=pod
=encoding utf8
=for html
=head1 NAME
Sereal - A binary serialization format
=head1 SYNOPSIS
This repository is the home of the Sereal data serialization format. This
format was started because the authors had technical reasons for producing
a better Storable.
Before we embarked on this project we had a look at various prior art. This
included a review of Google Protocol Buffers and of the MessagePack protocol.
Neither suited our needs so we designed this, liberally borrowing ideas from
the other projects.
=head1 DESCRIPTION
=head2 OBJECTIVES
=head3 References
We wanted to be able to serialize shared references properly. Many
serialization formats do not support this out of the box.
=head3 Weak References
Given that perl uses a reference counting garbage collection scheme,
Perl has the concept of a special type of reference called a
"weakref" which is used to create cyclic reference structures which do
not leak memory. Unlike most of the existing solutions, we need to handle
these structures correctly, thus avoiding a perfectly valid data structure
to be converted to one that will cause a memory leak on a remote system.
For cross-language compatibility, weak references can very easily
be ignored by other decoder implementations.
=head3 Aliases
Perl supports aliases. These are a special kind of reference which is
effectively a C level pointer instead of a Perl language-level
reference. We needed to be able to represent these as well.
=head3 Objects
Promoting a plain data structure reference to an object, as is customary
in dynamic languages, can be dangerous in some circumstances. We needed
to be able to serialize objects safely and reliably, and we wanted a
sane control mechanism for doing so.
=head3 Regular Expression Objects
In Perl, a regular expression is a native type. We wanted to be
able serialize these at a native level without losing data
such as modifiers.
=head3 Space Efficiencies
We want to be able to represent common structures as small as is
reasonable. Although not to the extreme that this makes the protocol
error prone and ludicrously difficult to implement. The steps taken
include removing redundancy from the serialized structure
(such as hash keys or classnames) automatically. The protocol supports
this kind of redundancy removal, but an encoder implementation can
choose to which extent it makes use of the technique.
=head3 Speed Efficiencies
We want to be able to serialize and deserialize quickly. Some of the design
decisions and trade-offs were aimed squarely at performance.
=head3 Separate Decoder and Encoder
We wanted to separate the functions of serializing from deserializing
so they could be upgraded independently.
=head3 Forward/Backward Compatibility
We wanted the protocol to be robust to forward/backwards compatibility
issues. It should be possible to partially read new formats with an
old decoder, and output old formats with a new encoder.
=head3 Language Agnosticism
We want the format to be usable by other languages, especially dynamic
languages. In aim of making
this easier we have structured our repo so that implementations from other
languages can be easily added, and we would welcome any contributions
along these lines.
=head2 Performance Analysis
There are some graphs of how the Perl implementations Sereal performs as
compared to the alternatives at
L<Sereal Performance Graphs, https://github.com/Sereal/Sereal/wiki/Sereal-Comparison-Graphs>
=head1 SPECIFICATION
You can find the specification at
L<sereal_spec.pod, https://github.com/Sereal/Sereal/blob/master/sereal_spec.pod>
=head1 DISCUSSION GROUPS
There is a low-traffic announcement mailing list
L<sereal-announce, https://groups.google.com/forum/?fromgroups#!forum/sereal-announce>
as well as a more general development list
L<sereal-dev, https://groups.google.com/forum/?fromgroups#!forum/sereal-dev>
=head1 AUTHOR
Yves Orton Edemerphq@gmail.comE
Damian Gryski Edamian@gryski.comE
Steffen Mueller Esmueller@cpan.orgE
Rafaël Garcia-Suarez
Ævar Arnfjörð Bjarmason Eavar@cpan.orgE
=head1 ACKNOWLEDGMENT
This protocol was originally developed for Booking.com. With approval
from Booking.com, the code and specification were generalized and
published as Open Source on github and CPAN, for which the authors
would like to express their gratitude.
=head1 COPYRIGHT AND LICENSE
Copyright (C) 2012, 2013, 2014 by Steffen Mueller
Copyright (C) 2012, 2013, 2014 by Yves Orton
=cut