-package TieHash;
+package Tie::Hash;
=head1 NAME
-TieHash, TieHash::Std - base class definitions for tied hashes
+Tie::Hash, Tie::StdHash - base class definitions for tied hashes
=head1 SYNOPSIS
package NewHash;
- require TieHash;
+ require Tie::Hash;
- @ISA = (TieHash);
+ @ISA = (Tie::Hash);
sub DELETE { ... } # Provides needed method
sub CLEAR { ... } # Overrides inherited method
package NewStdHash;
- require TieHash;
+ require Tie::Hash;
- @ISA = (TieHash::Std);
+ @ISA = (Tie::StdHash);
# All methods provided by default, define only those needing overrides
sub DELETE { ... }
=head1 DESCRIPTION
This module provides some skeletal methods for hash-tying classes. See
-L<perlfunc/tie> for a list of the functions required in order to tie a hash
-to a package. The basic B<TieHash> package provides a C<new> method, as well
-as methods C<TIEHASH>, C<EXISTS> and C<CLEAR>. The B<TieHash::Std> package
-provides most methods required for hashes in L<perlfunc/tie>. It inherits from
-B<TieHash>, and causes tied hashes to behave exactly like standard hashes,
-allowing for selective overloading of methods. The B<new> method is provided
-as grandfathering in the case a class forgets to include a B<TIEHASH> method.
+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> package
+provides most methods required for hashes in L<perltie>. It inherits from
+B<Tie::Hash>, and causes tied hashes to behave exactly like standard hashes,
+allowing for selective overloading of methods. The C<new> method is provided
+as grandfathering 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:
+are briefly defined below. See the L<perltie> section for more detailed
+descriptive, as well as example code:
+
+=over
=item TIEHASH classname, LIST
-The method invoked by the command C<tie %hash, class>. Associates a new
+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.
=head1 CAVEATS
-The L<perlfunc/tie> documentation includes a method called C<DESTROY> as
-a necessary method for tied hashes. Neither B<TieHash> nor B<TieHash::Std>
-define a default for this method.
-
-The C<CLEAR> method provided by these two packages is not listed in the
-L<perlfunc/tie> section.
+The L<perltie> documentation includes a method called C<DESTROY> as
+a necessary method for tied hashes. Neither B<Tie::Hash> nor B<Tie::StdHash>
+define a default for this method. This is a standard for class packages,
+but may be omitted in favor of a simple default.
=head1 MORE INFORMATION
The packages relating to various DBM-related implemetations (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<TieHash>, they serve as
+L<Config> module. While these do not utilize B<Tie::Hash>, they serve as
good working examples.
=cut
}
}
-# The TieHash::Std package implements standard perl hash behaviour.
+# 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 TieHash::Std;
-@ISA = qw(TieHash);
+package Tie::StdHash;
+@ISA = qw(Tie::Hash);
sub TIEHASH { bless {}, $_[0] }
sub STORE { $_[0]->{$_[1]} = $_[2] }
--- /dev/null
+package Tie::Scalar;
+
+=head1 NAME
+
+Tie::Scalar, Tie::StdScalar - base class definitions for tied scalars
+
+=head1 SYNOPSIS
+
+ package NewScalar;
+ require Tie::Scalar;
+
+ @ISA = (Tie::Scalar);
+
+ sub FETCH { ... } # Provide a needed method
+ sub TIESCALAR { ... } # Overrides inherited method
+
+
+ package NewStdScalar;
+ require Tie::Scalar;
+
+ @ISA = (Tie::StdScalar);
+
+ # All methods provided by default, so define only what needs be overridden
+ sub FETCH { ... }
+
+
+ package main;
+
+ tie $new_scalar, NewScalar;
+ tie $new_std_scalar, NewStdScalar;
+
+=head1 DESCRIPTION
+
+This module provides some skeletal methods for scalar-tying classes. See
+L<perltie> for a list of the functions required in tying a scalar to a
+package. The basic B<Tie::Scalar> package provides a C<new> method, as well
+as methods C<TIESCALAR>, C<FETCH> and C<STORE>. The B<Tie::StdScalar>
+package provides all the methods specified in L<perltie>. It inherits from
+B<Tie::Scalar> and causes scalars tied to it to behave exactly like the
+built-in scalars, allowing for selective overloading of methods. The C<new>
+method is provided as a means of grandfathering, for classes that forget to
+provide their own C<TIESCALAR> method.
+
+For developers wishing to write their own tied-scalar classes, the methods
+are summarized below. The L<perltie> section not only documents these, but
+has sample code as well:
+
+=over
+
+=item TIESCALAR classname, LIST
+
+The method invoked by the command C<tie $scalar, classname>. Associates a new
+scalar 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 FETCH this
+
+Retrieve the value of the tied scalar referenced by I<this>.
+
+=item STORE this, value
+
+Store data I<value> in the tied scalar referenced by I<this>.
+
+=item DESTROY this
+
+Free the storage associated with the tied scalar referenced by I<this>.
+This is rarely needed, as Perl manages its memory quite well. But the
+option exists, should a class wish to perform specific actions upon the
+destruction of an instance.
+
+=back
+
+=head1 MORE INFORMATION
+
+The L<perltie> section uses a good example of tying scalars by associating
+process IDs with priority.
+
+=cut
+
+use Carp;
+
+sub new {
+ my $pkg = shift;
+ $pkg->TIESCALAR(@_);
+}
+
+# "Grandfather" the new, a la Tie::Hash
+
+sub TIESCALAR {
+ my $pkg = shift;
+ if (defined &{"{$pkg}::new"}) {
+ carp "WARNING: calling ${pkg}->new since ${pkg}->TIESCALAR is missing"
+ if $^W;
+ $pkg->new(@_);
+ }
+ else {
+ croak "$pkg doesn't define a TIESCALAR method";
+ }
+}
+
+sub FETCH {
+ my $pkg = ref $_[0];
+ croak "$pkg doesn't define a FETCH method";
+}
+
+sub STORE {
+ my $pkg = ref $_[0];
+ croak "$pkg doesn't define a STORE method";
+}
+
+#
+# The Tie::StdScalar package provides scalars that behave exactly like
+# Perl's built-in scalars. Good base to inherit from, if you're only going to
+# tweak a small bit.
+#
+package Tie::StdScalar;
+@ISA = (Tie::Scalar);
+
+sub TIESCALAR {
+ my $class = shift;
+ my $instance = shift || undef;
+ return bless \$instance => $class;
+}
+
+sub FETCH {
+ return ${$_[0]};
+}
+
+sub STORE {
+ ${$_[0]} = $_[1];
+}
+
+sub DESTROY {
+ undef ${$_[0]};
+}
+
+1;
-package SubstrHash;
+package Tie::SubstrHash;
+
+=head1 NAME
+
+Tie::SubstrHash - Fixed-table-size, fixed-key-length hashing
+
+=head1 SYNOPSIS
+
+ require Tie::SubstrHash;
+
+ tie %myhash, Tie::SubstrHash, $key_len, $value_len, $table_size;
+
+=head1 DESCRIPTION
+
+The B<Tie::SubstrHash> package provides a hash-table-like interface to
+an array of determinate size, with constant key size and record size.
+
+Upon tying a new hash to this package, the developer must specify the
+size of the keys that will be used, the size of the value fields that the
+keys will index, and the size of the overall table (in terms of key-value
+pairs, not size in hard memory). I<These values will not change for the
+duration of the tied hash>. The newly-allocated hash table may now have
+data stored and retrieved. Efforts to store more than C<$table_size>
+elements will result in a fatal error, as will efforts to store a value
+not exactly C<$value_len> characters in length, or reference through a
+key not exactly C<$key_len> characters in length. While these constraints
+may seem excessive, the result is a hash table using much less internal
+memory than an equivalent freely-allocated hash table.
+
+=head1 CAVEATS
+
+Because the current implementation uses the table and key sizes for the
+hashing algorithm, there is no means by which to dynamically change the
+value of any of the initialization parameters.
+
+=cut
+
use Carp;
sub TIEHASH {
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