time.c

   1 #include "para.h"
   2 /** \file time.c helper functions for dealing with timeouts */
   3
   4 /**
   5  * convert struct timeval to milliseconds
   6  *
   7  * \param tv the value to convert
   8  *
   9  * \return The number off milliseconds in \a tv
  10  */
  11 long unsigned tv2ms(const struct timeval *tv)
  12 {
  13         return tv->tv_sec * 1000 + (tv->tv_usec + 500)/ 1000;
  14 }
  15
  16 /**
  17  * convert milliseconds to struct timeval
  18  *
  19  * \param n the number of milliseconds
  20  * \param tv will be filled in by the function
  21  */
  22 void ms2tv(long unsigned n, struct timeval *tv)
  23 {
  24         tv->tv_sec = n / 1000;
  25         tv->tv_usec = (n % 1000) * 1000;
  26 }
  27
  28 /**
  29  * convert double to struct timeval
  30  *
  31  * \param x the value to convert
  32  * \param tv converted value is stored here
  33  */
  34 void d2tv(double x, struct timeval *tv)
  35 {
  36         tv->tv_sec = x;
  37         tv->tv_usec = (x - (double)tv->tv_sec) * 1000.0 * 1000.0 + 0.5;
  38 }
  39
  40 /**
  41  * compute the difference of two time values
  42  *
  43  * \param b minuend
  44  * \param a subtrahend
  45  * \param diff difference is stored here
  46  *
  47  * \return If b > a, compute b - a and return 1. if b < a
  48  * compute a - b and return -1. If \a diff is not  \p NULL, \a diff gets
  49  * filled in with the absolute value |b - a|.
  50  */
  51 int tv_diff(const struct timeval *b, const struct timeval *a, struct timeval *diff)
  52 {
  53         int ret = 1;
  54
  55         if ((b->tv_sec < a->tv_sec) ||
  56                 ((b->tv_sec == a->tv_sec) && (b->tv_usec < a->tv_usec))) {
  57                 const struct timeval *tmp = a;
  58                 a = b;
  59                 b = tmp;
  60                 ret = -1;
  61         }
  62         if (!diff)
  63                 return ret;
  64         diff->tv_sec = b->tv_sec - a->tv_sec;
  65         if (b->tv_usec < a->tv_usec) {
  66                 diff->tv_sec--;
  67                 diff->tv_usec = 1000 * 1000 - a->tv_usec + b->tv_usec;
  68         } else
  69                 diff->tv_usec = b->tv_usec - a->tv_usec;
  70         return ret;
  71 }
  72
  73 /**
  74  * add two structs of type timeval
  75  *
  76  * \param a first addend
  77  * \param b second addend
  78  * \param sum holds the sum upon return
  79  */
  80 void tv_add(const struct timeval *a, const struct timeval *b,
  81         struct timeval *sum)
  82 {
  83         sum->tv_sec = a->tv_sec + b->tv_sec;
  84         if (a->tv_usec + b->tv_usec >= 1000 * 1000) {
  85                 sum->tv_sec++;
  86                 sum->tv_usec = a->tv_usec + b->tv_usec - 1000 * 1000;
  87         } else
  88                 sum->tv_usec = a->tv_usec + b->tv_usec;
  89 }
  90
  91 /**
  92  * compute integer multiple of given struct timeval
  93  *
  94  * \param mult the integer value to multiply with
  95  * \param tv the timevalue to multiply
  96  * \param result holds mult * tv upon return
  97  */
  98 void tv_scale(const unsigned long mult, const struct timeval *tv,
  99         struct timeval *result)
 100 {
 101         result->tv_sec = mult * tv->tv_sec;
 102         result->tv_sec += tv->tv_usec * mult / 1000 / 1000;
 103         result->tv_usec = tv->tv_usec * mult % (1000 * 1000);
 104 }
 105
 106 /**
 107  * compute fraction of given struct timeval
 108  *
 109  * \param divisor the integer value to divide by
 110  * \param tv the timevalue to divide
 111  * \param result holds (1 / mult) * tv upon return
 112  */
 113 void tv_divide(const unsigned long divisor, const struct timeval *tv,
 114         struct timeval *result)
 115 {
 116         long unsigned q;
 117
 118         if (!divisor) {
 119                 PARA_EMERG_LOG("%s\n", "division by zero");
 120                 exit(EXIT_FAILURE);
 121         }
 122         q = tv->tv_usec / divisor;
 123         result->tv_sec = tv->tv_sec / divisor;
 124         result->tv_usec = (tv->tv_sec - result->tv_sec * divisor)
 125                 * 1000 * 1000 / divisor;
 126         if (result->tv_usec + q >= 1000 * 1000) {
 127                 result->tv_sec++;
 128                 result->tv_usec = 1000 * 1000 - result->tv_usec - q;
 129         } else
 130                 result->tv_usec += q;
 131 }
 132
 133 /**
 134  * compute a convex combination of two time values
 135  *
 136  * \param a the first coefiicent
 137  * \param tv1 the first time value
 138  * \param b the second coefiicent
 139  * \param tv2 the second time value
 140  * \param result holds the convex combination upon return
 141  *
 142  * compute x := (a * tv1 + b * tv2) / (|a| + |b|). a, b may be negative.
 143  * returns sign(x) and stores |x| in the result pointer.
 144  */
 145 int tv_convex_combination(const long a, const struct timeval *tv1,
 146                 const long b, const struct timeval *tv2,
 147                 struct timeval *result)
 148 {
 149         struct timeval tmp1, tmp2, tmp3;
 150         int ret = 1, subtract = ((a > 0 && b < 0) || (a < 0 && b > 0));
 151         unsigned long a1 = PARA_ABS(a), b1 = PARA_ABS(b);
 152
 153         tv_scale(a1, tv1, &tmp1);
 154         tv_scale(b1, tv2, &tmp2);
 155         if (subtract)
 156                 ret = tv_diff(&tmp1, &tmp2, &tmp3);
 157         else
 158                 tv_add(&tmp1, &tmp2, &tmp3);
 159         if (a1 + b1)
 160                 tv_divide(a1 + b1, &tmp3, result);
 161         else {
 162                 result->tv_sec = 0;
 163                 result->tv_usec = 0;
 164         }
 165         if (!a || !b) {
 166                 if (a + b < 0)
 167                         ret = -1;
 168         } else
 169                 if (a < 0)
 170                         ret = -ret;
 171         return ret;
 172 }