editfns.c

/* Lisp functions pertaining to editing.
   Copyright (C) 1985,86,87,89,93,94,95,96 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs 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.

GNU Emacs 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 GNU Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


#include <sys/types.h>

#include <config.h>

#ifdef VMS
#include "vms-pwd.h"
#else
#include <pwd.h>
#endif

#include "lisp.h"
#include "intervals.h"
#include "buffer.h"
#include "window.h"

#include "systime.h"

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

extern char **environ;
extern Lisp_Object make_time ();
extern void insert_from_buffer ();
static int tm_diff ();
static void update_buffer_properties ();
void set_time_zone_rule ();

Lisp_Object Vbuffer_access_fontify_functions;
Lisp_Object Qbuffer_access_fontify_functions;
Lisp_Object Vbuffer_access_fontified_property;

/* Some static data, and a function to initialize it for each run */

Lisp_Object Vsystem_name;
Lisp_Object Vuser_real_login_name;	/* login name of current user ID */
Lisp_Object Vuser_full_name;		/* full name of current user */
Lisp_Object Vuser_login_name;		/* user name from LOGNAME or USER */

void
init_editfns ()
{
  char *user_name;
  register unsigned char *p, *q, *r;
  struct passwd *pw;	/* password entry for the current user */
  Lisp_Object tem;

  /* Set up system_name even when dumping.  */
  init_system_name ();

#ifndef CANNOT_DUMP
  /* Don't bother with this on initial start when just dumping out */
  if (!initialized)
    return;
#endif /* not CANNOT_DUMP */

  pw = (struct passwd *) getpwuid (getuid ());
#ifdef MSDOS
  /* We let the real user name default to "root" because that's quite
     accurate on MSDOG and because it lets Emacs find the init file.
     (The DVX libraries override the Djgpp libraries here.)  */
  Vuser_real_login_name = build_string (pw ? pw->pw_name : "root");
#else
  Vuser_real_login_name = build_string (pw ? pw->pw_name : "unknown");
#endif

  /* Get the effective user name, by consulting environment variables,
     or the effective uid if those are unset.  */
  user_name = (char *) getenv ("LOGNAME");
  if (!user_name)
#ifdef WINDOWSNT
    user_name = (char *) getenv ("USERNAME");	/* it's USERNAME on NT */
#else  /* WINDOWSNT */
    user_name = (char *) getenv ("USER");
#endif /* WINDOWSNT */
  if (!user_name)
    {
      pw = (struct passwd *) getpwuid (geteuid ());
      user_name = (char *) (pw ? pw->pw_name : "unknown");
    }
  Vuser_login_name = build_string (user_name);

  /* If the user name claimed in the environment vars differs from
     the real uid, use the claimed name to find the full name.  */
  tem = Fstring_equal (Vuser_login_name, Vuser_real_login_name);
  Vuser_full_name = Fuser_full_name (NILP (tem)? make_number (geteuid())
				     : Vuser_login_name);
  
  p = (unsigned char *) getenv ("NAME");
  if (p)
    Vuser_full_name = build_string (p);
  else if (NILP (Vuser_full_name))
    Vuser_full_name = build_string ("unknown");
}

DEFUN ("char-to-string", Fchar_to_string, Schar_to_string, 1, 1, 0,
  "Convert arg CHARACTER to a one-character string containing that character.")
  (character)
     Lisp_Object character;
{
  char c;
  CHECK_NUMBER (character, 0);

  c = XINT (character);
  return make_string (&c, 1);
}

DEFUN ("string-to-char", Fstring_to_char, Sstring_to_char, 1, 1, 0,
  "Convert arg STRING to a character, the first character of that string.")
  (string)
     register Lisp_Object string;
{
  register Lisp_Object val;
  register struct Lisp_String *p;
  CHECK_STRING (string, 0);

  p = XSTRING (string);
  if (p->size)
    XSETFASTINT (val, ((unsigned char *) p->data)[0]);
  else
    XSETFASTINT (val, 0);
  return val;
}

static Lisp_Object
buildmark (val)
     int val;
{
  register Lisp_Object mark;
  mark = Fmake_marker ();
  Fset_marker (mark, make_number (val), Qnil);
  return mark;
}

DEFUN ("point", Fpoint, Spoint, 0, 0, 0,
  "Return value of point, as an integer.\n\
Beginning of buffer is position (point-min)")
  ()
{
  Lisp_Object temp;
  XSETFASTINT (temp, PT);
  return temp;
}

DEFUN ("point-marker", Fpoint_marker, Spoint_marker, 0, 0, 0,
   "Return value of point, as a marker object.")
  ()
{
  return buildmark (PT);
}

int
clip_to_bounds (lower, num, upper)
     int lower, num, upper;
{
  if (num < lower)
    return lower;
  else if (num > upper)
    return upper;
  else
    return num;
}

DEFUN ("goto-char", Fgoto_char, Sgoto_char, 1, 1, "NGoto char: ",
  "Set point to POSITION, a number or marker.\n\
Beginning of buffer is position (point-min), end is (point-max).")
  (position)
     register Lisp_Object position;
{
  CHECK_NUMBER_COERCE_MARKER (position, 0);

  SET_PT (clip_to_bounds (BEGV, XINT (position), ZV));
  return position;
}

static Lisp_Object
region_limit (beginningp)
     int beginningp;
{
  extern Lisp_Object Vmark_even_if_inactive; /* Defined in callint.c. */
  register Lisp_Object m;
  if (!NILP (Vtransient_mark_mode) && NILP (Vmark_even_if_inactive)
      && NILP (current_buffer->mark_active))
    Fsignal (Qmark_inactive, Qnil);
  m = Fmarker_position (current_buffer->mark);
  if (NILP (m)) error ("There is no region now");
  if ((PT < XFASTINT (m)) == beginningp)
    return (make_number (PT));
  else
    return (m);
}

DEFUN ("region-beginning", Fregion_beginning, Sregion_beginning, 0, 0, 0,
  "Return position of beginning of region, as an integer.")
  ()
{
  return (region_limit (1));
}

DEFUN ("region-end", Fregion_end, Sregion_end, 0, 0, 0,
  "Return position of end of region, as an integer.")
  ()
{
  return (region_limit (0));
}

DEFUN ("mark-marker", Fmark_marker, Smark_marker, 0, 0, 0,
  "Return this buffer's mark, as a marker object.\n\
Watch out!  Moving this marker changes the mark position.\n\
If you set the marker not to point anywhere, the buffer will have no mark.")
  ()
{
  return current_buffer->mark;
}

DEFUN ("line-beginning-position", Fline_beginning_position, Sline_beginning_position,
  0, 1, 0,
  "Return the character position of the first character on the current line.\n\
With argument N not nil or 1, move forward N - 1 lines first.\n\
If scan reaches end of buffer, return that position.\n\
This function does not move point.")
  (n)
     Lisp_Object n;
{
  register int orig, end;

  if (NILP (n))
    XSETFASTINT (n, 1);
  else
    CHECK_NUMBER (n, 0);

  orig = PT;
  Fforward_line (make_number (XINT (n) - 1));
  end = PT;
  SET_PT (orig);

  return make_number (end);
}

DEFUN ("line-end-position", Fline_end_position, Sline_end_position,
  0, 1, 0,
  "Return the character position of the last character on the current line.\n\
With argument N not nil or 1, move forward N - 1 lines first.\n\
If scan reaches end of buffer, return that position.\n\
This function does not move point.")
  (n)
     Lisp_Object n;
{
  if (NILP (n))
    XSETFASTINT (n, 1);
  else
    CHECK_NUMBER (n, 0);

  return make_number (find_before_next_newline 
		      (PT, 0, XINT (n) - (XINT (n) <= 0)));
}

Lisp_Object
save_excursion_save ()
{
  register int visible = (XBUFFER (XWINDOW (selected_window)->buffer)
			  == current_buffer);

  return Fcons (Fpoint_marker (),
		Fcons (Fcopy_marker (current_buffer->mark, Qnil),
		       Fcons (visible ? Qt : Qnil,
			      current_buffer->mark_active)));		       
}

Lisp_Object
save_excursion_restore (info)
     Lisp_Object info;
{
  Lisp_Object tem, tem1, omark, nmark;
  struct gcpro gcpro1, gcpro2, gcpro3;

  tem = Fmarker_buffer (Fcar (info));
  /* If buffer being returned to is now deleted, avoid error */
  /* Otherwise could get error here while unwinding to top level
     and crash */
  /* In that case, Fmarker_buffer returns nil now.  */
  if (NILP (tem))
    return Qnil;

  omark = nmark = Qnil;
  GCPRO3 (info, omark, nmark);

  Fset_buffer (tem);
  tem = Fcar (info);
  Fgoto_char (tem);
  unchain_marker (tem);
  tem = Fcar (Fcdr (info));
  omark = Fmarker_position (current_buffer->mark);
  Fset_marker (current_buffer->mark, tem, Fcurrent_buffer ());
  nmark = Fmarker_position (tem);
  unchain_marker (tem);
  tem = Fcdr (Fcdr (info));
#if 0 /* We used to make the current buffer visible in the selected window
	 if that was true previously.  That avoids some anomalies.
	 But it creates others, and it wasn't documented, and it is simpler
	 and cleaner never to alter the window/buffer connections.  */
  tem1 = Fcar (tem);
  if (!NILP (tem1)
      && current_buffer != XBUFFER (XWINDOW (selected_window)->buffer))
    Fswitch_to_buffer (Fcurrent_buffer (), Qnil);
#endif /* 0 */

  tem1 = current_buffer->mark_active;
  current_buffer->mark_active = Fcdr (tem);
  if (!NILP (Vrun_hooks))
    {
      /* If mark is active now, and either was not active
	 or was at a different place, run the activate hook.  */
      if (! NILP (current_buffer->mark_active))
	{
	  if (! EQ (omark, nmark))
	    call1 (Vrun_hooks, intern ("activate-mark-hook"));
	}
      /* If mark has ceased to be active, run deactivate hook.  */
      else if (! NILP (tem1))
	call1 (Vrun_hooks, intern ("deactivate-mark-hook"));
    }
  UNGCPRO;
  return Qnil;
}

DEFUN ("save-excursion", Fsave_excursion, Ssave_excursion, 0, UNEVALLED, 0,
  "Save point, mark, and current buffer; execute BODY; restore those things.\n\
Executes BODY just like `progn'.\n\
The values of point, mark and the current buffer are restored\n\
even in case of abnormal exit (throw or error).\n\
The state of activation of the mark is also restored.")
  (args)
     Lisp_Object args;
{
  register Lisp_Object val;
  int count = specpdl_ptr - specpdl;

  record_unwind_protect (save_excursion_restore, save_excursion_save ());

  val = Fprogn (args);
  return unbind_to (count, val);
}

DEFUN ("save-current-buffer", Fsave_current_buffer, Ssave_current_buffer, 0, UNEVALLED, 0,
  "Save the current buffer; execute BODY; restore the current buffer.\n\
Executes BODY just like `progn'.")
  (args)
     Lisp_Object args;
{
  register Lisp_Object val;
  int count = specpdl_ptr - specpdl;

  record_unwind_protect (Fset_buffer, Fcurrent_buffer ());

  val = Fprogn (args);
  return unbind_to (count, val);
}

DEFUN ("buffer-size", Fbufsize, Sbufsize, 0, 0, 0,
  "Return the number of characters in the current buffer.")
  ()
{
  Lisp_Object temp;
  XSETFASTINT (temp, Z - BEG);
  return temp;
}

DEFUN ("point-min", Fpoint_min, Spoint_min, 0, 0, 0,
  "Return the minimum permissible value of point in the current buffer.\n\
This is 1, unless narrowing (a buffer restriction) is in effect.")
  ()
{
  Lisp_Object temp;
  XSETFASTINT (temp, BEGV);
  return temp;
}

DEFUN ("point-min-marker", Fpoint_min_marker, Spoint_min_marker, 0, 0, 0,
  "Return a marker to the minimum permissible value of point in this buffer.\n\
This is the beginning, unless narrowing (a buffer restriction) is in effect.")
  ()
{
  return buildmark (BEGV);
}

DEFUN ("point-max", Fpoint_max, Spoint_max, 0, 0, 0,
  "Return the maximum permissible value of point in the current buffer.\n\
This is (1+ (buffer-size)), unless narrowing (a buffer restriction)\n\
is in effect, in which case it is less.")
  ()
{
  Lisp_Object temp;
  XSETFASTINT (temp, ZV);
  return temp;
}

DEFUN ("point-max-marker", Fpoint_max_marker, Spoint_max_marker, 0, 0, 0,
  "Return a marker to the maximum permissible value of point in this buffer.\n\
This is (1+ (buffer-size)), unless narrowing (a buffer restriction)\n\
is in effect, in which case it is less.")
  ()
{
  return buildmark (ZV);
}

DEFUN ("following-char", Ffollowing_char, Sfollowing_char, 0, 0, 0,
  "Return the character following point, as a number.\n\
At the end of the buffer or accessible region, return 0.")
  ()
{
  Lisp_Object temp;
  if (PT >= ZV)
    XSETFASTINT (temp, 0);
  else
    XSETFASTINT (temp, FETCH_CHAR (PT));
  return temp;
}

DEFUN ("preceding-char", Fprevious_char, Sprevious_char, 0, 0, 0,
  "Return the character preceding point, as a number.\n\
At the beginning of the buffer or accessible region, return 0.")
  ()
{
  Lisp_Object temp;
  if (PT <= BEGV)
    XSETFASTINT (temp, 0);
  else
    XSETFASTINT (temp, FETCH_CHAR (PT - 1));
  return temp;
}

DEFUN ("bobp", Fbobp, Sbobp, 0, 0, 0,
  "Return T if point is at the beginning of the buffer.\n\
If the buffer is narrowed, this means the beginning of the narrowed part.")
  ()
{
  if (PT == BEGV)
    return Qt;
  return Qnil;
}

DEFUN ("eobp", Feobp, Seobp, 0, 0, 0,
  "Return T if point is at the end of the buffer.\n\
If the buffer is narrowed, this means the end of the narrowed part.")
  ()
{
  if (PT == ZV)
    return Qt;
  return Qnil;
}

DEFUN ("bolp", Fbolp, Sbolp, 0, 0, 0,
  "Return T if point is at the beginning of a line.")
  ()
{
  if (PT == BEGV || FETCH_CHAR (PT - 1) == '\n')
    return Qt;
  return Qnil;
}

DEFUN ("eolp", Feolp, Seolp, 0, 0, 0,
  "Return T if point is at the end of a line.\n\
`End of a line' includes point being at the end of the buffer.")
  ()
{
  if (PT == ZV || FETCH_CHAR (PT) == '\n')
    return Qt;
  return Qnil;
}

DEFUN ("char-after", Fchar_after, Schar_after, 1, 1, 0,
  "Return character in current buffer at position POS.\n\
POS is an integer or a buffer pointer.\n\
If POS is out of range, the value is nil.")
  (pos)
     Lisp_Object pos;
{
  register Lisp_Object val;
  register int n;

  CHECK_NUMBER_COERCE_MARKER (pos, 0);

  n = XINT (pos);
  if (n < BEGV || n >= ZV) return Qnil;

  XSETFASTINT (val, FETCH_CHAR (n));
  return val;
}

DEFUN ("user-login-name", Fuser_login_name, Suser_login_name, 0, 1, 0,
  "Return the name under which the user logged in, as a string.\n\
This is based on the effective uid, not the real uid.\n\
Also, if the environment variable LOGNAME or USER is set,\n\
that determines the value of this function.\n\n\
If optional argument UID is an integer, return the login name of the user\n\
with that uid, or nil if there is no such user.")
  (uid)
     Lisp_Object uid;
{
  struct passwd *pw;

  /* Set up the user name info if we didn't do it before.
     (That can happen if Emacs is dumpable
     but you decide to run `temacs -l loadup' and not dump.  */
  if (INTEGERP (Vuser_login_name))
    init_editfns ();

  if (NILP (uid))
    return Vuser_login_name;

  CHECK_NUMBER (uid, 0);
  pw = (struct passwd *) getpwuid (XINT (uid));
  return (pw ? build_string (pw->pw_name) : Qnil);
}

DEFUN ("user-real-login-name", Fuser_real_login_name, Suser_real_login_name,
  0, 0, 0,
  "Return the name of the user's real uid, as a string.\n\
This ignores the environment variables LOGNAME and USER, so it differs from\n\
`user-login-name' when running under `su'.")
  ()
{
  /* Set up the user name info if we didn't do it before.
     (That can happen if Emacs is dumpable
     but you decide to run `temacs -l loadup' and not dump.  */
  if (INTEGERP (Vuser_login_name))
    init_editfns ();
  return Vuser_real_login_name;
}

DEFUN ("user-uid", Fuser_uid, Suser_uid, 0, 0, 0,
  "Return the effective uid of Emacs, as an integer.")
  ()
{
  return make_number (geteuid ());
}

DEFUN ("user-real-uid", Fuser_real_uid, Suser_real_uid, 0, 0, 0,
  "Return the real uid of Emacs, as an integer.")
  ()
{
  return make_number (getuid ());
}

DEFUN ("user-full-name", Fuser_full_name, Suser_full_name, 0, 1, 0,
  "Return the full name of the user logged in, as a string.\n\
If optional argument UID is an integer, return the full name of the user\n\
with that uid, or \"unknown\" if there is no such user.
If UID is a string, return the full name of the user with that login\n\
name, or \"unknown\" if no such user could be found.")
  (uid)
     Lisp_Object uid;
{
  struct passwd *pw;
  register char *p, *q;
  extern char *index ();
  Lisp_Object full;

  if (NILP (uid))
    return Vuser_full_name; 
  else if (NUMBERP (uid))
    pw = (struct passwd *) getpwuid (XINT (uid));
  else if (STRINGP (uid)) 
    pw = (struct passwd *) getpwnam (XSTRING (uid)->data);
  else
    error ("Invalid UID specification");

  if (!pw)
    return Qnil;
  
  p = (unsigned char *) USER_FULL_NAME;
  /* Chop off everything after the first comma. */
  q = (unsigned char *) index (p, ',');
  full = make_string (p, q ? q - p : strlen (p));
  
#ifdef AMPERSAND_FULL_NAME
  p = XSTRING (full)->data;
  q = (unsigned char *) index (p, '&');
  /* Substitute the login name for the &, upcasing the first character.  */
  if (q)
    {
      register char *r;
      Lisp_Object login;

      login = Fuser_login_name (make_number (pw->pw_uid));
      r = (unsigned char *) alloca (strlen (p) + XSTRING (login)->size + 1);
      bcopy (p, r, q - p);
      r[q - p] = 0;
      strcat (r, XSTRING (login)->data);
      r[q - p] = UPCASE (r[q - p]);
      strcat (r, q + 1);
      full = build_string (r);
    }
#endif /* AMPERSAND_FULL_NAME */

  return full;
}

DEFUN ("system-name", Fsystem_name, Ssystem_name, 0, 0, 0,
  "Return the name of the machine you are running on, as a string.")
  ()
{
  return Vsystem_name;
}

/* For the benefit of callers who don't want to include lisp.h */
char *
get_system_name ()
{
  return (char *) XSTRING (Vsystem_name)->data;
}

DEFUN ("emacs-pid", Femacs_pid, Semacs_pid, 0, 0, 0,
  "Return the process ID of Emacs, as an integer.")
  ()
{
  return make_number (getpid ());
}

DEFUN ("current-time", Fcurrent_time, Scurrent_time, 0, 0, 0,
  "Return the current time, as the number of seconds since 1970-01-01 00:00:00.\n\
The time is returned as a list of three integers.  The first has the\n\
most significant 16 bits of the seconds, while the second has the\n\
least significant 16 bits.  The third integer gives the microsecond\n\
count.\n\
\n\
The microsecond count is zero on systems that do not provide\n\
resolution finer than a second.")
  ()
{
  EMACS_TIME t;
  Lisp_Object result[3];

  EMACS_GET_TIME (t);
  XSETINT (result[0], (EMACS_SECS (t) >> 16) & 0xffff);
  XSETINT (result[1], (EMACS_SECS (t) >> 0)  & 0xffff);
  XSETINT (result[2], EMACS_USECS (t));

  return Flist (3, result);
}


static int
lisp_time_argument (specified_time, result)
     Lisp_Object specified_time;
     time_t *result;
{
  if (NILP (specified_time))
    return time (result) != -1;
  else
    {
      Lisp_Object high, low;
      high = Fcar (specified_time);
      CHECK_NUMBER (high, 0);
      low = Fcdr (specified_time);
      if (CONSP (low))
	low = Fcar (low);
      CHECK_NUMBER (low, 0);
      *result = (XINT (high) << 16) + (XINT (low) & 0xffff);
      return *result >> 16 == XINT (high);
    }
}

DEFUN ("format-time-string", Fformat_time_string, Sformat_time_string, 1, 2, 0,
  "Use FORMAT-STRING to format the time TIME.\n\
TIME is specified as (HIGH LOW . IGNORED) or (HIGH . LOW), as from\n\
`current-time' and `file-attributes'.\n\
FORMAT-STRING may contain %-sequences to substitute parts of the time.\n\
%a is replaced by the abbreviated name of the day of week.\n\
%A is replaced by the full name of the day of week.\n\
%b is replaced by the abbreviated name of the month.\n\
%B is replaced by the full name of the month.\n\
%c stands for the preferred date/time format of the C locale.\n\
%d is replaced by the day of month, zero-padded.\n\
%D is a synonym for \"%m/%d/%y\".\n\
%e is replaced by the day of month, blank-padded.\n\
%h is a synonym for \"%b\".\n\
%H is replaced by the hour (00-23).\n\
%I is replaced by the hour (00-12).\n\
%j is replaced by the day of the year (001-366).\n\
%k is replaced by the hour (0-23), blank padded.\n\
%l is replaced by the hour (1-12), blank padded.\n\
%m is replaced by the month (01-12).\n\
%M is replaced by the minute (00-59).\n\
%n is a synonym for \"\\n\".\n\
%p is replaced by AM or PM, as appropriate.\n\
%r is a synonym for \"%I:%M:%S %p\".\n\
%R is a synonym for \"%H:%M\".\n\
%S is replaced by the second (00-60).\n\
%t is a synonym for \"\\t\".\n\
%T is a synonym for \"%H:%M:%S\".\n\
%U is replaced by the week of the year (00-53), first day of week is Sunday.\n\
%w is replaced by the day of week (0-6), Sunday is day 0.\n\
%W is replaced by the week of the year (00-53), first day of week is Monday.\n\
%x is a locale-specific synonym, which defaults to \"%D\" in the C locale.\n\
%X is a locale-specific synonym, which defaults to \"%T\" in the C locale.\n\
%y is replaced by the year without century (00-99).\n\
%Y is replaced by the year with century.\n\
%Z is replaced by the time zone abbreviation.\n\
\n\
The number of options reflects the `strftime' function.")
  (format_string, time)
     Lisp_Object format_string, time;
{
  time_t value;
  int size;

  CHECK_STRING (format_string, 1);

  if (! lisp_time_argument (time, &value))
    error ("Invalid time specification");

  /* This is probably enough.  */
  size = XSTRING (format_string)->size * 6 + 50;

  while (1)
    {
      char *buf = (char *) alloca (size);
      *buf = 1;
      if (emacs_strftime (buf, size, XSTRING (format_string)->data,
			  localtime (&value))
	  || !*buf)
	return build_string (buf);
      /* If buffer was too small, make it bigger.  */
      size *= 2;
    }
}

DEFUN ("decode-time", Fdecode_time, Sdecode_time, 0, 1, 0,
  "Decode a time value as (SEC MINUTE HOUR DAY MONTH YEAR DOW DST ZONE).\n\
The optional SPECIFIED-TIME should be a list of (HIGH LOW . IGNORED)\n\
or (HIGH . LOW), as from `current-time' and `file-attributes', or `nil'\n\
to use the current time.  The list has the following nine members:\n\
SEC is an integer between 0 and 60; SEC is 60 for a leap second, which\n\
only some operating systems support.  MINUTE is an integer between 0 and 59.\n\
HOUR is an integer between 0 and 23.  DAY is an integer between 1 and 31.\n\
MONTH is an integer between 1 and 12.  YEAR is an integer indicating the\n\
four-digit year.  DOW is the day of week, an integer between 0 and 6, where\n\
0 is Sunday.  DST is t if daylight savings time is effect, otherwise nil.\n\
ZONE is an integer indicating the number of seconds east of Greenwich.\n\
\(Note that Common Lisp has different meanings for DOW and ZONE.)")
  (specified_time)
     Lisp_Object specified_time;
{
  time_t time_spec;
  struct tm save_tm;
  struct tm *decoded_time;
  Lisp_Object list_args[9];
  
  if (! lisp_time_argument (specified_time, &time_spec))
    error ("Invalid time specification");

  decoded_time = localtime (&time_spec);
  XSETFASTINT (list_args[0], decoded_time->tm_sec);
  XSETFASTINT (list_args[1], decoded_time->tm_min);
  XSETFASTINT (list_args[2], decoded_time->tm_hour);
  XSETFASTINT (list_args[3], decoded_time->tm_mday);
  XSETFASTINT (list_args[4], decoded_time->tm_mon + 1);
  XSETINT (list_args[5], decoded_time->tm_year + 1900);
  XSETFASTINT (list_args[6], decoded_time->tm_wday);
  list_args[7] = (decoded_time->tm_isdst)? Qt : Qnil;

  /* Make a copy, in case gmtime modifies the struct.  */
  save_tm = *decoded_time;
  decoded_time = gmtime (&time_spec);
  if (decoded_time == 0)
    list_args[8] = Qnil;
  else
    XSETINT (list_args[8], tm_diff (&save_tm, decoded_time));
  return Flist (9, list_args);
}

DEFUN ("encode-time", Fencode_time, Sencode_time, 6, MANY, 0,
  "Convert SECOND, MINUTE, HOUR, DAY, MONTH, YEAR and ZONE to internal time.\n\
This is the reverse operation of `decode-time', which see.\n\
ZONE defaults to the current time zone rule.  This can\n\
be a string or t (as from `set-time-zone-rule'), or it can be a list\n\
\(as from `current-time-zone') or an integer (as from `decode-time')\n\
applied without consideration for daylight savings time.\n\
\n\
You can pass more than 7 arguments; then the first six arguments\n\
are used as SECOND through YEAR, and the *last* argument is used as ZONE.\n\
The intervening arguments are ignored.\n\
This feature lets (apply 'encode-time (decode-time ...)) work.\n\
\n\
Out-of-range values for SEC, MINUTE, HOUR, DAY, or MONTH are allowed;\n\
for example, a DAY of 0 means the day preceding the given month.\n\
Year numbers less than 100 are treated just like other year numbers.\n\
If you want them to stand for years in this century, you must do that yourself.")
  (nargs, args)
     int nargs;
     register Lisp_Object *args;
{
  time_t time;
  struct tm tm;
  Lisp_Object zone = (nargs > 6)? args[nargs - 1] : Qnil;

  CHECK_NUMBER (args[0], 0);	/* second */
  CHECK_NUMBER (args[1], 1);	/* minute */
  CHECK_NUMBER (args[2], 2);	/* hour */
  CHECK_NUMBER (args[3], 3);	/* day */
  CHECK_NUMBER (args[4], 4);	/* month */
  CHECK_NUMBER (args[5], 5);	/* year */

  tm.tm_sec = XINT (args[0]);
  tm.tm_min = XINT (args[1]);
  tm.tm_hour = XINT (args[2]);
  tm.tm_mday = XINT (args[3]);
  tm.tm_mon = XINT (args[4]) - 1;
  tm.tm_year = XINT (args[5]) - 1900;
  tm.tm_isdst = -1;

  if (CONSP (zone))
    zone = Fcar (zone);
  if (NILP (zone))
    time = mktime (&tm);
  else
    {
      char tzbuf[100];
      char *tzstring;
      char **oldenv = environ, **newenv;
      
      if (zone == Qt)
	tzstring = "UTC0";
      else if (STRINGP (zone))
	tzstring = (char *) XSTRING (zone)->data;
      else if (INTEGERP (zone))
	{
	  int abszone = abs (XINT (zone));
	  sprintf (tzbuf, "XXX%s%d:%02d:%02d", "-" + (XINT (zone) < 0),
		   abszone / (60*60), (abszone/60) % 60, abszone % 60);
	  tzstring = tzbuf;
	}
      else
	error ("Invalid time zone specification");

      /* Set TZ before calling mktime; merely adjusting mktime's returned 
	 value doesn't suffice, since that would mishandle leap seconds.  */
      set_time_zone_rule (tzstring);

      time = mktime (&tm);

      /* Restore TZ to previous value.  */
      newenv = environ;
      environ = oldenv;
      xfree (newenv);
#ifdef LOCALTIME_CACHE
      tzset ();
#endif
    }

  if (time == (time_t) -1)
    error ("Specified time is not representable");

  return make_time (time);
}

DEFUN ("current-time-string", Fcurrent_time_string, Scurrent_time_string, 0, 1, 0,
  "Return the current time, as a human-readable string.\n\
Programs can use this function to decode a time,\n\
since the number of columns in each field is fixed.\n\
The format is `Sun Sep 16 01:03:52 1973'.\n\
If an argument is given, it specifies a time to format\n\
instead of the current time.  The argument should have the form:\n\
  (HIGH . LOW)\n\
or the form:\n\
  (HIGH LOW . IGNORED).\n\
Thus, you can use times obtained from `current-time'\n\
and from `file-attributes'.")
  (specified_time)
     Lisp_Object specified_time;
{
  time_t value;
  char buf[30];
  register char *tem;

  if (! lisp_time_argument (specified_time, &value))
    value = -1;
  tem = (char *) ctime (&value);

  strncpy (buf, tem, 24);
  buf[24] = 0;

  return build_string (buf);
}

#define TM_YEAR_BASE 1900

/* Yield A - B, measured in seconds.
   This function is copied from the GNU C Library.  */
static int
tm_diff (a, b)
     struct tm *a, *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));
}

DEFUN ("current-time-zone", Fcurrent_time_zone, Scurrent_time_zone, 0, 1, 0,
  "Return the offset and name for the local time zone.\n\
This returns a list of the form (OFFSET NAME).\n\
OFFSET is an integer number of seconds ahead of UTC (east of Greenwich).\n\
    A negative value means west of Greenwich.\n\
NAME is a string giving the name of the time zone.\n\
If an argument is given, it specifies when the time zone offset is determined\n\
instead of using the current time.  The argument should have the form:\n\
  (HIGH . LOW)\n\
or the form:\n\
  (HIGH LOW . IGNORED).\n\
Thus, you can use times obtained from `current-time'\n\
and from `file-attributes'.\n\
\n\
Some operating systems cannot provide all this information to Emacs;\n\
in this case, `current-time-zone' returns a list containing nil for\n\
the data it can't find.")
  (specified_time)
     Lisp_Object specified_time;
{
  time_t value;
  struct tm *t;

  if (lisp_time_argument (specified_time, &value)
      && (t = gmtime (&value)) != 0)
    {
      struct tm gmt;
      int offset;
      char *s, buf[6];

      gmt = *t;		/* Make a copy, in case localtime modifies *t.  */
      t = localtime (&value);
      offset = tm_diff (t, &gmt);
      s = 0;
#ifdef HAVE_TM_ZONE
      if (t->tm_zone)
	s = (char *)t->tm_zone;
#else /* not HAVE_TM_ZONE */
#ifdef HAVE_TZNAME
      if (t->tm_isdst == 0 || t->tm_isdst == 1)
	s = tzname[t->tm_isdst];
#endif
#endif /* not HAVE_TM_ZONE */
      if (!s)
	{
	  /* No local time zone name is available; use "+-NNNN" instead.  */
	  int am = (offset < 0 ? -offset : offset) / 60;
	  sprintf (buf, "%c%02d%02d", (offset < 0 ? '-' : '+'), am/60, am%60);
	  s = buf;
	}
      return Fcons (make_number (offset), Fcons (build_string (s), Qnil));
    }
  else
    return Fmake_list (2, Qnil);
}

/* This holds the value of `environ' produced by the previous
   call to Fset_time_zone_rule, or 0 if Fset_time_zone_rule
   has never been called.  */
static char **environbuf;

DEFUN ("set-time-zone-rule", Fset_time_zone_rule, Sset_time_zone_rule, 1, 1, 0,
  "Set the local time zone using TZ, a string specifying a time zone rule.\n\
If TZ is nil, use implementation-defined default time zone information.\n\
If TZ is t, use Universal Time.")
  (tz)
     Lisp_Object tz;
{
  char *tzstring;

  if (NILP (tz))
    tzstring = 0;
  else if (tz == Qt)
    tzstring = "UTC0";
  else
    {
      CHECK_STRING (tz, 0);
      tzstring = (char *) XSTRING (tz)->data;
    }

  set_time_zone_rule (tzstring);
  if (environbuf)
    free (environbuf);
  environbuf = environ;

  return Qnil;
}

/* These two values are known to load tz files in buggy implementations.
   Their values shouldn't matter in non-buggy implementations.
   We don't use string literals for these strings, 
   since if a string in the environment is in readonly
   storage, it runs afoul of bugs in SVR4 and Solaris 2.3.
   See Sun bugs 1113095 and 1114114, ``Timezone routines
   improperly modify environment''.  */

static char set_time_zone_rule_tz1[] = "TZ=GMT0";
static char set_time_zone_rule_tz2[] = "TZ=GMT1";

/* Set the local time zone rule to TZSTRING.
   This allocates memory into `environ', which it is the caller's
   responsibility to free.  */
void
set_time_zone_rule (tzstring)
     char *tzstring;
{
  int envptrs;
  char **from, **to, **newenv;

  /* Make the ENVIRON vector longer with room for TZSTRING.  */
  for (from = environ; *from; from++)
    continue;
  envptrs = from - environ + 2;
  newenv = to = (char **) xmalloc (envptrs * sizeof (char *)
				   + (tzstring ? strlen (tzstring) + 4 : 0));

  /* Add TZSTRING to the end of environ, as a value for TZ.  */
  if (tzstring)
    {
      char *t = (char *) (to + envptrs);
      strcpy (t, "TZ=");
      strcat (t, tzstring);
      *to++ = t;
    }

  /* Copy the old environ vector elements into NEWENV,
     but don't copy the TZ variable.
     So we have only one definition of TZ, which came from TZSTRING.  */
  for (from = environ; *from; from++)
    if (strncmp (*from, "TZ=", 3) != 0)
      *to++ = *from;
  *to = 0;

  environ = newenv;

  /* If we do have a TZSTRING, NEWENV points to the vector slot where
     the TZ variable is stored.  If we do not have a TZSTRING,
     TO points to the vector slot which has the terminating null.  */