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Comparing Types-Serialiser/Serialiser.pm (file contents):
Revision 1.2 by root, Sun Oct 27 20:01:08 2013 UTC vs.
Revision 1.4 by root, Mon Oct 28 15:28:44 2013 UTC

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15 15
16=cut 16=cut
17 17
18package Types::Serialiser; 18package Types::Serialiser;
19 19
20use common::sense; # required to suppress annoying warnings
21
20our $VERSION = 0.01; 22our $VERSION = 0.02;
21 23
22=head1 SIMPLE SCALAR CONSTANTS 24=head1 SIMPLE SCALAR CONSTANTS
23 25
24Simple scalar constants are values that are overloaded to act like simple 26Simple scalar constants are values that are overloaded to act like simple
25Perl values, but have (class) type to differentiate them from normal Perl 27Perl values, but have (class) type to differentiate them from normal Perl
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95 97
96=back 98=back
97 99
98=cut 100=cut
99 101
102BEGIN {
103 # for historical reasons, and to avoid extra dependencies in JSON::PP,
104 # we alias *Types::Serialiser::Boolean with JSON::PP::Boolean.
105 package JSON::PP::Boolean;
106 *Types::Serialiser::Boolean:: = *JSON::PP::Boolean::;
107}
108
100our $true = do { bless \(my $dummy = 1), Types::Serialiser::Boolean:: }; 109our $true = do { bless \(my $dummy = 1), Types::Serialiser::Boolean:: };
101our $false = do { bless \(my $dummy = 0), Types::Serialiser::Boolean:: }; 110our $false = do { bless \(my $dummy = 0), Types::Serialiser::Boolean:: };
102our $error = do { bless \(my $dummy ), Types::Serialiser::Error:: }; 111our $error = do { bless \(my $dummy ), Types::Serialiser::Error:: };
103 112
104sub true () { $true } 113sub true () { $true }
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108sub is_bool ($) { UNIVERSAL::isa $_[0], Types::Serialiser::Boolean:: } 117sub is_bool ($) { UNIVERSAL::isa $_[0], Types::Serialiser::Boolean:: }
109sub is_true ($) { $_[0] && UNIVERSAL::isa $_[0], Types::Serialiser::Boolean:: } 118sub is_true ($) { $_[0] && UNIVERSAL::isa $_[0], Types::Serialiser::Boolean:: }
110sub is_false ($) { !$_[0] && UNIVERSAL::isa $_[0], Types::Serialiser::Boolean:: } 119sub is_false ($) { !$_[0] && UNIVERSAL::isa $_[0], Types::Serialiser::Boolean:: }
111sub is_error ($) { UNIVERSAL::isa $_[0], Types::Serialiser::Error:: } 120sub is_error ($) { UNIVERSAL::isa $_[0], Types::Serialiser::Error:: }
112 121
113package Types::Serialiser::Boolean; 122package Types::Serialiser::BooleanBase;
114 123
115use overload 124use overload
116 "0+" => sub { ${$_[0]} }, 125 "0+" => sub { ${$_[0]} },
117 "++" => sub { $_[0] = ${$_[0]} + 1 }, 126 "++" => sub { $_[0] = ${$_[0]} + 1 },
118 "--" => sub { $_[0] = ${$_[0]} - 1 }, 127 "--" => sub { $_[0] = ${$_[0]} - 1 },
119 fallback => 1; 128 fallback => 1;
120 129
130@Types::Serialiser::Boolean::ISA = Types::Serialiser::BooleanBase::;
131
121package Types::Serialiser::Error; 132package Types::Serialiser::Error;
122 133
123sub error { 134sub error {
124 require Carp; 135 require Carp;
125 Carp::croak ("caught attempt to use the Types::Serialiser::error value"); 136 Carp::croak ("caught attempt to use the Types::Serialiser::error value");
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139see if it's C<1> (true), C<0> (false) or C<undef> (error). 150see if it's C<1> (true), C<0> (false) or C<undef> (error).
140 151
141While it is possible to use an isa test, directly comparing stash pointers 152While it is possible to use an isa test, directly comparing stash pointers
142is faster and guaranteed to work. 153is faster and guaranteed to work.
143 154
155For historical reasons, the C<Types::Serialiser::Boolean> stash is
156just an alias for C<JSON::PP::Boolean>. When printed, the classname
157withh usually be C<JSON::PP::Boolean>, but isa tests and stash pointer
158comparison will normally work correctly (i.e. Types::Serialiser::true ISA
159JSON::PP::Boolean, but also ISA Types::Serialiser::Boolean).
160
161=head1 A GENERIC OBJECT SERIALIATION PROTOCOL
162
163This section explains the object serialisation protocol used by
164L<CBOR::XS>. It is meant to be generic enough to support any kind of
165generic object serialiser.
166
167This protocol is called "the Types::Serialiser object serialisation
168protocol".
169
170=head2 ENCODING
171
172When the encoder encounters an object that it cannot otherwise encode (for
173example, L<CBOR::XS> can encode a few special types itself, and will first
174attempt to use the special C<TO_CBOR> serialisation protocol), it will
175look up the C<FREEZE> method on the object.
176
177If it exists, it will call it with two arguments: the object to
178serialise, and a constant string that indicates the name of the
179serialisationformat. For example L<CBOR::XS> uses C<CBOR>, and L<JSON> and
180L<JSON::XS> (or any other JSON serialiser), would use C<JSON> as second
181argument.
182
183The C<FREEZE> method can then return zero or more values to identify the
184object instance. The serialiser is then supposed to encode the class name
185and all of these return values (which must be encodable in the format)
186using the relevant form for perl objects. In CBOR for example, there is a
187registered tag number for encoded perl objects.
188
189=head2 DECODING
190
191When the decoder then encounters such an encoded perl object, it should
192look up the C<THAW> method on the stored classname, and invoke it with the
193classname, the constant string to identify the format, and all the return
194values returned by C<FREEZE>.
195
196=head2 EXAMPLES
197
198See the C<OBJECT SERIALISATION> section in the L<CBOR::XS> manpage for
199more details, an example implementation, and code examples.
200
201Here is an example C<FREEZE>/C<THAW> method pair:
202
203 sub My::Object::FREEZE {
204 my ($self, $serialiser) = @_;
205
206 ($self->{type}, $self->{id}, $self->{variant})
207 }
208
209 sub My::Object::THAW {
210 my ($class, $serialiser, $type, $id, $variant) = @_;
211
212 $class-<new (type => $type, id => $id, variant => $variant)
213 }
214
144=head1 BUGS 215=head1 BUGS
145 216
146The use of L<overload> makes this module much heavier than it should be 217The use of L<overload> makes this module much heavier than it should be
147(on my system, this module: 4kB RSS, overload: 260kB RSS). 218(on my system, this module: 4kB RSS, overload: 260kB RSS).
148 219

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