UNIX ON-LINE Man Pages - Die Onlinehilfe

Die Syntax von Unixbefehlen wird in den entsprechenden Manpages dokumentiert. Hier können Sie diese Onlinehilfe für viele Standardbefehle abrufen.

Suchoptionen:
Seiten auflisten, welche beginnen mit:
A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z   ALPHA   NUM   ANDERE   ALLE
Hash::Util(3pm)        Perl Programmers Reference Guide        Hash::Util(3pm)

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

SYNOPSIS
         # Restricted hashes

         use Hash::Util qw(
                            hash_seed all_keys
                            lock_keys unlock_keys
                            lock_value unlock_value
                            lock_hash unlock_hash
                            lock_keys_plus hash_locked
                            hidden_keys legal_keys
                          );

         %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);
         my $ref = 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);

         my $hashes_are_randomised = hash_seed() != 0;

DESCRIPTION
       "Hash::Util" and "Hash::Util::FieldHash" contain special functions for
       manipulating hashes that don't really warrant a keyword.

       "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
       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
       ability to ensure that an individual 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.

           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.
       Most subroutines documented in this module have equivalent versions
       that operate on references to hashes instead of native hashes.  The
       following is a list of these subs. They are identical except in name
       and in that instead of taking a %hash they take a $hashref, and
       additionally are not prototyped.

       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
       Note that the trapping of the restricted operations is not atomic: for
       example

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

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

BUGS
       The interface exposed by this module is very close to the current
       implementation of restricted hashes. Over time it is expected that this
       behavior will be extended and the interface abstracted further.

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

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

       Additional code by Yves Orton.

SEE ALSO
       Scalar::Util, List::Util and "Algorithmic Complexity Attacks" in
       perlsec.

       Hash::Util::FieldHash.

perl v5.12.1                      2010-04-26                   Hash::Util(3pm)
 

Scannen Sie den Barcode um die Webseite zu öffnen


Quelle: http://www.trinler.net/de/service/doc/linux/man.html?command=Hash%3A%3AUtil
Gedruckt am: 12.12.2017 17:16 GMT+0100 (2017-12-12T17:16:28+01:00)