NAME

Tie::Array::File::LazyRead - Read a file record by record using tied array and for()

VERSION

This document describes version 0.001 of Tie::Array::File::LazyRead (from Perl distribution Tie-Array-File-LazyRead), released on 2019-04-16.

SYNOPSIS

Given FILENAME.txt containing:

 line1
 line2
 line3

Then this Perl script:

 use Tie::Array::File::LazyRead;

 tie my @ary, 'Tie::Array::File::LazyRead', 'FILENAME.txt', {accumulate=>1}; # default for accumulate is 0

 for my $line (@ary) {
     print $line;
 }

will print:

 line1
 line2
 line3

and @ary containing:

 ["line1", "line2", "line3"]

If accumulate is set to 0 (the default), @ary will contain:

 [undef, undef, "line3"]

(i.e. only the last element/line will be remembered.

DESCRIPTION

EXPERIMENTAL, PROOF-OF-CONCEPT.

When for() is given a tied array:

 for (@tied_array) {
     ...
 }

it will invoke FETCHSIZE on the tied array to find out the size, then FETCH(0), then FETCHSIZE() again, then FETCH(1), and so on. In other words, FETCHSIZE is called on each iteration. This makes it possible to only fetch new data in FETCHSIZE instead of FETCH.

Without using for():

 tie my @ary, 'Tie::Array::File::LazyRead', 'FILENAME.txt';

 print $ary[0];

will not print anything, and the first line of the file is not fetched. To fetch one more line, you need to do:

 my $size = @ary;
 # then
 print $ary[0];

and so on.

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/Tie-Array-File-LazyRead.

SOURCE

Source repository is at https://github.com/perlancar/perl-Tie-Array-File-LazyRead.

BUGS

Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Tie-Array-File-LazyRead

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

SEE ALSO

AUTHOR

perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2019 by perlancar@cpan.org.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

cpanm Tie::Array::File::LazyRead

perl -MCPAN -e shell
install Tie::Array::File::LazyRead