NAME

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

VERSION

This document describes version 0.240 of Data::Dmp (from Perl distribution Data-Dmp), released on 2020-04-07.

SYNOPSIS

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

Print truncated dump (capped at "$Data::Dmp::OPT_MAX_DUMP_LEN_BEFORE_ELLIPSIS" characters):

 use Data::Dmp qw(dd_ellipsis dmp_ellipsis);
 dd_ellipsis [1..100];

DESCRIPTION

Data::Dmp is a Perl dumper like Data::Dumper. It's compact (only about 200 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.

VARIABLES

$Data::Dmp::OPT_PERL_VERSION

String, 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.

$Data::Dmp::OPT_MAX_DUMP_LEN_BEFORE_ELLIPSIS

Int, default: 70.

Used by "dd_ellipsis" and "dmp_ellipsis".

BENCHMARKS

 [1..10]:
                      Rate    Data::Dump Data::Dumper Data::Dmp
 Data::Dump    32032+-55/s            --       -64.6%    -73.9%
 Data::Dumper 90580+-110/s 182.77+-0.59%           --    -26.1%
 Data::Dmp    122575+-43/s 282.66+-0.67% 35.32+-0.17%        --
 
 [1..100]:
                       Rate    Data::Dump   Data::Dmp Data::Dumper
 Data::Dump   3890.6+-5.9/s            --      -73.7%       -73.7%
 Data::Dmp     14768.3+-5/s 279.59+-0.59%          --        -0.1%
 Data::Dumper   14790+-87/s   280.2+-2.3% 0.15+-0.59%           --
 
 Some mixed structure:
                     Rate    Data::Dump   Data::Dmp Data::Dumper
 Data::Dump    9035+-17/s            --      -68.3%       -80.9%
 Data::Dmp    28504+-10/s 215.47+-0.59%          --       -39.6%
 Data::Dumper 47188+-55/s   422.3+-1.1% 65.55+-0.2%           --

FUNCTIONS

dd

Usage:

 dd($data, ...); # returns $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

Usage:

 my $dump = dmp($data, ...);

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

dd_ellipsis

Usage:

 dd_ellipsis($data, ...); # returns data

Just like "dd", except will truncate its output to "$Data::Dmp::OPT_MAX_DUMP_LEN_BEFORE_ELLIPSIS" characters if dump is too long. Note that truncated dump will probably not be valid Perl code.

dmp_ellipsis

Usage:

 my $dump = dd_ellipsis($data, ...); # returns data

Just like "dmp", except will truncate dump result to "$Data::Dmp::OPT_MAX_DUMP_LEN_BEFORE_ELLIPSIS" characters if dump is too long. Note that truncated dump will probably not be valid Perl code.

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) 2020, 2017, 2016, 2015, 2014 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.