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cutils.c
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1 /*
2  * various simple utilities for libavformat
3  * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 #include "avformat.h"
22 #include "internal.h"
23 
24 #define ISLEAP(y) (((y) % 4 == 0) && (((y) % 100) != 0 || ((y) % 400) == 0))
25 #define LEAPS_COUNT(y) ((y)/4 - (y)/100 + (y)/400)
26 
27 /* This is our own gmtime_r. It differs from its POSIX counterpart in a
28  couple of places, though. */
29 struct tm *ff_brktimegm(time_t secs, struct tm *tm)
30 {
31  int days, y, ny, m;
32  int md[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
33 
34  days = secs / 86400;
35  secs %= 86400;
36  tm->tm_hour = secs / 3600;
37  tm->tm_min = (secs % 3600) / 60;
38  tm->tm_sec = secs % 60;
39 
40  /* oh well, may be someone some day will invent a formula for this stuff */
41  y = 1970; /* start "guessing" */
42  while (days > 365) {
43  ny = (y + days/366);
44  days -= (ny - y) * 365 + LEAPS_COUNT(ny - 1) - LEAPS_COUNT(y - 1);
45  y = ny;
46  }
47  if (days==365 && !ISLEAP(y)) { days=0; y++; }
48  md[1] = ISLEAP(y)?29:28;
49  for (m=0; days >= md[m]; m++)
50  days -= md[m];
51 
52  tm->tm_year = y; /* unlike gmtime_r we store complete year here */
53  tm->tm_mon = m+1; /* unlike gmtime_r tm_mon is from 1 to 12 */
54  tm->tm_mday = days+1;
55 
56  return tm;
57 }