proposed changes to strftime.c

May 25, 1993

      Here are some proposed changes to strftime.c:

	Use ISO standard date format for %x; this is more appropriate than the
	American date format, which confuses non-Americans.  Especially for
	dates like 01/02/03; the ISO date 2003-01-02 is much clearer for
	everybody, and it sorts correctly too.

	_conv fails when n is negative, and it's hard to get it exactly right
	when n is INT_MIN.  Why not let sprintf do the work?

	The buffer inside _conv might overflow with 64-bit ints.

	Use `const' when possible, so that the data can be shared in the
	read-only text segment.

	Use function prototypes when possible, to keep lint checkers happy.

	There's a /* in a comment just before `You are understood not to
	expect this.'

Here's a patch.

*** draft-strftime.c	Tue May 25 10:39:33 1993
--- draft-strftime1.c	Tue May 25 11:28:38 1993
***************
*** 1,6 ****
  #ifndef lint
  #ifndef NOID
! static char	elsieid[] = "@(#)strftime.c	7.4";
  /*
  ** Based on the UCB version whose ID appears below.
  ** This is ANSIish only when time is treated identically in all locales and
--- 1,6 ----
  #ifndef lint
  #ifndef NOID
! static const char elsieid[] = "@(#)strftime.c	7.4";
  /*
  ** Based on the UCB version whose ID appears below.
  ** This is ANSIish only when time is treated identically in all locales and
***************
*** 26,64 ****
   */

  #if defined(LIBC_SCCS) && !defined(lint)
! static char sccsid[] = "@(#)strftime.c	5.4 (Berkeley) 3/14/89";
  #endif /* LIBC_SCCS and not lint */

! #include "sys/types.h"
! #include "time.h"
  #include "tzfile.h"

! static char *afmt[] = {
! 	"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat",
  };
! static char *Afmt[] = {
  	"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
! 	"Saturday",
  };
! static char *bfmt[] = {
  	"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep",
! 	"Oct", "Nov", "Dec",
  };
! static char *Bfmt[] = {
  	"January", "February", "March", "April", "May", "June", "July",
! 	"August", "September", "October", "November", "December",
  };

! static char *_add();
! static char *_conv();
! static char *_fmt();

  size_t
  strftime(s, maxsize, format, t)
  	char *s;
  	size_t maxsize;
! 	char *format;
! 	struct tm *t;
  {
  	size_t gsize;

--- 26,65 ----
   */

  #if defined(LIBC_SCCS) && !defined(lint)
! static const char sccsid[] = "@(#)strftime.c	5.4 (Berkeley) 3/14/89";
  #endif /* LIBC_SCCS and not lint */

! #include "private.h"
  #include "tzfile.h"

! static const char * const afmt[] = {
! 	"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  };
! static const char * const Afmt[] = {
  	"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
! 	"Saturday"
  };
! static const char * const bfmt[] = {
  	"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep",
! 	"Oct", "Nov", "Dec"
  };
! static const char * const Bfmt[] = {
  	"January", "February", "March", "April", "May", "June", "July",
! 	"August", "September", "October", "November", "December"
  };

! static char *_add P((const char *, size_t *, char *));
! static char *_conv P((int, const char *, size_t *, char *));
! static char *_fmt P((const char *, const struct tm *, size_t *, char *));

+ size_t strftime P((char *, size_t, const char *, const struct tm *));
+ 
  size_t
  strftime(s, maxsize, format, t)
  	char *s;
  	size_t maxsize;
! 	const char *format;
! 	const struct tm *t;
  {
  	size_t gsize;

***************
*** 72,79 ****

  static char *
  _fmt(format, t, gsizep, pt)
! 	char *format;
! 	struct tm *t;
  	size_t *gsizep;
  	char *pt;
  {
--- 73,80 ----

  static char *
  _fmt(format, t, gsizep, pt)
! 	const char *format;
! 	const struct tm *t;
  	size_t *gsizep;
  	char *pt;
  {
***************
*** 113,119 ****
  				** (ado, 5/24/93)
  				*/
  				pt = _conv((t->tm_year + TM_YEAR_BASE) / 100,
! 					2, '0', gsizep, pt);
  				continue;
  			case 'D':
  			case 'x':
--- 114,120 ----
  				** (ado, 5/24/93)
  				*/
  				pt = _conv((t->tm_year + TM_YEAR_BASE) / 100,
! 					"%02d", gsizep, pt);
  				continue;
  			case 'D':
  			case 'x':
***************
*** 126,137 ****
  				** standard calls for "date, using locale's
  				** date format," anything goes.  Using just
  				** numbers (as here) makes Quakers happier.
! 				** (ado, 5/24/93)
  				*/
! 				pt = _fmt("%m/%d/%y", t, gsizep, pt);
  				continue;
  			case 'd':
! 				pt = _conv(t->tm_mday, 2, '0', gsizep, pt);
  				continue;
  			case 'E':
  			case 'O':
--- 127,138 ----
  				** standard calls for "date, using locale's
  				** date format," anything goes.  Using just
  				** numbers (as here) makes Quakers happier.
! 				** This is the ISO standard date format.
  				*/
! 				pt = _fmt("%Y-%m-%d", t, gsizep, pt);
  				continue;
  			case 'd':
! 				pt = _conv(t->tm_mday, "%02d", gsizep, pt);
  				continue;
  			case 'E':
  			case 'O':
***************
*** 148,165 ****
  				*/
  				goto label;
  			case 'e':
! 				pt = _conv(t->tm_mday, 2, ' ', gsizep, pt);
  				continue;
  			case 'H':
! 				pt = _conv(t->tm_hour, 2, '0', gsizep, pt);
  				continue;
  			case 'I':
  				pt = _conv((t->tm_hour % 12) ?
  					(t->tm_hour % 12) : 12,
! 					2, '0', gsizep, pt);
  				continue;
  			case 'j':
! 				pt = _conv(t->tm_yday + 1, 3, '0', gsizep, pt);
  				continue;
  			case 'k':
  				/*
--- 149,166 ----
  				*/
  				goto label;
  			case 'e':
! 				pt = _conv(t->tm_mday, "%2d", gsizep, pt);
  				continue;
  			case 'H':
! 				pt = _conv(t->tm_hour, "%02d", gsizep, pt);
  				continue;
  			case 'I':
  				pt = _conv((t->tm_hour % 12) ?
  					(t->tm_hour % 12) : 12,
! 					"%02d", gsizep, pt);
  				continue;
  			case 'j':
! 				pt = _conv(t->tm_yday + 1, "%03d", gsizep, pt);
  				continue;
  			case 'k':
  				/*
***************
*** 172,178 ****
  				** "%l" have been swapped.
  				** (ado, 5/24/93)
  				*/
! 				pt = _conv(t->tm_hour, 2, ' ', gsizep, pt);
  				continue;
  #ifdef KITCHEN_SINK
  			case 'K':
--- 173,179 ----
  				** "%l" have been swapped.
  				** (ado, 5/24/93)
  				*/
! 				pt = _conv(t->tm_hour, "%2d", gsizep, pt);
  				continue;
  #ifdef KITCHEN_SINK
  			case 'K':
***************
*** 194,206 ****
  				*/
  				pt = _conv((t->tm_hour % 12) ?
  					(t->tm_hour % 12) : 12,
! 					2, ' ', gsizep, pt);
  				continue;
  			case 'M':
! 				pt = _conv(t->tm_min, 2, '0', gsizep, pt);
  				continue;
  			case 'm':
! 				pt = _conv(t->tm_mon + 1, 2, '0', gsizep, pt);
  				continue;
  			case 'n':
  				pt = _add("\n", gsizep, pt);
--- 195,207 ----
  				*/
  				pt = _conv((t->tm_hour % 12) ?
  					(t->tm_hour % 12) : 12,
! 					"%2d", gsizep, pt);
  				continue;
  			case 'M':
! 				pt = _conv(t->tm_min, "%02d", gsizep, pt);
  				continue;
  			case 'm':
! 				pt = _conv(t->tm_mon + 1, "%02d", gsizep, pt);
  				continue;
  			case 'n':
  				pt = _add("\n", gsizep, pt);
***************
*** 216,222 ****
  				pt = _fmt("%I:%M:%S %p", t, gsizep, pt);
  				continue;
  			case 'S':
! 				pt = _conv(t->tm_sec, 2, '0', gsizep, pt);
  				continue;
  			case 'T':
  			case 'X':
--- 217,223 ----
  				pt = _fmt("%I:%M:%S %p", t, gsizep, pt);
  				continue;
  			case 'S':
! 				pt = _conv(t->tm_sec, "%02d", gsizep, pt);
  				continue;
  			case 'T':
  			case 'X':
***************
*** 227,233 ****
  				continue;
  			case 'U':
  				pt = _conv((t->tm_yday + 7 - t->tm_wday) / 7,
! 					2, '0', gsizep, pt);
  				continue;
  			case 'u':
  				/*
--- 228,234 ----
  				continue;
  			case 'U':
  				pt = _conv((t->tm_yday + 7 - t->tm_wday) / 7,
! 					"%02d", gsizep, pt);
  				continue;
  			case 'u':
  				/*
***************
*** 237,243 ****
  				** (ado, 5/24/93)
  				*/
  				pt = _conv((t->tm_wday == 0) ? 7 : t->tm_wday,
! 					1, '0', gsizep, pt);
  				continue;
  			case 'V':
  				/*
--- 238,244 ----
  				** (ado, 5/24/93)
  				*/
  				pt = _conv((t->tm_wday == 0) ? 7 : t->tm_wday,
! 					"%d", gsizep, pt);
  				continue;
  			case 'V':
  				/*
***************
*** 260,266 ****
  				** 1 falls on a Thursday, are December 29-31
  				** of the PREVIOUS year part of week 1???
  				** (ado 5/24/93)
! 				/*
  				** You are understood not to expect this.
  				*/
  				{
--- 261,267 ----
  				** 1 falls on a Thursday, are December 29-31
  				** of the PREVIOUS year part of week 1???
  				** (ado 5/24/93)
! 				**
  				** You are understood not to expect this.
  				*/
  				{
***************
*** 269,275 ****
  					i = (t->tm_yday + 10 - (t->tm_wday ?
  						(t->tm_wday - 1) : 6)) / 7;
  					pt = _conv((i == 0) ? 53 : i,
! 						2, '0', gsizep, pt);
  				}
  				continue;
  			case 'v':
--- 270,276 ----
  					i = (t->tm_yday + 10 - (t->tm_wday ?
  						(t->tm_wday - 1) : 6)) / 7;
  					pt = _conv((i == 0) ? 53 : i,
! 						"%02d", gsizep, pt);
  				}
  				continue;
  			case 'v':
***************
*** 284,300 ****
  				pt = _conv((t->tm_yday + 7 -
  					(t->tm_wday ?
  					(t->tm_wday - 1) : 6)) / 7,
! 					2, '0', gsizep, pt);
  				continue;
  			case 'w':
! 				pt = _conv(t->tm_wday, 1, '0', gsizep, pt);
  				continue;
  			case 'y':
  				pt = _conv((t->tm_year + TM_YEAR_BASE) % 100,
! 					2, '0', gsizep, pt);
  				continue;
  			case 'Y':
! 				pt = _conv(t->tm_year + TM_YEAR_BASE, 4, '0',
  					gsizep, pt);
  				continue;
  			case 'Z':
--- 285,301 ----
  				pt = _conv((t->tm_yday + 7 -
  					(t->tm_wday ?
  					(t->tm_wday - 1) : 6)) / 7,
! 					"%02d", gsizep, pt);
  				continue;
  			case 'w':
! 				pt = _conv(t->tm_wday, "%d", gsizep, pt);
  				continue;
  			case 'y':
  				pt = _conv((t->tm_year + TM_YEAR_BASE) % 100,
! 					"%02d", gsizep, pt);
  				continue;
  			case 'Y':
! 				pt = _conv(t->tm_year + TM_YEAR_BASE, "%04d",
  					gsizep, pt);
  				continue;
  			case 'Z':
***************
*** 329,356 ****
  }

  static char *
! _conv(n, width, fill, gsizep, pt)
! 	int n, width, fill;
  	size_t *gsizep;
  	char *pt;
  {
! 	char *p, *q, buf[12];
! 	static char digits[] = "0123456789";

! 	p = buf + sizeof buf;
! 	q = (width >= sizeof buf) ? buf : (p - width - 1);
! 	*--p = '\0';
! 	*--p = digits[n % 10];
! 	while (p > buf && (n /= 10) != 0)
! 		*--p = digits[n % 10];
! 	while (p > q)
! 		*--p = fill;
! 	return _add(p, gsizep, pt);
  }

  static char *
  _add(str, gsizep, pt)
! 	char *str;
  	size_t *gsizep;
  	char *pt;
  {
--- 330,350 ----
  }

  static char *
! _conv(n, format, gsizep, pt)
! 	int n;
! 	const char *format;
  	size_t *gsizep;
  	char *pt;
  {
! 	char buf[21]; /* Room for - 2**63 ("-9223372036854775808") + null.  */

! 	(void) sprintf(buf, format, n);
! 	return _add(buf, gsizep, pt);
  }

  static char *
  _add(str, gsizep, pt)
! 	const char *str;
  	size_t *gsizep;
  	char *pt;
  {

proposed changes to strftime.c

eggert＠twinsun.com