| 1 | /* timespec -- System time interface |
| 2 | |
| 3 | Copyright (C) 2000, 2002, 2004-2005, 2007, 2009-2013 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 <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #if ! defined TIMESPEC_H |
| 20 | # define TIMESPEC_H |
| 21 | |
| 22 | # include <time.h> |
| 23 | |
| 24 | _GL_INLINE_HEADER_BEGIN |
| 25 | #ifndef _GL_TIMESPEC_INLINE |
| 26 | # define _GL_TIMESPEC_INLINE _GL_INLINE |
| 27 | #endif |
| 28 | |
| 29 | /* Resolution of timespec time stamps (in units per second), and log |
| 30 | base 10 of the resolution. */ |
| 31 | |
| 32 | enum { TIMESPEC_RESOLUTION = 1000000000 }; |
| 33 | enum { LOG10_TIMESPEC_RESOLUTION = 9 }; |
| 34 | |
| 35 | /* Return a timespec with seconds S and nanoseconds NS. */ |
| 36 | |
| 37 | _GL_TIMESPEC_INLINE struct timespec |
| 38 | make_timespec (time_t s, long int ns) |
| 39 | { |
| 40 | struct timespec r; |
| 41 | r.tv_sec = s; |
| 42 | r.tv_nsec = ns; |
| 43 | return r; |
| 44 | } |
| 45 | |
| 46 | /* Return negative, zero, positive if A < B, A == B, A > B, respectively. |
| 47 | |
| 48 | For each time stamp T, this code assumes that either: |
| 49 | |
| 50 | * T.tv_nsec is in the range 0..999999999; or |
| 51 | * T.tv_sec corresponds to a valid leap second on a host that supports |
| 52 | leap seconds, and T.tv_nsec is in the range 1000000000..1999999999; or |
| 53 | * T.tv_sec is the minimum time_t value and T.tv_nsec is -1; or |
| 54 | T.tv_sec is the maximum time_t value and T.tv_nsec is 2000000000. |
| 55 | This allows for special struct timespec values that are less or |
| 56 | greater than all possible valid time stamps. |
| 57 | |
| 58 | In all these cases, it is safe to subtract two tv_nsec values and |
| 59 | convert the result to integer without worrying about overflow on |
| 60 | any platform of interest to the GNU project, since all such |
| 61 | platforms have 32-bit int or wider. |
| 62 | |
| 63 | Replacing "(int) (a.tv_nsec - b.tv_nsec)" with something like |
| 64 | "a.tv_nsec < b.tv_nsec ? -1 : a.tv_nsec > b.tv_nsec" would cause |
| 65 | this function to work in some cases where the above assumption is |
| 66 | violated, but not in all cases (e.g., a.tv_sec==1, a.tv_nsec==-2, |
| 67 | b.tv_sec==0, b.tv_nsec==999999999) and is arguably not worth the |
| 68 | extra instructions. Using a subtraction has the advantage of |
| 69 | detecting some invalid cases on platforms that detect integer |
| 70 | overflow. |
| 71 | |
| 72 | The (int) cast avoids a gcc -Wconversion warning. */ |
| 73 | |
| 74 | _GL_TIMESPEC_INLINE int |
| 75 | timespec_cmp (struct timespec a, struct timespec b) |
| 76 | { |
| 77 | return (a.tv_sec < b.tv_sec ? -1 |
| 78 | : a.tv_sec > b.tv_sec ? 1 |
| 79 | : (int) (a.tv_nsec - b.tv_nsec)); |
| 80 | } |
| 81 | |
| 82 | /* Return -1, 0, 1, depending on the sign of A. A.tv_nsec must be |
| 83 | nonnegative. */ |
| 84 | _GL_TIMESPEC_INLINE int |
| 85 | timespec_sign (struct timespec a) |
| 86 | { |
| 87 | return a.tv_sec < 0 ? -1 : a.tv_sec || a.tv_nsec; |
| 88 | } |
| 89 | |
| 90 | struct timespec timespec_add (struct timespec, struct timespec) |
| 91 | _GL_ATTRIBUTE_CONST; |
| 92 | struct timespec timespec_sub (struct timespec, struct timespec) |
| 93 | _GL_ATTRIBUTE_CONST; |
| 94 | struct timespec dtotimespec (double) |
| 95 | _GL_ATTRIBUTE_CONST; |
| 96 | |
| 97 | /* Return an approximation to A, of type 'double'. */ |
| 98 | _GL_TIMESPEC_INLINE double |
| 99 | timespectod (struct timespec a) |
| 100 | { |
| 101 | return a.tv_sec + a.tv_nsec / 1e9; |
| 102 | } |
| 103 | |
| 104 | void gettime (struct timespec *); |
| 105 | int settime (struct timespec const *); |
| 106 | |
| 107 | _GL_INLINE_HEADER_END |
| 108 | |
| 109 | #endif |