gdate.c

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g_date_is_last_of_month (const GDate *d)
{
  gint index;
  
  g_return_val_if_fail (d != NULL, FALSE);
  g_return_val_if_fail (g_date_valid (d), FALSE);
  
  if (!d->dmy) 
    {
      g_date_update_dmy (d);
    }
  g_return_val_if_fail (d->dmy, FALSE);  
  
  index = g_date_is_leap_year (d->year) ? 1 : 0;
  
  if (d->day == days_in_months[index][d->month]) return TRUE;
  else return FALSE;
}

void         
g_date_add_days (GDate *d, guint ndays)
{
  g_return_if_fail (d != NULL);
  g_return_if_fail (g_date_valid (d));
  
  if (!d->julian)
    {
      g_date_update_julian (d);
    }
  g_return_if_fail (d->julian);
  
  d->julian_days += ndays;
  d->dmy = FALSE;
}

void         
g_date_subtract_days (GDate *d, guint ndays)
{
  g_return_if_fail (d != NULL);
  g_return_if_fail (g_date_valid (d));
  
  if (!d->julian)
    {
      g_date_update_julian (d);
    }
  g_return_if_fail (d->julian);
  g_return_if_fail (d->julian_days > ndays);
  
  d->julian_days -= ndays;
  d->dmy = FALSE;
}

void         
g_date_add_months (GDate       *d, 
                   guint        nmonths)
{
  guint years, months;
  gint index;
  
  g_return_if_fail (d != NULL);
  g_return_if_fail (g_date_valid (d));
  
  if (!d->dmy) 
    {
      g_date_update_dmy (d);
    }
  g_return_if_fail (d->dmy);  
  
  nmonths += d->month - 1;
  
  years  = nmonths/12;
  months = nmonths%12;
  
  d->month = months + 1;
  d->year  += years;
  
  index = g_date_is_leap_year (d->year) ? 1 : 0;
  
  if (d->day > days_in_months[index][d->month])
    d->day = days_in_months[index][d->month];
  
  d->julian = FALSE;
  
  g_return_if_fail (g_date_valid (d));
}

void         
g_date_subtract_months (GDate       *d, 
                        guint        nmonths)
{
  guint years, months;
  gint index;
  
  g_return_if_fail (d != NULL);
  g_return_if_fail (g_date_valid (d));
  
  if (!d->dmy) 
    {
      g_date_update_dmy (d);
    }
  g_return_if_fail (d->dmy);  
  
  years  = nmonths/12;
  months = nmonths%12;
  
  g_return_if_fail (d->year > years);
  
  d->year  -= years;
  
  if (d->month > months) d->month -= months;
  else 
    {
      months -= d->month;
      d->month = 12 - months;
      d->year -= 1;
    }
  
  index = g_date_is_leap_year (d->year) ? 1 : 0;
  
  if (d->day > days_in_months[index][d->month])
    d->day = days_in_months[index][d->month];
  
  d->julian = FALSE;
  
  g_return_if_fail (g_date_valid (d));
}

void         
g_date_add_years (GDate       *d, 
                  guint        nyears)
{
  g_return_if_fail (d != NULL);
  g_return_if_fail (g_date_valid (d));
  
  if (!d->dmy) 
    {
      g_date_update_dmy (d);
    }
  g_return_if_fail (d->dmy);  
  
  d->year += nyears;
  
  if (d->month == 2 && d->day == 29)
    {
      if (!g_date_is_leap_year (d->year))
        {
          d->day = 28;
        }
    }
  
  d->julian = FALSE;
}

void         
g_date_subtract_years (GDate       *d, 
                       guint        nyears)
{
  g_return_if_fail (d != NULL);
  g_return_if_fail (g_date_valid (d));
  
  if (!d->dmy) 
    {
      g_date_update_dmy (d);
    }
  g_return_if_fail (d->dmy);  
  g_return_if_fail (d->year > nyears);
  
  d->year -= nyears;
  
  if (d->month == 2 && d->day == 29)
    {
      if (!g_date_is_leap_year (d->year))
        {
          d->day = 28;
        }
    }
  
  d->julian = FALSE;
}


gboolean     
g_date_is_leap_year (GDateYear  year)
{
  g_return_val_if_fail (g_date_valid_year (year), FALSE);
  
  return ( (((year % 4) == 0) && ((year % 100) != 0)) ||
           (year % 400) == 0 );
}

guint8         
g_date_get_days_in_month (GDateMonth month, 
                          GDateYear  year)
{
  gint index;
  
  g_return_val_if_fail (g_date_valid_year (year), 0);
  g_return_val_if_fail (g_date_valid_month (month), 0);
  
  index = g_date_is_leap_year (year) ? 1 : 0;
  
  return days_in_months[index][month];
}

guint8       
g_date_get_monday_weeks_in_year (GDateYear  year)
{
  GDate d;
  
  g_return_val_if_fail (g_date_valid_year (year), 0);
  
  g_date_clear (&d, 1);
  g_date_set_dmy (&d, 1, 1, year);
  if (g_date_get_weekday (&d) == G_DATE_MONDAY) return 53;
  g_date_set_dmy (&d, 31, 12, year);
  if (g_date_get_weekday (&d) == G_DATE_MONDAY) return 53;
  if (g_date_is_leap_year (year)) 
    {
      g_date_set_dmy (&d, 2, 1, year);
      if (g_date_get_weekday (&d) == G_DATE_MONDAY) return 53;
      g_date_set_dmy (&d, 30, 12, year);
      if (g_date_get_weekday (&d) == G_DATE_MONDAY) return 53;
    }
  return 52;
}

guint8       
g_date_get_sunday_weeks_in_year (GDateYear  year)
{
  GDate d;
  
  g_return_val_if_fail (g_date_valid_year (year), 0);
  
  g_date_clear (&d, 1);
  g_date_set_dmy (&d, 1, 1, year);
  if (g_date_get_weekday (&d) == G_DATE_SUNDAY) return 53;
  g_date_set_dmy (&d, 31, 12, year);
  if (g_date_get_weekday (&d) == G_DATE_SUNDAY) return 53;
  if (g_date_is_leap_year (year)) 
    {
      g_date_set_dmy (&d, 2, 1, year);
      if (g_date_get_weekday (&d) == G_DATE_SUNDAY) return 53;
      g_date_set_dmy (&d, 30, 12, year);
      if (g_date_get_weekday (&d) == G_DATE_SUNDAY) return 53;
    }
  return 52;
}

gint         
g_date_compare (const GDate *lhs, 
                const GDate *rhs)
{
  g_return_val_if_fail (lhs != NULL, 0);
  g_return_val_if_fail (rhs != NULL, 0);
  g_return_val_if_fail (g_date_valid (lhs), 0);
  g_return_val_if_fail (g_date_valid (rhs), 0);
  
  /* Remember the self-comparison case! I think it works right now. */
  
  while (TRUE)
    {
      
      if (lhs->julian && rhs->julian) 
        {
          if (lhs->julian_days < rhs->julian_days) return -1;
          else if (lhs->julian_days > rhs->julian_days) return 1;
          else                                          return 0;
        }
      else if (lhs->dmy && rhs->dmy) 
        {
          if (lhs->year < rhs->year)               return -1;
          else if (lhs->year > rhs->year)               return 1;
          else 
            {
              if (lhs->month < rhs->month)         return -1;
              else if (lhs->month > rhs->month)         return 1;
              else 
                {
                  if (lhs->day < rhs->day)              return -1;
                  else if (lhs->day > rhs->day)              return 1;
                  else                                       return 0;
                }
              
            }
          
        }
      else
        {
          if (!lhs->julian) g_date_update_julian (lhs);
          if (!rhs->julian) g_date_update_julian (rhs);
          g_return_val_if_fail (lhs->julian, 0);
          g_return_val_if_fail (rhs->julian, 0);
        }
      
    }
  return 0; /* warnings */
}


void        
g_date_to_struct_tm (const GDate *d, 
                     struct tm   *tm)
{
  GDateWeekday day;
     
  g_return_if_fail (d != NULL);
  g_return_if_fail (g_date_valid (d));
  g_return_if_fail (tm != NULL);
  
  if (!d->dmy) 
    {
      g_date_update_dmy (d);
    }
  g_return_if_fail (d->dmy);
  
  /* zero all the irrelevant fields to be sure they're valid */
  
  /* On Linux and maybe other systems, there are weird non-POSIX
   * fields on the end of struct tm that choke strftime if they
   * contain garbage.  So we need to 0 the entire struct, not just the
   * fields we know to exist. 
   */
  
  memset (tm, 0x0, sizeof (struct tm));
  
  tm->tm_mday = d->day;
  tm->tm_mon  = d->month - 1; /* 0-11 goes in tm */
  tm->tm_year = ((int)d->year) - 1900; /* X/Open says tm_year can be negative */
  
  day = g_date_get_weekday (d);
  if (day == 7) day = 0; /* struct tm wants days since Sunday, so Sunday is 0 */
  
  tm->tm_wday = (int)day;
  
  tm->tm_yday = g_date_get_day_of_year (d) - 1; /* 0 to 365 */
  tm->tm_isdst = -1; /* -1 means "information not available" */
}

void
g_date_clamp (GDate *date,
	      const GDate *min_date,
	      const GDate *max_date)
{
  g_return_if_fail (date);
  g_return_if_fail (g_date_valid (date));
  if (min_date != NULL)
    g_return_if_fail (g_date_valid (min_date));
  if (max_date != NULL)
    g_return_if_fail (g_date_valid (max_date));
  if (min_date != NULL && max_date != NULL)
    g_return_if_fail (g_date_compare (min_date, max_date) <= 0);

  if (min_date && g_date_compare (date, min_date) < 0)
    *date = *min_date;

  if (max_date && g_date_compare (max_date, date) < 0)
    *date = *max_date;
}

void
g_date_order (GDate *date1,
              GDate *date2)
{
  g_return_if_fail (date1 != NULL);
  g_return_if_fail (date2 != NULL);
  g_return_if_fail (g_date_valid (date1));
  g_return_if_fail (g_date_valid (date2));

  if (g_date_compare (date1, date2) > 0)
    {
      GDate tmp = *date1;
      *date1 = *date2;
      *date2 = tmp;
    }
}

gsize     
g_date_strftime (gchar       *s, 
                 gsize        slen, 
                 const gchar *format, 
                 const GDate *d)
{
  struct tm tm;
  gsize locale_format_len = 0;
  gchar *locale_format;
  gsize tmplen;
  gchar *tmpbuf;
  gsize tmpbufsize;
  gsize convlen = 0;
  gchar *convbuf;
  GError *error = NULL;
  gsize retval;

  g_return_val_if_fail (d != NULL, 0);
  g_return_val_if_fail (g_date_valid (d), 0);
  g_return_val_if_fail (slen > 0, 0); 
  g_return_val_if_fail (format != 0, 0);
  g_return_val_if_fail (s != 0, 0);

  g_date_to_struct_tm (d, &tm);

  locale_format = g_locale_from_utf8 (format, -1, NULL, &locale_format_len, &error);

  if (error)
    {
      g_warning (G_STRLOC "Error converting format to locale encoding: %s\n", error->message);
      g_error_free (error);

      s[0] = '\0';
      return 0;
    }

  tmpbufsize = MAX (128, locale_format_len * 2);
  while (TRUE)
    {
      tmpbuf = g_malloc (tmpbufsize);

      /* Set the first byte to something other than '\0', to be able to
       * recognize whether strftime actually failed or just returned "".
       */
      tmpbuf[0] = '\1';
      tmplen = strftime (tmpbuf, tmpbufsize, locale_format, &tm);

      if (tmplen == 0 && tmpbuf[0] != '\0')
        {
          g_free (tmpbuf);
          tmpbufsize *= 2;

          if (tmpbufsize > 65536)
            {
              g_warning (G_STRLOC "Maximum buffer size for g_date_strftime exceeded: giving up\n");
              g_free (locale_format);

              s[0] = '\0';
              return 0;
            }
        }
      else
        break;
    }
  g_free (locale_format);

  convbuf = g_locale_to_utf8 (tmpbuf, tmplen, NULL, &convlen, &error);
  g_free (tmpbuf);

  if (error)
    {
      g_warning (G_STRLOC "Error converting results of strftime to UTF-8: %s\n", error->message);
      g_error_free (error);

      s[0] = '\0';
      return 0;
    }

  if (slen <= convlen)
    {
      /* Ensure only whole characters are copied into the buffer.
       */
      gchar *end = g_utf8_find_prev_char (convbuf, convbuf + slen);
      g_assert (end != NULL);
      convlen = end - convbuf;

      /* Return 0 because the buffer isn't large enough.
       */
      retval = 0;
    }
  else
    retval = convlen;

  memcpy (s, convbuf, convlen);
  s[convlen] = '\0';
  g_free (convbuf);

  return retval;
}