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1.1 |
=head1 NAME |
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CBOR::XS - Concise Binary Object Representation (CBOR, RFC7049) |
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=encoding utf-8 |
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=head1 SYNOPSIS |
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use CBOR::XS; |
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$binary_cbor_data = encode_cbor $perl_value; |
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$perl_value = decode_cbor $binary_cbor_data; |
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# OO-interface |
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$coder = CBOR::XS->new; |
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1.6 |
$binary_cbor_data = $coder->encode ($perl_value); |
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$perl_value = $coder->decode ($binary_cbor_data); |
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# prefix decoding |
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my $many_cbor_strings = ...; |
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while (length $many_cbor_strings) { |
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my ($data, $length) = $cbor->decode_prefix ($many_cbor_strings); |
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# data was decoded |
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substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string |
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} |
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1.1 |
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=head1 DESCRIPTION |
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1.5 |
This module converts Perl data structures to the Concise Binary Object |
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Representation (CBOR) and vice versa. CBOR is a fast binary serialisation |
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1.28 |
format that aims to use an (almost) superset of the JSON data model, i.e. |
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when you can represent something useful in JSON, you should be able to |
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represent it in CBOR. |
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1.1 |
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1.28 |
In short, CBOR is a faster and quite compact binary alternative to JSON, |
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1.10 |
with the added ability of supporting serialisation of Perl objects. (JSON |
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often compresses better than CBOR though, so if you plan to compress the |
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1.28 |
data later and speed is less important you might want to compare both |
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formats first). |
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1.5 |
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1.68 |
The primary goal of this module is to be I<correct> and the secondary goal |
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is to be I<fast>. To reach the latter goal it was written in C. |
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1.15 |
To give you a general idea about speed, with texts in the megabyte range, |
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C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or |
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L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the |
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data, the worse L<Storable> performs in comparison. |
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1.28 |
Regarding compactness, C<CBOR::XS>-encoded data structures are usually |
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about 20% smaller than the same data encoded as (compact) JSON or |
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L<Storable>. |
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In addition to the core CBOR data format, this module implements a |
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1.31 |
number of extensions, to support cyclic and shared data structures |
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(see C<allow_sharing> and C<allow_cycles>), string deduplication (see |
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C<pack_strings>) and scalar references (always enabled). |
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1.21 |
|
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1.1 |
See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
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vice versa. |
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=cut |
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package CBOR::XS; |
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use common::sense; |
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1.67 |
our $VERSION = 1.71; |
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1.1 |
our @ISA = qw(Exporter); |
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our @EXPORT = qw(encode_cbor decode_cbor); |
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use Exporter; |
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use XSLoader; |
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1.6 |
use Types::Serialiser; |
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1.3 |
our $MAGIC = "\xd9\xd9\xf7"; |
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1.1 |
=head1 FUNCTIONAL INTERFACE |
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The following convenience methods are provided by this module. They are |
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exported by default: |
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=over 4 |
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=item $cbor_data = encode_cbor $perl_scalar |
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Converts the given Perl data structure to CBOR representation. Croaks on |
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error. |
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=item $perl_scalar = decode_cbor $cbor_data |
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The opposite of C<encode_cbor>: expects a valid CBOR string to parse, |
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returning the resulting perl scalar. Croaks on error. |
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=back |
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=head1 OBJECT-ORIENTED INTERFACE |
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The object oriented interface lets you configure your own encoding or |
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decoding style, within the limits of supported formats. |
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=over 4 |
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=item $cbor = new CBOR::XS |
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Creates a new CBOR::XS object that can be used to de/encode CBOR |
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strings. All boolean flags described below are by default I<disabled>. |
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The mutators for flags all return the CBOR object again and thus calls can |
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be chained: |
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my $cbor = CBOR::XS->new->encode ({a => [1,2]}); |
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1.65 |
=item $cbor = new_safe CBOR::XS |
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Create a new, safe/secure CBOR::XS object. This is similar to C<new>, |
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but configures the coder object to be safe to use with untrusted |
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data. Currently, this is equivalent to: |
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my $cbor = CBOR::XS |
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->new |
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->forbid_objects |
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->filter (\&CBOR::XS::safe_filter) |
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->max_size (1e8); |
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But is more future proof (it is better to crash because of a change than |
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to be exploited in other ways). |
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=cut |
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sub new_safe { |
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CBOR::XS |
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->new |
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->forbid_objects |
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->filter (\&CBOR::XS::safe_filter) |
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->max_size (1e8) |
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} |
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1.1 |
=item $cbor = $cbor->max_depth ([$maximum_nesting_depth]) |
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=item $max_depth = $cbor->get_max_depth |
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Sets the maximum nesting level (default C<512>) accepted while encoding |
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or decoding. If a higher nesting level is detected in CBOR data or a Perl |
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data structure, then the encoder and decoder will stop and croak at that |
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point. |
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Nesting level is defined by number of hash- or arrayrefs that the encoder |
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needs to traverse to reach a given point or the number of C<{> or C<[> |
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characters without their matching closing parenthesis crossed to reach a |
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given character in a string. |
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Setting the maximum depth to one disallows any nesting, so that ensures |
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that the object is only a single hash/object or array. |
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If no argument is given, the highest possible setting will be used, which |
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is rarely useful. |
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Note that nesting is implemented by recursion in C. The default value has |
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been chosen to be as large as typical operating systems allow without |
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crashing. |
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1.65 |
See L<SECURITY CONSIDERATIONS>, below, for more info on why this is useful. |
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1.1 |
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=item $cbor = $cbor->max_size ([$maximum_string_size]) |
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=item $max_size = $cbor->get_max_size |
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Set the maximum length a CBOR string may have (in bytes) where decoding |
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is being attempted. The default is C<0>, meaning no limit. When C<decode> |
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is called on a string that is longer then this many bytes, it will not |
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attempt to decode the string but throw an exception. This setting has no |
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effect on C<encode> (yet). |
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If no argument is given, the limit check will be deactivated (same as when |
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C<0> is specified). |
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1.65 |
See L<SECURITY CONSIDERATIONS>, below, for more info on why this is useful. |
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1.1 |
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1.19 |
=item $cbor = $cbor->allow_unknown ([$enable]) |
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=item $enabled = $cbor->get_allow_unknown |
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If C<$enable> is true (or missing), then C<encode> will I<not> throw an |
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exception when it encounters values it cannot represent in CBOR (for |
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example, filehandles) but instead will encode a CBOR C<error> value. |
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If C<$enable> is false (the default), then C<encode> will throw an |
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exception when it encounters anything it cannot encode as CBOR. |
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This option does not affect C<decode> in any way, and it is recommended to |
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leave it off unless you know your communications partner. |
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1.20 |
=item $cbor = $cbor->allow_sharing ([$enable]) |
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1.19 |
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1.20 |
=item $enabled = $cbor->get_allow_sharing |
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1.19 |
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If C<$enable> is true (or missing), then C<encode> will not double-encode |
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1.20 |
values that have been referenced before (e.g. when the same object, such |
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as an array, is referenced multiple times), but instead will emit a |
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reference to the earlier value. |
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1.19 |
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This means that such values will only be encoded once, and will not result |
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in a deep cloning of the value on decode, in decoders supporting the value |
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1.25 |
sharing extension. This also makes it possible to encode cyclic data |
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1.62 |
structures (which need C<allow_cycles> to be enabled to be decoded by this |
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1.31 |
module). |
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1.19 |
|
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1.21 |
It is recommended to leave it off unless you know your |
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communication partner supports the value sharing extensions to CBOR |
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1.26 |
(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the |
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1.25 |
resulting data structure might be unusable. |
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1.21 |
|
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1.19 |
Detecting shared values incurs a runtime overhead when values are encoded |
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that have a reference counter large than one, and might unnecessarily |
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increase the encoded size, as potentially shared values are encode as |
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1.31 |
shareable whether or not they are actually shared. |
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1.19 |
|
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1.20 |
At the moment, only targets of references can be shared (e.g. scalars, |
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arrays or hashes pointed to by a reference). Weirder constructs, such as |
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an array with multiple "copies" of the I<same> string, which are hard but |
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not impossible to create in Perl, are not supported (this is the same as |
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1.25 |
with L<Storable>). |
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1.19 |
|
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1.25 |
If C<$enable> is false (the default), then C<encode> will encode shared |
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data structures repeatedly, unsharing them in the process. Cyclic data |
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structures cannot be encoded in this mode. |
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1.19 |
|
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This option does not affect C<decode> in any way - shared values and |
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1.21 |
references will always be decoded properly if present. |
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1.31 |
=item $cbor = $cbor->allow_cycles ([$enable]) |
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=item $enabled = $cbor->get_allow_cycles |
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If C<$enable> is true (or missing), then C<decode> will happily decode |
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self-referential (cyclic) data structures. By default these will not be |
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decoded, as they need manual cleanup to avoid memory leaks, so code that |
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isn't prepared for this will not leak memory. |
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If C<$enable> is false (the default), then C<decode> will throw an error |
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when it encounters a self-referential/cyclic data structure. |
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1.41 |
FUTURE DIRECTION: the motivation behind this option is to avoid I<real> |
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cycles - future versions of this module might chose to decode cyclic data |
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structures using weak references when this option is off, instead of |
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throwing an error. |
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1.31 |
This option does not affect C<encode> in any way - shared values and |
254 |
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1.42 |
references will always be encoded properly if present. |
255 |
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1.31 |
|
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1.65 |
=item $cbor = $cbor->forbid_objects ([$enable]) |
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=item $enabled = $cbor->get_forbid_objects |
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Disables the use of the object serialiser protocol. |
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If C<$enable> is true (or missing), then C<encode> will will throw an |
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exception when it encounters perl objects that would be encoded using the |
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perl-object tag (26). When C<decode> encounters such tags, it will fall |
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back to the general filter/tagged logic as if this were an unknown tag (by |
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default resulting in a C<CBOR::XC::Tagged> object). |
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If C<$enable> is false (the default), then C<encode> will use the |
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L<Types::Serialiser> object serialisation protocol to serialise objects |
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into perl-object tags, and C<decode> will do the same to decode such tags. |
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See L<SECURITY CONSIDERATIONS>, below, for more info on why forbidding this |
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protocol can be useful. |
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1.25 |
=item $cbor = $cbor->pack_strings ([$enable]) |
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1.21 |
|
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1.25 |
=item $enabled = $cbor->get_pack_strings |
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1.21 |
|
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If C<$enable> is true (or missing), then C<encode> will try not to encode |
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the same string twice, but will instead encode a reference to the string |
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1.25 |
instead. Depending on your data format, this can save a lot of space, but |
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1.21 |
also results in a very large runtime overhead (expect encoding times to be |
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2-4 times as high as without). |
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It is recommended to leave it off unless you know your |
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communications partner supports the stringref extension to CBOR |
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1.26 |
(L<http://cbor.schmorp.de/stringref>), as without decoder support, the |
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1.25 |
resulting data structure might not be usable. |
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1.21 |
|
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1.25 |
If C<$enable> is false (the default), then C<encode> will encode strings |
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the standard CBOR way. |
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1.21 |
|
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This option does not affect C<decode> in any way - string references will |
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always be decoded properly if present. |
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1.19 |
|
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1.52 |
=item $cbor = $cbor->text_keys ([$enable]) |
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298 |
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=item $enabled = $cbor->get_text_keys |
299 |
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300 |
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If C<$enabled> is true (or missing), then C<encode> will encode all |
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perl hash keys as CBOR text strings/UTF-8 string, upgrading them as needed. |
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If C<$enable> is false (the default), then C<encode> will encode hash keys |
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normally - upgraded perl strings (strings internally encoded as UTF-8) as |
305 |
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CBOR text strings, and downgraded perl strings as CBOR byte strings. |
306 |
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|
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This option does not affect C<decode> in any way. |
308 |
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|
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This option is useful for interoperability with CBOR decoders that don't |
310 |
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treat byte strings as a form of text. It is especially useful as Perl |
311 |
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gives very little control over hash keys. |
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Enabling this option can be slow, as all downgraded hash keys that are |
314 |
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encoded need to be scanned and converted to UTF-8. |
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316 |
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=item $cbor = $cbor->text_strings ([$enable]) |
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318 |
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=item $enabled = $cbor->get_text_strings |
319 |
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|
320 |
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This option works similar to C<text_keys>, above, but works on all strings |
321 |
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(including hash keys), so C<text_keys> has no further effect after |
322 |
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enabling C<text_strings>. |
323 |
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If C<$enabled> is true (or missing), then C<encode> will encode all perl |
325 |
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strings as CBOR text strings/UTF-8 strings, upgrading them as needed. |
326 |
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|
327 |
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If C<$enable> is false (the default), then C<encode> will encode strings |
328 |
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normally (but see C<text_keys>) - upgraded perl strings (strings |
329 |
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internally encoded as UTF-8) as CBOR text strings, and downgraded perl |
330 |
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strings as CBOR byte strings. |
331 |
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|
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This option does not affect C<decode> in any way. |
333 |
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|
334 |
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This option has similar advantages and disadvantages as C<text_keys>. In |
335 |
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addition, this option effectively removes the ability to encode byte |
336 |
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strings, which might break some C<FREEZE> and C<TO_CBOR> methods that rely |
337 |
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on this, such as bignum encoding, so this option is mainly useful for very |
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simple data. |
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|
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1.33 |
=item $cbor = $cbor->validate_utf8 ([$enable]) |
341 |
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342 |
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=item $enabled = $cbor->get_validate_utf8 |
343 |
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344 |
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If C<$enable> is true (or missing), then C<decode> will validate that |
345 |
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elements (text strings) containing UTF-8 data in fact contain valid UTF-8 |
346 |
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data (instead of blindly accepting it). This validation obviously takes |
347 |
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extra time during decoding. |
348 |
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349 |
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The concept of "valid UTF-8" used is perl's concept, which is a superset |
350 |
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of the official UTF-8. |
351 |
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352 |
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If C<$enable> is false (the default), then C<decode> will blindly accept |
353 |
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UTF-8 data, marking them as valid UTF-8 in the resulting data structure |
354 |
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1.51 |
regardless of whether that's true or not. |
355 |
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1.33 |
|
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Perl isn't too happy about corrupted UTF-8 in strings, but should |
357 |
|
|
generally not crash or do similarly evil things. Extensions might be not |
358 |
|
|
so forgiving, so it's recommended to turn on this setting if you receive |
359 |
|
|
untrusted CBOR. |
360 |
|
|
|
361 |
|
|
This option does not affect C<encode> in any way - strings that are |
362 |
|
|
supposedly valid UTF-8 will simply be dumped into the resulting CBOR |
363 |
|
|
string without checking whether that is, in fact, true or not. |
364 |
|
|
|
365 |
root |
1.23 |
=item $cbor = $cbor->filter ([$cb->($tag, $value)]) |
366 |
|
|
|
367 |
|
|
=item $cb_or_undef = $cbor->get_filter |
368 |
|
|
|
369 |
root |
1.24 |
Sets or replaces the tagged value decoding filter (when C<$cb> is |
370 |
|
|
specified) or clears the filter (if no argument or C<undef> is provided). |
371 |
|
|
|
372 |
|
|
The filter callback is called only during decoding, when a non-enforced |
373 |
|
|
tagged value has been decoded (see L<TAG HANDLING AND EXTENSIONS> for a |
374 |
|
|
list of enforced tags). For specific tags, it's often better to provide a |
375 |
|
|
default converter using the C<%CBOR::XS::FILTER> hash (see below). |
376 |
|
|
|
377 |
|
|
The first argument is the numerical tag, the second is the (decoded) value |
378 |
|
|
that has been tagged. |
379 |
|
|
|
380 |
|
|
The filter function should return either exactly one value, which will |
381 |
|
|
replace the tagged value in the decoded data structure, or no values, |
382 |
|
|
which will result in default handling, which currently means the decoder |
383 |
|
|
creates a C<CBOR::XS::Tagged> object to hold the tag and the value. |
384 |
|
|
|
385 |
|
|
When the filter is cleared (the default state), the default filter |
386 |
root |
1.65 |
function, C<CBOR::XS::default_filter>, is used. This function simply |
387 |
|
|
looks up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists |
388 |
|
|
it must be a code reference that is called with tag and value, and is |
389 |
|
|
responsible for decoding the value. If no entry exists, it returns no |
390 |
|
|
values. C<CBOR::XS> provides a number of default filter functions already, |
391 |
|
|
the the C<%CBOR::XS::FILTER> hash can be freely extended with more. |
392 |
|
|
|
393 |
|
|
C<CBOR::XS> additionally provides an alternative filter function that is |
394 |
|
|
supposed to be safe to use with untrusted data (which the default filter |
395 |
|
|
might not), called C<CBOR::XS::safe_filter>, which works the same as |
396 |
|
|
the C<default_filter> but uses the C<%CBOR::XS::SAFE_FILTER> variable |
397 |
|
|
instead. It is prepopulated with the tag decoding functions that are |
398 |
|
|
deemed safe (basically the same as C<%CBOR::XS::FILTER> without all |
399 |
|
|
the bignum tags), and can be extended by user code as wlel, although, |
400 |
|
|
obviously, one should be very careful about adding decoding functions |
401 |
|
|
here, since the expectation is that they are safe to use on untrusted |
402 |
|
|
data, after all. |
403 |
root |
1.24 |
|
404 |
root |
1.28 |
Example: decode all tags not handled internally into C<CBOR::XS::Tagged> |
405 |
root |
1.24 |
objects, with no other special handling (useful when working with |
406 |
|
|
potentially "unsafe" CBOR data). |
407 |
|
|
|
408 |
|
|
CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
409 |
|
|
|
410 |
|
|
Example: provide a global filter for tag 1347375694, converting the value |
411 |
|
|
into some string form. |
412 |
|
|
|
413 |
|
|
$CBOR::XS::FILTER{1347375694} = sub { |
414 |
|
|
my ($tag, $value); |
415 |
|
|
|
416 |
|
|
"tag 1347375694 value $value" |
417 |
|
|
}; |
418 |
root |
1.23 |
|
419 |
root |
1.65 |
Example: provide your own filter function that looks up tags in your own |
420 |
|
|
hash: |
421 |
|
|
|
422 |
|
|
my %my_filter = ( |
423 |
|
|
998347484 => sub { |
424 |
|
|
my ($tag, $value); |
425 |
|
|
|
426 |
|
|
"tag 998347484 value $value" |
427 |
|
|
}; |
428 |
|
|
); |
429 |
|
|
|
430 |
|
|
my $coder = CBOR::XS->new->filter (sub { |
431 |
|
|
&{ $my_filter{$_[0]} or return } |
432 |
|
|
}); |
433 |
|
|
|
434 |
|
|
|
435 |
|
|
Example: use the safe filter function (see L<SECURITY CONSIDERATIONS> for |
436 |
|
|
more considerations on security). |
437 |
|
|
|
438 |
|
|
CBOR::XS->new->filter (\&CBOR::XS::safe_filter)->decode ($cbor_data); |
439 |
|
|
|
440 |
root |
1.1 |
=item $cbor_data = $cbor->encode ($perl_scalar) |
441 |
|
|
|
442 |
|
|
Converts the given Perl data structure (a scalar value) to its CBOR |
443 |
|
|
representation. |
444 |
|
|
|
445 |
|
|
=item $perl_scalar = $cbor->decode ($cbor_data) |
446 |
|
|
|
447 |
|
|
The opposite of C<encode>: expects CBOR data and tries to parse it, |
448 |
|
|
returning the resulting simple scalar or reference. Croaks on error. |
449 |
|
|
|
450 |
|
|
=item ($perl_scalar, $octets) = $cbor->decode_prefix ($cbor_data) |
451 |
|
|
|
452 |
|
|
This works like the C<decode> method, but instead of raising an exception |
453 |
|
|
when there is trailing garbage after the CBOR string, it will silently |
454 |
|
|
stop parsing there and return the number of characters consumed so far. |
455 |
|
|
|
456 |
|
|
This is useful if your CBOR texts are not delimited by an outer protocol |
457 |
|
|
and you need to know where the first CBOR string ends amd the next one |
458 |
|
|
starts. |
459 |
|
|
|
460 |
|
|
CBOR::XS->new->decode_prefix ("......") |
461 |
|
|
=> ("...", 3) |
462 |
|
|
|
463 |
|
|
=back |
464 |
|
|
|
465 |
root |
1.39 |
=head2 INCREMENTAL PARSING |
466 |
|
|
|
467 |
|
|
In some cases, there is the need for incremental parsing of JSON |
468 |
|
|
texts. While this module always has to keep both CBOR text and resulting |
469 |
|
|
Perl data structure in memory at one time, it does allow you to parse a |
470 |
|
|
CBOR stream incrementally, using a similar to using "decode_prefix" to see |
471 |
|
|
if a full CBOR object is available, but is much more efficient. |
472 |
|
|
|
473 |
|
|
It basically works by parsing as much of a CBOR string as possible - if |
474 |
|
|
the CBOR data is not complete yet, the pasrer will remember where it was, |
475 |
|
|
to be able to restart when more data has been accumulated. Once enough |
476 |
|
|
data is available to either decode a complete CBOR value or raise an |
477 |
|
|
error, a real decode will be attempted. |
478 |
|
|
|
479 |
|
|
A typical use case would be a network protocol that consists of sending |
480 |
|
|
and receiving CBOR-encoded messages. The solution that works with CBOR and |
481 |
|
|
about anything else is by prepending a length to every CBOR value, so the |
482 |
|
|
receiver knows how many octets to read. More compact (and slightly slower) |
483 |
|
|
would be to just send CBOR values back-to-back, as C<CBOR::XS> knows where |
484 |
|
|
a CBOR value ends, and doesn't need an explicit length. |
485 |
|
|
|
486 |
|
|
The following methods help with this: |
487 |
|
|
|
488 |
|
|
=over 4 |
489 |
|
|
|
490 |
|
|
=item @decoded = $cbor->incr_parse ($buffer) |
491 |
|
|
|
492 |
|
|
This method attempts to decode exactly one CBOR value from the beginning |
493 |
|
|
of the given C<$buffer>. The value is removed from the C<$buffer> on |
494 |
|
|
success. When C<$buffer> doesn't contain a complete value yet, it returns |
495 |
|
|
nothing. Finally, when the C<$buffer> doesn't start with something |
496 |
|
|
that could ever be a valid CBOR value, it raises an exception, just as |
497 |
|
|
C<decode> would. In the latter case the decoder state is undefined and |
498 |
|
|
must be reset before being able to parse further. |
499 |
|
|
|
500 |
|
|
This method modifies the C<$buffer> in place. When no CBOR value can be |
501 |
|
|
decoded, the decoder stores the current string offset. On the next call, |
502 |
|
|
continues decoding at the place where it stopped before. For this to make |
503 |
|
|
sense, the C<$buffer> must begin with the same octets as on previous |
504 |
|
|
unsuccessful calls. |
505 |
|
|
|
506 |
|
|
You can call this method in scalar context, in which case it either |
507 |
|
|
returns a decoded value or C<undef>. This makes it impossible to |
508 |
|
|
distinguish between CBOR null values (which decode to C<undef>) and an |
509 |
|
|
unsuccessful decode, which is often acceptable. |
510 |
|
|
|
511 |
|
|
=item @decoded = $cbor->incr_parse_multiple ($buffer) |
512 |
|
|
|
513 |
|
|
Same as C<incr_parse>, but attempts to decode as many CBOR values as |
514 |
|
|
possible in one go, instead of at most one. Calls to C<incr_parse> and |
515 |
|
|
C<incr_parse_multiple> can be interleaved. |
516 |
|
|
|
517 |
|
|
=item $cbor->incr_reset |
518 |
|
|
|
519 |
|
|
Resets the incremental decoder. This throws away any saved state, so that |
520 |
|
|
subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse |
521 |
|
|
a new CBOR value from the beginning of the C<$buffer> again. |
522 |
|
|
|
523 |
root |
1.61 |
This method can be called at any time, but it I<must> be called if you want |
524 |
root |
1.39 |
to change your C<$buffer> or there was a decoding error and you want to |
525 |
|
|
reuse the C<$cbor> object for future incremental parsings. |
526 |
|
|
|
527 |
|
|
=back |
528 |
|
|
|
529 |
root |
1.1 |
|
530 |
|
|
=head1 MAPPING |
531 |
|
|
|
532 |
|
|
This section describes how CBOR::XS maps Perl values to CBOR values and |
533 |
|
|
vice versa. These mappings are designed to "do the right thing" in most |
534 |
|
|
circumstances automatically, preserving round-tripping characteristics |
535 |
|
|
(what you put in comes out as something equivalent). |
536 |
|
|
|
537 |
|
|
For the more enlightened: note that in the following descriptions, |
538 |
|
|
lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl> |
539 |
|
|
refers to the abstract Perl language itself. |
540 |
|
|
|
541 |
|
|
|
542 |
|
|
=head2 CBOR -> PERL |
543 |
|
|
|
544 |
|
|
=over 4 |
545 |
|
|
|
546 |
root |
1.4 |
=item integers |
547 |
|
|
|
548 |
|
|
CBOR integers become (numeric) perl scalars. On perls without 64 bit |
549 |
|
|
support, 64 bit integers will be truncated or otherwise corrupted. |
550 |
|
|
|
551 |
|
|
=item byte strings |
552 |
|
|
|
553 |
root |
1.27 |
Byte strings will become octet strings in Perl (the Byte values 0..255 |
554 |
root |
1.4 |
will simply become characters of the same value in Perl). |
555 |
|
|
|
556 |
|
|
=item UTF-8 strings |
557 |
|
|
|
558 |
|
|
UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
559 |
|
|
decoded into proper Unicode code points. At the moment, the validity of |
560 |
|
|
the UTF-8 octets will not be validated - corrupt input will result in |
561 |
|
|
corrupted Perl strings. |
562 |
|
|
|
563 |
|
|
=item arrays, maps |
564 |
|
|
|
565 |
|
|
CBOR arrays and CBOR maps will be converted into references to a Perl |
566 |
|
|
array or hash, respectively. The keys of the map will be stringified |
567 |
|
|
during this process. |
568 |
|
|
|
569 |
root |
1.6 |
=item null |
570 |
|
|
|
571 |
|
|
CBOR null becomes C<undef> in Perl. |
572 |
|
|
|
573 |
|
|
=item true, false, undefined |
574 |
root |
1.1 |
|
575 |
root |
1.6 |
These CBOR values become C<Types:Serialiser::true>, |
576 |
|
|
C<Types:Serialiser::false> and C<Types::Serialiser::error>, |
577 |
root |
1.1 |
respectively. They are overloaded to act almost exactly like the numbers |
578 |
root |
1.6 |
C<1> and C<0> (for true and false) or to throw an exception on access (for |
579 |
|
|
error). See the L<Types::Serialiser> manpage for details. |
580 |
|
|
|
581 |
root |
1.23 |
=item tagged values |
582 |
root |
1.1 |
|
583 |
root |
1.23 |
Tagged items consists of a numeric tag and another CBOR value. |
584 |
root |
1.4 |
|
585 |
root |
1.23 |
See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >> |
586 |
root |
1.28 |
for details on which tags are handled how. |
587 |
root |
1.4 |
|
588 |
|
|
=item anything else |
589 |
|
|
|
590 |
|
|
Anything else (e.g. unsupported simple values) will raise a decoding |
591 |
|
|
error. |
592 |
root |
1.1 |
|
593 |
|
|
=back |
594 |
|
|
|
595 |
|
|
|
596 |
|
|
=head2 PERL -> CBOR |
597 |
|
|
|
598 |
|
|
The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
599 |
root |
1.28 |
typeless language. That means this module can only guess which CBOR type |
600 |
|
|
is meant by a perl value. |
601 |
root |
1.1 |
|
602 |
|
|
=over 4 |
603 |
|
|
|
604 |
|
|
=item hash references |
605 |
|
|
|
606 |
root |
1.4 |
Perl hash references become CBOR maps. As there is no inherent ordering in |
607 |
|
|
hash keys (or CBOR maps), they will usually be encoded in a pseudo-random |
608 |
root |
1.49 |
order. This order can be different each time a hash is encoded. |
609 |
root |
1.4 |
|
610 |
|
|
Currently, tied hashes will use the indefinite-length format, while normal |
611 |
|
|
hashes will use the fixed-length format. |
612 |
root |
1.1 |
|
613 |
|
|
=item array references |
614 |
|
|
|
615 |
root |
1.4 |
Perl array references become fixed-length CBOR arrays. |
616 |
root |
1.1 |
|
617 |
|
|
=item other references |
618 |
|
|
|
619 |
root |
1.28 |
Other unblessed references will be represented using |
620 |
|
|
the indirection tag extension (tag value C<22098>, |
621 |
|
|
L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed |
622 |
|
|
to be able to decode these values somehow, by either "doing the right |
623 |
|
|
thing", decoding into a generic tagged object, simply ignoring the tag, or |
624 |
|
|
something else. |
625 |
root |
1.4 |
|
626 |
|
|
=item CBOR::XS::Tagged objects |
627 |
|
|
|
628 |
|
|
Objects of this type must be arrays consisting of a single C<[tag, value]> |
629 |
root |
1.13 |
pair. The (numerical) tag will be encoded as a CBOR tag, the value will |
630 |
root |
1.28 |
be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to |
631 |
root |
1.13 |
create such objects. |
632 |
root |
1.1 |
|
633 |
root |
1.6 |
=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error |
634 |
root |
1.1 |
|
635 |
root |
1.6 |
These special values become CBOR true, CBOR false and CBOR undefined |
636 |
|
|
values, respectively. You can also use C<\1>, C<\0> and C<\undef> directly |
637 |
|
|
if you want. |
638 |
root |
1.1 |
|
639 |
root |
1.7 |
=item other blessed objects |
640 |
root |
1.1 |
|
641 |
root |
1.7 |
Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See |
642 |
root |
1.23 |
L<TAG HANDLING AND EXTENSIONS> for specific classes handled by this |
643 |
|
|
module, and L<OBJECT SERIALISATION> for generic object serialisation. |
644 |
root |
1.1 |
|
645 |
|
|
=item simple scalars |
646 |
|
|
|
647 |
|
|
Simple Perl scalars (any scalar that is not a reference) are the most |
648 |
|
|
difficult objects to encode: CBOR::XS will encode undefined scalars as |
649 |
root |
1.4 |
CBOR null values, scalars that have last been used in a string context |
650 |
root |
1.1 |
before encoding as CBOR strings, and anything else as number value: |
651 |
|
|
|
652 |
|
|
# dump as number |
653 |
|
|
encode_cbor [2] # yields [2] |
654 |
|
|
encode_cbor [-3.0e17] # yields [-3e+17] |
655 |
|
|
my $value = 5; encode_cbor [$value] # yields [5] |
656 |
|
|
|
657 |
root |
1.27 |
# used as string, so dump as string (either byte or text) |
658 |
root |
1.1 |
print $value; |
659 |
|
|
encode_cbor [$value] # yields ["5"] |
660 |
|
|
|
661 |
|
|
# undef becomes null |
662 |
|
|
encode_cbor [undef] # yields [null] |
663 |
|
|
|
664 |
|
|
You can force the type to be a CBOR string by stringifying it: |
665 |
|
|
|
666 |
|
|
my $x = 3.1; # some variable containing a number |
667 |
|
|
"$x"; # stringified |
668 |
|
|
$x .= ""; # another, more awkward way to stringify |
669 |
|
|
print $x; # perl does it for you, too, quite often |
670 |
|
|
|
671 |
root |
1.53 |
You can force whether a string is encoded as byte or text string by using |
672 |
|
|
C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled): |
673 |
root |
1.27 |
|
674 |
|
|
utf8::upgrade $x; # encode $x as text string |
675 |
|
|
utf8::downgrade $x; # encode $x as byte string |
676 |
|
|
|
677 |
|
|
Perl doesn't define what operations up- and downgrade strings, so if the |
678 |
|
|
difference between byte and text is important, you should up- or downgrade |
679 |
root |
1.53 |
your string as late as possible before encoding. You can also force the |
680 |
|
|
use of CBOR text strings by using C<text_keys> or C<text_strings>. |
681 |
root |
1.27 |
|
682 |
root |
1.1 |
You can force the type to be a CBOR number by numifying it: |
683 |
|
|
|
684 |
|
|
my $x = "3"; # some variable containing a string |
685 |
|
|
$x += 0; # numify it, ensuring it will be dumped as a number |
686 |
|
|
$x *= 1; # same thing, the choice is yours. |
687 |
|
|
|
688 |
|
|
You can not currently force the type in other, less obscure, ways. Tell me |
689 |
|
|
if you need this capability (but don't forget to explain why it's needed |
690 |
|
|
:). |
691 |
|
|
|
692 |
root |
1.4 |
Perl values that seem to be integers generally use the shortest possible |
693 |
|
|
representation. Floating-point values will use either the IEEE single |
694 |
|
|
format if possible without loss of precision, otherwise the IEEE double |
695 |
|
|
format will be used. Perls that use formats other than IEEE double to |
696 |
|
|
represent numerical values are supported, but might suffer loss of |
697 |
|
|
precision. |
698 |
root |
1.1 |
|
699 |
|
|
=back |
700 |
|
|
|
701 |
root |
1.7 |
=head2 OBJECT SERIALISATION |
702 |
|
|
|
703 |
root |
1.29 |
This module implements both a CBOR-specific and the generic |
704 |
|
|
L<Types::Serialier> object serialisation protocol. The following |
705 |
|
|
subsections explain both methods. |
706 |
|
|
|
707 |
|
|
=head3 ENCODING |
708 |
|
|
|
709 |
root |
1.7 |
This module knows two way to serialise a Perl object: The CBOR-specific |
710 |
|
|
way, and the generic way. |
711 |
|
|
|
712 |
root |
1.29 |
Whenever the encoder encounters a Perl object that it cannot serialise |
713 |
root |
1.7 |
directly (most of them), it will first look up the C<TO_CBOR> method on |
714 |
|
|
it. |
715 |
|
|
|
716 |
|
|
If it has a C<TO_CBOR> method, it will call it with the object as only |
717 |
|
|
argument, and expects exactly one return value, which it will then |
718 |
|
|
substitute and encode it in the place of the object. |
719 |
|
|
|
720 |
|
|
Otherwise, it will look up the C<FREEZE> method. If it exists, it will |
721 |
|
|
call it with the object as first argument, and the constant string C<CBOR> |
722 |
|
|
as the second argument, to distinguish it from other serialisers. |
723 |
|
|
|
724 |
|
|
The C<FREEZE> method can return any number of values (i.e. zero or |
725 |
|
|
more). These will be encoded as CBOR perl object, together with the |
726 |
|
|
classname. |
727 |
|
|
|
728 |
root |
1.29 |
These methods I<MUST NOT> change the data structure that is being |
729 |
|
|
serialised. Failure to comply to this can result in memory corruption - |
730 |
|
|
and worse. |
731 |
|
|
|
732 |
root |
1.7 |
If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
733 |
|
|
with an error. |
734 |
|
|
|
735 |
root |
1.29 |
=head3 DECODING |
736 |
|
|
|
737 |
|
|
Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded, |
738 |
|
|
but objects encoded via C<FREEZE> can be decoded using the following |
739 |
|
|
protocol: |
740 |
root |
1.7 |
|
741 |
|
|
When an encoded CBOR perl object is encountered by the decoder, it will |
742 |
|
|
look up the C<THAW> method, by using the stored classname, and will fail |
743 |
|
|
if the method cannot be found. |
744 |
|
|
|
745 |
|
|
After the lookup it will call the C<THAW> method with the stored classname |
746 |
|
|
as first argument, the constant string C<CBOR> as second argument, and all |
747 |
|
|
values returned by C<FREEZE> as remaining arguments. |
748 |
|
|
|
749 |
root |
1.29 |
=head3 EXAMPLES |
750 |
root |
1.7 |
|
751 |
|
|
Here is an example C<TO_CBOR> method: |
752 |
|
|
|
753 |
|
|
sub My::Object::TO_CBOR { |
754 |
|
|
my ($obj) = @_; |
755 |
|
|
|
756 |
|
|
["this is a serialised My::Object object", $obj->{id}] |
757 |
|
|
} |
758 |
|
|
|
759 |
|
|
When a C<My::Object> is encoded to CBOR, it will instead encode a simple |
760 |
|
|
array with two members: a string, and the "object id". Decoding this CBOR |
761 |
|
|
string will yield a normal perl array reference in place of the object. |
762 |
|
|
|
763 |
|
|
A more useful and practical example would be a serialisation method for |
764 |
|
|
the URI module. CBOR has a custom tag value for URIs, namely 32: |
765 |
|
|
|
766 |
|
|
sub URI::TO_CBOR { |
767 |
|
|
my ($self) = @_; |
768 |
|
|
my $uri = "$self"; # stringify uri |
769 |
|
|
utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
770 |
root |
1.28 |
CBOR::XS::tag 32, "$_[0]" |
771 |
root |
1.7 |
} |
772 |
|
|
|
773 |
|
|
This will encode URIs as a UTF-8 string with tag 32, which indicates an |
774 |
|
|
URI. |
775 |
|
|
|
776 |
|
|
Decoding such an URI will not (currently) give you an URI object, but |
777 |
|
|
instead a CBOR::XS::Tagged object with tag number 32 and the string - |
778 |
|
|
exactly what was returned by C<TO_CBOR>. |
779 |
|
|
|
780 |
|
|
To serialise an object so it can automatically be deserialised, you need |
781 |
|
|
to use C<FREEZE> and C<THAW>. To take the URI module as example, this |
782 |
|
|
would be a possible implementation: |
783 |
|
|
|
784 |
|
|
sub URI::FREEZE { |
785 |
|
|
my ($self, $serialiser) = @_; |
786 |
|
|
"$self" # encode url string |
787 |
|
|
} |
788 |
|
|
|
789 |
|
|
sub URI::THAW { |
790 |
|
|
my ($class, $serialiser, $uri) = @_; |
791 |
|
|
$class->new ($uri) |
792 |
|
|
} |
793 |
|
|
|
794 |
|
|
Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For |
795 |
|
|
example, a C<FREEZE> method that returns "type", "id" and "variant" values |
796 |
|
|
would cause an invocation of C<THAW> with 5 arguments: |
797 |
|
|
|
798 |
|
|
sub My::Object::FREEZE { |
799 |
|
|
my ($self, $serialiser) = @_; |
800 |
|
|
|
801 |
|
|
($self->{type}, $self->{id}, $self->{variant}) |
802 |
|
|
} |
803 |
|
|
|
804 |
|
|
sub My::Object::THAW { |
805 |
|
|
my ($class, $serialiser, $type, $id, $variant) = @_; |
806 |
|
|
|
807 |
|
|
$class-<new (type => $type, id => $id, variant => $variant) |
808 |
|
|
} |
809 |
|
|
|
810 |
root |
1.1 |
|
811 |
root |
1.7 |
=head1 MAGIC HEADER |
812 |
root |
1.3 |
|
813 |
|
|
There is no way to distinguish CBOR from other formats |
814 |
|
|
programmatically. To make it easier to distinguish CBOR from other |
815 |
|
|
formats, the CBOR specification has a special "magic string" that can be |
816 |
root |
1.18 |
prepended to any CBOR string without changing its meaning. |
817 |
root |
1.3 |
|
818 |
|
|
This string is available as C<$CBOR::XS::MAGIC>. This module does not |
819 |
root |
1.18 |
prepend this string to the CBOR data it generates, but it will ignore it |
820 |
root |
1.3 |
if present, so users can prepend this string as a "file type" indicator as |
821 |
|
|
required. |
822 |
|
|
|
823 |
|
|
|
824 |
root |
1.12 |
=head1 THE CBOR::XS::Tagged CLASS |
825 |
|
|
|
826 |
|
|
CBOR has the concept of tagged values - any CBOR value can be tagged with |
827 |
|
|
a numeric 64 bit number, which are centrally administered. |
828 |
|
|
|
829 |
|
|
C<CBOR::XS> handles a few tags internally when en- or decoding. You can |
830 |
|
|
also create tags yourself by encoding C<CBOR::XS::Tagged> objects, and the |
831 |
|
|
decoder will create C<CBOR::XS::Tagged> objects itself when it hits an |
832 |
|
|
unknown tag. |
833 |
|
|
|
834 |
|
|
These objects are simply blessed array references - the first member of |
835 |
|
|
the array being the numerical tag, the second being the value. |
836 |
|
|
|
837 |
|
|
You can interact with C<CBOR::XS::Tagged> objects in the following ways: |
838 |
|
|
|
839 |
|
|
=over 4 |
840 |
|
|
|
841 |
|
|
=item $tagged = CBOR::XS::tag $tag, $value |
842 |
|
|
|
843 |
|
|
This function(!) creates a new C<CBOR::XS::Tagged> object using the given |
844 |
|
|
C<$tag> (0..2**64-1) to tag the given C<$value> (which can be any Perl |
845 |
|
|
value that can be encoded in CBOR, including serialisable Perl objects and |
846 |
|
|
C<CBOR::XS::Tagged> objects). |
847 |
|
|
|
848 |
|
|
=item $tagged->[0] |
849 |
|
|
|
850 |
|
|
=item $tagged->[0] = $new_tag |
851 |
|
|
|
852 |
|
|
=item $tag = $tagged->tag |
853 |
|
|
|
854 |
|
|
=item $new_tag = $tagged->tag ($new_tag) |
855 |
|
|
|
856 |
|
|
Access/mutate the tag. |
857 |
|
|
|
858 |
|
|
=item $tagged->[1] |
859 |
|
|
|
860 |
|
|
=item $tagged->[1] = $new_value |
861 |
|
|
|
862 |
|
|
=item $value = $tagged->value |
863 |
|
|
|
864 |
|
|
=item $new_value = $tagged->value ($new_value) |
865 |
|
|
|
866 |
|
|
Access/mutate the tagged value. |
867 |
|
|
|
868 |
|
|
=back |
869 |
|
|
|
870 |
|
|
=cut |
871 |
|
|
|
872 |
|
|
sub tag($$) { |
873 |
|
|
bless [@_], CBOR::XS::Tagged::; |
874 |
|
|
} |
875 |
|
|
|
876 |
|
|
sub CBOR::XS::Tagged::tag { |
877 |
|
|
$_[0][0] = $_[1] if $#_; |
878 |
|
|
$_[0][0] |
879 |
|
|
} |
880 |
|
|
|
881 |
|
|
sub CBOR::XS::Tagged::value { |
882 |
|
|
$_[0][1] = $_[1] if $#_; |
883 |
|
|
$_[0][1] |
884 |
|
|
} |
885 |
|
|
|
886 |
root |
1.13 |
=head2 EXAMPLES |
887 |
|
|
|
888 |
|
|
Here are some examples of C<CBOR::XS::Tagged> uses to tag objects. |
889 |
|
|
|
890 |
|
|
You can look up CBOR tag value and emanings in the IANA registry at |
891 |
|
|
L<http://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml>. |
892 |
|
|
|
893 |
|
|
Prepend a magic header (C<$CBOR::XS::MAGIC>): |
894 |
|
|
|
895 |
|
|
my $cbor = encode_cbor CBOR::XS::tag 55799, $value; |
896 |
|
|
# same as: |
897 |
|
|
my $cbor = $CBOR::XS::MAGIC . encode_cbor $value; |
898 |
|
|
|
899 |
|
|
Serialise some URIs and a regex in an array: |
900 |
|
|
|
901 |
|
|
my $cbor = encode_cbor [ |
902 |
|
|
(CBOR::XS::tag 32, "http://www.nethype.de/"), |
903 |
|
|
(CBOR::XS::tag 32, "http://software.schmorp.de/"), |
904 |
|
|
(CBOR::XS::tag 35, "^[Pp][Ee][Rr][lL]\$"), |
905 |
|
|
]; |
906 |
|
|
|
907 |
|
|
Wrap CBOR data in CBOR: |
908 |
|
|
|
909 |
|
|
my $cbor_cbor = encode_cbor |
910 |
|
|
CBOR::XS::tag 24, |
911 |
|
|
encode_cbor [1, 2, 3]; |
912 |
|
|
|
913 |
root |
1.19 |
=head1 TAG HANDLING AND EXTENSIONS |
914 |
|
|
|
915 |
root |
1.22 |
This section describes how this module handles specific tagged values |
916 |
|
|
and extensions. If a tag is not mentioned here and no additional filters |
917 |
|
|
are provided for it, then the default handling applies (creating a |
918 |
|
|
CBOR::XS::Tagged object on decoding, and only encoding the tag when |
919 |
|
|
explicitly requested). |
920 |
root |
1.19 |
|
921 |
root |
1.23 |
Tags not handled specifically are currently converted into a |
922 |
|
|
L<CBOR::XS::Tagged> object, which is simply a blessed array reference |
923 |
|
|
consisting of the numeric tag value followed by the (decoded) CBOR value. |
924 |
|
|
|
925 |
root |
1.19 |
Future versions of this module reserve the right to special case |
926 |
root |
1.22 |
additional tags (such as base64url). |
927 |
|
|
|
928 |
|
|
=head2 ENFORCED TAGS |
929 |
|
|
|
930 |
|
|
These tags are always handled when decoding, and their handling cannot be |
931 |
root |
1.51 |
overridden by the user. |
932 |
root |
1.19 |
|
933 |
|
|
=over 4 |
934 |
|
|
|
935 |
root |
1.26 |
=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>) |
936 |
root |
1.19 |
|
937 |
root |
1.23 |
These tags are automatically created (and decoded) for serialisable |
938 |
|
|
objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object |
939 |
|
|
serialisation protocol). See L<OBJECT SERIALISATION> for details. |
940 |
root |
1.19 |
|
941 |
root |
1.45 |
=item 28, 29 (shareable, sharedref, L<http://cbor.schmorp.de/value-sharing>) |
942 |
root |
1.19 |
|
943 |
root |
1.31 |
These tags are automatically decoded when encountered (and they do not |
944 |
|
|
result in a cyclic data structure, see C<allow_cycles>), resulting in |
945 |
root |
1.19 |
shared values in the decoded object. They are only encoded, however, when |
946 |
root |
1.31 |
C<allow_sharing> is enabled. |
947 |
|
|
|
948 |
|
|
Not all shared values can be successfully decoded: values that reference |
949 |
|
|
themselves will I<currently> decode as C<undef> (this is not the same |
950 |
|
|
as a reference pointing to itself, which will be represented as a value |
951 |
|
|
that contains an indirect reference to itself - these will be decoded |
952 |
|
|
properly). |
953 |
|
|
|
954 |
|
|
Note that considerably more shared value data structures can be decoded |
955 |
|
|
than will be encoded - currently, only values pointed to by references |
956 |
|
|
will be shared, others will not. While non-reference shared values can be |
957 |
|
|
generated in Perl with some effort, they were considered too unimportant |
958 |
|
|
to be supported in the encoder. The decoder, however, will decode these |
959 |
|
|
values as shared values. |
960 |
root |
1.19 |
|
961 |
root |
1.45 |
=item 256, 25 (stringref-namespace, stringref, L<http://cbor.schmorp.de/stringref>) |
962 |
root |
1.21 |
|
963 |
|
|
These tags are automatically decoded when encountered. They are only |
964 |
root |
1.25 |
encoded, however, when C<pack_strings> is enabled. |
965 |
root |
1.21 |
|
966 |
root |
1.19 |
=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>) |
967 |
|
|
|
968 |
|
|
This tag is automatically generated when a reference are encountered (with |
969 |
root |
1.51 |
the exception of hash and array references). It is converted to a reference |
970 |
root |
1.19 |
when decoding. |
971 |
|
|
|
972 |
|
|
=item 55799 (self-describe CBOR, RFC 7049) |
973 |
|
|
|
974 |
|
|
This value is not generated on encoding (unless explicitly requested by |
975 |
|
|
the user), and is simply ignored when decoding. |
976 |
|
|
|
977 |
|
|
=back |
978 |
|
|
|
979 |
root |
1.24 |
=head2 NON-ENFORCED TAGS |
980 |
root |
1.22 |
|
981 |
|
|
These tags have default filters provided when decoding. Their handling can |
982 |
root |
1.51 |
be overridden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by |
983 |
root |
1.24 |
providing a custom C<filter> callback when decoding. |
984 |
root |
1.22 |
|
985 |
|
|
When they result in decoding into a specific Perl class, the module |
986 |
|
|
usually provides a corresponding C<TO_CBOR> method as well. |
987 |
|
|
|
988 |
|
|
When any of these need to load additional modules that are not part of the |
989 |
|
|
perl core distribution (e.g. L<URI>), it is (currently) up to the user to |
990 |
|
|
provide these modules. The decoding usually fails with an exception if the |
991 |
|
|
required module cannot be loaded. |
992 |
|
|
|
993 |
|
|
=over 4 |
994 |
|
|
|
995 |
root |
1.35 |
=item 0, 1 (date/time string, seconds since the epoch) |
996 |
|
|
|
997 |
|
|
These tags are decoded into L<Time::Piece> objects. The corresponding |
998 |
|
|
C<Time::Piece::TO_CBOR> method always encodes into tag 1 values currently. |
999 |
|
|
|
1000 |
|
|
The L<Time::Piece> API is generally surprisingly bad, and fractional |
1001 |
|
|
seconds are only accidentally kept intact, so watch out. On the plus side, |
1002 |
|
|
the module comes with perl since 5.10, which has to count for something. |
1003 |
|
|
|
1004 |
root |
1.22 |
=item 2, 3 (positive/negative bignum) |
1005 |
|
|
|
1006 |
|
|
These tags are decoded into L<Math::BigInt> objects. The corresponding |
1007 |
|
|
C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR |
1008 |
|
|
integers, and others into positive/negative CBOR bignums. |
1009 |
|
|
|
1010 |
root |
1.55 |
=item 4, 5, 264, 265 (decimal fraction/bigfloat) |
1011 |
root |
1.22 |
|
1012 |
|
|
Both decimal fractions and bigfloats are decoded into L<Math::BigFloat> |
1013 |
|
|
objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always> |
1014 |
root |
1.55 |
encodes into a decimal fraction (either tag 4 or 264). |
1015 |
root |
1.22 |
|
1016 |
root |
1.55 |
NaN and infinities are not encoded properly, as they cannot be represented |
1017 |
|
|
in CBOR. |
1018 |
root |
1.22 |
|
1019 |
root |
1.55 |
See L<BIGNUM SECURITY CONSIDERATIONS> for more info. |
1020 |
root |
1.22 |
|
1021 |
root |
1.58 |
=item 30 (rational numbers) |
1022 |
|
|
|
1023 |
|
|
These tags are decoded into L<Math::BigRat> objects. The corresponding |
1024 |
|
|
C<Math::BigRat::TO_CBOR> method encodes rational numbers with denominator |
1025 |
|
|
C<1> via their numerator only, i.e., they become normal integers or |
1026 |
|
|
C<bignums>. |
1027 |
|
|
|
1028 |
|
|
See L<BIGNUM SECURITY CONSIDERATIONS> for more info. |
1029 |
|
|
|
1030 |
root |
1.22 |
=item 21, 22, 23 (expected later JSON conversion) |
1031 |
|
|
|
1032 |
|
|
CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these |
1033 |
|
|
tags. |
1034 |
|
|
|
1035 |
|
|
=item 32 (URI) |
1036 |
|
|
|
1037 |
|
|
These objects decode into L<URI> objects. The corresponding |
1038 |
|
|
C<URI::TO_CBOR> method again results in a CBOR URI value. |
1039 |
|
|
|
1040 |
|
|
=back |
1041 |
|
|
|
1042 |
|
|
=cut |
1043 |
|
|
|
1044 |
root |
1.7 |
=head1 CBOR and JSON |
1045 |
root |
1.1 |
|
1046 |
root |
1.4 |
CBOR is supposed to implement a superset of the JSON data model, and is, |
1047 |
|
|
with some coercion, able to represent all JSON texts (something that other |
1048 |
|
|
"binary JSON" formats such as BSON generally do not support). |
1049 |
|
|
|
1050 |
|
|
CBOR implements some extra hints and support for JSON interoperability, |
1051 |
|
|
and the spec offers further guidance for conversion between CBOR and |
1052 |
|
|
JSON. None of this is currently implemented in CBOR, and the guidelines |
1053 |
|
|
in the spec do not result in correct round-tripping of data. If JSON |
1054 |
|
|
interoperability is improved in the future, then the goal will be to |
1055 |
|
|
ensure that decoded JSON data will round-trip encoding and decoding to |
1056 |
|
|
CBOR intact. |
1057 |
root |
1.1 |
|
1058 |
|
|
|
1059 |
|
|
=head1 SECURITY CONSIDERATIONS |
1060 |
|
|
|
1061 |
root |
1.65 |
Tl;dr... if you want to decode or encode CBOR from untrusted sources, you |
1062 |
|
|
should start with a coder object created via C<new_safe>: |
1063 |
|
|
|
1064 |
|
|
my $coder = CBOR::XS->new_safe; |
1065 |
root |
1.1 |
|
1066 |
root |
1.65 |
my $data = $coder->decode ($cbor_text); |
1067 |
|
|
my $cbor = $coder->encode ($data); |
1068 |
|
|
|
1069 |
|
|
Longer version: When you are using CBOR in a protocol, talking to |
1070 |
|
|
untrusted potentially hostile creatures requires some thought: |
1071 |
|
|
|
1072 |
|
|
=over 4 |
1073 |
|
|
|
1074 |
|
|
=item Security of the CBOR decoder itself |
1075 |
|
|
|
1076 |
|
|
First and foremost, your CBOR decoder should be secure, that is, should |
1077 |
|
|
not have any buffer overflows or similar bugs that could potentially be |
1078 |
|
|
exploited. Obviously, this module should ensure that and I am trying hard |
1079 |
|
|
on making that true, but you never know. |
1080 |
|
|
|
1081 |
|
|
=item CBOR::XS can invoke almost arbitrary callbacks during decoding |
1082 |
|
|
|
1083 |
|
|
CBOR::XS supports object serialisation - decoding CBOR can cause calls |
1084 |
|
|
to I<any> C<THAW> method in I<any> package that exists in your process |
1085 |
|
|
(that is, CBOR::XS will not try to load modules, but any existing C<THAW> |
1086 |
|
|
method or function can be called, so they all have to be secure). |
1087 |
|
|
|
1088 |
|
|
Less obviously, it will also invoke C<TO_CBOR> and C<FREEZE> methods - |
1089 |
|
|
even if all your C<THAW> methods are secure, encoding data structures from |
1090 |
|
|
untrusted sources can invoke those and trigger bugs in those. |
1091 |
|
|
|
1092 |
|
|
So, if you are not sure about the security of all the modules you |
1093 |
|
|
have loaded (you shouldn't), you should disable this part using |
1094 |
|
|
C<forbid_objects>. |
1095 |
|
|
|
1096 |
|
|
=item CBOR can be extended with tags that call library code |
1097 |
|
|
|
1098 |
|
|
CBOR can be extended with tags, and C<CBOR::XS> has a registry of |
1099 |
|
|
conversion functions for many existing tags that can be extended via |
1100 |
|
|
third-party modules (see the C<filter> method). |
1101 |
|
|
|
1102 |
|
|
If you don't trust these, you should configure the "safe" filter function, |
1103 |
|
|
C<CBOR::XS::safe_filter>, which by default only includes conversion |
1104 |
|
|
functions that are considered "safe" by the author (but again, they can be |
1105 |
|
|
extended by third party modules). |
1106 |
|
|
|
1107 |
|
|
Depending on your level of paranoia, you can use the "safe" filter: |
1108 |
|
|
|
1109 |
|
|
$cbor->filter (\&CBOR::XS::safe_filter); |
1110 |
|
|
|
1111 |
|
|
... your own filter... |
1112 |
|
|
|
1113 |
|
|
$cbor->filter (sub { ... do your stuffs here ... }); |
1114 |
|
|
|
1115 |
|
|
... or even no filter at all, disabling all tag decoding: |
1116 |
|
|
|
1117 |
|
|
$cbor->filter (sub { }); |
1118 |
|
|
|
1119 |
|
|
This is never a problem for encoding, as the tag mechanism only exists in |
1120 |
|
|
CBOR texts. |
1121 |
|
|
|
1122 |
|
|
=item Resource-starving attacks: object memory usage |
1123 |
|
|
|
1124 |
|
|
You need to avoid resource-starving attacks. That means you should limit |
1125 |
|
|
the size of CBOR data you accept, or make sure then when your resources |
1126 |
|
|
run out, that's just fine (e.g. by using a separate process that can |
1127 |
|
|
crash safely). The size of a CBOR string in octets is usually a good |
1128 |
root |
1.1 |
indication of the size of the resources required to decode it into a Perl |
1129 |
root |
1.65 |
structure. While CBOR::XS can check the size of the CBOR text (using |
1130 |
|
|
C<max_size>), it might be too late when you already have it in memory, so |
1131 |
|
|
you might want to check the size before you accept the string. |
1132 |
|
|
|
1133 |
|
|
As for encoding, it is possible to construct data structures that are |
1134 |
|
|
relatively small but result in large CBOR texts (for example by having an |
1135 |
|
|
array full of references to the same big data structure, which will all be |
1136 |
|
|
deep-cloned during encoding by default). This is rarely an actual issue |
1137 |
|
|
(and the worst case is still just running out of memory), but you can |
1138 |
|
|
reduce this risk by using C<allow_sharing>. |
1139 |
|
|
|
1140 |
|
|
=item Resource-starving attacks: stack overflows |
1141 |
|
|
|
1142 |
|
|
CBOR::XS recurses using the C stack when decoding objects and arrays. The |
1143 |
|
|
C stack is a limited resource: for instance, on my amd64 machine with 8MB |
1144 |
|
|
of stack size I can decode around 180k nested arrays but only 14k nested |
1145 |
|
|
CBOR objects (due to perl itself recursing deeply on croak to free the |
1146 |
|
|
temporary). If that is exceeded, the program crashes. To be conservative, |
1147 |
|
|
the default nesting limit is set to 512. If your process has a smaller |
1148 |
|
|
stack, you should adjust this setting accordingly with the C<max_depth> |
1149 |
|
|
method. |
1150 |
|
|
|
1151 |
|
|
=item Resource-starving attacks: CPU en-/decoding complexity |
1152 |
|
|
|
1153 |
|
|
CBOR::XS will use the L<Math::BigInt>, L<Math::BigFloat> and |
1154 |
|
|
L<Math::BigRat> libraries to represent encode/decode bignums. These can |
1155 |
|
|
be very slow (as in, centuries of CPU time) and can even crash your |
1156 |
|
|
program (and are generally not very trustworthy). See the next section for |
1157 |
|
|
details. |
1158 |
|
|
|
1159 |
|
|
=item Data breaches: leaking information in error messages |
1160 |
|
|
|
1161 |
|
|
CBOR::XS might leak contents of your Perl data structures in its error |
1162 |
|
|
messages, so when you serialise sensitive information you might want to |
1163 |
|
|
make sure that exceptions thrown by CBOR::XS will not end up in front of |
1164 |
|
|
untrusted eyes. |
1165 |
|
|
|
1166 |
|
|
=item Something else... |
1167 |
root |
1.1 |
|
1168 |
|
|
Something else could bomb you, too, that I forgot to think of. In that |
1169 |
|
|
case, you get to keep the pieces. I am always open for hints, though... |
1170 |
|
|
|
1171 |
root |
1.65 |
=back |
1172 |
root |
1.1 |
|
1173 |
root |
1.55 |
|
1174 |
|
|
=head1 BIGNUM SECURITY CONSIDERATIONS |
1175 |
|
|
|
1176 |
|
|
CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and |
1177 |
|
|
L<Math::BigFloat> that tries to encode the number in the simplest possible |
1178 |
|
|
way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag |
1179 |
root |
1.58 |
4) or an arbitrary-exponent decimal fraction (tag 264). Rational numbers |
1180 |
|
|
(L<Math::BigRat>, tag 30) can also contain bignums as members. |
1181 |
root |
1.55 |
|
1182 |
root |
1.58 |
CBOR::XS will also understand base-2 bigfloat or arbitrary-exponent |
1183 |
|
|
bigfloats (tags 5 and 265), but it will never generate these on its own. |
1184 |
root |
1.55 |
|
1185 |
|
|
Using the built-in L<Math::BigInt::Calc> support, encoding and decoding |
1186 |
|
|
decimal fractions is generally fast. Decoding bigints can be slow for very |
1187 |
root |
1.58 |
big numbers (tens of thousands of digits, something that could potentially |
1188 |
|
|
be caught by limiting the size of CBOR texts), and decoding bigfloats or |
1189 |
|
|
arbitrary-exponent bigfloats can be I<extremely> slow (minutes, decades) |
1190 |
|
|
for large exponents (roughly 40 bit and longer). |
1191 |
root |
1.55 |
|
1192 |
|
|
Additionally, L<Math::BigInt> can take advantage of other bignum |
1193 |
root |
1.58 |
libraries, such as L<Math::GMP>, which cannot handle big floats with large |
1194 |
|
|
exponents, and might simply abort or crash your program, due to their code |
1195 |
|
|
quality. |
1196 |
root |
1.55 |
|
1197 |
|
|
This can be a concern if you want to parse untrusted CBOR. If it is, you |
1198 |
root |
1.58 |
might want to disable decoding of tag 2 (bigint) and 3 (negative bigint) |
1199 |
|
|
types. You should also disable types 5 and 265, as these can be slow even |
1200 |
|
|
without bigints. |
1201 |
|
|
|
1202 |
|
|
Disabling bigints will also partially or fully disable types that rely on |
1203 |
|
|
them, e.g. rational numbers that use bignums. |
1204 |
root |
1.55 |
|
1205 |
|
|
|
1206 |
root |
1.1 |
=head1 CBOR IMPLEMENTATION NOTES |
1207 |
|
|
|
1208 |
|
|
This section contains some random implementation notes. They do not |
1209 |
|
|
describe guaranteed behaviour, but merely behaviour as-is implemented |
1210 |
|
|
right now. |
1211 |
|
|
|
1212 |
|
|
64 bit integers are only properly decoded when Perl was built with 64 bit |
1213 |
|
|
support. |
1214 |
|
|
|
1215 |
|
|
Strings and arrays are encoded with a definite length. Hashes as well, |
1216 |
|
|
unless they are tied (or otherwise magical). |
1217 |
|
|
|
1218 |
|
|
Only the double data type is supported for NV data types - when Perl uses |
1219 |
|
|
long double to represent floating point values, they might not be encoded |
1220 |
|
|
properly. Half precision types are accepted, but not encoded. |
1221 |
|
|
|
1222 |
|
|
Strict mode and canonical mode are not implemented. |
1223 |
|
|
|
1224 |
|
|
|
1225 |
root |
1.30 |
=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT |
1226 |
|
|
|
1227 |
|
|
On perls that were built without 64 bit integer support (these are rare |
1228 |
root |
1.43 |
nowadays, even on 32 bit architectures, as all major Perl distributions |
1229 |
|
|
are built with 64 bit integer support), support for any kind of 64 bit |
1230 |
root |
1.30 |
integer in CBOR is very limited - most likely, these 64 bit values will |
1231 |
|
|
be truncated, corrupted, or otherwise not decoded correctly. This also |
1232 |
|
|
includes string, array and map sizes that are stored as 64 bit integers. |
1233 |
|
|
|
1234 |
|
|
|
1235 |
root |
1.1 |
=head1 THREADS |
1236 |
|
|
|
1237 |
|
|
This module is I<not> guaranteed to be thread safe and there are no |
1238 |
|
|
plans to change this until Perl gets thread support (as opposed to the |
1239 |
|
|
horribly slow so-called "threads" which are simply slow and bloated |
1240 |
|
|
process simulations - use fork, it's I<much> faster, cheaper, better). |
1241 |
|
|
|
1242 |
|
|
(It might actually work, but you have been warned). |
1243 |
|
|
|
1244 |
|
|
|
1245 |
|
|
=head1 BUGS |
1246 |
|
|
|
1247 |
|
|
While the goal of this module is to be correct, that unfortunately does |
1248 |
|
|
not mean it's bug-free, only that I think its design is bug-free. If you |
1249 |
|
|
keep reporting bugs they will be fixed swiftly, though. |
1250 |
|
|
|
1251 |
|
|
Please refrain from using rt.cpan.org or any other bug reporting |
1252 |
|
|
service. I put the contact address into my modules for a reason. |
1253 |
|
|
|
1254 |
|
|
=cut |
1255 |
|
|
|
1256 |
root |
1.65 |
# clumsy and slow hv_store-in-hash helper function |
1257 |
root |
1.64 |
sub _hv_store { |
1258 |
|
|
$_[0]{$_[1]} = $_[2]; |
1259 |
|
|
} |
1260 |
|
|
|
1261 |
root |
1.22 |
our %FILTER = ( |
1262 |
root |
1.35 |
0 => sub { # rfc4287 datetime, utf-8 |
1263 |
|
|
require Time::Piece; |
1264 |
|
|
# Time::Piece::Strptime uses the "incredibly flexible date parsing routine" |
1265 |
|
|
# from FreeBSD, which can't parse ISO 8601, RFC3339, RFC4287 or much of anything |
1266 |
|
|
# else either. Whats incredibe over standard strptime totally escapes me. |
1267 |
|
|
# doesn't do fractional times, either. sigh. |
1268 |
root |
1.36 |
# In fact, it's all a lie, it uses whatever strptime it wants, and of course, |
1269 |
root |
1.47 |
# they are all incompatible. The openbsd one simply ignores %z (but according to the |
1270 |
root |
1.37 |
# docs, it would be much more incredibly flexible indeed. If it worked, that is.). |
1271 |
root |
1.35 |
scalar eval { |
1272 |
|
|
my $s = $_[1]; |
1273 |
|
|
|
1274 |
|
|
$s =~ s/Z$/+00:00/; |
1275 |
root |
1.36 |
$s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])$// |
1276 |
root |
1.35 |
or die; |
1277 |
|
|
|
1278 |
root |
1.36 |
my $b = $1 - ($2 * 60 + $3) * 60; # fractional part + offset. hopefully |
1279 |
|
|
my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S"); |
1280 |
root |
1.35 |
|
1281 |
root |
1.36 |
Time::Piece::gmtime ($d->epoch + $b) |
1282 |
root |
1.35 |
} || die "corrupted CBOR date/time string ($_[0])"; |
1283 |
|
|
}, |
1284 |
|
|
|
1285 |
|
|
1 => sub { # seconds since the epoch, possibly fractional |
1286 |
|
|
require Time::Piece; |
1287 |
|
|
scalar Time::Piece::gmtime (pop) |
1288 |
|
|
}, |
1289 |
root |
1.22 |
|
1290 |
|
|
2 => sub { # pos bigint |
1291 |
|
|
require Math::BigInt; |
1292 |
root |
1.57 |
Math::BigInt->new ("0x" . unpack "H*", pop) |
1293 |
root |
1.22 |
}, |
1294 |
|
|
|
1295 |
|
|
3 => sub { # neg bigint |
1296 |
|
|
require Math::BigInt; |
1297 |
root |
1.57 |
-Math::BigInt->new ("0x" . unpack "H*", pop) |
1298 |
root |
1.22 |
}, |
1299 |
|
|
|
1300 |
|
|
4 => sub { # decimal fraction, array |
1301 |
|
|
require Math::BigFloat; |
1302 |
|
|
Math::BigFloat->new ($_[1][1] . "E" . $_[1][0]) |
1303 |
|
|
}, |
1304 |
|
|
|
1305 |
root |
1.58 |
264 => sub { # decimal fraction with arbitrary exponent |
1306 |
|
|
require Math::BigFloat; |
1307 |
|
|
Math::BigFloat->new ($_[1][1] . "E" . $_[1][0]) |
1308 |
|
|
}, |
1309 |
|
|
|
1310 |
root |
1.22 |
5 => sub { # bigfloat, array |
1311 |
|
|
require Math::BigFloat; |
1312 |
root |
1.50 |
scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0]) |
1313 |
root |
1.22 |
}, |
1314 |
|
|
|
1315 |
root |
1.58 |
265 => sub { # bigfloat with arbitrary exponent |
1316 |
|
|
require Math::BigFloat; |
1317 |
|
|
scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0]) |
1318 |
|
|
}, |
1319 |
|
|
|
1320 |
|
|
30 => sub { # rational number |
1321 |
|
|
require Math::BigRat; |
1322 |
|
|
Math::BigRat->new ("$_[1][0]/$_[1][1]") # separate parameters only work in recent versons |
1323 |
|
|
}, |
1324 |
|
|
|
1325 |
root |
1.22 |
21 => sub { pop }, # expected conversion to base64url encoding |
1326 |
|
|
22 => sub { pop }, # expected conversion to base64 encoding |
1327 |
|
|
23 => sub { pop }, # expected conversion to base16 encoding |
1328 |
|
|
|
1329 |
|
|
# 24 # embedded cbor, byte string |
1330 |
|
|
|
1331 |
|
|
32 => sub { |
1332 |
|
|
require URI; |
1333 |
|
|
URI->new (pop) |
1334 |
|
|
}, |
1335 |
|
|
|
1336 |
|
|
# 33 # base64url rfc4648, utf-8 |
1337 |
|
|
# 34 # base64 rfc46484, utf-8 |
1338 |
|
|
# 35 # regex pcre/ecma262, utf-8 |
1339 |
|
|
# 36 # mime message rfc2045, utf-8 |
1340 |
|
|
); |
1341 |
|
|
|
1342 |
root |
1.65 |
sub default_filter { |
1343 |
root |
1.22 |
&{ $FILTER{$_[0]} or return } |
1344 |
|
|
} |
1345 |
|
|
|
1346 |
root |
1.65 |
our %SAFE_FILTER = map { $_ => $FILTER{$_} } 0, 1, 21, 22, 23, 32; |
1347 |
|
|
|
1348 |
|
|
sub safe_filter { |
1349 |
|
|
&{ $SAFE_FILTER{$_[0]} or return } |
1350 |
|
|
} |
1351 |
|
|
|
1352 |
root |
1.22 |
sub URI::TO_CBOR { |
1353 |
|
|
my $uri = $_[0]->as_string; |
1354 |
|
|
utf8::upgrade $uri; |
1355 |
root |
1.35 |
tag 32, $uri |
1356 |
root |
1.22 |
} |
1357 |
|
|
|
1358 |
|
|
sub Math::BigInt::TO_CBOR { |
1359 |
root |
1.55 |
if (-2147483648 <= $_[0] && $_[0] <= 2147483647) { |
1360 |
root |
1.22 |
$_[0]->numify |
1361 |
|
|
} else { |
1362 |
|
|
my $hex = substr $_[0]->as_hex, 2; |
1363 |
|
|
$hex = "0$hex" if 1 & length $hex; # sigh |
1364 |
root |
1.35 |
tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex |
1365 |
root |
1.22 |
} |
1366 |
|
|
} |
1367 |
|
|
|
1368 |
|
|
sub Math::BigFloat::TO_CBOR { |
1369 |
|
|
my ($m, $e) = $_[0]->parts; |
1370 |
root |
1.55 |
|
1371 |
|
|
-9223372036854775808 <= $e && $e <= 18446744073709551615 |
1372 |
|
|
? tag 4, [$e->numify, $m] |
1373 |
|
|
: tag 264, [$e, $m] |
1374 |
root |
1.35 |
} |
1375 |
|
|
|
1376 |
root |
1.58 |
sub Math::BigRat::TO_CBOR { |
1377 |
|
|
my ($n, $d) = $_[0]->parts; |
1378 |
|
|
|
1379 |
root |
1.60 |
# older versions of BigRat need *1, as they not always return numbers |
1380 |
root |
1.59 |
|
1381 |
|
|
$d*1 == 1 |
1382 |
|
|
? $n*1 |
1383 |
|
|
: tag 30, [$n*1, $d*1] |
1384 |
root |
1.58 |
} |
1385 |
|
|
|
1386 |
root |
1.35 |
sub Time::Piece::TO_CBOR { |
1387 |
root |
1.40 |
tag 1, 0 + $_[0]->epoch |
1388 |
root |
1.22 |
} |
1389 |
|
|
|
1390 |
root |
1.1 |
XSLoader::load "CBOR::XS", $VERSION; |
1391 |
|
|
|
1392 |
|
|
=head1 SEE ALSO |
1393 |
|
|
|
1394 |
|
|
The L<JSON> and L<JSON::XS> modules that do similar, but human-readable, |
1395 |
|
|
serialisation. |
1396 |
|
|
|
1397 |
root |
1.6 |
The L<Types::Serialiser> module provides the data model for true, false |
1398 |
|
|
and error values. |
1399 |
|
|
|
1400 |
root |
1.1 |
=head1 AUTHOR |
1401 |
|
|
|
1402 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
1403 |
|
|
http://home.schmorp.de/ |
1404 |
|
|
|
1405 |
|
|
=cut |
1406 |
|
|
|
1407 |
root |
1.6 |
1 |
1408 |
|
|
|