time.c

   1 /*
   2  * Copyright (C) 2005-2013 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 of 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,
  59                 struct timeval *diff)
  60 {
  61         int ret = 1;
  62
  63         if ((b->tv_sec < a->tv_sec) ||
  64                 ((b->tv_sec == a->tv_sec) && (b->tv_usec < a->tv_usec))) {
  65                 const struct timeval *tmp = a;
  66                 a = b;
  67                 b = tmp;
  68                 ret = -1;
  69         }
  70         if (!diff)
  71                 return ret;
  72         diff->tv_sec = b->tv_sec - a->tv_sec;
  73         if (b->tv_usec < a->tv_usec) {
  74                 diff->tv_sec--;
  75                 diff->tv_usec = 1000 * 1000 - a->tv_usec + b->tv_usec;
  76         } else
  77                 diff->tv_usec = b->tv_usec - a->tv_usec;
  78         return ret;
  79 }
  80
  81 /**
  82  * Add two time values.
  83  *
  84  * \param a First addend.
  85  * \param b Second addend.
  86  * \param sum Contains the sum \a a + \a b on return.
  87  */
  88 void tv_add(const struct timeval *a, const struct timeval *b,
  89                 struct timeval *sum)
  90 {
  91         sum->tv_sec = a->tv_sec + b->tv_sec;
  92         if (a->tv_usec + b->tv_usec >= 1000 * 1000) {
  93                 sum->tv_sec++;
  94                 sum->tv_usec = a->tv_usec + b->tv_usec - 1000 * 1000;
  95         } else
  96                 sum->tv_usec = a->tv_usec + b->tv_usec;
  97 }
  98
  99 /**
 100  * Compute integer multiple of given struct timeval.
 101  *
 102  * \param mult The integer value to multiply with.
 103  * \param tv The timevalue to multiply.
 104  *
 105  * \param result Contains \a mult * \a tv on return.
 106  */
 107 void tv_scale(const unsigned long mult, const struct timeval *tv,
 108                 struct timeval *result)
 109 {
 110         uint64_t x = ((uint64_t)tv->tv_sec * 1000 * 1000 + tv->tv_usec) * mult;
 111
 112         result->tv_sec = x / 1000 / 1000;
 113         result->tv_usec = x % (1000 * 1000);
 114 }
 115
 116 /**
 117  * Compute a fraction of given struct timeval.
 118  *
 119  * \param divisor The integer value to divide by.
 120  * \param tv The timevalue to divide.
 121  * \param result Contains (1 / mult) * tv on return.
 122  */
 123 void tv_divide(const unsigned long divisor, const struct timeval *tv,
 124                 struct timeval *result)
 125 {
 126         uint64_t x = ((uint64_t)tv->tv_sec * 1000 * 1000 + tv->tv_usec) / divisor;
 127
 128         result->tv_sec = x / 1000 / 1000;
 129         result->tv_usec = x % (1000 * 1000);
 130 }
 131
 132 /**
 133  * Compute a convex combination of two time values.
 134  *
 135  * \param a The first coefficient.
 136  * \param tv1 The first time value.
 137  * \param b The second coefficient.
 138  * \param tv2 The second time value.
 139  * \param result Contains the convex combination upon return.
 140  *
 141  * Compute x := (a * tv1 + b * tv2) / (|a| + |b|) and store |x| in \a result.
 142  * Both \a a and \a b may be negative.
 143  *
 144  * \return Zero, 1 or -1, if \a x is zero, positive or negative, respectively.
 145  */
 146 int tv_convex_combination(const long a, const struct timeval *tv1,
 147                 const long b, const struct timeval *tv2,
 148                 struct timeval *result)
 149 {
 150         struct timeval tmp1, tmp2, tmp3;
 151         int ret = 1;
 152         unsigned long a1, b1;
 153
 154         if (a == 0 && b == 0) {
 155                 result->tv_sec = 0;
 156                 result->tv_usec = 0;
 157                 return 0;
 158         }
 159         a1 = PARA_ABS(a);
 160         b1 = PARA_ABS(b);
 161         tv_scale(a1, tv1, &tmp1);
 162         tv_scale(b1, tv2, &tmp2);
 163         if ((a > 0 && b < 0) || (a < 0 && b > 0)) /* subtract */
 164                 ret = tv_diff(&tmp1, &tmp2, &tmp3);
 165         else
 166                 tv_add(&tmp1, &tmp2, &tmp3);
 167         tv_divide(a1 + b1, &tmp3, result);
 168         if (!a || !b) {
 169                 if (a + b < 0)
 170                         ret = -1;
 171         } else if (a < 0)
 172                 ret = -ret;
 173         return ret;
 174 }
 175
 176 /**
 177  * Compute when to send a chunk of an audio file.
 178  *
 179  * \param chunk_num The number of the chunk.
 180  * \param chunk_tv The duration of one chunk.
 181  * \param stream_start When the first chunk was sent.
 182  * \param result The time when to send chunk number \a chunk_num.
 183  *
 184  * This function computes \a stream_start + \a chunk_num * \a chunk_time.
 185  */
 186 void compute_chunk_time(long unsigned chunk_num,
 187                 struct timeval *chunk_tv, struct timeval *stream_start,
 188                 struct timeval *result)
 189 {
 190         struct timeval tmp;
 191
 192         tv_scale(chunk_num, chunk_tv, &tmp);
 193         tv_add(&tmp, stream_start, result);
 194 }
 195
 196 /**
 197  * Retrieve the time of the realtime clock.
 198  *
 199  * \param tv Where to store the result.
 200  *
 201  * Gets the current value of the system-wide real-time clock (identified by id
 202  * \p CLOCK_REALTIME). If \a tv is \p NULL, the value is stored in a static
 203  * buffer, otherwise it is stored at the location given by \a tv.
 204  *
 205  * \return This function aborts on errors. On success it returns a pointer to
 206  * memory containing the current time.
 207  *
 208  * \sa clock_gettime(2), gettimeofday(2).
 209  */
 210 struct timeval *clock_get_realtime(struct timeval *tv)
 211 {
 212         static struct timeval user_friendly;
 213
 214         if (!tv)
 215                 tv = &user_friendly;
 216 #ifdef HAVE_CLOCK_GETTIME
 217         {
 218                 struct timespec t;
 219                 int ret;
 220
 221                 ret = clock_gettime(CLOCK_REALTIME, &t);
 222                 assert(ret == 0);
 223                 tv->tv_sec = t.tv_sec;
 224                 tv->tv_usec = t.tv_nsec / 1000;
 225         }
 226 #else
 227         #include <sys/time.h>
 228         gettimeofday(tv, NULL);
 229 #endif /* HAVE_CLOCK_GETTIME */
 230         return tv;
 231 }