coreutils/lib/posixtm.y

/* Parse dates for touch.
   Copyright (C) 1989, 1990, 1991 Free Software Foundation Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* Written by Jim Kingdon and David MacKenzie. */
%{
#ifdef __GNUC__
#define alloca __builtin_alloca
#else
#ifdef sparc
#include <alloca.h>
#else
#ifdef _AIX
 #pragma alloca
#else
char *alloca ();
#endif
#endif
#endif

#include <stdio.h>
#include <sys/types.h>
#include <time.h>

#define YYDEBUG 1

/* Lexical analyzer's current scan position in the input string. */
static char *curpos;

/* The return value. */
static struct tm t;

time_t mktime ();

#define yyparse posixtime_yyparse
static int yylex ();
static int yyerror ();
%}

%token DIGIT

%%
date :
       digitpair /* month */
       digitpair /* day */
       digitpair /* hours */
       digitpair /* minutes */
       year
       seconds {
	         if ($1 >= 1 && $1 <= 12)
		   t.tm_mon = $1 - 1;
		 else {
		   YYABORT;
		 }
		 if ($2 >= 1 && $2 <= 31)
		   t.tm_mday = $2;
		 else {
		   YYABORT;
		 }
		 if ($3 >= 0 && $3 <= 23)
		   t.tm_hour = $3;
		 else {
		   YYABORT;
		 }
		 if ($4 >= 0 && $4 <= 59)
		   t.tm_min = $4;
		 else {
		   YYABORT;
		 }
	       }

year : digitpair {
                   t.tm_year = $1;
		   /* Deduce the century based on the year.
		      See POSIX.2 section 4.63.3.  */
		   if ($1 <= 68)
		     t.tm_year += 100;
		 }
    | digitpair digitpair {
                            t.tm_year = $1 * 100 + $2;
			    if (t.tm_year < 1900) {
			      YYABORT;
			    } else
			      t.tm_year -= 1900;
			  }
    | /* empty */ {
                    time_t now;
		    struct tm *tmp;

                    /* Use current year.  */
                    time (&now);
		    tmp = localtime (&now);
		    t.tm_year = tmp->tm_year;
		  }
    ;

seconds : /* empty */ {
                        t.tm_sec = 0;
		      }
        | '.' digitpair {
	                  if ($2 >= 0 && $2 <= 61)
			    t.tm_sec = $2;
			  else {
			    YYABORT;
			  }
			}
        ;

digitpair : DIGIT DIGIT {
                          $$ = $1 * 10 + $2;
			}
          ;
%%
static int
yylex ()
{
  char ch = *curpos++;

  if (ch >= '0' && ch <= '9')
    {
      yylval = ch - '0';
      return DIGIT;
    }
  else if (ch == '.' || ch == 0)
    return ch;
  else
    return '?';			/* Cause an error.  */
}

static int
yyerror ()
{
  return 0;
}

/* Parse a POSIX-style date and return it, or (time_t)-1 for an error.  */

time_t
posixtime (s)
     char *s;
{
  curpos = s;
  /* Let mktime decide whether it is daylight savings time.  */
  t.tm_isdst = -1;
  if (yyparse ())
    return (time_t)-1;
  else
    return mktime (&t);
}

/* Parse a POSIX-style date and return it, or NULL for an error.  */

struct tm *
posixtm (s)
     char *s;
{
  if (posixtime (s) == -1)
    return NULL;
  return &t;
}