libguile/objects.c

   1 /* Copyright (C) 1995,1996,1999,2000,2001, 2003, 2004, 2006, 2008 Free Software Foundation, Inc.
   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
   5  * License as published by the Free Software Foundation; either
   6  * version 2.1 of the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful,
   9  * but 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 02110-1301 USA
  16  */
  17
  18
  19 \f
  20
  21 /* This file and objects.h contains those minimal pieces of the Guile
  22  * Object Oriented Programming System which need to be included in
  23  * libguile.  See the comments in objects.h.
  24  */
  25
  26 #ifdef HAVE_CONFIG_H
  27 # include <config.h>
  28 #endif
  29
  30 #include "libguile/_scm.h"
  31
  32 #include "libguile/struct.h"
  33 #include "libguile/procprop.h"
  34 #include "libguile/chars.h"
  35 #include "libguile/keywords.h"
  36 #include "libguile/smob.h"
  37 #include "libguile/eval.h"
  38 #include "libguile/alist.h"
  39 #include "libguile/ports.h"
  40 #include "libguile/strings.h"
  41 #include "libguile/vectors.h"
  42
  43 #include "libguile/validate.h"
  44 #include "libguile/objects.h"
  45 #include "libguile/goops.h"
  46
  47 \f
  48
  49 SCM scm_metaclass_standard;
  50 SCM scm_metaclass_operator;
  51
  52 /* The cache argument for scm_mcache_lookup_cmethod has one of two possible
  53  * formats:
  54  *
  55  * Format #1:
  56  * (SCM_IM_DISPATCH ARGS N-SPECIALIZED
  57  *   #((TYPE1 ... ENV FORMALS FORM ...) ...)
  58  *   GF)
  59  *
  60  * Format #2:
  61  * (SCM_IM_HASH_DISPATCH ARGS N-SPECIALIZED HASHSET MASK
  62  *   #((TYPE1 ... ENV FORMALS FORM ...) ...)
  63  *   GF)
  64  *
  65  * ARGS is either a list of expressions, in which case they
  66  * are interpreted as the arguments of an application, or
  67  * a non-pair, which is interpreted as a single expression
  68  * yielding all arguments.
  69  *
  70  * SCM_IM_DISPATCH expressions in generic functions always
  71  * have ARGS = the symbol `args' or the iloc #@0-0.
  72  *
  73  * Need FORMALS in order to support varying arity.  This
  74  * also avoids the need for renaming of bindings.
  75  *
  76  * We should probably not complicate this mechanism by
  77  * introducing "optimizations" for getters and setters or
  78  * primitive methods.  Getters and setter will normally be
  79  * compiled into @slot-[ref|set!] or a procedure call.
  80  * They rely on the dispatch performed before executing
  81  * the code which contains them.
  82  *
  83  * We might want to use a more efficient representation of
  84  * this form in the future, perhaps after we have introduced
  85  * low-level support for syntax-case macros.
  86  */
  87
  88 SCM
  89 scm_mcache_lookup_cmethod (SCM cache, SCM args)
  90 {
  91   unsigned long i, mask, n, end;
  92   SCM ls, methods, z = SCM_CDDR (cache);
  93   n = scm_to_ulong (SCM_CAR (z)); /* maximum number of specializers */
  94   methods = SCM_CADR (z);
  95
  96   if (scm_is_simple_vector (methods))
  97     {
  98       /* cache format #1: prepare for linear search */
  99       mask = -1;
 100       i = 0;
 101       end = SCM_SIMPLE_VECTOR_LENGTH (methods);
 102     }
 103   else
 104     {
 105       /* cache format #2: compute a hash value */
 106       unsigned long hashset = scm_to_ulong (methods);
 107       long j = n;
 108       z = SCM_CDDR (z);
 109       mask = scm_to_ulong (SCM_CAR (z));
 110       methods = SCM_CADR (z);
 111       i = 0;
 112       ls = args;
 113       if (!scm_is_null (ls))
 114         do
 115           {
 116             i += SCM_STRUCT_DATA (scm_class_of (SCM_CAR (ls)))
 117                  [scm_si_hashsets + hashset];
 118             ls = SCM_CDR (ls);
 119           }
 120         while (j-- && !scm_is_null (ls));
 121       i &= mask;
 122       end = i;
 123     }
 124
 125   /* Search for match  */
 126   do
 127     {
 128       long j = n;
 129       z = SCM_SIMPLE_VECTOR_REF (methods, i);
 130       ls = args; /* list of arguments */
 131       if (!scm_is_null (ls))
 132         do
 133           {
 134             /* More arguments than specifiers => CLASS != ENV */
 135             if (! scm_is_eq (scm_class_of (SCM_CAR (ls)), SCM_CAR (z)))
 136               goto next_method;
 137             ls = SCM_CDR (ls);
 138             z = SCM_CDR (z);
 139           }
 140         while (j-- && !scm_is_null (ls));
 141       /* Fewer arguments than specifiers => CAR != CLASS */
 142       if (!SCM_CLASSP (SCM_CAR (z)))
 143         return z;
 144     next_method:
 145       i = (i + 1) & mask;
 146     } while (i != end);
 147   return SCM_BOOL_F;
 148 }
 149
 150 SCM
 151 scm_mcache_compute_cmethod (SCM cache, SCM args)
 152 {
 153   SCM cmethod = scm_mcache_lookup_cmethod (cache, args);
 154   if (scm_is_false (cmethod))
 155     /* No match - memoize */
 156     return scm_memoize_method (cache, args);
 157   return cmethod;
 158 }
 159
 160 SCM
 161 scm_apply_generic (SCM gf, SCM args)
 162 {
 163   SCM cmethod = scm_mcache_compute_cmethod (SCM_ENTITY_PROCEDURE (gf), args);
 164   if (scm_is_pair (cmethod))
 165     return scm_eval_body (SCM_CDR (SCM_CMETHOD_CODE (cmethod)),
 166                           SCM_EXTEND_ENV (SCM_CAR (SCM_CMETHOD_CODE (cmethod)),
 167                                           args,
 168                                           SCM_CMETHOD_ENV (cmethod)));
 169   else
 170     return scm_apply (cmethod, args, SCM_EOL);
 171 }
 172
 173 SCM
 174 scm_call_generic_0 (SCM gf)
 175 {
 176   return scm_apply_generic (gf, SCM_EOL);
 177 }
 178
 179 SCM
 180 scm_call_generic_1 (SCM gf, SCM a1)
 181 {
 182   return scm_apply_generic (gf, scm_list_1 (a1));
 183 }
 184
 185 SCM
 186 scm_call_generic_2 (SCM gf, SCM a1, SCM a2)
 187 {
 188   return scm_apply_generic (gf, scm_list_2 (a1, a2));
 189 }
 190
 191 SCM
 192 scm_call_generic_3 (SCM gf, SCM a1, SCM a2, SCM a3)
 193 {
 194   return scm_apply_generic (gf, scm_list_3 (a1, a2, a3));
 195 }
 196
 197 SCM_DEFINE (scm_entity_p, "entity?", 1, 0, 0,
 198             (SCM obj),
 199             "Return @code{#t} if @var{obj} is an entity.")
 200 #define FUNC_NAME s_scm_entity_p
 201 {
 202   return scm_from_bool(SCM_STRUCTP (obj) && SCM_I_ENTITYP (obj));
 203 }
 204 #undef FUNC_NAME
 205
 206 SCM_DEFINE (scm_operator_p, "operator?", 1, 0, 0,
 207             (SCM obj),
 208             "Return @code{#t} if @var{obj} is an operator.")
 209 #define FUNC_NAME s_scm_operator_p
 210 {
 211   return scm_from_bool(SCM_STRUCTP (obj)
 212                   && SCM_I_OPERATORP (obj)
 213                   && !SCM_I_ENTITYP (obj));
 214 }
 215 #undef FUNC_NAME
 216
 217 /* XXX - What code requires the object procedure to be only of certain
 218          types? */
 219
 220 SCM_DEFINE (scm_valid_object_procedure_p, "valid-object-procedure?", 1, 0, 0,
 221             (SCM proc),
 222             "Return @code{#t} iff @var{proc} is a procedure that can be used "
 223             "with @code{set-object-procedure}.  It is always valid to use "
 224             "a closure constructed by @code{lambda}.")
 225 #define FUNC_NAME s_scm_valid_object_procedure_p
 226 {
 227   if (SCM_IMP (proc))
 228     return SCM_BOOL_F;
 229   switch (SCM_TYP7 (proc))
 230     {
 231     default:
 232       return SCM_BOOL_F;
 233     case scm_tcs_closures:
 234     case scm_tc7_subr_1:
 235     case scm_tc7_subr_2:
 236     case scm_tc7_subr_3:
 237     case scm_tc7_lsubr_2:
 238       return SCM_BOOL_T;
 239     }
 240 }
 241 #undef FUNC_NAME
 242
 243 SCM_DEFINE (scm_set_object_procedure_x, "set-object-procedure!", 2, 0, 0,
 244             (SCM obj, SCM proc),
 245             "Set the object procedure of @var{obj} to @var{proc}.\n"
 246             "@var{obj} must be either an entity or an operator.")
 247 #define FUNC_NAME s_scm_set_object_procedure_x
 248 {
 249   SCM_ASSERT (SCM_STRUCTP (obj)
 250               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 251                   || (SCM_I_ENTITYP (obj)
 252                       && !(SCM_OBJ_CLASS_FLAGS (obj)
 253                            & SCM_CLASSF_PURE_GENERIC))),
 254               obj,
 255               SCM_ARG1,
 256               FUNC_NAME);
 257   SCM_ASSERT (scm_valid_object_procedure_p (proc), proc, SCM_ARG2, FUNC_NAME);
 258   if (SCM_I_ENTITYP (obj))
 259     SCM_SET_ENTITY_PROCEDURE (obj, proc);
 260   else
 261     SCM_OPERATOR_CLASS (obj)->procedure = proc;
 262   return SCM_UNSPECIFIED;
 263 }
 264 #undef FUNC_NAME
 265
 266 #ifdef GUILE_DEBUG
 267 SCM_DEFINE (scm_object_procedure, "object-procedure", 1, 0, 0,
 268             (SCM obj),
 269             "Return the object procedure of @var{obj}. @var{obj} must be\n"
 270             "an entity or an operator.")
 271 #define FUNC_NAME s_scm_object_procedure
 272 {
 273   SCM_ASSERT (SCM_STRUCTP (obj)
 274               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 275                   || SCM_I_ENTITYP (obj)),
 276               obj, SCM_ARG1, FUNC_NAME);
 277   return (SCM_I_ENTITYP (obj)
 278           ? SCM_ENTITY_PROCEDURE (obj)
 279           : SCM_OPERATOR_CLASS (obj)->procedure);
 280 }
 281 #undef FUNC_NAME
 282 #endif /* GUILE_DEBUG */
 283
 284 /* The following procedures are not a part of Goops but a minimal
 285  * object system built upon structs.  They are here for those who
 286  * want to implement their own object system.
 287  */
 288
 289 SCM
 290 scm_i_make_class_object (SCM meta,
 291                          SCM layout_string,
 292                          unsigned long flags)
 293 {
 294   SCM c;
 295   SCM layout = scm_make_struct_layout (layout_string);
 296   c = scm_make_struct (meta,
 297                        SCM_INUM0,
 298                        scm_list_4 (layout, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 299   SCM_SET_CLASS_FLAGS (c, flags);
 300   return c;
 301 }
 302
 303 SCM_DEFINE (scm_make_class_object, "make-class-object", 2, 0, 0,
 304             (SCM metaclass, SCM layout),
 305             "Create a new class object of class @var{metaclass}, with the\n"
 306             "slot layout specified by @var{layout}.")
 307 #define FUNC_NAME s_scm_make_class_object
 308 {
 309   unsigned long flags = 0;
 310   SCM_VALIDATE_STRUCT (1, metaclass);
 311   SCM_VALIDATE_STRING (2, layout);
 312   if (scm_is_eq (metaclass, scm_metaclass_operator))
 313     flags = SCM_CLASSF_OPERATOR;
 314   return scm_i_make_class_object (metaclass, layout, flags);
 315 }
 316 #undef FUNC_NAME
 317
 318 SCM_DEFINE (scm_make_subclass_object, "make-subclass-object", 2, 0, 0,
 319             (SCM class, SCM layout),
 320             "Create a subclass object of @var{class}, with the slot layout\n"
 321             "specified by @var{layout}.")
 322 #define FUNC_NAME s_scm_make_subclass_object
 323 {
 324   SCM pl;
 325   SCM_VALIDATE_STRUCT (1, class);
 326   SCM_VALIDATE_STRING (2, layout);
 327   pl = SCM_PACK (SCM_STRUCT_DATA (class) [scm_vtable_index_layout]);
 328   pl = scm_symbol_to_string (pl);
 329   return scm_i_make_class_object (SCM_STRUCT_VTABLE (class),
 330                                   scm_string_append (scm_list_2 (pl, layout)),
 331                                   SCM_CLASS_FLAGS (class));
 332 }
 333 #undef FUNC_NAME
 334
 335 void
 336 scm_init_objects ()
 337 {
 338   SCM ms = scm_from_locale_string (SCM_METACLASS_STANDARD_LAYOUT);
 339   SCM mt = scm_make_vtable_vtable (ms, SCM_INUM0,
 340                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 341
 342   SCM os = scm_from_locale_string (SCM_METACLASS_OPERATOR_LAYOUT);
 343   SCM ot = scm_make_vtable_vtable (os, SCM_INUM0,
 344                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 345
 346   SCM es = scm_from_locale_string (SCM_ENTITY_LAYOUT);
 347   SCM el = scm_make_struct_layout (es);
 348   SCM et = scm_make_struct (mt, SCM_INUM0,
 349                             scm_list_4 (el, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 350
 351   scm_c_define ("<class>", mt);
 352   scm_metaclass_standard = mt;
 353   scm_c_define ("<operator-class>", ot);
 354   scm_metaclass_operator = ot;
 355   SCM_SET_CLASS_FLAGS (et, SCM_CLASSF_OPERATOR | SCM_CLASSF_ENTITY);
 356   SCM_SET_CLASS_DESTRUCTOR (et, scm_struct_free_entity);
 357   scm_c_define ("<entity>", et);
 358
 359 #include "libguile/objects.x"
 360 }
 361
 362 /*
 363   Local Variables:
 364   c-file-style: "gnu"
 365   End:
 366 */