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diff --git a/Master/tlpkg/tlperl/lib/Attribute/Handlers.pm b/Master/tlpkg/tlperl/lib/Attribute/Handlers.pm new file mode 100755 index 00000000000..ea11b8f7ed6 --- /dev/null +++ b/Master/tlpkg/tlperl/lib/Attribute/Handlers.pm @@ -0,0 +1,924 @@ +package Attribute::Handlers; +use 5.006; +use Carp; +use warnings; +use strict; +use vars qw($VERSION $AUTOLOAD); +$VERSION = '0.87'; # remember to update version in POD! +# $DB::single=1; + +my %symcache; +sub findsym { + my ($pkg, $ref, $type) = @_; + return $symcache{$pkg,$ref} if $symcache{$pkg,$ref}; + $type ||= ref($ref); + no strict 'refs'; + foreach my $sym ( values %{$pkg."::"} ) { + use strict; + next unless ref ( \$sym ) eq 'GLOB'; + 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 =~ $qual_id + && eval "use base q\0$tieclass\0; 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 $_"; + } + } +} + +# On older perls, code attribute handlers run before the sub gets placed +# in its package. Since the :ATTR handlers need to know the name of the +# sub they're applied to, the name lookup (via findsym) needs to be +# delayed: we do it immediately before we might need to find attribute +# handlers from their name. However, on newer perls (which fix some +# problems relating to attribute application), a sub gets placed in its +# package before its attributes are processed. In this case, the +# delayed name lookup might be too late, because the sub we're looking +# for might have already been replaced. So we need to detect which way +# round this perl does things, and time the name lookup accordingly. +BEGIN { + my $delayed; + sub Attribute::Handlers::_TEST_::MODIFY_CODE_ATTRIBUTES { + $delayed = \&Attribute::Handlers::_TEST_::t != $_[1]; + return (); + } + sub Attribute::Handlers::_TEST_::t :T { } + *_delayed_name_resolution = sub() { $delayed }; + undef &Attribute::Handlers::_TEST_::MODIFY_CODE_ATTRIBUTES; + undef &Attribute::Handlers::_TEST_::t; +} + +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{$lastattr{type}}} ) { + no strict 'refs'; + *{"$lastattr{pkg}::_ATTR_${_}_${name}"} = $lastattr{ref}; + } + %lastattr = (); +} + +sub AUTOLOAD { + return if $AUTOLOAD =~ /::DESTROY$/; + my ($class) = $AUTOLOAD =~ m/(.*)::/g; + $AUTOLOAD =~ m/_ATTR_(.*?)_(.*)/ or + croak "Can't locate class method '$AUTOLOAD' via package '$class'"; + croak "Attribute handler '$2' doesn't handle $1 attributes"; +} + +my $builtin = qr/lvalue|method|locked|unique|shared/; + +sub _gen_handler_AH_() { + return sub { + _resolve_lastattr if _delayed_name_resolution; + my ($pkg, $ref, @attrs) = @_; + my (undef, $filename, $linenum) = caller 2; + foreach (@attrs) { + my ($attr, $data) = /^([a-z_]\w*)(?:[(](.*)[)])?$/is or next; + if ($attr eq 'ATTR') { + no strict 'refs'; + $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); + _resolve_lastattr unless _delayed_name_resolution; + } + else { + my $type = ref $ref; + my $handler = $pkg->can("_ATTR_${type}_${attr}"); + next unless $handler; + my $decl = [$pkg, $ref, $attr, $data, + $raw{$handler}, $phase{$handler}, $filename, $linenum]; + foreach my $gphase (@global_phases) { + _apply_handler_AH_($decl,$gphase) + if $global_phases{$gphase} <= $global_phase; + } + if ($global_phase != 0) { + # if _gen_handler_AH_ is being called after + # CHECK it's for a lexical, so make sure + # it didn't want to run anything later + + local $Carp::CarpLevel = 2; + carp "Won't be able to apply END handler" + if $phase{$handler}{END}; + } + else { + push @declarations, $decl + } + } + $_ = undef; + } + return grep {defined && !/$builtin/} @attrs; + } +} + +{ + no strict 'refs'; + *{"Attribute::Handlers::UNIVERSAL::MODIFY_${_}_ATTRIBUTES"} = + _gen_handler_AH_ foreach @{$validtype{ANY}}; +} +push @UNIVERSAL::ISA, 'Attribute::Handlers::UNIVERSAL' + unless grep /^Attribute::Handlers::UNIVERSAL$/, @UNIVERSAL::ISA; + +sub _apply_handler_AH_ { + my ($declaration, $phase) = @_; + my ($pkg, $ref, $attr, $data, $raw, $handlerphase, $filename, $linenum) = @$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 ||= $type eq 'CODE' ? 'ANON' : 'LEXICAL'; + no warnings; + if (!$raw && defined($data)) { + if ($data ne '') { + my $evaled = eval("package $pkg; no warnings; no strict; + local \$SIG{__WARN__}=sub{die}; [$data]"); + $data = $evaled unless $@; + } + else { $data = undef } + } + $pkg->$handler($sym, + (ref $sym eq 'GLOB' ? *{$sym}{ref $ref}||$ref : $ref), + $attr, + $data, + $phase, + $filename, + $linenum, + ); + return 1; +} + +{ + no warnings 'void'; + CHECK { + $global_phase++; + _resolve_lastattr if _delayed_name_resolution; + _apply_handler_AH_($_,'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 0.87 of Attribute::Handlers, +released September 21, 2009. + +=head1 SYNOPSIS + + package MyClass; + require 5.006; + 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 $next : Cycle(['A'..'Z']); + + +=head1 DESCRIPTION + +This module, when inherited by a package, allows that package's class to +define attribute handler subroutines for specific attributes. Variables +and subroutines subsequently defined in that package, or in packages +derived from that package may be given attributes with the same names as +the attribute handler subroutines, which will then be called in one of +the compilation phases (i.e. in a C<BEGIN>, C<CHECK>, C<INIT>, or C<END> +block). (C<UNITCHECK> blocks don't correspond to a global compilation +phase, so they can't be specified here.) + +To create a handler, define it as a subroutine with the same name as +the desired attribute, and declare the subroutine itself with the +attribute C<:ATTR>. For example: + + package LoudDecl; + use Attribute::Handlers; + + sub Loud :ATTR { + my ($package, $symbol, $referent, $attr, $data, $phase, $filename, $linenum) = @_; + print STDERR + ref($referent), " ", + *{$symbol}{NAME}, " ", + "($referent) ", "was just declared ", + "and ascribed the ${attr} attribute ", + "with data ($data)\n", + "in phase $phase\n", + "in file $filename at line $linenum\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; + +=item [6] + +the filename in which the handler is being invoked; + +=item [7] + +the line number in this file. + +=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<$_[1]>) is set to the +string C<'LEXICAL'> in that case. Likewise, ascribing an attribute to +an anonymous subroutine results in a symbol table argument of C<'ANON'>. + +The data argument passes in the value (if any) associated with the +attribute. For example, if C<&foo> had been declared: + + sub foo :Loud("turn it up to 11, man!") {...} + +then a reference to an array containing the string +C<"turn it up to 11, man!"> would be passed as the last argument. + +Attribute::Handlers makes strenuous efforts to convert +the data argument (C<$_[4]>) to a useable form before passing it to +the handler (but see L<"Non-interpretive attribute handlers">). +If those efforts succeed, the interpreted data is passed in an array +reference; if they fail, the raw data is passed as a string. +For example, all of these: + + 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. While: + + sub foo :Loud(['till','ears','are','bleeding']) {...} + +causes it to pass C<[ ['till','ears','are','bleeding'] ]>; the array +reference specified in the data being passed inside the standard +array reference indicating successful interpretation. + +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 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 +facilitate 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. + +Note that it is important to quote the __CALLER__::Roo identifier because +a bug in perl 5.8 will refuse to parse it and cause an unknown error. + +=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 UTILITY FUNCTIONS + +This module offers a single utility function, C<findsym()>. + +=over 4 + +=item findsym + + my $symbol = Attribute::Handlers::findsym($package, $referent); + +The function looks in the symbol table of C<$package> for the typeglob for +C<$referent>, which is a reference to a variable or subroutine (SCALAR, ARRAY, +HASH, or CODE). If it finds the typeglob, it returns it. Otherwise, it returns +undef. Note that C<findsym> memoizes the typeglobs it has previously +successfully found, so subsequent calls with the same arguments should be +must faster. + +=back + +=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. + +=item C<Won't be able to apply END handler> + +You have defined an END handler for an attribute that is being applied +to a lexical variable. Since the variable may not be available during END +this won't happen. + +=back + +=head1 AUTHOR + +Damian Conway (damian@conway.org). The maintainer of this module is now Rafael +Garcia-Suarez (rgarciasuarez@gmail.com). + +Maintainer of the CPAN release is Steffen Mueller (smueller@cpan.org). +Contact him with technical difficulties with respect to the packaging of the +CPAN module. + +=head1 BUGS + +There are undoubtedly serious bugs lurking somewhere in code this funky :-) +Bug reports and other feedback are most welcome. + +=head1 COPYRIGHT AND LICENSE + + Copyright (c) 2001-2009, 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. |