1 | /* timespec -- System time interface |
2 | |
3 | Copyright (C) 2000, 2002, 2004-2005, 2007, 2009-2019 Free Software |
4 | Foundation, Inc. |
5 | |
6 | This program is free software: you can redistribute it and/or modify |
7 | it under the terms of the GNU General Public License as published by |
8 | the Free Software Foundation; either version 3 of the License, or |
9 | (at your option) any later version. |
10 | |
11 | This program is distributed in the hope that it will be useful, |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
14 | GNU General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU General Public License |
17 | along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #if ! defined TIMESPEC_H |
20 | #define TIMESPEC_H |
21 | |
22 | #include <time.h> |
23 | |
24 | #ifndef _GL_INLINE_HEADER_BEGIN |
25 | #error "Please include config.h first." |
26 | #endif |
27 | _GL_INLINE_HEADER_BEGIN |
28 | #ifndef _GL_TIMESPEC_INLINE |
29 | # define _GL_TIMESPEC_INLINE _GL_INLINE |
30 | #endif |
31 | |
32 | #ifdef __cplusplus |
33 | extern "C" { |
34 | #endif |
35 | |
36 | #include "arg-nonnull.h" |
37 | #include "verify.h" |
38 | |
39 | /* Inverse resolution of timespec timestamps (in units per second), |
40 | and log base 10 of the inverse resolution. */ |
41 | |
42 | enum { TIMESPEC_HZ = 1000000000 }; |
43 | enum { LOG10_TIMESPEC_HZ = 9 }; |
44 | |
45 | /* Obsolescent names for backward compatibility. |
46 | They are misnomers, because TIMESPEC_RESOLUTION is not a resolution. */ |
47 | |
48 | enum { TIMESPEC_RESOLUTION = TIMESPEC_HZ }; |
49 | enum { LOG10_TIMESPEC_RESOLUTION = LOG10_TIMESPEC_HZ }; |
50 | |
51 | /* Return a timespec with seconds S and nanoseconds NS. */ |
52 | |
53 | _GL_TIMESPEC_INLINE struct timespec |
54 | make_timespec (time_t s, long int ns) |
55 | { |
56 | struct timespec r; |
57 | r.tv_sec = s; |
58 | r.tv_nsec = ns; |
59 | return r; |
60 | } |
61 | |
62 | /* Return negative, zero, positive if A < B, A == B, A > B, respectively. |
63 | |
64 | For each timestamp T, this code assumes that either: |
65 | |
66 | * T.tv_nsec is in the range 0..999999999; or |
67 | * T.tv_sec corresponds to a valid leap second on a host that supports |
68 | leap seconds, and T.tv_nsec is in the range 1000000000..1999999999; or |
69 | * T.tv_sec is the minimum time_t value and T.tv_nsec is -1; or |
70 | T.tv_sec is the maximum time_t value and T.tv_nsec is 2000000000. |
71 | This allows for special struct timespec values that are less or |
72 | greater than all possible valid timestamps. |
73 | |
74 | In all these cases, it is safe to subtract two tv_nsec values and |
75 | convert the result to integer without worrying about overflow on |
76 | any platform of interest to the GNU project, since all such |
77 | platforms have 32-bit int or wider. |
78 | |
79 | Replacing "a.tv_nsec - b.tv_nsec" with something like |
80 | "a.tv_nsec < b.tv_nsec ? -1 : a.tv_nsec > b.tv_nsec" would cause |
81 | this function to work in some cases where the above assumption is |
82 | violated, but not in all cases (e.g., a.tv_sec==1, a.tv_nsec==-2, |
83 | b.tv_sec==0, b.tv_nsec==999999999) and is arguably not worth the |
84 | extra instructions. Using a subtraction has the advantage of |
85 | detecting some invalid cases on platforms that detect integer |
86 | overflow. */ |
87 | |
88 | _GL_TIMESPEC_INLINE int _GL_ATTRIBUTE_PURE |
89 | timespec_cmp (struct timespec a, struct timespec b) |
90 | { |
91 | if (a.tv_sec < b.tv_sec) |
92 | return -1; |
93 | if (a.tv_sec > b.tv_sec) |
94 | return 1; |
95 | |
96 | /* Pacify gcc -Wstrict-overflow (bleeding-edge circa 2017-10-02). See: |
97 | https://lists.gnu.org/r/bug-gnulib/2017-10/msg00006.html */ |
98 | assume (-1 <= a.tv_nsec && a.tv_nsec <= 2 * TIMESPEC_HZ); |
99 | assume (-1 <= b.tv_nsec && b.tv_nsec <= 2 * TIMESPEC_HZ); |
100 | |
101 | return a.tv_nsec - b.tv_nsec; |
102 | } |
103 | |
104 | /* Return -1, 0, 1, depending on the sign of A. A.tv_nsec must be |
105 | nonnegative. */ |
106 | _GL_TIMESPEC_INLINE int _GL_ATTRIBUTE_PURE |
107 | timespec_sign (struct timespec a) |
108 | { |
109 | return a.tv_sec < 0 ? -1 : a.tv_sec || a.tv_nsec; |
110 | } |
111 | |
112 | struct timespec timespec_add (struct timespec, struct timespec) |
113 | _GL_ATTRIBUTE_CONST; |
114 | struct timespec timespec_sub (struct timespec, struct timespec) |
115 | _GL_ATTRIBUTE_CONST; |
116 | struct timespec dtotimespec (double) |
117 | _GL_ATTRIBUTE_CONST; |
118 | |
119 | /* Return an approximation to A, of type 'double'. */ |
120 | _GL_TIMESPEC_INLINE double |
121 | timespectod (struct timespec a) |
122 | { |
123 | return a.tv_sec + a.tv_nsec / 1e9; |
124 | } |
125 | |
126 | struct timespec current_timespec (void); |
127 | void gettime (struct timespec *) _GL_ARG_NONNULL ((1)); |
128 | int settime (struct timespec const *) _GL_ARG_NONNULL ((1)); |
129 | |
130 | #ifdef __cplusplus |
131 | } |
132 | #endif |
133 | |
134 | _GL_INLINE_HEADER_END |
135 | |
136 | #endif |
137 | |