time.c

   1 /* Copyright (C) 2005 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
   2
   3 #include "para.h"
   4 /** \file time.c Helper functions for dealing with time values. */
   5
   6 /**
   7  * Convert struct timeval to milliseconds.
   8  *
   9  * \param tv The time value value to convert.
  10  *
  11  * \return The number of milliseconds in \a tv.
  12  */
  13 long unsigned tv2ms(const struct timeval *tv)
  14 {
  15         return tv->tv_sec * 1000 + (tv->tv_usec + 500)/ 1000;
  16 }
  17
  18 /**
  19  * Convert milliseconds to a struct timeval.
  20  *
  21  * \param n The number of milliseconds.
  22  * \param tv Result pointer.
  23  */
  24 void ms2tv(long unsigned n, struct timeval *tv)
  25 {
  26         tv->tv_sec = n / 1000;
  27         tv->tv_usec = (n % 1000) * 1000;
  28 }
  29
  30 /**
  31  * Compute the difference of two time values.
  32  *
  33  * \param b Minuend.
  34  * \param a Subtrahend.
  35  * \param diff Result pointer.
  36  *
  37  * If \a diff is not \p NULL, it contains the absolute value |\a b - \a a| on
  38  * return.
  39  *
  40  * \return If \a b < \a a, this function returns -1, otherwise it returns 1.
  41  */
  42 int tv_diff(const struct timeval *b, const struct timeval *a,
  43                 struct timeval *diff)
  44 {
  45         int ret = 1;
  46
  47         if ((b->tv_sec < a->tv_sec) ||
  48                 ((b->tv_sec == a->tv_sec) && (b->tv_usec < a->tv_usec))) {
  49                 const struct timeval *tmp = a;
  50                 a = b;
  51                 b = tmp;
  52                 ret = -1;
  53         }
  54         if (!diff)
  55                 return ret;
  56         diff->tv_sec = b->tv_sec - a->tv_sec;
  57         if (b->tv_usec < a->tv_usec) {
  58                 diff->tv_sec--;
  59                 diff->tv_usec = 1000 * 1000 - a->tv_usec + b->tv_usec;
  60         } else
  61                 diff->tv_usec = b->tv_usec - a->tv_usec;
  62         return ret;
  63 }
  64
  65 /**
  66  * Add two time values.
  67  *
  68  * \param a First addend.
  69  * \param b Second addend.
  70  * \param sum Contains the sum \a a + \a b on return.
  71  */
  72 void tv_add(const struct timeval *a, const struct timeval *b,
  73                 struct timeval *sum)
  74 {
  75         sum->tv_sec = a->tv_sec + b->tv_sec;
  76         if (a->tv_usec + b->tv_usec >= 1000 * 1000) {
  77                 sum->tv_sec++;
  78                 sum->tv_usec = a->tv_usec + b->tv_usec - 1000 * 1000;
  79         } else
  80                 sum->tv_usec = a->tv_usec + b->tv_usec;
  81 }
  82
  83 /**
  84  * Compute integer multiple of given struct timeval.
  85  *
  86  * \param mult The integer value to multiply with.
  87  * \param tv The timevalue to multiply.
  88  *
  89  * \param result Contains \a mult * \a tv on return.
  90  */
  91 void tv_scale(const unsigned long mult, const struct timeval *tv,
  92                 struct timeval *result)
  93 {
  94         uint64_t x = ((uint64_t)tv->tv_sec * 1000 * 1000 + tv->tv_usec) * mult;
  95
  96         result->tv_sec = x / 1000 / 1000;
  97         result->tv_usec = x % (1000 * 1000);
  98 }
  99
 100 /**
 101  * Compute a fraction of given struct timeval.
 102  *
 103  * \param divisor The integer value to divide by.
 104  * \param tv The timevalue to divide.
 105  * \param result Contains (1 / mult) * tv on return.
 106  */
 107 void tv_divide(const unsigned long divisor, const struct timeval *tv,
 108                 struct timeval *result)
 109 {
 110         uint64_t x = ((uint64_t)tv->tv_sec * 1000 * 1000 + tv->tv_usec) / divisor;
 111
 112         result->tv_sec = x / 1000 / 1000;
 113         result->tv_usec = x % (1000 * 1000);
 114 }
 115
 116 /**
 117  * Compute a convex combination of two time values.
 118  *
 119  * \param a The first coefficient.
 120  * \param tv1 The first time value.
 121  * \param b The second coefficient.
 122  * \param tv2 The second time value.
 123  * \param result Contains the convex combination upon return.
 124  *
 125  * Compute x := (a * tv1 + b * tv2) / (|a| + |b|) and store |x| in \a result.
 126  * Both \a a and \a b may be negative.
 127  *
 128  * \return Zero, 1 or -1, if \a x is zero, positive or negative, respectively.
 129  */
 130 int tv_convex_combination(const long a, const struct timeval *tv1,
 131                 const long b, const struct timeval *tv2,
 132                 struct timeval *result)
 133 {
 134         struct timeval tmp1, tmp2, tmp3;
 135         int ret = 1;
 136         unsigned long a1, b1;
 137
 138         if (a == 0 && b == 0) {
 139                 result->tv_sec = 0;
 140                 result->tv_usec = 0;
 141                 return 0;
 142         }
 143         a1 = PARA_ABS(a);
 144         b1 = PARA_ABS(b);
 145         tv_scale(a1, tv1, &tmp1);
 146         tv_scale(b1, tv2, &tmp2);
 147         if ((a > 0 && b < 0) || (a < 0 && b > 0)) /* subtract */
 148                 ret = tv_diff(&tmp1, &tmp2, &tmp3);
 149         else
 150                 tv_add(&tmp1, &tmp2, &tmp3);
 151         tv_divide(a1 + b1, &tmp3, result);
 152         if (!a || !b) {
 153                 if (a + b < 0)
 154                         ret = -1;
 155         } else if (a < 0)
 156                 ret = -ret;
 157         return ret;
 158 }
 159
 160 /**
 161  * Compute when to send a chunk of an audio file.
 162  *
 163  * \param chunk_num The number of the chunk.
 164  * \param chunk_tv The duration of one chunk.
 165  * \param stream_start When the first chunk was sent.
 166  * \param result The time when to send chunk number \a chunk_num.
 167  *
 168  * This function computes \a stream_start + \a chunk_num * \a chunk_time.
 169  */
 170 void compute_chunk_time(long unsigned chunk_num,
 171                 struct timeval *chunk_tv, struct timeval *stream_start,
 172                 struct timeval *result)
 173 {
 174         struct timeval tmp;
 175
 176         tv_scale(chunk_num, chunk_tv, &tmp);
 177         tv_add(&tmp, stream_start, result);
 178 }
 179
 180 /**
 181  * Retrieve the time of the realtime clock.
 182  *
 183  * \param tv Where to store the result.
 184  *
 185  * Gets the current value of the system-wide real-time clock (identified by id
 186  * \p CLOCK_REALTIME). If \a tv is \p NULL, the value is stored in a static
 187  * buffer, otherwise it is stored at the location given by \a tv.
 188  *
 189  * \return This function aborts on errors. On success it returns a pointer to
 190  * memory containing the current time.
 191  *
 192  * \sa clock_gettime(2), gettimeofday(2).
 193  */
 194 struct timeval *clock_get_realtime(struct timeval *tv)
 195 {
 196         static struct timeval user_friendly;
 197         struct timespec t;
 198         int ret;
 199
 200         if (!tv)
 201                 tv = &user_friendly;
 202         ret = clock_gettime(CLOCK_REALTIME, &t);
 203         assert(ret == 0);
 204         tv->tv_sec = t.tv_sec;
 205         tv->tv_usec = t.tv_nsec / 1000;
 206         return tv;
 207 }