NAME

ESPPlus::Storage - An interface to ESP+ Storage repository files

SYNOPSIS

  use ESPPlus::Storage;
  my $st = ESPPlus::Storage->new
      ( { filename => $Repository,
          uncompress_function => \&uncompress } );

DESCRIPTION

This module provides an interface to the ESP+ Storage repository files. It allows you to read a .REP file as a series of original records. See ESPPlus::Storage::Reader::Tie for an especially easy interface for reading databases.

For an even easier interface, see ESPPlus::Storage::Reader::Tie. It wraps the interface described below and in ESPPlus::Storage::Reader and ESPPlus::Storage::Record.

CONSTRUCTOR

new

 $db = ESPPlus::Storage->new( { compress_function   => \ &compress,
                                uncompress_function => \ &uncompress,
                                ( $handle ? ( handle   => $handle ) :
                                            ( filename => $filename ) )
                            } )

This is the class constructor and it takes four optional arguments, two of them contradictory. It returns a new ESPPlus::Storage object. All of the arguments are passed in data in a hash reference.

The compress_function and uncompress_function parameters both expect code references. uncompress_function is expected to accept a reference to a .Z compressed string and is expected to return a reference to an uncompressed string. This is required for reading .REP repository records.

compress_function is the exact opposite, it is needed for writing to .REP repositories, accepts a reference to uncompressed data and returns a reference to .Z compressed data.

Currently there is no LZW implementation on www.cpan.org so the current expectation is that you will write a wrapper over /usr/bin/uncompress. A sample wrapper is included farther down in the documentation.

The two parameters filename and handle are complementary. If you supply only a filename then it will be opened for you otherwise pass in an already opened handle to a .REP file via handle.

METHODS / PROPERTIES

compress_function

When called without arguments it returns the ESPPlus::Storage object's stored compress_function code reference. When called with a value, it saves that as the new value.

 my $c = $db->compress_function;
 $db->compress_function( $new_c );

uncompress_function

When called without arguments it returns the ESPPlus::Storage object's stored uncompress_function code reference. When called with a value, it saves that as the new value.

 my $c = $db->uncompress_function;
 $db->uncompress_function( $new_c );

filename

When called without arguments it returns the ESPPlus::Storage object's stored filename. When called with a value, it saves that as the new value.

 my $f = $db->filename;
 $db->filename( $new_f );

handle

When called without arguments it returns a stored IO::File object if there is one. If there isn't then it attempts to open one by using filename. When called with a value it saves that as the new value.

 my $h = $db->handle;
 $db->handle( $h );

reader

This returns a ESPPlus::Storage::Reader object. This is what reads a .REP database file.

writer

This returns a ESPPlus::Storage::Writer object. This creates .REP database files.

UNCOMPRESS WRAPPER

 The following function is a sample implementation of a function suitable
 for passing into <uncompress_function>.

 our $TempFile = `mktemp /tmp/esp.XXX`;
 our $Uncompress = "/usr/bin/uncompress";
 sub uncompress {
     my $compressed = shift;
 
     {
         my $out = IO::File->new;
         sysopen $out, $TempFile, O_WRONLY
             or die "Couldn't open $TempFile: $!";
         flock $out, LOCK_EX
             or die "Couldn't get an exclusive lock on $TempFile: $!";
         truncate $out, 0
             or die "Couldn't truncate $TempFile: $!";
         binmode $out
             or die "Could binmode $TempFile: $!";
         print $out $$compressed
             or die "Couldnt write to $TempFile: $!";
         close $out
             or die "Couldn't close $TempFile: $!";
     }
 
     # add error processing as above
     my $in = IO::Handle->new;
     {
         my $sleep_count = 0;
         my $pid = open $in, "-|", $Uncompress, '-c', $TempFile
             or die "Can't exec $Uncompress: $!";
         unless (defined $pid) {
             warn "Cannot fork: $!";
             die "Bailing out" if $sleep_count++ > 6;
             sleep 10;
             redo;
         }
     }
 
     local $/;
     binmode $in or die "Couldn't binmode \$in: $!";
     my $uncompressed = <$in>;
     close $in or warn "$Uncompress exited $?";
 
     return \ $uncompressed;
 }

COPYRIGHT AND LICENSE

Copyright 2003, Joshua b. Jore. All rights reserved.

This program is free software; you can redistribute it and/or modify it under the terms of either:

a) the GNU General Public License as published by the Free Software Foundation; version 2, or

b) the "Artistic License" which comes with Perl.

SEE ALSO

ESPPlus::Storage::Reader ESPPlus::Storage::Reader::Tie ESPPlus::Storage::Writer ESPPlus::Storage::Record