--- CBOR-XS/XS.pm 2013/11/22 16:00:30 1.23 +++ CBOR-XS/XS.pm 2013/11/28 15:43:24 1.27 @@ -58,7 +58,7 @@ In addition to the core CBOR data format, this module implements a number of extensions, to support cyclic and self-referencing data structures -(see C), string deduplication (see C) and +(see C), string deduplication (see C) and scalar references (always enabled). The primary goal of this module is to be I and the secondary goal @@ -73,7 +73,7 @@ use common::sense; -our $VERSION = 0.08; +our $VERSION = 0.09; our @ISA = qw(Exporter); our @EXPORT = qw(encode_cbor decode_cbor); @@ -188,11 +188,13 @@ This means that such values will only be encoded once, and will not result in a deep cloning of the value on decode, in decoders supporting the value -sharing extension. +sharing extension. This also makes it possible to encode cyclic data +structures. It is recommended to leave it off unless you know your communication partner supports the value sharing extensions to CBOR -(http://cbor.schmorp.de/value-sharing). +(L), as without decoder support, the +resulting data structure might be unusable. Detecting shared values incurs a runtime overhead when values are encoded that have a reference counter large than one, and might unnecessarily @@ -203,30 +205,32 @@ arrays or hashes pointed to by a reference). Weirder constructs, such as an array with multiple "copies" of the I string, which are hard but not impossible to create in Perl, are not supported (this is the same as -for L). +with L). -If C<$enable> is false (the default), then C will encode -exception when it encounters anything it cannot encode as CBOR. +If C<$enable> is false (the default), then C will encode shared +data structures repeatedly, unsharing them in the process. Cyclic data +structures cannot be encoded in this mode. This option does not affect C in any way - shared values and references will always be decoded 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 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), as without decoder support, the +resulting data structure might not be usable. -If C<$enable> is false (the default), then C will encode -exception when it encounters anything it cannot encode as CBOR. +If C<$enable> is false (the default), then C will encode strings +the standard CBOR way. This option does not affect C in any way - string references will always be decoded properly if present. @@ -235,7 +239,42 @@ =item $cb_or_undef = $cbor->get_filter -TODO +Sets or replaces the tagged value decoding filter (when C<$cb> is +specified) or clears the filter (if no argument or C is provided). + +The filter callback is called only during decoding, when a non-enforced +tagged value has been decoded (see L for a +list of enforced tags). For specific tags, it's often better to provide a +default converter using the C<%CBOR::XS::FILTER> hash (see below). + +The first argument is the numerical tag, the second is the (decoded) value +that has been tagged. + +The filter function should return either exactly one value, which will +replace the tagged value in the decoded data structure, or no values, +which will result in default handling, which currently means the decoder +creates a C object to hold the tag and the value. + +When the filter is cleared (the default state), the default filter +function, C, 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 +objects, with no other special handling (useful when working with +potentially "unsafe" CBOR data). + + CBOR::XS->new->filter (sub { })->decode ($cbor_data); + +Example: provide a global filter for tag 1347375694, converting the value +into some string form. + + $CBOR::XS::FILTER{1347375694} = sub { + my ($tag, $value); + + "tag 1347375694 value $value" + }; =item $cbor_data = $cbor->encode ($perl_scalar) @@ -286,7 +325,7 @@ =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 @@ -387,7 +426,7 @@ 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"] @@ -401,6 +440,16 @@ $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 +C and C): + + 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 force the type to be a CBOR number by numifying it: my $x = "3"; # some variable containing a string @@ -642,22 +691,22 @@ =over 4 -=item (perl-object, L) +=item 26 (perl-object, L) These tags are automatically created (and decoded) for serialisable objects using the C methods (the L object serialisation protocol). See L for details. -=item , (sharable, sharedref, L ) +=item 28, 29 (sharable, sharedref, L ) These tags are automatically decoded when encountered, resulting in shared values in the decoded object. They are only encoded, however, when C is enabled. -=item , (stringref-namespace, stringref, L ) +=item 256, 25 (stringref-namespace, stringref, L ) These tags are automatically decoded when encountered. They are only -encoded, however, when C is enabled. +encoded, however, when C is enabled. =item 22098 (indirection, L) @@ -672,11 +721,11 @@ =back -=head2 OPTIONAL TAGS +=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 -providing a custom C function when decoding. +providing a custom C callback when decoding. When they result in decoding into a specific Perl class, the module usually provides a corresponding C method as well.