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

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.30 by root, Sat Nov 30 16:19:59 2013 UTC vs.
Revision 1.56 by root, Mon Apr 25 21:44:13 2016 UTC

 Regarding compactness, C<CBOR::XS>-encoded data structures are usually
 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 of extensions, to support cyclic and shared data structures (see
+number of extensions, to support cyclic and shared data structures
-C<allow_sharing>), string deduplication (see C<pack_strings>) and scalar
+(see C<allow_sharing> and C<allow_cycles>), string deduplication (see
-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 = '1.0';
+our $VERSION = 1.5;
 our @ISA = qw(Exporter);
 our @EXPORT = qw(encode_cbor decode_cbor);
 use Exporter;
 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. This also makes it possible to encode cyclic data
-structures.
+structures (which need C<allow_cycles> to ne 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
 (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
 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 = $cbor->pack_strings ([$enable])
 =item $enabled = $cbor->get_pack_strings
 If C<$enable> is true (or missing), then C<encode> will try not to encode
 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 = $cbor->get_filter
 Sets or replaces the tagged value decoding filter (when C<$cb> is
    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 caled 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
 This section describes how CBOR::XS maps Perl values to CBOR values and
 vice versa. These mappings are designed to "do the right thing" in most
 =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. This order can be different each time a hahs is encoded.
+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
    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 ie encoded as byte or text string by using
+You can force whether a string is encoded as byte or text string by using
-C<utf8::upgrade> and C<utf8::downgrade>):
+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.
+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
    $x += 0;     # numify it, ensuring it will be dumped as a number
       "$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 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 28, 29 (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 256, 25 (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<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 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
 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).
+It 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, and decoding bigfloats or arbitrary-exponent bigfloats can be
+extremely slow (minutes, decades) for large exponents.
+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
+need to disable decoding of tag 2 (bigint) and 3 (negative bigint) types,
+which will also disable bigfloat support (to be sure, you can also disable
+types 4, 5, 264 and 265).
 =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.
 =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), support for any kind of 64 bit
+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.
 service. I put the contact address into my modules for a reason.
 =cut
 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)
+      Math::BigInt->from_hex ("0x" . unpack "H*", pop)
    },
    3 => sub { # neg bigint
       require Math::BigInt;
-      -Math::BigInt->new ("0x" . unpack "H*", pop)
+      -Math::BigInt->from_hex ("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 ($_[1][0], 2)
+      scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
    },
    21 => sub { pop }, # expected conversion to base64url encoding
    22 => sub { pop }, # expected conversion to base64 encoding
    23 => sub { pop }, # expected conversion to base16 encoding
    # 33 # base64url rfc4648, utf-8
    # 34 # base64 rfc46484, utf-8
    # 35 # regex pcre/ecma262, utf-8
    # 36 # mime message rfc2045, utf-8
+   264 => sub { # decimal fraction with arbitrary exponent
+      require Math::BigFloat;
+      Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
+   },
+   265 => sub { # bigfloat with arbitrary exponent
+      require Math::BigFloat;
+      scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
+   },
 );
 sub CBOR::XS::default_filter {
    &{ $FILTER{$_[0]} or return }
 }
 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 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 1.30 by root, Sat Nov 30 16:19:59 2013 UTC vs. Revision 1.56 by root, Mon Apr 25 21:44:13 2016 UTC

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Comparing CBOR-XS/XS.pm (file contents):
Revision 1.30 by root, Sat Nov 30 16:19:59 2013 UTC vs.
Revision 1.56 by root, Mon Apr 25 21:44:13 2016 UTC