/* xnanosleep.c -- a more convenient interface to nanosleep Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ /* Mostly written (for sleep.c) by Paul Eggert. Factored out (creating this file) by Jim Meyering. */ #if HAVE_CONFIG_H # include #endif #include "xnanosleep.h" #include #include #include #include #include #include #include /* The extra casts work around common compiler bugs. */ #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) /* The outer cast is needed to work around a bug in Cray C 5.0.3.0. It is necessary at least when t == time_t. */ #define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \ ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0)) #define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t))) #ifndef TIME_T_MAX # define TIME_T_MAX TYPE_MAXIMUM (time_t) #endif #include "timespec.h" #include "xalloc.h" /* Subtract the `struct timespec' values X and Y by computing X - Y. If the difference is negative or zero, return false. Otherwise, return true and store the difference in DIFF. X and Y must have valid ts_nsec values, in the range 0 to 999999999. If the difference would overflow, store the maximum possible difference. */ static bool timespec_subtract (struct timespec *diff, struct timespec const *x, struct timespec const *y) { time_t sec = x->tv_sec - y->tv_sec; long int nsec = x->tv_nsec - y->tv_nsec; if (x->tv_sec < y->tv_sec) return false; if (sec < 0) { /* The difference has overflowed. */ sec = TIME_T_MAX; nsec = 999999999; } else if (sec == 0 && nsec <= 0) return false; if (nsec < 0) { sec--; nsec += 1000000000; } diff->tv_sec = sec; diff->tv_nsec = nsec; return true; } /* Sleep until the time (call it WAKE_UP_TIME) specified as SECONDS seconds after the time this function is called. SECONDS must be non-negative. If SECONDS is so large that it is not representable as a `struct timespec', then use the maximum value for that interval. Return -1 on failure (setting errno), 0 on success. */ int xnanosleep (double seconds) { bool overflow; double ns; struct timespec ts_start; struct timespec ts_sleep; struct timespec ts_stop; assert (0 <= seconds); if (gettime (&ts_start) != 0) return -1; /* Separate whole seconds from nanoseconds. Be careful to detect any overflow. */ ts_sleep.tv_sec = seconds; ns = 1e9 * (seconds - ts_sleep.tv_sec); overflow = ! (ts_sleep.tv_sec <= seconds && 0 <= ns && ns <= 1e9); ts_sleep.tv_nsec = ns; /* Round up to the next whole number, if necessary, so that we always sleep for at least the requested amount of time. Assuming the default rounding mode, we don't have to worry about the rounding error when computing 'ns' above, since the error won't cause 'ns' to drop below an integer boundary. */ ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns); /* Normalize the interval length. nanosleep requires this. */ if (1000000000 <= ts_sleep.tv_nsec) { time_t t = ts_sleep.tv_sec + 1; /* Detect integer overflow. */ overflow |= (t < ts_sleep.tv_sec); ts_sleep.tv_sec = t; ts_sleep.tv_nsec -= 1000000000; } /* Compute the time until which we should sleep. */ ts_stop.tv_sec = ts_start.tv_sec + ts_sleep.tv_sec; ts_stop.tv_nsec = ts_start.tv_nsec + ts_sleep.tv_nsec; if (1000000000 <= ts_stop.tv_nsec) { ++ts_stop.tv_sec; ts_stop.tv_nsec -= 1000000000; } /* Detect integer overflow. */ overflow |= (ts_stop.tv_sec < ts_start.tv_sec || (ts_stop.tv_sec == ts_start.tv_sec && ts_stop.tv_nsec < ts_start.tv_nsec)); if (overflow) { /* Fix ts_sleep and ts_stop, which may be garbage due to overflow. */ ts_sleep.tv_sec = ts_stop.tv_sec = TIME_T_MAX; ts_sleep.tv_nsec = ts_stop.tv_nsec = 999999999; } while (nanosleep (&ts_sleep, NULL) != 0) { if (errno != EINTR || gettime (&ts_start) != 0) return -1; /* POSIX.1-2001 requires that when a process is suspended, then resumed, nanosleep (A, B) returns -1, sets errno to EINTR, and sets *B to the time remaining at the point of resumption. However, some versions of the Linux kernel incorrectly return the time remaining at the point of suspension. Work around this bug by computing the remaining time here, rather than by relying on nanosleep's computation. */ if (! timespec_subtract (&ts_sleep, &ts_stop, &ts_start)) break; } return 0; }