perlancar

NAME

Data::Dmp - Dump Perl data structures as Perl code

VERSION

This document describes version 0.23 of Data::Dmp (from Perl distribution Data-Dmp), released on 2017-01-30.

SYNOPSIS

 use Data::Dmp; # exports dd() and dmp()
 dd [1, 2, 3]; # prints "[1,2,3]"
 $a = dmp({a => 1}); # -> "{a=>1}"

DESCRIPTION

Data::Dmp is a Perl dumper like Data::Dumper. It's compact (only about 175 lines of code long), starts fast and does not use any non-core modules except Regexp::Stringify when dumping regexes. It produces compact single-line output (similar to Data::Dumper::Concise). It roughly has the same speed as Data::Dumper (usually a bit faster for smaller structures) and faster than Data::Dump, but does not offer the various formatting options. It supports dumping objects, regexes, circular structures, coderefs. Its code is first based on Data::Dump: I removed all the parts that I don't need, particularly the pretty formatting stuffs) and added some features that I need like proper regex dumping and coderef deparsing.

SETTINGS

$Data::Dmp::OPT_PERL_VERSION => str (default: 5.010)

Set target Perl version. If you set this to, say 5.010, then the dumped code will keep compatibility with Perl 5.10.0. This is used in the following ways:

  • passed to Regexp::Stringify

  • when dumping code references

    For example, in perls earlier than 5.016, feature.pm does not understand:

     no feature ':all';

    so we replace it with:

     no feature;

$Data::Dmp::OPT_REMOVE_PRAGMAS => bool (default: 0)

If set to 1, then pragmas at the start of coderef dump will be removed. Coderef dump is produced by B::Deparse and is of the form like:

 sub { use feature 'current_sub', 'evalbytes', 'fc', 'say', 'state', 'switch', 'unicode_strings', 'unicode_eval'; $a <=> $b }

If you want to dump short coderefs, the pragmas might be distracting. You can turn turn on this option which will make the above dump become:

 sub { $a <=> $b }

Note that without the pragmas, the dump might be incorrect.

$Data::Dmp::OPT_DEPARSE => bool (default: 1)

Can be set to 0 to skip deparsing code. Coderefs will be dumped as sub{"DUMMY"} instead, like in Data::Dump.

$Data::Dmp::OPT_STRINGIFY_NUMBERS => bool (default: 0)

If set to true, will dump numbers as quoted string, e.g. 123 as "123" instead of 123. This might be helpful if you want to compute the hash of or get a canonical representation of data structure.

BENCHMARKS

 [1..10]:
                       Rate    Data::Dump Data::Dumper Data::Dmp
 Data::Dump     30417+-55/s            --       -66.2%    -74.0%
 Data::Dumper   89888+-79/s  195.52+-0.6%           --    -23.1%
 Data::Dmp    116890+-160/s 284.29+-0.87% 30.04+-0.21%        --
 
 [1..100]:
                        Rate    Data::Dump  Data::Dmp Data::Dumper
 Data::Dump    3712.3+-7.9/s            --     -73.9%       -74.9%
 Data::Dmp    14211.3+-4.9/s 282.82+-0.82%         --        -3.8%
 Data::Dumper    14771+-28/s   297.9+-1.1% 3.94+-0.2%           --
 
 Some mixed structure:
                     Rate    Data::Dump    Data::Dmp Data::Dumper
 Data::Dump    8764+-16/s            --       -67.6%       -80.1%
 Data::Dmp    27016+-36/s  208.28+-0.7%           --       -38.6%
 Data::Dumper 43995+-13/s 402.02+-0.95% 62.85+-0.22%           --

FUNCTIONS

dd($data, ...) => $data ...

Exported by default. Like Data::Dump's dd (a.k.a. dump), print one or more data to STDOUT. Unlike Data::Dump's dd, it always prints and return the original data (like XXX), making it convenient to insert into expressions. This also removes ambiguity and saves one wantarray() call.

dmp($data, ...) => $str

Exported by default. Return dump result as string. Unlike Data::Dump's dd (a.k.a. dump), it never prints and only return the data.

FAQ

When to use Data::Dmp? How does it compare to other dumper modules?

Data::Dmp might be suitable for you if you want a relatively fast pure-Perl data structure dumper to eval-able Perl code. It produces compact, single-line Perl code but offers little/no formatting options. Data::Dmp and Data::Dump module family usually produce Perl code that is "more eval-able", e.g. it can recreate circular structure.

Data::Dump produces visually nicer output (some alignment, use of range operator to shorten lists, use of base64 for binary data, etc) but no built-in option to produce compact/single-line output. It's more suitable for debugging. It's also relatively slow. I usually use its variant, Data::Dump::Color, for console debugging.

Data::Dumper is a core module, offers a lot of formatting options (like disabling hash key sorting, setting verboseness/indent level, and so on) but you usually have to configure it quite a bit before it does exactly like you want (that's why there are modules on CPAN that are just wrapping Data::Dumper with some configuration, like Data::Dumper::Concise et al). It does not support dumping Perl code that can recreate circular structures.

Of course, dumping to eval-able Perl code is slow (not to mention the cost of re-loading the code back to in-memory data, via eval-ing) compared to dumping to JSON, YAML, Sereal, or other format. So you need to decide first whether this is the appropriate route you want to take. (But note that there is also Data::Dumper::Limited and Data::Undump which uses a format similar to Data::Dumper but lets you load the serialized data without eval-ing them, thus achieving the speed comparable to JSON::XS).

Is the output guaranteed to be single line dump?

No. Some things can still produce multiline dump, e.g. newline in regular expression.

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/Data-Dmp.

SOURCE

Source repository is at https://github.com/perlancar/perl-Data-Dmp.

BUGS

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

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

Data::Dump and other variations/derivate works in Data::Dump::*.

Data::Dumper and its variants.

Data::Printer.

YAML, JSON, Storable, Sereal, and other serialization formats.

AUTHOR

perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2017 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.