libguile/objects.c

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