strftime.c

Newlib 嵌入式 C库 标准实现代码

	       9999		99		99
	       0999		09		99
	       0099		00		99
	       0001		00		01
	       0000		00		00
	       -001		-0		01
	       -099		-0		99
	       -999		-9		99
	       -1000		-10		00
	       -10000		-100		00
	       -2147481748	-21474817	48

	       Be careful of both overflow and sign adjustment due to the
	       asymmetric range of years.
	    */
	    int neg = tim_p->tm_year < -YEAR_BASE;
	    int century = tim_p->tm_year >= 0
	      ? tim_p->tm_year / 100 + YEAR_BASE / 100
	      : abs (tim_p->tm_year + YEAR_BASE) / 100;
            count += snprintf (&s[count], maxsize - count, "%s%.*d",
                               neg ? "-" : "", 2 - neg, century);
            if (count >= maxsize)
              return 0;
	  }
	  break;
	case 'd':
	case 'e':
	  if (count < maxsize - 2)
	    {
	      sprintf (&s[count], *format == 'd' ? "%.2d" : "%2d",
		       tim_p->tm_mday);
	      count += 2;
	    }
	  else
	    return 0;
	  break;
	case 'D':
	case 'x':
	  /* %m/%d/%y */
	  if (count < maxsize - 8)
	    {
	      sprintf (&s[count], "%.2d/%.2d/%.2d",
		       tim_p->tm_mon + 1, tim_p->tm_mday,
		       tim_p->tm_year >= 0 ? tim_p->tm_year % 100
		       : abs (tim_p->tm_year + YEAR_BASE) % 100);
	      count += 8;
	    }
	  else
	    return 0;
	  break;
        case 'F':
	  {
	    /* Length is not known because of %C%y, so recurse. */
	    size_t adjust = strftime (&s[count], maxsize - count,
				      "%C%y-%m-%d", tim_p);
	    if (adjust > 0)
	      count += adjust;
	    else
	      return 0;
	  }
          break;
        case 'g':
	  if (count < maxsize - 2)
	    {
	      /* Be careful of both overflow and negative years, thanks to
		 the asymmetric range of years.  */
	      int adjust = iso_year_adjust (tim_p);
	      int year = tim_p->tm_year >= 0 ? tim_p->tm_year % 100
		: abs (tim_p->tm_year + YEAR_BASE) % 100;
	      if (adjust < 0 && tim_p->tm_year <= -YEAR_BASE)
		adjust = 1;
	      else if (adjust > 0 && tim_p->tm_year < -YEAR_BASE)
		adjust = -1;
	      sprintf (&s[count], "%.2d",
		       ((year + adjust) % 100 + 100) % 100);
	      count += 2;
	    }
	  else
	    return 0;
          break;
        case 'G':
	  {
	    /* See the comments for 'C' and 'Y'; this is a variable length
	       field.  Although there is no requirement for a minimum number
	       of digits, we use 4 for consistency with 'Y'.  */
	    int neg = tim_p->tm_year < -YEAR_BASE;
	    int adjust = iso_year_adjust (tim_p);
	    int century = tim_p->tm_year >= 0
	      ? tim_p->tm_year / 100 + YEAR_BASE / 100
	      : abs (tim_p->tm_year + YEAR_BASE) / 100;
	    int year = tim_p->tm_year >= 0 ? tim_p->tm_year % 100
	      : abs (tim_p->tm_year + YEAR_BASE) % 100;
	    if (adjust < 0 && tim_p->tm_year <= -YEAR_BASE)
	      neg = adjust = 1;
	    else if (adjust > 0 && neg)
	      adjust = -1;
	    year += adjust;
	    if (year == -1)
	      {
		year = 99;
		--century;
	      }
	    else if (year == 100)
	      {
		year = 0;
		++century;
	      }
            count += snprintf (&s[count], maxsize - count, "%s%.*d%.2d",
                               neg ? "-" : "", 2 - neg, century, year);
            if (count >= maxsize)
              return 0;
	  }
          break;
	case 'H':
	case 'k':
	  if (count < maxsize - 2)
	    {
	      sprintf (&s[count], *format == 'k' ? "%2d" : "%.2d",
		       tim_p->tm_hour);
	      count += 2;
	    }
	  else
	    return 0;
	  break;
	case 'I':
	case 'l':
	  if (count < maxsize - 2)
	    {
	      if (tim_p->tm_hour == 0 ||
		  tim_p->tm_hour == 12)
		{
		  s[count++] = '1';
		  s[count++] = '2';
		}
	      else
		{
		  sprintf (&s[count], *format == 'I' ? "%.2d" : "%2d",
			   tim_p->tm_hour % 12);
		  count += 2;
		}
	    }
	  else
	    return 0;
	  break;
	case 'j':
	  if (count < maxsize - 3)
	    {
	      sprintf (&s[count], "%.3d",
		       tim_p->tm_yday + 1);
	      count += 3;
	    }
	  else
	    return 0;
	  break;
	case 'm':
	  if (count < maxsize - 2)
	    {
	      sprintf (&s[count], "%.2d",
		       tim_p->tm_mon + 1);
	      count += 2;
	    }
	  else
	    return 0;
	  break;
	case 'M':
	  if (count < maxsize - 2)
	    {
	      sprintf (&s[count], "%.2d",
		       tim_p->tm_min);
	      count += 2;
	    }
	  else
	    return 0;
	  break;
	case 'n':
	  if (count < maxsize - 1)
	    s[count++] = '\n';
	  else
	    return 0;
	  break;
	case 'p':
	  if (count < maxsize - 2)
	    {
	      if (tim_p->tm_hour < 12)
		s[count++] = 'A';
	      else
		s[count++] = 'P';

	      s[count++] = 'M';
	    }
	  else
	    return 0;
	  break;
	case 'r':
	  if (count < maxsize - 11)
	    {
	      if (tim_p->tm_hour == 0 ||
		  tim_p->tm_hour == 12)
		{
		  s[count++] = '1';
		  s[count++] = '2';
		}
	      else
		{
		  sprintf (&s[count], "%.2d", tim_p->tm_hour % 12);
		  count += 2;
		}
	      s[count++] = ':';
	      sprintf (&s[count], "%.2d",
		       tim_p->tm_min);
	      count += 2;
	      s[count++] = ':';
	      sprintf (&s[count], "%.2d",
		       tim_p->tm_sec);
	      count += 2;
	      s[count++] = ' ';
	      if (tim_p->tm_hour < 12)
		s[count++] = 'A';
	      else
		s[count++] = 'P';

	      s[count++] = 'M';
	    }
	  else
	    return 0;
	  break;
        case 'R':
          if (count < maxsize - 5)
            {
              sprintf (&s[count], "%.2d:%.2d", tim_p->tm_hour, tim_p->tm_min);
              count += 5;
            }
          else
            return 0;
          break;
	case 'S':
	  if (count < maxsize - 2)
	    {
	      sprintf (&s[count], "%.2d",
		       tim_p->tm_sec);
	      count += 2;
	    }
	  else
	    return 0;
	  break;
	case 't':
	  if (count < maxsize - 1)
	    s[count++] = '\t';
	  else
	    return 0;
	  break;
        case 'T':
        case 'X':
          if (count < maxsize - 8)
            {
              sprintf (&s[count], "%.2d:%.2d:%.2d", tim_p->tm_hour,
                       tim_p->tm_min, tim_p->tm_sec);
              count += 8;
            }
          else
            return 0;
          break;
        case 'u':
          if (count < maxsize - 1)
            {
              if (tim_p->tm_wday == 0)
                s[count++] = '7';
              else
                s[count++] = '0' + tim_p->tm_wday;
            }
          else
            return 0;
          break;
	case 'U':
	  if (count < maxsize - 2)
	    {
	      sprintf (&s[count], "%.2d",
		       (tim_p->tm_yday + 7 -
			tim_p->tm_wday) / 7);
	      count += 2;
	    }
	  else
	    return 0;
	  break;
        case 'V':
	  if (count < maxsize - 2)
	    {
	      int adjust = iso_year_adjust (tim_p);
	      int wday = (tim_p->tm_wday) ? tim_p->tm_wday - 1 : 6;
	      int week = (tim_p->tm_yday + 10 - wday) / 7;
	      if (adjust > 0)
		week = 1;
	      else if (adjust < 0)
		/* Previous year has 53 weeks if current year starts on
		   Fri, and also if current year starts on Sat and
		   previous year was leap year.  */
		week = 52 + (4 >= (wday - tim_p->tm_yday
				   - isleap (tim_p->tm_year
					     + (YEAR_BASE - 1
						- (tim_p->tm_year < 0
						   ? 0 : 2000)))));
	      sprintf (&s[count], "%.2d", week);
	      count += 2;
	    }
	  else
	    return 0;
          break;
	case 'w':
	  if (count < maxsize - 1)
            s[count++] = '0' + tim_p->tm_wday;
	  else
	    return 0;
	  break;
	case 'W':
	  if (count < maxsize - 2)
	    {
	      int wday = (tim_p->tm_wday) ? tim_p->tm_wday - 1 : 6;
	      sprintf (&s[count], "%.2d",
		       (tim_p->tm_yday + 7 - wday) / 7);
	      count += 2;
	    }
	  else
	    return 0;
	  break;
	case 'y':
	  if (count < maxsize - 2)
	    {
	      /* Be careful of both overflow and negative years, thanks to
		 the asymmetric range of years.  */
	      int year = tim_p->tm_year >= 0 ? tim_p->tm_year % 100
		: abs (tim_p->tm_year + YEAR_BASE) % 100;
	      sprintf (&s[count], "%.2d", year);
	      count += 2;
	    }
	  else
	    return 0;
	  break;
	case 'Y':
	  {
	    /* Length is not known because of %C%y, so recurse. */
	    size_t adjust = strftime (&s[count], maxsize - count,
				      "%C%y", tim_p);
	    if (adjust > 0)
	      count += adjust;
	    else
	      return 0;
	  }
	  break;
        case 'z':
          if (tim_p->tm_isdst >= 0)
            {
	      if (count < maxsize - 5)
		{
		  long offset;
		  __tzinfo_type *tz = __gettzinfo ();
		  TZ_LOCK;
		  /* The sign of this is exactly opposite the envvar TZ.  We
		     could directly use the global _timezone for tm_isdst==0,
		     but have to use __tzrule for daylight savings.  */
		  offset = -tz->__tzrule[tim_p->tm_isdst > 0].offset;
		  TZ_UNLOCK;
		  sprintf (&s[count], "%+03ld%.2ld", offset / SECSPERHOUR,
			   labs (offset / SECSPERMIN) % 60L);
		  count += 5;
		}
	      else
		return 0;
            }
          break;
	case 'Z':
	  if (tim_p->tm_isdst >= 0)
	    {
	      int size;
	      TZ_LOCK;
	      size = strlen(_tzname[tim_p->tm_isdst > 0]);
	      for (i = 0; i < size; i++)
		{
		  if (count < maxsize - 1)
		    s[count++] = _tzname[tim_p->tm_isdst > 0][i];
		  else
		    {
		      TZ_UNLOCK;
		      return 0;
		    }
		}
	      TZ_UNLOCK;
	    }
	  break;
	case '%':
	  if (count < maxsize - 1)
	    s[count++] = '%';
	  else
	    return 0;
	  break;
	}
      if (*format)
	format++;
      else
	break;
    }
  if (maxsize)
    s[count] = '\0';

  return count;
}