… | |
… | |
91 | This function call is functionally identical to: |
91 | This function call is functionally identical to: |
92 | |
92 | |
93 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
93 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
94 | |
94 | |
95 | except being faster. |
95 | except being faster. |
|
|
96 | |
|
|
97 | $is_boolean = JSON::XS::is_bool $scalar |
|
|
98 | Returns true if the passed scalar represents either JSON::XS::true |
|
|
99 | or JSON::XS::false, two constants that act like 1 and 0, |
|
|
100 | respectively and are used to represent JSON "true" and "false" |
|
|
101 | values in Perl. |
|
|
102 | |
|
|
103 | See MAPPING, below, for more information on how JSON values are |
|
|
104 | mapped to Perl. |
96 | |
105 | |
97 | OBJECT-ORIENTED INTERFACE |
106 | OBJECT-ORIENTED INTERFACE |
98 | The object oriented interface lets you configure your own encoding or |
107 | The object oriented interface lets you configure your own encoding or |
99 | decoding style, within the limits of supported formats. |
108 | decoding style, within the limits of supported formats. |
100 | |
109 | |
… | |
… | |
379 | all the conversion details, but an integer may take slightly less |
388 | all the conversion details, but an integer may take slightly less |
380 | memory and might represent more values exactly than (floating point) |
389 | memory and might represent more values exactly than (floating point) |
381 | numbers. |
390 | numbers. |
382 | |
391 | |
383 | true, false |
392 | true, false |
384 | These JSON atoms become 0, 1, respectively. Information is lost in |
393 | These JSON atoms become "JSON::XS::true" and "JSON::XS::false", |
385 | this process. Future versions might represent those values |
394 | respectively. They are overloaded to act almost exactly like the |
386 | differently, but they will be guarenteed to act like these integers |
395 | numbers 1 and 0. You can check wether a scalar is a JSON boolean by |
387 | would normally in Perl. |
396 | using the "JSON::XS::is_bool" function. |
388 | |
397 | |
389 | null |
398 | null |
390 | A JSON null atom becomes "undef" in Perl. |
399 | A JSON null atom becomes "undef" in Perl. |
391 | |
400 | |
392 | PERL -> JSON |
401 | PERL -> JSON |
… | |
… | |
416 | can also use "JSON::XS::false" and "JSON::XS::true" to improve |
425 | can also use "JSON::XS::false" and "JSON::XS::true" to improve |
417 | readability. |
426 | readability. |
418 | |
427 | |
419 | to_json [\0,JSON::XS::true] # yields [false,true] |
428 | to_json [\0,JSON::XS::true] # yields [false,true] |
420 | |
429 | |
|
|
430 | JSON::XS::true, JSON::XS::false |
|
|
431 | These special values become JSON true and JSON false values, |
|
|
432 | respectively. You cna alos use "\1" and "\0" directly if you want. |
|
|
433 | |
421 | blessed objects |
434 | blessed objects |
422 | Blessed objects are not allowed. JSON::XS currently tries to encode |
435 | Blessed objects are not allowed. JSON::XS currently tries to encode |
423 | their underlying representation (hash- or arrayref), but this |
436 | their underlying representation (hash- or arrayref), but this |
424 | behaviour might change in future versions. |
437 | behaviour might change in future versions. |
425 | |
438 | |
… | |
… | |
535 | Does not generate valid JSON texts (key strings are often unquoted, |
548 | Does not generate valid JSON texts (key strings are often unquoted, |
536 | empty keys result in nothing being output) |
549 | empty keys result in nothing being output) |
537 | |
550 | |
538 | Does not check input for validity. |
551 | Does not check input for validity. |
539 | |
552 | |
|
|
553 | JSON and YAML |
|
|
554 | You often hear that JSON is a subset (or a close subset) of YAML. This |
|
|
555 | is, however, a mass hysteria and very far from the truth. In general, |
|
|
556 | there is no way to configure JSON::XS to output a data structure as |
|
|
557 | valid YAML. |
|
|
558 | |
|
|
559 | If you really must use JSON::XS to generate YAML, you should use this |
|
|
560 | algorithm (subject to change in future versions): |
|
|
561 | |
|
|
562 | my $to_yaml = JSON::XS->new->utf8->space_after (1); |
|
|
563 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
|
|
564 | |
|
|
565 | This will usually generate JSON texts that also parse as valid YAML. |
|
|
566 | Please note that YAML has hardcoded limits on (simple) object key |
|
|
567 | lengths that JSON doesn't have, so you should make sure that your hash |
|
|
568 | keys are noticably shorter than the 1024 characters YAML allows. |
|
|
569 | |
|
|
570 | There might be other incompatibilities that I am not aware of. In |
|
|
571 | general you should not try to generate YAML with a JSON generator or |
|
|
572 | vice versa, or try to parse JSON with a YAML parser or vice versa: |
|
|
573 | chances are high that you will run into severe interoperability |
|
|
574 | problems. |
|
|
575 | |
540 | SPEED |
576 | SPEED |
541 | It seems that JSON::XS is surprisingly fast, as shown in the following |
577 | It seems that JSON::XS is surprisingly fast, as shown in the following |
542 | tables. They have been generated with the help of the "eg/bench" program |
578 | tables. They have been generated with the help of the "eg/bench" program |
543 | in the JSON::XS distribution, to make it easy to compare on your own |
579 | in the JSON::XS distribution, to make it easy to compare on your own |
544 | system. |
580 | system. |
545 | |
581 | |
546 | First comes a comparison between various modules using a very short JSON |
582 | First comes a comparison between various modules using a very short |
547 | string: |
583 | single-line JSON string: |
548 | |
584 | |
549 | {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} |
585 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
|
|
586 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
550 | |
587 | |
551 | It shows the number of encodes/decodes per second (JSON::XS uses the |
588 | It shows the number of encodes/decodes per second (JSON::XS uses the |
552 | functional interface, while JSON::XS/2 uses the OO interface with |
589 | functional interface, while JSON::XS/2 uses the OO interface with |
553 | pretty-printing and hashkey sorting enabled). Higher is better: |
590 | pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink). |
|
|
591 | Higher is better: |
554 | |
592 | |
555 | module | encode | decode | |
593 | module | encode | decode | |
556 | -----------|------------|------------| |
594 | -----------|------------|------------| |
557 | JSON | 11488.516 | 7823.035 | |
595 | JSON | 7645.468 | 4208.613 | |
558 | JSON::DWIW | 94708.054 | 129094.260 | |
596 | JSON::DWIW | 40721.398 | 77101.176 | |
559 | JSON::PC | 63884.157 | 128528.212 | |
597 | JSON::PC | 65948.176 | 78251.940 | |
560 | JSON::Syck | 34898.677 | 42096.911 | |
598 | JSON::Syck | 22844.793 | 26479.192 | |
561 | JSON::XS | 654027.064 | 396423.669 | |
599 | JSON::XS | 388361.481 | 199728.762 | |
562 | JSON::XS/2 | 371564.190 | 371725.613 | |
600 | JSON::XS/2 | 218453.333 | 192399.266 | |
|
|
601 | JSON::XS/3 | 338250.323 | 192399.266 | |
|
|
602 | Storable | 15779.925 | 14169.946 | |
563 | -----------+------------+------------+ |
603 | -----------+------------+------------+ |
564 | |
604 | |
565 | That is, JSON::XS is more than six times faster than JSON::DWIW on |
605 | That is, JSON::XS is about five times faster than JSON::DWIW on |
566 | encoding, more than three times faster on decoding, and about thirty |
606 | encoding, about three times faster on decoding, and over fourty times |
567 | times faster than JSON, even with pretty-printing and key sorting. |
607 | faster than JSON, even with pretty-printing and key sorting. It also |
|
|
608 | compares favourably to Storable for small amounts of data. |
568 | |
609 | |
569 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
610 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
570 | search API (http://nanoref.com/yahooapis/mgPdGg): |
611 | search API (http://nanoref.com/yahooapis/mgPdGg): |
571 | |
612 | |
572 | module | encode | decode | |
613 | module | encode | decode | |
573 | -----------|------------|------------| |
614 | -----------|------------|------------| |
574 | JSON | 273.023 | 44.674 | |
615 | JSON | 254.685 | 37.665 | |
575 | JSON::DWIW | 1089.383 | 1145.704 | |
616 | JSON::DWIW | 843.343 | 1049.731 | |
576 | JSON::PC | 3097.419 | 2393.921 | |
617 | JSON::PC | 3602.116 | 2307.352 | |
577 | JSON::Syck | 514.060 | 843.053 | |
618 | JSON::Syck | 505.107 | 787.899 | |
578 | JSON::XS | 6479.668 | 3636.364 | |
619 | JSON::XS | 5747.196 | 3690.220 | |
579 | JSON::XS/2 | 3774.221 | 3599.124 | |
620 | JSON::XS/2 | 3968.121 | 3676.634 | |
|
|
621 | JSON::XS/3 | 6105.246 | 3662.508 | |
|
|
622 | Storable | 4417.337 | 5285.161 | |
580 | -----------+------------+------------+ |
623 | -----------+------------+------------+ |
581 | |
624 | |
582 | Again, JSON::XS leads by far. |
625 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
|
|
626 | decodes faster). |
583 | |
627 | |
584 | On large strings containing lots of high unicode characters, some |
628 | On large strings containing lots of high unicode characters, some |
585 | modules (such as JSON::PC) seem to decode faster than JSON::XS, but the |
629 | modules (such as JSON::PC) seem to decode faster than JSON::XS, but the |
586 | result will be broken due to missing (or wrong) unicode handling. Others |
630 | result will be broken due to missing (or wrong) unicode handling. Others |
587 | refuse to decode or encode properly, so it was impossible to prepare a |
631 | refuse to decode or encode properly, so it was impossible to prepare a |
… | |
… | |
613 | |
657 | |
614 | And last but least, something else could bomb you that I forgot to think |
658 | And last but least, something else could bomb you that I forgot to think |
615 | of. In that case, you get to keep the pieces. I am always open for |
659 | of. In that case, you get to keep the pieces. I am always open for |
616 | hints, though... |
660 | hints, though... |
617 | |
661 | |
|
|
662 | If you are using JSON::XS to return packets to consumption by javascript |
|
|
663 | scripts in a browser you should have a look at |
|
|
664 | <http://jpsykes.com/47/practical-csrf-and-json-security> to see wether |
|
|
665 | you are vulnerable to some common attack vectors (which really are |
|
|
666 | browser design bugs, but it is still you who will have to deal with it, |
|
|
667 | as major browser developers care only for features, not about doing |
|
|
668 | security right). |
|
|
669 | |
618 | BUGS |
670 | BUGS |
619 | While the goal of this module is to be correct, that unfortunately does |
671 | While the goal of this module is to be correct, that unfortunately does |
620 | not mean its bug-free, only that I think its design is bug-free. It is |
672 | not mean its bug-free, only that I think its design is bug-free. It is |
621 | still relatively early in its development. If you keep reporting bugs |
673 | still relatively early in its development. If you keep reporting bugs |
622 | they will be fixed swiftly, though. |
674 | they will be fixed swiftly, though. |