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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 | |
f740b751 |
43 | sub FETCHSIZE { |
44 | my $self = shift; |
45 | return scalar(@$self); |
46 | } |
47 | |
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48 | sub DESTROY { } |
49 | } |
50 | |
51 | sub struct { |
52 | |
53 | # Determine parameter list structure, one of: |
54 | # struct( class => [ element-list ]) |
55 | # struct( class => { element-list }) |
56 | # struct( element-list ) |
57 | # Latter form assumes current package name as struct name. |
58 | |
59 | my ($class, @decls); |
60 | my $base_type = ref $_[1]; |
61 | if ( $base_type eq 'HASH' ) { |
62 | $class = shift; |
63 | @decls = %{shift()}; |
64 | _usage_error() if @_; |
65 | } |
66 | elsif ( $base_type eq 'ARRAY' ) { |
67 | $class = shift; |
68 | @decls = @{shift()}; |
69 | _usage_error() if @_; |
70 | } |
71 | else { |
72 | $base_type = 'ARRAY'; |
73 | $class = (caller())[0]; |
74 | @decls = @_; |
75 | } |
76 | _usage_error() if @decls % 2 == 1; |
77 | |
78 | # Ensure we are not, and will not be, a subclass. |
79 | |
80 | my $isa = do { |
81 | no strict 'refs'; |
82 | \@{$class . '::ISA'}; |
83 | }; |
84 | _subclass_error() if @$isa; |
85 | tie @$isa, 'Class::Struct::Tie_ISA'; |
86 | |
87 | # Create constructor. |
88 | |
89 | croak "function 'new' already defined in package $class" |
90 | if do { no strict 'refs'; defined &{$class . "::new"} }; |
91 | |
92 | my @methods = (); |
93 | my %refs = (); |
94 | my %arrays = (); |
95 | my %hashes = (); |
96 | my %classes = (); |
97 | my $got_class = 0; |
98 | my $out = ''; |
99 | |
100 | $out = "{\n package $class;\n use Carp;\n sub new {\n"; |
101 | |
102 | my $cnt = 0; |
103 | my $idx = 0; |
104 | my( $cmt, $name, $type, $elem ); |
105 | |
106 | if( $base_type eq 'HASH' ){ |
107 | $out .= " my(\$r) = {};\n"; |
108 | $cmt = ''; |
109 | } |
110 | elsif( $base_type eq 'ARRAY' ){ |
111 | $out .= " my(\$r) = [];\n"; |
112 | } |
113 | while( $idx < @decls ){ |
114 | $name = $decls[$idx]; |
115 | $type = $decls[$idx+1]; |
116 | push( @methods, $name ); |
117 | if( $base_type eq 'HASH' ){ |
118 | $elem = "{'$name'}"; |
119 | } |
120 | elsif( $base_type eq 'ARRAY' ){ |
121 | $elem = "[$cnt]"; |
122 | ++$cnt; |
123 | $cmt = " # $name"; |
124 | } |
125 | if( $type =~ /^\*(.)/ ){ |
126 | $refs{$name}++; |
127 | $type = $1; |
128 | } |
129 | if( $type eq '@' ){ |
130 | $out .= " \$r->$elem = [];$cmt\n"; |
131 | $arrays{$name}++; |
132 | } |
133 | elsif( $type eq '%' ){ |
134 | $out .= " \$r->$elem = {};$cmt\n"; |
135 | $hashes{$name}++; |
136 | } |
137 | elsif ( $type eq '$') { |
138 | $out .= " \$r->$elem = undef;$cmt\n"; |
139 | } |
140 | elsif( $type =~ /^\w+(?:::\w+)*$/ ){ |
141 | $out .= " \$r->$elem = '${type}'->new();$cmt\n"; |
142 | $classes{$name} = $type; |
143 | $got_class = 1; |
144 | } |
145 | else{ |
146 | croak "'$type' is not a valid struct element type"; |
147 | } |
148 | $idx += 2; |
149 | } |
150 | $out .= " bless \$r;\n }\n"; |
151 | |
152 | # Create accessor methods. |
153 | |
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154 | my( $pre, $pst, $sel ); |
155 | $cnt = 0; |
156 | foreach $name (@methods){ |
157 | if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) { |
158 | carp "function '$name' already defined, overrides struct accessor method" |
159 | if $^W; |
160 | } |
161 | else { |
162 | $pre = $pst = $cmt = $sel = ''; |
163 | if( defined $refs{$name} ){ |
164 | $pre = "\\("; |
165 | $pst = ")"; |
166 | $cmt = " # returns ref"; |
167 | } |
168 | $out .= " sub $name {$cmt\n my \$r = shift;\n"; |
169 | if( $base_type eq 'ARRAY' ){ |
170 | $elem = "[$cnt]"; |
171 | ++$cnt; |
172 | } |
173 | elsif( $base_type eq 'HASH' ){ |
174 | $elem = "{'$name'}"; |
175 | } |
176 | if( defined $arrays{$name} ){ |
177 | $out .= " my \$i;\n"; |
178 | $out .= " \@_ ? (\$i = shift) : return $pre\$r->$elem$pst;\n"; |
179 | $sel = "->[\$i]"; |
180 | } |
181 | elsif( defined $hashes{$name} ){ |
182 | $out .= " my \$i;\n"; |
183 | $out .= " \@_ ? (\$i = shift) : return $pre\$r->$elem$pst;\n"; |
184 | $sel = "->{\$i}"; |
185 | } |
186 | elsif( defined $classes{$name} ){ |
187 | if ( $CHECK_CLASS_MEMBERSHIP ) { |
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188 | $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n"; |
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189 | } |
190 | } |
191 | $out .= " croak 'Too many args to $name' if \@_ > 1;\n"; |
192 | $out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n"; |
193 | $out .= " }\n"; |
194 | } |
195 | } |
196 | $out .= "}\n1;\n"; |
197 | |
198 | print $out if $print; |
199 | my $result = eval $out; |
200 | carp $@ if $@; |
201 | } |
202 | |
203 | sub _usage_error { |
204 | confess "struct usage error"; |
205 | } |
206 | |
207 | sub _subclass_error { |
208 | croak 'struct class cannot be a subclass (@ISA not allowed)'; |
209 | } |
210 | |
211 | 1; # for require |
212 | |
213 | |
214 | __END__ |
215 | |
216 | =head1 NAME |
217 | |
218 | Class::Struct - declare struct-like datatypes as Perl classes |
219 | |
220 | =head1 SYNOPSIS |
221 | |
222 | use Class::Struct; |
223 | # declare struct, based on array: |
224 | struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]); |
225 | # declare struct, based on hash: |
226 | struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... }); |
227 | |
228 | package CLASS_NAME; |
229 | use Class::Struct; |
230 | # declare struct, based on array, implicit class name: |
231 | struct( ELEMENT_NAME => ELEMENT_TYPE, ... ); |
232 | |
233 | |
234 | package Myobj; |
235 | use Class::Struct; |
236 | # declare struct with four types of elements: |
237 | struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' ); |
238 | |
239 | $obj = new Myobj; # constructor |
240 | |
241 | # scalar type accessor: |
242 | $element_value = $obj->s; # element value |
243 | $obj->s('new value'); # assign to element |
244 | |
245 | # array type accessor: |
246 | $ary_ref = $obj->a; # reference to whole array |
247 | $ary_element_value = $obj->a(2); # array element value |
248 | $obj->a(2, 'new value'); # assign to array element |
249 | |
250 | # hash type accessor: |
251 | $hash_ref = $obj->h; # reference to whole hash |
252 | $hash_element_value = $obj->h('x'); # hash element value |
253 | $obj->h('x', 'new value'); # assign to hash element |
254 | |
255 | # class type accessor: |
256 | $element_value = $obj->c; # object reference |
257 | $obj->c->method(...); # call method of object |
258 | $obj->c(new My_Other_Class); # assign a new object |
259 | |
260 | |
261 | =head1 DESCRIPTION |
262 | |
263 | C<Class::Struct> exports a single function, C<struct>. |
264 | Given a list of element names and types, and optionally |
265 | a class name, C<struct> creates a Perl 5 class that implements |
266 | a "struct-like" data structure. |
267 | |
268 | The new class is given a constructor method, C<new>, for creating |
269 | struct objects. |
270 | |
271 | Each element in the struct data has an accessor method, which is |
272 | used to assign to the element and to fetch its value. The |
273 | default accessor can be overridden by declaring a C<sub> of the |
274 | same name in the package. (See Example 2.) |
275 | |
276 | Each element's type can be scalar, array, hash, or class. |
277 | |
278 | |
279 | =head2 The C<struct()> function |
280 | |
281 | The C<struct> function has three forms of parameter-list. |
282 | |
283 | struct( CLASS_NAME => [ ELEMENT_LIST ]); |
284 | struct( CLASS_NAME => { ELEMENT_LIST }); |
285 | struct( ELEMENT_LIST ); |
286 | |
287 | The first and second forms explicitly identify the name of the |
288 | class being created. The third form assumes the current package |
289 | name as the class name. |
290 | |
291 | An object of a class created by the first and third forms is |
292 | based on an array, whereas an object of a class created by the |
293 | second form is based on a hash. The array-based forms will be |
294 | somewhat faster and smaller; the hash-based forms are more |
295 | flexible. |
296 | |
297 | The class created by C<struct> must not be a subclass of another |
298 | class other than C<UNIVERSAL>. |
299 | |
300 | A function named C<new> must not be explicitly defined in a class |
301 | created by C<struct>. |
302 | |
303 | The I<ELEMENT_LIST> has the form |
304 | |
305 | NAME => TYPE, ... |
306 | |
307 | Each name-type pair declares one element of the struct. Each |
308 | element name will be defined as an accessor method unless a |
309 | method by that name is explicitly defined; in the latter case, a |
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310 | warning is issued if the warning flag (B<-w>) is set. |
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311 | |
312 | |
313 | =head2 Element Types and Accessor Methods |
314 | |
315 | The four element types -- scalar, array, hash, and class -- are |
316 | represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name -- |
317 | optionally preceded by a C<'*'>. |
318 | |
319 | The accessor method provided by C<struct> for an element depends |
320 | on the declared type of the element. |
321 | |
322 | =over |
323 | |
324 | =item Scalar (C<'$'> or C<'*$'>) |
325 | |
326 | The element is a scalar, and is initialized to C<undef>. |
327 | |
328 | The accessor's argument, if any, is assigned to the element. |
329 | |
330 | If the element type is C<'$'>, the value of the element (after |
331 | assignment) is returned. If the element type is C<'*$'>, a reference |
332 | to the element is returned. |
333 | |
334 | =item Array (C<'@'> or C<'*@'>) |
335 | |
336 | The element is an array, initialized to C<()>. |
337 | |
338 | With no argument, the accessor returns a reference to the |
339 | element's whole array. |
340 | |
341 | With one or two arguments, the first argument is an index |
342 | specifying one element of the array; the second argument, if |
343 | present, is assigned to the array element. If the element type |
344 | is C<'@'>, the accessor returns the array element value. If the |
345 | element type is C<'*@'>, a reference to the array element is |
346 | returned. |
347 | |
348 | =item Hash (C<'%'> or C<'*%'>) |
349 | |
350 | The element is a hash, initialized to C<()>. |
351 | |
352 | With no argument, the accessor returns a reference to the |
353 | element's whole hash. |
354 | |
355 | With one or two arguments, the first argument is a key specifying |
356 | one element of the hash; the second argument, if present, is |
357 | assigned to the hash element. If the element type is C<'%'>, the |
358 | accessor returns the hash element value. If the element type is |
359 | C<'*%'>, a reference to the hash element is returned. |
360 | |
361 | =item Class (C<'Class_Name'> or C<'*Class_Name'>) |
362 | |
363 | The element's value must be a reference blessed to the named |
364 | class or to one of its subclasses. The element is initialized to |
365 | the result of calling the C<new> constructor of the named class. |
366 | |
367 | The accessor's argument, if any, is assigned to the element. The |
368 | accessor will C<croak> if this is not an appropriate object |
369 | reference. |
370 | |
371 | If the element type does not start with a C<'*'>, the accessor |
372 | returns the element value (after assignment). If the element type |
373 | starts with a C<'*'>, a reference to the element itself is returned. |
374 | |
375 | =back |
376 | |
377 | =head1 EXAMPLES |
378 | |
379 | =over |
380 | |
381 | =item Example 1 |
382 | |
383 | Giving a struct element a class type that is also a struct is how |
384 | structs are nested. Here, C<timeval> represents a time (seconds and |
385 | microseconds), and C<rusage> has two elements, each of which is of |
386 | type C<timeval>. |
387 | |
388 | use Class::Struct; |
389 | |
390 | struct( rusage => { |
391 | ru_utime => timeval, # seconds |
392 | ru_stime => timeval, # microseconds |
393 | }); |
394 | |
395 | struct( timeval => [ |
396 | tv_secs => '$', |
397 | tv_usecs => '$', |
398 | ]); |
399 | |
400 | # create an object: |
401 | my $t = new rusage; |
402 | # $t->ru_utime and $t->ru_stime are objects of type timeval. |
403 | |
404 | # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec. |
405 | $t->ru_utime->tv_secs(100); |
406 | $t->ru_utime->tv_usecs(0); |
407 | $t->ru_stime->tv_secs(5); |
408 | $t->ru_stime->tv_usecs(0); |
409 | |
410 | |
411 | =item Example 2 |
412 | |
413 | An accessor function can be redefined in order to provide |
414 | additional checking of values, etc. Here, we want the C<count> |
415 | element always to be nonnegative, so we redefine the C<count> |
416 | accessor accordingly. |
417 | |
418 | package MyObj; |
419 | use Class::Struct; |
420 | |
421 | # declare the struct |
422 | struct ( 'MyObj', { count => '$', stuff => '%' } ); |
423 | |
424 | # override the default accessor method for 'count' |
425 | sub count { |
426 | my $self = shift; |
427 | if ( @_ ) { |
428 | die 'count must be nonnegative' if $_[0] < 0; |
429 | $self->{'count'} = shift; |
430 | warn "Too many args to count" if @_; |
431 | } |
432 | return $self->{'count'}; |
433 | } |
434 | |
435 | package main; |
436 | $x = new MyObj; |
437 | print "\$x->count(5) = ", $x->count(5), "\n"; |
438 | # prints '$x->count(5) = 5' |
439 | |
440 | print "\$x->count = ", $x->count, "\n"; |
441 | # prints '$x->count = 5' |
442 | |
443 | print "\$x->count(-5) = ", $x->count(-5), "\n"; |
444 | # dies due to negative argument! |
445 | |
446 | |
447 | =head1 Author and Modification History |
448 | |
449 | |
450 | Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02. |
451 | |
452 | members() function removed. |
453 | Documentation corrected and extended. |
454 | Use of struct() in a subclass prohibited. |
455 | User definition of accessor allowed. |
456 | Treatment of '*' in element types corrected. |
457 | Treatment of classes as element types corrected. |
458 | Class name to struct() made optional. |
459 | Diagnostic checks added. |
460 | |
461 | |
462 | Originally C<Class::Template> by Dean Roehrich. |
463 | |
464 | # Template.pm --- struct/member template builder |
465 | # 12mar95 |
466 | # Dean Roehrich |
467 | # |
468 | # changes/bugs fixed since 28nov94 version: |
469 | # - podified |
470 | # changes/bugs fixed since 21nov94 version: |
471 | # - Fixed examples. |
472 | # changes/bugs fixed since 02sep94 version: |
473 | # - Moved to Class::Template. |
474 | # changes/bugs fixed since 20feb94 version: |
475 | # - Updated to be a more proper module. |
476 | # - Added "use strict". |
477 | # - Bug in build_methods, was using @var when @$var needed. |
478 | # - Now using my() rather than local(). |
479 | # |
480 | # Uses perl5 classes to create nested data types. |
481 | # This is offered as one implementation of Tom Christiansen's "structs.pl" |
482 | # idea. |
483 | |
484 | =cut |