… | |
… | |
83 | this module usually compares favourably in terms of speed, too. |
83 | this module usually compares favourably in terms of speed, too. |
84 | |
84 | |
85 | =item * simple to use |
85 | =item * simple to use |
86 | |
86 | |
87 | This module has both a simple functional interface as well as an object |
87 | This module has both a simple functional interface as well as an object |
88 | oriented interface interface. |
88 | oriented interface. |
89 | |
89 | |
90 | =item * reasonably versatile output formats |
90 | =item * reasonably versatile output formats |
91 | |
91 | |
92 | You can choose between the most compact guaranteed-single-line format |
92 | You can choose between the most compact guaranteed-single-line format |
93 | possible (nice for simple line-based protocols), a pure-ASCII format |
93 | possible (nice for simple line-based protocols), a pure-ASCII format |
… | |
… | |
101 | |
101 | |
102 | package JSON::XS; |
102 | package JSON::XS; |
103 | |
103 | |
104 | use common::sense; |
104 | use common::sense; |
105 | |
105 | |
106 | our $VERSION = '2.3'; |
106 | our $VERSION = '3.0'; |
107 | our @ISA = qw(Exporter); |
107 | our @ISA = qw(Exporter); |
108 | |
108 | |
109 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
109 | our @EXPORT = qw(encode_json decode_json); |
110 | |
|
|
111 | sub to_json($) { |
|
|
112 | require Carp; |
|
|
113 | Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call"); |
|
|
114 | } |
|
|
115 | |
|
|
116 | sub from_json($) { |
|
|
117 | require Carp; |
|
|
118 | Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call"); |
|
|
119 | } |
|
|
120 | |
110 | |
121 | use Exporter; |
111 | use Exporter; |
122 | use XSLoader; |
112 | use XSLoader; |
|
|
113 | |
|
|
114 | use Types::Serialiser (); |
123 | |
115 | |
124 | =head1 FUNCTIONAL INTERFACE |
116 | =head1 FUNCTIONAL INTERFACE |
125 | |
117 | |
126 | The following convenience methods are provided by this module. They are |
118 | The following convenience methods are provided by this module. They are |
127 | exported by default: |
119 | exported by default: |
… | |
… | |
148 | This function call is functionally identical to: |
140 | This function call is functionally identical to: |
149 | |
141 | |
150 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
142 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
151 | |
143 | |
152 | Except being faster. |
144 | Except being faster. |
153 | |
|
|
154 | =item $is_boolean = JSON::XS::is_bool $scalar |
|
|
155 | |
|
|
156 | Returns true if the passed scalar represents either JSON::XS::true or |
|
|
157 | JSON::XS::false, two constants that act like C<1> and C<0>, respectively |
|
|
158 | and are used to represent JSON C<true> and C<false> values in Perl. |
|
|
159 | |
|
|
160 | See MAPPING, below, for more information on how JSON values are mapped to |
|
|
161 | Perl. |
|
|
162 | |
145 | |
163 | =back |
146 | =back |
164 | |
147 | |
165 | |
148 | |
166 | =head1 A FEW NOTES ON UNICODE AND PERL |
149 | =head1 A FEW NOTES ON UNICODE AND PERL |
… | |
… | |
432 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
415 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
433 | by sorting their keys. This is adding a comparatively high overhead. |
416 | by sorting their keys. This is adding a comparatively high overhead. |
434 | |
417 | |
435 | If C<$enable> is false, then the C<encode> method will output key-value |
418 | If C<$enable> is false, then the C<encode> method will output key-value |
436 | pairs in the order Perl stores them (which will likely change between runs |
419 | pairs in the order Perl stores them (which will likely change between runs |
437 | of the same script). |
420 | of the same script, and can change even within the same run from 5.18 |
|
|
421 | onwards). |
438 | |
422 | |
439 | This option is useful if you want the same data structure to be encoded as |
423 | This option is useful if you want the same data structure to be encoded as |
440 | the same JSON text (given the same overall settings). If it is disabled, |
424 | the same JSON text (given the same overall settings). If it is disabled, |
441 | the same hash might be encoded differently even if contains the same data, |
425 | the same hash might be encoded differently even if contains the same data, |
442 | as key-value pairs have no inherent ordering in Perl. |
426 | as key-value pairs have no inherent ordering in Perl. |
… | |
… | |
483 | |
467 | |
484 | =item $json = $json->allow_blessed ([$enable]) |
468 | =item $json = $json->allow_blessed ([$enable]) |
485 | |
469 | |
486 | =item $enabled = $json->get_allow_blessed |
470 | =item $enabled = $json->get_allow_blessed |
487 | |
471 | |
|
|
472 | See L<OBJECT SERIALISATION> for details. |
|
|
473 | |
488 | If C<$enable> is true (or missing), then the C<encode> method will not |
474 | If C<$enable> is true (or missing), then the C<encode> method will not |
489 | barf when it encounters a blessed reference. Instead, the value of the |
475 | barf when it encounters a blessed reference that it cannot convert |
490 | B<convert_blessed> option will decide whether C<null> (C<convert_blessed> |
476 | otherwise. Instead, a JSON C<null> value is encoded instead of the object. |
491 | disabled or no C<TO_JSON> method found) or a representation of the |
|
|
492 | object (C<convert_blessed> enabled and C<TO_JSON> method found) is being |
|
|
493 | encoded. Has no effect on C<decode>. |
|
|
494 | |
477 | |
495 | If C<$enable> is false (the default), then C<encode> will throw an |
478 | If C<$enable> is false (the default), then C<encode> will throw an |
496 | exception when it encounters a blessed object. |
479 | exception when it encounters a blessed object that it cannot convert |
|
|
480 | otherwise. |
|
|
481 | |
|
|
482 | This setting has no effect on C<decode>. |
497 | |
483 | |
498 | =item $json = $json->convert_blessed ([$enable]) |
484 | =item $json = $json->convert_blessed ([$enable]) |
499 | |
485 | |
500 | =item $enabled = $json->get_convert_blessed |
486 | =item $enabled = $json->get_convert_blessed |
|
|
487 | |
|
|
488 | See L<OBJECT SERIALISATION> for details. |
501 | |
489 | |
502 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
490 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
503 | blessed object, will check for the availability of the C<TO_JSON> method |
491 | blessed object, will check for the availability of the C<TO_JSON> method |
504 | on the object's class. If found, it will be called in scalar context |
492 | on the object's class. If found, it will be called in scalar context and |
505 | and the resulting scalar will be encoded instead of the object. If no |
493 | the resulting scalar will be encoded instead of the object. |
506 | C<TO_JSON> method is found, the value of C<allow_blessed> will decide what |
|
|
507 | to do. |
|
|
508 | |
494 | |
509 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
495 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
510 | returns other blessed objects, those will be handled in the same |
496 | returns other blessed objects, those will be handled in the same |
511 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
497 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
512 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
498 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
513 | methods called by the Perl core (== not by the user of the object) are |
499 | methods called by the Perl core (== not by the user of the object) are |
514 | usually in upper case letters and to avoid collisions with any C<to_json> |
500 | usually in upper case letters and to avoid collisions with any C<to_json> |
515 | function or method. |
501 | function or method. |
516 | |
502 | |
517 | This setting does not yet influence C<decode> in any way, but in the |
503 | If C<$enable> is false (the default), then C<encode> will not consider |
518 | future, global hooks might get installed that influence C<decode> and are |
504 | this type of conversion. |
519 | enabled by this setting. |
|
|
520 | |
505 | |
521 | If C<$enable> is false, then the C<allow_blessed> setting will decide what |
506 | This setting has no effect on C<decode>. |
522 | to do when a blessed object is found. |
507 | |
|
|
508 | =item $json = $json->allow_tags ([$enable]) |
|
|
509 | |
|
|
510 | =item $enabled = $json->allow_tags |
|
|
511 | |
|
|
512 | See L<OBJECT SERIALISATION> for details. |
|
|
513 | |
|
|
514 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
|
|
515 | blessed object, will check for the availability of the C<FREEZE> method on |
|
|
516 | the object's class. If found, it will be used to serialise the object into |
|
|
517 | a nonstandard tagged JSON value (that JSON decoders cannot decode). |
|
|
518 | |
|
|
519 | It also causes C<decode> to parse such tagged JSON values and deserialise |
|
|
520 | them via a call to the C<THAW> method. |
|
|
521 | |
|
|
522 | If C<$enable> is false (the default), then C<encode> will not consider |
|
|
523 | this type of conversion, and tagged JSON values will cause a parse error |
|
|
524 | in C<decode>, as if tags were not part of the grammar. |
523 | |
525 | |
524 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
526 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
525 | |
527 | |
526 | When C<$coderef> is specified, it will be called from C<decode> each |
528 | When C<$coderef> is specified, it will be called from C<decode> each |
527 | time it decodes a JSON object. The only argument is a reference to the |
529 | time it decodes a JSON object. The only argument is a reference to the |
… | |
… | |
666 | |
668 | |
667 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
669 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
668 | |
670 | |
669 | =item $json_text = $json->encode ($perl_scalar) |
671 | =item $json_text = $json->encode ($perl_scalar) |
670 | |
672 | |
671 | Converts the given Perl data structure (a simple scalar or a reference |
673 | Converts the given Perl value or data structure to its JSON |
672 | to a hash or array) to its JSON representation. Simple scalars will be |
674 | representation. Croaks on error. |
673 | converted into JSON string or number sequences, while references to arrays |
|
|
674 | become JSON arrays and references to hashes become JSON objects. Undefined |
|
|
675 | Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true> |
|
|
676 | nor C<false> values will be generated. |
|
|
677 | |
675 | |
678 | =item $perl_scalar = $json->decode ($json_text) |
676 | =item $perl_scalar = $json->decode ($json_text) |
679 | |
677 | |
680 | The opposite of C<encode>: expects a JSON text and tries to parse it, |
678 | The opposite of C<encode>: expects a JSON text and tries to parse it, |
681 | returning the resulting simple scalar or reference. Croaks on error. |
679 | returning the resulting simple scalar or reference. Croaks on error. |
682 | |
|
|
683 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
|
|
684 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
|
|
685 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
|
|
686 | |
680 | |
687 | =item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
681 | =item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
688 | |
682 | |
689 | This works like the C<decode> method, but instead of raising an exception |
683 | This works like the C<decode> method, but instead of raising an exception |
690 | when there is trailing garbage after the first JSON object, it will |
684 | when there is trailing garbage after the first JSON object, it will |
691 | silently stop parsing there and return the number of characters consumed |
685 | silently stop parsing there and return the number of characters consumed |
692 | so far. |
686 | so far. |
693 | |
687 | |
694 | This is useful if your JSON texts are not delimited by an outer protocol |
688 | This is useful if your JSON texts are not delimited by an outer protocol |
695 | (which is not the brightest thing to do in the first place) and you need |
|
|
696 | to know where the JSON text ends. |
689 | and you need to know where the JSON text ends. |
697 | |
690 | |
698 | JSON::XS->new->decode_prefix ("[1] the tail") |
691 | JSON::XS->new->decode_prefix ("[1] the tail") |
699 | => ([], 3) |
692 | => ([], 3) |
700 | |
693 | |
701 | =back |
694 | =back |
… | |
… | |
740 | |
733 | |
741 | If the method is called in scalar context, then it will try to extract |
734 | If the method is called in scalar context, then it will try to extract |
742 | exactly I<one> JSON object. If that is successful, it will return this |
735 | exactly I<one> JSON object. If that is successful, it will return this |
743 | object, otherwise it will return C<undef>. If there is a parse error, |
736 | object, otherwise it will return C<undef>. If there is a parse error, |
744 | this method will croak just as C<decode> would do (one can then use |
737 | this method will croak just as C<decode> would do (one can then use |
745 | C<incr_skip> to skip the errornous part). This is the most common way of |
738 | C<incr_skip> to skip the erroneous part). This is the most common way of |
746 | using the method. |
739 | using the method. |
747 | |
740 | |
748 | And finally, in list context, it will try to extract as many objects |
741 | And finally, in list context, it will try to extract as many objects |
749 | from the stream as it can find and return them, or the empty list |
742 | from the stream as it can find and return them, or the empty list |
750 | otherwise. For this to work, there must be no separators between the JSON |
743 | otherwise. For this to work, there must be no separators between the JSON |
… | |
… | |
779 | C<incr_parse> died, in which case the input buffer and incremental parser |
772 | C<incr_parse> died, in which case the input buffer and incremental parser |
780 | state is left unchanged, to skip the text parsed so far and to reset the |
773 | state is left unchanged, to skip the text parsed so far and to reset the |
781 | parse state. |
774 | parse state. |
782 | |
775 | |
783 | The difference to C<incr_reset> is that only text until the parse error |
776 | The difference to C<incr_reset> is that only text until the parse error |
784 | occured is removed. |
777 | occurred is removed. |
785 | |
778 | |
786 | =item $json->incr_reset |
779 | =item $json->incr_reset |
787 | |
780 | |
788 | This completely resets the incremental parser, that is, after this call, |
781 | This completely resets the incremental parser, that is, after this call, |
789 | it will be as if the parser had never parsed anything. |
782 | it will be as if the parser had never parsed anything. |
… | |
… | |
795 | =back |
788 | =back |
796 | |
789 | |
797 | =head2 LIMITATIONS |
790 | =head2 LIMITATIONS |
798 | |
791 | |
799 | All options that affect decoding are supported, except |
792 | All options that affect decoding are supported, except |
800 | C<allow_nonref>. The reason for this is that it cannot be made to |
793 | C<allow_nonref>. The reason for this is that it cannot be made to work |
801 | work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate |
794 | sensibly: JSON objects and arrays are self-delimited, i.e. you can |
802 | them back to back and still decode them perfectly. This does not hold true |
795 | concatenate them back to back and still decode them perfectly. This does |
803 | for JSON numbers, however. |
796 | not hold true for JSON numbers, however. |
804 | |
797 | |
805 | For example, is the string C<1> a single JSON number, or is it simply the |
798 | For example, is the string C<1> a single JSON number, or is it simply the |
806 | start of C<12>? Or is C<12> a single JSON number, or the concatenation |
799 | start of C<12>? Or is C<12> a single JSON number, or the concatenation |
807 | of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS |
800 | of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS |
808 | takes the conservative route and disallows this case. |
801 | takes the conservative route and disallows this case. |
… | |
… | |
987 | If the number consists of digits only, JSON::XS will try to represent |
980 | If the number consists of digits only, JSON::XS will try to represent |
988 | it as an integer value. If that fails, it will try to represent it as |
981 | it as an integer value. If that fails, it will try to represent it as |
989 | a numeric (floating point) value if that is possible without loss of |
982 | a numeric (floating point) value if that is possible without loss of |
990 | precision. Otherwise it will preserve the number as a string value (in |
983 | precision. Otherwise it will preserve the number as a string value (in |
991 | which case you lose roundtripping ability, as the JSON number will be |
984 | which case you lose roundtripping ability, as the JSON number will be |
992 | re-encoded toa JSON string). |
985 | re-encoded to a JSON string). |
993 | |
986 | |
994 | Numbers containing a fractional or exponential part will always be |
987 | Numbers containing a fractional or exponential part will always be |
995 | represented as numeric (floating point) values, possibly at a loss of |
988 | represented as numeric (floating point) values, possibly at a loss of |
996 | precision (in which case you might lose perfect roundtripping ability, but |
989 | precision (in which case you might lose perfect roundtripping ability, but |
997 | the JSON number will still be re-encoded as a JSON number). |
990 | the JSON number will still be re-encoded as a JSON number). |
998 | |
991 | |
999 | Note that precision is not accuracy - binary floating point values cannot |
992 | Note that precision is not accuracy - binary floating point values cannot |
1000 | represent most decimal fractions exactly, and when converting from and to |
993 | represent most decimal fractions exactly, and when converting from and to |
1001 | floating point, JSON::XS only guarantees precision up to but not including |
994 | floating point, JSON::XS only guarantees precision up to but not including |
1002 | the leats significant bit. |
995 | the least significant bit. |
1003 | |
996 | |
1004 | =item true, false |
997 | =item true, false |
1005 | |
998 | |
1006 | These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, |
999 | These JSON atoms become C<Types::Serialiser::true> and |
1007 | respectively. They are overloaded to act almost exactly like the numbers |
1000 | C<Types::Serialiser::false>, respectively. They are overloaded to act |
1008 | C<1> and C<0>. You can check whether a scalar is a JSON boolean by using |
1001 | almost exactly like the numbers C<1> and C<0>. You can check whether |
1009 | the C<JSON::XS::is_bool> function. |
1002 | a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool> |
|
|
1003 | function (after C<use Types::Serialier>, of course). |
1010 | |
1004 | |
1011 | =item null |
1005 | =item null |
1012 | |
1006 | |
1013 | A JSON null atom becomes C<undef> in Perl. |
1007 | A JSON null atom becomes C<undef> in Perl. |
|
|
1008 | |
|
|
1009 | =item shell-style comments (C<< # I<text> >>) |
|
|
1010 | |
|
|
1011 | As a nonstandard extension to the JSON syntax that is enabled by the |
|
|
1012 | C<relaxed> setting, shell-style comments are allowed. They can start |
|
|
1013 | anywhere outside strings and go till the end of the line. |
|
|
1014 | |
|
|
1015 | =item tagged values (C<< (I<tag>)I<value> >>). |
|
|
1016 | |
|
|
1017 | Another nonstandard extension to the JSON syntax, enabled with the |
|
|
1018 | C<allow_tags> setting, are tagged values. In this implementation, the |
|
|
1019 | I<tag> must be a perl package/class name encoded as a JSON string, and the |
|
|
1020 | I<value> must be a JSON array encoding optional constructor arguments. |
|
|
1021 | |
|
|
1022 | See L<OBJECT SERIALISATION>, below, for details. |
1014 | |
1023 | |
1015 | =back |
1024 | =back |
1016 | |
1025 | |
1017 | |
1026 | |
1018 | =head2 PERL -> JSON |
1027 | =head2 PERL -> JSON |
… | |
… | |
1023 | |
1032 | |
1024 | =over 4 |
1033 | =over 4 |
1025 | |
1034 | |
1026 | =item hash references |
1035 | =item hash references |
1027 | |
1036 | |
1028 | Perl hash references become JSON objects. As there is no inherent ordering |
1037 | Perl hash references become JSON objects. As there is no inherent |
1029 | in hash keys (or JSON objects), they will usually be encoded in a |
1038 | ordering in hash keys (or JSON objects), they will usually be encoded |
1030 | pseudo-random order that can change between runs of the same program but |
1039 | in a pseudo-random order. JSON::XS can optionally sort the hash keys |
1031 | stays generally the same within a single run of a program. JSON::XS can |
1040 | (determined by the I<canonical> flag), so the same datastructure will |
1032 | optionally sort the hash keys (determined by the I<canonical> flag), so |
1041 | serialise to the same JSON text (given same settings and version of |
1033 | the same datastructure will serialise to the same JSON text (given same |
1042 | JSON::XS), but this incurs a runtime overhead and is only rarely useful, |
1034 | settings and version of JSON::XS), but this incurs a runtime overhead |
1043 | e.g. when you want to compare some JSON text against another for equality. |
1035 | and is only rarely useful, e.g. when you want to compare some JSON text |
|
|
1036 | against another for equality. |
|
|
1037 | |
1044 | |
1038 | =item array references |
1045 | =item array references |
1039 | |
1046 | |
1040 | Perl array references become JSON arrays. |
1047 | Perl array references become JSON arrays. |
1041 | |
1048 | |
1042 | =item other references |
1049 | =item other references |
1043 | |
1050 | |
1044 | Other unblessed references are generally not allowed and will cause an |
1051 | Other unblessed references are generally not allowed and will cause an |
1045 | exception to be thrown, except for references to the integers C<0> and |
1052 | exception to be thrown, except for references to the integers C<0> and |
1046 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
1053 | C<1>, which get turned into C<false> and C<true> atoms in JSON. |
1047 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
|
|
1048 | |
1054 | |
|
|
1055 | Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you |
|
|
1056 | can also C<use Types::Serialiser> and then use C<Types::Serialiser::false> |
|
|
1057 | and C<Types::Serialiser::true> to improve readability. |
|
|
1058 | |
|
|
1059 | use Types::Serialiser; |
1049 | encode_json [\0, JSON::XS::true] # yields [false,true] |
1060 | encode_json [\0, Types::Serialiser::true] # yields [false,true] |
1050 | |
1061 | |
1051 | =item JSON::XS::true, JSON::XS::false |
1062 | =item Types::Serialiser::true, Types::Serialiser::false |
1052 | |
1063 | |
1053 | These special values become JSON true and JSON false values, |
1064 | These special values from the L<Types::Serialiser> module become JSON true |
1054 | respectively. You can also use C<\1> and C<\0> directly if you want. |
1065 | and JSON false values, respectively. You can also use C<\1> and C<\0> |
|
|
1066 | directly if you want. |
1055 | |
1067 | |
1056 | =item blessed objects |
1068 | =item blessed objects |
1057 | |
1069 | |
1058 | Blessed objects are not directly representable in JSON. See the |
1070 | Blessed objects are not directly representable in JSON, but C<JSON::XS> |
1059 | C<allow_blessed> and C<convert_blessed> methods on various options on |
1071 | allows various ways of handling objects. See L<OBJECT SERIALISATION>, |
1060 | how to deal with this: basically, you can choose between throwing an |
1072 | below, for details. |
1061 | exception, encoding the reference as if it weren't blessed, or provide |
|
|
1062 | your own serialiser method. |
|
|
1063 | |
1073 | |
1064 | =item simple scalars |
1074 | =item simple scalars |
1065 | |
1075 | |
1066 | Simple Perl scalars (any scalar that is not a reference) are the most |
1076 | Simple Perl scalars (any scalar that is not a reference) are the most |
1067 | difficult objects to encode: JSON::XS will encode undefined scalars as |
1077 | difficult objects to encode: JSON::XS will encode undefined scalars as |
… | |
… | |
1104 | infinities or NaN's - these cannot be represented in JSON, and it is an |
1114 | infinities or NaN's - these cannot be represented in JSON, and it is an |
1105 | error to pass those in. |
1115 | error to pass those in. |
1106 | |
1116 | |
1107 | =back |
1117 | =back |
1108 | |
1118 | |
|
|
1119 | =head2 OBJECT SERIALISATION |
|
|
1120 | |
|
|
1121 | As JSON cannot directly represent Perl objects, you have to choose between |
|
|
1122 | a pure JSON representation (without the ability to deserialise the object |
|
|
1123 | automatically again), and a nonstandard extension to the JSON syntax, |
|
|
1124 | tagged values. |
|
|
1125 | |
|
|
1126 | =head3 SERIALISATION |
|
|
1127 | |
|
|
1128 | What happens when C<JSON::XS> encounters a Perl object depends on the |
|
|
1129 | C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are |
|
|
1130 | used in this order: |
|
|
1131 | |
|
|
1132 | =over 4 |
|
|
1133 | |
|
|
1134 | =item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method. |
|
|
1135 | |
|
|
1136 | In this case, C<JSON::XS> uses the L<Types::Serialiser> object |
|
|
1137 | serialisation protocol to create a tagged JSON value, using a nonstandard |
|
|
1138 | extension to the JSON syntax. |
|
|
1139 | |
|
|
1140 | This works by invoking the C<FREEZE> method on the object, with the first |
|
|
1141 | argument being the object to serialise, and the second argument being the |
|
|
1142 | constant string C<JSON> to distinguish it from other serialisers. |
|
|
1143 | |
|
|
1144 | The C<FREEZE> method can return any number of values (i.e. zero or |
|
|
1145 | more). These values and the paclkage/classname of the object will then be |
|
|
1146 | encoded as a tagged JSON value in the following format: |
|
|
1147 | |
|
|
1148 | ("classname")[FREEZE return values...] |
|
|
1149 | |
|
|
1150 | For example, the hypothetical C<My::Object> C<FREEZE> method might use the |
|
|
1151 | objects C<type> and C<id> members to encode the object: |
|
|
1152 | |
|
|
1153 | sub My::Object::FREEZE { |
|
|
1154 | my ($self, $serialiser) = @_; |
|
|
1155 | |
|
|
1156 | ($self->{type}, $self->{id}) |
|
|
1157 | } |
|
|
1158 | |
|
|
1159 | =item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method. |
|
|
1160 | |
|
|
1161 | In this case, the C<TO_JSON> method of the object is invoked in scalar |
|
|
1162 | context. It must return a single scalar that can be directly encoded into |
|
|
1163 | JSON. This scalar replaces the object in the JSON text. |
|
|
1164 | |
|
|
1165 | For example, the following C<TO_JSON> method will convert all L<URI> |
|
|
1166 | objects to JSON strings when serialised. The fatc that these values |
|
|
1167 | originally were L<URI> objects is lost. |
|
|
1168 | |
|
|
1169 | sub URI::TO_JSON { |
|
|
1170 | my ($uri) = @_; |
|
|
1171 | $uri->as_string |
|
|
1172 | } |
|
|
1173 | |
|
|
1174 | =item 3. C<allow_blessed> is enabled. |
|
|
1175 | |
|
|
1176 | The object will be serialised as a JSON null value. |
|
|
1177 | |
|
|
1178 | =item 4. none of the above |
|
|
1179 | |
|
|
1180 | If none of the settings are enabled or the respective methods are missing, |
|
|
1181 | C<JSON::XS> throws an exception. |
|
|
1182 | |
|
|
1183 | =back |
|
|
1184 | |
|
|
1185 | =head3 DESERIALISATION |
|
|
1186 | |
|
|
1187 | For deserialisation there are only two cases to consider: either |
|
|
1188 | nonstandard tagging was used, in which case C<allow_tags> decides, |
|
|
1189 | or objects cannot be automatically be deserialised, in which |
|
|
1190 | case you can use postprocessing or the C<filter_json_object> or |
|
|
1191 | C<filter_json_single_key_object> callbacks to get some real objects our of |
|
|
1192 | your JSON. |
|
|
1193 | |
|
|
1194 | This section only considers the tagged value case: I a tagged JSON object |
|
|
1195 | is encountered during decoding and C<allow_tags> is disabled, a parse |
|
|
1196 | error will result (as if tagged values were not part of the grammar). |
|
|
1197 | |
|
|
1198 | If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method |
|
|
1199 | of the package/classname used during serialisation (it will not attempt |
|
|
1200 | to load the package as a Perl module). If there is no such method, the |
|
|
1201 | decoding will fail with an error. |
|
|
1202 | |
|
|
1203 | Otherwise, the C<THAW> method is invoked with the classname as first |
|
|
1204 | argument, the constant string C<JSON> as second argument, and all the |
|
|
1205 | values from the JSON array (the values originally returned by the |
|
|
1206 | C<FREEZE> method) as remaining arguments. |
|
|
1207 | |
|
|
1208 | The method must then return the object. While technically you can return |
|
|
1209 | any Perl scalar, you might have to enable the C<enable_nonref> setting to |
|
|
1210 | make that work in all cases, so better return an actual blessed reference. |
|
|
1211 | |
|
|
1212 | As an example, let's implement a C<THAW> function that regenerates the |
|
|
1213 | C<My::Object> from the C<FREEZE> example earlier: |
|
|
1214 | |
|
|
1215 | sub My::Object::THAW { |
|
|
1216 | my ($class, $serialiser, $type, $id) = @_; |
|
|
1217 | |
|
|
1218 | $class->new (type => $type, id => $id) |
|
|
1219 | } |
|
|
1220 | |
1109 | |
1221 | |
1110 | =head1 ENCODING/CODESET FLAG NOTES |
1222 | =head1 ENCODING/CODESET FLAG NOTES |
1111 | |
1223 | |
1112 | The interested reader might have seen a number of flags that signify |
1224 | The interested reader might have seen a number of flags that signify |
1113 | encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be |
1225 | encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be |
… | |
… | |
1137 | =item C<utf8> flag disabled |
1249 | =item C<utf8> flag disabled |
1138 | |
1250 | |
1139 | When C<utf8> is disabled (the default), then C<encode>/C<decode> generate |
1251 | When C<utf8> is disabled (the default), then C<encode>/C<decode> generate |
1140 | and expect Unicode strings, that is, characters with high ordinal Unicode |
1252 | and expect Unicode strings, that is, characters with high ordinal Unicode |
1141 | values (> 255) will be encoded as such characters, and likewise such |
1253 | values (> 255) will be encoded as such characters, and likewise such |
1142 | characters are decoded as-is, no canges to them will be done, except |
1254 | characters are decoded as-is, no changes to them will be done, except |
1143 | "(re-)interpreting" them as Unicode codepoints or Unicode characters, |
1255 | "(re-)interpreting" them as Unicode codepoints or Unicode characters, |
1144 | respectively (to Perl, these are the same thing in strings unless you do |
1256 | respectively (to Perl, these are the same thing in strings unless you do |
1145 | funny/weird/dumb stuff). |
1257 | funny/weird/dumb stuff). |
1146 | |
1258 | |
1147 | This is useful when you want to do the encoding yourself (e.g. when you |
1259 | This is useful when you want to do the encoding yourself (e.g. when you |
… | |
… | |
1263 | output for these property strings, e.g.: |
1375 | output for these property strings, e.g.: |
1264 | |
1376 | |
1265 | $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; |
1377 | $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; |
1266 | |
1378 | |
1267 | This works because C<__proto__> is not valid outside of strings, so every |
1379 | This works because C<__proto__> is not valid outside of strings, so every |
1268 | occurence of C<"__proto__"\s*:> must be a string used as property name. |
1380 | occurrence of C<"__proto__"\s*:> must be a string used as property name. |
1269 | |
1381 | |
1270 | If you know of other incompatibilities, please let me know. |
1382 | If you know of other incompatibilities, please let me know. |
1271 | |
1383 | |
1272 | |
1384 | |
1273 | =head2 JSON and YAML |
1385 | =head2 JSON and YAML |
… | |
… | |
1435 | are browser design bugs, but it is still you who will have to deal with |
1547 | are browser design bugs, but it is still you who will have to deal with |
1436 | it, as major browser developers care only for features, not about getting |
1548 | it, as major browser developers care only for features, not about getting |
1437 | security right). |
1549 | security right). |
1438 | |
1550 | |
1439 | |
1551 | |
|
|
1552 | =head1 INTEROPERABILITY WITH OTHER MODULES |
|
|
1553 | |
|
|
1554 | C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean |
|
|
1555 | constants. That means that the JSON true and false values will be |
|
|
1556 | comaptible to true and false values of iother modules that do the same, |
|
|
1557 | such as L<JSON::PP> and L<CBOR::XS>. |
|
|
1558 | |
|
|
1559 | |
1440 | =head1 THREADS |
1560 | =head1 THREADS |
1441 | |
1561 | |
1442 | This module is I<not> guaranteed to be thread safe and there are no |
1562 | This module is I<not> guaranteed to be thread safe and there are no |
1443 | plans to change this until Perl gets thread support (as opposed to the |
1563 | plans to change this until Perl gets thread support (as opposed to the |
1444 | horribly slow so-called "threads" which are simply slow and bloated |
1564 | horribly slow so-called "threads" which are simply slow and bloated |
1445 | process simulations - use fork, it's I<much> faster, cheaper, better). |
1565 | process simulations - use fork, it's I<much> faster, cheaper, better). |
1446 | |
1566 | |
1447 | (It might actually work, but you have been warned). |
1567 | (It might actually work, but you have been warned). |
1448 | |
1568 | |
1449 | |
1569 | |
|
|
1570 | =head1 THE PERILS OF SETLOCALE |
|
|
1571 | |
|
|
1572 | Sometimes people avoid the Perl locale support and directly call the |
|
|
1573 | system's setlocale function with C<LC_ALL>. |
|
|
1574 | |
|
|
1575 | This breaks both perl and modules such as JSON::XS, as stringification of |
|
|
1576 | numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might |
|
|
1577 | print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on |
|
|
1578 | perl to stringify numbers). |
|
|
1579 | |
|
|
1580 | The solution is simple: don't call C<setlocale>, or use it for only those |
|
|
1581 | categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>. |
|
|
1582 | |
|
|
1583 | If you need C<LC_NUMERIC>, you should enable it only around the code that |
|
|
1584 | actually needs it (avoiding stringification of numbers), and restore it |
|
|
1585 | afterwards. |
|
|
1586 | |
|
|
1587 | |
1450 | =head1 BUGS |
1588 | =head1 BUGS |
1451 | |
1589 | |
1452 | While the goal of this module is to be correct, that unfortunately does |
1590 | While the goal of this module is to be correct, that unfortunately does |
1453 | not mean it's bug-free, only that I think its design is bug-free. If you |
1591 | not mean it's bug-free, only that I think its design is bug-free. If you |
1454 | keep reporting bugs they will be fixed swiftly, though. |
1592 | keep reporting bugs they will be fixed swiftly, though. |
… | |
… | |
1456 | Please refrain from using rt.cpan.org or any other bug reporting |
1594 | Please refrain from using rt.cpan.org or any other bug reporting |
1457 | service. I put the contact address into my modules for a reason. |
1595 | service. I put the contact address into my modules for a reason. |
1458 | |
1596 | |
1459 | =cut |
1597 | =cut |
1460 | |
1598 | |
1461 | our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; |
1599 | BEGIN { |
1462 | our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; |
1600 | *true = \$Types::Serialiser::true; |
|
|
1601 | *true = \&Types::Serialiser::true; |
|
|
1602 | *false = \$Types::Serialiser::false; |
|
|
1603 | *false = \&Types::Serialiser::false; |
|
|
1604 | *is_bool = \&Types::Serialiser::is_bool; |
1463 | |
1605 | |
1464 | sub true() { $true } |
1606 | *JSON::XS::Boolean:: = *Types::Serialiser::Boolean::; |
1465 | sub false() { $false } |
|
|
1466 | |
|
|
1467 | sub is_bool($) { |
|
|
1468 | UNIVERSAL::isa $_[0], "JSON::XS::Boolean" |
|
|
1469 | # or UNIVERSAL::isa $_[0], "JSON::Literal" |
|
|
1470 | } |
1607 | } |
1471 | |
1608 | |
1472 | XSLoader::load "JSON::XS", $VERSION; |
1609 | XSLoader::load "JSON::XS", $VERSION; |
1473 | |
|
|
1474 | package JSON::XS::Boolean; |
|
|
1475 | |
|
|
1476 | use overload |
|
|
1477 | "0+" => sub { ${$_[0]} }, |
|
|
1478 | "++" => sub { $_[0] = ${$_[0]} + 1 }, |
|
|
1479 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
|
|
1480 | fallback => 1; |
|
|
1481 | |
|
|
1482 | 1; |
|
|
1483 | |
1610 | |
1484 | =head1 SEE ALSO |
1611 | =head1 SEE ALSO |
1485 | |
1612 | |
1486 | The F<json_xs> command line utility for quick experiments. |
1613 | The F<json_xs> command line utility for quick experiments. |
1487 | |
1614 | |
… | |
… | |
1490 | Marc Lehmann <schmorp@schmorp.de> |
1617 | Marc Lehmann <schmorp@schmorp.de> |
1491 | http://home.schmorp.de/ |
1618 | http://home.schmorp.de/ |
1492 | |
1619 | |
1493 | =cut |
1620 | =cut |
1494 | |
1621 | |
|
|
1622 | 1 |
|
|
1623 | |