--- /dev/null
+package Attribute::Handlers;
+use 5.006;
+use Carp;
+use warnings;
+$VERSION = '0.76';
+# $DB::single=1;
+
+my %symcache;
+sub findsym {
+ my ($pkg, $ref, $type) = @_;
+ return $symcache{$pkg,$ref} if $symcache{$pkg,$ref};
+ $type ||= ref($ref);
+ my $found;
+ foreach my $sym ( values %{$pkg."::"} ) {
+ return $symcache{$pkg,$ref} = \$sym
+ if *{$sym}{$type} && *{$sym}{$type} == $ref;
+ }
+}
+
+my %validtype = (
+ VAR => [qw[SCALAR ARRAY HASH]],
+ ANY => [qw[SCALAR ARRAY HASH CODE]],
+ "" => [qw[SCALAR ARRAY HASH CODE]],
+ SCALAR => [qw[SCALAR]],
+ ARRAY => [qw[ARRAY]],
+ HASH => [qw[HASH]],
+ CODE => [qw[CODE]],
+);
+my %lastattr;
+my @declarations;
+my %raw;
+my %phase;
+my %sigil = (SCALAR=>'$', ARRAY=>'@', HASH=>'%');
+my $global_phase = 0;
+my %global_phases = (
+ BEGIN => 0,
+ CHECK => 1,
+ INIT => 2,
+ END => 3,
+);
+my @global_phases = qw(BEGIN CHECK INIT END);
+
+sub _usage_AH_ {
+ croak "Usage: use $_[0] autotie => {AttrName => TieClassName,...}";
+}
+
+my $qual_id = qr/^[_a-z]\w*(::[_a-z]\w*)*$/i;
+
+sub import {
+ my $class = shift @_;
+ return unless $class eq "Attribute::Handlers";
+ while (@_) {
+ my $cmd = shift;
+ if ($cmd =~ /^autotie((?:ref)?)$/) {
+ my $tiedata = ($1 ? '$ref, ' : '') . '@$data';
+ my $mapping = shift;
+ _usage_AH_ $class unless ref($mapping) eq 'HASH';
+ while (my($attr, $tieclass) = each %$mapping) {
+ $tieclass =~ s/^([_a-z]\w*(::[_a-z]\w*)*)(.*)/$1/is;
+ my $args = $3||'()';
+ _usage_AH_ $class unless $attr =~ $qual_id
+ && $tieclass =~ $qual_id
+ && eval "use base $tieclass; 1";
+ if ($tieclass->isa('Exporter')) {
+ local $Exporter::ExportLevel = 2;
+ $tieclass->import(eval $args);
+ }
+ $attr =~ s/__CALLER__/caller(1)/e;
+ $attr = caller()."::".$attr unless $attr =~ /::/;
+ eval qq{
+ sub $attr : ATTR(VAR) {
+ my (\$ref, \$data) = \@_[2,4];
+ my \$was_arrayref = ref \$data eq 'ARRAY';
+ \$data = [ \$data ] unless \$was_arrayref;
+ my \$type = ref(\$ref)||"value (".(\$ref||"<undef>").")";
+ (\$type eq 'SCALAR')? tie \$\$ref,'$tieclass',$tiedata
+ :(\$type eq 'ARRAY') ? tie \@\$ref,'$tieclass',$tiedata
+ :(\$type eq 'HASH') ? tie \%\$ref,'$tieclass',$tiedata
+ : die "Can't autotie a \$type\n"
+ } 1
+ } or die "Internal error: $@";
+ }
+ }
+ else {
+ croak "Can't understand $_";
+ }
+ }
+}
+sub _resolve_lastattr {
+ return unless $lastattr{ref};
+ my $sym = findsym @lastattr{'pkg','ref'}
+ or die "Internal error: $lastattr{pkg} symbol went missing";
+ my $name = *{$sym}{NAME};
+ warn "Declaration of $name attribute in package $lastattr{pkg} may clash with future reserved word\n"
+ if $^W and $name !~ /[A-Z]/;
+ foreach ( @{$validtype{$lastattr{type}}} ) {
+ *{"$lastattr{pkg}::_ATTR_${_}_${name}"} = $lastattr{ref};
+ }
+ %lastattr = ();
+}
+
+sub AUTOLOAD {
+ my ($class) = $AUTOLOAD =~ m/(.*)::/g;
+ $AUTOLOAD =~ m/_ATTR_(.*?)_(.*)/ or
+ croak "Can't locate class method '$AUTOLOAD' via package '$class'";
+ croak "Attribute handler '$3' doesn't handle $2 attributes";
+}
+
+sub DESTROY {}
+
+my $builtin = qr/lvalue|method|locked/;
+
+sub _gen_handler_AH_() {
+ return sub {
+ _resolve_lastattr;
+ my ($pkg, $ref, @attrs) = @_;
+ foreach (@attrs) {
+ my ($attr, $data) = /^([a-z_]\w*)(?:[(](.*)[)])?$/is or next;
+ if ($attr eq 'ATTR') {
+ $data ||= "ANY";
+ $raw{$ref} = $data =~ s/\s*,?\s*RAWDATA\s*,?\s*//;
+ $phase{$ref}{BEGIN} = 1
+ if $data =~ s/\s*,?\s*(BEGIN)\s*,?\s*//;
+ $phase{$ref}{INIT} = 1
+ if $data =~ s/\s*,?\s*(INIT)\s*,?\s*//;
+ $phase{$ref}{END} = 1
+ if $data =~ s/\s*,?\s*(END)\s*,?\s*//;
+ $phase{$ref}{CHECK} = 1
+ if $data =~ s/\s*,?\s*(CHECK)\s*,?\s*//
+ || ! keys %{$phase{$ref}};
+ # Added for cleanup to not pollute next call.
+ (%lastattr = ()),
+ croak "Can't have two ATTR specifiers on one subroutine"
+ if keys %lastattr;
+ croak "Bad attribute type: ATTR($data)"
+ unless $validtype{$data};
+ %lastattr=(pkg=>$pkg,ref=>$ref,type=>$data);
+ }
+ else {
+ my $handler = $pkg->can($attr);
+ next unless $handler;
+ my $decl = [$pkg, $ref, $attr, $data,
+ $raw{$handler}, $phase{$handler}];
+ foreach my $gphase (@global_phases) {
+ _apply_handler_AH_($decl,$gphase)
+ if $global_phases{$gphase} <= $global_phase;
+ }
+ push @declarations, $decl;
+ }
+ $_ = undef;
+ }
+ return grep {defined && !/$builtin/} @attrs;
+ }
+}
+
+*{"MODIFY_${_}_ATTRIBUTES"} = _gen_handler_AH_ foreach @{$validtype{ANY}};
+push @UNIVERSAL::ISA, 'Attribute::Handlers'
+ unless grep /^Attribute::Handlers$/, @UNIVERSAL::ISA;
+
+sub _apply_handler_AH_ {
+ my ($declaration, $phase) = @_;
+ my ($pkg, $ref, $attr, $data, $raw, $handlerphase) = @$declaration;
+ return unless $handlerphase->{$phase};
+ # print STDERR "Handling $attr on $ref in $phase with [$data]\n";
+ my $type = ref $ref;
+ my $handler = "_ATTR_${type}_${attr}";
+ my $sym = findsym($pkg, $ref);
+ $sym ||= $type eq 'CODE' ? 'ANON' : 'LEXICAL';
+ no warnings;
+ my $evaled = !$raw && eval("package $pkg; no warnings;
+ local \$SIG{__WARN__}=sub{die}; [$data]");
+ $data = ($evaled && $data =~ /^\s*\[/) ? [$evaled]
+ : ($evaled) ? $evaled
+ : [$data];
+ $pkg->$handler($sym,
+ (ref $sym eq 'GLOB' ? *{$sym}{ref $ref}||$ref : $ref),
+ $attr,
+ (@$data>1? $data : $data->[0]),
+ $phase,
+ );
+ return 1;
+}
+
+CHECK {
+ $global_phase++;
+ _resolve_lastattr;
+ _apply_handler_AH_($_,'CHECK') foreach @declarations;
+}
+
+INIT { $global_phase++; _apply_handler_AH_($_,'INIT') foreach @declarations }
+
+END { $global_phase++; _apply_handler_AH_($_,'END') foreach @declarations }
+
+1;
+__END__
+
+=head1 NAME
+
+Attribute::Handlers - Simpler definition of attribute handlers
+
+=head1 VERSION
+
+This document describes version 0.76 of Attribute::Handlers,
+released November 15, 2001.
+
+=head1 SYNOPSIS
+
+ package MyClass;
+ require v5.6.0;
+ use Attribute::Handlers;
+ no warnings 'redefine';
+
+
+ sub Good : ATTR(SCALAR) {
+ my ($package, $symbol, $referent, $attr, $data) = @_;
+
+ # Invoked for any scalar variable with a :Good attribute,
+ # provided the variable was declared in MyClass (or
+ # a derived class) or typed to MyClass.
+
+ # Do whatever to $referent here (executed in CHECK phase).
+ ...
+ }
+
+ sub Bad : ATTR(SCALAR) {
+ # Invoked for any scalar variable with a :Bad attribute,
+ # provided the variable was declared in MyClass (or
+ # a derived class) or typed to MyClass.
+ ...
+ }
+
+ sub Good : ATTR(ARRAY) {
+ # Invoked for any array variable with a :Good attribute,
+ # provided the variable was declared in MyClass (or
+ # a derived class) or typed to MyClass.
+ ...
+ }
+
+ sub Good : ATTR(HASH) {
+ # Invoked for any hash variable with a :Good attribute,
+ # provided the variable was declared in MyClass (or
+ # a derived class) or typed to MyClass.
+ ...
+ }
+
+ sub Ugly : ATTR(CODE) {
+ # Invoked for any subroutine declared in MyClass (or a
+ # derived class) with an :Ugly attribute.
+ ...
+ }
+
+ sub Omni : ATTR {
+ # Invoked for any scalar, array, hash, or subroutine
+ # with an :Omni attribute, provided the variable or
+ # subroutine was declared in MyClass (or a derived class)
+ # or the variable was typed to MyClass.
+ # Use ref($_[2]) to determine what kind of referent it was.
+ ...
+ }
+
+
+ use Attribute::Handlers autotie => { Cycle => Tie::Cycle };
+
+ my $next : Cycle(['A'..'Z']);
+
+
+=head1 DESCRIPTION
+
+This module, when inherited by a package, allows that package's class to
+define attribute handler subroutines for specific attributes. Variables
+and subroutines subsequently defined in that package, or in packages
+derived from that package may be given attributes with the same names as
+the attribute handler subroutines, which will then be called in one of
+the compilation phases (i.e. in a C<BEGIN>, C<CHECK>, C<INIT>, or C<END>
+block).
+
+To create a handler, define it as a subroutine with the same name as
+the desired attribute, and declare the subroutine itself with the
+attribute C<:ATTR>. For example:
+
+ package LoudDecl;
+ use Attribute::Handlers;
+
+ sub Loud :ATTR {
+ my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
+ print STDERR
+ ref($referent), " ",
+ *{$symbol}{NAME}, " ",
+ "($referent) ", "was just declared ",
+ "and ascribed the ${attr} attribute ",
+ "with data ($data)\n",
+ "in phase $phase\n";
+ }
+
+This creates a handler for the attribute C<:Loud> in the class LoudDecl.
+Thereafter, any subroutine declared with a C<:Loud> attribute in the class
+LoudDecl:
+
+ package LoudDecl;
+
+ sub foo: Loud {...}
+
+causes the above handler to be invoked, and passed:
+
+=over
+
+=item [0]
+
+the name of the package into which it was declared;
+
+=item [1]
+
+a reference to the symbol table entry (typeglob) containing the subroutine;
+
+=item [2]
+
+a reference to the subroutine;
+
+=item [3]
+
+the name of the attribute;
+
+=item [4]
+
+any data associated with that attribute;
+
+=item [5]
+
+the name of the phase in which the handler is being invoked.
+
+=back
+
+Likewise, declaring any variables with the C<:Loud> attribute within the
+package:
+
+ package LoudDecl;
+
+ my $foo :Loud;
+ my @foo :Loud;
+ my %foo :Loud;
+
+will cause the handler to be called with a similar argument list (except,
+of course, that C<$_[2]> will be a reference to the variable).
+
+The package name argument will typically be the name of the class into
+which the subroutine was declared, but it may also be the name of a derived
+class (since handlers are inherited).
+
+If a lexical variable is given an attribute, there is no symbol table to
+which it belongs, so the symbol table argument (C<$_[1]>) is set to the
+string C<'LEXICAL'> in that case. Likewise, ascribing an attribute to
+an anonymous subroutine results in a symbol table argument of C<'ANON'>.
+
+The data argument passes in the value (if any) associated with the
+attribute. For example, if C<&foo> had been declared:
+
+ sub foo :Loud("turn it up to 11, man!") {...}
+
+then the string C<"turn it up to 11, man!"> would be passed as the
+last argument.
+
+Attribute::Handlers makes strenuous efforts to convert
+the data argument (C<$_[4]>) to a useable form before passing it to
+the handler (but see L<"Non-interpretive attribute handlers">).
+For example, all of these:
+
+ sub foo :Loud(till=>ears=>are=>bleeding) {...}
+ sub foo :Loud(['till','ears','are','bleeding']) {...}
+ sub foo :Loud(qw/till ears are bleeding/) {...}
+ sub foo :Loud(qw/my, ears, are, bleeding/) {...}
+ sub foo :Loud(till,ears,are,bleeding) {...}
+
+causes it to pass C<['till','ears','are','bleeding']> as the handler's
+data argument. However, if the data can't be parsed as valid Perl, then
+it is passed as an uninterpreted string. For example:
+
+ sub foo :Loud(my,ears,are,bleeding) {...}
+ sub foo :Loud(qw/my ears are bleeding) {...}
+
+cause the strings C<'my,ears,are,bleeding'> and C<'qw/my ears are bleeding'>
+respectively to be passed as the data argument.
+
+If the attribute has only a single associated scalar data value, that value is
+passed as a scalar. If multiple values are associated, they are passed as an
+array reference. If no value is associated with the attribute, C<undef> is
+passed.
+
+
+=head2 Typed lexicals
+
+Regardless of the package in which it is declared, if a lexical variable is
+ascribed an attribute, the handler that is invoked is the one belonging to
+the package to which it is typed. For example, the following declarations:
+
+ package OtherClass;
+
+ my LoudDecl $loudobj : Loud;
+ my LoudDecl @loudobjs : Loud;
+ my LoudDecl %loudobjex : Loud;
+
+causes the LoudDecl::Loud handler to be invoked (even if OtherClass also
+defines a handler for C<:Loud> attributes).
+
+
+=head2 Type-specific attribute handlers
+
+If an attribute handler is declared and the C<:ATTR> specifier is
+given the name of a built-in type (C<SCALAR>, C<ARRAY>, C<HASH>, or C<CODE>),
+the handler is only applied to declarations of that type. For example,
+the following definition:
+
+ package LoudDecl;
+
+ sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
+
+creates an attribute handler that applies only to scalars:
+
+
+ package Painful;
+ use base LoudDecl;
+
+ my $metal : RealLoud; # invokes &LoudDecl::RealLoud
+ my @metal : RealLoud; # error: unknown attribute
+ my %metal : RealLoud; # error: unknown attribute
+ sub metal : RealLoud {...} # error: unknown attribute
+
+You can, of course, declare separate handlers for these types as well
+(but you'll need to specify C<no warnings 'redefine'> to do it quietly):
+
+ package LoudDecl;
+ use Attribute::Handlers;
+ no warnings 'redefine';
+
+ sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
+ sub RealLoud :ATTR(ARRAY) { print "Urrrrrrrrrr!" }
+ sub RealLoud :ATTR(HASH) { print "Arrrrrgggghhhhhh!" }
+ sub RealLoud :ATTR(CODE) { croak "Real loud sub torpedoed" }
+
+You can also explicitly indicate that a single handler is meant to be
+used for all types of referents like so:
+
+ package LoudDecl;
+ use Attribute::Handlers;
+
+ sub SeriousLoud :ATTR(ANY) { warn "Hearing loss imminent" }
+
+(I.e. C<ATTR(ANY)> is a synonym for C<:ATTR>).
+
+
+=head2 Non-interpretive attribute handlers
+
+Occasionally the strenuous efforts Attribute::Handlers makes to convert
+the data argument (C<$_[4]>) to a useable form before passing it to
+the handler get in the way.
+
+You can turn off that eagerness-to-help by declaring
+an attribute handler with the keyword C<RAWDATA>. For example:
+
+ sub Raw : ATTR(RAWDATA) {...}
+ sub Nekkid : ATTR(SCALAR,RAWDATA) {...}
+ sub Au::Naturale : ATTR(RAWDATA,ANY) {...}
+
+Then the handler makes absolutely no attempt to interpret the data it
+receives and simply passes it as a string:
+
+ my $power : Raw(1..100); # handlers receives "1..100"
+
+=head2 Phase-specific attribute handlers
+
+By default, attribute handlers are called at the end of the compilation
+phase (in a C<CHECK> block). This seems to be optimal in most cases because
+most things that can be defined are defined by that point but nothing has
+been executed.
+
+However, it is possible to set up attribute handlers that are called at
+other points in the program's compilation or execution, by explicitly
+stating the phase (or phases) in which you wish the attribute handler to
+be called. For example:
+
+ sub Early :ATTR(SCALAR,BEGIN) {...}
+ sub Normal :ATTR(SCALAR,CHECK) {...}
+ sub Late :ATTR(SCALAR,INIT) {...}
+ sub Final :ATTR(SCALAR,END) {...}
+ sub Bookends :ATTR(SCALAR,BEGIN,END) {...}
+
+As the last example indicates, a handler may be set up to be (re)called in
+two or more phases. The phase name is passed as the handler's final argument.
+
+Note that attribute handlers that are scheduled for the C<BEGIN> phase
+are handled as soon as the attribute is detected (i.e. before any
+subsequently defined C<BEGIN> blocks are executed).
+
+
+=head2 Attributes as C<tie> interfaces
+
+Attributes make an excellent and intuitive interface through which to tie
+variables. For example:
+
+ use Attribute::Handlers;
+ use Tie::Cycle;
+
+ sub UNIVERSAL::Cycle : ATTR(SCALAR) {
+ my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
+ $data = [ $data ] unless ref $data eq 'ARRAY';
+ tie $$referent, 'Tie::Cycle', $data;
+ }
+
+ # and thereafter...
+
+ package main;
+
+ my $next : Cycle('A'..'Z'); # $next is now a tied variable
+
+ while (<>) {
+ print $next;
+ }
+
+Note that, because the C<Cycle> attribute receives its arguments in the
+C<$data> variable, if the attribute is given a list of arguments, C<$data>
+will consist of a single array reference; otherwise, it will consist of the
+single argument directly. Since Tie::Cycle requires its cycling values to
+be passed as an array reference, this means that we need to wrap
+non-array-reference arguments in an array constructor:
+
+ $data = [ $data ] unless ref $data eq 'ARRAY';
+
+Typically, however, things are the other way around: the tieable class expects
+its arguments as a flattened list, so the attribute looks like:
+
+ sub UNIVERSAL::Cycle : ATTR(SCALAR) {
+ my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
+ my @data = ref $data eq 'ARRAY' ? @$data : $data;
+ tie $$referent, 'Tie::Whatever', @data;
+ }
+
+
+This software pattern is so widely applicable that Attribute::Handlers
+provides a way to automate it: specifying C<'autotie'> in the
+C<use Attribute::Handlers> statement. So, the cycling example,
+could also be written:
+
+ use Attribute::Handlers autotie => { Cycle => 'Tie::Cycle' };
+
+ # and thereafter...
+
+ package main;
+
+ my $next : Cycle(['A'..'Z']); # $next is now a tied variable
+
+ while (<>) {
+ print $next;
+
+Note that we now have to pass the cycling values as an array reference,
+since the C<autotie> mechanism passes C<tie> a list of arguments as a list
+(as in the Tie::Whatever example), I<not> as an array reference (as in
+the original Tie::Cycle example at the start of this section).
+
+The argument after C<'autotie'> is a reference to a hash in which each key is
+the name of an attribute to be created, and each value is the class to which
+variables ascribed that attribute should be tied.
+
+Note that there is no longer any need to import the Tie::Cycle module --
+Attribute::Handlers takes care of that automagically. You can even pass
+arguments to the module's C<import> subroutine, by appending them to the
+class name. For example:
+
+ use Attribute::Handlers
+ autotie => { Dir => 'Tie::Dir qw(DIR_UNLINK)' };
+
+If the attribute name is unqualified, the attribute is installed in the
+current package. Otherwise it is installed in the qualifier's package:
+
+ package Here;
+
+ use Attribute::Handlers autotie => {
+ Other::Good => Tie::SecureHash, # tie attr installed in Other::
+ Bad => Tie::Taxes, # tie attr installed in Here::
+ UNIVERSAL::Ugly => Software::Patent # tie attr installed everywhere
+ };
+
+Autoties are most commonly used in the module to which they actually tie,
+and need to export their attributes to any module that calls them. To
+facilitiate this, Attribute::Handlers recognizes a special "pseudo-class" --
+C<__CALLER__>, which may be specified as the qualifier of an attribute:
+
+ package Tie::Me::Kangaroo:Down::Sport;
+
+ use Attribute::Handlers autotie => { __CALLER__::Roo => __PACKAGE__ };
+
+This causes Attribute::Handlers to define the C<Roo> attribute in the package
+that imports the Tie::Me::Kangaroo:Down::Sport module.
+
+=head3 Passing the tied object to C<tie>
+
+Occasionally it is important to pass a reference to the object being tied
+to the TIESCALAR, TIEHASH, etc. that ties it.
+
+The C<autotie> mechanism supports this too. The following code:
+
+ use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
+ my $var : Selfish(@args);
+
+has the same effect as:
+
+ tie my $var, 'Tie::Selfish', @args;
+
+But when C<"autotieref"> is used instead of C<"autotie">:
+
+ use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
+ my $var : Selfish(@args);
+
+the effect is to pass the C<tie> call an extra reference to the variable
+being tied:
+
+ tie my $var, 'Tie::Selfish', \$var, @args;
+
+
+
+=head1 EXAMPLES
+
+If the class shown in L<SYNOPSIS> were placed in the MyClass.pm
+module, then the following code:
+
+ package main;
+ use MyClass;
+
+ my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
+
+ package SomeOtherClass;
+ use base MyClass;
+
+ sub tent { 'acle' }
+
+ sub fn :Ugly(sister) :Omni('po',tent()) {...}
+ my @arr :Good :Omni(s/cie/nt/);
+ my %hsh :Good(q/bye) :Omni(q/bus/);
+
+
+would cause the following handlers to be invoked:
+
+ # my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
+
+ MyClass::Good:ATTR(SCALAR)( 'MyClass', # class
+ 'LEXICAL', # no typeglob
+ \$slr, # referent
+ 'Good', # attr name
+ undef # no attr data
+ 'CHECK', # compiler phase
+ );
+
+ MyClass::Bad:ATTR(SCALAR)( 'MyClass', # class
+ 'LEXICAL', # no typeglob
+ \$slr, # referent
+ 'Bad', # attr name
+ 0 # eval'd attr data
+ 'CHECK', # compiler phase
+ );
+
+ MyClass::Omni:ATTR(SCALAR)( 'MyClass', # class
+ 'LEXICAL', # no typeglob
+ \$slr, # referent
+ 'Omni', # attr name
+ '-vorous' # eval'd attr data
+ 'CHECK', # compiler phase
+ );
+
+
+ # sub fn :Ugly(sister) :Omni('po',tent()) {...}
+
+ MyClass::UGLY:ATTR(CODE)( 'SomeOtherClass', # class
+ \*SomeOtherClass::fn, # typeglob
+ \&SomeOtherClass::fn, # referent
+ 'Ugly', # attr name
+ 'sister' # eval'd attr data
+ 'CHECK', # compiler phase
+ );
+
+ MyClass::Omni:ATTR(CODE)( 'SomeOtherClass', # class
+ \*SomeOtherClass::fn, # typeglob
+ \&SomeOtherClass::fn, # referent
+ 'Omni', # attr name
+ ['po','acle'] # eval'd attr data
+ 'CHECK', # compiler phase
+ );
+
+
+ # my @arr :Good :Omni(s/cie/nt/);
+
+ MyClass::Good:ATTR(ARRAY)( 'SomeOtherClass', # class
+ 'LEXICAL', # no typeglob
+ \@arr, # referent
+ 'Good', # attr name
+ undef # no attr data
+ 'CHECK', # compiler phase
+ );
+
+ MyClass::Omni:ATTR(ARRAY)( 'SomeOtherClass', # class
+ 'LEXICAL', # no typeglob
+ \@arr, # referent
+ 'Omni', # attr name
+ "" # eval'd attr data
+ 'CHECK', # compiler phase
+ );
+
+
+ # my %hsh :Good(q/bye) :Omni(q/bus/);
+
+ MyClass::Good:ATTR(HASH)( 'SomeOtherClass', # class
+ 'LEXICAL', # no typeglob
+ \%hsh, # referent
+ 'Good', # attr name
+ 'q/bye' # raw attr data
+ 'CHECK', # compiler phase
+ );
+
+ MyClass::Omni:ATTR(HASH)( 'SomeOtherClass', # class
+ 'LEXICAL', # no typeglob
+ \%hsh, # referent
+ 'Omni', # attr name
+ 'bus' # eval'd attr data
+ 'CHECK', # compiler phase
+ );
+
+
+Installing handlers into UNIVERSAL, makes them...err..universal.
+For example:
+
+ package Descriptions;
+ use Attribute::Handlers;
+
+ my %name;
+ sub name { return $name{$_[2]}||*{$_[1]}{NAME} }
+
+ sub UNIVERSAL::Name :ATTR {
+ $name{$_[2]} = $_[4];
+ }
+
+ sub UNIVERSAL::Purpose :ATTR {
+ print STDERR "Purpose of ", &name, " is $_[4]\n";
+ }
+
+ sub UNIVERSAL::Unit :ATTR {
+ print STDERR &name, " measured in $_[4]\n";
+ }
+
+Let's you write:
+
+ use Descriptions;
+
+ my $capacity : Name(capacity)
+ : Purpose(to store max storage capacity for files)
+ : Unit(Gb);
+
+
+ package Other;
+
+ sub foo : Purpose(to foo all data before barring it) { }
+
+ # etc.
+
+
+=head1 DIAGNOSTICS
+
+=over
+
+=item C<Bad attribute type: ATTR(%s)>
+
+An attribute handler was specified with an C<:ATTR(I<ref_type>)>, but the
+type of referent it was defined to handle wasn't one of the five permitted:
+C<SCALAR>, C<ARRAY>, C<HASH>, C<CODE>, or C<ANY>.
+
+=item C<Attribute handler %s doesn't handle %s attributes>
+
+A handler for attributes of the specified name I<was> defined, but not
+for the specified type of declaration. Typically encountered whe trying
+to apply a C<VAR> attribute handler to a subroutine, or a C<SCALAR>
+attribute handler to some other type of variable.
+
+=item C<Declaration of %s attribute in package %s may clash with future reserved word>
+
+A handler for an attributes with an all-lowercase name was declared. An
+attribute with an all-lowercase name might have a meaning to Perl
+itself some day, even though most don't yet. Use a mixed-case attribute
+name, instead.
+
+=item C<Can't have two ATTR specifiers on one subroutine>
+
+You just can't, okay?
+Instead, put all the specifications together with commas between them
+in a single C<ATTR(I<specification>)>.
+
+=item C<Can't autotie a %s>
+
+You can only declare autoties for types C<"SCALAR">, C<"ARRAY">, and
+C<"HASH">. They're the only things (apart from typeglobs -- which are
+not declarable) that Perl can tie.
+
+=item C<Internal error: %s symbol went missing>
+
+Something is rotten in the state of the program. An attributed
+subroutine ceased to exist between the point it was declared and the point
+at which its attribute handler(s) would have been called.
+
+=back
+
+=head1 AUTHOR
+
+Damian Conway (damian@conway.org)
+
+=head1 BUGS
+
+There are undoubtedly serious bugs lurking somewhere in code this funky :-)
+Bug reports and other feedback are most welcome.
+
+=head1 COPYRIGHT
+
+ Copyright (c) 2001, Damian Conway. All Rights Reserved.
+ This module is free software. It may be used, redistributed
+ and/or modified under the same terms as Perl itself.
projects / p5sagit/p5-mst-13.2.git / commitdiff