summaryrefslogtreecommitdiffstats
path: root/struct.c
blob: 65f4eb7863ac02baa07a12695b144b09a4ee8004 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
/**********************************************************************

  struct.c -

  $Author$
  $Date$
  created at: Tue Mar 22 18:44:30 JST 1995

  Copyright (C) 1993-2003 Yukihiro Matsumoto

**********************************************************************/

#include "ruby.h"

VALUE rb_cStruct;

static VALUE struct_alloc _((VALUE));

VALUE
rb_struct_iv_get(c, name)
    VALUE c;
    char *name;
{
    ID id;

    id = rb_intern(name);
    for (;;) {
	if (rb_ivar_defined(c, id))
	    return rb_ivar_get(c, id);
	c = RCLASS(c)->super;
	if (c == 0 || c == rb_cStruct)
	    return Qnil;
    }
}

VALUE
rb_struct_s_members(klass)
    VALUE klass;
{
    VALUE members = rb_struct_iv_get(klass, "__members__");

    if (NIL_P(members)) {
	rb_bug("non-initialized struct");
    }
    return members;
}

VALUE
rb_struct_members(s)
    VALUE s;
{
    VALUE members = rb_struct_s_members(rb_obj_class(s));

    if (RSTRUCT(s)->len != RARRAY(members)->len) {
	rb_raise(rb_eTypeError, "struct size differs (%d required %d given)",
		 RARRAY(members)->len, RSTRUCT(s)->len);
    }
    return members;
}

static VALUE
rb_struct_s_members_m(klass)
    VALUE klass;
{
    VALUE members, ary;
    VALUE *p, *pend;

    members = rb_struct_s_members(klass);
    ary = rb_ary_new2(RARRAY(members)->len);
    p = RARRAY(members)->ptr; pend = p + RARRAY(members)->len;
    while (p < pend) {
	rb_ary_push(ary, rb_str_new2(rb_id2name(SYM2ID(*p))));
	p++;
    }

    return ary;
}

/*
 *  call-seq:
 *     struct.members    => array
 *  
 *  Returns an array of strings representing the names of the instance
 *  variables.
 *     
 *     Customer = Struct.new(:name, :address, :zip)
 *     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     joe.members   #=> ["name", "address", "zip"]
 */

static VALUE
rb_struct_members_m(obj)
    VALUE obj;
{
    return rb_struct_s_members_m(rb_obj_class(obj));
}

VALUE
rb_struct_getmember(obj, id)
    VALUE obj;
    ID id;
{
    VALUE members, slot;
    long i;

    members = rb_struct_members(obj);
    slot = ID2SYM(id);
    for (i=0; i<RARRAY(members)->len; i++) {
	if (RARRAY(members)->ptr[i] == slot) {
	    return RSTRUCT(obj)->ptr[i];
	}
    }
    rb_name_error(id, "%s is not struct member", rb_id2name(id));
    return Qnil;		/* not reached */
}

static VALUE
rb_struct_ref(obj)
    VALUE obj;
{
    return rb_struct_getmember(obj, rb_frame_last_func());
}

static VALUE rb_struct_ref0(obj) VALUE obj; {return RSTRUCT(obj)->ptr[0];}
static VALUE rb_struct_ref1(obj) VALUE obj; {return RSTRUCT(obj)->ptr[1];}
static VALUE rb_struct_ref2(obj) VALUE obj; {return RSTRUCT(obj)->ptr[2];}
static VALUE rb_struct_ref3(obj) VALUE obj; {return RSTRUCT(obj)->ptr[3];}
static VALUE rb_struct_ref4(obj) VALUE obj; {return RSTRUCT(obj)->ptr[4];}
static VALUE rb_struct_ref5(obj) VALUE obj; {return RSTRUCT(obj)->ptr[5];}
static VALUE rb_struct_ref6(obj) VALUE obj; {return RSTRUCT(obj)->ptr[6];}
static VALUE rb_struct_ref7(obj) VALUE obj; {return RSTRUCT(obj)->ptr[7];}
static VALUE rb_struct_ref8(obj) VALUE obj; {return RSTRUCT(obj)->ptr[8];}
static VALUE rb_struct_ref9(obj) VALUE obj; {return RSTRUCT(obj)->ptr[9];}

static VALUE (*ref_func[10])() = {
    rb_struct_ref0,
    rb_struct_ref1,
    rb_struct_ref2,
    rb_struct_ref3,
    rb_struct_ref4,
    rb_struct_ref5,
    rb_struct_ref6,
    rb_struct_ref7,
    rb_struct_ref8,
    rb_struct_ref9,
};

static void
rb_struct_modify(s)
    VALUE s;
{
    if (OBJ_FROZEN(s)) rb_error_frozen("Struct");
    if (!OBJ_TAINTED(s) && rb_safe_level() >= 4)
       rb_raise(rb_eSecurityError, "Insecure: can't modify Struct");
}

static VALUE
rb_struct_set(obj, val)
    VALUE obj, val;
{
    VALUE members, slot;
    long i;

    members = rb_struct_members(obj);
    rb_struct_modify(obj);
    for (i=0; i<RARRAY(members)->len; i++) {
	slot = RARRAY(members)->ptr[i];
	if (rb_id_attrset(SYM2ID(slot)) == rb_frame_last_func()) {
	    return RSTRUCT(obj)->ptr[i] = val;
	}
    }
    rb_name_error(rb_frame_last_func(), "`%s' is not a struct member",
		  rb_id2name(rb_frame_last_func()));
    return Qnil;		/* not reached */
}

static VALUE
make_struct(name, members, klass)
    VALUE name, members, klass;
{
    VALUE nstr;
    ID id;
    long i;

    OBJ_FREEZE(members);
    if (NIL_P(name)) {
	nstr = rb_class_new(klass);
	rb_make_metaclass(nstr, RBASIC(klass)->klass);
	rb_class_inherited(klass, nstr);
    }
    else {
	char *cname = StringValuePtr(name);
	id = rb_intern(cname);
	if (!rb_is_const_id(id)) {
	    rb_name_error(id, "identifier %s needs to be constant", cname);
	}
	if (rb_const_defined_at(klass, id)) {
	    rb_warn("redefining constant Struct::%s", cname);
	    rb_mod_remove_const(klass, ID2SYM(id));
	}
	nstr = rb_define_class_under(klass, cname, klass);
    }
    rb_iv_set(nstr, "__size__", LONG2NUM(RARRAY(members)->len));
    rb_iv_set(nstr, "__members__", members);

    rb_define_alloc_func(nstr, struct_alloc);
    rb_define_singleton_method(nstr, "new", rb_class_new_instance, -1);
    rb_define_singleton_method(nstr, "[]", rb_class_new_instance, -1);
    rb_define_singleton_method(nstr, "members", rb_struct_s_members_m, 0);
    for (i=0; i< RARRAY(members)->len; i++) {
	ID id = SYM2ID(RARRAY(members)->ptr[i]);
	if (i<10) {
	    rb_define_method_id(nstr, id, ref_func[i], 0);
	}
	else {
	    rb_define_method_id(nstr, id, rb_struct_ref, 0);
	}
	rb_define_method_id(nstr, rb_id_attrset(id), rb_struct_set, 1);
    }

    return nstr;
}

#ifdef HAVE_STDARG_PROTOTYPES
#include <stdarg.h>
#define va_init_list(a,b) va_start(a,b)
#else
#include <varargs.h>
#define va_init_list(a,b) va_start(a)
#endif

VALUE
#ifdef HAVE_STDARG_PROTOTYPES
rb_struct_define(const char *name, ...)
#else
rb_struct_define(name, va_alist)
    const char *name;
    va_dcl
#endif
{
    va_list ar;
    VALUE nm, ary;
    char *mem;

    if (!name) nm = Qnil;
    else nm = rb_str_new2(name);
    ary = rb_ary_new();

    va_init_list(ar, name);
    while (mem = va_arg(ar, char*)) {
	ID slot = rb_intern(mem);
	rb_ary_push(ary, ID2SYM(slot));
    }
    va_end(ar);

    return make_struct(nm, ary, rb_cStruct);
}

/*
 *  call-seq:
 *     Struct.new( [aString] [, aSym]+> )    => StructClass
 *     StructClass.new(arg, ...)             => obj
 *     StructClass[arg, ...]                 => obj
 *
 *  Creates a new class, named by <i>aString</i>, containing accessor
 *  methods for the given symbols. If the name <i>aString</i> is
 *  omitted, an anonymous structure class will be created. Otherwise,
 *  the name of this struct will appear as a constant in class
 *  <code>Struct</code>, so it must be unique for all
 *  <code>Struct</code>s in the system and should start with a capital
 *  letter. Assigning a structure class to a constant effectively gives
 *  the class the name of the constant.
 *     
 *  <code>Struct::new</code> returns a new <code>Class</code> object,
 *  which can then be used to create specific instances of the new
 *  structure. The number of actual parameters must be
 *  less than or equal to the number of attributes defined for this
 *  class; unset parameters default to \nil{}.  Passing too many
 *  parameters will raise an \E{ArgumentError}.
 *
 *  The remaining methods listed in this section (class and instance)
 *  are defined for this generated class. 
 *     
 *     # Create a structure with a name in Struct
 *     Struct.new("Customer", :name, :address)    #=> Struct::Customer
 *     Struct::Customer.new("Dave", "123 Main")   #=> #<Struct::Customer name="Dave", address="123 Main">
 *     
 *     # Create a structure named by its constant
 *     Customer = Struct.new(:name, :address)     #=> Customer
 *     Customer.new("Dave", "123 Main")           #=> #<Customer name="Dave", address="123 Main">
 */

static VALUE
rb_struct_s_def(argc, argv, klass)
    int argc;
    VALUE *argv;
    VALUE klass;
{
    VALUE name, rest;
    long i;
    VALUE st;
    ID id;

    rb_scan_args(argc, argv, "1*", &name, &rest);
    for (i=0; i<RARRAY(rest)->len; i++) {
	id = rb_to_id(RARRAY(rest)->ptr[i]);
	RARRAY(rest)->ptr[i] = ID2SYM(id);
    }
    if (!NIL_P(name)) {
	VALUE tmp = rb_check_string_type(name);

	if (NIL_P(tmp)) {
	    id = rb_to_id(name);
	    rb_ary_unshift(rest, ID2SYM(id));
	    name = Qnil;
	}
    }
    st = make_struct(name, rest, klass);
    if (rb_block_given_p()) {
	rb_mod_module_eval(0, 0, st);
    }

    return st;
}

/*
 */

static VALUE
rb_struct_initialize(self, values)
    VALUE self, values;
{
    VALUE klass = rb_obj_class(self);
    VALUE size;
    long n;

    rb_struct_modify(self);
    size = rb_struct_iv_get(klass, "__size__");
    n = FIX2LONG(size);
    if (n < RARRAY(values)->len) {
	rb_raise(rb_eArgError, "struct size differs");
    }
    MEMCPY(RSTRUCT(self)->ptr, RARRAY(values)->ptr, VALUE, RARRAY(values)->len);
    if (n > RARRAY(values)->len) {
	rb_mem_clear(RSTRUCT(self)->ptr+RARRAY(values)->len,
		     n-RARRAY(values)->len);
    }
    return Qnil;
}

static VALUE
struct_alloc(klass)
    VALUE klass;
{
    VALUE size;
    long n;
    NEWOBJ(st, struct RStruct);
    OBJSETUP(st, klass, T_STRUCT);

    size = rb_struct_iv_get(klass, "__size__");
    n = FIX2LONG(size);

    st->ptr = ALLOC_N(VALUE, n);
    rb_mem_clear(st->ptr, n);
    st->len = n;

    return (VALUE)st;
}

VALUE
rb_struct_alloc(klass, values)
    VALUE klass, values;
{
    return rb_class_new_instance(RARRAY(values)->len, RARRAY(values)->ptr, klass);
}

VALUE
#ifdef HAVE_STDARG_PROTOTYPES
rb_struct_new(VALUE klass, ...)
#else
rb_struct_new(klass, va_alist)
    VALUE klass;
    va_dcl
#endif
{
    VALUE sz, *mem;
    long size, i;
    va_list args;

    sz = rb_struct_iv_get(klass, "__size__");
    size = FIX2LONG(sz); 
    mem = ALLOCA_N(VALUE, size);
    va_init_list(args, klass);
    for (i=0; i<size; i++) {
	mem[i] = va_arg(args, VALUE);
    }
    va_end(args);

    return rb_class_new_instance(size, mem, klass);
}

/*
 *  call-seq:
 *     struct.each {|obj| block }  => struct
 *  
 *  Calls <i>block</i> once for each instance variable, passing the
 *  value as a parameter.
 *     
 *     Customer = Struct.new(:name, :address, :zip)
 *     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     joe.each {|x| puts(x) }
 *     
 *  <em>produces:</em>
 *     
 *     Joe Smith
 *     123 Maple, Anytown NC
 *     12345
 */

static VALUE
rb_struct_each(s)
    VALUE s;
{
    long i;

    for (i=0; i<RSTRUCT(s)->len; i++) {
	rb_yield(RSTRUCT(s)->ptr[i]);
    }
    return s;
}

/*
 *  call-seq:
 *     struct.each_pair {|sym, obj| block }     => struct
 *  
 *  Calls <i>block</i> once for each instance variable, passing the name
 *  (as a symbol) and the value as parameters.
 *     
 *     Customer = Struct.new(:name, :address, :zip)
 *     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     joe.each_pair {|name, value| puts("#{name} => #{value}") }
 *     
 *  <em>produces:</em>
 *     
 *     name => Joe Smith
 *     address => 123 Maple, Anytown NC
 *     zip => 12345
 */

static VALUE
rb_struct_each_pair(s)
    VALUE s;
{
    VALUE members;
    long i;

    members = rb_struct_members(s);
    for (i=0; i<RSTRUCT(s)->len; i++) {
	rb_yield_values(2, rb_ary_entry(members, i), RSTRUCT(s)->ptr[i]);
    }
    return s;
}

static VALUE
inspect_struct(s)
    VALUE s;
{
    char *cname = rb_class2name(rb_obj_class(s));
    VALUE str, members;
    long i;

    members = rb_struct_members(s);
    str = rb_str_buf_new2("#<struct ");
    rb_str_cat2(str, cname);
    rb_str_cat2(str, " ");
    for (i=0; i<RSTRUCT(s)->len; i++) {
	VALUE str2, slot;
	char *p;

	if (i > 0) {
	    rb_str_cat2(str, ", ");
	}
	slot = RARRAY(members)->ptr[i];
	p = rb_id2name(SYM2ID(slot));
	rb_str_cat2(str, p);
	rb_str_cat2(str, "=");
	str2 = rb_inspect(RSTRUCT(s)->ptr[i]);
	rb_str_append(str, str2);
    }
    rb_str_cat2(str, ">");
    OBJ_INFECT(str, s);

    return str;
}

/*
 * call-seq:
 *   struct.to_s      => string
 *   struct.inspect   => string
 *
 * Describe the contents of this struct in a string.
 */

static VALUE
rb_struct_inspect(s)
    VALUE s;
{
    if (rb_inspecting_p(s)) {
	char *cname = rb_class2name(rb_obj_class(s));
	VALUE str = rb_str_new(0, strlen(cname) + 15);

	sprintf(RSTRING(str)->ptr, "#<struct %s:...>", cname);
	RSTRING(str)->len = strlen(RSTRING(str)->ptr);
	return str;
    }
    return rb_protect_inspect(inspect_struct, s, 0);
}

/*
 *  call-seq:
 *     struct.to_a     => array
 *     struct.values   => array
 *  
 *  Returns the values for this instance as an array.
 *     
 *     Customer = Struct.new(:name, :address, :zip)
 *     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     joe.to_a[1]   #=> "123 Maple, Anytown NC"
 */

static VALUE
rb_struct_to_a(s)
    VALUE s;
{
    return rb_ary_new4(RSTRUCT(s)->len, RSTRUCT(s)->ptr);
}

/* :nodoc: */
static VALUE
rb_struct_init_copy(copy, s)
    VALUE copy, s;
{
    if (copy == s) return copy;
    rb_check_frozen(copy);
    if (!rb_obj_is_instance_of(s, rb_obj_class(copy))) {
	rb_raise(rb_eTypeError, "wrong argument class");
    }
    RSTRUCT(copy)->ptr = ALLOC_N(VALUE, RSTRUCT(s)->len);
    RSTRUCT(copy)->len = RSTRUCT(s)->len;
    MEMCPY(RSTRUCT(copy)->ptr, RSTRUCT(s)->ptr, VALUE, RSTRUCT(copy)->len);

    return copy;
}

static VALUE
rb_struct_aref_id(s, id)
    VALUE s;
    ID id;
{
    VALUE members;
    long i, len;

    members = rb_struct_members(s);
    len = RARRAY(members)->len;
    for (i=0; i<len; i++) {
	if (SYM2ID(RARRAY(members)->ptr[i]) == id) {
	    return RSTRUCT(s)->ptr[i];
	}
    }
    rb_name_error(id, "no member '%s' in struct", rb_id2name(id));
    return Qnil;		/* not reached */
}

/*
 *  call-seq:
 *     struct[symbol]    => anObject
 *     struct[fixnum]    => anObject 
 *  
 *  Attribute Reference---Returns the value of the instance variable
 *  named by <i>symbol</i>, or indexed (0..length-1) by
 *  <i>fixnum</i>. Will raise <code>NameError</code> if the named
 *  variable does not exist, or <code>IndexError</code> if the index is
 *  out of range.
 *     
 *     Customer = Struct.new(:name, :address, :zip)
 *     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     
 *     joe["name"]   #=> "Joe Smith"
 *     joe[:name]    #=> "Joe Smith"
 *     joe[0]        #=> "Joe Smith"
 */

VALUE
rb_struct_aref(s, idx)
    VALUE s, idx;
{
    long i;

    if (TYPE(idx) == T_STRING || TYPE(idx) == T_SYMBOL) {
	return rb_struct_aref_id(s, rb_to_id(idx));
    }

    i = NUM2LONG(idx);
    if (i < 0) i = RSTRUCT(s)->len + i;
    if (i < 0)
        rb_raise(rb_eIndexError, "offset %ld too small for struct(size:%ld)",
		 i, RSTRUCT(s)->len);
    if (RSTRUCT(s)->len <= i)
        rb_raise(rb_eIndexError, "offset %ld too large for struct(size:%ld)",
		 i, RSTRUCT(s)->len);
    return RSTRUCT(s)->ptr[i];
}

static VALUE
rb_struct_aset_id(s, id, val)
    VALUE s, val;
    ID id;
{
    VALUE members;
    long i, len;

    members = rb_struct_members(s);
    rb_struct_modify(s);
    len = RARRAY(members)->len;
    if (RSTRUCT(s)->len != RARRAY(members)->len) {
	rb_raise(rb_eTypeError, "struct size differs (%d required %d given)",
		 RARRAY(members)->len, RSTRUCT(s)->len);
    }
    for (i=0; i<len; i++) {
	if (SYM2ID(RARRAY(members)->ptr[i]) == id) {
	    RSTRUCT(s)->ptr[i] = val;
	    return val;
	}
    }
    rb_name_error(id, "no member '%s' in struct", rb_id2name(id));
}

/*
 *  call-seq:
 *     struct[symbol] = obj    => obj
 *     struct[fixnum] = obj    => obj
 *  
 *  Attribute Assignment---Assigns to the instance variable named by
 *  <i>symbol</i> or <i>fixnum</i> the value <i>obj</i> and
 *  returns it. Will raise a <code>NameError</code> if the named
 *  variable does not exist, or an <code>IndexError</code> if the index
 *  is out of range.
 *     
 *     Customer = Struct.new(:name, :address, :zip)
 *     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     
 *     joe["name"] = "Luke"
 *     joe[:zip]   = "90210"
 *     
 *     joe.name   #=> "Luke"
 *     joe.zip    #=> "90210"
 */

VALUE
rb_struct_aset(s, idx, val)
    VALUE s, idx, val;
{
    long i;

    if (TYPE(idx) == T_STRING || TYPE(idx) == T_SYMBOL) {
	return rb_struct_aset_id(s, rb_to_id(idx), val);
    }

    i = NUM2LONG(idx);
    if (i < 0) i = RSTRUCT(s)->len + i;
    if (i < 0) {
        rb_raise(rb_eIndexError, "offset %ld too small for struct(size:%ld)",
		 i, RSTRUCT(s)->len);
    }
    if (RSTRUCT(s)->len <= i) {
        rb_raise(rb_eIndexError, "offset %ld too large for struct(size:%ld)",
		 i, RSTRUCT(s)->len);
    }
    rb_struct_modify(s);
    return RSTRUCT(s)->ptr[i] = val;
}

static VALUE struct_entry _((VALUE, long));
static VALUE
struct_entry(s, n)
    VALUE s;
    long n;
{
    return rb_struct_aref(s, LONG2NUM(n));
}

/* 
 * call-seq:
 *   struct.values_at(selector,... )  => an_array
 *
 *   Returns an array containing the elements in
 *   _self_ corresponding to the given selector(s). The selectors
 *   may be either integer indices or ranges. 
 *   See also </code>.select<code>.
 * 
 *      a = %w{ a b c d e f }
 *      a.values_at(1, 3, 5)
 *      a.values_at(1, 3, 5, 7)
 *      a.values_at(-1, -3, -5, -7)
 *      a.values_at(1..3, 2...5)
 */

static VALUE
rb_struct_values_at(argc, argv, s)
    int argc;
    VALUE *argv;
    VALUE s;
{
    return rb_get_values_at(s, RSTRUCT(s)->len, argc, argv, struct_entry);
}

/*
 *  call-seq:
 *     struct.select(fixnum, ... )   => array
 *     struct.select {|i| block }    => array
 *  
 *  The first form returns an array containing the elements in
 *  <i>struct</i> corresponding to the given indices. The second
 *  form invokes the block passing in successive elements from
 *  <i>struct</i>, returning an array containing those elements
 *  for which the block returns a true value (equivalent to
 *  <code>Enumerable#select</code>).
 *     
 *     Lots = Struct.new(:a, :b, :c, :d, :e, :f)
 *     l = Lots.new(11, 22, 33, 44, 55, 66)
 *     l.select(1, 3, 5)               #=> [22, 44, 66]
 *     l.select(0, 2, 4)               #=> [11, 33, 55]
 *     l.select(-1, -3, -5)            #=> [66, 44, 22]
 *     l.select {|v| (v % 2).zero? }   #=> [22, 44, 66]
 */

static VALUE
rb_struct_select(argc, argv, s)
    int argc;
    VALUE *argv;
    VALUE s;
{
    VALUE result;
    long i;

    if (argc > 0) {
	rb_raise(rb_eArgError, "wrong number of arguments (%d for 0)", argc);
    }
    result = rb_ary_new();
    for (i = 0; i < RSTRUCT(s)->len; i++) {
	if (RTEST(rb_yield(RSTRUCT(s)->ptr[i]))) {
	    rb_ary_push(result, RSTRUCT(s)->ptr[i]);
	}
    }

    return result;
}

/*
 *  call-seq:
 *     struct == other_struct     => true or false
 *  
 *  Equality---Returns <code>true</code> if <i>other_struct</i> is
 *  equal to this one: they must be of the same class as generated by
 *  <code>Struct::new</code>, and the values of all instance variables
 *  must be equal (according to <code>Object#==</code>).
 *     
 *     Customer = Struct.new(:name, :address, :zip)
 *     joe   = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     joejr = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     jane  = Customer.new("Jane Doe", "456 Elm, Anytown NC", 12345)
 *     joe == joejr   #=> true
 *     joe == jane    #=> false
 */

static VALUE
rb_struct_equal(s, s2)
    VALUE s, s2;
{
    long i;

    if (s == s2) return Qtrue;
    if (TYPE(s2) != T_STRUCT) return Qfalse;
    if (rb_obj_class(s) != rb_obj_class(s2)) return Qfalse;
    if (RSTRUCT(s)->len != RSTRUCT(s2)->len) {
	rb_bug("inconsistent struct"); /* should never happen */
    }

    for (i=0; i<RSTRUCT(s)->len; i++) {
	if (!rb_equal(RSTRUCT(s)->ptr[i], RSTRUCT(s2)->ptr[i])) return Qfalse;
    }
    return Qtrue;
}

/*
 * call-seq:
 *   struct.hash   => fixnum
 *
 * Return a hash value based on this struct's contents.
 */

static VALUE
rb_struct_hash(s)
    VALUE s;
{
    long i, h;
    VALUE n;

    h = rb_hash(rb_obj_class(s));
    for (i = 0; i < RSTRUCT(s)->len; i++) {
	h = (h << 1) | (h<0 ? 1 : 0);
	n = rb_hash(RSTRUCT(s)->ptr[i]);
	h ^= NUM2LONG(n);
    }
    return LONG2FIX(h);
}

/*
 * code-seq:
 *   struct.eql?(other)   => true or false
 *
 * Two structures are equal if they are the same object, or if all their
 * fields are equal (using <code>eql?</code>).
 */

static VALUE
rb_struct_eql(s, s2)
    VALUE s, s2;
{
    long i;

    if (s == s2) return Qtrue;
    if (TYPE(s2) != T_STRUCT) return Qfalse;
    if (rb_obj_class(s) != rb_obj_class(s2)) return Qfalse;
    if (RSTRUCT(s)->len != RSTRUCT(s2)->len) {
	rb_bug("inconsistent struct"); /* should never happen */
    }

    for (i=0; i<RSTRUCT(s)->len; i++) {
	if (!rb_eql(RSTRUCT(s)->ptr[i], RSTRUCT(s2)->ptr[i])) return Qfalse;
    }
    return Qtrue;
}

/*
 *  call-seq:
 *     struct.length    => fixnum
 *     struct.size      => fixnum
 *  
 *  Returns the number of instance variables.
 *     
 *     Customer = Struct.new(:name, :address, :zip)
 *     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     joe.length   #=> 3
 */

static VALUE
rb_struct_size(s)
    VALUE s;
{
    return LONG2FIX(RSTRUCT(s)->len);
}

/*
 *  A <code>Struct</code> is a convenient way to bundle a number of
 *  attributes together, using accessor methods, without having to write
 *  an explicit class.
 *     
 *  The <code>Struct</code> class is a generator of specific classes,
 *  each one of which is defined to hold a set of variables and their
 *  accessors. In these examples, we'll call the generated class
 *  ``<i>Customer</i>Class,'' and we'll show an example instance of that
 *  class as ``<i>Customer</i>Inst.''
 *     
 *  In the descriptions that follow, the parameter <i>symbol</i> refers
 *  to a symbol, which is either a quoted string or a
 *  <code>Symbol</code> (such as <code>:name</code>).
 */
void
Init_Struct()
{
    rb_cStruct = rb_define_class("Struct", rb_cObject);
    rb_include_module(rb_cStruct, rb_mEnumerable);

    rb_undef_alloc_func(rb_cStruct);
    rb_define_singleton_method(rb_cStruct, "new", rb_struct_s_def, -1);

    rb_define_method(rb_cStruct, "initialize", rb_struct_initialize, -2);
    rb_define_method(rb_cStruct, "initialize_copy", rb_struct_init_copy, 1);

    rb_define_method(rb_cStruct, "==", rb_struct_equal, 1);
    rb_define_method(rb_cStruct, "eql?", rb_struct_eql, 1);
    rb_define_method(rb_cStruct, "hash", rb_struct_hash, 0);

    rb_define_method(rb_cStruct, "to_s", rb_struct_inspect, 0);
    rb_define_method(rb_cStruct, "inspect", rb_struct_inspect, 0);
    rb_define_method(rb_cStruct, "to_a", rb_struct_to_a, 0);
    rb_define_method(rb_cStruct, "values", rb_struct_to_a, 0);
    rb_define_method(rb_cStruct, "size", rb_struct_size, 0);
    rb_define_method(rb_cStruct, "length", rb_struct_size, 0);

    rb_define_method(rb_cStruct, "each", rb_struct_each, 0);
    rb_define_method(rb_cStruct, "each_pair", rb_struct_each_pair, 0);
    rb_define_method(rb_cStruct, "[]", rb_struct_aref, 1);
    rb_define_method(rb_cStruct, "[]=", rb_struct_aset, 2);
    rb_define_method(rb_cStruct, "select", rb_struct_select, -1);
    rb_define_method(rb_cStruct, "values_at", rb_struct_values_at, -1);

    rb_define_method(rb_cStruct, "members", rb_struct_members_m, 0);
}