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/*

 * strftime.c

 * Original Author:     G. Haley

 * Additions from:      Eric Blake

 *

 * Places characters into the array pointed to by s as controlled by the string

 * pointed to by format. If the total number of resulting characters including

 * the terminating null character is not more than maxsize, returns the number

 * of characters placed into the array pointed to by s (not including the

 * terminating null character); otherwise zero is returned and the contents of

 * the array indeterminate.

 */

/*

FUNCTION

<<strftime>>---flexible calendar time formatter

INDEX

        strftime

ANSI_SYNOPSIS

        #include <time.h>

        size_t strftime(char *<[s]>, size_t <[maxsize]>,

                        const char *<[format]>, const struct tm *<[timp]>);

TRAD_SYNOPSIS

        #include <time.h>

        size_t strftime(<[s]>, <[maxsize]>, <[format]>, <[timp]>)

        char *<[s]>;

        size_t <[maxsize]>;

        char *<[format]>;

        struct tm *<[timp]>;

DESCRIPTION

<<strftime>> converts a <<struct tm>> representation of the time (at

<[timp]>) into a null-terminated string, starting at <[s]> and occupying

no more than <[maxsize]> characters.

You control the format of the output using the string at <[format]>.

<<*<[format]>>> can contain two kinds of specifications: text to be

copied literally into the formatted string, and time conversion

specifications.  Time conversion specifications are two- and

three-character sequences beginning with `<<%>>' (use `<<%%>>' to

include a percent sign in the output).  Each defined conversion

specification selects only the specified field(s) of calendar time

data from <<*<[timp]>>>, and converts it to a string in one of the

following ways:

o+

o %a

A three-letter abbreviation for the day of the week. [tm_wday]

o %A

The full name for the day of the week, one of `<<Sunday>>',

`<<Monday>>', `<<Tuesday>>', `<<Wednesday>>', `<<Thursday>>',

`<<Friday>>', or `<<Saturday>>'. [tm_wday]

o %b

A three-letter abbreviation for the month name. [tm_mon]

o %B

The full name of the month, one of `<<January>>', `<<February>>',

`<<March>>', `<<April>>', `<<May>>', `<<June>>', `<<July>>',

`<<August>>', `<<September>>', `<<October>>', `<<November>>',

`<<December>>'. [tm_mon]

o %c

A string representing the complete date and time, in the form

`<<"%a %b %e %H:%M:%S %Y">>' (example "Mon Apr 01 13:13:13

1992"). [tm_sec, tm_min, tm_hour, tm_mday, tm_mon, tm_year, tm_wday]

o %C

The century, that is, the year divided by 100 then truncated.  For

4-digit years, the result is zero-padded and exactly two characters;

but for other years, there may a negative sign or more digits.  In

this way, `<<%C%y>>' is equivalent to `<<%Y>>'. [tm_year]

o %d

The day of the month, formatted with two digits (from `<<01>>' to

`<<31>>'). [tm_mday]

o %D

A string representing the date, in the form `<<"%m/%d/%y">>'.

[tm_mday, tm_mon, tm_year]

o %e

The day of the month, formatted with leading space if single digit

(from `<<1>>' to `<<31>>'). [tm_mday]

o %E<<x>>

In some locales, the E modifier selects alternative representations of

certain modifiers <<x>>.  But in the "C" locale supported by newlib,

it is ignored, and treated as %<<x>>.

o %F

A string representing the ISO 8601:2000 date format, in the form

`<<"%Y-%m-%d">>'. [tm_mday, tm_mon, tm_year]

o %g

The last two digits of the week-based year, see specifier %G (from

`<<00>>' to `<<99>>'). [tm_year, tm_wday, tm_yday]

o %G

The week-based year. In the ISO 8601:2000 calendar, week 1 of the year

includes January 4th, and begin on Mondays. Therefore, if January 1st,

2nd, or 3rd falls on a Sunday, that day and earlier belong to the last

week of the previous year; and if December 29th, 30th, or 31st falls

on Monday, that day and later belong to week 1 of the next year.  For

consistency with %Y, it always has at least four characters.

Example: "%G" for Saturday 2nd January 1999 gives "1998", and for

Tuesday 30th December 1997 gives "1998". [tm_year, tm_wday, tm_yday]

o %h

A three-letter abbreviation for the month name (synonym for

"%b"). [tm_mon]

o %H

The hour (on a 24-hour clock), formatted with two digits (from

`<<00>>' to `<<23>>'). [tm_hour]

o %I

The hour (on a 12-hour clock), formatted with two digits (from

`<<01>>' to `<<12>>'). [tm_hour]

o %j

The count of days in the year, formatted with three digits

(from `<<001>>' to `<<366>>'). [tm_yday]

o %k

The hour (on a 24-hour clock), formatted with leading space if single

digit (from `<<0>>' to `<<23>>'). Non-POSIX extension. [tm_hour]

o %l

The hour (on a 12-hour clock), formatted with leading space if single

digit (from `<<1>>' to `<<12>>'). Non-POSIX extension. [tm_hour]

o %m

The month number, formatted with two digits (from `<<01>>' to `<<12>>').

[tm_mon]

o %M

The minute, formatted with two digits (from `<<00>>' to `<<59>>'). [tm_min]

o %n

A newline character (`<<\n>>').

o %O<<x>>

In some locales, the O modifier selects alternative digit characters

for certain modifiers <<x>>.  But in the "C" locale supported by newlib, it

is ignored, and treated as %<<x>>.

o %p

Either `<<AM>>' or `<<PM>>' as appropriate. [tm_hour]

o %r

The 12-hour time, to the second.  Equivalent to "%I:%M:%S %p". [tm_sec,

tm_min, tm_hour]

o %R

The 24-hour time, to the minute.  Equivalent to "%H:%M". [tm_min, tm_hour]

o %S

The second, formatted with two digits (from `<<00>>' to `<<60>>').  The

value 60 accounts for the occasional leap second. [tm_sec]

o %t

A tab character (`<<\t>>').

o %T

The 24-hour time, to the second.  Equivalent to "%H:%M:%S". [tm_sec,

tm_min, tm_hour]

o %u

The weekday as a number, 1-based from Monday (from `<<1>>' to

`<<7>>'). [tm_wday]

o %U

The week number, where weeks start on Sunday, week 1 contains the first

Sunday in a year, and earlier days are in week 0.  Formatted with two

digits (from `<<00>>' to `<<53>>').  See also <<%W>>. [tm_wday, tm_yday]

o %V

The week number, where weeks start on Monday, week 1 contains January 4th,

and earlier days are in the previous year.  Formatted with two digits

(from `<<01>>' to `<<53>>').  See also <<%G>>. [tm_year, tm_wday, tm_yday]

o %w

The weekday as a number, 0-based from Sunday (from `<<0>>' to `<<6>>').

[tm_wday]

o %W

The week number, where weeks start on Monday, week 1 contains the first

Monday in a year, and earlier days are in week 0.  Formatted with two

digits (from `<<00>>' to `<<53>>'). [tm_wday, tm_yday]

o %x

A string representing the complete date, equivalent to "%m/%d/%y".

[tm_mon, tm_mday, tm_year]

o %X

A string representing the full time of day (hours, minutes, and

seconds), equivalent to "%H:%M:%S". [tm_sec, tm_min, tm_hour]

o %y

The last two digits of the year (from `<<00>>' to `<<99>>'). [tm_year]

o %Y

The full year, equivalent to <<%C%y>>.  It will always have at least four

characters, but may have more.  The year is accurate even when tm_year

added to the offset of 1900 overflows an int. [tm_year]

o %z

The offset from UTC.  The format consists of a sign (negative is west of

Greewich), two characters for hour, then two characters for minutes

(-hhmm or +hhmm).  If tm_isdst is negative, the offset is unknown and no

output is generated; if it is zero, the offset is the standard offset for

the current time zone; and if it is positive, the offset is the daylight

savings offset for the current timezone. The offset is determined from

the TZ environment variable, as if by calling tzset(). [tm_isdst]

o %Z

The time zone name.  If tm_isdst is negative, no output is generated.

Otherwise, the time zone name is based on the TZ environment variable,

as if by calling tzset(). [tm_isdst]

o %%

A single character, `<<%>>'.

o-

RETURNS

When the formatted time takes up no more than <[maxsize]> characters,

the result is the length of the formatted string.  Otherwise, if the

formatting operation was abandoned due to lack of room, the result is

<<0>>, and the string starting at <[s]> corresponds to just those

parts of <<*<[format]>>> that could be completely filled in within the

<[maxsize]> limit.

PORTABILITY

ANSI C requires <<strftime>>, but does not specify the contents of

<<*<[s]>>> when the formatted string would require more than

<[maxsize]> characters.  Unrecognized specifiers and fields of

<<timp>> that are out of range cause undefined results.  Since some

formats expand to 0 bytes, it is wise to set <<*<[s]>>> to a nonzero

value beforehand to distinguish between failure and an empty string.

This implementation does not support <<s>> being NULL, nor overlapping

<<s>> and <<format>>.

<<strftime>> requires no supporting OS subroutines.

*/

#include <stddef.h>

#include <stdio.h>

#include <time.h>

#include <string.h>

#include <stdlib.h>

#include "local.h"

static _CONST int dname_len[7] =

{6, 6, 7, 9, 8, 6, 8};

static _CONST char *_CONST dname[7] =

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

 "Thursday", "Friday", "Saturday"};

static _CONST int mname_len[12] =

{7, 8, 5, 5, 3, 4, 4, 6, 9, 7, 8, 8};

static _CONST char *_CONST mname[12] =

{"January", "February", "March", "April",

 "May", "June", "July", "August", "September", "October", "November",

 "December"};

/* Using the tm_year, tm_wday, and tm_yday components of TIM_P, return

   -1, 0, or 1 as the adjustment to add to the year for the ISO week

   numbering used in "%g%G%V", avoiding overflow.  */

static int

_DEFUN (iso_year_adjust, (tim_p),

        _CONST struct tm *tim_p)

{

  /* Account for fact that tm_year==0 is year 1900.  */

  int leap = isleap (tim_p->tm_year + (YEAR_BASE

                                       - (tim_p->tm_year < 0 ? 0 : 2000)));

  /* Pack the yday, wday, and leap year into a single int since there are so

     many disparate cases.  */

#define PACK(yd, wd, lp) (((yd) << 4) + (wd << 1) + (lp))

  switch (PACK (tim_p->tm_yday, tim_p->tm_wday, leap))

    {

    case PACK (0, 5, 0): /* Jan 1 is Fri, not leap.  */

    case PACK (0, 6, 0): /* Jan 1 is Sat, not leap.  */

    case PACK (0, 0, 0): /* Jan 1 is Sun, not leap.  */

    case PACK (0, 5, 1): /* Jan 1 is Fri, leap year.  */

    case PACK (0, 6, 1): /* Jan 1 is Sat, leap year.  */

    case PACK (0, 0, 1): /* Jan 1 is Sun, leap year.  */

    case PACK (1, 6, 0): /* Jan 2 is Sat, not leap.  */

    case PACK (1, 0, 0): /* Jan 2 is Sun, not leap.  */

    case PACK (1, 6, 1): /* Jan 2 is Sat, leap year.  */

    case PACK (1, 0, 1): /* Jan 2 is Sun, leap year.  */

    case PACK (2, 0, 0): /* Jan 3 is Sun, not leap.  */

    case PACK (2, 0, 1): /* Jan 3 is Sun, leap year.  */

      return -1; /* Belongs to last week of previous year.  */

    case PACK (362, 1, 0): /* Dec 29 is Mon, not leap.  */

    case PACK (363, 1, 1): /* Dec 29 is Mon, leap year.  */

    case PACK (363, 1, 0): /* Dec 30 is Mon, not leap.  */

    case PACK (363, 2, 0): /* Dec 30 is Tue, not leap.  */

    case PACK (364, 1, 1): /* Dec 30 is Mon, leap year.  */

    case PACK (364, 2, 1): /* Dec 30 is Tue, leap year.  */

    case PACK (364, 1, 0): /* Dec 31 is Mon, not leap.  */

    case PACK (364, 2, 0): /* Dec 31 is Tue, not leap.  */

    case PACK (364, 3, 0): /* Dec 31 is Wed, not leap.  */

    case PACK (365, 1, 1): /* Dec 31 is Mon, leap year.  */

    case PACK (365, 2, 1): /* Dec 31 is Tue, leap year.  */

    case PACK (365, 3, 1): /* Dec 31 is Wed, leap year.  */

      return 1; /* Belongs to first week of next year.  */

    }

  return 0; /* Belongs to specified year.  */

#undef PACK

}

size_t

_DEFUN (strftime, (s, maxsize, format, tim_p),

        char *s _AND

        size_t maxsize _AND

        _CONST char *format _AND

        _CONST struct tm *tim_p)

{

  size_t count = 0;

  int i;

  for (;;)

    {

      while (*format && *format != '%')

        {

          if (count < maxsize - 1)

            s[count++] = *format++;

          else

            return 0;

        }

      if (*format == '\0')

        break;

      format++;

      if (*format == 'E' || *format == 'O')

        format++;

      switch (*format)

        {

        case 'a':

          for (i = 0; i < 3; i++)

            {

              if (count < maxsize - 1)

                s[count++] =

                  dname[tim_p->tm_wday][i];

              else

                return 0;

            }

          break;

        case 'A':

          for (i = 0; i < dname_len[tim_p->tm_wday]; i++)

            {

              if (count < maxsize - 1)

                s[count++] =

                  dname[tim_p->tm_wday][i];

              else

                return 0;

            }

          break;

        case 'b':

        case 'h':

          for (i = 0; i < 3; i++)

            {

              if (count < maxsize - 1)

                s[count++] =

                  mname[tim_p->tm_mon][i];

              else

                return 0;

            }

          break;

        case 'B':

          for (i = 0; i < mname_len[tim_p->tm_mon]; i++)

            {

              if (count < maxsize - 1)

                s[count++] =

                  mname[tim_p->tm_mon][i];

              else

                return 0;

            }

          break;

        case 'c':

          {

            /* Length is not known because of %C%y, so recurse. */

            size_t adjust = strftime (&s[count], maxsize - count,

                                      "%a %b %e %H:%M:%S %C%y", tim_p);

            if (adjust > 0)

              count += adjust;

            else

              return 0;

          }

          break;

        case 'C':

          {

            /* Examples of (tm_year + YEAR_BASE) that show how %Y == %C%y

               with 32-bit int.

               %Y               %C              %y

               2147485547       21474855        47

               10000            100             00

               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;