libguile/objects.c

   1 /* Copyright (C) 1995,1996,1999,2000,2001, 2003 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program 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
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41
  42
  43 \f
  44
  45 /* This file and objects.h contains those minimal pieces of the Guile
  46  * Object Oriented Programming System which need to be included in
  47  * libguile.  See the comments in objects.h.
  48  */
  49
  50 #include "libguile/_scm.h"
  51
  52 #include "libguile/struct.h"
  53 #include "libguile/procprop.h"
  54 #include "libguile/chars.h"
  55 #include "libguile/keywords.h"
  56 #include "libguile/smob.h"
  57 #include "libguile/eval.h"
  58 #include "libguile/alist.h"
  59 #include "libguile/ports.h"
  60 #include "libguile/strings.h"
  61 #include "libguile/vectors.h"
  62
  63 #include "libguile/validate.h"
  64 #include "libguile/objects.h"
  65 \f
  66
  67 SCM scm_metaclass_standard;
  68 SCM scm_metaclass_operator;
  69
  70 /* These variables are filled in by the object system when loaded. */
  71 SCM scm_class_boolean, scm_class_char, scm_class_pair;
  72 SCM scm_class_procedure, scm_class_string, scm_class_symbol;
  73 SCM scm_class_procedure_with_setter, scm_class_primitive_generic;
  74 SCM scm_class_vector, scm_class_null;
  75 SCM scm_class_integer, scm_class_real, scm_class_complex;
  76 SCM scm_class_unknown;
  77
  78 SCM *scm_port_class = 0;
  79 SCM *scm_smob_class = 0;
  80
  81 SCM scm_no_applicable_method;
  82
  83 /* This function is used for efficient type dispatch.  */
  84 SCM_DEFINE (scm_class_of, "class-of", 1, 0, 0,
  85             (SCM x),
  86             "Return the class of @var{x}.")
  87 #define FUNC_NAME s_scm_class_of
  88 {
  89   switch (SCM_ITAG3 (x))
  90     {
  91     case scm_tc3_int_1:
  92     case scm_tc3_int_2:
  93       return scm_class_integer;
  94
  95     case scm_tc3_imm24:
  96       if (SCM_CHARP (x))
  97         return scm_class_char;
  98       else
  99         {
 100           switch (SCM_ISYMNUM (x))
 101             {
 102             case SCM_ISYMNUM (SCM_BOOL_F):
 103             case SCM_ISYMNUM (SCM_BOOL_T):
 104               return scm_class_boolean;
 105             case SCM_ISYMNUM (SCM_EOL):
 106               return scm_class_null;
 107             default:
 108               return scm_class_unknown;
 109             }
 110         }
 111
 112     case scm_tc3_cons:
 113       switch (SCM_TYP7 (x))
 114         {
 115         case scm_tcs_cons_nimcar:
 116           return scm_class_pair;
 117         case scm_tcs_closures:
 118           return scm_class_procedure;
 119         case scm_tc7_symbol:
 120           return scm_class_symbol;
 121         case scm_tc7_vector:
 122         case scm_tc7_wvect:
 123 #ifdef HAVE_ARRAYS
 124         case scm_tc7_bvect:
 125         case scm_tc7_byvect:
 126         case scm_tc7_svect:
 127         case scm_tc7_ivect:
 128         case scm_tc7_uvect:
 129         case scm_tc7_fvect:
 130         case scm_tc7_dvect:
 131         case scm_tc7_cvect:
 132 #endif
 133           return scm_class_vector;
 134         case scm_tc7_string:
 135           return scm_class_string;
 136         case scm_tc7_asubr:
 137         case scm_tc7_subr_0:
 138         case scm_tc7_subr_1:
 139         case scm_tc7_cxr:
 140         case scm_tc7_subr_3:
 141         case scm_tc7_subr_2:
 142         case scm_tc7_rpsubr:
 143         case scm_tc7_subr_1o:
 144         case scm_tc7_subr_2o:
 145         case scm_tc7_lsubr_2:
 146         case scm_tc7_lsubr:
 147           if (SCM_SUBR_GENERIC (x) && *SCM_SUBR_GENERIC (x))
 148             return scm_class_primitive_generic;
 149           else
 150             return scm_class_procedure;
 151         case scm_tc7_cclo:
 152           return scm_class_procedure;
 153         case scm_tc7_pws:
 154           return scm_class_procedure_with_setter;
 155
 156         case scm_tc7_smob:
 157           {
 158             scm_t_bits type = SCM_TYP16 (x);
 159             if (type != scm_tc16_port_with_ps)
 160               return scm_smob_class[SCM_TC2SMOBNUM (type)];
 161             x = SCM_PORT_WITH_PS_PORT (x);
 162             /* fall through to ports */
 163           }
 164         case scm_tc7_port:
 165           return scm_port_class[(SCM_WRTNG & SCM_CELL_WORD_0 (x)
 166                                  ? (SCM_RDNG & SCM_CELL_WORD_0 (x)
 167                                     ? SCM_INOUT_PCLASS_INDEX | SCM_PTOBNUM (x)
 168                                     : SCM_OUT_PCLASS_INDEX | SCM_PTOBNUM (x))
 169                                  : SCM_IN_PCLASS_INDEX | SCM_PTOBNUM (x))];
 170         case scm_tcs_struct:
 171           if (SCM_OBJ_CLASS_FLAGS (x) & SCM_CLASSF_GOOPS_VALID)
 172             return SCM_CLASS_OF (x);
 173           else if (SCM_OBJ_CLASS_FLAGS (x) & SCM_CLASSF_GOOPS)
 174             {
 175               /* Goops object */
 176               if (! SCM_FALSEP (SCM_OBJ_CLASS_REDEF (x)))
 177                 scm_change_object_class (x,
 178                                          SCM_CLASS_OF (x),         /* old */
 179                                          SCM_OBJ_CLASS_REDEF (x)); /* new */
 180               return SCM_CLASS_OF (x);
 181             }
 182           else
 183             {
 184               /* ordinary struct */
 185               SCM handle = scm_struct_create_handle (SCM_STRUCT_VTABLE (x));
 186               if (!SCM_FALSEP (SCM_STRUCT_TABLE_CLASS (SCM_CDR (handle))))
 187                 return SCM_STRUCT_TABLE_CLASS (SCM_CDR (handle));
 188               else
 189                 {
 190                   SCM name = SCM_STRUCT_TABLE_NAME (SCM_CDR (handle));
 191                   SCM class = scm_make_extended_class (!SCM_FALSEP (name)
 192                                                        ? SCM_SYMBOL_CHARS (name)
 193                                                        : 0,
 194                                                        SCM_I_OPERATORP (x));
 195                   SCM_SET_STRUCT_TABLE_CLASS (SCM_CDR (handle), class);
 196                   return class;
 197                 }
 198             }
 199         default:
 200           if (SCM_CONSP (x))
 201             return scm_class_pair;
 202           else
 203             return scm_class_unknown;
 204         }
 205
 206     case scm_tc3_struct:
 207     case scm_tc3_tc7_1:
 208     case scm_tc3_tc7_2:
 209     case scm_tc3_closure:
 210       /* Never reached */
 211       break;
 212     }
 213   return scm_class_unknown;
 214 }
 215 #undef FUNC_NAME
 216
 217 /* The cache argument for scm_mcache_lookup_cmethod has one of two possible
 218  * formats:
 219  *
 220  * Format #1:
 221  * (SCM_IM_DISPATCH ARGS N-SPECIALIZED
 222  *   #((TYPE1 ... ENV FORMALS FORM ...) ...)
 223  *   GF)
 224  *
 225  * Format #2:
 226  * (SCM_IM_HASH_DISPATCH ARGS N-SPECIALIZED HASHSET MASK
 227  *   #((TYPE1 ... ENV FORMALS FORM ...) ...)
 228  *   GF)
 229  *
 230  * ARGS is either a list of expressions, in which case they
 231  * are interpreted as the arguments of an application, or
 232  * a non-pair, which is interpreted as a single expression
 233  * yielding all arguments.
 234  *
 235  * SCM_IM_DISPATCH expressions in generic functions always
 236  * have ARGS = the symbol `args' or the iloc #@0-0.
 237  *
 238  * Need FORMALS in order to support varying arity.  This
 239  * also avoids the need for renaming of bindings.
 240  *
 241  * We should probably not complicate this mechanism by
 242  * introducing "optimizations" for getters and setters or
 243  * primitive methods.  Getters and setter will normally be
 244  * compiled into @slot-[ref|set!] or a procedure call.
 245  * They rely on the dispatch performed before executing
 246  * the code which contains them.
 247  *
 248  * We might want to use a more efficient representation of
 249  * this form in the future, perhaps after we have introduced
 250  * low-level support for syntax-case macros.
 251  */
 252
 253 SCM
 254 scm_mcache_lookup_cmethod (SCM cache, SCM args)
 255 {
 256   long i, n, end, mask;
 257   SCM ls, methods, z = SCM_CDDR (cache);
 258   n = SCM_INUM (SCM_CAR (z)); /* maximum number of specializers */
 259   methods = SCM_CADR (z);
 260
 261   if (SCM_INUMP (methods))
 262     {
 263       /* cache format #2: compute a hash value */
 264       long hashset = SCM_INUM (methods);
 265       long j = n;
 266       z = SCM_CDDR (z);
 267       mask = SCM_INUM (SCM_CAR (z));
 268       methods = SCM_CADR (z);
 269       i = 0;
 270       ls = args;
 271       if (!SCM_NULLP (ls))
 272         do
 273           {
 274             i += SCM_STRUCT_DATA (scm_class_of (SCM_CAR (ls)))
 275                  [scm_si_hashsets + hashset];
 276             ls = SCM_CDR (ls);
 277           }
 278         while (j-- && !SCM_NULLP (ls));
 279       i &= mask;
 280       end = i;
 281     }
 282   else /* SCM_VECTORP (methods) */
 283     {
 284       /* cache format #1: prepare for linear search */
 285       mask = -1;
 286       i = 0;
 287       end = SCM_VECTOR_LENGTH (methods);
 288     }
 289
 290   /* Search for match  */
 291   do
 292     {
 293       long j = n;
 294       z = SCM_VELTS (methods)[i];
 295       ls = args; /* list of arguments */
 296       if (!SCM_NULLP (ls))
 297         do
 298           {
 299             /* More arguments than specifiers => CLASS != ENV */
 300             if (! SCM_EQ_P (scm_class_of (SCM_CAR (ls)), SCM_CAR (z)))
 301               goto next_method;
 302             ls = SCM_CDR (ls);
 303             z = SCM_CDR (z);
 304           }
 305         while (j-- && !SCM_NULLP (ls));
 306       /* Fewer arguments than specifiers => CAR != ENV */
 307       if (SCM_NULLP (SCM_CAR (z)) || SCM_CONSP (SCM_CAR (z)))
 308         return z;
 309     next_method:
 310       i = (i + 1) & mask;
 311     } while (i != end);
 312   return SCM_BOOL_F;
 313 }
 314
 315 SCM
 316 scm_mcache_compute_cmethod (SCM cache, SCM args)
 317 {
 318   SCM cmethod = scm_mcache_lookup_cmethod (cache, args);
 319   if (SCM_FALSEP (cmethod))
 320     /* No match - memoize */
 321     return scm_memoize_method (cache, args);
 322   return cmethod;
 323 }
 324
 325 SCM
 326 scm_apply_generic (SCM gf, SCM args)
 327 {
 328   SCM cmethod = scm_mcache_compute_cmethod (SCM_ENTITY_PROCEDURE (gf), args);
 329   return scm_eval_body (SCM_CDR (SCM_CMETHOD_CODE (cmethod)),
 330                         SCM_EXTEND_ENV (SCM_CAR (SCM_CMETHOD_CODE (cmethod)),
 331                                         args,
 332                                         SCM_CMETHOD_ENV (cmethod)));
 333 }
 334
 335 SCM
 336 scm_call_generic_0 (SCM gf)
 337 {
 338   return scm_apply_generic (gf, SCM_EOL);
 339 }
 340
 341 SCM
 342 scm_call_generic_1 (SCM gf, SCM a1)
 343 {
 344   return scm_apply_generic (gf, scm_list_1 (a1));
 345 }
 346
 347 SCM
 348 scm_call_generic_2 (SCM gf, SCM a1, SCM a2)
 349 {
 350   return scm_apply_generic (gf, scm_list_2 (a1, a2));
 351 }
 352
 353 SCM
 354 scm_call_generic_3 (SCM gf, SCM a1, SCM a2, SCM a3)
 355 {
 356   return scm_apply_generic (gf, scm_list_3 (a1, a2, a3));
 357 }
 358
 359 SCM_DEFINE (scm_entity_p, "entity?", 1, 0, 0,
 360             (SCM obj),
 361             "Return @code{#t} if @var{obj} is an entity.")
 362 #define FUNC_NAME s_scm_entity_p
 363 {
 364   return SCM_BOOL(SCM_STRUCTP (obj) && SCM_I_ENTITYP (obj));
 365 }
 366 #undef FUNC_NAME
 367
 368 SCM_DEFINE (scm_operator_p, "operator?", 1, 0, 0,
 369             (SCM obj),
 370             "Return @code{#t} if @var{obj} is an operator.")
 371 #define FUNC_NAME s_scm_operator_p
 372 {
 373   return SCM_BOOL(SCM_STRUCTP (obj)
 374                   && SCM_I_OPERATORP (obj)
 375                   && !SCM_I_ENTITYP (obj));
 376 }
 377 #undef FUNC_NAME
 378
 379 /* XXX - What code requires the object procedure to be only of certain
 380          types? */
 381
 382 SCM_DEFINE (scm_valid_object_procedure_p, "valid-object-procedure?", 1, 0, 0,
 383             (SCM proc),
 384             "Return @code{#t} iff @var{proc} is a procedure that can be used "
 385             "with @code{set-object-procedure}.  It is always valid to use "
 386             "a closure constructed by @code{lambda}.")
 387 #define FUNC_NAME s_scm_valid_object_procedure_p
 388 {
 389   if (SCM_IMP (proc))
 390     return SCM_BOOL_F;
 391   switch (SCM_TYP7 (proc))
 392     {
 393     default:
 394       return SCM_BOOL_F;
 395     case scm_tcs_closures:
 396     case scm_tc7_subr_1:
 397     case scm_tc7_subr_2:
 398     case scm_tc7_subr_3:
 399     case scm_tc7_lsubr_2:
 400       return SCM_BOOL_T;
 401     }
 402 }
 403 #undef FUNC_NAME
 404
 405 SCM_DEFINE (scm_set_object_procedure_x, "set-object-procedure!", 2, 0, 0,
 406             (SCM obj, SCM proc),
 407             "Set the object procedure of @var{obj} to @var{proc}.\n"
 408             "@var{obj} must be either an entity or an operator.")
 409 #define FUNC_NAME s_scm_set_object_procedure_x
 410 {
 411   SCM_ASSERT (SCM_STRUCTP (obj)
 412               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 413                   || (SCM_I_ENTITYP (obj)
 414                       && !(SCM_OBJ_CLASS_FLAGS (obj)
 415                            & SCM_CLASSF_PURE_GENERIC))),
 416               obj,
 417               SCM_ARG1,
 418               FUNC_NAME);
 419   SCM_ASSERT (scm_valid_object_procedure_p (proc), proc, SCM_ARG2, FUNC_NAME);
 420   if (SCM_I_ENTITYP (obj))
 421     SCM_SET_ENTITY_PROCEDURE (obj, proc);
 422   else
 423     SCM_OPERATOR_CLASS (obj)->procedure = proc;
 424   return SCM_UNSPECIFIED;
 425 }
 426 #undef FUNC_NAME
 427
 428 #ifdef GUILE_DEBUG
 429 SCM_DEFINE (scm_object_procedure, "object-procedure", 1, 0, 0,
 430             (SCM obj),
 431             "Return the object procedure of @var{obj}. @var{obj} must be\n"
 432             "an entity or an operator.")
 433 #define FUNC_NAME s_scm_object_procedure
 434 {
 435   SCM_ASSERT (SCM_STRUCTP (obj)
 436               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 437                   || SCM_I_ENTITYP (obj)),
 438               obj, SCM_ARG1, FUNC_NAME);
 439   return (SCM_I_ENTITYP (obj)
 440           ? SCM_ENTITY_PROCEDURE (obj)
 441           : SCM_OPERATOR_CLASS (obj)->procedure);
 442 }
 443 #undef FUNC_NAME
 444 #endif /* GUILE_DEBUG */
 445
 446 /* The following procedures are not a part of Goops but a minimal
 447  * object system built upon structs.  They are here for those who
 448  * want to implement their own object system.
 449  */
 450
 451 SCM
 452 scm_i_make_class_object (SCM meta,
 453                          SCM layout_string,
 454                          unsigned long flags)
 455 {
 456   SCM c;
 457   SCM layout = scm_make_struct_layout (layout_string);
 458   c = scm_make_struct (meta,
 459                        SCM_INUM0,
 460                        scm_list_4 (layout, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 461   SCM_SET_CLASS_FLAGS (c, flags);
 462   return c;
 463 }
 464
 465 SCM_DEFINE (scm_make_class_object, "make-class-object", 2, 0, 0,
 466             (SCM metaclass, SCM layout),
 467             "Create a new class object of class @var{metaclass}, with the\n"
 468             "slot layout specified by @var{layout}.")
 469 #define FUNC_NAME s_scm_make_class_object
 470 {
 471   unsigned long flags = 0;
 472   SCM_VALIDATE_STRUCT (1, metaclass);
 473   SCM_VALIDATE_STRING (2, layout);
 474   if (SCM_EQ_P (metaclass, scm_metaclass_operator))
 475     flags = SCM_CLASSF_OPERATOR;
 476   return scm_i_make_class_object (metaclass, layout, flags);
 477 }
 478 #undef FUNC_NAME
 479
 480 SCM_DEFINE (scm_make_subclass_object, "make-subclass-object", 2, 0, 0,
 481             (SCM class, SCM layout),
 482             "Create a subclass object of @var{class}, with the slot layout\n"
 483             "specified by @var{layout}.")
 484 #define FUNC_NAME s_scm_make_subclass_object
 485 {
 486   SCM pl;
 487   SCM_VALIDATE_STRUCT (1, class);
 488   SCM_VALIDATE_STRING (2, layout);
 489   pl = SCM_PACK (SCM_STRUCT_DATA (class) [scm_vtable_index_layout]);
 490   /* Convert symbol->string */
 491   pl = scm_mem2string (SCM_SYMBOL_CHARS (pl), SCM_SYMBOL_LENGTH (pl));
 492   return scm_i_make_class_object (SCM_STRUCT_VTABLE (class),
 493                                   scm_string_append (scm_list_2 (pl, layout)),
 494                                   SCM_CLASS_FLAGS (class));
 495 }
 496 #undef FUNC_NAME
 497
 498 void
 499 scm_init_objects ()
 500 {
 501   SCM ms = scm_makfrom0str (SCM_METACLASS_STANDARD_LAYOUT);
 502   SCM mt = scm_make_vtable_vtable (ms, SCM_INUM0,
 503                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 504
 505   SCM os = scm_makfrom0str (SCM_METACLASS_OPERATOR_LAYOUT);
 506   SCM ot = scm_make_vtable_vtable (os, SCM_INUM0,
 507                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 508
 509   SCM es = scm_makfrom0str (SCM_ENTITY_LAYOUT);
 510   SCM el = scm_make_struct_layout (es);
 511   SCM et = scm_make_struct (mt, SCM_INUM0,
 512                             scm_list_4 (el, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 513
 514   scm_c_define ("<class>", mt);
 515   scm_metaclass_standard = mt;
 516   scm_c_define ("<operator-class>", ot);
 517   scm_metaclass_operator = ot;
 518   SCM_SET_CLASS_FLAGS (et, SCM_CLASSF_OPERATOR | SCM_CLASSF_ENTITY);
 519   SCM_SET_CLASS_DESTRUCTOR (et, scm_struct_free_entity);
 520   scm_c_define ("<entity>", et);
 521
 522 #include "libguile/objects.x"
 523 }
 524
 525 /*
 526   Local Variables:
 527   c-file-style: "gnu"
 528   End:
 529 */