/* rfc822date.c -- Generate an 822 date
 $Id: rfc822date.c,v 1.4 2003/02/13 20:15:42 rjs3 Exp $
 
 * Copyright (c) 1998-2003 Carnegie Mellon University.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. 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.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any other legal
 *    details, please contact  
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
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 */

#include <stdio.h>
#include <time.h>

#include "assert.h"
#include "rfc822date.h"
#include "gmtoff.h"

static char *month[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
                         "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };

static char *wday[] = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };

/* 'buf' must be at least 80 characters */
void rfc822date_gen(char *buf, size_t len, time_t t)
{
    struct tm *tm;
    long gmtoff;
    int gmtnegative = 0;

    assert(buf != NULL);

    tm = localtime(&t);
    gmtoff = gmtoff_of(tm, t);
    if (gmtoff < 0) {
	gmtoff = -gmtoff;
	gmtnegative = 1;
    }
    gmtoff /= 60;

    snprintf(buf, len, "%s, %02d %s %4d %02d:%02d:%02d %c%.2lu%.2lu",
	     wday[tm->tm_wday], 
	     tm->tm_mday, month[tm->tm_mon], tm->tm_year + 1900,
	     tm->tm_hour, tm->tm_min, tm->tm_sec,
	     gmtnegative ? '-' : '+', gmtoff / 60, gmtoff % 60);
}
