… | |
… | |
35 | |
35 | |
36 | This module converts Perl data structures to JSON and vice versa. Its |
36 | This module converts Perl data structures to JSON and vice versa. Its |
37 | primary goal is to be I<correct> and its secondary goal is to be |
37 | primary goal is to be I<correct> and its secondary goal is to be |
38 | I<fast>. To reach the latter goal it was written in C. |
38 | I<fast>. To reach the latter goal it was written in C. |
39 | |
39 | |
40 | Beginning with version 2.0 of the JSON module, when both JSON and |
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41 | JSON::XS are installed, then JSON will fall back on JSON::XS (this can be |
|
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42 | overridden) with no overhead due to emulation (by inheriting constructor |
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43 | and methods). If JSON::XS is not available, it will fall back to the |
|
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44 | compatible JSON::PP module as backend, so using JSON instead of JSON::XS |
|
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45 | gives you a portable JSON API that can be fast when you need and doesn't |
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46 | require a C compiler when that is a problem. |
|
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47 | |
|
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48 | As this is the n-th-something JSON module on CPAN, what was the reason |
|
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49 | to write yet another JSON module? While it seems there are many JSON |
|
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50 | modules, none of them correctly handle all corner cases, and in most cases |
|
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51 | their maintainers are unresponsive, gone missing, or not listening to bug |
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52 | reports for other reasons. |
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53 | |
|
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54 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
40 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
55 | vice versa. |
41 | vice versa. |
56 | |
42 | |
57 | =head2 FEATURES |
43 | =head2 FEATURES |
58 | |
44 | |
59 | =over 4 |
45 | =over |
60 | |
46 | |
61 | =item * correct Unicode handling |
47 | =item * correct Unicode handling |
62 | |
48 | |
63 | This module knows how to handle Unicode, documents how and when it does |
49 | This module knows how to handle Unicode, documents how and when it does |
64 | so, and even documents what "correct" means. |
50 | so, and even documents what "correct" means. |
… | |
… | |
101 | |
87 | |
102 | package JSON::XS; |
88 | package JSON::XS; |
103 | |
89 | |
104 | use common::sense; |
90 | use common::sense; |
105 | |
91 | |
106 | our $VERSION = '3.0'; |
92 | our $VERSION = '4.02'; |
107 | our @ISA = qw(Exporter); |
93 | our @ISA = qw(Exporter); |
108 | |
94 | |
109 | our @EXPORT = qw(encode_json decode_json); |
95 | our @EXPORT = qw(encode_json decode_json); |
110 | |
96 | |
111 | use Exporter; |
97 | use Exporter; |
… | |
… | |
116 | =head1 FUNCTIONAL INTERFACE |
102 | =head1 FUNCTIONAL INTERFACE |
117 | |
103 | |
118 | The following convenience methods are provided by this module. They are |
104 | The following convenience methods are provided by this module. They are |
119 | exported by default: |
105 | exported by default: |
120 | |
106 | |
121 | =over 4 |
107 | =over |
122 | |
108 | |
123 | =item $json_text = encode_json $perl_scalar |
109 | =item $json_text = encode_json $perl_scalar |
124 | |
110 | |
125 | Converts the given Perl data structure to a UTF-8 encoded, binary string |
111 | Converts the given Perl data structure to a UTF-8 encoded, binary string |
126 | (that is, the string contains octets only). Croaks on error. |
112 | (that is, the string contains octets only). Croaks on error. |
… | |
… | |
131 | |
117 | |
132 | Except being faster. |
118 | Except being faster. |
133 | |
119 | |
134 | =item $perl_scalar = decode_json $json_text |
120 | =item $perl_scalar = decode_json $json_text |
135 | |
121 | |
136 | The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries |
122 | The opposite of C<encode_json>: expects a UTF-8 (binary) string and tries |
137 | to parse that as an UTF-8 encoded JSON text, returning the resulting |
123 | to parse that as a UTF-8 encoded JSON text, returning the resulting |
138 | reference. Croaks on error. |
124 | reference. Croaks on error. |
139 | |
125 | |
140 | This function call is functionally identical to: |
126 | This function call is functionally identical to: |
141 | |
127 | |
142 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
128 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
… | |
… | |
149 | =head1 A FEW NOTES ON UNICODE AND PERL |
135 | =head1 A FEW NOTES ON UNICODE AND PERL |
150 | |
136 | |
151 | Since this often leads to confusion, here are a few very clear words on |
137 | Since this often leads to confusion, here are a few very clear words on |
152 | how Unicode works in Perl, modulo bugs. |
138 | how Unicode works in Perl, modulo bugs. |
153 | |
139 | |
154 | =over 4 |
140 | =over |
155 | |
141 | |
156 | =item 1. Perl strings can store characters with ordinal values > 255. |
142 | =item 1. Perl strings can store characters with ordinal values > 255. |
157 | |
143 | |
158 | This enables you to store Unicode characters as single characters in a |
144 | This enables you to store Unicode characters as single characters in a |
159 | Perl string - very natural. |
145 | Perl string - very natural. |
… | |
… | |
197 | =head1 OBJECT-ORIENTED INTERFACE |
183 | =head1 OBJECT-ORIENTED INTERFACE |
198 | |
184 | |
199 | The object oriented interface lets you configure your own encoding or |
185 | The object oriented interface lets you configure your own encoding or |
200 | decoding style, within the limits of supported formats. |
186 | decoding style, within the limits of supported formats. |
201 | |
187 | |
202 | =over 4 |
188 | =over |
203 | |
189 | |
204 | =item $json = new JSON::XS |
190 | =item $json = new JSON::XS |
205 | |
191 | |
206 | Creates a new JSON::XS object that can be used to de/encode JSON |
192 | Creates a new JSON::XS object that can be used to de/encode JSON |
207 | strings. All boolean flags described below are by default I<disabled>. |
193 | strings. All boolean flags described below are by default I<disabled> |
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194 | (with the exception of C<allow_nonref>, which defaults to I<enabled> since |
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195 | version C<4.0>). |
208 | |
196 | |
209 | The mutators for flags all return the JSON object again and thus calls can |
197 | The mutators for flags all return the JSON object again and thus calls can |
210 | be chained: |
198 | be chained: |
211 | |
199 | |
212 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
200 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
… | |
… | |
270 | |
258 | |
271 | =item $enabled = $json->get_utf8 |
259 | =item $enabled = $json->get_utf8 |
272 | |
260 | |
273 | If C<$enable> is true (or missing), then the C<encode> method will encode |
261 | If C<$enable> is true (or missing), then the C<encode> method will encode |
274 | the JSON result into UTF-8, as required by many protocols, while the |
262 | the JSON result into UTF-8, as required by many protocols, while the |
275 | C<decode> method expects to be handled an UTF-8-encoded string. Please |
263 | C<decode> method expects to be handed a UTF-8-encoded string. Please |
276 | note that UTF-8-encoded strings do not contain any characters outside the |
264 | note that UTF-8-encoded strings do not contain any characters outside the |
277 | range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
265 | range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
278 | versions, enabling this option might enable autodetection of the UTF-16 |
266 | versions, enabling this option might enable autodetection of the UTF-16 |
279 | and UTF-32 encoding families, as described in RFC4627. |
267 | and UTF-32 encoding families, as described in RFC4627. |
280 | |
268 | |
… | |
… | |
365 | |
353 | |
366 | =item $enabled = $json->get_relaxed |
354 | =item $enabled = $json->get_relaxed |
367 | |
355 | |
368 | If C<$enable> is true (or missing), then C<decode> will accept some |
356 | If C<$enable> is true (or missing), then C<decode> will accept some |
369 | extensions to normal JSON syntax (see below). C<encode> will not be |
357 | extensions to normal JSON syntax (see below). C<encode> will not be |
370 | affected in anyway. I<Be aware that this option makes you accept invalid |
358 | affected in any way. I<Be aware that this option makes you accept invalid |
371 | JSON texts as if they were valid!>. I suggest only to use this option to |
359 | JSON texts as if they were valid!>. I suggest only to use this option to |
372 | parse application-specific files written by humans (configuration files, |
360 | parse application-specific files written by humans (configuration files, |
373 | resource files etc.) |
361 | resource files etc.) |
374 | |
362 | |
375 | If C<$enable> is false (the default), then C<decode> will only accept |
363 | If C<$enable> is false (the default), then C<decode> will only accept |
376 | valid JSON texts. |
364 | valid JSON texts. |
377 | |
365 | |
378 | Currently accepted extensions are: |
366 | Currently accepted extensions are: |
379 | |
367 | |
380 | =over 4 |
368 | =over |
381 | |
369 | |
382 | =item * list items can have an end-comma |
370 | =item * list items can have an end-comma |
383 | |
371 | |
384 | JSON I<separates> array elements and key-value pairs with commas. This |
372 | JSON I<separates> array elements and key-value pairs with commas. This |
385 | can be annoying if you write JSON texts manually and want to be able to |
373 | can be annoying if you write JSON texts manually and want to be able to |
… | |
… | |
404 | [ |
392 | [ |
405 | 1, # this comment not allowed in JSON |
393 | 1, # this comment not allowed in JSON |
406 | # neither this one... |
394 | # neither this one... |
407 | ] |
395 | ] |
408 | |
396 | |
|
|
397 | =item * literal ASCII TAB characters in strings |
|
|
398 | |
|
|
399 | Literal ASCII TAB characters are now allowed in strings (and treated as |
|
|
400 | C<\t>). |
|
|
401 | |
|
|
402 | [ |
|
|
403 | "Hello\tWorld", |
|
|
404 | "Hello<TAB>World", # literal <TAB> would not normally be allowed |
|
|
405 | ] |
|
|
406 | |
409 | =back |
407 | =back |
410 | |
408 | |
411 | =item $json = $json->canonical ([$enable]) |
409 | =item $json = $json->canonical ([$enable]) |
412 | |
410 | |
413 | =item $enabled = $json->get_canonical |
411 | =item $enabled = $json->get_canonical |
… | |
… | |
431 | |
429 | |
432 | =item $json = $json->allow_nonref ([$enable]) |
430 | =item $json = $json->allow_nonref ([$enable]) |
433 | |
431 | |
434 | =item $enabled = $json->get_allow_nonref |
432 | =item $enabled = $json->get_allow_nonref |
435 | |
433 | |
|
|
434 | Unlike other boolean options, this opotion is enabled by default beginning |
|
|
435 | with version C<4.0>. See L<SECURITY CONSIDERATIONS> for the gory details. |
|
|
436 | |
436 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
437 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
437 | non-reference into its corresponding string, number or null JSON value, |
438 | non-reference into its corresponding string, number or null JSON value, |
438 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
439 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
439 | values instead of croaking. |
440 | values instead of croaking. |
440 | |
441 | |
441 | If C<$enable> is false, then the C<encode> method will croak if it isn't |
442 | If C<$enable> is false, then the C<encode> method will croak if it isn't |
442 | passed an arrayref or hashref, as JSON texts must either be an object |
443 | passed an arrayref or hashref, as JSON texts must either be an object |
443 | or array. Likewise, C<decode> will croak if given something that is not a |
444 | or array. Likewise, C<decode> will croak if given something that is not a |
444 | JSON object or array. |
445 | JSON object or array. |
445 | |
446 | |
446 | Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, |
447 | Example, encode a Perl scalar as JSON value without enabled C<allow_nonref>, |
447 | resulting in an invalid JSON text: |
448 | resulting in an error: |
448 | |
449 | |
449 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
450 | JSON::XS->new->allow_nonref (0)->encode ("Hello, World!") |
450 | => "Hello, World!" |
451 | => hash- or arrayref expected... |
451 | |
452 | |
452 | =item $json = $json->allow_unknown ([$enable]) |
453 | =item $json = $json->allow_unknown ([$enable]) |
453 | |
454 | |
454 | =item $enabled = $json->get_allow_unknown |
455 | =item $enabled = $json->get_allow_unknown |
455 | |
456 | |
… | |
… | |
505 | |
506 | |
506 | This setting has no effect on C<decode>. |
507 | This setting has no effect on C<decode>. |
507 | |
508 | |
508 | =item $json = $json->allow_tags ([$enable]) |
509 | =item $json = $json->allow_tags ([$enable]) |
509 | |
510 | |
510 | =item $enabled = $json->allow_tags |
511 | =item $enabled = $json->get_allow_tags |
511 | |
512 | |
512 | See L<OBJECT SERIALISATION> for details. |
513 | See L<OBJECT SERIALISATION> for details. |
513 | |
514 | |
514 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
515 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
515 | blessed object, will check for the availability of the C<FREEZE> method on |
516 | blessed object, will check for the availability of the C<FREEZE> method on |
… | |
… | |
521 | |
522 | |
522 | If C<$enable> is false (the default), then C<encode> will not consider |
523 | 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 | 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. |
525 | in C<decode>, as if tags were not part of the grammar. |
525 | |
526 | |
|
|
527 | =item $json->boolean_values ([$false, $true]) |
|
|
528 | |
|
|
529 | =item ($false, $true) = $json->get_boolean_values |
|
|
530 | |
|
|
531 | By default, JSON booleans will be decoded as overloaded |
|
|
532 | C<$Types::Serialiser::false> and C<$Types::Serialiser::true> objects. |
|
|
533 | |
|
|
534 | With this method you can specify your own boolean values for decoding - |
|
|
535 | on decode, JSON C<false> will be decoded as a copy of C<$false>, and JSON |
|
|
536 | C<true> will be decoded as C<$true> ("copy" here is the same thing as |
|
|
537 | assigning a value to another variable, i.e. C<$copy = $false>). |
|
|
538 | |
|
|
539 | Calling this method without any arguments will reset the booleans |
|
|
540 | to their default values. |
|
|
541 | |
|
|
542 | C<get_boolean_values> will return both C<$false> and C<$true> values, or |
|
|
543 | the empty list when they are set to the default. |
|
|
544 | |
526 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
545 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
527 | |
546 | |
528 | When C<$coderef> is specified, it will be called from C<decode> each |
547 | When C<$coderef> is specified, it will be called from C<decode> each |
529 | time it decodes a JSON object. The only argument is a reference to the |
548 | time it decodes a JSON object. The only argument is a reference to |
530 | newly-created hash. If the code references returns a single scalar (which |
549 | the newly-created hash. If the code reference returns a single scalar |
531 | need not be a reference), this value (i.e. a copy of that scalar to avoid |
550 | (which need not be a reference), this value (or rather a copy of it) is |
532 | aliasing) is inserted into the deserialised data structure. If it returns |
551 | inserted into the deserialised data structure. If it returns an empty |
533 | an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the |
552 | list (NOTE: I<not> C<undef>, which is a valid scalar), the original |
534 | original deserialised hash will be inserted. This setting can slow down |
553 | deserialised hash will be inserted. This setting can slow down decoding |
535 | decoding considerably. |
554 | considerably. |
536 | |
555 | |
537 | When C<$coderef> is omitted or undefined, any existing callback will |
556 | When C<$coderef> is omitted or undefined, any existing callback will |
538 | be removed and C<decode> will not change the deserialised hash in any |
557 | be removed and C<decode> will not change the deserialised hash in any |
539 | way. |
558 | way. |
540 | |
559 | |
… | |
… | |
687 | |
706 | |
688 | This is useful if your JSON texts are not delimited by an outer protocol |
707 | This is useful if your JSON texts are not delimited by an outer protocol |
689 | and you need to know where the JSON text ends. |
708 | and you need to know where the JSON text ends. |
690 | |
709 | |
691 | JSON::XS->new->decode_prefix ("[1] the tail") |
710 | JSON::XS->new->decode_prefix ("[1] the tail") |
692 | => ([], 3) |
711 | => ([1], 3) |
693 | |
712 | |
694 | =back |
713 | =back |
695 | |
714 | |
696 | |
715 | |
697 | =head1 INCREMENTAL PARSING |
716 | =head1 INCREMENTAL PARSING |
… | |
… | |
714 | to set resource limits (e.g. C<max_size>) to ensure the parser will stop |
733 | to set resource limits (e.g. C<max_size>) to ensure the parser will stop |
715 | parsing in the presence if syntax errors. |
734 | parsing in the presence if syntax errors. |
716 | |
735 | |
717 | The following methods implement this incremental parser. |
736 | The following methods implement this incremental parser. |
718 | |
737 | |
719 | =over 4 |
738 | =over |
720 | |
739 | |
721 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
740 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
722 | |
741 | |
723 | This is the central parsing function. It can both append new text and |
742 | This is the central parsing function. It can both append new text and |
724 | extract objects from the stream accumulated so far (both of these |
743 | extract objects from the stream accumulated so far (both of these |
… | |
… | |
738 | C<incr_skip> to skip the erroneous part). This is the most common way of |
757 | C<incr_skip> to skip the erroneous part). This is the most common way of |
739 | using the method. |
758 | using the method. |
740 | |
759 | |
741 | And finally, in list context, it will try to extract as many objects |
760 | And finally, in list context, it will try to extract as many objects |
742 | from the stream as it can find and return them, or the empty list |
761 | from the stream as it can find and return them, or the empty list |
743 | otherwise. For this to work, there must be no separators between the JSON |
762 | otherwise. For this to work, there must be no separators (other than |
744 | objects or arrays, instead they must be concatenated back-to-back. If |
763 | whitespace) between the JSON objects or arrays, instead they must be |
745 | an error occurs, an exception will be raised as in the scalar context |
764 | concatenated back-to-back. If an error occurs, an exception will be |
746 | case. Note that in this case, any previously-parsed JSON texts will be |
765 | raised as in the scalar context case. Note that in this case, any |
747 | lost. |
766 | previously-parsed JSON texts will be lost. |
748 | |
767 | |
749 | Example: Parse some JSON arrays/objects in a given string and return |
768 | Example: Parse some JSON arrays/objects in a given string and return |
750 | them. |
769 | them. |
751 | |
770 | |
752 | my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]"); |
771 | my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]"); |
… | |
… | |
759 | all other circumstances you must not call this function (I mean it. |
778 | all other circumstances you must not call this function (I mean it. |
760 | although in simple tests it might actually work, it I<will> fail under |
779 | although in simple tests it might actually work, it I<will> fail under |
761 | real world conditions). As a special exception, you can also call this |
780 | real world conditions). As a special exception, you can also call this |
762 | method before having parsed anything. |
781 | method before having parsed anything. |
763 | |
782 | |
|
|
783 | That means you can only use this function to look at or manipulate text |
|
|
784 | before or after complete JSON objects, not while the parser is in the |
|
|
785 | middle of parsing a JSON object. |
|
|
786 | |
764 | This function is useful in two cases: a) finding the trailing text after a |
787 | This function is useful in two cases: a) finding the trailing text after a |
765 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
788 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
766 | (such as commas). |
789 | (such as commas). |
767 | |
790 | |
768 | =item $json->incr_skip |
791 | =item $json->incr_skip |
… | |
… | |
787 | |
810 | |
788 | =back |
811 | =back |
789 | |
812 | |
790 | =head2 LIMITATIONS |
813 | =head2 LIMITATIONS |
791 | |
814 | |
792 | All options that affect decoding are supported, except |
815 | The incremental parser is a non-exact parser: it works by gathering as |
793 | C<allow_nonref>. The reason for this is that it cannot be made to work |
816 | much text as possible that I<could> be a valid JSON text, followed by |
794 | sensibly: JSON objects and arrays are self-delimited, i.e. you can |
817 | trying to decode it. |
795 | concatenate them back to back and still decode them perfectly. This does |
|
|
796 | not hold true for JSON numbers, however. |
|
|
797 | |
818 | |
798 | For example, is the string C<1> a single JSON number, or is it simply the |
819 | That means it sometimes needs to read more data than strictly necessary to |
799 | start of C<12>? Or is C<12> a single JSON number, or the concatenation |
820 | diagnose an invalid JSON text. For example, after parsing the following |
800 | of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS |
821 | fragment, the parser I<could> stop with an error, as this fragment |
801 | takes the conservative route and disallows this case. |
822 | I<cannot> be the beginning of a valid JSON text: |
|
|
823 | |
|
|
824 | [, |
|
|
825 | |
|
|
826 | In reality, hopwever, the parser might continue to read data until a |
|
|
827 | length limit is exceeded or it finds a closing bracket. |
802 | |
828 | |
803 | =head2 EXAMPLES |
829 | =head2 EXAMPLES |
804 | |
830 | |
805 | Some examples will make all this clearer. First, a simple example that |
831 | Some examples will make all this clearer. First, a simple example that |
806 | works similarly to C<decode_prefix>: We want to decode the JSON object at |
832 | works similarly to C<decode_prefix>: We want to decode the JSON object at |
… | |
… | |
950 | refers to the abstract Perl language itself. |
976 | refers to the abstract Perl language itself. |
951 | |
977 | |
952 | |
978 | |
953 | =head2 JSON -> PERL |
979 | =head2 JSON -> PERL |
954 | |
980 | |
955 | =over 4 |
981 | =over |
956 | |
982 | |
957 | =item object |
983 | =item object |
958 | |
984 | |
959 | A JSON object becomes a reference to a hash in Perl. No ordering of object |
985 | A JSON object becomes a reference to a hash in Perl. No ordering of object |
960 | keys is preserved (JSON does not preserve object key ordering itself). |
986 | keys is preserved (JSON does not preserve object key ordering itself). |
… | |
… | |
1028 | |
1054 | |
1029 | The mapping from Perl to JSON is slightly more difficult, as Perl is a |
1055 | The mapping from Perl to JSON is slightly more difficult, as Perl is a |
1030 | truly typeless language, so we can only guess which JSON type is meant by |
1056 | truly typeless language, so we can only guess which JSON type is meant by |
1031 | a Perl value. |
1057 | a Perl value. |
1032 | |
1058 | |
1033 | =over 4 |
1059 | =over |
1034 | |
1060 | |
1035 | =item hash references |
1061 | =item hash references |
1036 | |
1062 | |
1037 | Perl hash references become JSON objects. As there is no inherent |
1063 | Perl hash references become JSON objects. As there is no inherent |
1038 | ordering in hash keys (or JSON objects), they will usually be encoded |
1064 | ordering in hash keys (or JSON objects), they will usually be encoded |
… | |
… | |
1127 | |
1153 | |
1128 | What happens when C<JSON::XS> encounters a Perl object depends on the |
1154 | 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 |
1155 | C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are |
1130 | used in this order: |
1156 | used in this order: |
1131 | |
1157 | |
1132 | =over 4 |
1158 | =over |
1133 | |
1159 | |
1134 | =item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method. |
1160 | =item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method. |
1135 | |
1161 | |
1136 | In this case, C<JSON::XS> uses the L<Types::Serialiser> object |
1162 | In this case, C<JSON::XS> uses the L<Types::Serialiser> object |
1137 | serialisation protocol to create a tagged JSON value, using a nonstandard |
1163 | serialisation protocol to create a tagged JSON value, using a nonstandard |
… | |
… | |
1248 | takes those codepoint numbers and I<encodes> them, in our case into |
1274 | takes those codepoint numbers and I<encodes> them, in our case into |
1249 | octets. Unicode is (among other things) a codeset, UTF-8 is an encoding, |
1275 | octets. Unicode is (among other things) a codeset, UTF-8 is an encoding, |
1250 | and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at |
1276 | and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at |
1251 | the same time, which can be confusing. |
1277 | the same time, which can be confusing. |
1252 | |
1278 | |
1253 | =over 4 |
1279 | =over |
1254 | |
1280 | |
1255 | =item C<utf8> flag disabled |
1281 | =item C<utf8> flag disabled |
1256 | |
1282 | |
1257 | When C<utf8> is disabled (the default), then C<encode>/C<decode> generate |
1283 | When C<utf8> is disabled (the default), then C<encode>/C<decode> generate |
1258 | and expect Unicode strings, that is, characters with high ordinal Unicode |
1284 | and expect Unicode strings, that is, characters with high ordinal Unicode |
… | |
… | |
1275 | expect your input strings to be encoded as UTF-8, that is, no "character" |
1301 | expect your input strings to be encoded as UTF-8, that is, no "character" |
1276 | of the input string must have any value > 255, as UTF-8 does not allow |
1302 | of the input string must have any value > 255, as UTF-8 does not allow |
1277 | that. |
1303 | that. |
1278 | |
1304 | |
1279 | The C<utf8> flag therefore switches between two modes: disabled means you |
1305 | The C<utf8> flag therefore switches between two modes: disabled means you |
1280 | will get a Unicode string in Perl, enabled means you get an UTF-8 encoded |
1306 | will get a Unicode string in Perl, enabled means you get a UTF-8 encoded |
1281 | octet/binary string in Perl. |
1307 | octet/binary string in Perl. |
1282 | |
1308 | |
1283 | =item C<latin1> or C<ascii> flags enabled |
1309 | =item C<latin1> or C<ascii> flags enabled |
1284 | |
1310 | |
1285 | With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters |
1311 | With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters |
… | |
… | |
1417 | general you should not try to generate YAML with a JSON generator or vice |
1443 | general you should not try to generate YAML with a JSON generator or vice |
1418 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
1444 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
1419 | high that you will run into severe interoperability problems when you |
1445 | high that you will run into severe interoperability problems when you |
1420 | least expect it. |
1446 | least expect it. |
1421 | |
1447 | |
1422 | =over 4 |
1448 | =over |
1423 | |
1449 | |
1424 | =item (*) |
1450 | =item (*) |
1425 | |
1451 | |
1426 | I have been pressured multiple times by Brian Ingerson (one of the |
1452 | I have been pressured multiple times by Brian Ingerson (one of the |
1427 | authors of the YAML specification) to remove this paragraph, despite him |
1453 | authors of the YAML specification) to remove this paragraph, despite him |
… | |
… | |
1553 | are browser design bugs, but it is still you who will have to deal with |
1579 | are browser design bugs, but it is still you who will have to deal with |
1554 | it, as major browser developers care only for features, not about getting |
1580 | it, as major browser developers care only for features, not about getting |
1555 | security right). |
1581 | security right). |
1556 | |
1582 | |
1557 | |
1583 | |
|
|
1584 | =head2 "OLD" VS. "NEW" JSON (RFC4627 VS. RFC7159) |
|
|
1585 | |
|
|
1586 | JSON originally required JSON texts to represent an array or object - |
|
|
1587 | scalar values were explicitly not allowed. This has changed, and versions |
|
|
1588 | of JSON::XS beginning with C<4.0> reflect this by allowing scalar values |
|
|
1589 | by default. |
|
|
1590 | |
|
|
1591 | One reason why one might not want this is that this removes a fundamental |
|
|
1592 | property of JSON texts, namely that they are self-delimited and |
|
|
1593 | self-contained, or in other words, you could take any number of "old" |
|
|
1594 | JSON texts and paste them together, and the result would be unambiguously |
|
|
1595 | parseable: |
|
|
1596 | |
|
|
1597 | [1,3]{"k":5}[][null] # four JSON texts, without doubt |
|
|
1598 | |
|
|
1599 | By allowing scalars, this property is lost: in the following example, is |
|
|
1600 | this one JSON text (the number 12) or two JSON texts (the numbers 1 and |
|
|
1601 | 2): |
|
|
1602 | |
|
|
1603 | 12 # could be 12, or 1 and 2 |
|
|
1604 | |
|
|
1605 | Another lost property of "old" JSON is that no lookahead is required to |
|
|
1606 | know the end of a JSON text, i.e. the JSON text definitely ended at the |
|
|
1607 | last C<]> or C<}> character, there was no need to read extra characters. |
|
|
1608 | |
|
|
1609 | For example, a viable network protocol with "old" JSON was to simply |
|
|
1610 | exchange JSON texts without delimiter. For "new" JSON, you have to use a |
|
|
1611 | suitable delimiter (such as a newline) after every JSON text or ensure you |
|
|
1612 | never encode/decode scalar values. |
|
|
1613 | |
|
|
1614 | Most protocols do work by only transferring arrays or objects, and the |
|
|
1615 | easiest way to avoid problems with the "new" JSON definition is to |
|
|
1616 | explicitly disallow scalar values in your encoder and decoder: |
|
|
1617 | |
|
|
1618 | $json_coder = JSON::XS->new->allow_nonref (0) |
|
|
1619 | |
|
|
1620 | This is a somewhat unhappy situation, and the blame can fully be put on |
|
|
1621 | JSON's inmventor, Douglas Crockford, who unilaterally changed the format |
|
|
1622 | in 2006 without consulting the IETF, forcing the IETF to either fork the |
|
|
1623 | format or go with it (as I was told, the IETF wasn't amused). |
|
|
1624 | |
|
|
1625 | |
|
|
1626 | =head1 RELATIONSHIP WITH I-JSON |
|
|
1627 | |
|
|
1628 | JSON is a somewhat sloppily-defined format - it carries around obvious |
|
|
1629 | Javascript baggage, such as not really defining number range, probably |
|
|
1630 | because Javascript only has one type of numbers: IEEE 64 bit floats |
|
|
1631 | ("binary64"). |
|
|
1632 | |
|
|
1633 | For this reaosn, RFC7493 defines "Internet JSON", which is a restricted |
|
|
1634 | subset of JSON that is supposedly more interoperable on the internet. |
|
|
1635 | |
|
|
1636 | While C<JSON::XS> does not offer specific support for I-JSON, it of course |
|
|
1637 | accepts valid I-JSON and by default implements some of the limitations |
|
|
1638 | of I-JSON, such as parsing numbers as perl numbers, which are usually a |
|
|
1639 | superset of binary64 numbers. |
|
|
1640 | |
|
|
1641 | To generate I-JSON, follow these rules: |
|
|
1642 | |
|
|
1643 | =over |
|
|
1644 | |
|
|
1645 | =item * always generate UTF-8 |
|
|
1646 | |
|
|
1647 | I-JSON must be encoded in UTF-8, the default for C<encode_json>. |
|
|
1648 | |
|
|
1649 | =item * numbers should be within IEEE 754 binary64 range |
|
|
1650 | |
|
|
1651 | Basically all existing perl installations use binary64 to represent |
|
|
1652 | floating point numbers, so all you need to do is to avoid large integers. |
|
|
1653 | |
|
|
1654 | =item * objects must not have duplicate keys |
|
|
1655 | |
|
|
1656 | This is trivially done, as C<JSON::XS> does not allow duplicate keys. |
|
|
1657 | |
|
|
1658 | =item * do not generate scalar JSON texts, use C<< ->allow_nonref (0) >> |
|
|
1659 | |
|
|
1660 | I-JSON strongly requests you to only encode arrays and objects into JSON. |
|
|
1661 | |
|
|
1662 | =item * times should be strings in ISO 8601 format |
|
|
1663 | |
|
|
1664 | There are a myriad of modules on CPAN dealing with ISO 8601 - search for |
|
|
1665 | C<ISO8601> on CPAN and use one. |
|
|
1666 | |
|
|
1667 | =item * encode binary data as base64 |
|
|
1668 | |
|
|
1669 | While it's tempting to just dump binary data as a string (and let |
|
|
1670 | C<JSON::XS> do the escaping), for I-JSON, it's I<recommended> to encode |
|
|
1671 | binary data as base64. |
|
|
1672 | |
|
|
1673 | =back |
|
|
1674 | |
|
|
1675 | There are some other considerations - read RFC7493 for the details if |
|
|
1676 | interested. |
|
|
1677 | |
|
|
1678 | |
1558 | =head1 INTEROPERABILITY WITH OTHER MODULES |
1679 | =head1 INTEROPERABILITY WITH OTHER MODULES |
1559 | |
1680 | |
1560 | C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean |
1681 | C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean |
1561 | constants. That means that the JSON true and false values will be |
1682 | constants. That means that the JSON true and false values will be |
1562 | comaptible to true and false values of iother modules that do the same, |
1683 | comaptible to true and false values of other modules that do the same, |
1563 | such as L<JSON::PP> and L<CBOR::XS>. |
1684 | such as L<JSON::PP> and L<CBOR::XS>. |
1564 | |
1685 | |
1565 | |
1686 | |
|
|
1687 | =head1 INTEROPERABILITY WITH OTHER JSON DECODERS |
|
|
1688 | |
|
|
1689 | As long as you only serialise data that can be directly expressed in JSON, |
|
|
1690 | C<JSON::XS> is incapable of generating invalid JSON output (modulo bugs, |
|
|
1691 | but C<JSON::XS> has found more bugs in the official JSON testsuite (1) |
|
|
1692 | than the official JSON testsuite has found in C<JSON::XS> (0)). |
|
|
1693 | |
|
|
1694 | When you have trouble decoding JSON generated by this module using other |
|
|
1695 | decoders, then it is very likely that you have an encoding mismatch or the |
|
|
1696 | other decoder is broken. |
|
|
1697 | |
|
|
1698 | When decoding, C<JSON::XS> is strict by default and will likely catch all |
|
|
1699 | errors. There are currently two settings that change this: C<relaxed> |
|
|
1700 | makes C<JSON::XS> accept (but not generate) some non-standard extensions, |
|
|
1701 | and C<allow_tags> will allow you to encode and decode Perl objects, at the |
|
|
1702 | cost of not outputting valid JSON anymore. |
|
|
1703 | |
|
|
1704 | =head2 TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS |
|
|
1705 | |
|
|
1706 | When you use C<allow_tags> to use the extended (and also nonstandard and |
|
|
1707 | invalid) JSON syntax for serialised objects, and you still want to decode |
|
|
1708 | the generated When you want to serialise objects, you can run a regex |
|
|
1709 | to replace the tagged syntax by standard JSON arrays (it only works for |
|
|
1710 | "normal" package names without comma, newlines or single colons). First, |
|
|
1711 | the readable Perl version: |
|
|
1712 | |
|
|
1713 | # if your FREEZE methods return no values, you need this replace first: |
|
|
1714 | $json =~ s/\( \s* (" (?: [^\\":,]+|\\.|::)* ") \s* \) \s* \[\s*\]/[$1]/gx; |
|
|
1715 | |
|
|
1716 | # this works for non-empty constructor arg lists: |
|
|
1717 | $json =~ s/\( \s* (" (?: [^\\":,]+|\\.|::)* ") \s* \) \s* \[/[$1,/gx; |
|
|
1718 | |
|
|
1719 | And here is a less readable version that is easy to adapt to other |
|
|
1720 | languages: |
|
|
1721 | |
|
|
1722 | $json =~ s/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/[$1,/g; |
|
|
1723 | |
|
|
1724 | Here is an ECMAScript version (same regex): |
|
|
1725 | |
|
|
1726 | json = json.replace (/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/g, "[$1,"); |
|
|
1727 | |
|
|
1728 | Since this syntax converts to standard JSON arrays, it might be hard to |
|
|
1729 | distinguish serialised objects from normal arrays. You can prepend a |
|
|
1730 | "magic number" as first array element to reduce chances of a collision: |
|
|
1731 | |
|
|
1732 | $json =~ s/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g; |
|
|
1733 | |
|
|
1734 | And after decoding the JSON text, you could walk the data |
|
|
1735 | structure looking for arrays with a first element of |
|
|
1736 | C<XU1peReLzT4ggEllLanBYq4G9VzliwKF>. |
|
|
1737 | |
|
|
1738 | The same approach can be used to create the tagged format with another |
|
|
1739 | encoder. First, you create an array with the magic string as first member, |
|
|
1740 | the classname as second, and constructor arguments last, encode it as part |
|
|
1741 | of your JSON structure, and then: |
|
|
1742 | |
|
|
1743 | $json =~ s/\[\s*"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s*,\s*("([^\\":,]+|\\.|::)*")\s*,/($1)[/g; |
|
|
1744 | |
|
|
1745 | Again, this has some limitations - the magic string must not be encoded |
|
|
1746 | with character escapes, and the constructor arguments must be non-empty. |
|
|
1747 | |
|
|
1748 | |
1566 | =head1 THREADS |
1749 | =head1 (I-)THREADS |
1567 | |
1750 | |
1568 | This module is I<not> guaranteed to be thread safe and there are no |
1751 | This module is I<not> guaranteed to be ithread (or MULTIPLICITY-) safe |
1569 | plans to change this until Perl gets thread support (as opposed to the |
1752 | and there are no plans to change this. Note that perl's builtin so-called |
1570 | horribly slow so-called "threads" which are simply slow and bloated |
1753 | threads/ithreads are officially deprecated and should not be used. |
1571 | process simulations - use fork, it's I<much> faster, cheaper, better). |
|
|
1572 | |
|
|
1573 | (It might actually work, but you have been warned). |
|
|
1574 | |
1754 | |
1575 | |
1755 | |
1576 | =head1 THE PERILS OF SETLOCALE |
1756 | =head1 THE PERILS OF SETLOCALE |
1577 | |
1757 | |
1578 | Sometimes people avoid the Perl locale support and directly call the |
1758 | Sometimes people avoid the Perl locale support and directly call the |
… | |
… | |
1587 | categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>. |
1767 | categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>. |
1588 | |
1768 | |
1589 | If you need C<LC_NUMERIC>, you should enable it only around the code that |
1769 | If you need C<LC_NUMERIC>, you should enable it only around the code that |
1590 | actually needs it (avoiding stringification of numbers), and restore it |
1770 | actually needs it (avoiding stringification of numbers), and restore it |
1591 | afterwards. |
1771 | afterwards. |
|
|
1772 | |
|
|
1773 | |
|
|
1774 | =head1 SOME HISTORY |
|
|
1775 | |
|
|
1776 | At the time this module was created there already were a number of JSON |
|
|
1777 | modules available on CPAN, so what was the reason to write yet another |
|
|
1778 | JSON module? While it seems there are many JSON modules, none of them |
|
|
1779 | correctly handled all corner cases, and in most cases their maintainers |
|
|
1780 | are unresponsive, gone missing, or not listening to bug reports for other |
|
|
1781 | reasons. |
|
|
1782 | |
|
|
1783 | Beginning with version 2.0 of the JSON module, when both JSON and |
|
|
1784 | JSON::XS are installed, then JSON will fall back on JSON::XS (this can be |
|
|
1785 | overridden) with no overhead due to emulation (by inheriting constructor |
|
|
1786 | and methods). If JSON::XS is not available, it will fall back to the |
|
|
1787 | compatible JSON::PP module as backend, so using JSON instead of JSON::XS |
|
|
1788 | gives you a portable JSON API that can be fast when you need it and |
|
|
1789 | doesn't require a C compiler when that is a problem. |
|
|
1790 | |
|
|
1791 | Somewhere around version 3, this module was forked into |
|
|
1792 | C<Cpanel::JSON::XS>, because its maintainer had serious trouble |
|
|
1793 | understanding JSON and insisted on a fork with many bugs "fixed" that |
|
|
1794 | weren't actually bugs, while spreading FUD about this module without |
|
|
1795 | actually giving any details on his accusations. You be the judge, but |
|
|
1796 | in my personal opinion, if you want quality, you will stay away from |
|
|
1797 | dangerous forks like that. |
1592 | |
1798 | |
1593 | |
1799 | |
1594 | =head1 BUGS |
1800 | =head1 BUGS |
1595 | |
1801 | |
1596 | While the goal of this module is to be correct, that unfortunately does |
1802 | While the goal of this module is to be correct, that unfortunately does |