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/* $OpenBSD: gmt2local.c,v 1.4 2013/08/09 17:52:12 bluhm Exp $ */ |
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/* |
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* Copyright (c) 1997 |
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* The Regents of the University of California. All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that: (1) source code distributions |
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* retain the above copyright notice and this paragraph in its entirety, (2) |
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* distributions including binary code include the above copyright notice and |
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* this paragraph in its entirety in the documentation or other materials |
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* provided with the distribution, and (3) all advertising materials mentioning |
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* features or use of this software display the following acknowledgement: |
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* ``This product includes software developed by the University of California, |
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* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of |
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* the University nor the names of its contributors may be used to endorse |
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* or promote products derived from this software without specific prior |
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* written permission. |
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED |
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* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF |
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. |
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*/ |
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#include <sys/types.h> |
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#include <sys/time.h> |
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#include <stdio.h> |
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#include <time.h> |
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#include "gmt2local.h" |
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/* |
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* Returns the difference between gmt and local time in seconds. |
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* Use gmtime() and localtime() to keep things simple. |
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*/ |
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int32_t |
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gmt2local(time_t t) |
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{ |
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register int dt, dir; |
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register struct tm *gmt, *loc; |
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struct tm sgmt; |
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if (t == 0) |
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t = time(NULL); |
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gmt = &sgmt; |
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*gmt = *gmtime(&t); |
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loc = localtime(&t); |
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dt = (loc->tm_hour - gmt->tm_hour) * 60 * 60 + |
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(loc->tm_min - gmt->tm_min) * 60; |
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/* |
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* If the year or julian day is different, we span 00:00 GMT |
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* and must add or subtract a day. Check the year first to |
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* avoid problems when the julian day wraps. |
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*/ |
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dir = loc->tm_year - gmt->tm_year; |
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if (dir == 0) |
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dir = loc->tm_yday - gmt->tm_yday; |
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dt += dir * 24 * 60 * 60; |
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return (dt); |
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} |