Hash::Util(3)

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 it does not effect the set of allowed keys.

      unlock_keys(%hash;)

    Removes the restriction on the %hash's keyset.

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