Provided by: libgoogle-protocolbuffers-perl_0.12-2_all 
NAME
Google::ProtocolBuffers - simple interface to Google Protocol Buffers
SYNOPSYS
##
## Define structure of your data and create serializer classes
##
use Google::ProtocolBuffers;
Google::ProtocolBuffers->parse("
message Person {
required string name = 1;
required int32 id = 2; // Unique ID number for this person.
optional string email = 3;
enum PhoneType {
MOBILE = 0;
HOME = 1;
WORK = 2;
}
message PhoneNumber {
required string number = 1;
optional PhoneType type = 2 [default = HOME];
}
repeated PhoneNumber phone = 4;
}
",
{create_accessors => 1 }
);
##
## Serialize Perl structure and print it to file
##
open my($fh), ">person.dat";
binmode $fh;
print $fh Person->encode({
name => 'A.U. Thor',
id => 123,
phone => [
{ number => 1234567890 },
{ number => 987654321, type=>Person::PhoneType::WORK() },
],
});
close $fh;
##
## Decode data from serialized form
##
my $person;
{
open my($fh), "<person.dat";
binmode $fh;
local $/;
$person = Person->decode(<$fh>);
close $fh;
}
print $person->{name}, "\n";
print $person->name, "\n"; ## ditto
DESCRIPTION
Google Protocol Buffers is a data serialization format. It is binary (and hence compact and fast for
serialization) and as extendable as XML; its nearest analogues are Thrift and ASN.1. There are official
mappings for C++, Java and Python languages; this library is a mapping for Perl.
METHODS
Google::ProtocolBuffers->parse($proto_text, \%options)
Google::ProtocolBuffers->parsefile($proto_filename, \%options)
Protocol Buffers is a typed protocol, so work with it starts with some kind of Interface Definition
Language named 'proto'. For the description of the language, please see the official page
(<http://code.google.com/p/protobuf/>) Methods 'parse' and 'parsefile' take the description of data
structure as text literal or as name of the proto file correspondently. After successful compilation,
Perl serializer classes are created for each message, group or enum found in proto. In case of error,
these methods will die. On success, a list of names of created classes is returned. Options are given as
a hash reference, the recognizable options are:
include_dir => [ $dir_name ]
One proto file may include others, this option sets where to look for the included files. Multiple
dirs should be specificed as an ARRAYREF.
generate_code => $filename or $file_handler
Compilation of proto source is a relatively slow and memory consuming operation, it is not
recommended in production environment. Instead, with this option you may specify filename or
filehandle where to save Perl code of created serializer classes for future use. Example:
## in helper script
use Google::ProtocolBuffers;
Google::ProtocolBuffers->parse(
"message Foo {optional int32 a = 1; }",
{ generate_code => 'Foo.pm' }
);
## then, in production code
use Foo;
my $str = Foo->encode({a => 100});
create_accessors (Boolean)
If this option is set, then result of 'decode' will be a blessed structure with accessor methods for
each field, look at Class::Accessor for more info. Example:
use Google::ProtocolBuffers;
Google::ProtocolBuffers->parse(
"message Foo { optional int32 id = 1; }",
{ create_accessors => 1 }
);
my $foo = Foo->decode("\x{08}\x{02}");
print $foo->id; ## prints 2
$foo->id(100); ## now it is set to 100
follow_best_practice (Boolean)
This option is from Class::Accessor too; it has no effect without 'create_accessors'. If set, names
of getters (read accessors) will start with get_ and names of setter with set_:
use Google::ProtocolBuffers;
Google::ProtocolBuffers->parse(
"message Foo { optional int32 id = 1; }",
{ create_accessors => 1, follow_best_practice => 1 }
);
## Class::Accessor provides a constructor too
my $foo = Foo->new({ id => 2 });
print $foo->get_id;
$foo->set_id(100);
simple_extensions (Boolean)
If this option is set, then extensions are treated as if they were regular fields in messages or
groups:
use Google::ProtocolBuffers;
use Data::Dumper;
Google::ProtocolBuffers->parse(
"
message Foo {
optional int32 id = 1;
extensions 10 to max;
}
extend Foo {
optional string name = 10;
}
",
{ simple_extensions=>1, create_accessors => 1 }
);
my $foo = Foo->decode("\x{08}\x{02}R\x{03}Bob");
print Dumper $foo; ## { id => 2, name => 'Bob' }
print $foo->id, "\n";
$foo->name("Sponge Bob");
This option is off by default because extensions live in a separate namespace and may have the same
names as fields. Compilation of such proto with 'simple_extension' option will result in die. If the
option is off, you have to use special accessors for extension fields - setExtension and
getExtension, as in C++ Protocol Buffer API. Hash keys for extended fields in Plain Old Data
structures will be enclosed in brackets:
use Google::ProtocolBuffers;
use Data::Dumper;
Google::ProtocolBuffers->parse(
"
message Foo {
optional int32 id = 1;
extensions 10 to max;
}
extend Foo {
optional string id = 10; // <-- id again!
}
",
{ simple_extensions => 0, ## <-- no simple extensions
create_accessors => 1,
}
);
my $foo = Foo->decode("\x{08}\x{02}R\x{05}Kenny");
print Dumper $foo; ## { id => 2, '[id]' => 'Kenny' }
print $foo->id, "\n"; ## 2
print $foo->getExtension('id'), "\n"; ## Kenny
$foo->setExtension("id", 'Kenny McCormick');
no_camel_case (Boolean)
By default, names of created Perl classes are taken from "camel-cased" names of proto's packages,
messages, groups and enums. First characters are capitalized, all underscores are removed and the
characters following them are capitalized too. An example: a fully qualified name
'package_test.Message' will result in Perl class 'PackageTest::Message'. Option 'no_camel_case' turns
name-mangling off. Names of fields, extensions and enum constants are not affected anyway.
package_name (String)
Package name to be put into generated Perl code; has no effect on Perl classes names and has no
effect unless 'generate_code' is also set.
MessageClass->encode($hashref)
This method may be called as class or instance method. 'MessageClass' must already be created by
compiler. Input is a hash reference. Output is a scalar (string) with serialized data. Unknown fields
in hashref are ignored. In case of errors (e.g. required field is not set and there is no default value
for the required field) an exception is thrown. Examples:
use Google::ProtocolBuffers;
Google::ProtocolBuffers->parse(
"message Foo {optional int32 id = 1; }",
{create_accessors => 1}
);
my $string = Foo->encode({ id => 2 });
my $foo = Foo->new({ id => 2 });
$string = $foo->encode; ## ditto
MessageClass->decode($scalar)
Class method. Input: serialized data string. Output: data object of class 'MessageClass'. Unknown fields
in serialized data are ignored. In case of errors (e.g. message is broken or partial) or data string is
a wide-character (utf-8) string, an exception is thrown.
PROTO ELEMENTS
Enums
For each enum in proto, a Perl class will be constructed with constants for each enum value. You may
import these constants via ClassName->import(":constants") call. Please note that Perl compiler will know
nothing about these constants at compile time, because this import occurs at run time, so parenthesis
after constant's name are required.
use Google::ProtocolBuffers;
Google::ProtocolBuffers->parse(
"
enum Foo {
FOO = 1;
BAR = 2;
}
",
{ generate_code => 'Foo.pm' }
);
print Foo::FOO(), "\n"; ## fully quailified name is fine
Foo->import(":constants");
print FOO(), "\n"; ## now FOO is defined in our namespace
print FOO; ## <-- Error! FOO is bareword!
Or, do the import inside a BEGIN block:
use Foo; ## Foo.pm was generated in previous example
BEGIN { Foo->import(":constants") }
print FOO, "\n"; ## ok, Perl compiler knows about FOO here
Groups
Though group are considered deprecated they are supported by Google::ProtocolBuffers. They are like
nested messages, except that nested type definition and field definition go together:
use Google::ProtocolBuffers;
Google::ProtocolBuffers->parse(
"
message Foo {
optional group Bar = 1 {
optional int32 baz = 1;
}
}
",
{ create_accessors => 1 }
);
my $foo = Foo->new;
$foo->Bar( Foo::Bar->new({ baz => 2 }) );
print $foo->Bar->baz, ", ", $foo->{Bar}->{baz}, "\n"; # 2, 2
Default values
Proto file may specify a default value for a field. The default value is returned by accessor if there
is no value for field or if this value is undefined. The default value is not accessible via plain old
data hash, though. Default string values are always byte-strings, if you need wide-character (Unicode)
string, use "decode_utf8" in Encode.
use Google::ProtocolBuffers;
Google::ProtocolBuffers->parse(
"message Foo {optional string name=1 [default='Kenny'];} ",
{create_accessors => 1}
);
## no initial value
my $foo = Foo->new;
print $foo->name(), ", ", $foo->{name}, "\n"; # Kenny, (undef)
## some defined value
$foo->name('Ken');
print $foo->name(), ", ", $foo->{name}, "\n"; # Ken, Ken
## empty, but still defined value
$foo->name('');
print $foo->name(), ", ", $foo->{name}, "\n"; # (empty), (empty)
## undef value == default value
$foo->name(undef);
print $foo->name(), ", ", $foo->{name}, "\n"; # Kenny, (undef)
Extensions
From the point of view of serialized data, there is no difference if a field is declared as regular field
or if it is extension, as far as field number is the same. That is why there is an option
'simple_extensions' (see above) that treats extensions like regular fields. From the point of view of
named accessors, however, extensions live in namespace different from namespace of fields, that's why
they simple names (i.e. not fully qualified ones) may conflict. (And that's why this option is off by
default). The name of extensions are obtained from their fully qualified names from which leading part,
most common with the class name to be extended, is stripped. Names of hash keys enclosed in brackets;
arguments to methods 'getExtension' and 'setExtension' do not. Here is the self-explanatory example to
the rules:
use Google::ProtocolBuffers;
use Data::Dumper;
Google::ProtocolBuffers->parse(
"
package some_package;
// message Plugh contains one regular field and three extensions
message Plugh {
optional int32 foo = 1;
extensions 10 to max;
}
extend Plugh {
optional int32 bar = 10;
}
message Thud {
extend Plugh {
optional int32 baz = 11;
}
}
// Note: the official Google's proto compiler does not allow
// several package declarations in a file (as of version 2.0.1).
// To compile this example with the official protoc, put lines
// above to some other file, and import that file here.
package another_package;
// import 'other_file.proto';
extend some_package.Plugh {
optional int32 qux = 12;
}
",
{ create_accessors => 1 }
);
my $plugh = SomePackage::Plugh->decode(
"\x{08}\x{01}\x{50}\x{02}\x{58}\x{03}\x{60}\x{04}"
);
print Dumper $plugh;
## {foo=>1, '[bar]'=>2, '[Thud.baz]'=>3, [another_package.qux]=>4}
print $plugh->foo, "\n"; ## 1
print $plugh->getExtension('bar'), "\n"; ## 2
print $plugh->getExtension('Thud.baz'), "\n"; ## 3
print $plugh->getExtension('Thud::baz'), "\n"; ## ditto
Another point is that 'extend' block doesn't create new namespace or scope, so the following proto
declaration is invalid:
// proto:
package test;
message Foo { extensions 10 to max; }
message Bar { extensions 10 to max; }
extend Foo { optional int32 a = 10; }
extend Bar { optional int32 a = 20; } // <-- Error: name 'a' in package
// 'test' is already used!
Well, extensions are the most complicated part of proto syntax, and I hope that you either got it or you
don't need it.
RUN-TIME MESSAGE CREATION
You don't like to mess with proto files? Structure of your data is known at run-time only? No problem,
create your serializer classes at run-time too with method
Google::ProtocolBuffers->create_message('ClassName', \@fields, \%options); (Note: The order of field
description parts is the same as in proto file. The API is going to change to accept named parameters,
but backward compatibility will be preserved).
use Google::ProtocolBuffers;
use Google::ProtocolBuffers::Constants(qw/:labels :types/);
##
## proto:
## message Foo {
## message Bar {
## optional int32 a = 1 [default=12];
## }
## required int32 id = 1;
## repeated Bar bars = 2;
## }
##
Google::ProtocolBuffers->create_message(
'Foo::Bar',
[
## optional int32 a = 1 [default=12]
[LABEL_OPTIONAL, TYPE_INT32, 'a', 1, '12']
],
{ create_accessors => 1 }
);
Google::ProtocolBuffers->create_message(
'Foo',
[
[LABEL_REQUIRED, TYPE_INT32, 'id', 1],
[LABEL_REPEATED, 'Foo::Bar', 'bars', 2],
],
{ create_accessors => 1 }
);
my $foo = Foo->new({ id => 10 });
$foo->bars( Foo::Bar->new({a=>1}), Foo::Bar->new({a=>2}) );
print $foo->encode;
There are methods 'create_group' and 'create_enum' also; the following constants are exported: labels
(LABEL_OPTIONAL, LABEL_OPTIONAL, LABEL_REPEATED) and types (TYPE_INT32, TYPE_UINT32, TYPE_SINT32,
TYPE_FIXED32, TYPE_SFIXED32, TYPE_INT64, TYPE_UINT64, TYPE_SINT64, TYPE_FIXED64, TYPE_SFIXED64,
TYPE_BOOL, TYPE_STRING, TYPE_BYTES, TYPE_DOUBLE, TYPE_FLOAT).
KNOWN BUGS, LIMITATIONS AND TODOs
All proto options are ignored except default values for fields; extension numbers are not checked.
Unknown fields in serialized data are skipped, no stream API (encoding to/decoding from file handlers) is
present. Ask for what you need most.
Introspection API is planned.
Declarations of RPC services are currently ignored, but their support is planned (btw, which Perl RPC
implementation would you recommend?)
SEE ALSO
Official page of Google's Protocol Buffers project (<http://code.google.com/p/protobuf/>)
Protobuf-PerlXS project (<http://code.google.com/p/protobuf-perlxs/>) - creates XS wrapper for C++
classes generated by official Google's compiler protoc. You have to complile XS files every time you've
changed the proto description, however, this is the fastest way to work with Protocol Buffers from Perl.
Protobuf-Perl project <http://code.google.com/p/protobuf-perl/> - someday it may be part of official
Google's compiler.
Thrift <http://developers.facebook.com/thrift/>
ASN.1 <http://en.wikipedia.org/wiki/ASN.1>, JSON and YAML
AUTHOR, ACKNOWLEDGEMENS, COPYRIGHT
Author: Igor Gariev <gariev@hotmail.com>
the CSIRT Gadgets Foundation <csirtgadgets.org>
Proto grammar is based on work by Alek Storm
<http://groups.google.com/group/protobuf/browse_thread/thread/1cccfc624cd612da>
This library is free software; you can redistribute it and/or modify it under the same terms as Perl
itself, either Perl version 5.10.0 or, at your option, any later version of Perl 5 you may have
available.