/ 
Sereal-Encoder-0.20
River stage three • 32 direct dependents • 111 total dependents
/ Sereal::Encoder

NAME

Sereal::Encoder - Fast, compact, powerful binary serialization

SYNOPSIS

use Sereal::Encoder qw(encode_sereal);

my $encoder = Sereal::Encoder->new({...options...});
my $out = $encoder->encode($structure);
# alternatively:
$out = encode_sereal($structure, {... options ...});

DESCRIPTION

This is an experimental module. The interface may change without notice. Before using it in production, please get in touch with the authors!

This library implements an efficient, compact-output, and feature-rich serializer using a binary protocol called Sereal. Its sister module Sereal::Decoder implements a decoder for this format. The two are released separately to allow for independent and safer upgrading.

The Sereal protocol version emitted by this encoder implementation is currently protocol version 1.

The protocol specification and many other bits of documentation can be found in the github repository. Right now, the specification is at https://github.com/Sereal/Sereal/blob/master/sereal_spec.pod, there is a discussion of the design objectives in https://github.com/Sereal/Sereal/blob/master/README.pod, and the output of our benchmarks can be seen at https://github.com/Sereal/Sereal/wiki/Sereal-Comparison-Graphs.

CLASS METHODS

new

Constructor. Optionally takes a hash reference as first parameter. This hash reference may contain any number of options that influence the behaviour of the encoder. Currently, the following options are recognized:

no_shared_hashkeys

When the no_shared_hashkeys option is set ot a true value, then the encoder will disable the detection and elimination of repeated hash keys. This only has an effect for serializing structures containing hashes. By skipping the detection of repeated hash keys, performance goes up a bit, but the size of the output can potentially be much larger. Do not disable this unless you have a reason to.

snappy

If set, the main payload of the Sereal document will be compressed using Google's Snappy algorithm. This can yield anywhere from no effect to significant savings on output size at rather low run time cost. If in doubt, test with your data whether this helps or not.

The decoder (version 0.04 and up) will know how to handle Snappy-compressed Sereal documents transparently.

snappy_threshold

The size threshold (in bytes) of the uncompressed output below which snappy compression is not even attempted even if enabled. Defaults to one kilobyte (1024 bytes). Set to 0 and snappy to enabled to always compress.

croak_on_bless

If this option is set, then the encoder will refuse to serialize blessed references and throw an exception instead.

This can be important because blessed references can mean executing a destructor on a remote system or generally executing code based on data.

undef_unknown

If set, unknown/unsupported data structures will be encoded as undef instead of throwing an exception.

Mutually exclusive with stringify_unknown. See also warn_unknown below.

stringify_unknown

If set, unknown/unsupported data structures will be stringified and encoded as that string instead of throwing an exception. The stringification may cause a warning to be emitted by perl.

Mutually exclusive with undef_unknown. See also warn_unknown below.

warn_unknown

Only has an effect if undef_unknown or stringify_unknown are enabled.

If set to a positive integer, any unknown/unsupported data structure encountered will emit a warning. If set to a negative integer, it will warn for unsupported data structures just the same as for a positive value with one exception: For blessed, unsupported items that have string overloading, we silently stringify without warning.

max_recursion_depth

Sereal::Encoder is recursive. If you pass it a Perl data structure that is deeply nested, it will eventually exhaust the C stack. Therefore, there is a limit on the depth of recursion that is accepted. It defaults to 10000 nested calls. You may choose to override this value with the max_recursion_depth option. Beware that setting it too high can cause hard crashes, so only do that if you KNOW that it is safe to do so.

Do note that the setting is somewhat approximate. Setting it to 10000 may break at somewhere between 9997 and 10003 nested structures depending on their types.

The thusly allocated encoder object and its output buffer will be reused between invocations of encode(), so hold on to it for an efficiency gain if you plan to serialize multiple similar data structures, but destroy it if you serialize a single very large data structure just once to free the memory.

INSTANCE METHODS

encode

Given a Perl data structure, serializes that data structure and returns a binary string that can be turned back into the original data structure by Sereal::Decoder.

EXPORTABLE FUNCTIONS

encode_sereal

The functional interface that is equivalent to using new and encode. Expects a data structure to serialize as first argument, optionally followed by a hash reference of options (see documentation for new()).

The functional interface is marginally slower than the OO interface since it cannot reuse the encoder object.

PERFORMANCE

The exact performance in time and space depends heavily on the data structure to be serialized. For ready-made comparison scripts, see the author_tools/bench.pl and author_tools/dbench.pl programs that are part of this distribution. Suffice to say that this library is easily competitive in both time and space efficiency with the best alternatives.

THREAD-SAFETY

Sereal::Encoder is thread-safe on Perl's 5.8.7 and higher. This means "thread-safe" in the sense that if you create a new thread, all Sereal::Encoder objects will become a reference to undef in the new thread. This might change in a future release to become a full clone of the encoder object.

AUTHOR

Yves Orton <demerphq@gmail.com>

Damian Gryski

Steffen Mueller <smueller@cpan.org>

Rafaël Garcia-Suarez

Ævar Arnfjörð Bjarmason <avar@cpan.org>

Some inspiration and code was taken from Marc Lehmann's excellent JSON::XS module due to obvious overlap in problem domain.

ACKNOWLEDGMENT

This module was originally developed for booking.com. With approval from booking.com, this module was generalized and published on CPAN, for which the authors would like to express their gratitude.

COPYRIGHT AND LICENSE

Copyright (C) 2012 by Steffen Mueller

The license for the code in this distribution is the following, with the exceptions listed below:

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

Except portions taken from Marc Lehmann's code for the JSON::XS module, which is licensed under the same terms as this module.

Also except the code for Snappy compression library, whose license is reproduced below and which, to the best of our knowledge, is compatible with this module's license. The license for the enclosed Snappy code is:

Copyright 2011, Google Inc.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

  * Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
  * Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
distribution.
  * Neither the name of Google Inc. nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

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