Handle two-digit years with leading zeros correctly.

[chaz/tar] / lib / getdate.y

%{
/* Parse a string into an internal time stamp.
   Copyright 1999, 2000 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Originally written by Steven M. Bellovin <smb@research.att.com> while
   at the University of North Carolina at Chapel Hill.  Later tweaked by
   a couple of people on Usenet.  Completely overhauled by Rich $alz
   <rsalz@bbn.com> and Jim Berets <jberets@bbn.com> in August, 1990.

   Modified by Paul Eggert <eggert@twinsun.com> in August 1999 to do
   the right thing about local DST.  Unlike previous versions, this
   version is reentrant.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
# ifdef HAVE_ALLOCA_H
#  include <alloca.h>
# endif
#endif

/* Since the code of getdate.y is not included in the Emacs executable
   itself, there is no need to #define static in this file.  Even if
   the code were included in the Emacs executable, it probably
   wouldn't do any harm to #undef it here; this will only cause
   problems if we try to write to a static variable, which I don't
   think this code needs to do.  */
#ifdef emacs
# undef static
#endif

#include <ctype.h>

#if HAVE_STDLIB_H
# include <stdlib.h> /* for `free'; used by Bison 1.27 */
#endif

#if STDC_HEADERS || (! defined isascii && ! HAVE_ISASCII)
# define IN_CTYPE_DOMAIN(c) 1
#else
# define IN_CTYPE_DOMAIN(c) isascii (c)
#endif

#define ISSPACE(c) (IN_CTYPE_DOMAIN (c) && isspace (c))
#define ISALPHA(c) (IN_CTYPE_DOMAIN (c) && isalpha (c))
#define ISLOWER(c) (IN_CTYPE_DOMAIN (c) && islower (c))
#define ISDIGIT_LOCALE(c) (IN_CTYPE_DOMAIN (c) && isdigit (c))

/* ISDIGIT differs from ISDIGIT_LOCALE, as follows:
   - Its arg may be any int or unsigned int; it need not be an unsigned char.
   - It's guaranteed to evaluate its argument exactly once.
   - It's typically faster.
   Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
   only '0' through '9' are digits.  Prefer ISDIGIT to ISDIGIT_LOCALE unless
   it's important to use the locale's definition of `digit' even when the
   host does not conform to Posix.  */
#define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)

#if STDC_HEADERS || HAVE_STRING_H
# include <string.h>
#endif

#if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8) || __STRICT_ANSI__
# define __attribute__(x)
#endif

#ifndef ATTRIBUTE_UNUSED
# define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
#endif

#define EPOCH_YEAR 1970
#define TM_YEAR_BASE 1900

#define HOUR(x) ((x) * 60)
 
/* An integer value, and the number of digits in its textual
   representation.  */
typedef struct
{
  int value;
  int digits;
} textint;

/* An entry in the lexical lookup table.  */
typedef struct
{
  char const *name;
  int type;
  int value;
} table;

/* Meridian: am, pm, or 24-hour style.  */
enum { MERam, MERpm, MER24 };

/* Information passed to and from the parser.  */
typedef struct
{
  /* The input string remaining to be parsed. */
  const char *input;

  /* N, if this is the Nth Tuesday.  */
  int day_ordinal;

  /* Day of week; Sunday is 0.  */
  int day_number;

  /* tm_isdst flag for the local zone.  */
  int local_isdst;

  /* Time zone, in minutes east of UTC.  */
  int time_zone;

  /* Style used for time.  */
  int meridian;

  /* Gregorian year, month, day, hour, minutes, and seconds.  */
  textint year;
  int month;
  int day;
  int hour;
  int minutes;
  int seconds;

  /* Relative year, month, day, hour, minutes, and seconds.  */
  int rel_year;
  int rel_month;
  int rel_day;
  int rel_hour;
  int rel_minutes;
  int rel_seconds;

  /* Counts of nonterminals of various flavors parsed so far.  */
  int dates_seen;
  int days_seen;
  int local_zones_seen;
  int rels_seen;
  int times_seen;
  int zones_seen;

  /* Table of local time zone abbrevations, terminated by a null entry.  */
  table local_time_zone_table[3];
} parser_control;

#define PC (* (parser_control *) parm)
#define YYLEX_PARAM parm
#define YYPARSE_PARAM parm

static int yyerror ();
static int yylex ();

%}

/* We want a reentrant parser.  */
%pure_parser

/* This grammar has 13 shift/reduce conflicts. */
%expect 13
 
%union
{
  int intval;
  textint textintval;
}

%token tAGO tDST

%token <intval> tDAY tDAY_UNIT tDAYZONE tHOUR_UNIT tLOCAL_ZONE tMERIDIAN
%token <intval> tMINUTE_UNIT tMONTH tMONTH_UNIT tSEC_UNIT tYEAR_UNIT tZONE

%token <textintval> tSNUMBER tUNUMBER

%type <intval> o_merid

%%

spec:
    /* empty */
  | spec item
  ;

item:
    time
      { PC.times_seen++; }
  | local_zone
      { PC.local_zones_seen++; }
  | zone
      { PC.zones_seen++; }
  | date
      { PC.dates_seen++; }
  | day
      { PC.days_seen++; }
  | rel
      { PC.rels_seen++; }
  | number
  ;

time:
    tUNUMBER tMERIDIAN
      {
        PC.hour = $1.value;
        PC.minutes = 0;
        PC.seconds = 0;
        PC.meridian = $2;
      }
  | tUNUMBER ':' tUNUMBER o_merid
      {
        PC.hour = $1.value;
        PC.minutes = $3.value;
        PC.seconds = 0;
        PC.meridian = $4;
      }
  | tUNUMBER ':' tUNUMBER tSNUMBER
      {
        PC.hour = $1.value;
        PC.minutes = $3.value;
        PC.meridian = MER24;
        PC.zones_seen++;
        PC.time_zone = $4.value % 100 + ($4.value / 100) * 60;
      }
  | tUNUMBER ':' tUNUMBER ':' tUNUMBER o_merid
      {
        PC.hour = $1.value;
        PC.minutes = $3.value;
        PC.seconds = $5.value;
        PC.meridian = $6;
      }
  | tUNUMBER ':' tUNUMBER ':' tUNUMBER tSNUMBER
      {
        PC.hour = $1.value;
        PC.minutes = $3.value;
        PC.seconds = $5.value;
        PC.meridian = MER24;
        PC.zones_seen++;
        PC.time_zone = $6.value % 100 + ($6.value / 100) * 60;
      }
  ;

local_zone:
    tLOCAL_ZONE
      { PC.local_isdst = $1; }
  | tLOCAL_ZONE tDST
      { PC.local_isdst = $1 < 0 ? 1 : $1 + 1; }
  ;

zone:
    tZONE
      { PC.time_zone = $1; }
  | tDAYZONE
      { PC.time_zone = $1 + 60; }
  | tZONE tDST
      { PC.time_zone = $1 + 60; }
  ;

day:
    tDAY
      {
        PC.day_ordinal = 1;
        PC.day_number = $1;
      }
  | tDAY ','
      {
        PC.day_ordinal = 1;
        PC.day_number = $1;
      }
  | tUNUMBER tDAY
      {
        PC.day_ordinal = $1.value;
        PC.day_number = $2;
      }
  ;

date:
    tUNUMBER '/' tUNUMBER
      {
        PC.month = $1.value;
        PC.day = $3.value;
      }
  | tUNUMBER '/' tUNUMBER '/' tUNUMBER
      {
        /* Interpret as YYYY/MM/DD if the first value has 4 or more digits,
           otherwise as MM/DD/YY.
           The goal in recognizing YYYY/MM/DD is solely to support legacy
           machine-generated dates like those in an RCS log listing.  If
           you want portability, use the ISO 8601 format.  */
        if (4 <= $1.digits)
          {
            PC.year = $1;
            PC.month = $3.value;
            PC.day = $5.value;
          }
        else
          {
            PC.month = $1.value;
            PC.day = $3.value;
            PC.year = $5;
          }
      }
  | tUNUMBER tSNUMBER tSNUMBER
      {
        /* ISO 8601 format.  YYYY-MM-DD.  */
        PC.year = $1;
        PC.month = -$2.value;
        PC.day = -$3.value;
      }
  | tUNUMBER tMONTH tSNUMBER
      {
        /* e.g. 17-JUN-1992.  */
        PC.day = $1.value;
        PC.month = $2;
        PC.year.value = -$3.value;
        PC.year.digits = $3.digits;
      }
  | tMONTH tUNUMBER
      {
        PC.month = $1;
        PC.day = $2.value;
      }
  | tMONTH tUNUMBER ',' tUNUMBER
      {
        PC.month = $1;
        PC.day = $2.value;
        PC.year = $4;
      }
  | tUNUMBER tMONTH
      {
        PC.day = $1.value;
        PC.month = $2;
      }
  | tUNUMBER tMONTH tUNUMBER
      {
        PC.day = $1.value;
        PC.month = $2;
        PC.year = $3;
      }
  ;

rel:
    relunit tAGO
      {
        PC.rel_seconds = -PC.rel_seconds;
        PC.rel_minutes = -PC.rel_minutes;
        PC.rel_hour = -PC.rel_hour;
        PC.rel_day = -PC.rel_day;
        PC.rel_month = -PC.rel_month;
        PC.rel_year = -PC.rel_year;
      }
  | relunit
  ;

relunit:
    tUNUMBER tYEAR_UNIT
      { PC.rel_year += $1.value * $2; }
  | tSNUMBER tYEAR_UNIT
      { PC.rel_year += $1.value * $2; }
  | tYEAR_UNIT
      { PC.rel_year += $1; }
  | tUNUMBER tMONTH_UNIT
      { PC.rel_month += $1.value * $2; }
  | tSNUMBER tMONTH_UNIT
      { PC.rel_month += $1.value * $2; }
  | tMONTH_UNIT
      { PC.rel_month += $1; }
  | tUNUMBER tDAY_UNIT
      { PC.rel_day += $1.value * $2; }
  | tSNUMBER tDAY_UNIT
      { PC.rel_day += $1.value * $2; }
  | tDAY_UNIT
      { PC.rel_day += $1 }
  | tUNUMBER tHOUR_UNIT
      { PC.rel_hour += $1.value * $2; }
  | tSNUMBER tHOUR_UNIT
      { PC.rel_hour += $1.value * $2; }
  | tHOUR_UNIT
      { PC.rel_hour += $1 }
  | tUNUMBER tMINUTE_UNIT
      { PC.rel_minutes += $1.value * $2; }
  | tSNUMBER tMINUTE_UNIT
      { PC.rel_minutes += $1.value * $2; }
  | tMINUTE_UNIT
      { PC.rel_minutes += $1 }
  | tUNUMBER tSEC_UNIT
      { PC.rel_seconds += $1.value * $2; }
  | tSNUMBER tSEC_UNIT
      { PC.rel_seconds += $1.value * $2; }
  | tSEC_UNIT
      { PC.rel_seconds += $1; }
  ;

number:
    tUNUMBER
      {
        if (PC.dates_seen
            && ! PC.rels_seen && (PC.times_seen || 2 < $1.digits))
          PC.year = $1;
        else
          {
            if (4 < $1.digits)
              {
                PC.dates_seen++;
                PC.day = $1.value % 100;
                PC.month = ($1.value / 100) % 100;
                PC.year.value = $1.value / 10000;
                PC.year.digits = $1.digits - 4;
              }
            else
              {
                PC.times_seen++;
                if ($1.digits <= 2)
                  {
                    PC.hour = $1.value;
                    PC.minutes = 0;
                  }
                else
                  {
                    PC.hour = $1.value / 100;
                    PC.minutes = $1.value % 100;
                  }
                PC.seconds = 0;
                PC.meridian = MER24;
              }
          }
      }
  ;

o_merid:
    /* empty */
      { $$ = MER24; }
  | tMERIDIAN
      { $$ = $1; }
  ;

%%

/* Include this file down here because bison inserts code above which
   may define-away `const'.  We want the prototype for get_date to have
   the same signature as the function definition.  */
#include "getdate.h"

#ifndef gmtime
struct tm *gmtime ();
#endif
#ifndef localtime
struct tm *localtime ();
#endif
#ifndef mktime
time_t mktime ();
#endif

static table const meridian_table[] =
{
  { "AM",   tMERIDIAN, MERam },
  { "A.M.", tMERIDIAN, MERam },
  { "PM",   tMERIDIAN, MERpm },
  { "P.M.", tMERIDIAN, MERpm },
  { 0, 0, 0 }
};

static table const dst_table[] =
{
  { "DST", tDST, 0 }
};

static table const month_and_day_table[] =
{
  { "JANUARY",  tMONTH,  1 },
  { "FEBRUARY", tMONTH,  2 },
  { "MARCH",    tMONTH,  3 },
  { "APRIL",    tMONTH,  4 },
  { "MAY",      tMONTH,  5 },
  { "JUNE",     tMONTH,  6 },
  { "JULY",     tMONTH,  7 },
  { "AUGUST",   tMONTH,  8 },
  { "SEPTEMBER",tMONTH,  9 },
  { "SEPT",     tMONTH,  9 },
  { "OCTOBER",  tMONTH, 10 },
  { "NOVEMBER", tMONTH, 11 },
  { "DECEMBER", tMONTH, 12 },
  { "SUNDAY",   tDAY,    0 },
  { "MONDAY",   tDAY,    1 },
  { "TUESDAY",  tDAY,    2 },
  { "TUES",     tDAY,    2 },
  { "WEDNESDAY",tDAY,    3 },
  { "WEDNES",   tDAY,    3 },
  { "THURSDAY", tDAY,    4 },
  { "THUR",     tDAY,    4 },
  { "THURS",    tDAY,    4 },
  { "FRIDAY",   tDAY,    5 },
  { "SATURDAY", tDAY,    6 },
  { 0, 0, 0 }
};

static table const time_units_table[] =
{
  { "YEAR",     tYEAR_UNIT,      1 },
  { "MONTH",    tMONTH_UNIT,     1 },
  { "FORTNIGHT",tDAY_UNIT,      14 },
  { "WEEK",     tDAY_UNIT,       7 },
  { "DAY",      tDAY_UNIT,       1 },
  { "HOUR",     tHOUR_UNIT,      1 },
  { "MINUTE",   tMINUTE_UNIT,    1 },
  { "MIN",      tMINUTE_UNIT,    1 },
  { "SECOND",   tSEC_UNIT,       1 },
  { "SEC",      tSEC_UNIT,       1 },
  { 0, 0, 0 }
};

/* Assorted relative-time words. */
static table const relative_time_table[] =
{
  { "TOMORROW", tMINUTE_UNIT,   24 * 60 },
  { "YESTERDAY",tMINUTE_UNIT,   - (24 * 60) },
  { "TODAY",    tMINUTE_UNIT,    0 },
  { "NOW",      tMINUTE_UNIT,    0 },
  { "LAST",     tUNUMBER,       -1 },
  { "THIS",     tUNUMBER,        0 },
  { "NEXT",     tUNUMBER,        1 },
  { "FIRST",    tUNUMBER,        1 },
/*{ "SECOND",   tUNUMBER,        2 }, */
  { "THIRD",    tUNUMBER,        3 },
  { "FOURTH",   tUNUMBER,        4 },
  { "FIFTH",    tUNUMBER,        5 },
  { "SIXTH",    tUNUMBER,        6 },
  { "SEVENTH",  tUNUMBER,        7 },
  { "EIGHTH",   tUNUMBER,        8 },
  { "NINTH",    tUNUMBER,        9 },
  { "TENTH",    tUNUMBER,       10 },
  { "ELEVENTH", tUNUMBER,       11 },
  { "TWELFTH",  tUNUMBER,       12 },
  { "AGO",      tAGO,            1 },
  { 0, 0, 0 }
};

/* The time zone table.  This table is necessarily incomplete, as time
   zone abbreviations are ambiguous; e.g. Australians interpret "EST"
   as Eastern time in Australia, not as US Eastern Standard Time.
   You cannot rely on getdate to handle arbitrary time zone
   abbreviations; use numeric abbreviations like `-0500' instead.  */
static table const time_zone_table[] =
{
  { "GMT",      tZONE,     HOUR ( 0) }, /* Greenwich Mean */
  { "UT",       tZONE,     HOUR ( 0) }, /* Universal (Coordinated) */
  { "UTC",      tZONE,     HOUR ( 0) },
  { "WET",      tZONE,     HOUR ( 0) }, /* Western European */
  { "WEST",     tDAYZONE,  HOUR ( 0) }, /* Western European Summer */
  { "BST",      tDAYZONE,  HOUR ( 0) }, /* British Summer */
  { "ART",      tZONE,    -HOUR ( 3) }, /* Argentina */
  { "BRT",      tZONE,    -HOUR ( 3) }, /* Brazil */
  { "BRST",     tDAYZONE, -HOUR ( 3) }, /* Brazil Summer */
  { "NST",      tZONE,   -(HOUR ( 3) + 30) },   /* Newfoundland Standard */
  { "NDT",      tDAYZONE,-(HOUR ( 3) + 30) },   /* Newfoundland Daylight */
  { "AST",      tZONE,    -HOUR ( 4) }, /* Atlantic Standard */
  { "ADT",      tDAYZONE, -HOUR ( 4) }, /* Atlantic Daylight */
  { "CLT",      tZONE,    -HOUR ( 4) }, /* Chile */
  { "CLST",     tDAYZONE, -HOUR ( 4) }, /* Chile Summer */
  { "EST",      tZONE,    -HOUR ( 5) }, /* Eastern Standard */
  { "EDT",      tDAYZONE, -HOUR ( 5) }, /* Eastern Daylight */
  { "CST",      tZONE,    -HOUR ( 6) }, /* Central Standard */
  { "CDT",      tDAYZONE, -HOUR ( 6) }, /* Central Daylight */
  { "MST",      tZONE,    -HOUR ( 7) }, /* Mountain Standard */
  { "MDT",      tDAYZONE, -HOUR ( 7) }, /* Mountain Daylight */
  { "PST",      tZONE,    -HOUR ( 8) }, /* Pacific Standard */
  { "PDT",      tDAYZONE, -HOUR ( 8) }, /* Pacific Daylight */
  { "AKST",     tZONE,    -HOUR ( 9) }, /* Alaska Standard */
  { "AKDT",     tDAYZONE, -HOUR ( 9) }, /* Alaska Daylight */
  { "HST",      tZONE,    -HOUR (10) }, /* Hawaii Standard */
  { "HAST",     tZONE,    -HOUR (10) }, /* Hawaii-Aleutian Standard */
  { "HADT",     tDAYZONE, -HOUR (10) }, /* Hawaii-Aleutian Daylight */
  { "SST",      tZONE,    -HOUR (12) }, /* Samoa Standard */
  { "WAT",      tZONE,     HOUR ( 1) }, /* West Africa */
  { "CET",      tZONE,     HOUR ( 1) }, /* Central European */
  { "CEST",     tDAYZONE,  HOUR ( 1) }, /* Central European Summer */
  { "MET",      tZONE,     HOUR ( 1) }, /* Middle European */
  { "MEZ",      tZONE,     HOUR ( 1) }, /* Middle European */
  { "MEST",     tDAYZONE,  HOUR ( 1) }, /* Middle European Summer */
  { "MESZ",     tDAYZONE,  HOUR ( 1) }, /* Middle European Summer */
  { "EET",      tZONE,     HOUR ( 2) }, /* Eastern European */
  { "EEST",     tDAYZONE,  HOUR ( 2) }, /* Eastern European Summer */
  { "CAT",      tZONE,     HOUR ( 2) }, /* Central Africa */
  { "SAST",     tZONE,     HOUR ( 2) }, /* South Africa Standard */
  { "EAT",      tZONE,     HOUR ( 3) }, /* East Africa */
  { "MSK",      tZONE,     HOUR ( 3) }, /* Moscow */
  { "MSD",      tDAYZONE,  HOUR ( 3) }, /* Moscow Daylight */
  { "IST",      tZONE,    (HOUR ( 5) + 30) },   /* India Standard */
  { "SGT",      tZONE,     HOUR ( 8) }, /* Singapore */
  { "KST",      tZONE,     HOUR ( 9) }, /* Korea Standard */
  { "JST",      tZONE,     HOUR ( 9) }, /* Japan Standard */
  { "GST",      tZONE,     HOUR (10) }, /* Guam Standard */
  { "NZST",     tZONE,     HOUR (12) }, /* New Zealand Standard */
  { "NZDT",     tDAYZONE,  HOUR (12) }, /* New Zealand Daylight */
  { 0, 0, 0  }
};

/* Military time zone table. */
static table const military_table[] =
{
  { "A", tZONE, -HOUR ( 1) },
  { "B", tZONE, -HOUR ( 2) },
  { "C", tZONE, -HOUR ( 3) },
  { "D", tZONE, -HOUR ( 4) },
  { "E", tZONE, -HOUR ( 5) },
  { "F", tZONE, -HOUR ( 6) },
  { "G", tZONE, -HOUR ( 7) },
  { "H", tZONE, -HOUR ( 8) },
  { "I", tZONE, -HOUR ( 9) },
  { "K", tZONE, -HOUR (10) },
  { "L", tZONE, -HOUR (11) },
  { "M", tZONE, -HOUR (12) },
  { "N", tZONE,  HOUR ( 1) },
  { "O", tZONE,  HOUR ( 2) },
  { "P", tZONE,  HOUR ( 3) },
  { "Q", tZONE,  HOUR ( 4) },
  { "R", tZONE,  HOUR ( 5) },
  { "S", tZONE,  HOUR ( 6) },
  { "T", tZONE,  HOUR ( 7) },
  { "U", tZONE,  HOUR ( 8) },
  { "V", tZONE,  HOUR ( 9) },
  { "W", tZONE,  HOUR (10) },
  { "X", tZONE,  HOUR (11) },
  { "Y", tZONE,  HOUR (12) },
  { "Z", tZONE,  HOUR ( 0) },
  { 0, 0, 0 }
};

\f

static int
to_hour (int hours, int meridian)
{
  switch (meridian)
    {
    case MER24:
      return 0 <= hours && hours < 24 ? hours : -1;
    case MERam:
      return 0 < hours && hours < 12 ? hours : hours == 12 ? 0 : -1;
    case MERpm:
      return 0 < hours && hours < 12 ? hours + 12 : hours == 12 ? 12 : -1;
    default:
      abort ();
    }
  /* NOTREACHED */
}

static int
to_year (textint textyear)
{
  int year = textyear.value;

  if (year < 0)
    year = -year;

  /* XPG4 suggests that years 00-68 map to 2000-2068, and
     years 69-99 map to 1969-1999.  */
  if (textyear.digits == 2)
    year += year < 69 ? 2000 : 1900;

  return year;
}

static table const *
lookup_zone (parser_control const *pc, char const *name)
{
  table const *tp;

  /* Try local zone abbreviations first; they're more likely to be right.  */
  for (tp = pc->local_time_zone_table; tp->name; tp++)
    if (strcmp (name, tp->name) == 0)
      return tp;

  for (tp = time_zone_table; tp->name; tp++)
    if (strcmp (name, tp->name) == 0)
      return tp;

  return 0;
}

#if ! HAVE_TM_GMTOFF
/* Yield the difference between *A and *B,
   measured in seconds, ignoring leap seconds.
   The body of this function is taken directly from the GNU C Library;
   see src/strftime.c.  */
static int
tm_diff (struct tm const *a, struct tm const *b)
{
  /* Compute intervening leap days correctly even if year is negative.
     Take care to avoid int overflow in leap day calculations,
     but it's OK to assume that A and B are close to each other.  */
  int a4 = (a->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (a->tm_year & 3);
  int b4 = (b->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (b->tm_year & 3);
  int a100 = a4 / 25 - (a4 % 25 < 0);
  int b100 = b4 / 25 - (b4 % 25 < 0);
  int a400 = a100 >> 2;
  int b400 = b100 >> 2;
  int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);
  int years = a->tm_year - b->tm_year;
  int days = (365 * years + intervening_leap_days
              + (a->tm_yday - b->tm_yday));
  return (60 * (60 * (24 * days + (a->tm_hour - b->tm_hour))
                + (a->tm_min - b->tm_min))
          + (a->tm_sec - b->tm_sec));
}
#endif /* ! HAVE_TM_GMTOFF */

static table const *
lookup_word (parser_control const *pc, char *word)
{
  char *p;
  char *q;
  size_t wordlen;
  table const *tp;
  int i;
  int abbrev;

  /* Make it uppercase.  */
  for (p = word; *p; p++)
    if (ISLOWER ((unsigned char) *p))
      *p = toupper ((unsigned char) *p);

  for (tp = meridian_table; tp->name; tp++)
    if (strcmp (word, tp->name) == 0)
      return tp;

  /* See if we have an abbreviation for a month. */
  wordlen = strlen (word);
  abbrev = wordlen == 3 || (wordlen == 4 && word[3] == '.');

  for (tp = month_and_day_table; tp->name; tp++)
    if ((abbrev ? strncmp (word, tp->name, 3) : strcmp (word, tp->name)) == 0)
      return tp;

  if ((tp = lookup_zone (pc, word)))
    return tp;

  if (strcmp (word, dst_table[0].name) == 0)
    return dst_table;

  for (tp = time_units_table; tp->name; tp++)
    if (strcmp (word, tp->name) == 0)
      return tp;

  /* Strip off any plural and try the units table again. */
  if (word[wordlen - 1] == 'S')
    {
      word[wordlen - 1] = '\0';
      for (tp = time_units_table; tp->name; tp++)
        if (strcmp (word, tp->name) == 0)
          return tp;
      word[wordlen - 1] = 'S';  /* For "this" in relative_time_table.  */
    }

  for (tp = relative_time_table; tp->name; tp++)
    if (strcmp (word, tp->name) == 0)
      return tp;

  /* Military time zones. */
  if (wordlen == 1)
    for (tp = military_table; tp->name; tp++)
      if (word[0] == tp->name[0])
        return tp;

  /* Drop out any periods and try the time zone table again. */
  for (i = 0, p = q = word; (*p = *q); q++)
    if (*q == '.')
      i = 1;
    else
      p++;
  if (i && (tp = lookup_zone (pc, word)))
    return tp;

  return 0;
}

static int
yylex (YYSTYPE *lvalp, parser_control *pc)
{
  unsigned char c;
  int count;

  for (;;)
    {
      while (c = *pc->input, ISSPACE (c))
        pc->input++;

      if (ISDIGIT (c) || c == '-' || c == '+')
        {
          char const *p;
          int sign;
          int value;
          if (c == '-' || c == '+')
            {
              sign = c == '-' ? -1 : 1;
              c = *++pc->input;
              if (! ISDIGIT (c))
                /* skip the '-' sign */
                continue;
            }
          else
            sign = 0;
          p = pc->input;
          value = 0;
          do
            {
              value = 10 * value + c - '0';
              c = *++p;
            }
          while (ISDIGIT (c));
          lvalp->textintval.value = sign < 0 ? -value : value;
          lvalp->textintval.digits = p - pc->input;
          pc->input = p;
          return sign ? tSNUMBER : tUNUMBER;
        }

      if (ISALPHA (c))
        {
          char buff[20];
          char *p = buff;
          table const *tp;

          do
            {
              if (p < buff + sizeof buff - 1)
                *p++ = c;
              c = *++pc->input;
            }
          while (ISALPHA (c) || c == '.');

          *p = '\0';
          tp = lookup_word (pc, buff);
          if (! tp)
            return '?';
          lvalp->intval = tp->value;
          return tp->type;
        }

      if (c != '(')
        return *pc->input++;
      count = 0;
      do
        {
          c = *pc->input++;
          if (c == '\0')
            return c;
          if (c == '(')
            count++;
          else if (c == ')')
            count--;
        }
      while (count > 0);
    }
}

/* Do nothing if the parser reports an error.  */
static int
yyerror (char *s ATTRIBUTE_UNUSED)
{
  return 0;
}

/* Parse a date/time string P.  Return the corresponding time_t value,
   or (time_t) -1 if there is an error.  P can be an incomplete or
   relative time specification; if so, use *NOW as the basis for the
   returned time.  */
time_t
get_date (const char *p, const time_t *now)
{
  time_t Start = now ? *now : time (0);
  struct tm *tmp = localtime (&Start);
  struct tm tm;
  struct tm tm0;
  parser_control pc;

  if (! tmp)
    return -1;

  pc.input = p;
  pc.year.value = tmp->tm_year + TM_YEAR_BASE;
  pc.year.digits = 4;
  pc.month = tmp->tm_mon + 1;
  pc.day = tmp->tm_mday;
  pc.hour = tmp->tm_hour;
  pc.minutes = tmp->tm_min;
  pc.seconds = tmp->tm_sec;
  tm.tm_isdst = tmp->tm_isdst;

  pc.meridian = MER24;
  pc.rel_seconds = 0;
  pc.rel_minutes = 0;
  pc.rel_hour = 0;
  pc.rel_day = 0;
  pc.rel_month = 0;
  pc.rel_year = 0;
  pc.dates_seen = 0;
  pc.days_seen = 0;
  pc.rels_seen = 0;
  pc.times_seen = 0;
  pc.local_zones_seen = 0;
  pc.zones_seen = 0;

#if HAVE_TM_ZONE
  pc.local_time_zone_table[0].name = tmp->tm_zone;
  pc.local_time_zone_table[0].type = tLOCAL_ZONE;
  pc.local_time_zone_table[0].value = tmp->tm_isdst;
  pc.local_time_zone_table[1].name = 0;

  /* Probe the names used in the next three calendar quarters, looking
     for a tm_isdst different from the one we already have.  */
  {
    int quarter;
    for (quarter = 1; quarter <= 3; quarter++)
      {
        time_t probe = Start + quarter * (90 * 24 * 60 * 60);
        struct tm *probe_tm = localtime (&probe);
        if (probe_tm && probe_tm->tm_zone
            && probe_tm->tm_isdst != pc.local_time_zone_table[0].value)
          {
              {
                pc.local_time_zone_table[1].name = probe_tm->tm_zone;
                pc.local_time_zone_table[1].type = tLOCAL_ZONE;
                pc.local_time_zone_table[1].value = probe_tm->tm_isdst;
                pc.local_time_zone_table[2].name = 0;
              }
            break;
          }
      }
  }
#else
#if HAVE_TZNAME
  {
# ifndef tzname
    extern char *tzname[];
# endif
    int i;
    for (i = 0; i < 2; i++)
      {
        pc.local_time_zone_table[i].name = tzname[i];
        pc.local_time_zone_table[i].type = tLOCAL_ZONE;
        pc.local_time_zone_table[i].value = i;
      }
    pc.local_time_zone_table[i].name = 0;
  }
#else
  pc.local_time_zone_table[0].name = 0;
#endif
#endif

  if (pc.local_time_zone_table[0].name && pc.local_time_zone_table[1].name
      && ! strcmp (pc.local_time_zone_table[0].name,
                   pc.local_time_zone_table[1].name))
    {
      /* This locale uses the same abbrevation for standard and
         daylight times.  So if we see that abbreviation, we don't
         know whether it's daylight time.  */
      pc.local_time_zone_table[0].value = -1;
      pc.local_time_zone_table[1].name = 0;
    }

  if (yyparse (&pc) != 0
      || 1 < pc.times_seen || 1 < pc.dates_seen || 1 < pc.days_seen
      || 1 < (pc.local_zones_seen + pc.zones_seen)
      || (pc.local_zones_seen && 1 < pc.local_isdst))
    return -1;

  tm.tm_year = to_year (pc.year) - TM_YEAR_BASE + pc.rel_year;
  tm.tm_mon = pc.month - 1 + pc.rel_month;
  tm.tm_mday = pc.day + pc.rel_day;
  if (pc.times_seen || (pc.rels_seen && ! pc.dates_seen && ! pc.days_seen))
    {
      tm.tm_hour = to_hour (pc.hour, pc.meridian);
      if (tm.tm_hour < 0)
        return -1;
      tm.tm_min = pc.minutes;
      tm.tm_sec = pc.seconds;
    }
  else
    {
      tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
    }
  tm.tm_hour += pc.rel_hour;
  tm.tm_min += pc.rel_minutes;
  tm.tm_sec += pc.rel_seconds;

  /* Let mktime deduce tm_isdst if we have an absolute time stamp,
     or if the relative time stamp mentions days, months, or years.  */
  if (pc.dates_seen | pc.days_seen | pc.times_seen | pc.rel_day | pc.rel_month | pc.rel_year)
    tm.tm_isdst = -1;

  /* But if the input explicitly specifies local time with or without
     DST, give mktime that information.  */
  if (pc.local_zones_seen)
    tm.tm_isdst = pc.local_isdst;

  tm0 = tm;

  Start = mktime (&tm);

  if (Start == (time_t) -1)
    {

      /* Guard against falsely reporting errors near the time_t boundaries
         when parsing times in other time zones.  For example, if the min
         time_t value is 1970-01-01 00:00:00 UTC and we are 8 hours ahead
         of UTC, then the min localtime value is 1970-01-01 08:00:00; if
         we apply mktime to 1970-01-01 00:00:00 we will get an error, so
         we apply mktime to 1970-01-02 08:00:00 instead and adjust the time
         zone by 24 hours to compensate.  This algorithm assumes that
         there is no DST transition within a day of the time_t boundaries.  */
      if (pc.zones_seen)
        {
          tm = tm0;
          if (tm.tm_year <= EPOCH_YEAR - TM_YEAR_BASE)
            {
              tm.tm_mday++;
              pc.time_zone += 24 * 60;
            }
          else
            {
              tm.tm_mday--;
              pc.time_zone -= 24 * 60;
            }
          Start = mktime (&tm);
        }

      if (Start == (time_t) -1)
        return Start;
    }

  if (pc.days_seen && ! pc.dates_seen)
    {
      tm.tm_mday += ((pc.day_number - tm.tm_wday + 7) % 7
                     + 7 * (pc.day_ordinal - (0 < pc.day_ordinal)));
      Start = mktime (&tm);
      if (Start == (time_t) -1)
        return Start;
    }

  if (pc.zones_seen)
    {
      int delta = pc.time_zone * 60;
#ifdef HAVE_TM_GMTOFF
      delta -= tm.tm_gmtoff;
#else
      struct tm *gmt = gmtime (&Start);
      if (! gmt)
        return -1;
      delta -= tm_diff (&tm, gmt);
#endif
      if ((Start < Start - delta) != (delta < 0))
        return -1;      /* time_t overflow */
      Start -= delta;
    }

  return Start;
}

#if TEST

#include <stdio.h>

int
main (int ac, char **av)
{
  char buff[BUFSIZ];
  time_t d;

  printf ("Enter date, or blank line to exit.\n\t> ");
  fflush (stdout);

  buff[BUFSIZ - 1] = 0;
  while (fgets (buff, BUFSIZ - 1, stdin) && buff[0])
    {
      d = get_date (buff, 0);
      if (d == (time_t) -1)
        printf ("Bad format - couldn't convert.\n");
      else
        printf ("%s", ctime (&d));
      printf ("\t> ");
      fflush (stdout);
    }
  return 0;
}
#endif /* defined TEST */