guile/libguile/options.c

/*	Copyright (C) 1995, 1996, 1998, 2000 Free Software Foundation
 * 
 * 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 software; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307 USA
 *
 * As a special exception, the Free Software Foundation gives permission
 * for additional uses of the text contained in its release of GUILE.
 *
 * The exception is that, if you link the GUILE library with other files
 * to produce an executable, this does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * Your use of that executable is in no way restricted on account of
 * linking the GUILE library code into it.
 *
 * This exception does not however invalidate any other reasons why
 * the executable file might be covered by the GNU General Public License.
 *
 * This exception applies only to the code released by the
 * Free Software Foundation under the name GUILE.  If you copy
 * code from other Free Software Foundation releases into a copy of
 * GUILE, as the General Public License permits, the exception does
 * not apply to the code that you add in this way.  To avoid misleading
 * anyone as to the status of such modified files, you must delete
 * this exception notice from them.
 *
 * If you write modifications of your own for GUILE, it is your choice
 * whether to permit this exception to apply to your modifications.
 * If you do not wish that, delete this exception notice.
 *
 * The author can be reached at djurfeldt@nada.kth.se
 * Mikael Djurfeldt, SANS/NADA KTH, 10044 STOCKHOLM, SWEDEN */

/* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
   gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */



#include "libguile/_scm.h"
#include "libguile/strings.h"

#include "libguile/options.h"


/* {Run-time options}
 *
 * This is the basic interface for low-level configuration of the
 * Guile library.  It is used for configuring the reader, evaluator,
 * printer and debugger.
 *
 * Motivation:
 *
 * 1. Altering option settings can have side effects.
 * 2. Option values can be stored in native format.
 *    (Important for efficiency in, e. g., the evaluator.)
 * 3. Doesn't use up name space.
 * 4. Options can be naturally grouped => ease of use.
 */

/* scm_options is the core of all options interface procedures.
 *
 * Some definitions:
 *
 * Run time options in Guile are arranged in groups.  Each group
 * affects a certain aspect of the behaviour of the library.
 *
 * An "options interface procedure" manages one group of options.  It
 * can be used to check or set options, or to get documentation for
 * all options of a group.  The options interface procedure is not
 * intended to be called directly by the user.  The user should
 * instead call
 *
 *   (<group>-options)
 *   (<group>-options 'help)
 *   (<group>-options 'full)
 *
 * to display current option settings (The second version also
 * displays documentation.  The third version also displays
 * information about programmer's options.), and
 *
 *   (<group>-enable  '<option-symbol>)
 *   (<group>-disable '<option-symbol>)
 *   (<group>-set! <option-symbol> <value>)
 *   (<group>-options <option setting>)
 *
 * to alter the state of an option  (The last version sets all
 * options according to <option setting>.) where <group> is the name
 * of the option group.
 *
 * An "option setting" represents the state of all low-level options
 * managed by one options interface procedure.  It is a list of
 * single symbols and symbols followed by a value.
 *
 * For boolean options, the presence of the symbol of that option in
 * the option setting indicates a true value.  If the symbol isn't a
 * member of the option setting this represents a false value.
 *
 * Other options are represented by a symbol followed by the value.
 *
 * If scm_options is called without arguments, the current option
 * setting is returned.  If the argument is an option setting, options
 * are altered and the old setting is returned.  If the argument isn't
 * a list, a list of sublists is returned, where each sublist contains
 * option name, value and documentation string.
 */

SCM_SYMBOL (scm_yes_sym, "yes");
SCM_SYMBOL (scm_no_sym, "no");

static SCM protected_objects;

SCM
scm_options (SCM arg, scm_option_t options[], int n, const char *s)
{
  int i, docp = (!SCM_UNBNDP (arg) && !SCM_NULLP (arg) && !SCM_CONSP (arg));
  /* Let `arg' GC protect the arguments */
  SCM new_mode = arg, ans = SCM_EOL, ls;
  for (i = 0; i < n; ++i)
    {
      ls = docp ? scm_cons ((SCM) options[i].doc, SCM_EOL) : ans;
      switch (options[i].type)
	{
	case SCM_OPTION_BOOLEAN:
	  if (docp)
	    ls = scm_cons ((int) options[i].val
			   ? scm_yes_sym
			   : scm_no_sym,
			   ls);
	  break;
	case SCM_OPTION_INTEGER:
	  ls = scm_cons (SCM_MAKINUM (options[i].val), ls);
	  break;
	case SCM_OPTION_SCM:
	  ls = scm_cons ((SCM) options[i].val, ls);
	}
      if (!((options[i].type == SCM_OPTION_BOOLEAN)
	    && !docp
	    && ! (int) options[i].val))
	ls = scm_cons ((SCM) options[i].name, ls);
      ans = docp ? scm_cons (ls, ans) : ls;
    }
  if (!(SCM_UNBNDP (new_mode) || docp))
    {
      unsigned long *flags;
      flags = (unsigned long *) scm_must_malloc (n * sizeof (unsigned long),
						 "mode buffer");
      for (i = 0; i < n; ++i)
	if (options[i].type == SCM_OPTION_BOOLEAN)
	  flags[i] = 0;
	else
	  flags[i] = (unsigned long) options[i].val;
      while (SCM_NNULLP (new_mode))
	{
	  SCM_ASSERT (SCM_CONSP (new_mode),
		      new_mode,
		      SCM_ARG1,
		      s);
	  for (i = 0; i < n; ++i)
	    if (SCM_CAR (new_mode) == (SCM) options[i].name)
	      switch (options[i].type)
		{
		case SCM_OPTION_BOOLEAN:
		  flags[i] = 1;
		  goto cont;
		case SCM_OPTION_INTEGER:
		  new_mode = SCM_CDR (new_mode);
		  SCM_ASSERT (   SCM_CONSP (new_mode)
			      && SCM_INUMP (SCM_CAR (new_mode)),
			      new_mode,
			      SCM_ARG1,
			      s);
		  flags[i] = (unsigned long) SCM_INUM (SCM_CAR (new_mode));
		  goto cont;
		case SCM_OPTION_SCM:
		  new_mode = SCM_CDR (new_mode);
		  flags[i] = SCM_UNPACK (SCM_CAR (new_mode));
		  goto cont;
		}
#ifndef SCM_RECKLESS
	  scm_must_free ((char *) flags);
	  scm_misc_error (s, "Unknown mode flag: ~S", 
			  SCM_LIST1 (SCM_CAR (new_mode)));
#endif
	cont:
	  new_mode = SCM_CDR (new_mode);
	}
      for (i = 0; i < n; ++i)
	{
	  /* scm_option doesn't know if its a long or an SCM */
	  if (options[i].type == SCM_OPTION_SCM)
	    SCM_SETCDR (protected_objects,
			scm_cons (SCM_PACK(flags[i]),
				  scm_delq1_x (SCM_PACK(options[i].val),
					       SCM_CDR (protected_objects))));
	  options[i].val = flags[i];
	}
      scm_must_free ((char *) flags);
    }
  return ans;
}


void
scm_init_opts (SCM (*func) (SCM), scm_option_t options[], int n)
{
  int i;

  for (i = 0; i < n; ++i)
    {
      SCM name;
      SCM doc;

      name = scm_str2symbol (options[i].name);
      options[i].name =	(char *) name;
      scm_permanent_object (name);
      doc = scm_take0str (options[i].doc);
      options[i].doc = (char *) doc;
      scm_permanent_object (doc);
      if (options[i].type == SCM_OPTION_SCM)
	SCM_SETCDR (protected_objects,
		    scm_cons (SCM_PACK(options[i].val), SCM_CDR (protected_objects)));
    }
  func (SCM_UNDEFINED);
}


void
scm_init_options ()
{
  protected_objects = scm_permanent_object (scm_cons (SCM_UNDEFINED, SCM_EOL));
#ifndef SCM_MAGIC_SNARFER
#include "libguile/options.x"
#endif
}

/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/