LOCALTIME
142 *localtime_buffer_addr = save;
143 # endif
144
145 return result;
146
147 # else
148
149 # if !defined OK_TO_USE_1S_CLOCK
150 # error "Only 1-second nominal clock resolution found. Is that intended?" \
151 "If so, compile with the -DOK_TO_USE_1S_CLOCK option."
152 # endif
153 tv->tv_sec = time (NULL);
154 tv->tv_usec = 0;
155
156 return 0;
157
158 # endif
159 #endif
160 }
161