… | |
… | |
7 | # exported functions, they croak on error |
7 | # exported functions, they croak on error |
8 | # and expect/generate UTF-8 |
8 | # and expect/generate UTF-8 |
9 | |
9 | |
10 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
10 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
11 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
11 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
12 | |
|
|
13 | # objToJson and jsonToObj aliases to to_json and from_json |
|
|
14 | # are exported for compatibility to the JSON module, |
|
|
15 | # but should not be used in new code. |
|
|
16 | |
12 | |
17 | # OO-interface |
13 | # OO-interface |
18 | |
14 | |
19 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
15 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
20 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
16 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
… | |
… | |
277 | Example, encode a Perl scalar as JSON value with enabled |
273 | Example, encode a Perl scalar as JSON value with enabled |
278 | "allow_nonref", resulting in an invalid JSON text: |
274 | "allow_nonref", resulting in an invalid JSON text: |
279 | |
275 | |
280 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
276 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
281 | => "Hello, World!" |
277 | => "Hello, World!" |
|
|
278 | |
|
|
279 | $json = $json->allow_blessed ([$enable]) |
|
|
280 | If $enable is true (or missing), then the "encode" method will not |
|
|
281 | barf when it encounters a blessed reference. Instead, the value of |
|
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282 | the convert_blessed option will decide wether "null" |
|
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283 | ("convert_blessed" disabled or no "to_json" method found) or a |
|
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284 | representation of the object ("convert_blessed" enabled and |
|
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285 | "to_json" method found) is being encoded. Has no effect on "decode". |
|
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286 | |
|
|
287 | If $enable is false (the default), then "encode" will throw an |
|
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288 | exception when it encounters a blessed object. |
|
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289 | |
|
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290 | $json = $json->convert_blessed ([$enable]) |
|
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291 | If $enable is true (or missing), then "encode", upon encountering a |
|
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292 | blessed object, will check for the availability of the "TO_JSON" |
|
|
293 | method on the object's class. If found, it will be called in scalar |
|
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294 | context and the resulting scalar will be encoded instead of the |
|
|
295 | object. If no "TO_JSON" method is found, the value of |
|
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296 | "allow_blessed" will decide what to do. |
|
|
297 | |
|
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298 | The "TO_JSON" method may safely call die if it wants. If "TO_JSON" |
|
|
299 | returns other blessed objects, those will be handled in the same |
|
|
300 | way. "TO_JSON" must take care of not causing an endless recursion |
|
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301 | cycle (== crash) in this case. The name of "TO_JSON" was chosen |
|
|
302 | because other methods called by the Perl core (== not by the user of |
|
|
303 | the object) are usually in upper case letters and to avoid |
|
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304 | collisions with the "to_json" function. |
|
|
305 | |
|
|
306 | This setting does not yet influence "decode" in any way, but in the |
|
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307 | future, global hooks might get installed that influence "decode" and |
|
|
308 | are enabled by this setting. |
|
|
309 | |
|
|
310 | If $enable is false, then the "allow_blessed" setting will decide |
|
|
311 | what to do when a blessed object is found. |
|
|
312 | |
|
|
313 | $json = $json->filter_json_object ([$coderef->($hashref)]) |
|
|
314 | When $coderef is specified, it will be called from "decode" each |
|
|
315 | time it decodes a JSON object. The only argument is a reference to |
|
|
316 | the newly-created hash. If the code references returns a single |
|
|
317 | scalar (which need not be a reference), this value (i.e. a copy of |
|
|
318 | that scalar to avoid aliasing) is inserted into the deserialised |
|
|
319 | data structure. If it returns an empty list (NOTE: *not* "undef", |
|
|
320 | which is a valid scalar), the original deserialised hash will be |
|
|
321 | inserted. This setting can slow down decoding considerably. |
|
|
322 | |
|
|
323 | When $coderef is omitted or undefined, any existing callback will be |
|
|
324 | removed and "decode" will not change the deserialised hash in any |
|
|
325 | way. |
|
|
326 | |
|
|
327 | Example, convert all JSON objects into the integer 5: |
|
|
328 | |
|
|
329 | my $js = JSON::XS->new->filter_json_object (sub { 5 }); |
|
|
330 | # returns [5] |
|
|
331 | $js->decode ('[{}]') |
|
|
332 | # throw an exception because allow_nonref is not enabled |
|
|
333 | # so a lone 5 is not allowed. |
|
|
334 | $js->decode ('{"a":1, "b":2}'); |
|
|
335 | |
|
|
336 | $json = $json->filter_json_single_key_object ($key [=> |
|
|
337 | $coderef->($value)]) |
|
|
338 | Works remotely similar to "filter_json_object", but is only called |
|
|
339 | for JSON objects having a single key named $key. |
|
|
340 | |
|
|
341 | This $coderef is called before the one specified via |
|
|
342 | "filter_json_object", if any. It gets passed the single value in the |
|
|
343 | JSON object. If it returns a single value, it will be inserted into |
|
|
344 | the data structure. If it returns nothing (not even "undef" but the |
|
|
345 | empty list), the callback from "filter_json_object" will be called |
|
|
346 | next, as if no single-key callback were specified. |
|
|
347 | |
|
|
348 | If $coderef is omitted or undefined, the corresponding callback will |
|
|
349 | be disabled. There can only ever be one callback for a given key. |
|
|
350 | |
|
|
351 | As this callback gets called less often then the |
|
|
352 | "filter_json_object" one, decoding speed will not usually suffer as |
|
|
353 | much. Therefore, single-key objects make excellent targets to |
|
|
354 | serialise Perl objects into, especially as single-key JSON objects |
|
|
355 | are as close to the type-tagged value concept as JSON gets (its |
|
|
356 | basically an ID/VALUE tuple). Of course, JSON does not support this |
|
|
357 | in any way, so you need to make sure your data never looks like a |
|
|
358 | serialised Perl hash. |
|
|
359 | |
|
|
360 | Typical names for the single object key are "__class_whatever__", or |
|
|
361 | "$__dollars_are_rarely_used__$" or "}ugly_brace_placement", or even |
|
|
362 | things like "__class_md5sum(classname)__", to reduce the risk of |
|
|
363 | clashing with real hashes. |
|
|
364 | |
|
|
365 | Example, decode JSON objects of the form "{ "__widget__" => <id> }" |
|
|
366 | into the corresponding $WIDGET{<id>} object: |
|
|
367 | |
|
|
368 | # return whatever is in $WIDGET{5}: |
|
|
369 | JSON::XS |
|
|
370 | ->new |
|
|
371 | ->filter_json_single_key_object (__widget__ => sub { |
|
|
372 | $WIDGET{ $_[0] } |
|
|
373 | }) |
|
|
374 | ->decode ('{"__widget__": 5') |
|
|
375 | |
|
|
376 | # this can be used with a TO_JSON method in some "widget" class |
|
|
377 | # for serialisation to json: |
|
|
378 | sub WidgetBase::TO_JSON { |
|
|
379 | my ($self) = @_; |
|
|
380 | |
|
|
381 | unless ($self->{id}) { |
|
|
382 | $self->{id} = ..get..some..id..; |
|
|
383 | $WIDGET{$self->{id}} = $self; |
|
|
384 | } |
|
|
385 | |
|
|
386 | { __widget__ => $self->{id} } |
|
|
387 | } |
282 | |
388 | |
283 | $json = $json->shrink ([$enable]) |
389 | $json = $json->shrink ([$enable]) |
284 | Perl usually over-allocates memory a bit when allocating space for |
390 | Perl usually over-allocates memory a bit when allocating space for |
285 | strings. This flag optionally resizes strings generated by either |
391 | strings. This flag optionally resizes strings generated by either |
286 | "encode" or "decode" to their minimum size possible. This can save |
392 | "encode" or "decode" to their minimum size possible. This can save |
… | |
… | |
319 | crossed to reach a given character in a string. |
425 | crossed to reach a given character in a string. |
320 | |
426 | |
321 | Setting the maximum depth to one disallows any nesting, so that |
427 | Setting the maximum depth to one disallows any nesting, so that |
322 | ensures that the object is only a single hash/object or array. |
428 | ensures that the object is only a single hash/object or array. |
323 | |
429 | |
324 | The argument to "max_depth" will be rounded up to the next nearest |
430 | The argument to "max_depth" will be rounded up to the next highest |
325 | power of two. |
431 | power of two. If no argument is given, the highest possible setting |
|
|
432 | will be used, which is rarely useful. |
|
|
433 | |
|
|
434 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
|
|
435 | useful. |
|
|
436 | |
|
|
437 | $json = $json->max_size ([$maximum_string_size]) |
|
|
438 | Set the maximum length a JSON text may have (in bytes) where |
|
|
439 | decoding is being attempted. The default is 0, meaning no limit. |
|
|
440 | When "decode" is called on a string longer then this number of |
|
|
441 | characters it will not attempt to decode the string but throw an |
|
|
442 | exception. This setting has no effect on "encode" (yet). |
|
|
443 | |
|
|
444 | The argument to "max_size" will be rounded up to the next highest |
|
|
445 | power of two (so may be more than requested). If no argument is |
|
|
446 | given, the limit check will be deactivated (same as when 0 is |
|
|
447 | specified). |
326 | |
448 | |
327 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
449 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
328 | useful. |
450 | useful. |
329 | |
451 | |
330 | $json_text = $json->encode ($perl_scalar) |
452 | $json_text = $json->encode ($perl_scalar) |
… | |
… | |
380 | A JSON string becomes a string scalar in Perl - Unicode codepoints |
502 | A JSON string becomes a string scalar in Perl - Unicode codepoints |
381 | in JSON are represented by the same codepoints in the Perl string, |
503 | in JSON are represented by the same codepoints in the Perl string, |
382 | so no manual decoding is necessary. |
504 | so no manual decoding is necessary. |
383 | |
505 | |
384 | number |
506 | number |
385 | A JSON number becomes either an integer or numeric (floating point) |
507 | A JSON number becomes either an integer, numeric (floating point) or |
386 | scalar in perl, depending on its range and any fractional parts. On |
508 | string scalar in perl, depending on its range and any fractional |
387 | the Perl level, there is no difference between those as Perl handles |
509 | parts. On the Perl level, there is no difference between those as |
388 | all the conversion details, but an integer may take slightly less |
510 | Perl handles all the conversion details, but an integer may take |
389 | memory and might represent more values exactly than (floating point) |
511 | slightly less memory and might represent more values exactly than |
390 | numbers. |
512 | (floating point) numbers. |
|
|
513 | |
|
|
514 | If the number consists of digits only, JSON::XS will try to |
|
|
515 | represent it as an integer value. If that fails, it will try to |
|
|
516 | represent it as a numeric (floating point) value if that is possible |
|
|
517 | without loss of precision. Otherwise it will preserve the number as |
|
|
518 | a string value. |
|
|
519 | |
|
|
520 | Numbers containing a fractional or exponential part will always be |
|
|
521 | represented as numeric (floating point) values, possibly at a loss |
|
|
522 | of precision. |
|
|
523 | |
|
|
524 | This might create round-tripping problems as numbers might become |
|
|
525 | strings, but as Perl is typeless there is no other way to do it. |
391 | |
526 | |
392 | true, false |
527 | true, false |
393 | These JSON atoms become "JSON::XS::true" and "JSON::XS::false", |
528 | These JSON atoms become "JSON::XS::true" and "JSON::XS::false", |
394 | respectively. They are overloaded to act almost exactly like the |
529 | respectively. They are overloaded to act almost exactly like the |
395 | numbers 1 and 0. You can check wether a scalar is a JSON boolean by |
530 | numbers 1 and 0. You can check wether a scalar is a JSON boolean by |
… | |
… | |
588 | It shows the number of encodes/decodes per second (JSON::XS uses the |
723 | It shows the number of encodes/decodes per second (JSON::XS uses the |
589 | functional interface, while JSON::XS/2 uses the OO interface with |
724 | functional interface, while JSON::XS/2 uses the OO interface with |
590 | pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink). |
725 | pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink). |
591 | Higher is better: |
726 | Higher is better: |
592 | |
727 | |
|
|
728 | Storable | 15779.925 | 14169.946 | |
|
|
729 | -----------+------------+------------+ |
593 | module | encode | decode | |
730 | module | encode | decode | |
594 | -----------|------------|------------| |
731 | -----------|------------|------------| |
595 | JSON | 7645.468 | 4208.613 | |
732 | JSON | 4990.842 | 4088.813 | |
596 | JSON::DWIW | 40721.398 | 77101.176 | |
733 | JSON::DWIW | 51653.990 | 71575.154 | |
597 | JSON::PC | 65948.176 | 78251.940 | |
734 | JSON::PC | 65948.176 | 74631.744 | |
598 | JSON::Syck | 22844.793 | 26479.192 | |
735 | JSON::PP | 8931.652 | 3817.168 | |
|
|
736 | JSON::Syck | 24877.248 | 27776.848 | |
599 | JSON::XS | 388361.481 | 199728.762 | |
737 | JSON::XS | 388361.481 | 227951.304 | |
600 | JSON::XS/2 | 218453.333 | 192399.266 | |
738 | JSON::XS/2 | 227951.304 | 218453.333 | |
601 | JSON::XS/3 | 338250.323 | 192399.266 | |
739 | JSON::XS/3 | 338250.323 | 218453.333 | |
602 | Storable | 15779.925 | 14169.946 | |
740 | Storable | 16500.016 | 135300.129 | |
603 | -----------+------------+------------+ |
741 | -----------+------------+------------+ |
604 | |
742 | |
605 | That is, JSON::XS is about five times faster than JSON::DWIW on |
743 | That is, JSON::XS is about five times faster than JSON::DWIW on |
606 | encoding, about three times faster on decoding, and over fourty times |
744 | encoding, about three times faster on decoding, and over fourty times |
607 | faster than JSON, even with pretty-printing and key sorting. It also |
745 | faster than JSON, even with pretty-printing and key sorting. It also |
… | |
… | |
610 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
748 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
611 | search API (http://nanoref.com/yahooapis/mgPdGg): |
749 | search API (http://nanoref.com/yahooapis/mgPdGg): |
612 | |
750 | |
613 | module | encode | decode | |
751 | module | encode | decode | |
614 | -----------|------------|------------| |
752 | -----------|------------|------------| |
615 | JSON | 254.685 | 37.665 | |
753 | JSON | 55.260 | 34.971 | |
616 | JSON::DWIW | 843.343 | 1049.731 | |
754 | JSON::DWIW | 825.228 | 1082.513 | |
617 | JSON::PC | 3602.116 | 2307.352 | |
755 | JSON::PC | 3571.444 | 2394.829 | |
|
|
756 | JSON::PP | 210.987 | 32.574 | |
618 | JSON::Syck | 505.107 | 787.899 | |
757 | JSON::Syck | 552.551 | 787.544 | |
619 | JSON::XS | 5747.196 | 3690.220 | |
758 | JSON::XS | 5780.463 | 4854.519 | |
620 | JSON::XS/2 | 3968.121 | 3676.634 | |
759 | JSON::XS/2 | 3869.998 | 4798.975 | |
621 | JSON::XS/3 | 6105.246 | 3662.508 | |
760 | JSON::XS/3 | 5862.880 | 4798.975 | |
622 | Storable | 4417.337 | 5285.161 | |
761 | Storable | 4445.002 | 5235.027 | |
623 | -----------+------------+------------+ |
762 | -----------+------------+------------+ |
624 | |
763 | |
625 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
764 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
626 | decodes faster). |
765 | decodes faster). |
627 | |
766 | |
… | |
… | |
642 | Second, you need to avoid resource-starving attacks. That means you |
781 | Second, you need to avoid resource-starving attacks. That means you |
643 | should limit the size of JSON texts you accept, or make sure then when |
782 | should limit the size of JSON texts you accept, or make sure then when |
644 | your resources run out, thats just fine (e.g. by using a separate |
783 | your resources run out, thats just fine (e.g. by using a separate |
645 | process that can crash safely). The size of a JSON text in octets or |
784 | process that can crash safely). The size of a JSON text in octets or |
646 | characters is usually a good indication of the size of the resources |
785 | characters is usually a good indication of the size of the resources |
647 | required to decode it into a Perl structure. |
786 | required to decode it into a Perl structure. While JSON::XS can check |
|
|
787 | the size of the JSON text, it might be too late when you already have it |
|
|
788 | in memory, so you might want to check the size before you accept the |
|
|
789 | string. |
648 | |
790 | |
649 | Third, JSON::XS recurses using the C stack when decoding objects and |
791 | Third, JSON::XS recurses using the C stack when decoding objects and |
650 | arrays. The C stack is a limited resource: for instance, on my amd64 |
792 | arrays. The C stack is a limited resource: for instance, on my amd64 |
651 | machine with 8MB of stack size I can decode around 180k nested arrays |
793 | machine with 8MB of stack size I can decode around 180k nested arrays |
652 | but only 14k nested JSON objects (due to perl itself recursing deeply on |
794 | but only 14k nested JSON objects (due to perl itself recursing deeply on |