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Hash::Util - Port of Perl 5's Hash::Util 0.22
use Hash::Util < lock_hash unlock_hash lock_hash_recurse unlock_hash_recurse lock_keys lock_keys_plus unlock_keys lock_value unlock_value hash_locked hash_unlocked hidden_keys legal_keys all_keys >; my %hash = foo => 42, bar => 23; # Ways to restrict a hash lock_keys(%hash); lock_keys(%hash, @keyset); lock_keys_plus(%hash, @additional_keys); # Ways to inspect the properties of a restricted hash my @legal = legal_keys(%hash); my @hidden = hidden_keys(%hash); all_keys(%hash,@keys,@hidden); my $is_locked = hash_locked(%hash); # Remove restrictions on the hash unlock_keys(%hash); # Lock individual values in a hash lock_value( %hash, 'foo'); unlock_value(%hash, 'foo'); # Ways to change the restrictions on both keys and values lock_hash (%hash); unlock_hash(%hash);
Hash::Util contains a set of functions that support restricted hashes. It 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 ability to ensure that an individual value cannot be changed.
By default Hash::Util does not export anything.
If you want to use this module for the sole purpose of only once locking a hash into an immutable state (calling only
lock_hash once on a hash), then it is much better to turn your hash into a
Map upon initialization by adding the
is Map trait:
my %hash is Map = foo => 42, bar => 23;
This will have exactly the same effect as:
my %hash = foo => 42, bar => 23; lock_hash(%hash);
but won't need to load the
Hash::Util module and will be much better performant because it won't need any additional run-time checks, because
Map is the immutable version of
Hash in Perl 6.
Functions that pertain to the unique implementation of Perl 5 hashes, have not been ported. These include:
hash_seed hash_value hv_store bucket_stats bucket_info bucket_array hash_traversal_mask
Also field hashes (the tools to create inside-out objects) have not been ported is these were deemed rather useless in the Perl 6 environment where everything is a true object. This pertains to the functions:
Since the concept of references does not exist as such in Perl 6, it didn't make sense to separately port the "ref" versions of the subroutines. They are however available as aliases to the non "ref" versions::
lock_hashref unlock_hashref lock_hashref_recurse unlock_hashref_recurse lock_ref_keys lock_ref_keys_plus unlock_ref_keys lock_ref_value unlock_ref_value hashref_locked hashref_unlocked
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.
:exists will still work, but will not alter the set of allowed keys. Returns the hash it worked on.
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. Returns the hash it worked on.
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
Locks 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 the hash on which it operated.
Unlocks the value for an individual key of a hash. Returns the hash on which it operated.
Locks an entire hash, making all keys and values read-only. No value can be changed, no keys can be added or deleted. Returns the hash it operated on. If you only want to lock a hash only once after it has been initialized, it's better to make it a
my %hash is Map = foo => 42, bar => 23;
This will have the same effect as
lock_hash, but will be much more performant as no extra overhead is needed for checking access at runtime.
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 the hash it operated on.
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. Returns the hash it originally operated on.
This method 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.
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. Returns the hash it originally operated on.
Identical recursion restrictions apply as to
say "Hash is locked!" if hash_locked(%hash);
Returns true if the hash and/or its keys are locked.
say "Hash is unlocked!" if hash_unlocked(%hash);
Returns true if the hash and/or its keys are not locked.
my @legal = 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
my @hidden = 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
In the case of an unrestricted hash this will return an empty list.
Populates the arrays @visible 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 the hash it operated on.
Elizabeth Mattijsen firstname.lastname@example.org
Source can be located at: https://github.com/lizmat/Hash-Util . Comments and Pull Requests are welcome.
Copyright 2018 Elizabeth Mattijsen
This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.
Re-imagined from the Perl 5 version as part of the CPAN Butterfly Plan. Perl 5 version originally developed by the Perl 5 Porters, subsequently maintained by Steve Hay.