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NAME
Data::Dmp - Dump Perl data structures as Perl code
VERSION
This document describes version 0.242 of Data::Dmp (from Perl
distribution Data-Dmp), released on 2022-08-28.
SYNOPSIS
use Data::Dmp; # exports dd() and dmp()
dd [1, 2, 3]; # prints "[1,2,3]"
$var = dmp({a => 1}); # -> "{a=>1}"
Print truncated dump (capped at
"$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.
$Data::Dmp::OPT_MAX_DUMP_LEN_BEFORE_ELLIPSIS
Int, default: 70.
Used by "dd_ellipsis" and "dmp_ellipsis".
BENCHMARKS
[1..10]:
Rate/s Precision/s Data::Dump Data::Dumper Data::Dmp
Data::Dump 24404 95 -- -61.6% -75.6%
Data::Dumper 63580 210 160.5+-1.3% -- -36.4%
Data::Dmp 99940 130 309.5+-1.7% 57.18+-0.55% --
[1..100]:
Rate/s Precision/s Data::Dump Data::Dumper Data::Dmp
Data::Dump 2934.3 7.8 -- -75.3% -76.2%
Data::Dumper 11873 32 304.6+-1.5% -- -3.7%
Data::Dmp 12323.4 4 320+-1.1% 3.8+-0.28% --
Some mixed structure:
Rate/s Precision/s Data::Dump Data::Dmp Data::Dumper
Data::Dump 7161 12 -- -69.3% -78.7%
Data::Dmp 23303 29 225.43+-0.7% -- -30.6%
Data::Dumper 33573 56 368.8+-1.1% 44.07+-0.3% --
FUNCTIONS
dd
Usage:
dd($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>.
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>
CONTRIBUTING
To contribute, you can send patches by email/via RT, or send pull
requests on GitHub.
Most of the time, you don't need to build the distribution yourself. You
can simply modify the code, then test via:
% prove -l
If you want to build the distribution (e.g. to try to install it locally
on your system), you can install Dist::Zilla,
Dist::Zilla::PluginBundle::Author::PERLANCAR,
Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two
other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps
required beyond that are considered a bug and can be reported to me.
COPYRIGHT AND LICENSE
This software is copyright (c) 2022, 2021, 2020, 2017, 2016, 2015, 2014
by perlancar <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.
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.
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