[ViewVC] Diff of: cvs/CBOR-XS/XS.pm

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.24 by root, Fri Nov 22 16:18:59 2013 UTC vs.
Revision 1.64 by root, Fri Nov 25 23:37:27 2016 UTC

     substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string
  }
 =head1 DESCRIPTION
-WARNING! This module is very new, and not very well tested (that's up
-to you to do). Furthermore, details of the implementation might change
-freely before version 1.0. And lastly, most extensions depend on an IANA
-assignment, and until that assignment is official, this implementation is
-not interoperable with other implementations (even future versions of this
-module) until the assignment is done.
-You are still invited to try out CBOR, and this module.
 This module converts Perl data structures to the Concise Binary Object
 Representation (CBOR) and vice versa. CBOR is a fast binary serialisation
-format that aims to use a superset of the JSON data model, i.e. when you
+format that aims to use an (almost) superset of the JSON data model, i.e.
-can represent something in JSON, you should be able to represent it in
+when you can represent something useful in JSON, you should be able to
-CBOR.
+represent it in CBOR.
-In short, CBOR is a faster and very compact binary alternative to JSON,
+In short, CBOR is a faster and quite compact binary alternative to JSON,
 with the added ability of supporting serialisation of Perl objects. (JSON
 often compresses better than CBOR though, so if you plan to compress the
-data later you might want to compare both formats first).
+data later and speed is less important you might want to compare both
+formats first).
 To give you a general idea about speed, with texts in the megabyte range,
 C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or
 L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the
 data, the worse L<Storable> performs in comparison.
-As for compactness, C<CBOR::XS> encoded data structures are usually about
+Regarding compactness, C<CBOR::XS>-encoded data structures are usually
-20% smaller than the same data encoded as (compact) JSON or L<Storable>.
+about 20% smaller than the same data encoded as (compact) JSON or
+L<Storable>.
-In addition to the core CBOR data format, this module implements a number
+In addition to the core CBOR data format, this module implements a
-of extensions, to support cyclic and self-referencing data structures
+number of extensions, to support cyclic and shared data structures
-(see C<allow_sharing>), string deduplication (see C<allow_stringref>) and
+(see C<allow_sharing> and C<allow_cycles>), string deduplication (see
-scalar references (always enabled).
+C<pack_strings>) and scalar references (always enabled).
 The primary goal of this module is to be I<correct> and the secondary goal
 is to be I<fast>. To reach the latter goal it was written in C.
 See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and
 package CBOR::XS;
 use common::sense;
-our $VERSION = 0.09;
+our $VERSION = 1.51;
 our @ISA = qw(Exporter);
 our @EXPORT = qw(encode_cbor decode_cbor);
 use Exporter;
 as an array, is referenced multiple times), but instead will emit a
 reference to the earlier value.
 This means that such values will only be encoded once, and will not result
 in a deep cloning of the value on decode, in decoders supporting the value
-sharing extension.
+sharing extension. This also makes it possible to encode cyclic data
+structures (which need C<allow_cycles> to be enabled to be decoded by this
+module).
 It is recommended to leave it off unless you know your
 communication partner supports the value sharing extensions to CBOR
-(http://cbor.schmorp.de/value-sharing).
+(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
+resulting data structure might be unusable.
 Detecting shared values incurs a runtime overhead when values are encoded
 that have a reference counter large than one, and might unnecessarily
 increase the encoded size, as potentially shared values are encode as
-sharable whether or not they are actually shared.
+shareable whether or not they are actually shared.
 At the moment, only targets of references can be shared (e.g. scalars,
 arrays or hashes pointed to by a reference). Weirder constructs, such as
 an array with multiple "copies" of the I<same> string, which are hard but
 not impossible to create in Perl, are not supported (this is the same as
-for L<Storable>).
+with L<Storable>).
-If C<$enable> is false (the default), then C<encode> will encode
+If C<$enable> is false (the default), then C<encode> will encode shared
-exception when it encounters anything it cannot encode as CBOR.
+data structures repeatedly, unsharing them in the process. Cyclic data
+structures cannot be encoded in this mode.
 This option does not affect C<decode> in any way - shared values and
 references will always be decoded properly if present.
+=item $cbor = $cbor->allow_cycles ([$enable])
+=item $enabled = $cbor->get_allow_cycles
+If C<$enable> is true (or missing), then C<decode> will happily decode
+self-referential (cyclic) data structures. By default these will not be
+decoded, as they need manual cleanup to avoid memory leaks, so code that
+isn't prepared for this will not leak memory.
+If C<$enable> is false (the default), then C<decode> will throw an error
+when it encounters a self-referential/cyclic data structure.
+FUTURE DIRECTION: the motivation behind this option is to avoid I<real>
+cycles - future versions of this module might chose to decode cyclic data
+structures using weak references when this option is off, instead of
+throwing an error.
+This option does not affect C<encode> in any way - shared values and
+references will always be encoded properly if present.
-=item $cbor = $cbor->allow_stringref ([$enable])
+=item $cbor = $cbor->pack_strings ([$enable])
-=item $enabled = $cbor->get_allow_stringref
+=item $enabled = $cbor->get_pack_strings
 If C<$enable> is true (or missing), then C<encode> will try not to encode
 the same string twice, but will instead encode a reference to the string
-instead. Depending on your data format. this can save a lot of space, but
+instead. Depending on your data format, this can save a lot of space, but
 also results in a very large runtime overhead (expect encoding times to be
 2-4 times as high as without).
 It is recommended to leave it off unless you know your
 communications partner supports the stringref extension to CBOR
-(http://cbor.schmorp.de/stringref).
+(L<http://cbor.schmorp.de/stringref>), as without decoder support, the
+resulting data structure might not be usable.
-If C<$enable> is false (the default), then C<encode> will encode
+If C<$enable> is false (the default), then C<encode> will encode strings
-exception when it encounters anything it cannot encode as CBOR.
+the standard CBOR way.
 This option does not affect C<decode> in any way - string references will
 always be decoded properly if present.
+=item $cbor = $cbor->text_keys ([$enable])
+=item $enabled = $cbor->get_text_keys
+If C<$enabled> is true (or missing), then C<encode> will encode all
+perl hash keys as CBOR text strings/UTF-8 string, upgrading them as needed.
+If C<$enable> is false (the default), then C<encode> will encode hash keys
+normally - upgraded perl strings (strings internally encoded as UTF-8) as
+CBOR text strings, and downgraded perl strings as CBOR byte strings.
+This option does not affect C<decode> in any way.
+This option is useful for interoperability with CBOR decoders that don't
+treat byte strings as a form of text. It is especially useful as Perl
+gives very little control over hash keys.
+Enabling this option can be slow, as all downgraded hash keys that are
+encoded need to be scanned and converted to UTF-8.
+=item $cbor = $cbor->text_strings ([$enable])
+=item $enabled = $cbor->get_text_strings
+This option works similar to C<text_keys>, above, but works on all strings
+(including hash keys), so C<text_keys> has no further effect after
+enabling C<text_strings>.
+If C<$enabled> is true (or missing), then C<encode> will encode all perl
+strings as CBOR text strings/UTF-8 strings, upgrading them as needed.
+If C<$enable> is false (the default), then C<encode> will encode strings
+normally (but see C<text_keys>) - upgraded perl strings (strings
+internally encoded as UTF-8) as CBOR text strings, and downgraded perl
+strings as CBOR byte strings.
+This option does not affect C<decode> in any way.
+This option has similar advantages and disadvantages as C<text_keys>. In
+addition, this option effectively removes the ability to encode byte
+strings, which might break some C<FREEZE> and C<TO_CBOR> methods that rely
+on this, such as bignum encoding, so this option is mainly useful for very
+simple data.
+=item $cbor = $cbor->validate_utf8 ([$enable])
+=item $enabled = $cbor->get_validate_utf8
+If C<$enable> is true (or missing), then C<decode> will validate that
+elements (text strings) containing UTF-8 data in fact contain valid UTF-8
+data (instead of blindly accepting it). This validation obviously takes
+extra time during decoding.
+The concept of "valid UTF-8" used is perl's concept, which is a superset
+of the official UTF-8.
+If C<$enable> is false (the default), then C<decode> will blindly accept
+UTF-8 data, marking them as valid UTF-8 in the resulting data structure
+regardless of whether that's true or not.
+Perl isn't too happy about corrupted UTF-8 in strings, but should
+generally not crash or do similarly evil things. Extensions might be not
+so forgiving, so it's recommended to turn on this setting if you receive
+untrusted CBOR.
+This option does not affect C<encode> in any way - strings that are
+supposedly valid UTF-8 will simply be dumped into the resulting CBOR
+string without checking whether that is, in fact, true or not.
 =item $cbor = $cbor->filter ([$cb->($tag, $value)])
 =item $cb_or_undef = $cbor->get_filter
 function, C<CBOR::XS::default_filter>, is used. This function simply looks
 up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be
 a code reference that is called with tag and value, and is responsible for
 decoding the value. If no entry exists, it returns no values.
-Example: decode all tags not handled internally into CBOR::XS::Tagged
+Example: decode all tags not handled internally into C<CBOR::XS::Tagged>
 objects, with no other special handling (useful when working with
 potentially "unsafe" CBOR data).
    CBOR::XS->new->filter (sub { })->decode ($cbor_data);
 and you need to know where the first CBOR string ends amd the next one
 starts.
    CBOR::XS->new->decode_prefix ("......")
    => ("...", 3)
+=back
+=head2 INCREMENTAL PARSING
+In some cases, there is the need for incremental parsing of JSON
+texts. While this module always has to keep both CBOR text and resulting
+Perl data structure in memory at one time, it does allow you to parse a
+CBOR stream incrementally, using a similar to using "decode_prefix" to see
+if a full CBOR object is available, but is much more efficient.
+It basically works by parsing as much of a CBOR string as possible - if
+the CBOR data is not complete yet, the pasrer will remember where it was,
+to be able to restart when more data has been accumulated. Once enough
+data is available to either decode a complete CBOR value or raise an
+error, a real decode will be attempted.
+A typical use case would be a network protocol that consists of sending
+and receiving CBOR-encoded messages. The solution that works with CBOR and
+about anything else is by prepending a length to every CBOR value, so the
+receiver knows how many octets to read. More compact (and slightly slower)
+would be to just send CBOR values back-to-back, as C<CBOR::XS> knows where
+a CBOR value ends, and doesn't need an explicit length.
+The following methods help with this:
+=over 4
+=item @decoded = $cbor->incr_parse ($buffer)
+This method attempts to decode exactly one CBOR value from the beginning
+of the given C<$buffer>. The value is removed from the C<$buffer> on
+success. When C<$buffer> doesn't contain a complete value yet, it returns
+nothing. Finally, when the C<$buffer> doesn't start with something
+that could ever be a valid CBOR value, it raises an exception, just as
+C<decode> would. In the latter case the decoder state is undefined and
+must be reset before being able to parse further.
+This method modifies the C<$buffer> in place. When no CBOR value can be
+decoded, the decoder stores the current string offset. On the next call,
+continues decoding at the place where it stopped before. For this to make
+sense, the C<$buffer> must begin with the same octets as on previous
+unsuccessful calls.
+You can call this method in scalar context, in which case it either
+returns a decoded value or C<undef>. This makes it impossible to
+distinguish between CBOR null values (which decode to C<undef>) and an
+unsuccessful decode, which is often acceptable.
+=item @decoded = $cbor->incr_parse_multiple ($buffer)
+Same as C<incr_parse>, but attempts to decode as many CBOR values as
+possible in one go, instead of at most one. Calls to C<incr_parse> and
+C<incr_parse_multiple> can be interleaved.
+=item $cbor->incr_reset
+Resets the incremental decoder. This throws away any saved state, so that
+subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse
+a new CBOR value from the beginning of the C<$buffer> again.
+This method can be called at any time, but it I<must> be called if you want
+to change your C<$buffer> or there was a decoding error and you want to
+reuse the C<$cbor> object for future incremental parsings.
 =back
 =head1 MAPPING
 CBOR integers become (numeric) perl scalars. On perls without 64 bit
 support, 64 bit integers will be truncated or otherwise corrupted.
 =item byte strings
-Byte strings will become octet strings in Perl (the byte values 0..255
+Byte strings will become octet strings in Perl (the Byte values 0..255
 will simply become characters of the same value in Perl).
 =item UTF-8 strings
 UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be
 =item tagged values
 Tagged items consists of a numeric tag and another CBOR value.
 See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>
-for details.
+for details on which tags are handled how.
 =item anything else
 Anything else (e.g. unsupported simple values) will raise a decoding
 error.
 =head2 PERL -> CBOR
 The mapping from Perl to CBOR is slightly more difficult, as Perl is a
-truly typeless language, so we can only guess which CBOR type is meant by
+typeless language. That means this module can only guess which CBOR type
-a Perl value.
+is meant by a perl value.
 =over 4
 =item hash references
 Perl hash references become CBOR maps. As there is no inherent ordering in
 hash keys (or CBOR maps), they will usually be encoded in a pseudo-random
-order.
+order. This order can be different each time a hash is encoded.
 Currently, tied hashes will use the indefinite-length format, while normal
 hashes will use the fixed-length format.
 =item array references
 Perl array references become fixed-length CBOR arrays.
 =item other references
-Other unblessed references are generally not allowed and will cause an
+Other unblessed references will be represented using
-exception to be thrown, except for references to the integers C<0> and
+the indirection tag extension (tag value C<22098>,
-C<1>, which get turned into false and true in CBOR.
+L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed
+to be able to decode these values somehow, by either "doing the right
+thing", decoding into a generic tagged object, simply ignoring the tag, or
+something else.
 =item CBOR::XS::Tagged objects
 Objects of this type must be arrays consisting of a single C<[tag, value]>
 pair. The (numerical) tag will be encoded as a CBOR tag, the value will
-be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to
+be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to
 create such objects.
 =item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error
 These special values become CBOR true, CBOR false and CBOR undefined
    # dump as number
    encode_cbor [2]                      # yields [2]
    encode_cbor [-3.0e17]                # yields [-3e+17]
    my $value = 5; encode_cbor [$value]  # yields [5]
-   # used as string, so dump as string
+   # used as string, so dump as string (either byte or text)
    print $value;
    encode_cbor [$value]                 # yields ["5"]
    # undef becomes null
    encode_cbor [undef]                  # yields [null]
    my $x = 3.1; # some variable containing a number
    "$x";        # stringified
    $x .= "";    # another, more awkward way to stringify
    print $x;    # perl does it for you, too, quite often
+You can force whether a string is encoded as byte or text string by using
+C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled):
+  utf8::upgrade $x;   # encode $x as text string
+  utf8::downgrade $x; # encode $x as byte string
+Perl doesn't define what operations up- and downgrade strings, so if the
+difference between byte and text is important, you should up- or downgrade
+your string as late as possible before encoding. You can also force the
+use of CBOR text strings by using C<text_keys> or C<text_strings>.
 You can force the type to be a CBOR number by numifying it:
    my $x = "3"; # some variable containing a string
    $x += 0;     # numify it, ensuring it will be dumped as a number
 =back
 =head2 OBJECT SERIALISATION
+This module implements both a CBOR-specific and the generic
+L<Types::Serialier> object serialisation protocol. The following
+subsections explain both methods.
+=head3 ENCODING
 This module knows two way to serialise a Perl object: The CBOR-specific
 way, and the generic way.
-Whenever the encoder encounters a Perl object that it cnanot serialise
+Whenever the encoder encounters a Perl object that it cannot serialise
 directly (most of them), it will first look up the C<TO_CBOR> method on
 it.
 If it has a C<TO_CBOR> method, it will call it with the object as only
 argument, and expects exactly one return value, which it will then
 The C<FREEZE> method can return any number of values (i.e. zero or
 more). These will be encoded as CBOR perl object, together with the
 classname.
+These methods I<MUST NOT> change the data structure that is being
+serialised. Failure to comply to this can result in memory corruption -
+and worse.
 If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail
 with an error.
+=head3 DECODING
-Objects encoded via C<TO_CBOR> cannot be automatically decoded, but
+Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded,
-objects encoded via C<FREEZE> can be decoded using the following protocol:
+but objects encoded via C<FREEZE> can be decoded using the following
+protocol:
 When an encoded CBOR perl object is encountered by the decoder, it will
 look up the C<THAW> method, by using the stored classname, and will fail
 if the method cannot be found.
 After the lookup it will call the C<THAW> method with the stored classname
 as first argument, the constant string C<CBOR> as second argument, and all
 values returned by C<FREEZE> as remaining arguments.
-=head4 EXAMPLES
+=head3 EXAMPLES
 Here is an example C<TO_CBOR> method:
    sub My::Object::TO_CBOR {
       my ($obj) = @_;
   sub URI::TO_CBOR {
      my ($self) = @_;
      my $uri = "$self"; # stringify uri
      utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string
-     CBOR::XS::tagged 32, "$_[0]"
+     CBOR::XS::tag 32, "$_[0]"
   }
 This will encode URIs as a UTF-8 string with tag 32, which indicates an
 URI.
       "$self" # encode url string
    }
    sub URI::THAW {
       my ($class, $serialiser, $uri) = @_;
       $class->new ($uri)
    }
 Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For
 example, a C<FREEZE> method that returns "type", "id" and "variant" values
 additional tags (such as base64url).
 =head2 ENFORCED TAGS
 These tags are always handled when decoding, and their handling cannot be
-overriden by the user.
+overridden by the user.
 =over 4
-=item <unassigned> (perl-object, L<http://cbor.schmorp.de/perl-object>)
+=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)
 These tags are automatically created (and decoded) for serialisable
 objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object
 serialisation protocol). See L<OBJECT SERIALISATION> for details.
-=item <unassigned>, <unassigned> (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)
+=item 28, 29 (shareable, sharedref, L<http://cbor.schmorp.de/value-sharing>)
-These tags are automatically decoded when encountered, resulting in
+These tags are automatically decoded when encountered (and they do not
+result in a cyclic data structure, see C<allow_cycles>), resulting in
 shared values in the decoded object. They are only encoded, however, when
-C<allow_sharable> is enabled.
+C<allow_sharing> is enabled.
+Not all shared values can be successfully decoded: values that reference
+themselves will I<currently> decode as C<undef> (this is not the same
+as a reference pointing to itself, which will be represented as a value
+that contains an indirect reference to itself - these will be decoded
+properly).
+Note that considerably more shared value data structures can be decoded
+than will be encoded - currently, only values pointed to by references
+will be shared, others will not. While non-reference shared values can be
+generated in Perl with some effort, they were considered too unimportant
+to be supported in the encoder. The decoder, however, will decode these
+values as shared values.
-=item <unassigned>, <unassigned> (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>)
+=item 256, 25 (stringref-namespace, stringref, L<http://cbor.schmorp.de/stringref>)
 These tags are automatically decoded when encountered. They are only
-encoded, however, when C<allow_stringref> is enabled.
+encoded, however, when C<pack_strings> is enabled.
 =item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
 This tag is automatically generated when a reference are encountered (with
-the exception of hash and array refernces). It is converted to a reference
+the exception of hash and array references). It is converted to a reference
 when decoding.
 =item 55799 (self-describe CBOR, RFC 7049)
 This value is not generated on encoding (unless explicitly requested by
 =back
 =head2 NON-ENFORCED TAGS
 These tags have default filters provided when decoding. Their handling can
-be overriden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by
+be overridden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by
 providing a custom C<filter> callback when decoding.
 When they result in decoding into a specific Perl class, the module
 usually provides a corresponding C<TO_CBOR> method as well.
 provide these modules. The decoding usually fails with an exception if the
 required module cannot be loaded.
 =over 4
+=item 0, 1 (date/time string, seconds since the epoch)
+These tags are decoded into L<Time::Piece> objects. The corresponding
+C<Time::Piece::TO_CBOR> method always encodes into tag 1 values currently.
+The L<Time::Piece> API is generally surprisingly bad, and fractional
+seconds are only accidentally kept intact, so watch out. On the plus side,
+the module comes with perl since 5.10, which has to count for something.
 =item 2, 3 (positive/negative bignum)
 These tags are decoded into L<Math::BigInt> objects. The corresponding
 C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
 integers, and others into positive/negative CBOR bignums.
-=item 4, 5 (decimal fraction/bigfloat)
+=item 4, 5, 264, 265 (decimal fraction/bigfloat)
 Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>
 objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
-encodes into a decimal fraction.
+encodes into a decimal fraction (either tag 4 or 264).
-CBOR cannot represent bigfloats with I<very> large exponents - conversion
+NaN and infinities are not encoded properly, as they cannot be represented
-of such big float objects is undefined.
+in CBOR.
-Also, NaN and infinities are not encoded properly.
+See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
+=item 30 (rational numbers)
+These tags are decoded into L<Math::BigRat> objects. The corresponding
+C<Math::BigRat::TO_CBOR> method encodes rational numbers with denominator
+C<1> via their numerator only, i.e., they become normal integers or
+C<bignums>.
+See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
 =item 21, 22, 23 (expected later JSON conversion)
 CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these
 tags.
 C<URI::TO_CBOR> method again results in a CBOR URI value.
 =back
 =cut
-our %FILTER = (
-   # 0 # rfc4287 datetime, utf-8
-   # 1 # unix timestamp, any
-   2 => sub { # pos bigint
-      require Math::BigInt;
-      Math::BigInt->new ("0x" . unpack "H*", pop)
-   },
-   3 => sub { # neg bigint
-      require Math::BigInt;
-      -Math::BigInt->new ("0x" . unpack "H*", pop)
-   },
-   4 => sub { # decimal fraction, array
-      require Math::BigFloat;
-      Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
-   },
-   5 => sub { # bigfloat, array
-      require Math::BigFloat;
-      scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2)
-   },
-   21 => sub { pop }, # expected conversion to base64url encoding
-   22 => sub { pop }, # expected conversion to base64 encoding
-   23 => sub { pop }, # expected conversion to base16 encoding
-   # 24 # embedded cbor, byte string
-   32 => sub {
-      require URI;
-      URI->new (pop)
-   },
-   # 33 # base64url rfc4648, utf-8
-   # 34 # base64 rfc46484, utf-8
-   # 35 # regex pcre/ecma262, utf-8
-   # 36 # mime message rfc2045, utf-8
-);
 =head1 CBOR and JSON
 CBOR is supposed to implement a superset of the JSON data model, and is,
 with some coercion, able to represent all JSON texts (something that other
 First of all, your CBOR decoder should be secure, that is, should not have
 any buffer overflows. Obviously, this module should ensure that and I am
 trying hard on making that true, but you never know.
+Second, CBOR::XS supports object serialisation - decoding CBOR can cause
+calls to I<any> C<THAW> method in I<any> package that exists in your
+process (that is, CBOR::XS will not try to load modules, but any existing
+C<THAW> method or function can be called, so they all have to be secure).
-Second, you need to avoid resource-starving attacks. That means you should
+Third, you need to avoid resource-starving attacks. That means you should
 limit the size of CBOR data you accept, or make sure then when your
 resources run out, that's just fine (e.g. by using a separate process that
 can crash safely). The size of a CBOR string in octets is usually a good
 indication of the size of the resources required to decode it into a Perl
 structure. While CBOR::XS can check the size of the CBOR text, it might be
 too late when you already have it in memory, so you might want to check
 the size before you accept the string.
-Third, CBOR::XS recurses using the C stack when decoding objects and
+Fourth, CBOR::XS recurses using the C stack when decoding objects and
 arrays. The C stack is a limited resource: for instance, on my amd64
 machine with 8MB of stack size I can decode around 180k nested arrays but
 only 14k nested CBOR objects (due to perl itself recursing deeply on croak
 to free the temporary). If that is exceeded, the program crashes. To be
 conservative, the default nesting limit is set to 512. If your process
 Also keep in mind that CBOR::XS might leak contents of your Perl data
 structures in its error messages, so when you serialise sensitive
 information you might want to make sure that exceptions thrown by CBOR::XS
 will not end up in front of untrusted eyes.
+=head1 BIGNUM SECURITY CONSIDERATIONS
+CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and
+L<Math::BigFloat> that tries to encode the number in the simplest possible
+way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
+4) or an arbitrary-exponent decimal fraction (tag 264). Rational numbers
+(L<Math::BigRat>, tag 30) can also contain bignums as members.
+CBOR::XS will also understand base-2 bigfloat or arbitrary-exponent
+bigfloats (tags 5 and 265), but it will never generate these on its own.
+Using the built-in L<Math::BigInt::Calc> support, encoding and decoding
+decimal fractions is generally fast. Decoding bigints can be slow for very
+big numbers (tens of thousands of digits, something that could potentially
+be caught by limiting the size of CBOR texts), and decoding bigfloats or
+arbitrary-exponent bigfloats can be I<extremely> slow (minutes, decades)
+for large exponents (roughly 40 bit and longer).
+Additionally, L<Math::BigInt> can take advantage of other bignum
+libraries, such as L<Math::GMP>, which cannot handle big floats with large
+exponents, and might simply abort or crash your program, due to their code
+quality.
+This can be a concern if you want to parse untrusted CBOR. If it is, you
+might want to disable decoding of tag 2 (bigint) and 3 (negative bigint)
+types. You should also disable types 5 and 265, as these can be slow even
+without bigints.
+Disabling bigints will also partially or fully disable types that rely on
+them, e.g. rational numbers that use bignums.
 =head1 CBOR IMPLEMENTATION NOTES
 This section contains some random implementation notes. They do not
 describe guaranteed behaviour, but merely behaviour as-is implemented
 right now.
 Only the double data type is supported for NV data types - when Perl uses
 long double to represent floating point values, they might not be encoded
 properly. Half precision types are accepted, but not encoded.
 Strict mode and canonical mode are not implemented.
+=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
+On perls that were built without 64 bit integer support (these are rare
+nowadays, even on 32 bit architectures, as all major Perl distributions
+are built with 64 bit integer support), support for any kind of 64 bit
+integer in CBOR is very limited - most likely, these 64 bit values will
+be truncated, corrupted, or otherwise not decoded correctly. This also
+includes string, array and map sizes that are stored as 64 bit integers.
 =head1 THREADS
 This module is I<not> guaranteed to be thread safe and there are no
 Please refrain from using rt.cpan.org or any other bug reporting
 service. I put the contact address into my modules for a reason.
 =cut
+# clumsy hv_store-in-perl
+sub _hv_store {
+   $_[0]{$_[1]} = $_[2];
+}
 our %FILTER = (
-   # 0 # rfc4287 datetime, utf-8
+   0 => sub { # rfc4287 datetime, utf-8
-   # 1 # unix timestamp, any
+      require Time::Piece;
+      # Time::Piece::Strptime uses the "incredibly flexible date parsing routine"
+      # from FreeBSD, which can't parse ISO 8601, RFC3339, RFC4287 or much of anything
+      # else either. Whats incredibe over standard strptime totally escapes me.
+      # doesn't do fractional times, either. sigh.
+      # In fact, it's all a lie, it uses whatever strptime it wants, and of course,
+      # they are all incompatible. The openbsd one simply ignores %z (but according to the
+      # docs, it would be much more incredibly flexible indeed. If it worked, that is.).
+      scalar eval {
+         my $s = $_[1];
+         $s =~ s/Z$/+00:00/;
+         $s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])$//
+            or die;
+         my $b = $1 - ($2 * 60 + $3) * 60; # fractional part + offset. hopefully
+         my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S");
+         Time::Piece::gmtime ($d->epoch + $b)
+      } || die "corrupted CBOR date/time string ($_[0])";
+   },
+   1 => sub { # seconds since the epoch, possibly fractional
+      require Time::Piece;
+      scalar Time::Piece::gmtime (pop)
+   },
    2 => sub { # pos bigint
       require Math::BigInt;
       Math::BigInt->new ("0x" . unpack "H*", pop)
    },
    4 => sub { # decimal fraction, array
       require Math::BigFloat;
       Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
    },
+   264 => sub { # decimal fraction with arbitrary exponent
+      require Math::BigFloat;
+      Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
+   },
    5 => sub { # bigfloat, array
       require Math::BigFloat;
-      scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2)
+      scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
+   },
+   265 => sub { # bigfloat with arbitrary exponent
+      require Math::BigFloat;
+      scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
+   },
+   30 => sub { # rational number
+      require Math::BigRat;
+      Math::BigRat->new ("$_[1][0]/$_[1][1]") # separate parameters only work in recent versons
    },
    21 => sub { pop }, # expected conversion to base64url encoding
    22 => sub { pop }, # expected conversion to base64 encoding
    23 => sub { pop }, # expected conversion to base16 encoding
 }
 sub URI::TO_CBOR {
    my $uri = $_[0]->as_string;
    utf8::upgrade $uri;
-   CBOR::XS::tag 32, $uri
+   tag 32, $uri
 }
 sub Math::BigInt::TO_CBOR {
-   if ($_[0] >= -2147483648 && $_[0] <= 2147483647) {
+   if (-2147483648 <= $_[0] && $_[0] <= 2147483647) {
       $_[0]->numify
    } else {
       my $hex = substr $_[0]->as_hex, 2;
       $hex = "0$hex" if 1 & length $hex; # sigh
-      CBOR::XS::tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
+      tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
    }
 }
 sub Math::BigFloat::TO_CBOR {
    my ($m, $e) = $_[0]->parts;
+   -9223372036854775808 <= $e && $e <= 18446744073709551615
-   CBOR::XS::tag 4, [$e->numify, $m]
+      ? tag 4, [$e->numify, $m]
+      : tag 264, [$e, $m]
+}
+sub Math::BigRat::TO_CBOR {
+   my ($n, $d) = $_[0]->parts;
+   # older versions of BigRat need *1, as they not always return numbers
+   $d*1 == 1
+      ? $n*1
+      : tag 30, [$n*1, $d*1]
+}
+sub Time::Piece::TO_CBOR {
+   tag 1, 0 + $_[0]->epoch
 }
 XSLoader::load "CBOR::XS", $VERSION;
 =head1 SEE ALSO

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Comparing CBOR-XS/XS.pm (file contents): Revision 1.24 by root, Fri Nov 22 16:18:59 2013 UTC vs. Revision 1.64 by root, Fri Nov 25 23:37:27 2016 UTC

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Comparing CBOR-XS/XS.pm (file contents):
Revision 1.24 by root, Fri Nov 22 16:18:59 2013 UTC vs.
Revision 1.64 by root, Fri Nov 25 23:37:27 2016 UTC