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Diffstat (limited to 'Master/tlpkg/tlperl0/lib/Tie/Hash.pm')
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1 files changed, 257 insertions, 0 deletions
diff --git a/Master/tlpkg/tlperl0/lib/Tie/Hash.pm b/Master/tlpkg/tlperl0/lib/Tie/Hash.pm new file mode 100755 index 00000000000..1ca8887e7e3 --- /dev/null +++ b/Master/tlpkg/tlperl0/lib/Tie/Hash.pm @@ -0,0 +1,257 @@ +package Tie::Hash; + +our $VERSION = '1.03'; + +=head1 NAME + +Tie::Hash, Tie::StdHash, Tie::ExtraHash - base class definitions for tied hashes + +=head1 SYNOPSIS + + package NewHash; + require Tie::Hash; + + @ISA = qw(Tie::Hash); + + sub DELETE { ... } # Provides needed method + sub CLEAR { ... } # Overrides inherited method + + + package NewStdHash; + require Tie::Hash; + + @ISA = qw(Tie::StdHash); + + # All methods provided by default, define only those needing overrides + # Accessors access the storage in %{$_[0]}; + # TIEHASH should return a reference to the actual storage + sub DELETE { ... } + + package NewExtraHash; + require Tie::Hash; + + @ISA = qw(Tie::ExtraHash); + + # All methods provided by default, define only those needing overrides + # Accessors access the storage in %{$_[0][0]}; + # TIEHASH should return an array reference with the first element being + # the reference to the actual storage + sub DELETE { + $_[0][1]->('del', $_[0][0], $_[1]); # Call the report writer + delete $_[0][0]->{$_[1]}; # $_[0]->SUPER::DELETE($_[1]) + } + + + package main; + + tie %new_hash, 'NewHash'; + tie %new_std_hash, 'NewStdHash'; + tie %new_extra_hash, 'NewExtraHash', + sub {warn "Doing \U$_[1]\E of $_[2].\n"}; + +=head1 DESCRIPTION + +This module provides some skeletal methods for hash-tying classes. See +L<perltie> for a list of the functions required in order to tie a hash +to a package. The basic B<Tie::Hash> package provides a C<new> method, as well +as methods C<TIEHASH>, C<EXISTS> and C<CLEAR>. The B<Tie::StdHash> and +B<Tie::ExtraHash> packages +provide most methods for hashes described in L<perltie> (the exceptions +are C<UNTIE> and C<DESTROY>). They cause tied hashes to behave exactly like standard hashes, +and allow for selective overwriting of methods. B<Tie::Hash> grandfathers the +C<new> method: it is used if C<TIEHASH> is not defined +in the case a class forgets to include a C<TIEHASH> method. + +For developers wishing to write their own tied hashes, the required methods +are briefly defined below. See the L<perltie> section for more detailed +descriptive, as well as example code: + +=over 4 + +=item TIEHASH classname, LIST + +The method invoked by the command C<tie %hash, classname>. Associates a new +hash instance with the specified class. C<LIST> would represent additional +arguments (along the lines of L<AnyDBM_File> and compatriots) needed to +complete the association. + +=item STORE this, key, value + +Store datum I<value> into I<key> for the tied hash I<this>. + +=item FETCH this, key + +Retrieve the datum in I<key> for the tied hash I<this>. + +=item FIRSTKEY this + +Return the first key in the hash. + +=item NEXTKEY this, lastkey + +Return the next key in the hash. + +=item EXISTS this, key + +Verify that I<key> exists with the tied hash I<this>. + +The B<Tie::Hash> implementation is a stub that simply croaks. + +=item DELETE this, key + +Delete the key I<key> from the tied hash I<this>. + +=item CLEAR this + +Clear all values from the tied hash I<this>. + +=item SCALAR this + +Returns what evaluating the hash in scalar context yields. + +B<Tie::Hash> does not implement this method (but B<Tie::StdHash> +and B<Tie::ExtraHash> do). + +=back + +=head1 Inheriting from B<Tie::StdHash> + +The accessor methods assume that the actual storage for the data in the tied +hash is in the hash referenced by C<tied(%tiedhash)>. Thus overwritten +C<TIEHASH> method should return a hash reference, and the remaining methods +should operate on the hash referenced by the first argument: + + package ReportHash; + our @ISA = 'Tie::StdHash'; + + sub TIEHASH { + my $storage = bless {}, shift; + warn "New ReportHash created, stored in $storage.\n"; + $storage + } + sub STORE { + warn "Storing data with key $_[1] at $_[0].\n"; + $_[0]{$_[1]} = $_[2] + } + + +=head1 Inheriting from B<Tie::ExtraHash> + +The accessor methods assume that the actual storage for the data in the tied +hash is in the hash referenced by C<(tied(%tiedhash))-E<gt>[0]>. Thus overwritten +C<TIEHASH> method should return an array reference with the first +element being a hash reference, and the remaining methods should operate on the +hash C<< %{ $_[0]->[0] } >>: + + package ReportHash; + our @ISA = 'Tie::ExtraHash'; + + sub TIEHASH { + my $class = shift; + my $storage = bless [{}, @_], $class; + warn "New ReportHash created, stored in $storage.\n"; + $storage; + } + sub STORE { + warn "Storing data with key $_[1] at $_[0].\n"; + $_[0][0]{$_[1]} = $_[2] + } + +The default C<TIEHASH> method stores "extra" arguments to tie() starting +from offset 1 in the array referenced by C<tied(%tiedhash)>; this is the +same storage algorithm as in TIEHASH subroutine above. Hence, a typical +package inheriting from B<Tie::ExtraHash> does not need to overwrite this +method. + +=head1 C<SCALAR>, C<UNTIE> and C<DESTROY> + +The methods C<UNTIE> and C<DESTROY> are not defined in B<Tie::Hash>, +B<Tie::StdHash>, or B<Tie::ExtraHash>. Tied hashes do not require +presence of these methods, but if defined, the methods will be called in +proper time, see L<perltie>. + +C<SCALAR> is only defined in B<Tie::StdHash> and B<Tie::ExtraHash>. + +If needed, these methods should be defined by the package inheriting from +B<Tie::Hash>, B<Tie::StdHash>, or B<Tie::ExtraHash>. See L<perltie/"SCALAR"> +to find out what happens when C<SCALAR> does not exist. + +=head1 MORE INFORMATION + +The packages relating to various DBM-related implementations (F<DB_File>, +F<NDBM_File>, etc.) show examples of general tied hashes, as does the +L<Config> module. While these do not utilize B<Tie::Hash>, they serve as +good working examples. + +=cut + +use Carp; +use warnings::register; + +sub new { + my $pkg = shift; + $pkg->TIEHASH(@_); +} + +# Grandfather "new" + +sub TIEHASH { + my $pkg = shift; + if (defined &{"${pkg}::new"}) { + warnings::warnif("WARNING: calling ${pkg}->new since ${pkg}->TIEHASH is missing"); + $pkg->new(@_); + } + else { + croak "$pkg doesn't define a TIEHASH method"; + } +} + +sub EXISTS { + my $pkg = ref $_[0]; + croak "$pkg doesn't define an EXISTS method"; +} + +sub CLEAR { + my $self = shift; + my $key = $self->FIRSTKEY(@_); + my @keys; + + while (defined $key) { + push @keys, $key; + $key = $self->NEXTKEY(@_, $key); + } + foreach $key (@keys) { + $self->DELETE(@_, $key); + } +} + +# The Tie::StdHash package implements standard perl hash behaviour. +# It exists to act as a base class for classes which only wish to +# alter some parts of their behaviour. + +package Tie::StdHash; +# @ISA = qw(Tie::Hash); # would inherit new() only + +sub TIEHASH { bless {}, $_[0] } +sub STORE { $_[0]->{$_[1]} = $_[2] } +sub FETCH { $_[0]->{$_[1]} } +sub FIRSTKEY { my $a = scalar keys %{$_[0]}; each %{$_[0]} } +sub NEXTKEY { each %{$_[0]} } +sub EXISTS { exists $_[0]->{$_[1]} } +sub DELETE { delete $_[0]->{$_[1]} } +sub CLEAR { %{$_[0]} = () } +sub SCALAR { scalar %{$_[0]} } + +package Tie::ExtraHash; + +sub TIEHASH { my $p = shift; bless [{}, @_], $p } +sub STORE { $_[0][0]{$_[1]} = $_[2] } +sub FETCH { $_[0][0]{$_[1]} } +sub FIRSTKEY { my $a = scalar keys %{$_[0][0]}; each %{$_[0][0]} } +sub NEXTKEY { each %{$_[0][0]} } +sub EXISTS { exists $_[0][0]->{$_[1]} } +sub DELETE { delete $_[0][0]->{$_[1]} } +sub CLEAR { %{$_[0][0]} = () } +sub SCALAR { scalar %{$_[0][0]} } + +1; |