libguile/options.c

   1 /* Copyright (C) 1995,1996,1998,2000,2001, 2006, 2008, 2009, 2010, 2011 Free Software Foundation
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public License
   5  * as published by the Free Software Foundation; either version 3 of
   6  * the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  16  * 02110-1301 USA
  17  */
  18
  19 \f
  20 #ifdef HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #include "libguile/_scm.h"
  25 #include "libguile/mallocs.h"
  26 #include "libguile/strings.h"
  27
  28 #include "libguile/options.h"
  29 \f
  30
  31 /* {Run-time options}
  32  *
  33  * This is the basic interface for low-level configuration of the
  34  * Guile library.  It is used for configuring the reader, evaluator,
  35  * printer and debugger.
  36  *
  37  * Motivation:
  38  *
  39  * 1. Altering option settings can have side effects.
  40  * 2. Option values can be stored in native format.
  41  *    (Important for efficiency in, e. g., the evaluator.)
  42  * 3. Doesn't use up name space.
  43  * 4. Options can be naturally grouped => ease of use.
  44  */
  45
  46 /* scm_options is the core of all options interface procedures.
  47  *
  48  * Some definitions:
  49  *
  50  * Run time options in Guile are arranged in groups.  Each group
  51  * affects a certain aspect of the behaviour of the library.
  52  *
  53  * An "options interface procedure" manages one group of options.  It
  54  * can be used to check or set options, or to get documentation for
  55  * all options of a group.  The options interface procedure is not
  56  * intended to be called directly by the user.  The user should
  57  * instead call
  58  *
  59  *   (<group>-options)
  60  *   (<group>-options 'help)
  61  *   (<group>-options 'full)
  62  *
  63  * to display current option settings (The second version also
  64  * displays documentation.  The third version also displays
  65  * information about programmer's options.), and
  66  *
  67  *   (<group>-enable  '<option-symbol>)
  68  *   (<group>-disable '<option-symbol>)
  69  *   (<group>-set! <option-symbol> <value>)
  70  *   (<group>-options <option setting>)
  71  *
  72  * to alter the state of an option  (The last version sets all
  73  * options according to <option setting>.) where <group> is the name
  74  * of the option group.
  75  *
  76  * An "option setting" represents the state of all low-level options
  77  * managed by one options interface procedure.  It is a list of
  78  * single symbols and symbols followed by a value.
  79  *
  80  * For boolean options, the presence of the symbol of that option in
  81  * the option setting indicates a true value.  If the symbol isn't a
  82  * member of the option setting this represents a false value.
  83  *
  84  * Other options are represented by a symbol followed by the value.
  85  *
  86  * If scm_options is called without arguments, the current option
  87  * setting is returned.  If the argument is an option setting, options
  88  * are altered and the old setting is returned.  If the argument isn't
  89  * a list, a list of sublists is returned, where each sublist contains
  90  * option name, value and documentation string.
  91  */
  92
  93 SCM_SYMBOL (scm_yes_sym, "yes");
  94 SCM_SYMBOL (scm_no_sym, "no");
  95
  96 /* Return a list of the current option setting.  The format of an
  97  * option setting is described in the above documentation.  */
  98 static SCM
  99 get_option_setting (const scm_t_option options[])
 100 {
 101   unsigned int i;
 102   SCM ls = SCM_EOL;
 103   for (i = 0; options[i].name; ++i)
 104     {
 105       switch (options[i].type)
 106         {
 107         case SCM_OPTION_BOOLEAN:
 108           if (options[i].val)
 109             ls = scm_cons (SCM_PACK (options[i].name), ls);
 110           break;
 111         case SCM_OPTION_INTEGER:
 112           ls = scm_cons (scm_from_unsigned_integer (options[i].val), ls);
 113           ls = scm_cons (SCM_PACK (options[i].name), ls);
 114           break;
 115         case SCM_OPTION_SCM:
 116           ls = scm_cons (SCM_PACK (options[i].val), ls);
 117           ls = scm_cons (SCM_PACK (options[i].name), ls);
 118         }
 119     }
 120   return ls;
 121 }
 122
 123
 124 /* Return a list of sublists, where each sublist contains option name, value
 125  * and documentation string.  */
 126 static SCM
 127 get_documented_option_setting (const scm_t_option options[])
 128 {
 129   SCM ans = SCM_EOL;
 130   unsigned int i;
 131
 132   for (i = 0; options[i].name; ++i)
 133     {
 134       SCM ls = scm_cons (scm_from_utf8_string (options[i].doc), SCM_EOL);
 135       switch (options[i].type)
 136         {
 137         case SCM_OPTION_BOOLEAN:
 138           ls = scm_cons (options[i].val ? scm_yes_sym : scm_no_sym, ls);
 139           break;
 140         case SCM_OPTION_INTEGER:
 141           ls = scm_cons (scm_from_unsigned_integer (options[i].val), ls);
 142           break;
 143         case SCM_OPTION_SCM:
 144           ls = scm_cons (SCM_PACK (options[i].val), ls);
 145         }
 146       ls = scm_cons (SCM_PACK (options[i].name), ls);
 147       ans = scm_cons (ls, ans);
 148     }
 149   return scm_reverse_x (ans, SCM_UNDEFINED);
 150 }
 151
 152
 153 static int
 154 options_length (scm_t_option options[])
 155 {
 156   unsigned int i = 0;
 157   for (; options[i].name != NULL; ++i)
 158     ;
 159
 160   return i;
 161 }
 162
 163 /* Alters options according to the given option setting 'args'.  The value of
 164  * args is known to be a list, but it is not known whether the list is a well
 165  * formed option setting, i. e. if for every non-boolean option a value is
 166  * given.  For this reason, the function applies all changes to a copy of the
 167  * original setting in memory.  Only if 'args' was successfully processed,
 168  * the new setting will overwrite the old one.
 169  *
 170  * If DRY_RUN is set, don't change anything. This is useful for trying out an option
 171  * before entering a critical section.
 172  */
 173 static void
 174 change_option_setting (SCM args, scm_t_option options[], const char *s,
 175                        int dry_run)
 176 {
 177   unsigned int i;
 178   scm_t_bits *new_vals;
 179
 180   new_vals = scm_gc_malloc (options_length (options) * sizeof (scm_t_bits),
 181                             "new-options");
 182
 183   for (i = 0; options[i].name; ++i)
 184     {
 185       if (options[i].type == SCM_OPTION_BOOLEAN)
 186         new_vals[i] = 0;
 187       else
 188         new_vals[i] = options[i].val;
 189     }
 190
 191   while (!SCM_NULL_OR_NIL_P (args))
 192     {
 193       SCM name = SCM_CAR (args);
 194       int found = 0;
 195
 196       for (i = 0; options[i].name && !found; ++i)
 197         {
 198           if (scm_is_eq (name, SCM_PACK (options[i].name)))
 199             {
 200               switch (options[i].type)
 201                 {
 202                 case SCM_OPTION_BOOLEAN:
 203                   new_vals[i] = 1;
 204                   break;
 205                 case SCM_OPTION_INTEGER:
 206                   args = SCM_CDR (args);
 207                   new_vals[i] = scm_to_size_t (scm_car (args));
 208                   break;
 209                 case SCM_OPTION_SCM:
 210                   args = SCM_CDR (args);
 211                   new_vals[i] = SCM_UNPACK (scm_car (args));
 212                   break;
 213                 }
 214               found = 1;
 215             }
 216         }
 217
 218       if (!found)
 219         scm_misc_error (s, "Unknown option name: ~S", scm_list_1 (name));
 220
 221       args = SCM_CDR (args);
 222     }
 223
 224   if (dry_run)
 225     return;
 226
 227   for (i = 0; options[i].name; ++i)
 228     options[i].val = new_vals[i];
 229 }
 230
 231
 232 SCM
 233 scm_options (SCM args, scm_t_option options[], const char *s)
 234 {
 235   return scm_options_try (args, options, s, 0);
 236 }
 237
 238 SCM
 239 scm_options_try (SCM args, scm_t_option options[], const char *s,
 240                  int dry_run)
 241 {
 242   if (SCM_UNBNDP (args))
 243     return get_option_setting (options);
 244   else if (!SCM_NULL_OR_NIL_P (args) && !scm_is_pair (args))
 245     /* Dirk:FIXME:: This criterion should be improved.  IMO it is better to
 246      * demand that args is #t if documentation should be shown than to say
 247      * that every argument except a list will print out documentation.  */
 248     return get_documented_option_setting (options);
 249   else
 250     {
 251       SCM old_setting;
 252       SCM_ASSERT (scm_is_true (scm_list_p (args)), args, 1, s);
 253       old_setting = get_option_setting (options);
 254       change_option_setting (args, options, s, dry_run);
 255       return old_setting;
 256     }
 257 }
 258
 259
 260 void
 261 scm_init_opts (SCM (*func) (SCM), scm_t_option options[])
 262 {
 263   unsigned int i;
 264
 265   for (i = 0; options[i].name; ++i)
 266     {
 267       SCM name = scm_from_utf8_symbol (options[i].name);
 268       options[i].name = (char *) SCM_UNPACK (name);
 269     }
 270   func (SCM_UNDEFINED);
 271 }
 272
 273
 274 void
 275 scm_init_options ()
 276 {
 277 #include "libguile/options.x"
 278 }
 279
 280 /*
 281   Local Variables:
 282   c-file-style: "gnu"
 283   End:
 284 */