/* * (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. */ /* $Id$ */ /* 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; }