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deb-goldedplus/goldlib/gall/gtimjuld.cpp
2000-02-25 10:15:17 +00:00

75 lines
2.7 KiB
C++

// This may look like C code, but it is really -*- C++ -*-
// ------------------------------------------------------------------
// The Goldware Library
// Copyright (C) 1990-1999 Odinn Sorensen
// Copyright (C) 1999-2000 Alexander S. Aganichev
// ------------------------------------------------------------------
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public
// License along with this program; if not, write to the Free
// Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
// MA 02111-1307, USA
// ------------------------------------------------------------------
// $Id$
// ------------------------------------------------------------------
// Julian date conversion functions.
// ------------------------------------------------------------------
#include <gtimall.h>
// ------------------------------------------------------------------
inline int isleap(unsigned yr) { return yr % 400 == 0 || (yr % 4 == 0 && yr % 100 != 0); }
inline unsigned months_to_days(unsigned month) { return (month * 3057 - 3007) / 100; }
inline long years_to_days(unsigned yr) { return yr * 365L + yr / 4 - yr / 100 + yr / 400; }
// ------------------------------------------------------------------
long YMD2JDN(unsigned yr, unsigned mo, unsigned day) {
long scalar;
scalar = day + months_to_days(mo);
if(mo > 2) /* adjust if past February */
scalar -= isleap(yr) ? 1 : 2;
yr--;
scalar += years_to_days(yr);
return scalar - 693595L;
}
// ------------------------------------------------------------------
void JDN2YMD(long scalar, unsigned *yr, unsigned *mo, unsigned *day) {
scalar += 693595L;
unsigned n; /* compute inverse of years_to_days() */
for(n = (unsigned)((scalar * 400L) / 146097L); years_to_days(n) < scalar;)
n++; /* 146097 == years_to_days(400) */
*yr = n;
n = (unsigned)(scalar - years_to_days(n-1));
if(n > 59) { /* adjust if past February */
n += 2;
if(isleap(*yr))
n -= n > 62 ? 1 : 2;
}
*mo = (n * 100 + 3007) / 3057; /* inverse of months_to_days() */
*day = n - months_to_days(*mo);
}
// ------------------------------------------------------------------