1package Class::Struct; 2 3## See POD after __END__ 4 5use 5.006_001; 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 = '0.64'; 18 19my $print = 0; 20sub 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 FETCHSIZE { 44 my $self = shift; 45 return scalar(@$self); 46 } 47 48 sub DESTROY { } 49} 50 51sub import { 52 my $self = shift; 53 54 if ( @_ == 0 ) { 55 $self->export_to_level( 1, $self, @EXPORT ); 56 } elsif ( @_ == 1 ) { 57 # This is admittedly a little bit silly: 58 # do we ever export anything else than 'struct'...? 59 $self->export_to_level( 1, $self, @_ ); 60 } else { 61 goto &struct; 62 } 63} 64 65sub struct { 66 67 # Determine parameter list structure, one of: 68 # struct( class => [ element-list ]) 69 # struct( class => { element-list }) 70 # struct( element-list ) 71 # Latter form assumes current package name as struct name. 72 73 my ($class, @decls); 74 my $base_type = ref $_[1]; 75 if ( $base_type eq 'HASH' ) { 76 $class = shift; 77 @decls = %{shift()}; 78 _usage_error() if @_; 79 } 80 elsif ( $base_type eq 'ARRAY' ) { 81 $class = shift; 82 @decls = @{shift()}; 83 _usage_error() if @_; 84 } 85 else { 86 $base_type = 'ARRAY'; 87 $class = (caller())[0]; 88 @decls = @_; 89 } 90 91 _usage_error() if @decls % 2 == 1; 92 93 # Ensure we are not, and will not be, a subclass. 94 95 my $isa = do { 96 no strict 'refs'; 97 \@{$class . '::ISA'}; 98 }; 99 _subclass_error() if @$isa; 100 tie @$isa, 'Class::Struct::Tie_ISA'; 101 102 # Create constructor. 103 104 croak "function 'new' already defined in package $class" 105 if do { no strict 'refs'; defined &{$class . "::new"} }; 106 107 my @methods = (); 108 my %refs = (); 109 my %arrays = (); 110 my %hashes = (); 111 my %classes = (); 112 my $got_class = 0; 113 my $out = ''; 114 115 $out = "{\n package $class;\n use Carp;\n sub new {\n"; 116 $out .= " my (\$class, \%init) = \@_;\n"; 117 $out .= " \$class = __PACKAGE__ unless \@_;\n"; 118 119 my $cnt = 0; 120 my $idx = 0; 121 my( $cmt, $name, $type, $elem ); 122 123 if( $base_type eq 'HASH' ){ 124 $out .= " my(\$r) = {};\n"; 125 $cmt = ''; 126 } 127 elsif( $base_type eq 'ARRAY' ){ 128 $out .= " my(\$r) = [];\n"; 129 } 130 131 $out .= " bless \$r, \$class;\n\n"; 132 133 while( $idx < @decls ){ 134 $name = $decls[$idx]; 135 $type = $decls[$idx+1]; 136 push( @methods, $name ); 137 if( $base_type eq 'HASH' ){ 138 $elem = "{'${class}::$name'}"; 139 } 140 elsif( $base_type eq 'ARRAY' ){ 141 $elem = "[$cnt]"; 142 ++$cnt; 143 $cmt = " # $name"; 144 } 145 if( $type =~ /^\*(.)/ ){ 146 $refs{$name}++; 147 $type = $1; 148 } 149 my $init = "defined(\$init{'$name'}) ? \$init{'$name'} :"; 150 if( $type eq '@' ){ 151 $out .= " croak 'Initializer for $name must be array reference'\n"; 152 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'ARRAY';\n"; 153 $out .= " \$r->$name( $init [] );$cmt\n"; 154 $arrays{$name}++; 155 } 156 elsif( $type eq '%' ){ 157 $out .= " croak 'Initializer for $name must be hash reference'\n"; 158 $out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n"; 159 $out .= " \$r->$name( $init {} );$cmt\n"; 160 $hashes{$name}++; 161 } 162 elsif ( $type eq '$') { 163 $out .= " \$r->$name( $init undef );$cmt\n"; 164 } 165 elsif( $type =~ /^\w+(?:::\w+)*$/ ){ 166 $out .= " if (defined(\$init{'$name'})) {\n"; 167 $out .= " if (ref \$init{'$name'} eq 'HASH')\n"; 168 $out .= " { \$r->$name( $type->new(\%{\$init{'$name'}}) ) } $cmt\n"; 169 $out .= " elsif (UNIVERSAL::isa(\$init{'$name'}, '$type'))\n"; 170 $out .= " { \$r->$name( \$init{'$name'} ) } $cmt\n"; 171 $out .= " else { croak 'Initializer for $name must be hash or $type reference' }\n"; 172 $out .= " }\n"; 173 $classes{$name} = $type; 174 $got_class = 1; 175 } 176 else{ 177 croak "'$type' is not a valid struct element type"; 178 } 179 $idx += 2; 180 } 181 182 $out .= "\n \$r;\n}\n"; 183 184 # Create accessor methods. 185 186 my( $pre, $pst, $sel ); 187 $cnt = 0; 188 foreach $name (@methods){ 189 if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) { 190 warnings::warnif("function '$name' already defined, overrides struct accessor method"); 191 } 192 else { 193 $pre = $pst = $cmt = $sel = ''; 194 if( defined $refs{$name} ){ 195 $pre = "\\("; 196 $pst = ")"; 197 $cmt = " # returns ref"; 198 } 199 $out .= " sub $name {$cmt\n my \$r = shift;\n"; 200 if( $base_type eq 'ARRAY' ){ 201 $elem = "[$cnt]"; 202 ++$cnt; 203 } 204 elsif( $base_type eq 'HASH' ){ 205 $elem = "{'${class}::$name'}"; 206 } 207 if( defined $arrays{$name} ){ 208 $out .= " my \$i;\n"; 209 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n"; 210 $out .= " if (ref(\$i) eq 'ARRAY' && !\@_) { \$r->$elem = \$i; return \$r }\n"; 211 $sel = "->[\$i]"; 212 } 213 elsif( defined $hashes{$name} ){ 214 $out .= " my \$i;\n"; 215 $out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n"; 216 $out .= " if (ref(\$i) eq 'HASH' && !\@_) { \$r->$elem = \$i; return \$r }\n"; 217 $sel = "->{\$i}"; 218 } 219 elsif( defined $classes{$name} ){ 220 $out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n"; 221 } 222 $out .= " croak 'Too many args to $name' if \@_ > 1;\n"; 223 $out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n"; 224 $out .= " }\n"; 225 } 226 } 227 $out .= "}\n1;\n"; 228 229 print $out if $print; 230 my $result = eval $out; 231 carp $@ if $@; 232} 233 234sub _usage_error { 235 confess "struct usage error"; 236} 237 238sub _subclass_error { 239 croak 'struct class cannot be a subclass (@ISA not allowed)'; 240} 241 2421; # for require 243 244 245__END__ 246 247=head1 NAME 248 249Class::Struct - declare struct-like datatypes as Perl classes 250 251=head1 SYNOPSIS 252 253 use Class::Struct; 254 # declare struct, based on array: 255 struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]); 256 # declare struct, based on hash: 257 struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... }); 258 259 package CLASS_NAME; 260 use Class::Struct; 261 # declare struct, based on array, implicit class name: 262 struct( ELEMENT_NAME => ELEMENT_TYPE, ... ); 263 264 # Declare struct at compile time 265 use Class::Struct CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]; 266 use Class::Struct CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... }; 267 268 # declare struct at compile time, based on array, implicit class name: 269 package CLASS_NAME; 270 use Class::Struct ELEMENT_NAME => ELEMENT_TYPE, ... ; 271 272 package Myobj; 273 use Class::Struct; 274 # declare struct with four types of elements: 275 struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' ); 276 277 $obj = new Myobj; # constructor 278 279 # scalar type accessor: 280 $element_value = $obj->s; # element value 281 $obj->s('new value'); # assign to element 282 283 # array type accessor: 284 $ary_ref = $obj->a; # reference to whole array 285 $ary_element_value = $obj->a(2); # array element value 286 $obj->a(2, 'new value'); # assign to array element 287 288 # hash type accessor: 289 $hash_ref = $obj->h; # reference to whole hash 290 $hash_element_value = $obj->h('x'); # hash element value 291 $obj->h('x', 'new value'); # assign to hash element 292 293 # class type accessor: 294 $element_value = $obj->c; # object reference 295 $obj->c->method(...); # call method of object 296 $obj->c(new My_Other_Class); # assign a new object 297 298=head1 DESCRIPTION 299 300C<Class::Struct> exports a single function, C<struct>. 301Given a list of element names and types, and optionally 302a class name, C<struct> creates a Perl 5 class that implements 303a "struct-like" data structure. 304 305The new class is given a constructor method, C<new>, for creating 306struct objects. 307 308Each element in the struct data has an accessor method, which is 309used to assign to the element and to fetch its value. The 310default accessor can be overridden by declaring a C<sub> of the 311same name in the package. (See Example 2.) 312 313Each element's type can be scalar, array, hash, or class. 314 315=head2 The C<struct()> function 316 317The C<struct> function has three forms of parameter-list. 318 319 struct( CLASS_NAME => [ ELEMENT_LIST ]); 320 struct( CLASS_NAME => { ELEMENT_LIST }); 321 struct( ELEMENT_LIST ); 322 323The first and second forms explicitly identify the name of the 324class being created. The third form assumes the current package 325name as the class name. 326 327An object of a class created by the first and third forms is 328based on an array, whereas an object of a class created by the 329second form is based on a hash. The array-based forms will be 330somewhat faster and smaller; the hash-based forms are more 331flexible. 332 333The class created by C<struct> must not be a subclass of another 334class other than C<UNIVERSAL>. 335 336It can, however, be used as a superclass for other classes. To facilitate 337this, the generated constructor method uses a two-argument blessing. 338Furthermore, if the class is hash-based, the key of each element is 339prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12). 340 341A function named C<new> must not be explicitly defined in a class 342created by C<struct>. 343 344The I<ELEMENT_LIST> has the form 345 346 NAME => TYPE, ... 347 348Each name-type pair declares one element of the struct. Each 349element name will be defined as an accessor method unless a 350method by that name is explicitly defined; in the latter case, a 351warning is issued if the warning flag (B<-w>) is set. 352 353=head2 Class Creation at Compile Time 354 355C<Class::Struct> can create your class at compile time. The main reason 356for doing this is obvious, so your class acts like every other class in 357Perl. Creating your class at compile time will make the order of events 358similar to using any other class ( or Perl module ). 359 360There is no significant speed gain between compile time and run time 361class creation, there is just a new, more standard order of events. 362 363=head2 Element Types and Accessor Methods 364 365The four element types -- scalar, array, hash, and class -- are 366represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name -- 367optionally preceded by a C<'*'>. 368 369The accessor method provided by C<struct> for an element depends 370on the declared type of the element. 371 372=over 4 373 374=item Scalar (C<'$'> or C<'*$'>) 375 376The element is a scalar, and by default is initialized to C<undef> 377(but see L<Initializing with new>). 378 379The accessor's argument, if any, is assigned to the element. 380 381If the element type is C<'$'>, the value of the element (after 382assignment) is returned. If the element type is C<'*$'>, a reference 383to the element is returned. 384 385=item Array (C<'@'> or C<'*@'>) 386 387The element is an array, initialized by default to C<()>. 388 389With no argument, the accessor returns a reference to the 390element's whole array (whether or not the element was 391specified as C<'@'> or C<'*@'>). 392 393With one or two arguments, the first argument is an index 394specifying one element of the array; the second argument, if 395present, is assigned to the array element. If the element type 396is C<'@'>, the accessor returns the array element value. If the 397element type is C<'*@'>, a reference to the array element is 398returned. 399 400As a special case, when the accessor is called with an array reference 401as the sole argument, this causes an assignment of the whole array element. 402The object reference is returned. 403 404=item Hash (C<'%'> or C<'*%'>) 405 406The element is a hash, initialized by default to C<()>. 407 408With no argument, the accessor returns a reference to the 409element's whole hash (whether or not the element was 410specified as C<'%'> or C<'*%'>). 411 412With one or two arguments, the first argument is a key specifying 413one element of the hash; the second argument, if present, is 414assigned to the hash element. If the element type is C<'%'>, the 415accessor returns the hash element value. If the element type is 416C<'*%'>, a reference to the hash element is returned. 417 418As a special case, when the accessor is called with a hash reference 419as the sole argument, this causes an assignment of the whole hash element. 420The object reference is returned. 421 422=item Class (C<'Class_Name'> or C<'*Class_Name'>) 423 424The element's value must be a reference blessed to the named 425class or to one of its subclasses. The element is not initialized 426by default. 427 428The accessor's argument, if any, is assigned to the element. The 429accessor will C<croak> if this is not an appropriate object 430reference. 431 432If the element type does not start with a C<'*'>, the accessor 433returns the element value (after assignment). If the element type 434starts with a C<'*'>, a reference to the element itself is returned. 435 436=back 437 438=head2 Initializing with C<new> 439 440C<struct> always creates a constructor called C<new>. That constructor 441may take a list of initializers for the various elements of the new 442struct. 443 444Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>. 445The initializer value for a scalar element is just a scalar value. The 446initializer for an array element is an array reference. The initializer 447for a hash is a hash reference. 448 449The initializer for a class element is an object of the corresponding class, 450or of one of it's subclasses, or a reference to a hash containing named 451arguments to be passed to the element's constructor. 452 453See Example 3 below for an example of initialization. 454 455=head1 EXAMPLES 456 457=over 4 458 459=item Example 1 460 461Giving a struct element a class type that is also a struct is how 462structs are nested. Here, C<Timeval> represents a time (seconds and 463microseconds), and C<Rusage> has two elements, each of which is of 464type C<Timeval>. 465 466 use Class::Struct; 467 468 struct( Rusage => { 469 ru_utime => 'Timeval', # user time used 470 ru_stime => 'Timeval', # system time used 471 }); 472 473 struct( Timeval => [ 474 tv_secs => '$', # seconds 475 tv_usecs => '$', # microseconds 476 ]); 477 478 # create an object: 479 my $t = Rusage->new(ru_utime=>Timeval->new(), ru_stime=>Timeval->new()); 480 481 # $t->ru_utime and $t->ru_stime are objects of type Timeval. 482 # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec. 483 $t->ru_utime->tv_secs(100); 484 $t->ru_utime->tv_usecs(0); 485 $t->ru_stime->tv_secs(5); 486 $t->ru_stime->tv_usecs(0); 487 488=item Example 2 489 490An accessor function can be redefined in order to provide 491additional checking of values, etc. Here, we want the C<count> 492element always to be nonnegative, so we redefine the C<count> 493accessor accordingly. 494 495 package MyObj; 496 use Class::Struct; 497 498 # declare the struct 499 struct ( 'MyObj', { count => '$', stuff => '%' } ); 500 501 # override the default accessor method for 'count' 502 sub count { 503 my $self = shift; 504 if ( @_ ) { 505 die 'count must be nonnegative' if $_[0] < 0; 506 $self->{'MyObj::count'} = shift; 507 warn "Too many args to count" if @_; 508 } 509 return $self->{'MyObj::count'}; 510 } 511 512 package main; 513 $x = new MyObj; 514 print "\$x->count(5) = ", $x->count(5), "\n"; 515 # prints '$x->count(5) = 5' 516 517 print "\$x->count = ", $x->count, "\n"; 518 # prints '$x->count = 5' 519 520 print "\$x->count(-5) = ", $x->count(-5), "\n"; 521 # dies due to negative argument! 522 523=item Example 3 524 525The constructor of a generated class can be passed a list 526of I<element>=>I<value> pairs, with which to initialize the struct. 527If no initializer is specified for a particular element, its default 528initialization is performed instead. Initializers for non-existent 529elements are silently ignored. 530 531Note that the initializer for a nested class may be specified as 532an object of that class, or as a reference to a hash of initializers 533that are passed on to the nested struct's constructor. 534 535 use Class::Struct; 536 537 struct Breed => 538 { 539 name => '$', 540 cross => '$', 541 }; 542 543 struct Cat => 544 [ 545 name => '$', 546 kittens => '@', 547 markings => '%', 548 breed => 'Breed', 549 ]; 550 551 552 my $cat = Cat->new( name => 'Socks', 553 kittens => ['Monica', 'Kenneth'], 554 markings => { socks=>1, blaze=>"white" }, 555 breed => Breed->new(name=>'short-hair', cross=>1), 556 or: breed => {name=>'short-hair', cross=>1}, 557 ); 558 559 print "Once a cat called ", $cat->name, "\n"; 560 print "(which was a ", $cat->breed->name, ")\n"; 561 print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n"; 562 563=back 564 565=head1 Author and Modification History 566 567Modified by Damian Conway, 2001-09-10, v0.62. 568 569 Modified implicit construction of nested objects. 570 Now will also take an object ref instead of requiring a hash ref. 571 Also default initializes nested object attributes to undef, rather 572 than calling object constructor without args 573 Original over-helpfulness was fraught with problems: 574 * the class's constructor might not be called 'new' 575 * the class might not have a hash-like-arguments constructor 576 * the class might not have a no-argument constructor 577 * "recursive" data structures didn't work well: 578 package Person; 579 struct { mother => 'Person', father => 'Person'}; 580 581 582Modified by Casey West, 2000-11-08, v0.59. 583 584 Added the ability for compile time class creation. 585 586Modified by Damian Conway, 1999-03-05, v0.58. 587 588 Added handling of hash-like arg list to class ctor. 589 590 Changed to two-argument blessing in ctor to support 591 derivation from created classes. 592 593 Added classname prefixes to keys in hash-based classes 594 (refer to "Perl Cookbook", Recipe 13.12 for rationale). 595 596 Corrected behaviour of accessors for '*@' and '*%' struct 597 elements. Package now implements documented behaviour when 598 returning a reference to an entire hash or array element. 599 Previously these were returned as a reference to a reference 600 to the element. 601 602Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02. 603 604 members() function removed. 605 Documentation corrected and extended. 606 Use of struct() in a subclass prohibited. 607 User definition of accessor allowed. 608 Treatment of '*' in element types corrected. 609 Treatment of classes as element types corrected. 610 Class name to struct() made optional. 611 Diagnostic checks added. 612 613Originally C<Class::Template> by Dean Roehrich. 614 615 # Template.pm --- struct/member template builder 616 # 12mar95 617 # Dean Roehrich 618 # 619 # changes/bugs fixed since 28nov94 version: 620 # - podified 621 # changes/bugs fixed since 21nov94 version: 622 # - Fixed examples. 623 # changes/bugs fixed since 02sep94 version: 624 # - Moved to Class::Template. 625 # changes/bugs fixed since 20feb94 version: 626 # - Updated to be a more proper module. 627 # - Added "use strict". 628 # - Bug in build_methods, was using @var when @$var needed. 629 # - Now using my() rather than local(). 630 # 631 # Uses perl5 classes to create nested data types. 632 # This is offered as one implementation of Tom Christiansen's "structs.pl" 633 # idea. 634 635=cut 636