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