time.c

   1 /*
   2  * Copyright (C) 2005-2008 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 #include "para.h"
   8 /** \file time.c Helper functions for dealing with time values. */
   9
  10 /**
  11  * Convert struct timeval to milliseconds.
  12  *
  13  * \param tv The time value value to convert.
  14  *
  15  * \return The number off milliseconds in \a tv.
  16  */
  17 long unsigned tv2ms(const struct timeval *tv)
  18 {
  19         return tv->tv_sec * 1000 + (tv->tv_usec + 500)/ 1000;
  20 }
  21
  22 /**
  23  * Convert milliseconds to a struct timeval.
  24  *
  25  * \param n The number of milliseconds.
  26  * \param tv Result pointer.
  27  */
  28 void ms2tv(long unsigned n, struct timeval *tv)
  29 {
  30         tv->tv_sec = n / 1000;
  31         tv->tv_usec = (n % 1000) * 1000;
  32 }
  33
  34 /**
  35  * Convert a double to a struct timeval.
  36  *
  37  * \param x The value to convert.
  38  * \param tv Result pointer.
  39  */
  40 void d2tv(double x, struct timeval *tv)
  41 {
  42         tv->tv_sec = x;
  43         tv->tv_usec = (x - (double)tv->tv_sec) * 1000.0 * 1000.0 + 0.5;
  44 }
  45
  46 /**
  47  * Compute the difference of two time values.
  48  *
  49  * \param b Minuend.
  50  * \param a Subtrahend.
  51  * \param diff Result pointer.
  52  *
  53  * If \a diff is not \p NULL, it contains the absolute value |\a b - \a a| on
  54  * return.
  55  *
  56  * \return If \a b < \a a, this function returns -1, otherwise it returns 1.
  57  */
  58 int tv_diff(const struct timeval *b, const struct timeval *a, struct timeval *diff)
  59 {
  60         int ret = 1;
  61
  62         if ((b->tv_sec < a->tv_sec) ||
  63                 ((b->tv_sec == a->tv_sec) && (b->tv_usec < a->tv_usec))) {
  64                 const struct timeval *tmp = a;
  65                 a = b;
  66                 b = tmp;
  67                 ret = -1;
  68         }
  69         if (!diff)
  70                 return ret;
  71         diff->tv_sec = b->tv_sec - a->tv_sec;
  72         if (b->tv_usec < a->tv_usec) {
  73                 diff->tv_sec--;
  74                 diff->tv_usec = 1000 * 1000 - a->tv_usec + b->tv_usec;
  75         } else
  76                 diff->tv_usec = b->tv_usec - a->tv_usec;
  77         return ret;
  78 }
  79
  80 /**
  81  * Add two time values.
  82  *
  83  * \param a First addend.
  84  * \param b Second addend.
  85  * \param sum Contains the sum \a + \a b on return.
  86  */
  87 void tv_add(const struct timeval *a, const struct timeval *b,
  88         struct timeval *sum)
  89 {
  90         sum->tv_sec = a->tv_sec + b->tv_sec;
  91         if (a->tv_usec + b->tv_usec >= 1000 * 1000) {
  92                 sum->tv_sec++;
  93                 sum->tv_usec = a->tv_usec + b->tv_usec - 1000 * 1000;
  94         } else
  95                 sum->tv_usec = a->tv_usec + b->tv_usec;
  96 }
  97
  98 /**
  99  * Compute integer multiple of given struct timeval.
 100  *
 101  * \param mult The integer value to multiply with.
 102  * \param tv The timevalue to multiply.
 103  *
 104  * \param result Contains \a mult * \a tv on return.
 105  */
 106 void tv_scale(const unsigned long mult, const struct timeval *tv,
 107         struct timeval *result)
 108 {
 109         result->tv_sec = mult * tv->tv_sec;
 110         result->tv_sec += tv->tv_usec * mult / 1000 / 1000;
 111         result->tv_usec = tv->tv_usec * mult % (1000 * 1000);
 112 }
 113
 114 /**
 115  * Compute a fraction of given struct timeval.
 116  *
 117  * \param divisor The integer value to divide by.
 118  * \param tv The timevalue to divide.
 119  * \param result Contains (1 / mult) * tv on return.
 120  */
 121 void tv_divide(const unsigned long divisor, const struct timeval *tv,
 122         struct timeval *result)
 123 {
 124         uint64_t x = ((uint64_t)tv->tv_sec * 1000 * 1000 + tv->tv_usec) / divisor;
 125
 126         result->tv_sec = x / 1000 / 1000;
 127         result->tv_usec = x % (1000 * 1000);
 128 }
 129
 130 /**
 131  * Compute a convex combination of two time values.
 132  *
 133  * \param a The first coefiicent.
 134  * \param tv1 The first time value.
 135  * \param b The second coefiicent.
 136  * \param tv2 The second time value.
 137  * \param result Contains the convex combination upon return.
 138  *
 139  * compute x := (a * tv1 + b * tv2) / (|a| + |b|) and store |x| in \a result.
 140  * Both \a a and \a b may be negative.
 141  *
 142  * \return One if \a x is positive, -1 otherwise.
 143  */
 144 int tv_convex_combination(const long a, const struct timeval *tv1,
 145                 const long b, const struct timeval *tv2,
 146                 struct timeval *result)
 147 {
 148         struct timeval tmp1, tmp2, tmp3;
 149         int ret = 1, subtract = ((a > 0 && b < 0) || (a < 0 && b > 0));
 150         unsigned long a1 = PARA_ABS(a), b1 = PARA_ABS(b);
 151
 152         tv_scale(a1, tv1, &tmp1);
 153         tv_scale(b1, tv2, &tmp2);
 154         if (subtract)
 155                 ret = tv_diff(&tmp1, &tmp2, &tmp3);
 156         else
 157                 tv_add(&tmp1, &tmp2, &tmp3);
 158         if (a1 + b1)
 159                 tv_divide(a1 + b1, &tmp3, result);
 160         else {
 161                 result->tv_sec = 0;
 162                 result->tv_usec = 0;
 163         }
 164         if (!a || !b) {
 165                 if (a + b < 0)
 166                         ret = -1;
 167         } else
 168                 if (a < 0)
 169                         ret = -ret;
 170         return ret;
 171 }
 172
 173 /**
 174  * Compute when to send a chunk of an audio file.
 175  *
 176  * \param chunk_num The number of the chunk.
 177  * \param chunk_tv The duration of one chunk.
 178  * \param stream_start When the first chunk was sent.
 179  * \param result The time when to send chunk number \a chunk_num.
 180  *
 181  * This function computes stream_start + chunk_num * chunk_time.
 182  */
 183 void compute_chunk_time(long unsigned chunk_num,
 184                 struct timeval *chunk_tv, struct timeval *stream_start,
 185                 struct timeval *result)
 186 {
 187         struct timeval tmp;
 188
 189         tv_scale(chunk_num, chunk_tv, &tmp);
 190         tv_add(&tmp, stream_start, result);
 191 }