1package Class::Struct; 2 3## See POD after __END__ 4 5use 5.005_64; 6 7use strict; 8use warnings::register; 9our(@ISA, @EXPORT, $VERSION); 10 11use Carp; 12 13require Exporter; 14@ISA = qw(Exporter); 15@EXPORT = qw(struct); 16 17$VERSION = '0.58'; 18 19## Tested on 5.002 and 5.003 without class membership tests: 20my $CHECK_CLASS_MEMBERSHIP = ($] >= 5.003_95); 21 22my $print = 0; 23sub printem { 24 if (@_) { $print = shift } 25 else { $print++ } 26} 27 28{ 29 package Class::Struct::Tie_ISA; 30 31 sub TIEARRAY { 32 my $class = shift; 33 return bless [], $class; 34 } 35 36 sub STORE { 37 my ($self, $index, $value) = @_; 38 Class::Struct::_subclass_error(); 39 } 40 41 sub FETCH { 42 my ($self, $index) = @_; 43 $self->[$index]; 44 } 45 46 sub FETCHSIZE { 47 my $self = shift; 48 return scalar(@$self); 49 } 50 51 sub DESTROY { } 52} 53 54sub struct { 55 56 # Determine parameter list structure, one of: 57 # struct( class => [ element-list ]) 58 # struct( class => { element-list }) 59 # struct( element-list ) 60 # Latter form assumes current package name as struct name. 61 62 my ($class, @decls); 63 my $base_type = ref $_[1]; 64 if ( $base_type eq 'HASH' ) { 65 $class = shift; 66 @decls = %{shift()}; 67 _usage_error() if @_; 68 } 69 elsif ( $base_type eq 'ARRAY' ) { 70 $class = shift; 71 @decls = @{shift()}; 72 _usage_error() if @_; 73 } 74 else { 75 $base_type = 'ARRAY'; 76 $class = (caller())[0]; 77 @decls = @_; 78 } 79 _usage_error() if @decls % 2 == 1; 80 81 # Ensure we are not, and will not be, a subclass. 82 83 my $isa = do { 84 no strict 'refs'; 85 \@{$class . '::ISA'}; 86 }; 87 _subclass_error() if @$isa; 88 tie @$isa, 'Class::Struct::Tie_ISA'; 89 90 # Create constructor. 91 92 croak "function 'new' already defined in package $class" 93 if do { no strict 'refs'; defined &{$class . "::new"} }; 94 95 my @methods = (); 96 my %refs = (); 97 my %arrays = (); 98 my %hashes = (); 99 my %classes = (); 100 my $got_class = 0; 101 my $out = ''; 102 103 $out = "{\n package $class;\n use Carp;\n sub new {\n"; 104 $out .= " my (\$class, \%init) = \@_;\n"; 105 $out .= " \$class = __PACKAGE__ unless \@_;\n"; 106 107 my $cnt = 0; 108 my $idx = 0; 109 my( $cmt, $name, $type, $elem ); 110 111 if( $base_type eq 'HASH' ){ 112 $out .= " my(\$r) = {};\n"; 113 $cmt = ''; 114 } 115 elsif( $base_type eq 'ARRAY' ){ 116 $out .= " my(\$r) = [];\n"; 117 } 118 while( $idx < @decls ){ 119 $name = $decls[$idx]; 120 $type = $decls[$idx+1]; 121 push( @methods, $name ); 122 if( $base_type eq 'HASH' ){ 123 $elem = "{'${class}::$name'}"; 124 } 125 elsif( $base_type eq 'ARRAY' ){ 126 $elem = "[$cnt]"; 127 ++$cnt; 128 $cmt = " # $name"; 129 } 130 if( $type =~ /^\*(.)/ ){ 131 $refs{$name}++; 132 $type = $1; 133 } 134 my $init = "defined(\$init{'$name'}) ? \$init{'$name'} :"; 135 if( $type eq '@' ){ 136 $out .= " croak 'Initializer for $name must be array reference'\n"; 137 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'ARRAY';\n"; 138 $out .= " \$r->$elem = $init [];$cmt\n"; 139 $arrays{$name}++; 140 } 141 elsif( $type eq '%' ){ 142 $out .= " croak 'Initializer for $name must be hash reference'\n"; 143 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n"; 144 $out .= " \$r->$elem = $init {};$cmt\n"; 145 $hashes{$name}++; 146 } 147 elsif ( $type eq '$') { 148 $out .= " \$r->$elem = $init undef;$cmt\n"; 149 } 150 elsif( $type =~ /^\w+(?:::\w+)*$/ ){ 151 $init = "defined(\$init{'$name'}) ? \%{\$init{'$name'}} : ()"; 152 $out .= " croak 'Initializer for $name must be hash reference'\n"; 153 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n"; 154 $out .= " \$r->$elem = '${type}'->new($init);$cmt\n"; 155 $classes{$name} = $type; 156 $got_class = 1; 157 } 158 else{ 159 croak "'$type' is not a valid struct element type"; 160 } 161 $idx += 2; 162 } 163 $out .= " bless \$r, \$class;\n }\n"; 164 165 # Create accessor methods. 166 167 my( $pre, $pst, $sel ); 168 $cnt = 0; 169 foreach $name (@methods){ 170 if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) { 171 warnings::warn "function '$name' already defined, overrides struct accessor method" 172 if warnings::enabled(); 173 } 174 else { 175 $pre = $pst = $cmt = $sel = ''; 176 if( defined $refs{$name} ){ 177 $pre = "\\("; 178 $pst = ")"; 179 $cmt = " # returns ref"; 180 } 181 $out .= " sub $name {$cmt\n my \$r = shift;\n"; 182 if( $base_type eq 'ARRAY' ){ 183 $elem = "[$cnt]"; 184 ++$cnt; 185 } 186 elsif( $base_type eq 'HASH' ){ 187 $elem = "{'${class}::$name'}"; 188 } 189 if( defined $arrays{$name} ){ 190 $out .= " my \$i;\n"; 191 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n"; 192 $sel = "->[\$i]"; 193 } 194 elsif( defined $hashes{$name} ){ 195 $out .= " my \$i;\n"; 196 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n"; 197 $sel = "->{\$i}"; 198 } 199 elsif( defined $classes{$name} ){ 200 if ( $CHECK_CLASS_MEMBERSHIP ) { 201 $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n"; 202 } 203 } 204 $out .= " croak 'Too many args to $name' if \@_ > 1;\n"; 205 $out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n"; 206 $out .= " }\n"; 207 } 208 } 209 $out .= "}\n1;\n"; 210 211 print $out if $print; 212 my $result = eval $out; 213 carp $@ if $@; 214} 215 216sub _usage_error { 217 confess "struct usage error"; 218} 219 220sub _subclass_error { 221 croak 'struct class cannot be a subclass (@ISA not allowed)'; 222} 223 2241; # for require 225 226 227__END__ 228 229=head1 NAME 230 231Class::Struct - declare struct-like datatypes as Perl classes 232 233=head1 SYNOPSIS 234 235 use Class::Struct; 236 # declare struct, based on array: 237 struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]); 238 # declare struct, based on hash: 239 struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... }); 240 241 package CLASS_NAME; 242 use Class::Struct; 243 # declare struct, based on array, implicit class name: 244 struct( ELEMENT_NAME => ELEMENT_TYPE, ... ); 245 246 247 package Myobj; 248 use Class::Struct; 249 # declare struct with four types of elements: 250 struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' ); 251 252 $obj = new Myobj; # constructor 253 254 # scalar type accessor: 255 $element_value = $obj->s; # element value 256 $obj->s('new value'); # assign to element 257 258 # array type accessor: 259 $ary_ref = $obj->a; # reference to whole array 260 $ary_element_value = $obj->a(2); # array element value 261 $obj->a(2, 'new value'); # assign to array element 262 263 # hash type accessor: 264 $hash_ref = $obj->h; # reference to whole hash 265 $hash_element_value = $obj->h('x'); # hash element value 266 $obj->h('x', 'new value'); # assign to hash element 267 268 # class type accessor: 269 $element_value = $obj->c; # object reference 270 $obj->c->method(...); # call method of object 271 $obj->c(new My_Other_Class); # assign a new object 272 273 274=head1 DESCRIPTION 275 276C<Class::Struct> exports a single function, C<struct>. 277Given a list of element names and types, and optionally 278a class name, C<struct> creates a Perl 5 class that implements 279a "struct-like" data structure. 280 281The new class is given a constructor method, C<new>, for creating 282struct objects. 283 284Each element in the struct data has an accessor method, which is 285used to assign to the element and to fetch its value. The 286default accessor can be overridden by declaring a C<sub> of the 287same name in the package. (See Example 2.) 288 289Each element's type can be scalar, array, hash, or class. 290 291 292=head2 The C<struct()> function 293 294The C<struct> function has three forms of parameter-list. 295 296 struct( CLASS_NAME => [ ELEMENT_LIST ]); 297 struct( CLASS_NAME => { ELEMENT_LIST }); 298 struct( ELEMENT_LIST ); 299 300The first and second forms explicitly identify the name of the 301class being created. The third form assumes the current package 302name as the class name. 303 304An object of a class created by the first and third forms is 305based on an array, whereas an object of a class created by the 306second form is based on a hash. The array-based forms will be 307somewhat faster and smaller; the hash-based forms are more 308flexible. 309 310The class created by C<struct> must not be a subclass of another 311class other than C<UNIVERSAL>. 312 313It can, however, be used as a superclass for other classes. To facilitate 314this, the generated constructor method uses a two-argument blessing. 315Furthermore, if the class is hash-based, the key of each element is 316prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12). 317 318A function named C<new> must not be explicitly defined in a class 319created by C<struct>. 320 321The I<ELEMENT_LIST> has the form 322 323 NAME => TYPE, ... 324 325Each name-type pair declares one element of the struct. Each 326element name will be defined as an accessor method unless a 327method by that name is explicitly defined; in the latter case, a 328warning is issued if the warning flag (B<-w>) is set. 329 330 331=head2 Element Types and Accessor Methods 332 333The four element types -- scalar, array, hash, and class -- are 334represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name -- 335optionally preceded by a C<'*'>. 336 337The accessor method provided by C<struct> for an element depends 338on the declared type of the element. 339 340=over 341 342=item Scalar (C<'$'> or C<'*$'>) 343 344The element is a scalar, and by default is initialized to C<undef> 345(but see L<Initializing with new>). 346 347The accessor's argument, if any, is assigned to the element. 348 349If the element type is C<'$'>, the value of the element (after 350assignment) is returned. If the element type is C<'*$'>, a reference 351to the element is returned. 352 353=item Array (C<'@'> or C<'*@'>) 354 355The element is an array, initialized by default to C<()>. 356 357With no argument, the accessor returns a reference to the 358element's whole array (whether or not the element was 359specified as C<'@'> or C<'*@'>). 360 361With one or two arguments, the first argument is an index 362specifying one element of the array; the second argument, if 363present, is assigned to the array element. If the element type 364is C<'@'>, the accessor returns the array element value. If the 365element type is C<'*@'>, a reference to the array element is 366returned. 367 368=item Hash (C<'%'> or C<'*%'>) 369 370The element is a hash, initialized by default to C<()>. 371 372With no argument, the accessor returns a reference to the 373element's whole hash (whether or not the element was 374specified as C<'%'> or C<'*%'>). 375 376With one or two arguments, the first argument is a key specifying 377one element of the hash; the second argument, if present, is 378assigned to the hash element. If the element type is C<'%'>, the 379accessor returns the hash element value. If the element type is 380C<'*%'>, a reference to the hash element is returned. 381 382=item Class (C<'Class_Name'> or C<'*Class_Name'>) 383 384The element's value must be a reference blessed to the named 385class or to one of its subclasses. The element is initialized to 386the result of calling the C<new> constructor of the named class. 387 388The accessor's argument, if any, is assigned to the element. The 389accessor will C<croak> if this is not an appropriate object 390reference. 391 392If the element type does not start with a C<'*'>, the accessor 393returns the element value (after assignment). If the element type 394starts with a C<'*'>, a reference to the element itself is returned. 395 396=back 397 398=head2 Initializing with C<new> 399 400C<struct> always creates a constructor called C<new>. That constructor 401may take a list of initializers for the various elements of the new 402struct. 403 404Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>. 405The initializer value for a scalar element is just a scalar value. The 406initializer for an array element is an array reference. The initializer 407for a hash is a hash reference. 408 409The initializer for a class element is also a hash reference, and the 410contents of that hash are passed to the element's own constructor. 411 412See Example 3 below for an example of initialization. 413 414 415=head1 EXAMPLES 416 417=over 418 419=item Example 1 420 421Giving a struct element a class type that is also a struct is how 422structs are nested. Here, C<timeval> represents a time (seconds and 423microseconds), and C<rusage> has two elements, each of which is of 424type C<timeval>. 425 426 use Class::Struct; 427 428 struct( rusage => { 429 ru_utime => timeval, # seconds 430 ru_stime => timeval, # microseconds 431 }); 432 433 struct( timeval => [ 434 tv_secs => '$', 435 tv_usecs => '$', 436 ]); 437 438 # create an object: 439 my $t = new rusage; 440 441 # $t->ru_utime and $t->ru_stime are objects of type timeval. 442 # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec. 443 $t->ru_utime->tv_secs(100); 444 $t->ru_utime->tv_usecs(0); 445 $t->ru_stime->tv_secs(5); 446 $t->ru_stime->tv_usecs(0); 447 448 449=item Example 2 450 451An accessor function can be redefined in order to provide 452additional checking of values, etc. Here, we want the C<count> 453element always to be nonnegative, so we redefine the C<count> 454accessor accordingly. 455 456 package MyObj; 457 use Class::Struct; 458 459 # declare the struct 460 struct ( 'MyObj', { count => '$', stuff => '%' } ); 461 462 # override the default accessor method for 'count' 463 sub count { 464 my $self = shift; 465 if ( @_ ) { 466 die 'count must be nonnegative' if $_[0] < 0; 467 $self->{'count'} = shift; 468 warn "Too many args to count" if @_; 469 } 470 return $self->{'count'}; 471 } 472 473 package main; 474 $x = new MyObj; 475 print "\$x->count(5) = ", $x->count(5), "\n"; 476 # prints '$x->count(5) = 5' 477 478 print "\$x->count = ", $x->count, "\n"; 479 # prints '$x->count = 5' 480 481 print "\$x->count(-5) = ", $x->count(-5), "\n"; 482 # dies due to negative argument! 483 484=item Example 3 485 486The constructor of a generated class can be passed a list 487of I<element>=>I<value> pairs, with which to initialize the struct. 488If no initializer is specified for a particular element, its default 489initialization is performed instead. Initializers for non-existent 490elements are silently ignored. 491 492Note that the initializer for a nested struct is specified 493as an anonymous hash of initializers, which is passed on to the nested 494struct's constructor. 495 496 497 use Class::Struct; 498 499 struct Breed => 500 { 501 name => '$', 502 cross => '$', 503 }; 504 505 struct Cat => 506 [ 507 name => '$', 508 kittens => '@', 509 markings => '%', 510 breed => 'Breed', 511 ]; 512 513 514 my $cat = Cat->new( name => 'Socks', 515 kittens => ['Monica', 'Kenneth'], 516 markings => { socks=>1, blaze=>"white" }, 517 breed => { name=>'short-hair', cross=>1 }, 518 ); 519 520 print "Once a cat called ", $cat->name, "\n"; 521 print "(which was a ", $cat->breed->name, ")\n"; 522 print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n"; 523 524=back 525 526=head1 Author and Modification History 527 528 529Modified by Damian Conway, 1999-03-05, v0.58. 530 531 Added handling of hash-like arg list to class ctor. 532 533 Changed to two-argument blessing in ctor to support 534 derivation from created classes. 535 536 Added classname prefixes to keys in hash-based classes 537 (refer to "Perl Cookbook", Recipe 13.12 for rationale). 538 539 Corrected behaviour of accessors for '*@' and '*%' struct 540 elements. Package now implements documented behaviour when 541 returning a reference to an entire hash or array element. 542 Previously these were returned as a reference to a reference 543 to the element. 544 545 546Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02. 547 548 members() function removed. 549 Documentation corrected and extended. 550 Use of struct() in a subclass prohibited. 551 User definition of accessor allowed. 552 Treatment of '*' in element types corrected. 553 Treatment of classes as element types corrected. 554 Class name to struct() made optional. 555 Diagnostic checks added. 556 557 558Originally C<Class::Template> by Dean Roehrich. 559 560 # Template.pm --- struct/member template builder 561 # 12mar95 562 # Dean Roehrich 563 # 564 # changes/bugs fixed since 28nov94 version: 565 # - podified 566 # changes/bugs fixed since 21nov94 version: 567 # - Fixed examples. 568 # changes/bugs fixed since 02sep94 version: 569 # - Moved to Class::Template. 570 # changes/bugs fixed since 20feb94 version: 571 # - Updated to be a more proper module. 572 # - Added "use strict". 573 # - Bug in build_methods, was using @var when @$var needed. 574 # - Now using my() rather than local(). 575 # 576 # Uses perl5 classes to create nested data types. 577 # This is offered as one implementation of Tom Christiansen's "structs.pl" 578 # idea. 579 580=cut 581