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 or `no-method' */
 142       if (!scm_is_pair (z)
 143           || (!SCM_CLASSP (SCM_CAR (z)) && !scm_is_symbol (SCM_CAR (z))))
 144         return z;
 145     next_method:
 146       i = (i + 1) & mask;
 147     } while (i != end);
 148   return SCM_BOOL_F;
 149 }
 150
 151 SCM
 152 scm_mcache_compute_cmethod (SCM cache, SCM args)
 153 {
 154   SCM cmethod = scm_mcache_lookup_cmethod (cache, args);
 155   if (scm_is_false (cmethod))
 156     /* No match - memoize */
 157     return scm_memoize_method (cache, args);
 158   return cmethod;
 159 }
 160
 161 SCM
 162 scm_apply_generic (SCM gf, SCM args)
 163 {
 164   SCM cmethod = scm_mcache_compute_cmethod (SCM_ENTITY_PROCEDURE (gf), args);
 165   if (scm_is_pair (cmethod))
 166     return scm_eval_body (SCM_CDR (SCM_CMETHOD_CODE (cmethod)),
 167                           SCM_EXTEND_ENV (SCM_CAR (SCM_CMETHOD_CODE (cmethod)),
 168                                           args,
 169                                           SCM_CMETHOD_ENV (cmethod)));
 170   else
 171     return scm_apply (cmethod, args, SCM_EOL);
 172 }
 173
 174 SCM
 175 scm_call_generic_0 (SCM gf)
 176 {
 177   return scm_apply_generic (gf, SCM_EOL);
 178 }
 179
 180 SCM
 181 scm_call_generic_1 (SCM gf, SCM a1)
 182 {
 183   return scm_apply_generic (gf, scm_list_1 (a1));
 184 }
 185
 186 SCM
 187 scm_call_generic_2 (SCM gf, SCM a1, SCM a2)
 188 {
 189   return scm_apply_generic (gf, scm_list_2 (a1, a2));
 190 }
 191
 192 SCM
 193 scm_call_generic_3 (SCM gf, SCM a1, SCM a2, SCM a3)
 194 {
 195   return scm_apply_generic (gf, scm_list_3 (a1, a2, a3));
 196 }
 197
 198 SCM_DEFINE (scm_entity_p, "entity?", 1, 0, 0,
 199             (SCM obj),
 200             "Return @code{#t} if @var{obj} is an entity.")
 201 #define FUNC_NAME s_scm_entity_p
 202 {
 203   return scm_from_bool(SCM_STRUCTP (obj) && SCM_I_ENTITYP (obj));
 204 }
 205 #undef FUNC_NAME
 206
 207 SCM_DEFINE (scm_operator_p, "operator?", 1, 0, 0,
 208             (SCM obj),
 209             "Return @code{#t} if @var{obj} is an operator.")
 210 #define FUNC_NAME s_scm_operator_p
 211 {
 212   return scm_from_bool(SCM_STRUCTP (obj)
 213                   && SCM_I_OPERATORP (obj)
 214                   && !SCM_I_ENTITYP (obj));
 215 }
 216 #undef FUNC_NAME
 217
 218 /* XXX - What code requires the object procedure to be only of certain
 219          types? */
 220
 221 SCM_DEFINE (scm_valid_object_procedure_p, "valid-object-procedure?", 1, 0, 0,
 222             (SCM proc),
 223             "Return @code{#t} iff @var{proc} is a procedure that can be used "
 224             "with @code{set-object-procedure}.  It is always valid to use "
 225             "a closure constructed by @code{lambda}.")
 226 #define FUNC_NAME s_scm_valid_object_procedure_p
 227 {
 228   if (SCM_IMP (proc))
 229     return SCM_BOOL_F;
 230   switch (SCM_TYP7 (proc))
 231     {
 232     default:
 233       return SCM_BOOL_F;
 234     case scm_tcs_closures:
 235     case scm_tc7_subr_1:
 236     case scm_tc7_subr_2:
 237     case scm_tc7_subr_3:
 238     case scm_tc7_lsubr_2:
 239       return SCM_BOOL_T;
 240     }
 241 }
 242 #undef FUNC_NAME
 243
 244 SCM_DEFINE (scm_set_object_procedure_x, "set-object-procedure!", 2, 0, 0,
 245             (SCM obj, SCM proc),
 246             "Set the object procedure of @var{obj} to @var{proc}.\n"
 247             "@var{obj} must be either an entity or an operator.")
 248 #define FUNC_NAME s_scm_set_object_procedure_x
 249 {
 250   SCM_ASSERT (SCM_STRUCTP (obj)
 251               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 252                   || (SCM_I_ENTITYP (obj)
 253                       && !(SCM_OBJ_CLASS_FLAGS (obj)
 254                            & SCM_CLASSF_PURE_GENERIC))),
 255               obj,
 256               SCM_ARG1,
 257               FUNC_NAME);
 258   SCM_ASSERT (scm_valid_object_procedure_p (proc), proc, SCM_ARG2, FUNC_NAME);
 259   if (SCM_I_ENTITYP (obj))
 260     SCM_SET_ENTITY_PROCEDURE (obj, proc);
 261   else
 262     SCM_OPERATOR_CLASS (obj)->procedure = proc;
 263   return SCM_UNSPECIFIED;
 264 }
 265 #undef FUNC_NAME
 266
 267 #ifdef GUILE_DEBUG
 268 SCM_DEFINE (scm_object_procedure, "object-procedure", 1, 0, 0,
 269             (SCM obj),
 270             "Return the object procedure of @var{obj}. @var{obj} must be\n"
 271             "an entity or an operator.")
 272 #define FUNC_NAME s_scm_object_procedure
 273 {
 274   SCM_ASSERT (SCM_STRUCTP (obj)
 275               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 276                   || SCM_I_ENTITYP (obj)),
 277               obj, SCM_ARG1, FUNC_NAME);
 278   return (SCM_I_ENTITYP (obj)
 279           ? SCM_ENTITY_PROCEDURE (obj)
 280           : SCM_OPERATOR_CLASS (obj)->procedure);
 281 }
 282 #undef FUNC_NAME
 283 #endif /* GUILE_DEBUG */
 284
 285 /* The following procedures are not a part of Goops but a minimal
 286  * object system built upon structs.  They are here for those who
 287  * want to implement their own object system.
 288  */
 289
 290 SCM
 291 scm_i_make_class_object (SCM meta,
 292                          SCM layout_string,
 293                          unsigned long flags)
 294 {
 295   SCM c;
 296   SCM layout = scm_make_struct_layout (layout_string);
 297   c = scm_make_struct (meta,
 298                        SCM_INUM0,
 299                        scm_list_4 (layout, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 300   SCM_SET_CLASS_FLAGS (c, flags);
 301   return c;
 302 }
 303
 304 SCM_DEFINE (scm_make_class_object, "make-class-object", 2, 0, 0,
 305             (SCM metaclass, SCM layout),
 306             "Create a new class object of class @var{metaclass}, with the\n"
 307             "slot layout specified by @var{layout}.")
 308 #define FUNC_NAME s_scm_make_class_object
 309 {
 310   unsigned long flags = 0;
 311   SCM_VALIDATE_STRUCT (1, metaclass);
 312   SCM_VALIDATE_STRING (2, layout);
 313   if (scm_is_eq (metaclass, scm_metaclass_operator))
 314     flags = SCM_CLASSF_OPERATOR;
 315   return scm_i_make_class_object (metaclass, layout, flags);
 316 }
 317 #undef FUNC_NAME
 318
 319 SCM_DEFINE (scm_make_subclass_object, "make-subclass-object", 2, 0, 0,
 320             (SCM class, SCM layout),
 321             "Create a subclass object of @var{class}, with the slot layout\n"
 322             "specified by @var{layout}.")
 323 #define FUNC_NAME s_scm_make_subclass_object
 324 {
 325   SCM pl;
 326   SCM_VALIDATE_STRUCT (1, class);
 327   SCM_VALIDATE_STRING (2, layout);
 328   pl = SCM_PACK (SCM_STRUCT_DATA (class) [scm_vtable_index_layout]);
 329   pl = scm_symbol_to_string (pl);
 330   return scm_i_make_class_object (SCM_STRUCT_VTABLE (class),
 331                                   scm_string_append (scm_list_2 (pl, layout)),
 332                                   SCM_CLASS_FLAGS (class));
 333 }
 334 #undef FUNC_NAME
 335
 336 void
 337 scm_init_objects ()
 338 {
 339   SCM ms = scm_from_locale_string (SCM_METACLASS_STANDARD_LAYOUT);
 340   SCM mt = scm_make_vtable_vtable (ms, SCM_INUM0,
 341                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 342
 343   SCM os = scm_from_locale_string (SCM_METACLASS_OPERATOR_LAYOUT);
 344   SCM ot = scm_make_vtable_vtable (os, SCM_INUM0,
 345                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 346
 347   SCM es = scm_from_locale_string (SCM_ENTITY_LAYOUT);
 348   SCM el = scm_make_struct_layout (es);
 349   SCM et = scm_make_struct (mt, SCM_INUM0,
 350                             scm_list_4 (el, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 351
 352   scm_c_define ("<class>", mt);
 353   scm_metaclass_standard = mt;
 354   scm_c_define ("<operator-class>", ot);
 355   scm_metaclass_operator = ot;
 356   SCM_SET_CLASS_FLAGS (et, SCM_CLASSF_OPERATOR | SCM_CLASSF_ENTITY);
 357   SCM_SET_CLASS_DESTRUCTOR (et, scm_struct_free_entity);
 358   scm_c_define ("<entity>", et);
 359
 360 #include "libguile/objects.x"
 361 }
 362
 363 /*
 364   Local Variables:
 365   c-file-style: "gnu"
 366   End:
 367 */