Home Man
Today's Posts

Linux & Unix Commands - Search Man Pages

RedHat 9 (Linux i386) - man page for tie::memoize (redhat section 3pm)

Tie::Memoize(3pm)		 Perl Programmers Reference Guide		Tie::Memoize(3pm)

       Tie::Memoize - add data to hash when needed

	 require Tie::Memoize;
	 tie %hash, 'Tie::Memoize',
	     \&fetch,		       # The rest is optional
	     $DATA, \&exists,
	     {%ini_value}, {%ini_existence};

       This package allows a tied hash to autoload its values on the first access, and to use the
       cached value on the following accesses.

       Only read-accesses (via fetching the value or "exists") result in calls to the functions;
       the modify-accesses are performed as on a normal hash.

       The required arguments during "tie" are the hash, the package, and the reference to the
       "FETCH"ing function.  The optional arguments are an arbitrary scalar $data, the reference
       to the "EXISTS" function, and initial values of the hash and of the existence cache.

       Both the "FETCH"ing function and the "EXISTS" functions have the same signature: the argu-
       ments are "$key, $data"; $data is the same value as given as argument during tie()ing.
       Both functions should return an empty list if the value does not exist.	If "EXISTS" func-
       tion is different from the "FETCH"ing function, it should return a TRUE value on success.
       The "FETCH"ing function should return the intended value if the key is valid.

Inheriting from Tie::Memoize
       The structure of the tied() data is an array reference with elements

	 0:  cache of known values
	 1:  cache of known existence of keys
	 2:  FETCH  function
	 3:  EXISTS function
	 4:  $data

       The rest is for internal usage of this package.	In particular, if TIEHASH is overwritten,
       it should call SUPER::TIEHASH.

	 sub slurp {
	   my ($key, $dir) = shift;
	   open my $h, '<', "$dir/$key" or return;
	   local $/; <$h>		       # slurp it all
	 sub exists { my ($key, $dir) = shift; return -f "$dir/$key" }

	 tie %hash, 'Tie::Memoize', \&slurp, $directory, \&exists,
	     { fake_file1 => $content1, fake_file2 => $content2 },
	     { pretend_does_not_exists => 0, known_to_exist => 1 };

       This example treats the slightly modified contents of $directory as a hash.  The modifica-
       tions are that the keys fake_file1 and fake_file2 fetch values $content1 and $content2,
       and pretend_does_not_exists will never be accessed.  Additionally, the existence of
       known_to_exist is never checked (so if it does not exists when its content is needed, the
       user of %hash may be confused).

       FIRSTKEY and NEXTKEY methods go through the keys which were already read, not all the pos-
       sible keys of the hash.

       Ilya Zakharevich <mailto:perl-module-hash-memoize@ilyaz.org>.

perl v5.8.0				    2002-06-01				Tie::Memoize(3pm)

All times are GMT -4. The time now is 01:45 AM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
Show Password