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RedHat 9 (Linux i386) - man page for hash::util (redhat section 3pm)

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)


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