lwp/fasttime.c

   1 /*
   2 ****************************************************************************
   3 *        Copyright IBM Corporation 1988, 1989 - All Rights Reserved        *
   4 *                                                                          *
   5 * Permission to use, copy, modify, and distribute this software and its    *
   6 * documentation for any purpose and without fee is hereby granted,         *
   7 * provided that the above copyright notice appear in all copies and        *
   8 * that both that copyright notice and this permission notice appear in     *
   9 * supporting documentation, and that the name of IBM not be used in        *
  10 * advertising or publicity pertaining to distribution of the software      *
  11 * without specific, written prior permission.                              *
  12 *                                                                          *
  13 * IBM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL *
  14 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL IBM *
  15 * BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY      *
  16 * DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER  *
  17 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING   *
  18 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.    *
  19 ****************************************************************************
  20 */
  21 /*
  22  * fasttime.c -- Get the time of day quickly by mapping the kernel's
  23  *               time of day variable.
  24  *
  25  * David Nichols
  26  *  6 January 1986
  27  *
  28  * Modification History
  29  * 3/21/86:  Added FT_ApproxTime which returns the last time
  30  *           in seconds returned by RT_FastTime.  The intent is to give
  31  *           routines which aren't too concerned about the exact time
  32  *           fast access to the time, even on kernels without mmap.
  33  *           - Bob Sidebotham.
  34  * 4/2/86:   Fixed my previous mod and fixed FT_Init so it doesn't initialize
  35  *           a second time if explicitly called after being implicitly called.
  36  *           This saves a (precious) file descriptor.
  37  */
  38
  39 #ifdef HAVE_CONFIG_H
  40 #include <config.h>
  41 RCSID("$Id$");
  42 #endif
  43
  44 #include <stdio.h>
  45 #include <sys/types.h>
  46 #include <sys/time.h>
  47 #include <sys/file.h>
  48 #ifdef HAVE_SYS_MMAN_H
  49 #include <sys/mman.h>
  50 #endif
  51
  52 #ifdef HAVE_NLIST_H
  53 #include <nlist.h>
  54 #else
  55 #ifdef HAVE_LIBELF_NLIST_H
  56 #include <libelf/nlist.h>
  57 #endif
  58 #endif
  59
  60 #include "timer.h"
  61
  62 #define TRUE    1
  63 #define FALSE   0
  64
  65 static enum InitState {
  66     notTried, tried, done
  67 } initState = notTried;
  68
  69 /* last time returned by RT_FastTime. Used to implement FT_ApproxTime */
  70 struct timeval FT_LastTime;
  71
  72
  73 /*
  74  * Call this to get the memory mapped.  It will return -1 if anything went
  75  * wrong.  In that case, calls to FT_GetTimeOfDay will call gettimeofday
  76  * instead.  If printErrors is true, errors in initialization will cause
  77  * error messages to be printed on stderr.  If notReally is true, then
  78  * things are set up so that all calls to FT_GetTimeOfDay call gettimeofday.
  79  * You might want this if your program won't run too long and the nlist
  80  * call is too expensive.  Yeah, it's pretty horrible.
  81  */
  82 int
  83 FT_Init(int printErrors, int notReally)
  84 {
  85
  86     /*
  87      * This is in case explicit initialization occurs after automatic
  88      * initialization
  89      */
  90     if (initState != notTried && !notReally)
  91         return (initState == done ? 0 : -1);
  92
  93     initState = tried;
  94     if (notReally)
  95         return 0;                      /* fake success, but leave initState
  96                                         * wrong. */
  97     return (-1);
  98 }
  99
 100 /*
 101  * Call this to get the time of day.  It will automatically initialize the
 102  * first time you call it.  If you want error messages when you initialize,
 103  * call FT_Init yourself.  If the initialization failed, this will just
 104  * call gettimeofday.  If you ask for the timezone info, this routine will
 105  * punt to gettimeofday.
 106  */
 107 int
 108 FT_GetTimeOfDay(struct timeval * tv, struct timezone * tz)
 109 {
 110     int ret;
 111
 112     ret = gettimeofday(tv, tz);
 113     if (!ret) {
 114
 115         /*
 116          * need to bounds check 'cause Unix can fail these checks, (esp on
 117          * Suns) and time package can generate invalid (to select syscall)
 118          * values for the time until the next interesting event if it
 119          * encounters out of range microsecond fields
 120          */
 121         if (tv->tv_usec < 0)
 122             tv->tv_usec = 0;
 123         if (tv->tv_usec > 999999)
 124             tv->tv_usec = 999999;
 125         FT_LastTime.tv_sec = tv->tv_sec;
 126         FT_LastTime.tv_usec = tv->tv_usec;
 127     }
 128     return ret;
 129 }
 130
 131
 132 /* For compatibility.  Should go away. */
 133 int
 134 TM_GetTimeOfDay(struct timeval * tv, struct timezone * tz)
 135 {
 136     return FT_GetTimeOfDay(tv, tz);
 137 }
 138
 139 int
 140 FT_AGetTimeOfDay(struct timeval * tv, struct timezone * tz)
 141 {
 142     if (FT_LastTime.tv_sec) {
 143         tv->tv_sec = FT_LastTime.tv_sec;
 144         tv->tv_usec = FT_LastTime.tv_usec;
 145         return 0;
 146     }
 147     return FT_GetTimeOfDay(tv, tz);
 148 }
 149
 150 unsigned int
 151 FT_ApproxTime(void)
 152 {
 153     if (!FT_LastTime.tv_sec) {
 154         FT_GetTimeOfDay(&FT_LastTime, 0);
 155     }
 156     return FT_LastTime.tv_sec;
 157 }
 158
 159
 160