/**

 *

 * strftime.c

 *

 * implements the ansi c function strftime()

 *

 * written 6 september 1989 by jim nutt

 * released into the public domain by jim nutt

 *

 * modified 21-Oct-89 by Rob Duff

 *

 * modified 08-Dec-04 by Tobi Oetiker (added %V)

**/

#include <stddef.h>     /* for size_t */

#include <stdarg.h>     /* for va_arg */

#include <time.h>       /* for struct tm */

#include "strftime.h"

static char *aday[] = {

    "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"

};

static char *day[] = {

    "Sunday", "Monday", "Tuesday", "Wednesday",

    "Thursday", "Friday", "Saturday"

};

static char *amonth[] = {

    "Jan", "Feb", "Mar", "Apr", "May", "Jun",

    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"

};

static char *month[] = {

    "January", "February", "March", "April", "May", "June",

    "July", "August", "September", "October", "November", "December"

};

char *tzname_[2] = {"CST", "CDT"};        /* Add your own defaults here */

static char buf[26];

static void strfmt(char *str, const char *fmt, ...);

/**

 *

 * size_t strftime_(char *str,

 *                  size_t maxs,

 *                  const char *fmt,

 *                  const struct tm *t)

 *

 *      this functions acts much like a sprintf for time/date output.

 *      given a pointer to an output buffer, a format string and a

 *      time, it copies the time to the output buffer formatted in

 *      accordance with the format string.  the parameters are used

 *      as follows:

 *

 *          str is a pointer to the output buffer, there should

 *          be at least maxs characters available at the address

 *          pointed to by str.

 *

 *          maxs is the maximum number of characters to be copied

 *          into the output buffer, included the '\0' terminator

 *

 *          fmt is the format string.  a percent sign (%) is used

 *          to indicate that the following character is a special

 *          format character.  the following are valid format

 *          characters:

 *

 *              %A      full weekday name (Monday)

 *              %a      abbreviated weekday name (Mon)

 *              %B      full month name (January)

 *              %b      abbreviated month name (Jan)

 *              %c      standard date and time representation

 *              %d      day-of-month (01-31)

 *              %H      hour (24 hour clock) (00-23)

 *              %I      hour (12 hour clock) (01-12)

 *              %j      day-of-year (001-366)

 *              %M      minute (00-59)

 *              %m      month (01-12)

 *              %p      local equivalent of AM or PM

 *              %S      second (00-59)

 *              %U      week-of-year, first day sunday (00-53)

 *              %W      week-of-year, first day monday (00-53)

 *              %V      ISO 8601 Week number 

 *              %w      weekday (0-6, sunday is 0)

 *              %X      standard time representation

 *              %x      standard date representation

 *              %Y      year with century

 *              %y      year without century (00-99)

 *              %Z      timezone name

 *              %%      percent sign

 *

 *      the standard date string is equivalent to:

 *

 *          %a %b %d %Y

 *

 *      the standard time string is equivalent to:

 *

 *          %H:%M:%S

 *

 *      the standard date and time string is equivalent to:

 *

 *          %a %b %d %H:%M:%S %Y

 *

 *      strftime_() returns the number of characters placed in the

 *      buffer, not including the terminating \0, or zero if more

 *      than maxs characters were produced.

 *

**/

size_t strftime_(char *s, size_t maxs, const char *f, const struct tm *t)

{

      int w,d;

      char *p, *q, *r;

      p = s;

      q = s + maxs - 1;

      while ((*f != '\0'))

      {

            if (*f++ == '%')

            {

                  r = buf;

                  switch (*f++)

                  {

                  case '%' :

                        r = "%";

                        break;

                  case 'a' :

                        r = aday[t->tm_wday];

                        break;

                  case 'A' :

                        r = day[t->tm_wday];

                        break;

                  case 'b' :

                        r = amonth[t->tm_mon];

                        break;

                  case 'B' :

                        r = month[t->tm_mon];

                        break;

                  case 'c' :

                        strfmt(r, "%0 %0 %2 %2:%2:%2 %4",

                              aday[t->tm_wday], amonth[t->tm_mon],

                              t->tm_mday,t->tm_hour, t->tm_min,

                              t->tm_sec, t->tm_year+1900);

                        break;

                  case 'd' :

                        strfmt(r,"%2",t->tm_mday);

                        break;

                  case 'H' :

                        strfmt(r,"%2",t->tm_hour);

                        break;

                  case 'I' :

                        strfmt(r,"%2",(t->tm_hour%12)?t->tm_hour%12:12);

                        break;

                  case 'j' :

                        strfmt(r,"%3",t->tm_yday+1);

                        break;

                  case 'm' :

                        strfmt(r,"%2",t->tm_mon+1);

                        break;

                  case 'M' :

                        strfmt(r,"%2",t->tm_min);

                        break;

                  case 'p' :

                        r = (t->tm_hour>11)?"PM":"AM";

                        break;

                  case 'S' :

                        strfmt(r,"%2",t->tm_sec);

                        break;

                  case 'U' :

                        w = t->tm_yday/7;

                        if (t->tm_yday%7 > t->tm_wday)

                              w++;

                        strfmt(r, "%2", w);

                        break;

                  case 'W' :

                        w = t->tm_yday/7;

                        if (t->tm_yday%7 > (t->tm_wday+6)%7)

                              w++;

                        strfmt(r, "%2", w);

                        break;

                  case 'V':

                        /* ISO 8601 Week Of Year:

                           If the week (Monday - Sunday) containing January 1 has four or more

                           days in the new year, then it is week 1; otherwise it is week 53 of

                           the previous year and the next week is week one. */

  		        w  =  (t->tm_yday + 7 - (t->tm_wday ? t->tm_wday - 1 : 6)) / 7;

                        d  =  (t->tm_yday + 7 - (t->tm_wday ? t->tm_wday - 1 : 6)) % 7;

                        if (d >= 4) { w++; } else if (w == 0) { w = 53; }

                        strfmt(r, "%2", w);

                        break;

                  case 'w' :

                        strfmt(r,"%1",t->tm_wday);

                        break;

                  case 'x' :

                        strfmt(r, "%3s %3s %2 %4", aday[t->tm_wday],

                              amonth[t->tm_mon], t->tm_mday, t->tm_year+1900);

                        break;

                  case 'X' :

                        strfmt(r, "%2:%2:%2", t->tm_hour,

                              t->tm_min, t->tm_sec);

                        break;

                  case 'y' :

                        strfmt(r,"%2",t->tm_year%100);

                        break;

                  case 'Y' :

                        strfmt(r,"%4",t->tm_year+1900);

                        break;

                  case 'Z' :

                        r = (t->tm_isdst && tzname_[1][0]) ?

                              tzname_[1] : tzname_[0];

                        break;

                  default:

                        buf[0] = '%';     /* reconstruct the format */

                        buf[1] = f[-1];

                        buf[2] = '\0';

                        if (buf[1] == 0)

                              f--;        /* back up if at end of string */

                  }

                  while (*r)

                  {

                        if (p == q)

                        {

                              *q = '\0';

                              return 0;

                        }

                        *p++ = *r++;

                  }

            }

            else

            {

                  if (p == q)

                  {

                        *q = '\0';

                        return 0;

                  }

                  *p++ = f[-1];

            }

      }

      *p = '\0';

      return p - s;

}

/*

 *  stdarg.h

 *

typedef void *va_list;

#define va_start(vp,v) (vp=((char*)&v)+sizeof(v))

#define va_arg(vp,t) (*((t*)(vp))++)

#define va_end(vp)

 *

 */

static int pow[5] = { 1, 10, 100, 1000, 10000 };

/**

 * static void strfmt(char *str, char *fmt);

 *

 * simple sprintf for strftime

 *

 * each format descriptor is of the form %n

 * where n goes from zero to four

 *

 * 0    -- string %s

 * 1..4 -- int %?.?d

 *

**/

static void strfmt(char *str, const char *fmt, ...)

{

      int ival, ilen;

      char *sval;

      va_list vp;

      va_start(vp, fmt);

      while (*fmt)

      {

            if (*fmt++ == '%')

            {

                  ilen = *fmt++ - '0';

                  if (ilen == 0)                /* zero means string arg */

                  {

                        sval = va_arg(vp, char*);

                        while (*sval)

                              *str++ = *sval++;

                  }

                  else                          /* always leading zeros */

                  {

                        ival = va_arg(vp, int);

                        while (ilen)

                        {

                              ival %= pow[ilen--];

                              *str++ = (char)('0' + ival / pow[ilen]);

                        }

                  }

            }

            else  *str++ = fmt[-1];

      }

      *str = '\0';

      va_end(vp);

}

#ifdef TEST

#include <stdio.h>      /* for printf */

#include <time.h>       /* for strftime */

char test[80];

int main(int argc, char *argv[])

{

      int len;

      char *fmt;

      time_t now;

      time(&now;;

      fmt = (argc == 1) ? "%I:%M %p\n%c\n" : argv[1];

      len = strftime_(test,sizeof test, fmt, localtime(&now));

      printf("%d: %s\n", len, test);

      return !len;

}

#endif /* TEST */