Hash::Util

NAME

SYNOPSIS

DESCRIPTION

Hash::Util contains a set of functions that support restricted hashes. These are described in this document. Hash::Util::FieldHash contains an (unrelated) set of functions that support the use of hashes in inside-out classes, described in Hash::Util::FieldHash.

By default Hash::Util does not export anything.  

Restricted hashes

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. Note that if any of the values of the hash have been locked they will not be unlocked after this sub executes. Both routines return a reference to the hash operated on.

lock_keys_plus

lock_keys_plus(%hash,@additional_keys) Similar to lock_keys(), with the difference being that the optional key list specifies keys that may or may not be already in the hash. Essentially this is an easier way to say lock_keys(%hash,@additional_keys,keys %hash); Returns a reference to %hash

lock_value

unlock_value

lock_value (%hash, $key); unlock_value(%hash, $key); Locks and unlocks the value for an individual key of a hash. The value of a locked key cannot be changed. Unless %hash has already been locked the key/value could be deleted regardless of this setting. Returns a reference to the %hash.

lock_hash

unlock_hash

lock_hash(%hash); lock_hash() locks an entire hash, making all keys and values read-only. 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 writable. All values can be changed and keys can be added and deleted. Returns a reference to the %hash.

lock_hash_recurse

unlock_hash_recurse

lock_hash_recurse(%hash); lock_hash() locks an entire hash and any hashes it references recursively, making all keys and values read-only. No value can be changed, no keys can be added or deleted. Only recurses into hashes that are referenced by another hash. Thus a Hash of Hashes (HoH) will all be restricted, but a Hash of Arrays of Hashes (HoAoH) will only have the top hash restricted. unlock_hash_recurse(%hash); unlock_hash_recurse() does the opposite of lock_hash_recurse(). All keys and values are made writable. All values can be changed and keys can be added and deleted. Identical recursion restrictions apply as to lock_hash_recurse(). Returns a reference to the %hash.

hash_unlocked

hash_unlocked(%hash) and print "Hash is unlocked!\n"; Returns true if the hash and its keys are unlocked.

legal_keys

my @keys = legal_keys(%hash); Returns the list of the keys that are legal in a restricted hash. In the case of an unrestricted hash this is identical to calling keys(%hash).

hidden_keys

my @keys = hidden_keys(%hash); Returns the list of the keys that are legal in a restricted hash but do not have a value associated to them. Thus if 'foo' is a hidden key of the %hash it will return false for both defined and exists tests. In the case of an unrestricted hash this will return an empty list. NOTE this is an experimental feature that is heavily dependent on the current implementation of restricted hashes. Should the implementation change, this routine may become meaningless, in which case it will return an empty list.

all_keys

all_keys(%hash,@keys,@hidden); Populates the arrays @keys with the all the keys that would pass an exists tests, and populates @hidden with the remaining legal keys that have not been utilized. Returns a reference to the hash. In the case of an unrestricted hash this will be equivalent to $ref = do { @keys = keys %hash; @hidden = (); \%hash }; NOTE this is an experimental feature that is heavily dependent on the current implementation of restricted hashes. Should the implementation change this routine may become meaningless in which case it will behave identically to how it would behave on an unrestricted hash.

hash_seed

my $hash_seed = hash_seed(); hash_seed() returns the seed number used to randomise hash ordering. Zero means the traditional random hash ordering, non-zero means the new even more random hash ordering introduced in Perl 5.8.1. Note that the hash seed is sensitive information: by knowing it one can craft a denial-of-service attack against Perl code, even remotely, see Algorithmic Complexity Attacks in perlsec for more information. Do not disclose the hash seed to people who don't need to know it. See also PERL_HASH_SEED_DEBUG in perlrun.

hv_store

my $sv = 0; hv_store(%hash,$key,$sv) or die "Failed to alias!"; $hash{$key} = 1; print $sv; # prints 1 Stores an alias to a variable in a hash instead of copying the value.

Operating on references to hashes.

lock_ref_keys

unlock_ref_keys

lock_ref_keys_plus

lock_ref_value

unlock_ref_value

lock_hashref

unlock_hashref

lock_hashref_recurse

unlock_hashref_recurse

hash_ref_unlocked

legal_ref_keys

hidden_ref_keys

CAVEATS

eval { %hash = (illegal_key => 1) }

leaves the %hash empty rather than with its original contents.  

BUGS

AUTHOR

hv_store() is from Array::RefElem, Copyright 2000 Gisle Aas.

Additional code by Yves Orton.  

SEE ALSO

Hash::Util::FieldHash.

Index

NAME

SYNOPSIS

DESCRIPTION

Restricted hashes

Operating on references to hashes.

CAVEATS

BUGS

AUTHOR

SEE ALSO