FFmpeg: libavformat/cutils.c Source File

00001 /*
00002  * various simple utilities for libavformat
00003  * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 #include "avformat.h"
00022 #include "internal.h"
00023 
00024 #define ISLEAP(y) (((y) % 4 == 0) && (((y) % 100) != 0 || ((y) % 400) == 0))
00025 #define LEAPS_COUNT(y) ((y)/4 - (y)/100 + (y)/400)
00026 
00027 /* This is our own gmtime_r. It differs from its POSIX counterpart in a
00028    couple of places, though. */
00029 struct tm *brktimegm(time_t secs, struct tm *tm)
00030 {
00031     int days, y, ny, m;
00032     int md[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
00033 
00034     days = secs / 86400;
00035     secs %= 86400;
00036     tm->tm_hour = secs / 3600;
00037     tm->tm_min = (secs % 3600) / 60;
00038     tm->tm_sec =  secs % 60;
00039 
00040     /* oh well, may be someone some day will invent a formula for this stuff */
00041     y = 1970; /* start "guessing" */
00042     while (days > 365) {
00043         ny = (y + days/366);
00044         days -= (ny - y) * 365 + LEAPS_COUNT(ny - 1) - LEAPS_COUNT(y - 1);
00045         y = ny;
00046     }
00047     if (days==365 && !ISLEAP(y)) { days=0; y++; }
00048     md[1] = ISLEAP(y)?29:28;
00049     for (m=0; days >= md[m]; m++)
00050          days -= md[m];
00051 
00052     tm->tm_year = y;  /* unlike gmtime_r we store complete year here */
00053     tm->tm_mon = m+1; /* unlike gmtime_r tm_mon is from 1 to 12 */
00054     tm->tm_mday = days+1;
00055 
00056     return tm;
00057 }