… | |
… | |
128 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
128 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
129 | |
129 | |
130 | except being faster. |
130 | except being faster. |
131 | |
131 | |
132 | =back |
132 | =back |
|
|
133 | |
133 | |
134 | |
134 | =head1 OBJECT-ORIENTED INTERFACE |
135 | =head1 OBJECT-ORIENTED INTERFACE |
135 | |
136 | |
136 | The object oriented interface lets you configure your own encoding or |
137 | The object oriented interface lets you configure your own encoding or |
137 | decoding style, within the limits of supported formats. |
138 | decoding style, within the limits of supported formats. |
… | |
… | |
301 | |
302 | |
302 | In the future, this setting might control other things, such as converting |
303 | In the future, this setting might control other things, such as converting |
303 | strings that look like integers or floats into integers or floats |
304 | strings that look like integers or floats into integers or floats |
304 | internally (there is no difference on the Perl level), saving space. |
305 | internally (there is no difference on the Perl level), saving space. |
305 | |
306 | |
|
|
307 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
|
|
308 | |
|
|
309 | Sets the maximum nesting level (default C<8192>) accepted while encoding |
|
|
310 | or decoding. If the JSON text or Perl data structure has an equal or |
|
|
311 | higher nesting level then this limit, then the encoder and decoder will |
|
|
312 | stop and croak at that point. |
|
|
313 | |
|
|
314 | Nesting level is defined by number of hash- or arrayrefs that the encoder |
|
|
315 | needs to traverse to reach a given point or the number of C<{> or C<[> |
|
|
316 | characters without their matching closing parenthesis crossed to reach a |
|
|
317 | given character in a string. |
|
|
318 | |
|
|
319 | Setting the maximum depth to one disallows any nesting, so that ensures |
|
|
320 | that the object is only a single hash/object or array. |
|
|
321 | |
|
|
322 | The argument to C<max_depth> will be rounded up to the next nearest power |
|
|
323 | of two. |
|
|
324 | |
|
|
325 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
|
|
326 | |
306 | =item $json_text = $json->encode ($perl_scalar) |
327 | =item $json_text = $json->encode ($perl_scalar) |
307 | |
328 | |
308 | Converts the given Perl data structure (a simple scalar or a reference |
329 | Converts the given Perl data structure (a simple scalar or a reference |
309 | to a hash or array) to its JSON representation. Simple scalars will be |
330 | to a hash or array) to its JSON representation. Simple scalars will be |
310 | converted into JSON string or number sequences, while references to arrays |
331 | converted into JSON string or number sequences, while references to arrays |
… | |
… | |
320 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
341 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
321 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
342 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
322 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
343 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
323 | |
344 | |
324 | =back |
345 | =back |
|
|
346 | |
325 | |
347 | |
326 | =head1 MAPPING |
348 | =head1 MAPPING |
327 | |
349 | |
328 | This section describes how JSON::XS maps Perl values to JSON values and |
350 | This section describes how JSON::XS maps Perl values to JSON values and |
329 | vice versa. These mappings are designed to "do the right thing" in most |
351 | vice versa. These mappings are designed to "do the right thing" in most |
… | |
… | |
440 | =item circular data structures |
462 | =item circular data structures |
441 | |
463 | |
442 | Those will be encoded until memory or stackspace runs out. |
464 | Those will be encoded until memory or stackspace runs out. |
443 | |
465 | |
444 | =back |
466 | =back |
|
|
467 | |
445 | |
468 | |
446 | =head1 COMPARISON |
469 | =head1 COMPARISON |
447 | |
470 | |
448 | As already mentioned, this module was created because none of the existing |
471 | As already mentioned, this module was created because none of the existing |
449 | JSON modules could be made to work correctly. First I will describe the |
472 | JSON modules could be made to work correctly. First I will describe the |
… | |
… | |
578 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
601 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
579 | will be broken due to missing (or wrong) unicode handling. Others refuse |
602 | will be broken due to missing (or wrong) unicode handling. Others refuse |
580 | to decode or encode properly, so it was impossible to prepare a fair |
603 | to decode or encode properly, so it was impossible to prepare a fair |
581 | comparison table for that case. |
604 | comparison table for that case. |
582 | |
605 | |
583 | =head1 RESOURCE LIMITS |
|
|
584 | |
606 | |
585 | JSON::XS does not impose any limits on the size of JSON texts or Perl |
607 | =head1 SECURITY CONSIDERATIONS |
586 | values they represent - if your machine can handle it, JSON::XS will |
608 | |
587 | encode or decode it. Future versions might optionally impose structure |
609 | When you are using JSON in a protocol, talking to untrusted potentially |
588 | depth and memory use resource limits. |
610 | hostile creatures requires relatively few measures. |
|
|
611 | |
|
|
612 | First of all, your JSON decoder should be secure, that is, should not have |
|
|
613 | any buffer overflows. Obviously, this module should ensure that and I am |
|
|
614 | trying hard on making that true, but you never know. |
|
|
615 | |
|
|
616 | Second, you need to avoid resource-starving attacks. That means you should |
|
|
617 | limit the size of JSON texts you accept, or make sure then when your |
|
|
618 | resources run out, thats just fine (e.g. by using a separate process that |
|
|
619 | can crash safely). The size of a JSON text in octets or characters is |
|
|
620 | usually a good indication of the size of the resources required to decode |
|
|
621 | it into a Perl structure. |
|
|
622 | |
|
|
623 | Third, JSON::XS recurses using the C stack when decoding objects and |
|
|
624 | arrays. The C stack is a limited resource: for instance, on my amd64 |
|
|
625 | machine with 8MB of stack size I can decode around 180k nested arrays |
|
|
626 | but only 14k nested JSON objects. If that is exceeded, the program |
|
|
627 | crashes. Thats why the default nesting limit is set to 8192. If your |
|
|
628 | process has a smaller stack, you should adjust this setting accordingly |
|
|
629 | with the C<max_depth> method. |
|
|
630 | |
|
|
631 | And last but least, something else could bomb you that I forgot to think |
|
|
632 | of. In that case, you get to keep the pieces. I am alway sopen for hints, |
|
|
633 | though... |
|
|
634 | |
589 | |
635 | |
590 | =head1 BUGS |
636 | =head1 BUGS |
591 | |
637 | |
592 | While the goal of this module is to be correct, that unfortunately does |
638 | While the goal of this module is to be correct, that unfortunately does |
593 | not mean its bug-free, only that I think its design is bug-free. It is |
639 | not mean its bug-free, only that I think its design is bug-free. It is |
594 | still very young and not well-tested. If you keep reporting bugs they will |
640 | still relatively early in its development. If you keep reporting bugs they |
595 | be fixed swiftly, though. |
641 | will be fixed swiftly, though. |
596 | |
642 | |
597 | =cut |
643 | =cut |
598 | |
644 | |
599 | 1; |
645 | 1; |
600 | |
646 | |