Documentation patch: Tie::Hash, Tie::Scalar, Tie::SubstrHash

[This finishes a job started by Randy Ray with perl5.002b1f.]

This patch updates the files lib/TieHash.pm and lib/SubstrHash.pm. Those
two files are moved to a new directory called lib/Tie. A new tie-related
class for scalars, lib/Tie/Scalar.pm, is added. Each of these has pod
documentation that passes through pod2man without complaint. All package
names are updated to reflect this structure, and the "standard" sub-classes
for hashes and scalars are named Tie::StdHash and Tie::StdScalar, in
keeping with the group consensus.

With this, the documentation for Tie::Hash should be fine, Tie::Scalar
exists and is documented, and Tie::SubstrHash (formerly just SubstrHash)
is also documented, albeit weakly. I have no examples of usage to show, and
I suspect a possible bug or two, but without examples it's hard to say.

As it happens, this patch also impacts the DBM-style extensions, as they
(DB_File, NDBM_File, GBM_File, ODBM_File, SDBM_File) all inherited from
the old TieHash.pm as a base class.

3 files changed, 201 insertions, 26 deletions

diff --git a/lib/Tie/Hash.pm b/lib/Tie/Hash.pm
index 161771a0ea..9a9d059a7f 100644
--- a/lib/Tie/Hash.pm
+++ b/lib/Tie/Hash.pm
@@ -1,24 +1,24 @@
-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 { ... }
@@ -32,20 +32,23 @@ TieHash, TieHash::Std - base class definitions for tied hashes
 =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.
@@ -82,18 +85,16 @@ Clear all values from the tied hash I<this>.
 
 =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
@@ -138,12 +139,12 @@ sub CLEAR {
     }
 }
 
-# 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] }
diff --git a/lib/Tie/Scalar.pm b/lib/Tie/Scalar.pm
new file mode 100644
index 0000000000..2db02ae1da
--- /dev/null
+++ b/lib/Tie/Scalar.pm
@@ -0,0 +1,138 @@
+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;
diff --git a/lib/Tie/SubstrHash.pm b/lib/Tie/SubstrHash.pm
index 6250e73848..a01c66ef8d 100644
--- a/lib/Tie/SubstrHash.pm
+++ b/lib/Tie/SubstrHash.pm
@@ -1,4 +1,40 @@
-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 {