1 /* Provide a replacement for the POSIX nanosleep function.
2
3 Copyright (C) 1999-2000, 2002, 2004-2023 Free Software Foundation, Inc.
4
5 This file is free software: you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as
7 published by the Free Software Foundation; either version 2.1 of the
8 License, or (at your option) any later version.
9
10 This file 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 and Bruno Haible for the native Windows part */
20
21 #include <config.h>
22
23 #include <time.h>
24
25 #include "intprops.h"
26
27 #include <stdio.h>
28 #include <sys/types.h>
29 #include <sys/select.h>
30 #include <signal.h>
31
32 #include <errno.h>
33
34 #include <unistd.h>
35
36
37 enum { BILLION = 1000 * 1000 * 1000 };
38
39 #if HAVE_BUG_BIG_NANOSLEEP
40
41 int
42 nanosleep (const struct timespec *requested_delay,
43 struct timespec *remaining_delay)
44 # undef nanosleep
45 {
46 /* nanosleep mishandles large sleeps due to internal overflow problems.
47 The worst known case of this is Linux 2.6.9 with glibc 2.3.4, which
48 can't sleep more than 24.85 days (2^31 milliseconds). Similarly,
49 cygwin 1.5.x, which can't sleep more than 49.7 days (2^32 milliseconds).
50 Solve this by breaking the sleep up into smaller chunks. */
51
52 if (requested_delay->tv_nsec < 0 || BILLION <= requested_delay->tv_nsec)
53 {
54 errno = EINVAL;
55 return -1;
56 }
57
58 {
59 /* Verify that time_t is large enough. */
60 static_assert (TYPE_MAXIMUM (time_t) / 24 / 24 / 60 / 60);
61 const time_t limit = 24 * 24 * 60 * 60;
62 time_t seconds = requested_delay->tv_sec;
63 struct timespec intermediate = *requested_delay;
64
65 while (limit < seconds)
66 {
67 int result;
68 intermediate.tv_sec = limit;
69 result = nanosleep (&intermediate, remaining_delay);
70 seconds -= limit;
71 if (result)
72 {
73 if (remaining_delay)
74 remaining_delay->tv_sec += seconds;
75 return result;
76 }
77 intermediate.tv_nsec = 0;
78 }
79 intermediate.tv_sec = seconds;
80 return nanosleep (&intermediate, remaining_delay);
81 }
82 }
83
84 #elif defined _WIN32 && ! defined __CYGWIN__
85 /* Native Windows platforms. */
86
87 # define WIN32_LEAN_AND_MEAN
88 # include <windows.h>
89
90 /* The Windows API function Sleep() has a resolution of about 15 ms and takes
91 at least 5 ms to execute. We use this function for longer time periods.
92 Additionally, we use busy-looping over short time periods, to get a
93 resolution of about 0.01 ms. In order to measure such short timespans,
94 we use the QueryPerformanceCounter() function. */
95
96 int
97 nanosleep (const struct timespec *requested_delay,
98 struct timespec *remaining_delay)
99 {
100 static bool initialized;
101 /* Number of performance counter increments per nanosecond,
102 or zero if it could not be determined. */
103 static double ticks_per_nanosecond;
104
105 if (requested_delay->tv_nsec < 0 || BILLION <= requested_delay->tv_nsec)
106 {
107 errno = EINVAL;
108 return -1;
109 }
110
111 /* For requested delays of one second or more, 15ms resolution is
112 sufficient. */
113 if (requested_delay->tv_sec == 0)
114 {
115 if (!initialized)
116 {
117 /* Initialize ticks_per_nanosecond. */
118 LARGE_INTEGER ticks_per_second;
119
120 if (QueryPerformanceFrequency (&ticks_per_second))
121 ticks_per_nanosecond =
122 (double) ticks_per_second.QuadPart / 1000000000.0;
123
124 initialized = true;
125 }
126 if (ticks_per_nanosecond)
127 {
128 /* QueryPerformanceFrequency worked. We can use
129 QueryPerformanceCounter. Use a combination of Sleep and
130 busy-looping. */
131 /* Number of milliseconds to pass to the Sleep function.
132 Since Sleep can take up to 8 ms less or 8 ms more than requested
133 (or maybe more if the system is loaded), we subtract 10 ms. */
134 int sleep_millis = (int) requested_delay->tv_nsec / 1000000 - 10;
135 /* Determine how many ticks to delay. */
136 LONGLONG wait_ticks = requested_delay->tv_nsec * ticks_per_nanosecond;
137 /* Start. */
138 LARGE_INTEGER counter_before;
139 if (QueryPerformanceCounter (&counter_before))
140 {
141 /* Wait until the performance counter has reached this value.
142 We don't need to worry about overflow, because the performance
143 counter is reset at reboot, and with a frequency of 3.6E6
144 ticks per second 63 bits suffice for over 80000 years. */
145 LONGLONG wait_until = counter_before.QuadPart + wait_ticks;
146 /* Use Sleep for the longest part. */
147 if (sleep_millis > 0)
148 Sleep (sleep_millis);
149 /* Busy-loop for the rest. */
150 for (;;)
151 {
152 LARGE_INTEGER counter_after;
153 if (!QueryPerformanceCounter (&counter_after))
154 /* QueryPerformanceCounter failed, but succeeded earlier.
155 Should not happen. */
156 break;
157 if (counter_after.QuadPart >= wait_until)
158 /* The requested time has elapsed. */
159 break;
160 }
161 goto done;
162 }
163 }
164 }
165 /* Implementation for long delays and as fallback. */
166 Sleep (requested_delay->tv_sec * 1000 + requested_delay->tv_nsec / 1000000);
167
168 done:
169 /* Sleep is not interruptible. So there is no remaining delay. */
170 if (remaining_delay != NULL)
171 {
172 remaining_delay->tv_sec = 0;
173 remaining_delay->tv_nsec = 0;
174 }
175 return 0;
176 }
177
178 #else
179 /* Other platforms lacking nanosleep.
180 It's not clear whether these are still practical porting targets.
181 For now, just fall back on pselect. */
182
183 /* Suspend execution for at least *REQUESTED_DELAY seconds. The
184 *REMAINING_DELAY part isn't implemented yet. */
185
186 int
187 nanosleep (const struct timespec *requested_delay,
188 struct timespec *remaining_delay)
189 {
190 return pselect (0, NULL, NULL, NULL, requested_delay, NULL);
191 }
192 #endif