Author image Leo Charre
and 1 contributors

NAME

Alister::Base::Sums - subroutines for managing a sum disgest database table

DESCRIPTION

I have a package Alister and a package Zack, they both need to track metadata with a 'sum' as main identifier (of the main data of interest).

This is a stand-alone module which lets you:

   -Create and manage a 'sums' table in a database to track a collection of unique sum digests.
   -It is by itself not OO, but meant to be perhaps used to implement this in OO fashion.

This package does not include features on interacting with the filesystem, this is out of scope. For good reasons. To isolate the problems. This package was part of Alister. But Alister is complicated, potentially. I hope to isolate some probems here.

(The goal here is to isolate the tracking of sums. This stores a sum, retrieves it, etc to a db table.

This is used by Alister, and could be used by Zack. And other programs storing info against md5sums in general. )

SUBS

None are exported by default.

validate_argument_sum()

Argument is a 'sum'. Returns same argument. Dies if argumement is missing. If not real sum, returns undef.

validate_argument_id()

Argument is a 'id', returns same argument or undef if not a id. A id is a number such as in the table.

sum_add()

First argument is 'dbh'. Second argument is 'sum'. Returns id.

Warns and returns undef on failure.

If you do not pass any argument as sum, will throw an exception.

sum_add() is designed so you can it multiple times for same sum, and will return same id. It does not guarantee that the sum was not already in there.

sum_get()

First argument is 'dbh'. Second argument is either 'sum' or 'id'. If argument is sum, returns id, if is id, returns sum. On fail, returns undef.

If you do not pass any argument as dbh and sum, will throw an exception.

   sum_get($dbh, 5);
   sum_get($dbh, '4446d445d6fc77b0b8d12e5e0e5da6f5');

If the sum is not there, returns

sum_delete()

First argument is dbh. Second argument is either a sum or a sum id. Returns how many were deleted. (should be one or 0)

sum_update()

First argument is dbh. Second argument is either a sum or a sum id. Returns true or false.

If this returns true, it's because you tried to update to a sum that already exists elsewhere.

   unless( sum_update( $dbh, $oldsum, $newsum ) ){
      # already there?
      my $id = sum_get($newsum);
      warn("Already exists with id $newsum.");
      
      # maybe delete old one?
      sum_delete( $dbh, $oldsum );
   }

It seems that if the sum is already there, it should update in some way anyways, but this is out of scope here.

table_create_sums()

Argument is dbh. Table must not already exist.

table_reset_sums()

Argument is dbh. If table exists, drops before creating.

$Alister::Base::Sums::TABLE_NAME

By default, 'sums'.

$Alister::Base::Sums::SQL_LAYOUT

Holds table layout. By default:

   CREATE TABLE $TABLE_NAME (
      id int(20) AUTO_INCREMENT PRIMARY KEY,
      sum varchar(32) NOT NULL UNIQUE 
   );
   

Obviously if you chose to override validate_sum() for use with some other digest algorythm, this needs to be altered.

TERMINOLOGY

sum

A sum is a string 32 characters long. The characters can be 0-9 and a-f.

sum_id

This is the id in the sums table

dbh

This is a DBI object. The creation of this object is out of scope here.

sums

This is the default name of the sums table.

CAVEATS

This module is in development. Not ready as API.

AUTHOR

Leo Charre leocharre at cpan dot org

LICENSE

This package is free software; you can redistribute it and/or modify it under the same terms as Perl itself, i.e., under the terms of the "Artistic License" or the "GNU General Public License".

DISCLAIMER

This package is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

See the "GNU General Public License" for more details.