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 != ENV */
 142       if (scm_is_null (SCM_CAR (z)) || scm_is_pair (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   return scm_eval_body (SCM_CDR (SCM_CMETHOD_CODE (cmethod)),
 165                         SCM_EXTEND_ENV (SCM_CAR (SCM_CMETHOD_CODE (cmethod)),
 166                                         args,
 167                                         SCM_CMETHOD_ENV (cmethod)));
 168 }
 169
 170 SCM
 171 scm_call_generic_0 (SCM gf)
 172 {
 173   return scm_apply_generic (gf, SCM_EOL);
 174 }
 175
 176 SCM
 177 scm_call_generic_1 (SCM gf, SCM a1)
 178 {
 179   return scm_apply_generic (gf, scm_list_1 (a1));
 180 }
 181
 182 SCM
 183 scm_call_generic_2 (SCM gf, SCM a1, SCM a2)
 184 {
 185   return scm_apply_generic (gf, scm_list_2 (a1, a2));
 186 }
 187
 188 SCM
 189 scm_call_generic_3 (SCM gf, SCM a1, SCM a2, SCM a3)
 190 {
 191   return scm_apply_generic (gf, scm_list_3 (a1, a2, a3));
 192 }
 193
 194 SCM_DEFINE (scm_entity_p, "entity?", 1, 0, 0,
 195             (SCM obj),
 196             "Return @code{#t} if @var{obj} is an entity.")
 197 #define FUNC_NAME s_scm_entity_p
 198 {
 199   return scm_from_bool(SCM_STRUCTP (obj) && SCM_I_ENTITYP (obj));
 200 }
 201 #undef FUNC_NAME
 202
 203 SCM_DEFINE (scm_operator_p, "operator?", 1, 0, 0,
 204             (SCM obj),
 205             "Return @code{#t} if @var{obj} is an operator.")
 206 #define FUNC_NAME s_scm_operator_p
 207 {
 208   return scm_from_bool(SCM_STRUCTP (obj)
 209                   && SCM_I_OPERATORP (obj)
 210                   && !SCM_I_ENTITYP (obj));
 211 }
 212 #undef FUNC_NAME
 213
 214 /* XXX - What code requires the object procedure to be only of certain
 215          types? */
 216
 217 SCM_DEFINE (scm_valid_object_procedure_p, "valid-object-procedure?", 1, 0, 0,
 218             (SCM proc),
 219             "Return @code{#t} iff @var{proc} is a procedure that can be used "
 220             "with @code{set-object-procedure}.  It is always valid to use "
 221             "a closure constructed by @code{lambda}.")
 222 #define FUNC_NAME s_scm_valid_object_procedure_p
 223 {
 224   if (SCM_IMP (proc))
 225     return SCM_BOOL_F;
 226   switch (SCM_TYP7 (proc))
 227     {
 228     default:
 229       return SCM_BOOL_F;
 230     case scm_tcs_closures:
 231     case scm_tc7_subr_1:
 232     case scm_tc7_subr_2:
 233     case scm_tc7_subr_3:
 234     case scm_tc7_lsubr_2:
 235       return SCM_BOOL_T;
 236     }
 237 }
 238 #undef FUNC_NAME
 239
 240 SCM_DEFINE (scm_set_object_procedure_x, "set-object-procedure!", 2, 0, 0,
 241             (SCM obj, SCM proc),
 242             "Set the object procedure of @var{obj} to @var{proc}.\n"
 243             "@var{obj} must be either an entity or an operator.")
 244 #define FUNC_NAME s_scm_set_object_procedure_x
 245 {
 246   SCM_ASSERT (SCM_STRUCTP (obj)
 247               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 248                   || (SCM_I_ENTITYP (obj)
 249                       && !(SCM_OBJ_CLASS_FLAGS (obj)
 250                            & SCM_CLASSF_PURE_GENERIC))),
 251               obj,
 252               SCM_ARG1,
 253               FUNC_NAME);
 254   SCM_ASSERT (scm_valid_object_procedure_p (proc), proc, SCM_ARG2, FUNC_NAME);
 255   if (SCM_I_ENTITYP (obj))
 256     SCM_SET_ENTITY_PROCEDURE (obj, proc);
 257   else
 258     SCM_OPERATOR_CLASS (obj)->procedure = proc;
 259   return SCM_UNSPECIFIED;
 260 }
 261 #undef FUNC_NAME
 262
 263 #ifdef GUILE_DEBUG
 264 SCM_DEFINE (scm_object_procedure, "object-procedure", 1, 0, 0,
 265             (SCM obj),
 266             "Return the object procedure of @var{obj}. @var{obj} must be\n"
 267             "an entity or an operator.")
 268 #define FUNC_NAME s_scm_object_procedure
 269 {
 270   SCM_ASSERT (SCM_STRUCTP (obj)
 271               && ((SCM_CLASS_FLAGS (obj) & SCM_CLASSF_OPERATOR)
 272                   || SCM_I_ENTITYP (obj)),
 273               obj, SCM_ARG1, FUNC_NAME);
 274   return (SCM_I_ENTITYP (obj)
 275           ? SCM_ENTITY_PROCEDURE (obj)
 276           : SCM_OPERATOR_CLASS (obj)->procedure);
 277 }
 278 #undef FUNC_NAME
 279 #endif /* GUILE_DEBUG */
 280
 281 /* The following procedures are not a part of Goops but a minimal
 282  * object system built upon structs.  They are here for those who
 283  * want to implement their own object system.
 284  */
 285
 286 SCM
 287 scm_i_make_class_object (SCM meta,
 288                          SCM layout_string,
 289                          unsigned long flags)
 290 {
 291   SCM c;
 292   SCM layout = scm_make_struct_layout (layout_string);
 293   c = scm_make_struct (meta,
 294                        SCM_INUM0,
 295                        scm_list_4 (layout, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 296   SCM_SET_CLASS_FLAGS (c, flags);
 297   return c;
 298 }
 299
 300 SCM_DEFINE (scm_make_class_object, "make-class-object", 2, 0, 0,
 301             (SCM metaclass, SCM layout),
 302             "Create a new class object of class @var{metaclass}, with the\n"
 303             "slot layout specified by @var{layout}.")
 304 #define FUNC_NAME s_scm_make_class_object
 305 {
 306   unsigned long flags = 0;
 307   SCM_VALIDATE_STRUCT (1, metaclass);
 308   SCM_VALIDATE_STRING (2, layout);
 309   if (scm_is_eq (metaclass, scm_metaclass_operator))
 310     flags = SCM_CLASSF_OPERATOR;
 311   return scm_i_make_class_object (metaclass, layout, flags);
 312 }
 313 #undef FUNC_NAME
 314
 315 SCM_DEFINE (scm_make_subclass_object, "make-subclass-object", 2, 0, 0,
 316             (SCM class, SCM layout),
 317             "Create a subclass object of @var{class}, with the slot layout\n"
 318             "specified by @var{layout}.")
 319 #define FUNC_NAME s_scm_make_subclass_object
 320 {
 321   SCM pl;
 322   SCM_VALIDATE_STRUCT (1, class);
 323   SCM_VALIDATE_STRING (2, layout);
 324   pl = SCM_PACK (SCM_STRUCT_DATA (class) [scm_vtable_index_layout]);
 325   pl = scm_symbol_to_string (pl);
 326   return scm_i_make_class_object (SCM_STRUCT_VTABLE (class),
 327                                   scm_string_append (scm_list_2 (pl, layout)),
 328                                   SCM_CLASS_FLAGS (class));
 329 }
 330 #undef FUNC_NAME
 331
 332 void
 333 scm_init_objects ()
 334 {
 335   SCM ms = scm_from_locale_string (SCM_METACLASS_STANDARD_LAYOUT);
 336   SCM mt = scm_make_vtable_vtable (ms, SCM_INUM0,
 337                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 338
 339   SCM os = scm_from_locale_string (SCM_METACLASS_OPERATOR_LAYOUT);
 340   SCM ot = scm_make_vtable_vtable (os, SCM_INUM0,
 341                                    scm_list_3 (SCM_BOOL_F, SCM_EOL, SCM_EOL));
 342
 343   SCM es = scm_from_locale_string (SCM_ENTITY_LAYOUT);
 344   SCM el = scm_make_struct_layout (es);
 345   SCM et = scm_make_struct (mt, SCM_INUM0,
 346                             scm_list_4 (el, SCM_BOOL_F, SCM_EOL, SCM_EOL));
 347
 348   scm_c_define ("<class>", mt);
 349   scm_metaclass_standard = mt;
 350   scm_c_define ("<operator-class>", ot);
 351   scm_metaclass_operator = ot;
 352   SCM_SET_CLASS_FLAGS (et, SCM_CLASSF_OPERATOR | SCM_CLASSF_ENTITY);
 353   scm_c_define ("<entity>", et);
 354
 355 #include "libguile/objects.x"
 356 }
 357
 358 /*
 359   Local Variables:
 360   c-file-style: "gnu"
 361   End:
 362 */