X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2Ffields.pm;h=cca778f905d971f26afccd20400db45af4c74c10;hb=a6f787ca70fe8281557cb1a6f45d147f91cb88bb;hp=be2a7aedab42c02fe4adeeaed087c85cff31b564;hpb=3b825e419da1c361eab06a1e6d287276c0aef241;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/fields.pm b/lib/fields.pm index be2a7ae..cca778f 100644 --- a/lib/fields.pm +++ b/lib/fields.pm @@ -1,5 +1,173 @@ package fields; +require 5.005; +use strict; +no strict 'refs'; +unless( eval q{require warnings::register; warnings::register->import} ) { + *warnings::warnif = sub { + require Carp; + Carp::carp(@_); + } +} +use vars qw(%attr $VERSION); + +$VERSION = '2.03'; + +# constant.pm is slow +sub PUBLIC () { 2**0 } +sub PRIVATE () { 2**1 } +sub INHERITED () { 2**2 } +sub PROTECTED () { 2**3 } + + +# The %attr hash holds the attributes of the currently assigned fields +# per class. The hash is indexed by class names and the hash value is +# an array reference. The first element in the array is the lowest field +# number not belonging to a base class. The remaining elements' indices +# are the field numbers. The values are integer bit masks, or undef +# in the case of base class private fields (which occupy a slot but are +# otherwise irrelevant to the class). + +sub import { + my $class = shift; + return unless @_; + my $package = caller(0); + # avoid possible typo warnings + %{"$package\::FIELDS"} = () unless %{"$package\::FIELDS"}; + my $fields = \%{"$package\::FIELDS"}; + my $fattr = ($attr{$package} ||= [1]); + my $next = @$fattr; + + # Quiet pseudo-hash deprecation warning for uses of fields::new. + bless \%{"$package\::FIELDS"}, 'pseudohash'; + + if ($next > $fattr->[0] + and ($fields->{$_[0]} || 0) >= $fattr->[0]) + { + # There are already fields not belonging to base classes. + # Looks like a possible module reload... + $next = $fattr->[0]; + } + foreach my $f (@_) { + my $fno = $fields->{$f}; + + # Allow the module to be reloaded so long as field positions + # have not changed. + if ($fno and $fno != $next) { + require Carp; + if ($fno < $fattr->[0]) { + if ($] < 5.006001) { + warn("Hides field '$f' in base class") if $^W; + } else { + warnings::warnif("Hides field '$f' in base class") ; + } + } else { + Carp::croak("Field name '$f' already in use"); + } + } + $fields->{$f} = $next; + $fattr->[$next] = ($f =~ /^_/) ? PRIVATE : PUBLIC; + $next += 1; + } + if (@$fattr > $next) { + # Well, we gave them the benefit of the doubt by guessing the + # module was reloaded, but they appear to be declaring fields + # in more than one place. We can't be sure (without some extra + # bookkeeping) that the rest of the fields will be declared or + # have the same positions, so punt. + require Carp; + Carp::croak ("Reloaded module must declare all fields at once"); + } +} + +sub inherit { + require base; + goto &base::inherit_fields; +} + +sub _dump # sometimes useful for debugging +{ + for my $pkg (sort keys %attr) { + print "\n$pkg"; + if (@{"$pkg\::ISA"}) { + print " (", join(", ", @{"$pkg\::ISA"}), ")"; + } + print "\n"; + my $fields = \%{"$pkg\::FIELDS"}; + for my $f (sort {$fields->{$a} <=> $fields->{$b}} keys %$fields) { + my $no = $fields->{$f}; + print " $no: $f"; + my $fattr = $attr{$pkg}[$no]; + if (defined $fattr) { + my @a; + push(@a, "public") if $fattr & PUBLIC; + push(@a, "private") if $fattr & PRIVATE; + push(@a, "inherited") if $fattr & INHERITED; + print "\t(", join(", ", @a), ")"; + } + print "\n"; + } + } +} + +if ($] < 5.009) { + *new = sub { + my $class = shift; + $class = ref $class if ref $class; + return bless [\%{$class . "::FIELDS"}], $class; + } +} else { + *new = sub { + my $class = shift; + $class = ref $class if ref $class; + require Hash::Util; + my $self = bless {}, $class; + + # The lock_keys() prototype won't work since we require Hash::Util :( + &Hash::Util::lock_keys(\%$self, keys %{$class.'::FIELDS'}); + return $self; + } +} + +sub phash { + die "Pseudo-hashes have been removed from Perl" if $] >= 5.009; + my $h; + my $v; + if (@_) { + if (ref $_[0] eq 'ARRAY') { + my $a = shift; + @$h{@$a} = 1 .. @$a; + if (@_) { + $v = shift; + unless (! @_ and ref $v eq 'ARRAY') { + require Carp; + Carp::croak ("Expected at most two array refs\n"); + } + } + } + else { + if (@_ % 2) { + require Carp; + Carp::croak ("Odd number of elements initializing pseudo-hash\n"); + } + my $i = 0; + @$h{grep ++$i % 2, @_} = 1 .. @_ / 2; + $i = 0; + $v = [grep $i++ % 2, @_]; + } + } + else { + $h = {}; + $v = []; + } + [ $h, @$v ]; + +} + +1; + +__END__ + =head1 NAME fields - compile-time class fields @@ -21,10 +189,10 @@ fields - compile-time class fields } } - my Foo $var = Foo::->new; + my $var = Foo->new; $var->{foo} = 42; - # this will generate a compile-time error + # this will generate an error $var->{zap} = 42; # subclassing @@ -51,10 +219,13 @@ hash of the calling package, but this may change in future versions. Do B update the %FIELDS hash directly, because it must be created at compile-time for it to be fully useful, as is done by this pragma. +B + If a typed lexical variable holding a reference is used to access a -hash element and a package with the same name as the type has declared -class fields using this pragma, then the operation is turned into an -array access at compile time. +hash element and a package with the same name as the type has +declared class fields using this pragma, then the operation is +turned into an array access at compile time. + The related C pragma will combine fields from base classes and any fields declared using the C pragma. This enables field @@ -65,26 +236,39 @@ the class and are not visible to subclasses. Inherited fields can be overridden but will generate a warning if used together with the C<-w> switch. -The effect of all this is that you can have objects with named fields -which are as compact and as fast arrays to access. This only works -as long as the objects are accessed through properly typed variables. -If the objects are not typed, access is only checked at run time. +B + +The effect of all this is that you can have objects with named +fields which are as compact and as fast arrays to access. This only +works as long as the objects are accessed through properly typed +variables. If the objects are not typed, access is only checked at +run time. + The following functions are supported: -=over 8 +=over 4 =item new -fields::new() creates and blesses a pseudo-hash comprised of the fields -declared using the C pragma into the specified class. +B< perl before 5.9.0: > fields::new() creates and blesses a +pseudo-hash comprised of the fields declared using the C +pragma into the specified class. + +B< perl 5.9.0 and higher: > fields::new() creates and blesses a +restricted-hash comprised of the fields declared using the C +pragma into the specified class. + +This function is usable with or without pseudo-hashes. It is the +recommended way to construct a fields-based object. + This makes it possible to write a constructor like this: package Critter::Sounds; use fields qw(cat dog bird); sub new { - my Critter::Sounds $self = shift; + my $self = shift; $self = fields::new($self) unless ref $self; $self->{cat} = 'meow'; # scalar element @$self{'dog','bird'} = ('bark','tweet'); # slice @@ -93,6 +277,8 @@ This makes it possible to write a constructor like this: =item phash +B< before perl 5.9.0: > + fields::phash() can be used to create and initialize a plain (unblessed) pseudo-hash. This function should always be used instead of creating pseudo-hashes directly. @@ -106,180 +292,28 @@ This makes it particularly useful for creating a pseudo-hash from subroutine arguments: sub dogtag { - my $tag = fields::phash([qw(name rank ser_num)], [@_]); + my $tag = fields::phash([qw(name rank ser_num)], [@_]); } fields::phash() also accepts a list of key-value pairs that will be used to construct the pseudo hash. Examples: my $tag = fields::phash(name => "Joe", - rank => "captain", - ser_num => 42); + rank => "captain", + ser_num => 42); my $pseudohash = fields::phash(%args); +B< perl 5.9.0 and higher: > + +Pseudo-hashes have been removed from Perl as of 5.10. Consider using +restricted hashes or fields::new() instead. Using fields::phash() +will cause an error. + =back =head1 SEE ALSO -L, -L +L =cut - -use 5.006_001; -use strict; -no strict 'refs'; -use warnings::register; -our(%attr, $VERSION); - -$VERSION = "1.02"; - -# some constants -sub _PUBLIC () { 1 } -sub _PRIVATE () { 2 } - -# The %attr hash holds the attributes of the currently assigned fields -# per class. The hash is indexed by class names and the hash value is -# an array reference. The first element in the array is the lowest field -# number not belonging to a base class. The remaining elements' indices -# are the field numbers. The values are integer bit masks, or undef -# in the case of base class private fields (which occupy a slot but are -# otherwise irrelevant to the class). - -sub import { - my $class = shift; - return unless @_; - my $package = caller(0); - # avoid possible typo warnings - %{"$package\::FIELDS"} = () unless %{"$package\::FIELDS"}; - my $fields = \%{"$package\::FIELDS"}; - my $fattr = ($attr{$package} ||= [1]); - my $next = @$fattr; - - if ($next > $fattr->[0] - and ($fields->{$_[0]} || 0) >= $fattr->[0]) - { - # There are already fields not belonging to base classes. - # Looks like a possible module reload... - $next = $fattr->[0]; - } - foreach my $f (@_) { - my $fno = $fields->{$f}; - - # Allow the module to be reloaded so long as field positions - # have not changed. - if ($fno and $fno != $next) { - require Carp; - if ($fno < $fattr->[0]) { - warnings::warnif("Hides field '$f' in base class") ; - } else { - Carp::croak("Field name '$f' already in use"); - } - } - $fields->{$f} = $next; - $fattr->[$next] = ($f =~ /^_/) ? _PRIVATE : _PUBLIC; - $next += 1; - } - if (@$fattr > $next) { - # Well, we gave them the benefit of the doubt by guessing the - # module was reloaded, but they appear to be declaring fields - # in more than one place. We can't be sure (without some extra - # bookkeeping) that the rest of the fields will be declared or - # have the same positions, so punt. - require Carp; - Carp::croak ("Reloaded module must declare all fields at once"); - } -} - -sub inherit { # called by base.pm when $base_fields is nonempty - my($derived, $base) = @_; - my $base_attr = $attr{$base}; - my $derived_attr = $attr{$derived} ||= []; - # avoid possible typo warnings - %{"$base\::FIELDS"} = () unless %{"$base\::FIELDS"}; - %{"$derived\::FIELDS"} = () unless %{"$derived\::FIELDS"}; - my $base_fields = \%{"$base\::FIELDS"}; - my $derived_fields = \%{"$derived\::FIELDS"}; - - $derived_attr->[0] = $base_attr ? scalar(@$base_attr) : 1; - while (my($k,$v) = each %$base_fields) { - my($fno); - if ($fno = $derived_fields->{$k} and $fno != $v) { - require Carp; - Carp::croak ("Inherited %FIELDS can't override existing %FIELDS"); - } - if ($base_attr->[$v] & _PRIVATE) { - $derived_attr->[$v] = undef; - } else { - $derived_attr->[$v] = $base_attr->[$v]; - $derived_fields->{$k} = $v; - } - } -} - -sub _dump # sometimes useful for debugging -{ - for my $pkg (sort keys %attr) { - print "\n$pkg"; - if (@{"$pkg\::ISA"}) { - print " (", join(", ", @{"$pkg\::ISA"}), ")"; - } - print "\n"; - my $fields = \%{"$pkg\::FIELDS"}; - for my $f (sort {$fields->{$a} <=> $fields->{$b}} keys %$fields) { - my $no = $fields->{$f}; - print " $no: $f"; - my $fattr = $attr{$pkg}[$no]; - if (defined $fattr) { - my @a; - push(@a, "public") if $fattr & _PUBLIC; - push(@a, "private") if $fattr & _PRIVATE; - push(@a, "inherited") if $no < $attr{$pkg}[0]; - print "\t(", join(", ", @a), ")"; - } - print "\n"; - } - } -} - -sub new { - my $class = shift; - $class = ref $class if ref $class; - return bless [\%{$class . "::FIELDS"}], $class; -} - -sub phash { - my $h; - my $v; - if (@_) { - if (ref $_[0] eq 'ARRAY') { - my $a = shift; - @$h{@$a} = 1 .. @$a; - if (@_) { - $v = shift; - unless (! @_ and ref $v eq 'ARRAY') { - require Carp; - Carp::croak ("Expected at most two array refs\n"); - } - } - } - else { - if (@_ % 2) { - require Carp; - Carp::croak ("Odd number of elements initializing pseudo-hash\n"); - } - my $i = 0; - @$h{grep ++$i % 2, @_} = 1 .. @_ / 2; - $i = 0; - $v = [grep $i++ % 2, @_]; - } - } - else { - $h = {}; - $v = []; - } - [ $h, @$v ]; -} - -1;