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/*
* (C)2012 Michael Duane Rice All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer. Redistributions in binary
* form must reproduce the above copyright notice, this list of conditions
* and the following disclaimer in the documentation and/or other materials
* provided with the distribution. Neither the name of the copyright holders
* nor the names of contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/* $Id: gm_sidereal.c 2369 2013-04-28 14:19:35Z swfltek $ */
/*
Greenwich Mean Sidereal Time. A sidereal second is somewhat shorter than a standard second,
about 1.002737909350795 sidereal seconds per standard second.
We resort to fixed point math due to the insufficient resolution of a 'double', using...
timestamp * ( 1.002737909350795 << 31 )
--------------------------------------- + Te
1 << 31
Where Te is the sidereal time at the epoch.
*/
#include <time.h>
#include <stdint.h>
unsigned long
gm_sidereal(const time_t * timer)
{
uint64_t tmp;
tmp = *timer;
tmp *= 0x8059B740;
tmp /= 0x80000000;
tmp += (uint64_t) 23991;
tmp %= ONE_DAY;
return tmp;
}
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