1 /* $OpenBSD: gmt2local.c,v 1.2 2000/10/03 14:31:55 ho Exp $ */ 2 3 /* 4 * Copyright (c) 1997 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that: (1) source code distributions 9 * retain the above copyright notice and this paragraph in its entirety, (2) 10 * distributions including binary code include the above copyright notice and 11 * this paragraph in its entirety in the documentation or other materials 12 * provided with the distribution, and (3) all advertising materials mentioning 13 * features or use of this software display the following acknowledgement: 14 * ``This product includes software developed by the University of California, 15 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of 16 * the University nor the names of its contributors may be used to endorse 17 * or promote products derived from this software without specific prior 18 * written permission. 19 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED 20 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 21 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 22 */ 23 24 #ifndef lint 25 static const char rcsid[] = 26 "@(#) $Header: /home/cvs/src/usr.sbin/tcpdump/gmt2local.c,v 1.2 2000/10/03 14:31:55 ho Exp $ (LBL)"; 27 #endif 28 29 #include <sys/types.h> 30 #include <sys/time.h> 31 32 #include <stdio.h> 33 #ifdef TIME_WITH_SYS_TIME 34 #include <time.h> 35 #endif 36 37 #include "gnuc.h" 38 #ifdef HAVE_OS_PROTO_H 39 #include "os-proto.h" 40 #endif 41 42 #include "gmt2local.h" 43 44 /* 45 * Returns the difference between gmt and local time in seconds. 46 * Use gmtime() and localtime() to keep things simple. 47 */ 48 int32_t 49 gmt2local(time_t t) 50 { 51 register int dt, dir; 52 register struct tm *gmt, *loc; 53 struct tm sgmt; 54 55 if (t == 0) 56 t = time(NULL); 57 gmt = &sgmt; 58 *gmt = *gmtime(&t); 59 loc = localtime(&t); 60 dt = (loc->tm_hour - gmt->tm_hour) * 60 * 60 + 61 (loc->tm_min - gmt->tm_min) * 60; 62 63 /* 64 * If the year or julian day is different, we span 00:00 GMT 65 * and must add or subtract a day. Check the year first to 66 * avoid problems when the julian day wraps. 67 */ 68 dir = loc->tm_year - gmt->tm_year; 69 if (dir == 0) 70 dir = loc->tm_yday - gmt->tm_yday; 71 dt += dir * 24 * 60 * 60; 72 73 return (dt); 74 } 75