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1 | package Class::Struct; |
2 | |
3 | ## See POD after __END__ |
4 | |
5 | require 5.002; |
6 | |
7 | use strict; |
8 | use vars qw(@ISA @EXPORT); |
9 | |
10 | use Carp; |
11 | |
12 | require Exporter; |
13 | @ISA = qw(Exporter); |
14 | @EXPORT = qw(struct); |
15 | |
16 | ## Tested on 5.002 and 5.003 without class membership tests: |
17 | my $CHECK_CLASS_MEMBERSHIP = ($] >= 5.003_95); |
18 | |
19 | my $print = 0; |
20 | sub printem { |
21 | if (@_) { $print = shift } |
22 | else { $print++ } |
23 | } |
24 | |
25 | { |
26 | package Class::Struct::Tie_ISA; |
27 | |
28 | sub TIEARRAY { |
29 | my $class = shift; |
30 | return bless [], $class; |
31 | } |
32 | |
33 | sub STORE { |
34 | my ($self, $index, $value) = @_; |
35 | Class::Struct::_subclass_error(); |
36 | } |
37 | |
38 | sub FETCH { |
39 | my ($self, $index) = @_; |
40 | $self->[$index]; |
41 | } |
42 | |
43 | sub DESTROY { } |
44 | } |
45 | |
46 | sub struct { |
47 | |
48 | # Determine parameter list structure, one of: |
49 | # struct( class => [ element-list ]) |
50 | # struct( class => { element-list }) |
51 | # struct( element-list ) |
52 | # Latter form assumes current package name as struct name. |
53 | |
54 | my ($class, @decls); |
55 | my $base_type = ref $_[1]; |
56 | if ( $base_type eq 'HASH' ) { |
57 | $class = shift; |
58 | @decls = %{shift()}; |
59 | _usage_error() if @_; |
60 | } |
61 | elsif ( $base_type eq 'ARRAY' ) { |
62 | $class = shift; |
63 | @decls = @{shift()}; |
64 | _usage_error() if @_; |
65 | } |
66 | else { |
67 | $base_type = 'ARRAY'; |
68 | $class = (caller())[0]; |
69 | @decls = @_; |
70 | } |
71 | _usage_error() if @decls % 2 == 1; |
72 | |
73 | # Ensure we are not, and will not be, a subclass. |
74 | |
75 | my $isa = do { |
76 | no strict 'refs'; |
77 | \@{$class . '::ISA'}; |
78 | }; |
79 | _subclass_error() if @$isa; |
80 | tie @$isa, 'Class::Struct::Tie_ISA'; |
81 | |
82 | # Create constructor. |
83 | |
84 | croak "function 'new' already defined in package $class" |
85 | if do { no strict 'refs'; defined &{$class . "::new"} }; |
86 | |
87 | my @methods = (); |
88 | my %refs = (); |
89 | my %arrays = (); |
90 | my %hashes = (); |
91 | my %classes = (); |
92 | my $got_class = 0; |
93 | my $out = ''; |
94 | |
95 | $out = "{\n package $class;\n use Carp;\n sub new {\n"; |
96 | |
97 | my $cnt = 0; |
98 | my $idx = 0; |
99 | my( $cmt, $name, $type, $elem ); |
100 | |
101 | if( $base_type eq 'HASH' ){ |
102 | $out .= " my(\$r) = {};\n"; |
103 | $cmt = ''; |
104 | } |
105 | elsif( $base_type eq 'ARRAY' ){ |
106 | $out .= " my(\$r) = [];\n"; |
107 | } |
108 | while( $idx < @decls ){ |
109 | $name = $decls[$idx]; |
110 | $type = $decls[$idx+1]; |
111 | push( @methods, $name ); |
112 | if( $base_type eq 'HASH' ){ |
113 | $elem = "{'$name'}"; |
114 | } |
115 | elsif( $base_type eq 'ARRAY' ){ |
116 | $elem = "[$cnt]"; |
117 | ++$cnt; |
118 | $cmt = " # $name"; |
119 | } |
120 | if( $type =~ /^\*(.)/ ){ |
121 | $refs{$name}++; |
122 | $type = $1; |
123 | } |
124 | if( $type eq '@' ){ |
125 | $out .= " \$r->$elem = [];$cmt\n"; |
126 | $arrays{$name}++; |
127 | } |
128 | elsif( $type eq '%' ){ |
129 | $out .= " \$r->$elem = {};$cmt\n"; |
130 | $hashes{$name}++; |
131 | } |
132 | elsif ( $type eq '$') { |
133 | $out .= " \$r->$elem = undef;$cmt\n"; |
134 | } |
135 | elsif( $type =~ /^\w+(?:::\w+)*$/ ){ |
136 | $out .= " \$r->$elem = '${type}'->new();$cmt\n"; |
137 | $classes{$name} = $type; |
138 | $got_class = 1; |
139 | } |
140 | else{ |
141 | croak "'$type' is not a valid struct element type"; |
142 | } |
143 | $idx += 2; |
144 | } |
145 | $out .= " bless \$r;\n }\n"; |
146 | |
147 | # Create accessor methods. |
148 | |
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149 | my( $pre, $pst, $sel ); |
150 | $cnt = 0; |
151 | foreach $name (@methods){ |
152 | if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) { |
153 | carp "function '$name' already defined, overrides struct accessor method" |
154 | if $^W; |
155 | } |
156 | else { |
157 | $pre = $pst = $cmt = $sel = ''; |
158 | if( defined $refs{$name} ){ |
159 | $pre = "\\("; |
160 | $pst = ")"; |
161 | $cmt = " # returns ref"; |
162 | } |
163 | $out .= " sub $name {$cmt\n my \$r = shift;\n"; |
164 | if( $base_type eq 'ARRAY' ){ |
165 | $elem = "[$cnt]"; |
166 | ++$cnt; |
167 | } |
168 | elsif( $base_type eq 'HASH' ){ |
169 | $elem = "{'$name'}"; |
170 | } |
171 | if( defined $arrays{$name} ){ |
172 | $out .= " my \$i;\n"; |
173 | $out .= " \@_ ? (\$i = shift) : return $pre\$r->$elem$pst;\n"; |
174 | $sel = "->[\$i]"; |
175 | } |
176 | elsif( defined $hashes{$name} ){ |
177 | $out .= " my \$i;\n"; |
178 | $out .= " \@_ ? (\$i = shift) : return $pre\$r->$elem$pst;\n"; |
179 | $sel = "->{\$i}"; |
180 | } |
181 | elsif( defined $classes{$name} ){ |
182 | if ( $CHECK_CLASS_MEMBERSHIP ) { |
183 | $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$type');\n"; |
184 | } |
185 | } |
186 | $out .= " croak 'Too many args to $name' if \@_ > 1;\n"; |
187 | $out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n"; |
188 | $out .= " }\n"; |
189 | } |
190 | } |
191 | $out .= "}\n1;\n"; |
192 | |
193 | print $out if $print; |
194 | my $result = eval $out; |
195 | carp $@ if $@; |
196 | } |
197 | |
198 | sub _usage_error { |
199 | confess "struct usage error"; |
200 | } |
201 | |
202 | sub _subclass_error { |
203 | croak 'struct class cannot be a subclass (@ISA not allowed)'; |
204 | } |
205 | |
206 | 1; # for require |
207 | |
208 | |
209 | __END__ |
210 | |
211 | =head1 NAME |
212 | |
213 | Class::Struct - declare struct-like datatypes as Perl classes |
214 | |
215 | =head1 SYNOPSIS |
216 | |
217 | use Class::Struct; |
218 | # declare struct, based on array: |
219 | struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]); |
220 | # declare struct, based on hash: |
221 | struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... }); |
222 | |
223 | package CLASS_NAME; |
224 | use Class::Struct; |
225 | # declare struct, based on array, implicit class name: |
226 | struct( ELEMENT_NAME => ELEMENT_TYPE, ... ); |
227 | |
228 | |
229 | package Myobj; |
230 | use Class::Struct; |
231 | # declare struct with four types of elements: |
232 | struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' ); |
233 | |
234 | $obj = new Myobj; # constructor |
235 | |
236 | # scalar type accessor: |
237 | $element_value = $obj->s; # element value |
238 | $obj->s('new value'); # assign to element |
239 | |
240 | # array type accessor: |
241 | $ary_ref = $obj->a; # reference to whole array |
242 | $ary_element_value = $obj->a(2); # array element value |
243 | $obj->a(2, 'new value'); # assign to array element |
244 | |
245 | # hash type accessor: |
246 | $hash_ref = $obj->h; # reference to whole hash |
247 | $hash_element_value = $obj->h('x'); # hash element value |
248 | $obj->h('x', 'new value'); # assign to hash element |
249 | |
250 | # class type accessor: |
251 | $element_value = $obj->c; # object reference |
252 | $obj->c->method(...); # call method of object |
253 | $obj->c(new My_Other_Class); # assign a new object |
254 | |
255 | |
256 | =head1 DESCRIPTION |
257 | |
258 | C<Class::Struct> exports a single function, C<struct>. |
259 | Given a list of element names and types, and optionally |
260 | a class name, C<struct> creates a Perl 5 class that implements |
261 | a "struct-like" data structure. |
262 | |
263 | The new class is given a constructor method, C<new>, for creating |
264 | struct objects. |
265 | |
266 | Each element in the struct data has an accessor method, which is |
267 | used to assign to the element and to fetch its value. The |
268 | default accessor can be overridden by declaring a C<sub> of the |
269 | same name in the package. (See Example 2.) |
270 | |
271 | Each element's type can be scalar, array, hash, or class. |
272 | |
273 | |
274 | =head2 The C<struct()> function |
275 | |
276 | The C<struct> function has three forms of parameter-list. |
277 | |
278 | struct( CLASS_NAME => [ ELEMENT_LIST ]); |
279 | struct( CLASS_NAME => { ELEMENT_LIST }); |
280 | struct( ELEMENT_LIST ); |
281 | |
282 | The first and second forms explicitly identify the name of the |
283 | class being created. The third form assumes the current package |
284 | name as the class name. |
285 | |
286 | An object of a class created by the first and third forms is |
287 | based on an array, whereas an object of a class created by the |
288 | second form is based on a hash. The array-based forms will be |
289 | somewhat faster and smaller; the hash-based forms are more |
290 | flexible. |
291 | |
292 | The class created by C<struct> must not be a subclass of another |
293 | class other than C<UNIVERSAL>. |
294 | |
295 | A function named C<new> must not be explicitly defined in a class |
296 | created by C<struct>. |
297 | |
298 | The I<ELEMENT_LIST> has the form |
299 | |
300 | NAME => TYPE, ... |
301 | |
302 | Each name-type pair declares one element of the struct. Each |
303 | element name will be defined as an accessor method unless a |
304 | method by that name is explicitly defined; in the latter case, a |
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305 | warning is issued if the warning flag (B<-w>) is set. |
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306 | |
307 | |
308 | =head2 Element Types and Accessor Methods |
309 | |
310 | The four element types -- scalar, array, hash, and class -- are |
311 | represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name -- |
312 | optionally preceded by a C<'*'>. |
313 | |
314 | The accessor method provided by C<struct> for an element depends |
315 | on the declared type of the element. |
316 | |
317 | =over |
318 | |
319 | =item Scalar (C<'$'> or C<'*$'>) |
320 | |
321 | The element is a scalar, and is initialized to C<undef>. |
322 | |
323 | The accessor's argument, if any, is assigned to the element. |
324 | |
325 | If the element type is C<'$'>, the value of the element (after |
326 | assignment) is returned. If the element type is C<'*$'>, a reference |
327 | to the element is returned. |
328 | |
329 | =item Array (C<'@'> or C<'*@'>) |
330 | |
331 | The element is an array, initialized to C<()>. |
332 | |
333 | With no argument, the accessor returns a reference to the |
334 | element's whole array. |
335 | |
336 | With one or two arguments, the first argument is an index |
337 | specifying one element of the array; the second argument, if |
338 | present, is assigned to the array element. If the element type |
339 | is C<'@'>, the accessor returns the array element value. If the |
340 | element type is C<'*@'>, a reference to the array element is |
341 | returned. |
342 | |
343 | =item Hash (C<'%'> or C<'*%'>) |
344 | |
345 | The element is a hash, initialized to C<()>. |
346 | |
347 | With no argument, the accessor returns a reference to the |
348 | element's whole hash. |
349 | |
350 | With one or two arguments, the first argument is a key specifying |
351 | one element of the hash; the second argument, if present, is |
352 | assigned to the hash element. If the element type is C<'%'>, the |
353 | accessor returns the hash element value. If the element type is |
354 | C<'*%'>, a reference to the hash element is returned. |
355 | |
356 | =item Class (C<'Class_Name'> or C<'*Class_Name'>) |
357 | |
358 | The element's value must be a reference blessed to the named |
359 | class or to one of its subclasses. The element is initialized to |
360 | the result of calling the C<new> constructor of the named class. |
361 | |
362 | The accessor's argument, if any, is assigned to the element. The |
363 | accessor will C<croak> if this is not an appropriate object |
364 | reference. |
365 | |
366 | If the element type does not start with a C<'*'>, the accessor |
367 | returns the element value (after assignment). If the element type |
368 | starts with a C<'*'>, a reference to the element itself is returned. |
369 | |
370 | =back |
371 | |
372 | =head1 EXAMPLES |
373 | |
374 | =over |
375 | |
376 | =item Example 1 |
377 | |
378 | Giving a struct element a class type that is also a struct is how |
379 | structs are nested. Here, C<timeval> represents a time (seconds and |
380 | microseconds), and C<rusage> has two elements, each of which is of |
381 | type C<timeval>. |
382 | |
383 | use Class::Struct; |
384 | |
385 | struct( rusage => { |
386 | ru_utime => timeval, # seconds |
387 | ru_stime => timeval, # microseconds |
388 | }); |
389 | |
390 | struct( timeval => [ |
391 | tv_secs => '$', |
392 | tv_usecs => '$', |
393 | ]); |
394 | |
395 | # create an object: |
396 | my $t = new rusage; |
397 | # $t->ru_utime and $t->ru_stime are objects of type timeval. |
398 | |
399 | # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec. |
400 | $t->ru_utime->tv_secs(100); |
401 | $t->ru_utime->tv_usecs(0); |
402 | $t->ru_stime->tv_secs(5); |
403 | $t->ru_stime->tv_usecs(0); |
404 | |
405 | |
406 | =item Example 2 |
407 | |
408 | An accessor function can be redefined in order to provide |
409 | additional checking of values, etc. Here, we want the C<count> |
410 | element always to be nonnegative, so we redefine the C<count> |
411 | accessor accordingly. |
412 | |
413 | package MyObj; |
414 | use Class::Struct; |
415 | |
416 | # declare the struct |
417 | struct ( 'MyObj', { count => '$', stuff => '%' } ); |
418 | |
419 | # override the default accessor method for 'count' |
420 | sub count { |
421 | my $self = shift; |
422 | if ( @_ ) { |
423 | die 'count must be nonnegative' if $_[0] < 0; |
424 | $self->{'count'} = shift; |
425 | warn "Too many args to count" if @_; |
426 | } |
427 | return $self->{'count'}; |
428 | } |
429 | |
430 | package main; |
431 | $x = new MyObj; |
432 | print "\$x->count(5) = ", $x->count(5), "\n"; |
433 | # prints '$x->count(5) = 5' |
434 | |
435 | print "\$x->count = ", $x->count, "\n"; |
436 | # prints '$x->count = 5' |
437 | |
438 | print "\$x->count(-5) = ", $x->count(-5), "\n"; |
439 | # dies due to negative argument! |
440 | |
441 | |
442 | =head1 Author and Modification History |
443 | |
444 | |
445 | Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02. |
446 | |
447 | members() function removed. |
448 | Documentation corrected and extended. |
449 | Use of struct() in a subclass prohibited. |
450 | User definition of accessor allowed. |
451 | Treatment of '*' in element types corrected. |
452 | Treatment of classes as element types corrected. |
453 | Class name to struct() made optional. |
454 | Diagnostic checks added. |
455 | |
456 | |
457 | Originally C<Class::Template> by Dean Roehrich. |
458 | |
459 | # Template.pm --- struct/member template builder |
460 | # 12mar95 |
461 | # Dean Roehrich |
462 | # |
463 | # changes/bugs fixed since 28nov94 version: |
464 | # - podified |
465 | # changes/bugs fixed since 21nov94 version: |
466 | # - Fixed examples. |
467 | # changes/bugs fixed since 02sep94 version: |
468 | # - Moved to Class::Template. |
469 | # changes/bugs fixed since 20feb94 version: |
470 | # - Updated to be a more proper module. |
471 | # - Added "use strict". |
472 | # - Bug in build_methods, was using @var when @$var needed. |
473 | # - Now using my() rather than local(). |
474 | # |
475 | # Uses perl5 classes to create nested data types. |
476 | # This is offered as one implementation of Tom Christiansen's "structs.pl" |
477 | # idea. |
478 | |
479 | =cut |