1 /*
2 * Copyright (C) 2005-2007 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
7 #include "para.h"
8 /** \file time.c Helper functions for dealing with time values. */
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 }
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 }
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 }
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;
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 }
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 }
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 }
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;
126 result->tv_sec = x / 1000 / 1000;
127 result->tv_usec = x % (1000 * 1000);
128 }
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);
152 tv_scale(a1, tv1, &tmp1);
153 tv_scale(b1, tv2, &tmp2);
154 if (subtract)
155 ret = tv_diff(&tmp1, &tmp2, &tmp3);
156 else
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 }