ch19.032_best_ex19.9

来自「Perl Best Practices the source code」· 9 代码 · 共 40 行

##############################################################################
##   Example 19.9 (Recommended) from Chapter 19 of "Perl Best Practices"    ##
##     Copyright (c) O'Reilly & Associates, 2005. All Rights Reserved.      ##
##  See: http://www.oreilly.com/pub/a/oreilly/ask_tim/2001/codepolicy.html  ##
##############################################################################


#  Example 19-9. Adding a cache to a digest subroutine


# Standard modules...
use strict;
use warnings;
use IO::Prompt;
use Carp;
use English qw( -no_match_vars );
use Data::Alias;
use Readonly;


{
    my %cache;
 
    sub lc_digest {
        my $text = lc shift;
 
        # Compute the answer only if it's not already known...
        if (!exists $cache{$text}) {
            use Digest::SHA qw( sha512 );
            $cache{$text} = sha512($text);
        }
 
        return $cache{$text};
    }
}

for my $text ( ('foo was here' x 1_000_000) x 100 ) {
    print lc_digest($text), "\n";
}