Hash::Util(3pm) 					 Perl Programmers Reference Guide					   Hash::Util(3pm)

NAME

       Hash::Util - A selection of general-utility hash subroutines

SYNOPSIS

	 use Hash::Util qw(lock_keys   unlock_keys
			   lock_value  unlock_value
			   lock_hash   unlock_hash);

	 %hash = (foo => 42, bar => 23);
	 lock_keys(%hash);
	 lock_keys(%hash, @keyset);
	 unlock_keys(%hash);

	 lock_value  (%hash, 'foo');
	 unlock_value(%hash, 'foo');

	 lock_hash  (%hash);
	 unlock_hash(%hash);

DESCRIPTION

       "Hash::Util" contains special functions for manipulating hashes that don't really warrant a keyword.

       By default "Hash::Util" does not export anything.

       Restricted hashes

       5.8.0 introduces the ability to restrict a hash to a certain set of keys.  No keys outside of this set can be added.  It also introduces
       the ability to lock an individual key so it cannot be deleted and the value cannot be changed.

       This is intended to largely replace the deprecated pseudo-hashes.

       lock_keys
       unlock_keys
	     lock_keys(%hash);
	     lock_keys(%hash, @keys);

	   Restricts the given %hash's set of keys to @keys.  If @keys is not given it restricts it to its current keyset.  No more keys can be
	   added. delete() and exists() will still work, but will not alter the set of allowed keys. Note: the current implementation prevents the
	   hash from being bless()ed while it is in a locked state. Any attempt to do so will raise an exception. Of course you can still bless()
	   the hash before you call lock_keys() so this shouldn't be a problem.

	     unlock_keys(%hash);

	   Removes the restriction on the %hash's keyset.

       lock_value
       unlock_value
	     lock_value  (%hash, $key);
	     unlock_value(%hash, $key);

	   Locks and unlocks an individual key of a hash.  The value of a locked key cannot be changed.

	   %hash must have already been locked for this to have useful effect.

       lock_hash
       unlock_hash
	       lock_hash(%hash);

	   lock_hash() locks an entire hash, making all keys and values readonly.  No value can be changed, no keys can be added or deleted.

	       unlock_hash(%hash);

	   unlock_hash() does the opposite of lock_hash().  All keys and values are made read/write.  All values can be changed and keys can be
	   added and deleted.

AUTHOR

       Michael G Schwern <schwern@pobox.com> on top of code by Nick Ing-Simmons and Jeffrey Friedl.

SEE ALSO

       Scalar::Util, List::Util, Hash::Util

perl v5.8.0							    2002-06-01							   Hash::Util(3pm)