628 lines
20 KiB
Perl
628 lines
20 KiB
Perl
package Class::Struct;
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## See POD after __END__
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use strict;
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use warnings::register;
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our(@ISA, @EXPORT, $VERSION);
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require Exporter;
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@ISA = qw(Exporter);
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@EXPORT = qw(struct);
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$VERSION = '0.63';
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my $print = 0;
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sub printem {
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if (@_) { $print = shift }
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else { $print++ }
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}
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{
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package Class::Struct::Tie_ISA;
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sub TIEARRAY {
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my $class = shift;
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return bless \@(), $class;
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}
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sub STORE {
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my ($self, $index, $value) = @_;
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Class::Struct::_subclass_error();
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}
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sub FETCH {
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my ($self, $index) = @_;
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$self->[$index];
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}
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sub FETCHSIZE {
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my $self = shift;
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return scalar(@$self);
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}
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sub DESTROY { }
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}
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sub import {
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my $self = shift;
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if ( @_ == 0 ) {
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$self->export_to_level( 1, $self, @EXPORT );
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} elsif ( @_ == 1 ) {
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# This is admittedly a little bit silly:
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# do we ever export anything else than 'struct'...?
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$self->export_to_level( 1, $self, @_ );
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} else {
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goto &struct;
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}
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}
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sub struct {
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# Determine parameter list structure, one of:
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# struct( class => [ element-list ])
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# struct( class => { element-list })
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# struct( element-list )
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# Latter form assumes current package name as struct name.
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my ($class, @decls);
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my $base_type = ref @_[1];
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if ( $base_type eq 'HASH' ) {
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$class = shift;
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@decls = %{shift()};
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_usage_error() if @_;
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}
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elsif ( $base_type eq 'ARRAY' ) {
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$class = shift;
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@decls = @{shift()};
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_usage_error() if @_;
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}
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else {
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$base_type = 'ARRAY';
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$class = (caller())[[0]];
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@decls = @_;
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}
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_usage_error() if @decls % 2 == 1;
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# Ensure we are not, and will not be, a subclass.
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my $isa = do {
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no strict 'refs';
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\@{*{Symbol::fetch_glob($class . '::ISA')}};
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};
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_subclass_error() if @$isa;
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tie @$isa, 'Class::Struct::Tie_ISA';
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# Create constructor.
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die "function 'new' already defined in package $class"
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if do { no strict 'refs'; defined &{Symbol::fetch_glob($class . "::new")} };
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my @methods = ();
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my %refs = ();
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my %arrays = ();
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my %hashes = ();
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my %classes = ();
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my $got_class = 0;
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my $out = '';
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$out = "\{\n package $class;\n sub new \{\n";
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$out .= " my (\$class, \%init) = \@_;\n";
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$out .= " \$class = __PACKAGE__ unless \@_;\n";
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my $cnt = 0;
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my $idx = 0;
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my( $cmt, $name, $type, $elem );
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if( $base_type eq 'HASH' ){
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$out .= ' my($r) = \%();'."\n";
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$cmt = '';
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}
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elsif( $base_type eq 'ARRAY' ){
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$out .= ' my($r) = \@();'."\n";
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}
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while( $idx +< @decls ){
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$name = @decls[$idx];
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$type = @decls[$idx+1];
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push( @methods, $name );
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if( $base_type eq 'HASH' ){
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$elem = "\{'{$class}::$name'\}";
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}
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elsif( $base_type eq 'ARRAY' ){
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$elem = "[$cnt]";
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++$cnt;
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$cmt = " # $name";
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}
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if( $type =~ m/^\*(.)/ ){
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%refs{$name}++;
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$type = $1;
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}
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my $init = "defined(\%init\{'$name'\}) ? \%init\{'$name'\} :";
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if( $type eq '@' ){
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$out .= " die 'Initializer for $name must be array reference'\n";
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$out .= " if defined(\%init\{'$name'\}) && ref(\%init\{'$name'\}) ne 'ARRAY';\n";
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$out .= " \$r->$elem = $init \\\@();$cmt\n";
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%arrays{$name}++;
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}
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elsif( $type eq '%' ){
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$out .= " die 'Initializer for $name must be hash reference'\n";
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$out .= " if defined(\%init\{'$name'\}) && ref(\%init\{'$name'\}) ne 'HASH';\n";
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$out .= " \$r->$elem = $init \\\%();$cmt\n";
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%hashes{$name}++;
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}
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elsif ( $type eq '$') {
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$out .= " \$r->$elem = $init undef;$cmt\n";
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}
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elsif( $type =~ m/^\w+(?:::\w+)*$/ ){
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$out .= " if (defined(\%init\{'$name'\})) \{\n";
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$out .= " if (ref \%init\{'$name'\} eq 'HASH')\n";
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$out .= " \{ \$r->$elem = $type->new(\%\{\%init\{'$name'\}\}) \} $cmt\n";
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$out .= " elsif (UNIVERSAL::isa(\%init\{'$name'\}, '$type'))\n";
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$out .= " \{ \$r->$elem = \%init\{'$name'\} \} $cmt\n";
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$out .= " else \{ die 'Initializer for $name must be hash or $type reference' \}\n";
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$out .= " \}\n";
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%classes{$name} = $type;
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$got_class = 1;
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}
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else{
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die "'$type' is not a valid struct element type";
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}
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$idx += 2;
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}
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$out .= " bless \$r, \$class;\n \}\n";
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# Create accessor methods.
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my( $pre, $pst, $sel );
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$cnt = 0;
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foreach $name (@methods){
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if ( do { no strict 'refs'; defined &{Symbol::fetch_glob($class . "::$name")} } ) {
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warnings::warnif("function '$name' already defined, overrides struct accessor method");
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}
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else {
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$pre = $pst = $cmt = $sel = '';
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if( defined %refs{$name} ){
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$pre = "\\(";
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$pst = ")";
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$cmt = " # returns ref";
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}
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$out .= " sub $name \{$cmt\n my \$r = shift;\n";
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if( $base_type eq 'ARRAY' ){
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$elem = "[$cnt]";
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++$cnt;
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}
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elsif( $base_type eq 'HASH' ){
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$elem = "\{'{$class}::$name'\}";
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}
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if( defined %arrays{$name} ){
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$out .= " my \$i;\n";
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$out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
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$out .= " if (ref(\$i) eq 'ARRAY' && !\@_) \{ \$r->$elem = \$i; return \$r \}\n";
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$sel = "->[\$i]";
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}
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elsif( defined %hashes{$name} ){
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$out .= " my \$i;\n";
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$out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
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$out .= " if (ref(\$i) eq 'HASH' && !\@_) \{ \$r->$elem = \$i; return \$r \}\n";
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$sel = "->\{\$i\}";
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}
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elsif( defined %classes{$name} ){
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$out .= " die '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\@_[0], '%classes{$name}');\n";
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}
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$out .= " die 'Too many args to $name' if \@_ +> 1;\n";
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$out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n";
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$out .= " \}\n";
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}
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}
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$out .= "\}\n1;\n";
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print $out if $print;
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my $result = eval $out;
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warn $@ if $@;
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}
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sub _usage_error {
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die "struct usage error";
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}
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sub _subclass_error {
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die 'struct class cannot be a subclass (@ISA not allowed)';
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}
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1; # for require
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__END__
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=head1 NAME
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Class::Struct - declare struct-like datatypes as Perl classes
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=head1 SYNOPSIS
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use Class::Struct;
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# declare struct, based on array:
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struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
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# declare struct, based on hash:
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struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });
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package CLASS_NAME;
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use Class::Struct;
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# declare struct, based on array, implicit class name:
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struct( ELEMENT_NAME => ELEMENT_TYPE, ... );
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# Declare struct at compile time
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use Class::Struct CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ];
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use Class::Struct CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... };
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# declare struct at compile time, based on array, implicit class name:
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package CLASS_NAME;
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use Class::Struct ELEMENT_NAME => ELEMENT_TYPE, ... ;
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package Myobj;
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use Class::Struct;
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# declare struct with four types of elements:
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struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );
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$obj = new Myobj; # constructor
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# scalar type accessor:
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$element_value = $obj->s; # element value
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$obj->s('new value'); # assign to element
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# array type accessor:
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$ary_ref = $obj->a; # reference to whole array
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$ary_element_value = $obj->a(2); # array element value
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$obj->a(2, 'new value'); # assign to array element
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# hash type accessor:
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$hash_ref = $obj->h; # reference to whole hash
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$hash_element_value = $obj->h('x'); # hash element value
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$obj->h('x', 'new value'); # assign to hash element
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# class type accessor:
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$element_value = $obj->c; # object reference
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$obj->c->method(...); # call method of object
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$obj->c(new My_Other_Class); # assign a new object
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=head1 DESCRIPTION
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C<Class::Struct> exports a single function, C<struct>.
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Given a list of element names and types, and optionally
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a class name, C<struct> creates a Perl 5 class that implements
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a "struct-like" data structure.
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The new class is given a constructor method, C<new>, for creating
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struct objects.
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Each element in the struct data has an accessor method, which is
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used to assign to the element and to fetch its value. The
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default accessor can be overridden by declaring a C<sub> of the
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same name in the package. (See Example 2.)
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Each element's type can be scalar, array, hash, or class.
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=head2 The C<struct()> function
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The C<struct> function has three forms of parameter-list.
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struct( CLASS_NAME => [ ELEMENT_LIST ]);
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struct( CLASS_NAME => { ELEMENT_LIST });
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struct( ELEMENT_LIST );
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The first and second forms explicitly identify the name of the
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class being created. The third form assumes the current package
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name as the class name.
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An object of a class created by the first and third forms is
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based on an array, whereas an object of a class created by the
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second form is based on a hash. The array-based forms will be
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somewhat faster and smaller; the hash-based forms are more
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flexible.
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The class created by C<struct> must not be a subclass of another
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class other than C<UNIVERSAL>.
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It can, however, be used as a superclass for other classes. To facilitate
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this, the generated constructor method uses a two-argument blessing.
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Furthermore, if the class is hash-based, the key of each element is
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prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12).
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A function named C<new> must not be explicitly defined in a class
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created by C<struct>.
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The I<ELEMENT_LIST> has the form
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NAME => TYPE, ...
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Each name-type pair declares one element of the struct. Each
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element name will be defined as an accessor method unless a
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method by that name is explicitly defined; in the latter case, a
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warning is issued if the warning flag (B<-w>) is set.
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=head2 Class Creation at Compile Time
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C<Class::Struct> can create your class at compile time. The main reason
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for doing this is obvious, so your class acts like every other class in
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Perl. Creating your class at compile time will make the order of events
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similar to using any other class ( or Perl module ).
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There is no significant speed gain between compile time and run time
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class creation, there is just a new, more standard order of events.
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=head2 Element Types and Accessor Methods
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The four element types -- scalar, array, hash, and class -- are
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represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name --
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optionally preceded by a C<'*'>.
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The accessor method provided by C<struct> for an element depends
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on the declared type of the element.
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=over 4
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=item Scalar (C<'$'> or C<'*$'>)
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The element is a scalar, and by default is initialized to C<undef>
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(but see L<Initializing with new>).
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The accessor's argument, if any, is assigned to the element.
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If the element type is C<'$'>, the value of the element (after
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assignment) is returned. If the element type is C<'*$'>, a reference
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to the element is returned.
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=item Array (C<'@'> or C<'*@'>)
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The element is an array, initialized by default to C<()>.
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With no argument, the accessor returns a reference to the
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element's whole array (whether or not the element was
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specified as C<'@'> or C<'*@'>).
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With one or two arguments, the first argument is an index
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specifying one element of the array; the second argument, if
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present, is assigned to the array element. If the element type
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is C<'@'>, the accessor returns the array element value. If the
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element type is C<'*@'>, a reference to the array element is
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returned.
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As a special case, when the accessor is called with an array reference
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as the sole argument, this causes an assignment of the whole array element.
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The object reference is returned.
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=item Hash (C<'%'> or C<'*%'>)
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The element is a hash, initialized by default to C<()>.
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With no argument, the accessor returns a reference to the
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element's whole hash (whether or not the element was
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specified as C<'%'> or C<'*%'>).
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With one or two arguments, the first argument is a key specifying
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one element of the hash; the second argument, if present, is
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assigned to the hash element. If the element type is C<'%'>, the
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accessor returns the hash element value. If the element type is
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C<'*%'>, a reference to the hash element is returned.
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As a special case, when the accessor is called with a hash reference
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as the sole argument, this causes an assignment of the whole hash element.
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The object reference is returned.
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=item Class (C<'Class_Name'> or C<'*Class_Name'>)
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The element's value must be a reference blessed to the named
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class or to one of its subclasses. The element is not initialized
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by default.
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The accessor's argument, if any, is assigned to the element. The
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accessor will C<die> if this is not an appropriate object
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reference.
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If the element type does not start with a C<'*'>, the accessor
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returns the element value (after assignment). If the element type
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starts with a C<'*'>, a reference to the element itself is returned.
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=back
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=head2 Initializing with C<new>
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C<struct> always creates a constructor called C<new>. That constructor
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may take a list of initializers for the various elements of the new
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struct.
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Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>.
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The initializer value for a scalar element is just a scalar value. The
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initializer for an array element is an array reference. The initializer
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for a hash is a hash reference.
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The initializer for a class element is an object of the corresponding class,
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or of one of it's subclasses, or a reference to a hash containing named
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arguments to be passed to the element's constructor.
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See Example 3 below for an example of initialization.
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=head1 EXAMPLES
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=over 4
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=item Example 1
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Giving a struct element a class type that is also a struct is how
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structs are nested. Here, C<Timeval> represents a time (seconds and
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microseconds), and C<Rusage> has two elements, each of which is of
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type C<Timeval>.
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use Class::Struct;
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struct( Rusage => {
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ru_utime => 'Timeval', # user time used
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ru_stime => 'Timeval', # system time used
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});
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struct( Timeval => [
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tv_secs => '$', # seconds
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tv_usecs => '$', # microseconds
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]);
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# create an object:
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my $t = Rusage->new(ru_utime=>Timeval->new(), ru_stime=>Timeval->new());
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# $t->ru_utime and $t->ru_stime are objects of type Timeval.
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# set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
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$t->ru_utime->tv_secs(100);
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$t->ru_utime->tv_usecs(0);
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$t->ru_stime->tv_secs(5);
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$t->ru_stime->tv_usecs(0);
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=item Example 2
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An accessor function can be redefined in order to provide
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additional checking of values, etc. Here, we want the C<count>
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element always to be nonnegative, so we redefine the C<count>
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accessor accordingly.
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package MyObj;
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use Class::Struct;
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# declare the struct
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struct ( 'MyObj', { count => '$', stuff => '%' } );
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# override the default accessor method for 'count'
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sub count {
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my $self = shift;
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if ( @_ ) {
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die 'count must be nonnegative' if $_[0] < 0;
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$self->{'MyObj::count'} = shift;
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warn "Too many args to count" if @_;
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}
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return $self->{'MyObj::count'};
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}
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package main;
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$x = new MyObj;
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print "\$x->count(5) = ", $x->count(5), "\n";
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# prints '$x->count(5) = 5'
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print "\$x->count = ", $x->count, "\n";
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# prints '$x->count = 5'
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|
|
|
print "\$x->count(-5) = ", $x->count(-5), "\n";
|
|
# dies due to negative argument!
|
|
|
|
=item Example 3
|
|
|
|
The constructor of a generated class can be passed a list
|
|
of I<element>=>I<value> pairs, with which to initialize the struct.
|
|
If no initializer is specified for a particular element, its default
|
|
initialization is performed instead. Initializers for non-existent
|
|
elements are silently ignored.
|
|
|
|
Note that the initializer for a nested class may be specified as
|
|
an object of that class, or as a reference to a hash of initializers
|
|
that are passed on to the nested struct's constructor.
|
|
|
|
use Class::Struct;
|
|
|
|
struct Breed =>
|
|
{
|
|
name => '$',
|
|
cross => '$',
|
|
};
|
|
|
|
struct Cat =>
|
|
[
|
|
name => '$',
|
|
kittens => '@',
|
|
markings => '%',
|
|
breed => 'Breed',
|
|
];
|
|
|
|
|
|
my $cat = Cat->new( name => 'Socks',
|
|
kittens => ['Monica', 'Kenneth'],
|
|
markings => { socks=>1, blaze=>"white" },
|
|
breed => Breed->new(name=>'short-hair', cross=>1),
|
|
or: breed => {name=>'short-hair', cross=>1},
|
|
);
|
|
|
|
print "Once a cat called ", $cat->name, "\n";
|
|
print "(which was a ", $cat->breed->name, ")\n";
|
|
print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n";
|
|
|
|
=back
|
|
|
|
=head1 Author and Modification History
|
|
|
|
Modified by Damian Conway, 2001-09-10, v0.62.
|
|
|
|
Modified implicit construction of nested objects.
|
|
Now will also take an object ref instead of requiring a hash ref.
|
|
Also default initializes nested object attributes to undef, rather
|
|
than calling object constructor without args
|
|
Original over-helpfulness was fraught with problems:
|
|
* the class's constructor might not be called 'new'
|
|
* the class might not have a hash-like-arguments constructor
|
|
* the class might not have a no-argument constructor
|
|
* "recursive" data structures didn't work well:
|
|
package Person;
|
|
struct { mother => 'Person', father => 'Person'};
|
|
|
|
|
|
Modified by Casey West, 2000-11-08, v0.59.
|
|
|
|
Added the ability for compile time class creation.
|
|
|
|
Modified by Damian Conway, 1999-03-05, v0.58.
|
|
|
|
Added handling of hash-like arg list to class ctor.
|
|
|
|
Changed to two-argument blessing in ctor to support
|
|
derivation from created classes.
|
|
|
|
Added classname prefixes to keys in hash-based classes
|
|
(refer to "Perl Cookbook", Recipe 13.12 for rationale).
|
|
|
|
Corrected behaviour of accessors for '*@' and '*%' struct
|
|
elements. Package now implements documented behaviour when
|
|
returning a reference to an entire hash or array element.
|
|
Previously these were returned as a reference to a reference
|
|
to the element.
|
|
|
|
Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02.
|
|
|
|
members() function removed.
|
|
Documentation corrected and extended.
|
|
Use of struct() in a subclass prohibited.
|
|
User definition of accessor allowed.
|
|
Treatment of '*' in element types corrected.
|
|
Treatment of classes as element types corrected.
|
|
Class name to struct() made optional.
|
|
Diagnostic checks added.
|
|
|
|
Originally C<Class::Template> by Dean Roehrich.
|
|
|
|
# Template.pm --- struct/member template builder
|
|
# 12mar95
|
|
# Dean Roehrich
|
|
#
|
|
# changes/bugs fixed since 28nov94 version:
|
|
# - podified
|
|
# changes/bugs fixed since 21nov94 version:
|
|
# - Fixed examples.
|
|
# changes/bugs fixed since 02sep94 version:
|
|
# - Moved to Class::Template.
|
|
# changes/bugs fixed since 20feb94 version:
|
|
# - Updated to be a more proper module.
|
|
# - Added "use strict".
|
|
# - Bug in build_methods, was using @var when @$var needed.
|
|
# - Now using my() rather than local().
|
|
#
|
|
# Uses perl5 classes to create nested data types.
|
|
# This is offered as one implementation of Tom Christiansen's "structs.pl"
|
|
# idea.
|
|
|
|
=cut
|