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4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use JSON::XS; |
7 | use JSON::XS; |
8 | |
8 | |
9 | # exported functions, croak on error |
9 | # exported functions, they croak on error |
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10 | # and expect/generate UTF-8 |
10 | |
11 | |
11 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
12 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
12 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
13 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
13 | |
14 | |
14 | # objToJson and jsonToObj are exported for JSON |
15 | # objToJson and jsonToObj aliases to to_json and from_json |
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16 | # are exported for compatibility to the JSON module, |
15 | # compatibility, but should not be used in new code. |
17 | # but should not be used in new code. |
16 | |
18 | |
17 | # oo-interface |
19 | # OO-interface |
18 | |
20 | |
19 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
21 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
20 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
22 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
21 | $perl_scalar = $coder->decode ($unicode_json_text); |
23 | $perl_scalar = $coder->decode ($unicode_json_text); |
22 | |
24 | |
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84 | package JSON::XS; |
86 | package JSON::XS; |
85 | |
87 | |
86 | use strict; |
88 | use strict; |
87 | |
89 | |
88 | BEGIN { |
90 | BEGIN { |
89 | our $VERSION = '0.8'; |
91 | our $VERSION = '1.1'; |
90 | our @ISA = qw(Exporter); |
92 | our @ISA = qw(Exporter); |
91 | |
93 | |
92 | our @EXPORT = qw(to_json from_json objToJson jsonToObj); |
94 | our @EXPORT = qw(to_json from_json objToJson jsonToObj); |
93 | require Exporter; |
95 | require Exporter; |
94 | |
96 | |
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126 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
128 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
127 | |
129 | |
128 | except being faster. |
130 | except being faster. |
129 | |
131 | |
130 | =back |
132 | =back |
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133 | |
131 | |
134 | |
132 | =head1 OBJECT-ORIENTED INTERFACE |
135 | =head1 OBJECT-ORIENTED INTERFACE |
133 | |
136 | |
134 | The object oriented interface lets you configure your own encoding or |
137 | The object oriented interface lets you configure your own encoding or |
135 | decoding style, within the limits of supported formats. |
138 | decoding style, within the limits of supported formats. |
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281 | => "Hello, World!" |
284 | => "Hello, World!" |
282 | |
285 | |
283 | =item $json = $json->shrink ([$enable]) |
286 | =item $json = $json->shrink ([$enable]) |
284 | |
287 | |
285 | Perl usually over-allocates memory a bit when allocating space for |
288 | Perl usually over-allocates memory a bit when allocating space for |
286 | strings. This flag optionally resizes strings generated by either |
289 | strings. This flag optionally resizes strings generated by either |
287 | C<encode> or C<decode> to their minimum size possible. This can save |
290 | C<encode> or C<decode> to their minimum size possible. This can save |
288 | memory when your JSON texts are either very very long or you have many |
291 | memory when your JSON texts are either very very long or you have many |
289 | short strings. It will also try to downgrade any strings to octet-form |
292 | short strings. It will also try to downgrade any strings to octet-form |
290 | if possible: perl stores strings internally either in an encoding called |
293 | if possible: perl stores strings internally either in an encoding called |
291 | UTF-X or in octet-form. The latter cannot store everything but uses less |
294 | UTF-X or in octet-form. The latter cannot store everything but uses less |
292 | space in general. |
295 | space in general (and some buggy Perl or C code might even rely on that |
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296 | internal representation being used). |
293 | |
297 | |
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298 | The actual definition of what shrink does might change in future versions, |
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299 | but it will always try to save space at the expense of time. |
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300 | |
294 | If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit, |
301 | If C<$enable> is true (or missing), the string returned by C<encode> will |
295 | while all strings generated by C<decode> will also be shrunk-to-fit. |
302 | be shrunk-to-fit, while all strings generated by C<decode> will also be |
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303 | shrunk-to-fit. |
296 | |
304 | |
297 | If C<$enable> is false, then the normal perl allocation algorithms are used. |
305 | If C<$enable> is false, then the normal perl allocation algorithms are used. |
298 | If you work with your data, then this is likely to be faster. |
306 | If you work with your data, then this is likely to be faster. |
299 | |
307 | |
300 | In the future, this setting might control other things, such as converting |
308 | In the future, this setting might control other things, such as converting |
301 | strings that look like integers or floats into integers or floats |
309 | strings that look like integers or floats into integers or floats |
302 | internally (there is no difference on the Perl level), saving space. |
310 | internally (there is no difference on the Perl level), saving space. |
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311 | |
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312 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
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313 | |
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314 | Sets the maximum nesting level (default C<512>) accepted while encoding |
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315 | or decoding. If the JSON text or Perl data structure has an equal or |
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316 | higher nesting level then this limit, then the encoder and decoder will |
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317 | stop and croak at that point. |
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318 | |
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319 | Nesting level is defined by number of hash- or arrayrefs that the encoder |
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320 | needs to traverse to reach a given point or the number of C<{> or C<[> |
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321 | characters without their matching closing parenthesis crossed to reach a |
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322 | given character in a string. |
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323 | |
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324 | Setting the maximum depth to one disallows any nesting, so that ensures |
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325 | that the object is only a single hash/object or array. |
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326 | |
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327 | The argument to C<max_depth> will be rounded up to the next nearest power |
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328 | of two. |
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329 | |
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330 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
303 | |
331 | |
304 | =item $json_text = $json->encode ($perl_scalar) |
332 | =item $json_text = $json->encode ($perl_scalar) |
305 | |
333 | |
306 | Converts the given Perl data structure (a simple scalar or a reference |
334 | Converts the given Perl data structure (a simple scalar or a reference |
307 | to a hash or array) to its JSON representation. Simple scalars will be |
335 | to a hash or array) to its JSON representation. Simple scalars will be |
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319 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
347 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
320 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
348 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
321 | |
349 | |
322 | =back |
350 | =back |
323 | |
351 | |
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352 | |
324 | =head1 MAPPING |
353 | =head1 MAPPING |
325 | |
354 | |
326 | This section describes how JSON::XS maps Perl values to JSON values and |
355 | This section describes how JSON::XS maps Perl values to JSON values and |
327 | vice versa. These mappings are designed to "do the right thing" in most |
356 | vice versa. These mappings are designed to "do the right thing" in most |
328 | circumstances automatically, preserving round-tripping characteristics |
357 | circumstances automatically, preserving round-tripping characteristics |
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381 | =over 4 |
410 | =over 4 |
382 | |
411 | |
383 | =item hash references |
412 | =item hash references |
384 | |
413 | |
385 | Perl hash references become JSON objects. As there is no inherent ordering |
414 | Perl hash references become JSON objects. As there is no inherent ordering |
386 | in hash keys, they will usually be encoded in a pseudo-random order that |
415 | in hash keys (or JSON objects), they will usually be encoded in a |
387 | can change between runs of the same program but stays generally the same |
416 | pseudo-random order that can change between runs of the same program but |
388 | within a single run of a program. JSON::XS can optionally sort the hash |
417 | stays generally the same within a single run of a program. JSON::XS can |
389 | keys (determined by the I<canonical> flag), so the same datastructure |
418 | optionally sort the hash keys (determined by the I<canonical> flag), so |
390 | will serialise to the same JSON text (given same settings and version of |
419 | the same datastructure will serialise to the same JSON text (given same |
391 | JSON::XS), but this incurs a runtime overhead. |
420 | settings and version of JSON::XS), but this incurs a runtime overhead |
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421 | and is only rarely useful, e.g. when you want to compare some JSON text |
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422 | against another for equality. |
392 | |
423 | |
393 | =item array references |
424 | =item array references |
394 | |
425 | |
395 | Perl array references become JSON arrays. |
426 | Perl array references become JSON arrays. |
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427 | |
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428 | =item other references |
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429 | |
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430 | Other unblessed references are generally not allowed and will cause an |
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431 | exception to be thrown, except for references to the integers C<0> and |
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432 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
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433 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
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434 | |
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435 | to_json [\0,JSON::XS::true] # yields [false,true] |
396 | |
436 | |
397 | =item blessed objects |
437 | =item blessed objects |
398 | |
438 | |
399 | Blessed objects are not allowed. JSON::XS currently tries to encode their |
439 | Blessed objects are not allowed. JSON::XS currently tries to encode their |
400 | underlying representation (hash- or arrayref), but this behaviour might |
440 | underlying representation (hash- or arrayref), but this behaviour might |
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433 | $x *= 1; # same thing, the choise is yours. |
473 | $x *= 1; # same thing, the choise is yours. |
434 | |
474 | |
435 | You can not currently output JSON booleans or force the type in other, |
475 | You can not currently output JSON booleans or force the type in other, |
436 | less obscure, ways. Tell me if you need this capability. |
476 | less obscure, ways. Tell me if you need this capability. |
437 | |
477 | |
438 | =item circular data structures |
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439 | |
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440 | Those will be encoded until memory or stackspace runs out. |
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441 | |
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442 | =back |
478 | =back |
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479 | |
443 | |
480 | |
444 | =head1 COMPARISON |
481 | =head1 COMPARISON |
445 | |
482 | |
446 | As already mentioned, this module was created because none of the existing |
483 | As already mentioned, this module was created because none of the existing |
447 | JSON modules could be made to work correctly. First I will describe the |
484 | JSON modules could be made to work correctly. First I will describe the |
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576 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
613 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
577 | will be broken due to missing (or wrong) unicode handling. Others refuse |
614 | will be broken due to missing (or wrong) unicode handling. Others refuse |
578 | to decode or encode properly, so it was impossible to prepare a fair |
615 | to decode or encode properly, so it was impossible to prepare a fair |
579 | comparison table for that case. |
616 | comparison table for that case. |
580 | |
617 | |
581 | =head1 RESOURCE LIMITS |
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582 | |
618 | |
583 | JSON::XS does not impose any limits on the size of JSON texts or Perl |
619 | =head1 SECURITY CONSIDERATIONS |
584 | values they represent - if your machine can handle it, JSON::XS will |
620 | |
585 | encode or decode it. Future versions might optionally impose structure |
621 | When you are using JSON in a protocol, talking to untrusted potentially |
586 | depth and memory use resource limits. |
622 | hostile creatures requires relatively few measures. |
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623 | |
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624 | First of all, your JSON decoder should be secure, that is, should not have |
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625 | any buffer overflows. Obviously, this module should ensure that and I am |
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626 | trying hard on making that true, but you never know. |
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627 | |
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628 | Second, you need to avoid resource-starving attacks. That means you should |
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629 | limit the size of JSON texts you accept, or make sure then when your |
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630 | resources run out, thats just fine (e.g. by using a separate process that |
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631 | can crash safely). The size of a JSON text in octets or characters is |
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632 | usually a good indication of the size of the resources required to decode |
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633 | it into a Perl structure. |
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634 | |
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635 | Third, JSON::XS recurses using the C stack when decoding objects and |
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636 | arrays. The C stack is a limited resource: for instance, on my amd64 |
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637 | machine with 8MB of stack size I can decode around 180k nested arrays but |
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638 | only 14k nested JSON objects (due to perl itself recursing deeply on croak |
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639 | to free the temporary). If that is exceeded, the program crashes. to be |
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640 | conservative, the default nesting limit is set to 512. If your process |
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641 | has a smaller stack, you should adjust this setting accordingly with the |
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642 | C<max_depth> method. |
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643 | |
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644 | And last but least, something else could bomb you that I forgot to think |
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645 | of. In that case, you get to keep the pieces. I am alway sopen for hints, |
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646 | though... |
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647 | |
587 | |
648 | |
588 | =head1 BUGS |
649 | =head1 BUGS |
589 | |
650 | |
590 | While the goal of this module is to be correct, that unfortunately does |
651 | While the goal of this module is to be correct, that unfortunately does |
591 | not mean its bug-free, only that I think its design is bug-free. It is |
652 | not mean its bug-free, only that I think its design is bug-free. It is |
592 | still very young and not well-tested. If you keep reporting bugs they will |
653 | still relatively early in its development. If you keep reporting bugs they |
593 | be fixed swiftly, though. |
654 | will be fixed swiftly, though. |
594 | |
655 | |
595 | =cut |
656 | =cut |
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657 | |
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658 | sub true() { \1 } |
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659 | sub false() { \0 } |
596 | |
660 | |
597 | 1; |
661 | 1; |
598 | |
662 | |
599 | =head1 AUTHOR |
663 | =head1 AUTHOR |
600 | |
664 | |