142 lines
3.5 KiB
C
142 lines
3.5 KiB
C
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/*++
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/* NAME
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/* mail_date 3
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/* SUMMARY
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/* return formatted time
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/* SYNOPSIS
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/* #include <mail_date.h>
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/*
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/* const char *mail_date(when)
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/* time_t when;
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/* DESCRIPTION
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/* mail_date() converts the time specified in \fIwhen\fR to the
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/* form: "Mon, 9 Dec 1996 05:38:26 -0500 (EST)" and returns
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/* a pointer to the result. The result is overwritten upon
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/* each call.
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/* DIAGNOSTICS
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/* Panic: the offset from UTC is more than a whole day. Fatal
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/* error: out of memory.
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/* LICENSE
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/* .ad
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/* .fi
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/* The Secure Mailer license must be distributed with this software.
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/* AUTHOR(S)
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/* Wietse Venema
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/* IBM T.J. Watson Research
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/* P.O. Box 704
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/* Yorktown Heights, NY 10598, USA
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/*--*/
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/* System library. */
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#include <sys_defs.h>
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#include <time.h>
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#include <stdlib.h>
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/* Utility library. */
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#include <msg.h>
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#include <vstring.h>
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/* Global library. */
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#include "mail_date.h"
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/*
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* Application-specific.
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*/
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#define DAY_MIN (24 * HOUR_MIN) /* minutes in a day */
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#define HOUR_MIN 60 /* minutes in an hour */
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#define MIN_SEC 60 /* seconds in a minute */
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/* mail_date - return formatted time */
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const char *mail_date(time_t when)
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{
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static VSTRING *vp;
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struct tm *lt;
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struct tm gmt;
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int gmtoff;
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/*
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* As if strftime() isn't expensive enough, we're dynamically adjusting
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* the size for the result, so we won't be surprised by long names etc.
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*/
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if (vp == 0)
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vp = vstring_alloc(100);
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else
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VSTRING_RESET(vp);
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/*
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* POSIX does not require that struct tm has a tm_gmtoff field, so we
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* must compute the time offset from UTC by hand.
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*
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* Starting with the difference in hours/minutes between 24-hour clocks,
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* adjust for differences in years, in yeardays, and in (leap) seconds.
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*
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* Assume 0..23 hours in a day, 0..59 minutes in an hour. The library spec
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* has changed: we can no longer assume that there are 0..59 seconds in a
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* minute.
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*/
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gmt = *gmtime(&when);
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lt = localtime(&when);
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gmtoff = (lt->tm_hour - gmt.tm_hour) * HOUR_MIN + lt->tm_min - gmt.tm_min;
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if (lt->tm_year < gmt.tm_year)
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gmtoff -= DAY_MIN;
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else if (lt->tm_year > gmt.tm_year)
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gmtoff += DAY_MIN;
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else if (lt->tm_yday < gmt.tm_yday)
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gmtoff -= DAY_MIN;
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else if (lt->tm_yday > gmt.tm_yday)
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gmtoff += DAY_MIN;
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if (lt->tm_sec <= gmt.tm_sec - MIN_SEC)
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gmtoff -= 1;
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else if (lt->tm_sec >= gmt.tm_sec + MIN_SEC)
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gmtoff += 1;
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/*
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* First, format the date and wall-clock time. XXX The %e format (day of
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* month, leading zero replaced by blank) isn't in my POSIX book, but
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* many vendors seem to support it.
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*/
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#ifdef MISSING_STRFTIME_E
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#define STRFTIME_FMT "%a, %d %b %Y %H:%M:%S "
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#else
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#define STRFTIME_FMT "%a, %e %b %Y %H:%M:%S "
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#endif
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while (strftime(vstring_end(vp), vstring_avail(vp), STRFTIME_FMT, lt) == 0)
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VSTRING_SPACE(vp, 100);
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VSTRING_SKIP(vp);
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/*
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* Then, add the UTC offset.
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*/
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if (gmtoff < -DAY_MIN || gmtoff > DAY_MIN)
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msg_panic("UTC time offset %d is larger than one day", gmtoff);
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vstring_sprintf_append(vp, "%+03d%02d", (int) (gmtoff / HOUR_MIN),
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(int) (gmtoff % HOUR_MIN));
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/*
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* Finally, add the time zone name.
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*/
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while (strftime(vstring_end(vp), vstring_avail(vp), " (%Z)", lt) == 0)
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VSTRING_SPACE(vp, 100);
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VSTRING_SKIP(vp);
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return (vstring_str(vp));
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}
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#ifdef TEST
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#include <vstream.h>
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main(void)
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{
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vstream_printf("%s\n", mail_date(time((time_t *) 0)));
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vstream_fflush(VSTREAM_OUT);
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return (0);
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}
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#endif
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