lib/roken/timeval.c

   1 /*
   2  * Copyright (c) 1999 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the Institute nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 /*
  35  * Timeval stuff
  36  */
  37
  38 #include <config.h>
  39
  40 #include "roken.h"
  41
  42 ROKEN_LIB_FUNCTION time_t ROKEN_LIB_CALL
  43 rk_time_add(time_t t, time_t delta)
  44 {
  45     if (delta == 0)
  46         return t;
  47
  48 #ifdef TIME_T_SIGNED
  49     /* Signed overflow is UB in C */
  50 #if SIZEOF_TIME_T == 4
  51     if (t >= 0 && delta > 0 && INT32_MAX - t < delta)
  52         /* Time left to hit INT32_MAX is less than what we want to add */
  53         return INT32_MAX;
  54     else if (t < 0 && delta == INT32_MIN)
  55         /* Avoid computing -delta when t == INT32_MIN! */
  56         return INT32_MIN;
  57     else if (t == INT32_MIN && delta < 0)
  58         /* Avoid computing -t when t == INT32_MIN! */
  59         return INT32_MIN;
  60     else if (t < 0 && delta < 0 && INT32_MIN + (-t) < (-delta))
  61         /* Time left to hit INT32_MIN is less than what we want to subtract */
  62         return INT32_MIN;
  63     else
  64         return t + delta;
  65 #elif SIZEOF_TIME_T == 8
  66     if (t >= 0 && delta > 0 && INT64_MAX - t < delta)
  67         return INT64_MAX;
  68     else if (t < 0 && delta == INT64_MIN)
  69         /* Avoid computing -delta when t == INT64_MIN! */
  70         return INT64_MIN;
  71     else if (t == INT64_MIN && delta < 0)
  72         /* Avoid computing -t when t == INT64_MIN! */
  73         return INT64_MIN;
  74     else if (t < 0 && delta < 0 && INT64_MIN + (-t) < (-delta))
  75         return INT64_MIN;
  76     else
  77         return t + delta;
  78 #else
  79 #error "Unexpected sizeof(time_t)"
  80 #endif
  81 #else
  82
  83     /* Unsigned overflow is defined in C */
  84 #if SIZEOF_TIME_T == 4
  85     if (t + delta < t)
  86         return UINT32_MAX;
  87 #elif SIZEOF_TIME_T == 8
  88     if (t + delta < t)
  89         return UINT64_MAX;
  90 #else
  91 #error "Unexpected sizeof(time_t)"
  92 #endif
  93 #endif
  94     return t + delta;
  95 }
  96
  97 ROKEN_LIB_FUNCTION time_t ROKEN_LIB_CALL
  98 rk_time_sub(time_t t, time_t delta)
  99 {
 100     if (delta == 0)
 101         return t;
 102 #ifdef TIME_T_SIGNED
 103     if (delta > 0)
 104         return time_add(t, -delta);
 105 #if SIZEOF_TIME_T == 4
 106     if (delta == INT32_MIN) {
 107         if (t < 0) {
 108             t = t + INT32_MAX;
 109             return t + 1;
 110         }
 111         return INT32_MAX;
 112     }
 113     /* Safe to compute -delta, so use time_add() to add -delta */
 114     return time_add(t, -delta);
 115 #elif SIZEOF_TIME_T == 8
 116     if (delta == INT64_MIN) {
 117         if (t < 0) {
 118             t = t + INT64_MAX;
 119             return t + 1;
 120         }
 121         return INT64_MAX;
 122     }
 123     return time_add(t, -delta);
 124 #else
 125 #error "Unexpected sizeof(time_t)"
 126 #endif
 127 #else
 128     /* Both t and delta are non-negative. */
 129     if (delta > t)
 130         return 0;
 131 #endif
 132     return t - delta;
 133 }
 134
 135 /*
 136  * Make `t1' consistent.
 137  */
 138
 139 ROKEN_LIB_FUNCTION void ROKEN_LIB_CALL
 140 timevalfix(struct timeval *t1)
 141 {
 142     if (t1->tv_usec < 0) {
 143         t1->tv_sec--;
 144         t1->tv_usec += 1000000;
 145     }
 146     if (t1->tv_usec >= 1000000) {
 147         t1->tv_sec++;
 148         t1->tv_usec -= 1000000;
 149     }
 150 }
 151
 152 /*
 153  * t1 += t2
 154  */
 155
 156 ROKEN_LIB_FUNCTION void ROKEN_LIB_CALL
 157 timevaladd(struct timeval *t1, const struct timeval *t2)
 158 {
 159     t1->tv_sec  += t2->tv_sec;
 160     t1->tv_usec += t2->tv_usec;
 161     timevalfix(t1);
 162 }
 163
 164 /*
 165  * t1 -= t2
 166  */
 167
 168 ROKEN_LIB_FUNCTION void ROKEN_LIB_CALL
 169 timevalsub(struct timeval *t1, const struct timeval *t2)
 170 {
 171     t1->tv_sec  -= t2->tv_sec;
 172     t1->tv_usec -= t2->tv_usec;
 173     timevalfix(t1);
 174 }