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1 : chenry 1.1 package JSON;
2 :    
3 :    
4 :     use strict;
5 :     use Carp ();
6 :     use base qw(Exporter);
7 :     @JSON::EXPORT = qw(from_json to_json jsonToObj objToJson encode_json decode_json);
8 :    
9 :     BEGIN {
10 :     $JSON::VERSION = '2.21';
11 :     $JSON::DEBUG = 0 unless (defined $JSON::DEBUG);
12 :     }
13 :    
14 :     my $Module_XS = 'JSON::XS';
15 :     my $Module_PP = 'JSON::PP';
16 :     my $XS_Version = '2.27';
17 :    
18 :    
19 :     # XS and PP common methods
20 :    
21 :     my @PublicMethods = qw/
22 :     ascii latin1 utf8 pretty indent space_before space_after relaxed canonical allow_nonref
23 :     allow_blessed convert_blessed filter_json_object filter_json_single_key_object
24 :     shrink max_depth max_size encode decode decode_prefix allow_unknown
25 :     /;
26 :    
27 :     my @Properties = qw/
28 :     ascii latin1 utf8 indent space_before space_after relaxed canonical allow_nonref
29 :     allow_blessed convert_blessed shrink max_depth max_size allow_unknown
30 :     /;
31 :    
32 :     my @XSOnlyMethods = qw//; # Currently nothing
33 :    
34 :     my @PPOnlyMethods = qw/
35 :     indent_length sort_by
36 :     allow_singlequote allow_bignum loose allow_barekey escape_slash as_nonblessed
37 :     /; # JSON::PP specific
38 :    
39 :    
40 :     # used in _load_xs and _load_pp ($INSTALL_ONLY is not used currently)
41 :     my $_INSTALL_DONT_DIE = 1; # When _load_xs fails to load XS, don't die.
42 :     my $_INSTALL_ONLY = 2; # Don't call _set_methods()
43 :     my $_ALLOW_UNSUPPORTED = 0;
44 :     my $_UNIV_CONV_BLESSED = 0;
45 :    
46 :    
47 :     # Check the environment variable to decide worker module.
48 :    
49 :     unless ($JSON::Backend) {
50 :     $JSON::DEBUG and Carp::carp("Check used worker module...");
51 :    
52 :     my $backend = exists $ENV{PERL_JSON_BACKEND} ? $ENV{PERL_JSON_BACKEND} : 1;
53 :    
54 :     if ($backend eq '1' or $backend =~ /JSON::XS\s*,\s*JSON::PP/) {
55 :     _load_xs($_INSTALL_DONT_DIE) or _load_pp();
56 :     }
57 :     elsif ($backend eq '0' or $backend eq 'JSON::PP') {
58 :     _load_pp();
59 :     }
60 :     elsif ($backend eq '2' or $backend eq 'JSON::XS') {
61 :     _load_xs();
62 :     }
63 :     else {
64 :     Carp::croak "The value of environmental variable 'PERL_JSON_BACKEND' is invalid.";
65 :     }
66 :     }
67 :    
68 :    
69 :     sub import {
70 :     my $pkg = shift;
71 :     my @what_to_export;
72 :     my $no_export;
73 :    
74 :     for my $tag (@_) {
75 :     if ($tag eq '-support_by_pp') {
76 :     if (!$_ALLOW_UNSUPPORTED++) {
77 :     JSON::Backend::XS
78 :     ->support_by_pp(@PPOnlyMethods) if ($JSON::Backend eq $Module_XS);
79 :     }
80 :     next;
81 :     }
82 :     elsif ($tag eq '-no_export') {
83 :     $no_export++, next;
84 :     }
85 :     elsif ( $tag eq '-convert_blessed_universally' ) {
86 :     eval q|
87 :     require B;
88 :     *UNIVERSAL::TO_JSON = sub {
89 :     my $b_obj = B::svref_2object( $_[0] );
90 :     return $b_obj->isa('B::HV') ? { %{ $_[0] } }
91 :     : $b_obj->isa('B::AV') ? [ @{ $_[0] } ]
92 :     : undef
93 :     ;
94 :     }
95 :     | if ( !$_UNIV_CONV_BLESSED++ );
96 :     next;
97 :     }
98 :     push @what_to_export, $tag;
99 :     }
100 :    
101 :     return if ($no_export);
102 :    
103 :     __PACKAGE__->export_to_level(1, $pkg, @what_to_export);
104 :     }
105 :    
106 :    
107 :     # OBSOLETED
108 :    
109 :     sub jsonToObj {
110 :     my $alternative = 'from_json';
111 :     if (defined $_[0] and UNIVERSAL::isa($_[0], 'JSON')) {
112 :     shift @_; $alternative = 'decode';
113 :     }
114 :     Carp::carp "'jsonToObj' will be obsoleted. Please use '$alternative' instead.";
115 :     return JSON::from_json(@_);
116 :     };
117 :    
118 :     sub objToJson {
119 :     my $alternative = 'to_json';
120 :     if (defined $_[0] and UNIVERSAL::isa($_[0], 'JSON')) {
121 :     shift @_; $alternative = 'encode';
122 :     }
123 :     Carp::carp "'objToJson' will be obsoleted. Please use '$alternative' instead.";
124 :     JSON::to_json(@_);
125 :     };
126 :    
127 :    
128 :     # INTERFACES
129 :    
130 :     sub to_json ($@) {
131 :     my $json = new JSON;
132 :    
133 :     if (@_ == 2 and ref $_[1] eq 'HASH') {
134 :     my $opt = $_[1];
135 :     for my $method (keys %$opt) {
136 :     $json->$method( $opt->{$method} );
137 :     }
138 :     }
139 :    
140 :     $json->encode($_[0]);
141 :     }
142 :    
143 :    
144 :     sub from_json ($@) {
145 :     my $json = new JSON;
146 :    
147 :     if (@_ == 2 and ref $_[1] eq 'HASH') {
148 :     my $opt = $_[1];
149 :     for my $method (keys %$opt) {
150 :     $json->$method( $opt->{$method} );
151 :     }
152 :     }
153 :    
154 :     return $json->decode( $_[0] );
155 :     }
156 :    
157 :    
158 :     sub true { $JSON::true }
159 :    
160 :     sub false { $JSON::false }
161 :    
162 :     sub null { undef; }
163 :    
164 :    
165 :     sub require_xs_version { $XS_Version; }
166 :    
167 :     sub backend {
168 :     my $proto = shift;
169 :     $JSON::Backend;
170 :     }
171 :    
172 :     #*module = *backend;
173 :    
174 :    
175 :     sub is_xs {
176 :     return $_[0]->module eq $Module_XS;
177 :     }
178 :    
179 :    
180 :     sub is_pp {
181 :     return $_[0]->module eq $Module_PP;
182 :     }
183 :    
184 :    
185 :     sub pureperl_only_methods { @PPOnlyMethods; }
186 :    
187 :    
188 :     sub property {
189 :     my ($self, $name, $value) = @_;
190 :    
191 :     if (@_ == 1) {
192 :     my %props;
193 :     for $name (@Properties) {
194 :     my $method = 'get_' . $name;
195 :     if ($name eq 'max_size') {
196 :     my $value = $self->$method();
197 :     $props{$name} = $value == 1 ? 0 : $value;
198 :     next;
199 :     }
200 :     $props{$name} = $self->$method();
201 :     }
202 :     return \%props;
203 :     }
204 :     elsif (@_ > 3) {
205 :     Carp::croak('property() can take only the option within 2 arguments.');
206 :     }
207 :     elsif (@_ == 2) {
208 :     if ( my $method = $self->can('get_' . $name) ) {
209 :     if ($name eq 'max_size') {
210 :     my $value = $self->$method();
211 :     return $value == 1 ? 0 : $value;
212 :     }
213 :     $self->$method();
214 :     }
215 :     }
216 :     else {
217 :     $self->$name($value);
218 :     }
219 :    
220 :     }
221 :    
222 :    
223 :    
224 :     # INTERNAL
225 :    
226 :     sub _load_xs {
227 :     my $opt = shift;
228 :    
229 :     $JSON::DEBUG and Carp::carp "Load $Module_XS.";
230 :    
231 :     # if called after install module, overload is disable.... why?
232 :     JSON::Boolean::_overrride_overload($Module_XS);
233 :     JSON::Boolean::_overrride_overload($Module_PP);
234 :    
235 :     eval qq|
236 :     use $Module_XS $XS_Version ();
237 :     |;
238 :    
239 :     if ($@) {
240 :     if (defined $opt and $opt & $_INSTALL_DONT_DIE) {
241 :     $JSON::DEBUG and Carp::carp "Can't load $Module_XS...($@)";
242 :     return 0;
243 :     }
244 :     Carp::croak $@;
245 :     }
246 :    
247 :     unless (defined $opt and $opt & $_INSTALL_ONLY) {
248 :     _set_module( $JSON::Backend = $Module_XS );
249 :     my $data = join("", <DATA>); # this code is from Jcode 2.xx.
250 :     close(DATA);
251 :     eval $data;
252 :     JSON::Backend::XS->init;
253 :     }
254 :    
255 :     return 1;
256 :     };
257 :    
258 :    
259 :     sub _load_pp {
260 :     my $opt = shift;
261 :    
262 :     $JSON::DEBUG and Carp::carp "Load $Module_PP.";
263 :    
264 :     # if called after install module, overload is disable.... why?
265 :     JSON::Boolean::_overrride_overload($Module_XS);
266 :     JSON::Boolean::_overrride_overload($Module_PP);
267 :    
268 :     eval qq| require $Module_PP |;
269 :     if ($@) {
270 :     Carp::croak $@;
271 :     }
272 :    
273 :     unless (defined $opt and $opt & $_INSTALL_ONLY) {
274 :     _set_module( $JSON::Backend = $Module_PP );
275 :     JSON::Backend::PP->init;
276 :     }
277 :     };
278 :    
279 :    
280 :     sub _set_module {
281 :     my $module = shift;
282 :    
283 :     local $^W;
284 :     no strict qw(refs);
285 :    
286 :     $JSON::true = ${"$module\::true"};
287 :     $JSON::false = ${"$module\::false"};
288 :    
289 :     push @JSON::ISA, $module;
290 :     push @{"$module\::Boolean::ISA"}, qw(JSON::Boolean);
291 :    
292 :     *{"JSON::is_bool"} = \&{"$module\::is_bool"};
293 :    
294 :     for my $method ($module eq $Module_XS ? @PPOnlyMethods : @XSOnlyMethods) {
295 :     *{"JSON::$method"} = sub {
296 :     Carp::carp("$method is not supported in $module.");
297 :     $_[0];
298 :     };
299 :     }
300 :    
301 :     return 1;
302 :     }
303 :    
304 :    
305 :    
306 :     #
307 :     # JSON Boolean
308 :     #
309 :    
310 :     package JSON::Boolean;
311 :    
312 :     my %Installed;
313 :    
314 :     sub _overrride_overload {
315 :     return if ($Installed{ $_[0] }++);
316 :    
317 :     my $boolean = $_[0] . '::Boolean';
318 :    
319 :     eval sprintf(q|
320 :     package %s;
321 :     use overload (
322 :     '""' => sub { ${$_[0]} == 1 ? 'true' : 'false' },
323 :     'eq' => sub {
324 :     my ($obj, $op) = ref ($_[0]) ? ($_[0], $_[1]) : ($_[1], $_[0]);
325 :     if ($op eq 'true' or $op eq 'false') {
326 :     return "$obj" eq 'true' ? 'true' eq $op : 'false' eq $op;
327 :     }
328 :     else {
329 :     return $obj ? 1 == $op : 0 == $op;
330 :     }
331 :     },
332 :     );
333 :     |, $boolean);
334 :    
335 :     if ($@) { Carp::croak $@; }
336 :    
337 :     return 1;
338 :     }
339 :    
340 :    
341 :     #
342 :     # Helper classes for Backend Module (PP)
343 :     #
344 :    
345 :     package JSON::Backend::PP;
346 :    
347 :     sub init {
348 :     local $^W;
349 :     no strict qw(refs);
350 :     *{"JSON::decode_json"} = \&{"JSON::PP::decode_json"};
351 :     *{"JSON::encode_json"} = \&{"JSON::PP::encode_json"};
352 :     *{"JSON::PP::is_xs"} = sub { 0 };
353 :     *{"JSON::PP::is_pp"} = sub { 1 };
354 :     return 1;
355 :     }
356 :    
357 :     #
358 :     # To save memory, the below lines are read only when XS backend is used.
359 :     #
360 :    
361 :     package JSON;
362 :    
363 :     1;
364 :     __DATA__
365 :    
366 :    
367 :     #
368 :     # Helper classes for Backend Module (XS)
369 :     #
370 :    
371 :     package JSON::Backend::XS;
372 :    
373 :     use constant INDENT_LENGTH_FLAG => 15 << 12;
374 :    
375 :     use constant UNSUPPORTED_ENCODE_FLAG => {
376 :     ESCAPE_SLASH => 0x00000010,
377 :     ALLOW_BIGNUM => 0x00000020,
378 :     AS_NONBLESSED => 0x00000040,
379 :     EXPANDED => 0x10000000, # for developer's
380 :     };
381 :    
382 :     use constant UNSUPPORTED_DECODE_FLAG => {
383 :     LOOSE => 0x00000001,
384 :     ALLOW_BIGNUM => 0x00000002,
385 :     ALLOW_BAREKEY => 0x00000004,
386 :     ALLOW_SINGLEQUOTE => 0x00000008,
387 :     EXPANDED => 0x20000000, # for developer's
388 :     };
389 :    
390 :    
391 :     sub init {
392 :     local $^W;
393 :     no strict qw(refs);
394 :     *{"JSON::decode_json"} = \&{"JSON::XS::decode_json"};
395 :     *{"JSON::encode_json"} = \&{"JSON::XS::encode_json"};
396 :     *{"JSON::XS::is_xs"} = sub { 1 };
397 :     *{"JSON::XS::is_pp"} = sub { 0 };
398 :     return 1;
399 :     }
400 :    
401 :    
402 :     sub support_by_pp {
403 :     my ($class, @methods) = @_;
404 :    
405 :     local $^W;
406 :     no strict qw(refs);
407 :    
408 :     push @JSON::Backend::XS::Supportable::ISA, 'JSON';
409 :    
410 :     my $pkg = 'JSON::Backend::XS::Supportable';
411 :    
412 :     *{JSON::new} = sub {
413 :     my $proto = new JSON::XS; $$proto = 0;
414 :     bless $proto, $pkg;
415 :     };
416 :    
417 :    
418 :     for my $method (@methods) {
419 :     my $flag = uc($method);
420 :     my $type |= (UNSUPPORTED_ENCODE_FLAG->{$flag} || 0);
421 :     $type |= (UNSUPPORTED_DECODE_FLAG->{$flag} || 0);
422 :    
423 :     next unless($type);
424 :    
425 :     $pkg->_make_unsupported_method($method => $type);
426 :     }
427 :    
428 :     push @{"JSON::XS::Boolean::ISA"}, qw(JSON::PP::Boolean);
429 :     push @{"JSON::PP::Boolean::ISA"}, qw(JSON::Boolean);
430 :    
431 :     $JSON::DEBUG and Carp::carp("set -support_by_pp mode.");
432 :    
433 :     return 1;
434 :     }
435 :    
436 :    
437 :    
438 :    
439 :     #
440 :     # Helper classes for XS
441 :     #
442 :    
443 :     package JSON::Backend::XS::Supportable;
444 :    
445 :     {
446 :     my $JSON_XS_encode_orignal = \&JSON::XS::encode;
447 :     my $JSON_XS_decode_orignal = \&JSON::XS::decode;
448 :     my $JSON_XS_incr_parse_orignal = \&JSON::XS::incr_parse;
449 :    
450 :     local $^W;
451 :     *JSON::XS::decode = \&JSON::Backend::XS::Supportable::_decode;
452 :     *JSON::XS::encode = \&JSON::Backend::XS::Supportable::_encode;
453 :     *JSON::XS::incr_parse = \&JSON::Backend::XS::Supportable::_incr_parse;
454 :    
455 :     *{JSON::XS::_original_decode} = $JSON_XS_decode_orignal;
456 :     *{JSON::XS::_original_encode} = $JSON_XS_encode_orignal;
457 :     *{JSON::XS::_original_incr_parse} = $JSON_XS_incr_parse_orignal;
458 :     }
459 :    
460 :     $Carp::Internal{'JSON::Backend::XS::Supportable'} = 1;
461 :    
462 :     sub _make_unsupported_method {
463 :     my ($pkg, $method, $type) = @_;
464 :    
465 :     local $^W;
466 :     no strict qw(refs);
467 :    
468 :     *{"$pkg\::$method"} = sub {
469 :     local $^W;
470 :     if (defined $_[1] ? $_[1] : 1) {
471 :     ${$_[0]} |= $type;
472 :     }
473 :     else {
474 :     ${$_[0]} &= ~$type;
475 :     }
476 :     $_[0];
477 :     };
478 :    
479 :     *{"$pkg\::get_$method"} = sub {
480 :     ${$_[0]} & $type ? 1 : '';
481 :     };
482 :    
483 :     }
484 :    
485 :    
486 :     sub _set_for_pp {
487 :     require JSON::PP;
488 :     my $type = shift;
489 :     my $pp = new JSON::PP;
490 :     my $prop = $_[0]->property;
491 :    
492 :     for my $name (keys %$prop) {
493 :     $pp->$name( $prop->{$name} ? $prop->{$name} : 0 );
494 :     }
495 :    
496 :     my $unsupported = $type eq 'encode' ? JSON::Backend::XS::UNSUPPORTED_ENCODE_FLAG
497 :     : JSON::Backend::XS::UNSUPPORTED_DECODE_FLAG;
498 :     my $flags = ${$_[0]} || 0;
499 :    
500 :     for my $name (keys %$unsupported) {
501 :     next if ($name eq 'EXPANDED'); # for developer's
502 :     my $enable = ($flags & $unsupported->{$name}) ? 1 : 0;
503 :     my $method = lc $name;
504 :     $pp->$method($enable);
505 :     }
506 :    
507 :     $pp->indent_length( $_[0]->get_indent_length );
508 :    
509 :     return $pp;
510 :     }
511 :    
512 :     sub _encode { # using with PP encod
513 :     if (${$_[0]}) {
514 :     _set_for_pp('encode' => @_)->encode($_[1]);
515 :     }
516 :     else {
517 :     $_[0]->_original_encode( $_[1] );
518 :     }
519 :     }
520 :    
521 :    
522 :     sub _decode { # if unsupported-flag is set, use PP
523 :     if (${$_[0]}) {
524 :     _set_for_pp('decode' => @_)->decode($_[1]);
525 :     }
526 :     else {
527 :     $_[0]->_original_decode( $_[1] );
528 :     }
529 :     }
530 :    
531 :    
532 :     sub decode_prefix { # if unsupported-flag is set, use PP
533 :     _set_for_pp('decode' => @_)->decode_prefix($_[1]);
534 :     }
535 :    
536 :    
537 :     sub _incr_parse {
538 :     if (${$_[0]}) {
539 :     _set_for_pp('decode' => @_)->incr_parse($_[1]);
540 :     }
541 :     else {
542 :     $_[0]->_original_incr_parse( $_[1] );
543 :     }
544 :     }
545 :    
546 :    
547 :     sub get_indent_length {
548 :     ${$_[0]} << 4 >> 16;
549 :     }
550 :    
551 :    
552 :     sub indent_length {
553 :     my $length = $_[1];
554 :    
555 :     if (!defined $length or $length > 15 or $length < 0) {
556 :     Carp::carp "The acceptable range of indent_length() is 0 to 15.";
557 :     }
558 :     else {
559 :     local $^W;
560 :     $length <<= 12;
561 :     ${$_[0]} &= ~ JSON::Backend::XS::INDENT_LENGTH_FLAG;
562 :     ${$_[0]} |= $length;
563 :     *JSON::XS::encode = \&JSON::Backend::XS::Supportable::_encode;
564 :     }
565 :    
566 :     $_[0];
567 :     }
568 :    
569 :    
570 :     1;
571 :     __END__
572 :    
573 :     =head1 NAME
574 :    
575 :     JSON - JSON (JavaScript Object Notation) encoder/decoder
576 :    
577 :     =head1 SYNOPSIS
578 :    
579 :     use JSON; # imports encode_json, decode_json, to_json and from_json.
580 :    
581 :     # simple and fast interfaces (expect/generate UTF-8)
582 :    
583 :     $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
584 :     $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
585 :    
586 :     # OO-interface
587 :    
588 :     $json = JSON->new->allow_nonref;
589 :    
590 :     $json_text = $json->encode( $perl_scalar );
591 :     $perl_scalar = $json->decode( $json_text );
592 :    
593 :     $pretty_printed = $json->pretty->encode( $perl_scalar ); # pretty-printing
594 :    
595 :     # If you want to use PP only support features, call with '-support_by_pp'
596 :     # When XS unsupported feature is enable, using PP (de|en)code instead of XS ones.
597 :    
598 :     use JSON -support_by_pp;
599 :    
600 :     # option-acceptable interfaces (expect/generate UNICODE by default)
601 :    
602 :     $json_text = to_json( $perl_scalar, { ascii => 1, pretty => 1 } );
603 :     $perl_scalar = from_json( $json_text, { utf8 => 1 } );
604 :    
605 :     # Between (en|de)code_json and (to|from)_json, if you want to write
606 :     # a code which communicates to an outer world (encoded in UTF-8),
607 :     # recommend to use (en|de)code_json.
608 :    
609 :     =head1 VERSION
610 :    
611 :     2.21
612 :    
613 :     This version is compatible with JSON::XS B<2.27> and later.
614 :    
615 :    
616 :     =head1 DESCRIPTION
617 :    
618 :     ************************** CAUTION ********************************
619 :     * This is 'JSON module version 2' and there are many differences *
620 :     * to version 1.xx *
621 :     * Please check your applications useing old version. *
622 :     * See to 'INCOMPATIBLE CHANGES TO OLD VERSION' *
623 :     *******************************************************************
624 :    
625 :     JSON (JavaScript Object Notation) is a simple data format.
626 :     See to L<http://www.json.org/> and C<RFC4627>(L<http://www.ietf.org/rfc/rfc4627.txt>).
627 :    
628 :     This module converts Perl data structures to JSON and vice versa using either
629 :     L<JSON::XS> or L<JSON::PP>.
630 :    
631 :     JSON::XS is the fastest and most proper JSON module on CPAN which must be
632 :     compiled and installed in your environment.
633 :     JSON::PP is a pure-Perl module which is bundled in this distribution and
634 :     has a strong compatibility to JSON::XS.
635 :    
636 :     This module try to use JSON::XS by default and fail to it, use JSON::PP instead.
637 :     So its features completely depend on JSON::XS or JSON::PP.
638 :    
639 :     See to L<BACKEND MODULE DECISION>.
640 :    
641 :     To distinguish the module name 'JSON' and the format type JSON,
642 :     the former is quoted by CE<lt>E<gt> (its results vary with your using media),
643 :     and the latter is left just as it is.
644 :    
645 :     Module name : C<JSON>
646 :    
647 :     Format type : JSON
648 :    
649 :     =head2 FEATURES
650 :    
651 :     =over
652 :    
653 :     =item * correct unicode handling
654 :    
655 :     This module (i.e. backend modules) knows how to handle Unicode, documents
656 :     how and when it does so, and even documents what "correct" means.
657 :    
658 :     Even though there are limitations, this feature is available since Perl version 5.6.
659 :    
660 :     JSON::XS requires Perl 5.8.2 (but works correctly in 5.8.8 or later), so in older versions
661 :     C<JSON> sholud call JSON::PP as the backend which can be used since Perl 5.005.
662 :    
663 :     With Perl 5.8.x JSON::PP works, but from 5.8.0 to 5.8.2, because of a Perl side problem,
664 :     JSON::PP works slower in the versions. And in 5.005, the Unicode handling is not available.
665 :     See to L<JSON::PP/UNICODE HANDLING ON PERLS> for more information.
666 :    
667 :     See also to L<JSON::XS/A FEW NOTES ON UNICODE AND PERL>
668 :     and L<JSON::XS/ENCODING/CODESET_FLAG_NOTES>.
669 :    
670 :    
671 :     =item * round-trip integrity
672 :    
673 :     When you serialise a perl data structure using only data types supported
674 :     by JSON and Perl, the deserialised data structure is identical on the Perl
675 :     level. (e.g. the string "2.0" doesn't suddenly become "2" just because
676 :     it looks like a number). There I<are> minor exceptions to this, read the
677 :     L</MAPPING> section below to learn about those.
678 :    
679 :    
680 :     =item * strict checking of JSON correctness
681 :    
682 :     There is no guessing, no generating of illegal JSON texts by default,
683 :     and only JSON is accepted as input by default (the latter is a security
684 :     feature).
685 :    
686 :     See to L<JSON::XS/FEATURES> and L<JSON::PP/FEATURES>.
687 :    
688 :     =item * fast
689 :    
690 :     This module returns a JSON::XS object itself if available.
691 :     Compared to other JSON modules and other serialisers such as Storable,
692 :     JSON::XS usually compares favourably in terms of speed, too.
693 :    
694 :     If not available, C<JSON> returns a JSON::PP object instead of JSON::XS and
695 :     it is very slow as pure-Perl.
696 :    
697 :     =item * simple to use
698 :    
699 :     This module has both a simple functional interface as well as an
700 :     object oriented interface interface.
701 :    
702 :     =item * reasonably versatile output formats
703 :    
704 :     You can choose between the most compact guaranteed-single-line format possible
705 :     (nice for simple line-based protocols), a pure-ASCII format (for when your transport
706 :     is not 8-bit clean, still supports the whole Unicode range), or a pretty-printed
707 :     format (for when you want to read that stuff). Or you can combine those features
708 :     in whatever way you like.
709 :    
710 :     =back
711 :    
712 :     =head1 FUNCTIONAL INTERFACE
713 :    
714 :     Some documents are copied and modified from L<JSON::XS/FUNCTIONAL INTERFACE>.
715 :     C<to_json> and C<from_json> are additional functions.
716 :    
717 :     =head2 encode_json
718 :    
719 :     $json_text = encode_json $perl_scalar
720 :    
721 :     Converts the given Perl data structure to a UTF-8 encoded, binary string.
722 :    
723 :     This function call is functionally identical to:
724 :    
725 :     $json_text = JSON->new->utf8->encode($perl_scalar)
726 :    
727 :     =head2 decode_json
728 :    
729 :     $perl_scalar = decode_json $json_text
730 :    
731 :     The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
732 :     to parse that as an UTF-8 encoded JSON text, returning the resulting
733 :     reference.
734 :    
735 :     This function call is functionally identical to:
736 :    
737 :     $perl_scalar = JSON->new->utf8->decode($json_text)
738 :    
739 :    
740 :     =head2 to_json
741 :    
742 :     $json_text = to_json($perl_scalar)
743 :    
744 :     Converts the given Perl data structure to a json string.
745 :    
746 :     This function call is functionally identical to:
747 :    
748 :     $json_text = JSON->new->encode($perl_scalar)
749 :    
750 :     Takes a hash reference as the second.
751 :    
752 :     $json_text = to_json($perl_scalar, $flag_hashref)
753 :    
754 :     So,
755 :    
756 :     $json_text = encode_json($perl_scalar, {utf8 => 1, pretty => 1})
757 :    
758 :     equivalent to:
759 :    
760 :     $json_text = JSON->new->utf8(1)->pretty(1)->encode($perl_scalar)
761 :    
762 :     If you want to write a modern perl code which communicates to outer world,
763 :     you should use C<encode_json> (supposed that JSON data are encoded in UTF-8).
764 :    
765 :     =head2 from_json
766 :    
767 :     $perl_scalar = from_json($json_text)
768 :    
769 :     The opposite of C<to_json>: expects a json string and tries
770 :     to parse it, returning the resulting reference.
771 :    
772 :     This function call is functionally identical to:
773 :    
774 :     $perl_scalar = JSON->decode($json_text)
775 :    
776 :     Takes a hash reference as the second.
777 :    
778 :     $perl_scalar = from_json($json_text, $flag_hashref)
779 :    
780 :     So,
781 :    
782 :     $perl_scalar = from_json($json_text, {utf8 => 1})
783 :    
784 :     equivalent to:
785 :    
786 :     $perl_scalar = JSON->new->utf8(1)->decode($json_text)
787 :    
788 :     If you want to write a modern perl code which communicates to outer world,
789 :     you should use C<decode_json> (supposed that JSON data are encoded in UTF-8).
790 :    
791 :     =head2 JSON::is_bool
792 :    
793 :     $is_boolean = JSON::is_bool($scalar)
794 :    
795 :     Returns true if the passed scalar represents either JSON::true or
796 :     JSON::false, two constants that act like C<1> and C<0> respectively
797 :     and are also used to represent JSON C<true> and C<false> in Perl strings.
798 :    
799 :     =head2 JSON::true
800 :    
801 :     Returns JSON true value which is blessed object.
802 :     It C<isa> JSON::Boolean object.
803 :    
804 :     =head2 JSON::false
805 :    
806 :     Returns JSON false value which is blessed object.
807 :     It C<isa> JSON::Boolean object.
808 :    
809 :     =head2 JSON::null
810 :    
811 :     Returns C<undef>.
812 :    
813 :     See L<MAPPING>, below, for more information on how JSON values are mapped to
814 :     Perl.
815 :    
816 :     =head1 HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER
817 :    
818 :     This section supposes that your perl vresion is 5.8 or later.
819 :    
820 :     If you know a JSON text from an outer world - a network, a file content, and so on,
821 :     is encoded in UTF-8, you should use C<decode_json> or C<JSON> module object
822 :     with C<utf8> enable. And the decoded result will contain UNICODE characters.
823 :    
824 :     # from network
825 :     my $json = JSON->new->utf8;
826 :     my $json_text = CGI->new->param( 'json_data' );
827 :     my $perl_scalar = $json->decode( $json_text );
828 :    
829 :     # from file content
830 :     local $/;
831 :     open( my $fh, '<', 'json.data' );
832 :     $json_text = <$fh>;
833 :     $perl_scalar = decode_json( $json_text );
834 :    
835 :     If an outer data is not encoded in UTF-8, firstly you should C<decode> it.
836 :    
837 :     use Encode;
838 :     local $/;
839 :     open( my $fh, '<', 'json.data' );
840 :     my $encoding = 'cp932';
841 :     my $unicode_json_text = decode( $encoding, <$fh> ); # UNICODE
842 :    
843 :     # or you can write the below code.
844 :     #
845 :     # open( my $fh, "<:encoding($encoding)", 'json.data' );
846 :     # $unicode_json_text = <$fh>;
847 :    
848 :     In this case, C<$unicode_json_text> is of course UNICODE string.
849 :     So you B<cannot> use C<decode_json> nor C<JSON> module object with C<utf8> enable.
850 :     Instead of them, you use C<JSON> module object with C<utf8> disable or C<from_json>.
851 :    
852 :     $perl_scalar = $json->utf8(0)->decode( $unicode_json_text );
853 :     # or
854 :     $perl_scalar = from_json( $unicode_json_text );
855 :    
856 :     Or C<encode 'utf8'> and C<decode_json>:
857 :    
858 :     $perl_scalar = decode_json( encode( 'utf8', $unicode_json_text ) );
859 :     # this way is not efficient.
860 :    
861 :     And now, you want to convert your C<$perl_scalar> into JSON data and
862 :     send it to an outer world - a network or a file content, and so on.
863 :    
864 :     Your data usually contains UNICODE strings and you want the converted data to be encoded
865 :     in UTF-8, you should use C<encode_json> or C<JSON> module object with C<utf8> enable.
866 :    
867 :     print encode_json( $perl_scalar ); # to a network? file? or display?
868 :     # or
869 :     print $json->utf8->encode( $perl_scalar );
870 :    
871 :     If C<$perl_scalar> does not contain UNICODE but C<$encoding>-encoded strings
872 :     for some reason, then its characters are regarded as B<latin1> for perl
873 :     (because it does not concern with your $encoding).
874 :     You B<cannot> use C<encode_json> nor C<JSON> module object with C<utf8> enable.
875 :     Instead of them, you use C<JSON> module object with C<utf8> disable or C<to_json>.
876 :     Note that the resulted text is a UNICODE string but no problem to print it.
877 :    
878 :     # $perl_scalar contains $encoding encoded string values
879 :     $unicode_json_text = $json->utf8(0)->encode( $perl_scalar );
880 :     # or
881 :     $unicode_json_text = to_json( $perl_scalar );
882 :     # $unicode_json_text consists of characters less than 0x100
883 :     print $unicode_json_text;
884 :    
885 :     Or C<decode $encoding> all string values and C<encode_json>:
886 :    
887 :     $perl_scalar->{ foo } = decode( $encoding, $perl_scalar->{ foo } );
888 :     # ... do it to each string values, then encode_json
889 :     $json_text = encode_json( $perl_scalar );
890 :    
891 :     This method is a proper way but probably not efficient.
892 :    
893 :     See to L<Encode>, L<perluniintro>.
894 :    
895 :    
896 :     =head1 COMMON OBJECT-ORIENTED INTERFACE
897 :    
898 :     =head2 new
899 :    
900 :     $json = new JSON
901 :    
902 :     Returns a new C<JSON> object inherited from either JSON::XS or JSON::PP
903 :     that can be used to de/encode JSON strings.
904 :    
905 :     All boolean flags described below are by default I<disabled>.
906 :    
907 :     The mutators for flags all return the JSON object again and thus calls can
908 :     be chained:
909 :    
910 :     my $json = JSON->new->utf8->space_after->encode({a => [1,2]})
911 :     => {"a": [1, 2]}
912 :    
913 :     =head2 ascii
914 :    
915 :     $json = $json->ascii([$enable])
916 :    
917 :     $enabled = $json->get_ascii
918 :    
919 :     If $enable is true (or missing), then the encode method will not generate characters outside
920 :     the code range 0..127. Any Unicode characters outside that range will be escaped using either
921 :     a single \uXXXX or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.
922 :    
923 :     If $enable is false, then the encode method will not escape Unicode characters unless
924 :     required by the JSON syntax or other flags. This results in a faster and more compact format.
925 :    
926 :     This feature depends on the used Perl version and environment.
927 :    
928 :     See to L<JSON::PP/UNICODE HANDLING ON PERLS> if the backend is PP.
929 :    
930 :     JSON->new->ascii(1)->encode([chr 0x10401])
931 :     => ["\ud801\udc01"]
932 :    
933 :     =head2 latin1
934 :    
935 :     $json = $json->latin1([$enable])
936 :    
937 :     $enabled = $json->get_latin1
938 :    
939 :     If $enable is true (or missing), then the encode method will encode the resulting JSON
940 :     text as latin1 (or iso-8859-1), escaping any characters outside the code range 0..255.
941 :    
942 :     If $enable is false, then the encode method will not escape Unicode characters
943 :     unless required by the JSON syntax or other flags.
944 :    
945 :     JSON->new->latin1->encode (["\x{89}\x{abc}"]
946 :     => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
947 :    
948 :     =head2 utf8
949 :    
950 :     $json = $json->utf8([$enable])
951 :    
952 :     $enabled = $json->get_utf8
953 :    
954 :     If $enable is true (or missing), then the encode method will encode the JSON result
955 :     into UTF-8, as required by many protocols, while the decode method expects to be handled
956 :     an UTF-8-encoded string. Please note that UTF-8-encoded strings do not contain any
957 :     characters outside the range 0..255, they are thus useful for bytewise/binary I/O.
958 :    
959 :     In future versions, enabling this option might enable autodetection of the UTF-16 and UTF-32
960 :     encoding families, as described in RFC4627.
961 :    
962 :     If $enable is false, then the encode method will return the JSON string as a (non-encoded)
963 :     Unicode string, while decode expects thus a Unicode string. Any decoding or encoding
964 :     (e.g. to UTF-8 or UTF-16) needs to be done yourself, e.g. using the Encode module.
965 :    
966 :    
967 :     Example, output UTF-16BE-encoded JSON:
968 :    
969 :     use Encode;
970 :     $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
971 :    
972 :     Example, decode UTF-32LE-encoded JSON:
973 :    
974 :     use Encode;
975 :     $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
976 :    
977 :     See to L<JSON::PP/UNICODE HANDLING ON PERLS> if the backend is PP.
978 :    
979 :    
980 :     =head2 pretty
981 :    
982 :     $json = $json->pretty([$enable])
983 :    
984 :     This enables (or disables) all of the C<indent>, C<space_before> and
985 :     C<space_after> (and in the future possibly more) flags in one call to
986 :     generate the most readable (or most compact) form possible.
987 :    
988 :     Equivalent to:
989 :    
990 :     $json->indent->space_before->space_after
991 :    
992 :     The indent space length is three and JSON::XS cannot change the indent
993 :     space length.
994 :    
995 :     =head2 indent
996 :    
997 :     $json = $json->indent([$enable])
998 :    
999 :     $enabled = $json->get_indent
1000 :    
1001 :     If C<$enable> is true (or missing), then the C<encode> method will use a multiline
1002 :     format as output, putting every array member or object/hash key-value pair
1003 :     into its own line, identing them properly.
1004 :    
1005 :     If C<$enable> is false, no newlines or indenting will be produced, and the
1006 :     resulting JSON text is guarenteed not to contain any C<newlines>.
1007 :    
1008 :     This setting has no effect when decoding JSON texts.
1009 :    
1010 :     The indent space length is three.
1011 :     With JSON::PP, you can also access C<indent_length> to change indent space length.
1012 :    
1013 :    
1014 :     =head2 space_before
1015 :    
1016 :     $json = $json->space_before([$enable])
1017 :    
1018 :     $enabled = $json->get_space_before
1019 :    
1020 :     If C<$enable> is true (or missing), then the C<encode> method will add an extra
1021 :     optional space before the C<:> separating keys from values in JSON objects.
1022 :    
1023 :     If C<$enable> is false, then the C<encode> method will not add any extra
1024 :     space at those places.
1025 :    
1026 :     This setting has no effect when decoding JSON texts.
1027 :    
1028 :     Example, space_before enabled, space_after and indent disabled:
1029 :    
1030 :     {"key" :"value"}
1031 :    
1032 :    
1033 :     =head2 space_after
1034 :    
1035 :     $json = $json->space_after([$enable])
1036 :    
1037 :     $enabled = $json->get_space_after
1038 :    
1039 :     If C<$enable> is true (or missing), then the C<encode> method will add an extra
1040 :     optional space after the C<:> separating keys from values in JSON objects
1041 :     and extra whitespace after the C<,> separating key-value pairs and array
1042 :     members.
1043 :    
1044 :     If C<$enable> is false, then the C<encode> method will not add any extra
1045 :     space at those places.
1046 :    
1047 :     This setting has no effect when decoding JSON texts.
1048 :    
1049 :     Example, space_before and indent disabled, space_after enabled:
1050 :    
1051 :     {"key": "value"}
1052 :    
1053 :    
1054 :     =head2 relaxed
1055 :    
1056 :     $json = $json->relaxed([$enable])
1057 :    
1058 :     $enabled = $json->get_relaxed
1059 :    
1060 :     If C<$enable> is true (or missing), then C<decode> will accept some
1061 :     extensions to normal JSON syntax (see below). C<encode> will not be
1062 :     affected in anyway. I<Be aware that this option makes you accept invalid
1063 :     JSON texts as if they were valid!>. I suggest only to use this option to
1064 :     parse application-specific files written by humans (configuration files,
1065 :     resource files etc.)
1066 :    
1067 :     If C<$enable> is false (the default), then C<decode> will only accept
1068 :     valid JSON texts.
1069 :    
1070 :     Currently accepted extensions are:
1071 :    
1072 :     =over 4
1073 :    
1074 :     =item * list items can have an end-comma
1075 :    
1076 :     JSON I<separates> array elements and key-value pairs with commas. This
1077 :     can be annoying if you write JSON texts manually and want to be able to
1078 :     quickly append elements, so this extension accepts comma at the end of
1079 :     such items not just between them:
1080 :    
1081 :     [
1082 :     1,
1083 :     2, <- this comma not normally allowed
1084 :     ]
1085 :     {
1086 :     "k1": "v1",
1087 :     "k2": "v2", <- this comma not normally allowed
1088 :     }
1089 :    
1090 :     =item * shell-style '#'-comments
1091 :    
1092 :     Whenever JSON allows whitespace, shell-style comments are additionally
1093 :     allowed. They are terminated by the first carriage-return or line-feed
1094 :     character, after which more white-space and comments are allowed.
1095 :    
1096 :     [
1097 :     1, # this comment not allowed in JSON
1098 :     # neither this one...
1099 :     ]
1100 :    
1101 :     =back
1102 :    
1103 :    
1104 :     =head2 canonical
1105 :    
1106 :     $json = $json->canonical([$enable])
1107 :    
1108 :     $enabled = $json->get_canonical
1109 :    
1110 :     If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
1111 :     by sorting their keys. This is adding a comparatively high overhead.
1112 :    
1113 :     If C<$enable> is false, then the C<encode> method will output key-value
1114 :     pairs in the order Perl stores them (which will likely change between runs
1115 :     of the same script).
1116 :    
1117 :     This option is useful if you want the same data structure to be encoded as
1118 :     the same JSON text (given the same overall settings). If it is disabled,
1119 :     the same hash might be encoded differently even if contains the same data,
1120 :     as key-value pairs have no inherent ordering in Perl.
1121 :    
1122 :     This setting has no effect when decoding JSON texts.
1123 :    
1124 :     =head2 allow_nonref
1125 :    
1126 :     $json = $json->allow_nonref([$enable])
1127 :    
1128 :     $enabled = $json->get_allow_nonref
1129 :    
1130 :     If C<$enable> is true (or missing), then the C<encode> method can convert a
1131 :     non-reference into its corresponding string, number or null JSON value,
1132 :     which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
1133 :     values instead of croaking.
1134 :    
1135 :     If C<$enable> is false, then the C<encode> method will croak if it isn't
1136 :     passed an arrayref or hashref, as JSON texts must either be an object
1137 :     or array. Likewise, C<decode> will croak if given something that is not a
1138 :     JSON object or array.
1139 :    
1140 :     JSON->new->allow_nonref->encode ("Hello, World!")
1141 :     => "Hello, World!"
1142 :    
1143 :     =head2 allow_unknown
1144 :    
1145 :     $json = $json->allow_unknown ([$enable])
1146 :    
1147 :     $enabled = $json->get_allow_unknown
1148 :    
1149 :     If $enable is true (or missing), then "encode" will *not* throw an
1150 :     exception when it encounters values it cannot represent in JSON (for
1151 :     example, filehandles) but instead will encode a JSON "null" value.
1152 :     Note that blessed objects are not included here and are handled
1153 :     separately by c<allow_nonref>.
1154 :    
1155 :     If $enable is false (the default), then "encode" will throw an
1156 :     exception when it encounters anything it cannot encode as JSON.
1157 :    
1158 :     This option does not affect "decode" in any way, and it is
1159 :     recommended to leave it off unless you know your communications
1160 :     partner.
1161 :    
1162 :     =head2 allow_blessed
1163 :    
1164 :     $json = $json->allow_blessed([$enable])
1165 :    
1166 :     $enabled = $json->get_allow_blessed
1167 :    
1168 :     If C<$enable> is true (or missing), then the C<encode> method will not
1169 :     barf when it encounters a blessed reference. Instead, the value of the
1170 :     B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
1171 :     disabled or no C<TO_JSON> method found) or a representation of the
1172 :     object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
1173 :     encoded. Has no effect on C<decode>.
1174 :    
1175 :     If C<$enable> is false (the default), then C<encode> will throw an
1176 :     exception when it encounters a blessed object.
1177 :    
1178 :    
1179 :     =head2 convert_blessed
1180 :    
1181 :     $json = $json->convert_blessed([$enable])
1182 :    
1183 :     $enabled = $json->get_convert_blessed
1184 :    
1185 :     If C<$enable> is true (or missing), then C<encode>, upon encountering a
1186 :     blessed object, will check for the availability of the C<TO_JSON> method
1187 :     on the object's class. If found, it will be called in scalar context
1188 :     and the resulting scalar will be encoded instead of the object. If no
1189 :     C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
1190 :     to do.
1191 :    
1192 :     The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
1193 :     returns other blessed objects, those will be handled in the same
1194 :     way. C<TO_JSON> must take care of not causing an endless recursion cycle
1195 :     (== crash) in this case. The name of C<TO_JSON> was chosen because other
1196 :     methods called by the Perl core (== not by the user of the object) are
1197 :     usually in upper case letters and to avoid collisions with the C<to_json>
1198 :     function or method.
1199 :    
1200 :     This setting does not yet influence C<decode> in any way.
1201 :    
1202 :     If C<$enable> is false, then the C<allow_blessed> setting will decide what
1203 :     to do when a blessed object is found.
1204 :    
1205 :     =over
1206 :    
1207 :     =item convert_blessed_universally mode
1208 :    
1209 :     If use C<JSON> with C<-convert_blessed_universally>, the C<UNIVERSAL::TO_JSON>
1210 :     subroutine is defined as the below code:
1211 :    
1212 :     *UNIVERSAL::TO_JSON = sub {
1213 :     my $b_obj = B::svref_2object( $_[0] );
1214 :     return $b_obj->isa('B::HV') ? { %{ $_[0] } }
1215 :     : $b_obj->isa('B::AV') ? [ @{ $_[0] } ]
1216 :     : undef
1217 :     ;
1218 :     }
1219 :    
1220 :     This will cause that C<encode> method converts simple blessed objects into
1221 :     JSON objects as non-blessed object.
1222 :    
1223 :     JSON -convert_blessed_universally;
1224 :     $json->allow_blessed->convert_blessed->encode( $blessed_object )
1225 :    
1226 :     This feature is experimental and may be removed in the future.
1227 :    
1228 :     =back
1229 :    
1230 :     =head2 filter_json_object
1231 :    
1232 :     $json = $json->filter_json_object([$coderef])
1233 :    
1234 :     When C<$coderef> is specified, it will be called from C<decode> each
1235 :     time it decodes a JSON object. The only argument passed to the coderef
1236 :     is a reference to the newly-created hash. If the code references returns
1237 :     a single scalar (which need not be a reference), this value
1238 :     (i.e. a copy of that scalar to avoid aliasing) is inserted into the
1239 :     deserialised data structure. If it returns an empty list
1240 :     (NOTE: I<not> C<undef>, which is a valid scalar), the original deserialised
1241 :     hash will be inserted. This setting can slow down decoding considerably.
1242 :    
1243 :     When C<$coderef> is omitted or undefined, any existing callback will
1244 :     be removed and C<decode> will not change the deserialised hash in any
1245 :     way.
1246 :    
1247 :     Example, convert all JSON objects into the integer 5:
1248 :    
1249 :     my $js = JSON->new->filter_json_object (sub { 5 });
1250 :     # returns [5]
1251 :     $js->decode ('[{}]'); # the given subroutine takes a hash reference.
1252 :     # throw an exception because allow_nonref is not enabled
1253 :     # so a lone 5 is not allowed.
1254 :     $js->decode ('{"a":1, "b":2}');
1255 :    
1256 :    
1257 :     =head2 filter_json_single_key_object
1258 :    
1259 :     $json = $json->filter_json_single_key_object($key [=> $coderef])
1260 :    
1261 :     Works remotely similar to C<filter_json_object>, but is only called for
1262 :     JSON objects having a single key named C<$key>.
1263 :    
1264 :     This C<$coderef> is called before the one specified via
1265 :     C<filter_json_object>, if any. It gets passed the single value in the JSON
1266 :     object. If it returns a single value, it will be inserted into the data
1267 :     structure. If it returns nothing (not even C<undef> but the empty list),
1268 :     the callback from C<filter_json_object> will be called next, as if no
1269 :     single-key callback were specified.
1270 :    
1271 :     If C<$coderef> is omitted or undefined, the corresponding callback will be
1272 :     disabled. There can only ever be one callback for a given key.
1273 :    
1274 :     As this callback gets called less often then the C<filter_json_object>
1275 :     one, decoding speed will not usually suffer as much. Therefore, single-key
1276 :     objects make excellent targets to serialise Perl objects into, especially
1277 :     as single-key JSON objects are as close to the type-tagged value concept
1278 :     as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
1279 :     support this in any way, so you need to make sure your data never looks
1280 :     like a serialised Perl hash.
1281 :    
1282 :     Typical names for the single object key are C<__class_whatever__>, or
1283 :     C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
1284 :     things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
1285 :     with real hashes.
1286 :    
1287 :     Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
1288 :     into the corresponding C<< $WIDGET{<id>} >> object:
1289 :    
1290 :     # return whatever is in $WIDGET{5}:
1291 :     JSON
1292 :     ->new
1293 :     ->filter_json_single_key_object (__widget__ => sub {
1294 :     $WIDGET{ $_[0] }
1295 :     })
1296 :     ->decode ('{"__widget__": 5')
1297 :    
1298 :     # this can be used with a TO_JSON method in some "widget" class
1299 :     # for serialisation to json:
1300 :     sub WidgetBase::TO_JSON {
1301 :     my ($self) = @_;
1302 :    
1303 :     unless ($self->{id}) {
1304 :     $self->{id} = ..get..some..id..;
1305 :     $WIDGET{$self->{id}} = $self;
1306 :     }
1307 :    
1308 :     { __widget__ => $self->{id} }
1309 :     }
1310 :    
1311 :    
1312 :     =head2 shrink
1313 :    
1314 :     $json = $json->shrink([$enable])
1315 :    
1316 :     $enabled = $json->get_shrink
1317 :    
1318 :     With JSON::XS, this flag resizes strings generated by either
1319 :     C<encode> or C<decode> to their minimum size possible. This can save
1320 :     memory when your JSON texts are either very very long or you have many
1321 :     short strings. It will also try to downgrade any strings to octet-form
1322 :     if possible: perl stores strings internally either in an encoding called
1323 :     UTF-X or in octet-form. The latter cannot store everything but uses less
1324 :     space in general (and some buggy Perl or C code might even rely on that
1325 :     internal representation being used).
1326 :    
1327 :     With JSON::PP, it is noop about resizing strings but tries
1328 :     C<utf8::downgrade> to the returned string by C<encode>. See to L<utf8>.
1329 :    
1330 :     See to L<JSON::XS/OBJECT-ORIENTED INTERFACE> and L<JSON::PP/METHODS>.
1331 :    
1332 :     =head2 max_depth
1333 :    
1334 :     $json = $json->max_depth([$maximum_nesting_depth])
1335 :    
1336 :     $max_depth = $json->get_max_depth
1337 :    
1338 :     Sets the maximum nesting level (default C<512>) accepted while encoding
1339 :     or decoding. If a higher nesting level is detected in JSON text or a Perl
1340 :     data structure, then the encoder and decoder will stop and croak at that
1341 :     point.
1342 :    
1343 :     Nesting level is defined by number of hash- or arrayrefs that the encoder
1344 :     needs to traverse to reach a given point or the number of C<{> or C<[>
1345 :     characters without their matching closing parenthesis crossed to reach a
1346 :     given character in a string.
1347 :    
1348 :     If no argument is given, the highest possible setting will be used, which
1349 :     is rarely useful.
1350 :    
1351 :     Note that nesting is implemented by recursion in C. The default value has
1352 :     been chosen to be as large as typical operating systems allow without
1353 :     crashing. (JSON::XS)
1354 :    
1355 :     With JSON::PP as the backend, when a large value (100 or more) was set and
1356 :     it de/encodes a deep nested object/text, it may raise a warning
1357 :     'Deep recursion on subroutin' at the perl runtime phase.
1358 :    
1359 :     See L<JSON::XS/SECURITY CONSIDERATIONS> for more info on why this is useful.
1360 :    
1361 :     =head2 max_size
1362 :    
1363 :     $json = $json->max_size([$maximum_string_size])
1364 :    
1365 :     $max_size = $json->get_max_size
1366 :    
1367 :     Set the maximum length a JSON text may have (in bytes) where decoding is
1368 :     being attempted. The default is C<0>, meaning no limit. When C<decode>
1369 :     is called on a string that is longer then this many bytes, it will not
1370 :     attempt to decode the string but throw an exception. This setting has no
1371 :     effect on C<encode> (yet).
1372 :    
1373 :     If no argument is given, the limit check will be deactivated (same as when
1374 :     C<0> is specified).
1375 :    
1376 :     See L<JSON::XS/SECURITY CONSIDERATIONS>, below, for more info on why this is useful.
1377 :    
1378 :     =head2 encode
1379 :    
1380 :     $json_text = $json->encode($perl_scalar)
1381 :    
1382 :     Converts the given Perl data structure (a simple scalar or a reference
1383 :     to a hash or array) to its JSON representation. Simple scalars will be
1384 :     converted into JSON string or number sequences, while references to arrays
1385 :     become JSON arrays and references to hashes become JSON objects. Undefined
1386 :     Perl values (e.g. C<undef>) become JSON C<null> values.
1387 :     References to the integers C<0> and C<1> are converted into C<true> and C<false>.
1388 :    
1389 :     =head2 decode
1390 :    
1391 :     $perl_scalar = $json->decode($json_text)
1392 :    
1393 :     The opposite of C<encode>: expects a JSON text and tries to parse it,
1394 :     returning the resulting simple scalar or reference. Croaks on error.
1395 :    
1396 :     JSON numbers and strings become simple Perl scalars. JSON arrays become
1397 :     Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
1398 :     C<1> (C<JSON::true>), C<false> becomes C<0> (C<JSON::false>) and
1399 :     C<null> becomes C<undef>.
1400 :    
1401 :     =head2 decode_prefix
1402 :    
1403 :     ($perl_scalar, $characters) = $json->decode_prefix($json_text)
1404 :    
1405 :     This works like the C<decode> method, but instead of raising an exception
1406 :     when there is trailing garbage after the first JSON object, it will
1407 :     silently stop parsing there and return the number of characters consumed
1408 :     so far.
1409 :    
1410 :     JSON->new->decode_prefix ("[1] the tail")
1411 :     => ([], 3)
1412 :    
1413 :     See to L<JSON::XS/OBJECT-ORIENTED INTERFACE>
1414 :    
1415 :     =head2 property
1416 :    
1417 :     $boolean = $json->property($property_name)
1418 :    
1419 :     Returns a boolean value about above some properties.
1420 :    
1421 :     The available properties are C<ascii>, C<latin1>, C<utf8>,
1422 :     C<indent>,C<space_before>, C<space_after>, C<relaxed>, C<canonical>,
1423 :     C<allow_nonref>, C<allow_unknown>, C<allow_blessed>, C<convert_blessed>,
1424 :     C<shrink>, C<max_depth> and C<max_size>.
1425 :    
1426 :     $boolean = $json->property('utf8');
1427 :     => 0
1428 :     $json->utf8;
1429 :     $boolean = $json->property('utf8');
1430 :     => 1
1431 :    
1432 :     Sets the property with a given boolean value.
1433 :    
1434 :     $json = $json->property($property_name => $boolean);
1435 :    
1436 :     With no argumnt, it returns all the above properties as a hash reference.
1437 :    
1438 :     $flag_hashref = $json->property();
1439 :    
1440 :     =head1 INCREMENTAL PARSING
1441 :    
1442 :     Most of this section are copied and modified from L<JSON::XS/INCREMENTAL PARSING>.
1443 :    
1444 :     In some cases, there is the need for incremental parsing of JSON texts.
1445 :     This module does allow you to parse a JSON stream incrementally.
1446 :     It does so by accumulating text until it has a full JSON object, which
1447 :     it then can decode. This process is similar to using C<decode_prefix>
1448 :     to see if a full JSON object is available, but is much more efficient
1449 :     (and can be implemented with a minimum of method calls).
1450 :    
1451 :     The backend module will only attempt to parse the JSON text once it is sure it
1452 :     has enough text to get a decisive result, using a very simple but
1453 :     truly incremental parser. This means that it sometimes won't stop as
1454 :     early as the full parser, for example, it doesn't detect parenthese
1455 :     mismatches. The only thing it guarantees is that it starts decoding as
1456 :     soon as a syntactically valid JSON text has been seen. This means you need
1457 :     to set resource limits (e.g. C<max_size>) to ensure the parser will stop
1458 :     parsing in the presence if syntax errors.
1459 :    
1460 :     The following methods implement this incremental parser.
1461 :    
1462 :     =head2 incr_parse
1463 :    
1464 :     $json->incr_parse( [$string] ) # void context
1465 :    
1466 :     $obj_or_undef = $json->incr_parse( [$string] ) # scalar context
1467 :    
1468 :     @obj_or_empty = $json->incr_parse( [$string] ) # list context
1469 :    
1470 :     This is the central parsing function. It can both append new text and
1471 :     extract objects from the stream accumulated so far (both of these
1472 :     functions are optional).
1473 :    
1474 :     If C<$string> is given, then this string is appended to the already
1475 :     existing JSON fragment stored in the C<$json> object.
1476 :    
1477 :     After that, if the function is called in void context, it will simply
1478 :     return without doing anything further. This can be used to add more text
1479 :     in as many chunks as you want.
1480 :    
1481 :     If the method is called in scalar context, then it will try to extract
1482 :     exactly I<one> JSON object. If that is successful, it will return this
1483 :     object, otherwise it will return C<undef>. If there is a parse error,
1484 :     this method will croak just as C<decode> would do (one can then use
1485 :     C<incr_skip> to skip the errornous part). This is the most common way of
1486 :     using the method.
1487 :    
1488 :     And finally, in list context, it will try to extract as many objects
1489 :     from the stream as it can find and return them, or the empty list
1490 :     otherwise. For this to work, there must be no separators between the JSON
1491 :     objects or arrays, instead they must be concatenated back-to-back. If
1492 :     an error occurs, an exception will be raised as in the scalar context
1493 :     case. Note that in this case, any previously-parsed JSON texts will be
1494 :     lost.
1495 :    
1496 :     Example: Parse some JSON arrays/objects in a given string and return them.
1497 :    
1498 :     my @objs = JSON->new->incr_parse ("[5][7][1,2]");
1499 :    
1500 :     =head2 incr_text
1501 :    
1502 :     $lvalue_string = $json->incr_text
1503 :    
1504 :     This method returns the currently stored JSON fragment as an lvalue, that
1505 :     is, you can manipulate it. This I<only> works when a preceding call to
1506 :     C<incr_parse> in I<scalar context> successfully returned an object. Under
1507 :     all other circumstances you must not call this function (I mean it.
1508 :     although in simple tests it might actually work, it I<will> fail under
1509 :     real world conditions). As a special exception, you can also call this
1510 :     method before having parsed anything.
1511 :    
1512 :     This function is useful in two cases: a) finding the trailing text after a
1513 :     JSON object or b) parsing multiple JSON objects separated by non-JSON text
1514 :     (such as commas).
1515 :    
1516 :     $json->incr_text =~ s/\s*,\s*//;
1517 :    
1518 :     In Perl 5.005, C<lvalue> attribute is not available.
1519 :     You must write codes like the below:
1520 :    
1521 :     $string = $json->incr_text;
1522 :     $string =~ s/\s*,\s*//;
1523 :     $json->incr_text( $string );
1524 :    
1525 :     =head2 incr_skip
1526 :    
1527 :     $json->incr_skip
1528 :    
1529 :     This will reset the state of the incremental parser and will remove the
1530 :     parsed text from the input buffer. This is useful after C<incr_parse>
1531 :     died, in which case the input buffer and incremental parser state is left
1532 :     unchanged, to skip the text parsed so far and to reset the parse state.
1533 :    
1534 :     =head2 incr_reset
1535 :    
1536 :     $json->incr_reset
1537 :    
1538 :     This completely resets the incremental parser, that is, after this call,
1539 :     it will be as if the parser had never parsed anything.
1540 :    
1541 :     This is useful if you want ot repeatedly parse JSON objects and want to
1542 :     ignore any trailing data, which means you have to reset the parser after
1543 :     each successful decode.
1544 :    
1545 :     See to L<JSON::XS/INCREMENTAL PARSING> for examples.
1546 :    
1547 :    
1548 :     =head1 JSON::PP SUPPORT METHODS
1549 :    
1550 :     The below methods are JSON::PP own methods, so when C<JSON> works
1551 :     with JSON::PP (i.e. the created object is a JSON::PP object), available.
1552 :     See to L<JSON::PP/JSON::PP OWN METHODS> in detail.
1553 :    
1554 :     If you use C<JSON> with additonal C<-support_by_pp>, some methods
1555 :     are available even with JSON::XS. See to L<USE PP FEATURES EVEN THOUGH XS BACKEND>.
1556 :    
1557 :     BEING { $ENV{PERL_JSON_BACKEND} = 'JSON::XS' }
1558 :    
1559 :     use JSON -support_by_pp;
1560 :    
1561 :     my $json = new JSON;
1562 :     $json->allow_nonref->escape_slash->encode("/");
1563 :    
1564 :     # functional interfaces too.
1565 :     print to_json(["/"], {escape_slash => 1});
1566 :     print from_json('["foo"]', {utf8 => 1});
1567 :    
1568 :     If you do not want to all functions but C<-support_by_pp>,
1569 :     use C<-no_export>.
1570 :    
1571 :     use JSON -support_by_pp, -no_export;
1572 :     # functional interfaces are not exported.
1573 :    
1574 :     =head2 allow_singlequote
1575 :    
1576 :     $json = $json->allow_singlequote([$enable])
1577 :    
1578 :     If C<$enable> is true (or missing), then C<decode> will accept
1579 :     any JSON strings quoted by single quotations that are invalid JSON
1580 :     format.
1581 :    
1582 :     $json->allow_singlequote->decode({"foo":'bar'});
1583 :     $json->allow_singlequote->decode({'foo':"bar"});
1584 :     $json->allow_singlequote->decode({'foo':'bar'});
1585 :    
1586 :     As same as the C<relaxed> option, this option may be used to parse
1587 :     application-specific files written by humans.
1588 :    
1589 :     =head2 allow_barekey
1590 :    
1591 :     $json = $json->allow_barekey([$enable])
1592 :    
1593 :     If C<$enable> is true (or missing), then C<decode> will accept
1594 :     bare keys of JSON object that are invalid JSON format.
1595 :    
1596 :     As same as the C<relaxed> option, this option may be used to parse
1597 :     application-specific files written by humans.
1598 :    
1599 :     $json->allow_barekey->decode('{foo:"bar"}');
1600 :    
1601 :     =head2 allow_bignum
1602 :    
1603 :     $json = $json->allow_bignum([$enable])
1604 :    
1605 :     If C<$enable> is true (or missing), then C<decode> will convert
1606 :     the big integer Perl cannot handle as integer into a L<Math::BigInt>
1607 :     object and convert a floating number (any) into a L<Math::BigFloat>.
1608 :    
1609 :     On the contary, C<encode> converts C<Math::BigInt> objects and C<Math::BigFloat>
1610 :     objects into JSON numbers with C<allow_blessed> enable.
1611 :    
1612 :     $json->allow_nonref->allow_blessed->allow_bignum;
1613 :     $bigfloat = $json->decode('2.000000000000000000000000001');
1614 :     print $json->encode($bigfloat);
1615 :     # => 2.000000000000000000000000001
1616 :    
1617 :     See to L<MAPPING> aboout the conversion of JSON number.
1618 :    
1619 :     =head2 loose
1620 :    
1621 :     $json = $json->loose([$enable])
1622 :    
1623 :     The unescaped [\x00-\x1f\x22\x2f\x5c] strings are invalid in JSON strings
1624 :     and the module doesn't allow to C<decode> to these (except for \x2f).
1625 :     If C<$enable> is true (or missing), then C<decode> will accept these
1626 :     unescaped strings.
1627 :    
1628 :     $json->loose->decode(qq|["abc
1629 :     def"]|);
1630 :    
1631 :     See to L<JSON::PP/JSON::PP OWN METHODS>.
1632 :    
1633 :     =head2 escape_slash
1634 :    
1635 :     $json = $json->escape_slash([$enable])
1636 :    
1637 :     According to JSON Grammar, I<slash> (U+002F) is escaped. But by default
1638 :     JSON backend modules encode strings without escaping slash.
1639 :    
1640 :     If C<$enable> is true (or missing), then C<encode> will escape slashes.
1641 :    
1642 :     =head2 indent_length
1643 :    
1644 :     $json = $json->indent_length($length)
1645 :    
1646 :     With JSON::XS, The indent space length is 3 and cannot be changed.
1647 :     With JSON::PP, it sets the indent space length with the given $length.
1648 :     The default is 3. The acceptable range is 0 to 15.
1649 :    
1650 :     =head2 sort_by
1651 :    
1652 :     $json = $json->sort_by($function_name)
1653 :     $json = $json->sort_by($subroutine_ref)
1654 :    
1655 :     If $function_name or $subroutine_ref are set, its sort routine are used.
1656 :    
1657 :     $js = $pc->sort_by(sub { $JSON::PP::a cmp $JSON::PP::b })->encode($obj);
1658 :     # is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);
1659 :    
1660 :     $js = $pc->sort_by('own_sort')->encode($obj);
1661 :     # is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);
1662 :    
1663 :     sub JSON::PP::own_sort { $JSON::PP::a cmp $JSON::PP::b }
1664 :    
1665 :     As the sorting routine runs in the JSON::PP scope, the given
1666 :     subroutine name and the special variables C<$a>, C<$b> will begin
1667 :     with 'JSON::PP::'.
1668 :    
1669 :     If $integer is set, then the effect is same as C<canonical> on.
1670 :    
1671 :     See to L<JSON::PP/JSON::PP OWN METHODS>.
1672 :    
1673 :     =head1 MAPPING
1674 :    
1675 :     This section is copied from JSON::XS and modified to C<JSON>.
1676 :     JSON::XS and JSON::PP mapping mechanisms are almost equivalent.
1677 :    
1678 :     See to L<JSON::XS/MAPPING>.
1679 :    
1680 :     =head2 JSON -> PERL
1681 :    
1682 :     =over 4
1683 :    
1684 :     =item object
1685 :    
1686 :     A JSON object becomes a reference to a hash in Perl. No ordering of object
1687 :     keys is preserved (JSON does not preserver object key ordering itself).
1688 :    
1689 :     =item array
1690 :    
1691 :     A JSON array becomes a reference to an array in Perl.
1692 :    
1693 :     =item string
1694 :    
1695 :     A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
1696 :     are represented by the same codepoints in the Perl string, so no manual
1697 :     decoding is necessary.
1698 :    
1699 :     =item number
1700 :    
1701 :     A JSON number becomes either an integer, numeric (floating point) or
1702 :     string scalar in perl, depending on its range and any fractional parts. On
1703 :     the Perl level, there is no difference between those as Perl handles all
1704 :     the conversion details, but an integer may take slightly less memory and
1705 :     might represent more values exactly than floating point numbers.
1706 :    
1707 :     If the number consists of digits only, C<JSON> will try to represent
1708 :     it as an integer value. If that fails, it will try to represent it as
1709 :     a numeric (floating point) value if that is possible without loss of
1710 :     precision. Otherwise it will preserve the number as a string value (in
1711 :     which case you lose roundtripping ability, as the JSON number will be
1712 :     re-encoded toa JSON string).
1713 :    
1714 :     Numbers containing a fractional or exponential part will always be
1715 :     represented as numeric (floating point) values, possibly at a loss of
1716 :     precision (in which case you might lose perfect roundtripping ability, but
1717 :     the JSON number will still be re-encoded as a JSON number).
1718 :    
1719 :     Note that precision is not accuracy - binary floating point values cannot
1720 :     represent most decimal fractions exactly, and when converting from and to
1721 :     floating point, C<JSON> only guarantees precision up to but not including
1722 :     the leats significant bit.
1723 :    
1724 :     If the backend is JSON::PP and C<allow_bignum> is enable, the big integers
1725 :     and the numeric can be optionally converted into L<Math::BigInt> and
1726 :     L<Math::BigFloat> objects.
1727 :    
1728 :     =item true, false
1729 :    
1730 :     These JSON atoms become C<JSON::true> and C<JSON::false>,
1731 :     respectively. They are overloaded to act almost exactly like the numbers
1732 :     C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
1733 :     the C<JSON::is_bool> function.
1734 :    
1735 :     If C<JSON::true> and C<JSON::false> are used as strings or compared as strings,
1736 :     they represent as C<true> and C<false> respectively.
1737 :    
1738 :     print JSON::true . "\n";
1739 :     => true
1740 :     print JSON::true + 1;
1741 :     => 1
1742 :    
1743 :     ok(JSON::true eq 'true');
1744 :     ok(JSON::true eq '1');
1745 :     ok(JSON::true == 1);
1746 :    
1747 :     C<JSON> will install these missing overloading features to the backend modules.
1748 :    
1749 :    
1750 :     =item null
1751 :    
1752 :     A JSON null atom becomes C<undef> in Perl.
1753 :    
1754 :     C<JSON::null> returns C<unddef>.
1755 :    
1756 :     =back
1757 :    
1758 :    
1759 :     =head2 PERL -> JSON
1760 :    
1761 :     The mapping from Perl to JSON is slightly more difficult, as Perl is a
1762 :     truly typeless language, so we can only guess which JSON type is meant by
1763 :     a Perl value.
1764 :    
1765 :     =over 4
1766 :    
1767 :     =item hash references
1768 :    
1769 :     Perl hash references become JSON objects. As there is no inherent ordering
1770 :     in hash keys (or JSON objects), they will usually be encoded in a
1771 :     pseudo-random order that can change between runs of the same program but
1772 :     stays generally the same within a single run of a program. C<JSON>
1773 :     optionally sort the hash keys (determined by the I<canonical> flag), so
1774 :     the same datastructure will serialise to the same JSON text (given same
1775 :     settings and version of JSON::XS), but this incurs a runtime overhead
1776 :     and is only rarely useful, e.g. when you want to compare some JSON text
1777 :     against another for equality.
1778 :    
1779 :     In future, the ordered object feature will be added to JSON::PP using C<tie> mechanism.
1780 :    
1781 :    
1782 :     =item array references
1783 :    
1784 :     Perl array references become JSON arrays.
1785 :    
1786 :     =item other references
1787 :    
1788 :     Other unblessed references are generally not allowed and will cause an
1789 :     exception to be thrown, except for references to the integers C<0> and
1790 :     C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
1791 :     also use C<JSON::false> and C<JSON::true> to improve readability.
1792 :    
1793 :     to_json [\0,JSON::true] # yields [false,true]
1794 :    
1795 :     =item JSON::true, JSON::false, JSON::null
1796 :    
1797 :     These special values become JSON true and JSON false values,
1798 :     respectively. You can also use C<\1> and C<\0> directly if you want.
1799 :    
1800 :     JSON::null returns C<undef>.
1801 :    
1802 :     =item blessed objects
1803 :    
1804 :     Blessed objects are not directly representable in JSON. See the
1805 :     C<allow_blessed> and C<convert_blessed> methods on various options on
1806 :     how to deal with this: basically, you can choose between throwing an
1807 :     exception, encoding the reference as if it weren't blessed, or provide
1808 :     your own serialiser method.
1809 :    
1810 :     With C<convert_blessed_universally> mode, C<encode> converts blessed
1811 :     hash references or blessed array references (contains other blessed references)
1812 :     into JSON members and arrays.
1813 :    
1814 :     use JSON -convert_blessed_universally;
1815 :     JSON->new->allow_blessed->convert_blessed->encode( $blessed_object );
1816 :    
1817 :     See to L<convert_blessed>.
1818 :    
1819 :     =item simple scalars
1820 :    
1821 :     Simple Perl scalars (any scalar that is not a reference) are the most
1822 :     difficult objects to encode: JSON::XS and JSON::PP will encode undefined scalars as
1823 :     JSON C<null> values, scalars that have last been used in a string context
1824 :     before encoding as JSON strings, and anything else as number value:
1825 :    
1826 :     # dump as number
1827 :     encode_json [2] # yields [2]
1828 :     encode_json [-3.0e17] # yields [-3e+17]
1829 :     my $value = 5; encode_json [$value] # yields [5]
1830 :    
1831 :     # used as string, so dump as string
1832 :     print $value;
1833 :     encode_json [$value] # yields ["5"]
1834 :    
1835 :     # undef becomes null
1836 :     encode_json [undef] # yields [null]
1837 :    
1838 :     You can force the type to be a string by stringifying it:
1839 :    
1840 :     my $x = 3.1; # some variable containing a number
1841 :     "$x"; # stringified
1842 :     $x .= ""; # another, more awkward way to stringify
1843 :     print $x; # perl does it for you, too, quite often
1844 :    
1845 :     You can force the type to be a number by numifying it:
1846 :    
1847 :     my $x = "3"; # some variable containing a string
1848 :     $x += 0; # numify it, ensuring it will be dumped as a number
1849 :     $x *= 1; # same thing, the choise is yours.
1850 :    
1851 :     You can not currently force the type in other, less obscure, ways.
1852 :    
1853 :     Note that numerical precision has the same meaning as under Perl (so
1854 :     binary to decimal conversion follows the same rules as in Perl, which
1855 :     can differ to other languages). Also, your perl interpreter might expose
1856 :     extensions to the floating point numbers of your platform, such as
1857 :     infinities or NaN's - these cannot be represented in JSON, and it is an
1858 :     error to pass those in.
1859 :    
1860 :     =item Big Number
1861 :    
1862 :     If the backend is JSON::PP and C<allow_bignum> is enable,
1863 :     C<encode> converts C<Math::BigInt> objects and C<Math::BigFloat>
1864 :     objects into JSON numbers.
1865 :    
1866 :    
1867 :     =back
1868 :    
1869 :     =head1 JSON and ECMAscript
1870 :    
1871 :     See to L<JSON::XS/JSON and ECMAscript>.
1872 :    
1873 :     =head1 JSON and YAML
1874 :    
1875 :     JSON is not a subset of YAML.
1876 :     See to L<JSON::XS/JSON and YAML>.
1877 :    
1878 :    
1879 :     =head1 BACKEND MODULE DECISION
1880 :    
1881 :     When you use C<JSON>, C<JSON> tries to C<use> JSON::XS. If this call failed, it will
1882 :     C<uses> JSON::PP. The required JSON::XS version is I<2.2> or later.
1883 :    
1884 :     The C<JSON> constructor method returns an object inherited from the backend module,
1885 :     and JSON::XS object is a blessed scaler reference while JSON::PP is a blessed hash
1886 :     reference.
1887 :    
1888 :     So, your program should not depend on the backend module, especially
1889 :     returned objects should not be modified.
1890 :    
1891 :     my $json = JSON->new; # XS or PP?
1892 :     $json->{stash} = 'this is xs object'; # this code may raise an error!
1893 :    
1894 :     To check the backend module, there are some methods - C<backend>, C<is_pp> and C<is_xs>.
1895 :    
1896 :     JSON->backend; # 'JSON::XS' or 'JSON::PP'
1897 :    
1898 :     JSON->backend->is_pp: # 0 or 1
1899 :    
1900 :     JSON->backend->is_xs: # 1 or 0
1901 :    
1902 :     $json->is_xs; # 1 or 0
1903 :    
1904 :     $json->is_pp; # 0 or 1
1905 :    
1906 :    
1907 :     If you set an enviornment variable C<PERL_JSON_BACKEND>, The calling action will be changed.
1908 :    
1909 :     =over
1910 :    
1911 :     =item PERL_JSON_BACKEND = 0 or PERL_JSON_BACKEND = 'JSON::PP'
1912 :    
1913 :     Always use JSON::PP
1914 :    
1915 :     =item PERL_JSON_BACKEND == 1 or PERL_JSON_BACKEND = 'JSON::XS,JSON::PP'
1916 :    
1917 :     (The default) Use compiled JSON::XS if it is properly compiled & installed,
1918 :     otherwise use JSON::PP.
1919 :    
1920 :     =item PERL_JSON_BACKEND == 2 or PERL_JSON_BACKEND = 'JSON::XS'
1921 :    
1922 :     Always use compiled JSON::XS, die if it isn't properly compiled & installed.
1923 :    
1924 :     =back
1925 :    
1926 :     These ideas come from L<DBI::PurePerl> mechanism.
1927 :    
1928 :     example:
1929 :    
1930 :     BEGIN { $ENV{PERL_JSON_BACKEND} = 'JSON::PP' }
1931 :     use JSON; # always uses JSON::PP
1932 :    
1933 :     In future, it may be able to specify another module.
1934 :    
1935 :     =head1 USE PP FEATURES EVEN THOUGH XS BACKEND
1936 :    
1937 :     Many methods are available with either JSON::XS or JSON::PP and
1938 :     when the backend module is JSON::XS, if any JSON::PP specific (i.e. JSON::XS unspported)
1939 :     method is called, it will C<warn> and be noop.
1940 :    
1941 :     But If you C<use> C<JSON> passing the optional string C<-support_by_pp>,
1942 :     it makes a part of those unupported methods available.
1943 :     This feature is achieved by using JSON::PP in C<de/encode>.
1944 :    
1945 :     BEGIN { $ENV{PERL_JSON_BACKEND} = 2 } # with JSON::XS
1946 :     use JSON -support_by_pp;
1947 :     my $json = new JSON;
1948 :     $json->allow_nonref->escape_slash->encode("/");
1949 :    
1950 :     At this time, the returned object is a C<JSON::Backend::XS::Supportable>
1951 :     object (re-blessed XS object), and by checking JSON::XS unsupported flags
1952 :     in de/encoding, can support some unsupported methods - C<loose>, C<allow_bignum>,
1953 :     C<allow_barekey>, C<allow_singlequote>, C<escape_slash> and C<indent_length>.
1954 :    
1955 :     When any unsupported methods are not enable, C<XS de/encode> will be
1956 :     used as is. The switch is achieved by changing the symbolic tables.
1957 :    
1958 :     C<-support_by_pp> is effective only when the backend module is JSON::XS
1959 :     and it makes the de/encoding speed down a bit.
1960 :    
1961 :     See to L<JSON::PP SUPPORT METHODS>.
1962 :    
1963 :     =head1 INCOMPATIBLE CHANGES TO OLD VERSION
1964 :    
1965 :     There are big incompatibility between new version (2.00) and old (1.xx).
1966 :     If you use old C<JSON> 1.xx in your code, please check it.
1967 :    
1968 :     See to L<Transition ways from 1.xx to 2.xx.>
1969 :    
1970 :     =over
1971 :    
1972 :     =item jsonToObj and objToJson are obsoleted.
1973 :    
1974 :     Non Perl-style name C<jsonToObj> and C<objToJson> are obsoleted
1975 :     (but not yet deleted from the source).
1976 :     If you use these functions in your code, please replace them
1977 :     with C<from_json> and C<to_json>.
1978 :    
1979 :    
1980 :     =item Global variables are no longer available.
1981 :    
1982 :     C<JSON> class variables - C<$JSON::AUTOCONVERT>, C<$JSON::BareKey>, etc...
1983 :     - are not available any longer.
1984 :     Instead, various features can be used through object methods.
1985 :    
1986 :    
1987 :     =item Package JSON::Converter and JSON::Parser are deleted.
1988 :    
1989 :     Now C<JSON> bundles with JSON::PP which can handle JSON more properly than them.
1990 :    
1991 :     =item Package JSON::NotString is deleted.
1992 :    
1993 :     There was C<JSON::NotString> class which represents JSON value C<true>, C<false>, C<null>
1994 :     and numbers. It was deleted and replaced by C<JSON::Boolean>.
1995 :    
1996 :     C<JSON::Boolean> represents C<true> and C<false>.
1997 :    
1998 :     C<JSON::Boolean> does not represent C<null>.
1999 :    
2000 :     C<JSON::null> returns C<undef>.
2001 :    
2002 :     C<JSON> makes L<JSON::XS::Boolean> and L<JSON::PP::Boolean> is-a relation
2003 :     to L<JSON::Boolean>.
2004 :    
2005 :     =item function JSON::Number is obsoleted.
2006 :    
2007 :     C<JSON::Number> is now needless because JSON::XS and JSON::PP have
2008 :     round-trip integrity.
2009 :    
2010 :     =item JSONRPC modules are deleted.
2011 :    
2012 :     Perl implementation of JSON-RPC protocol - C<JSONRPC >, C<JSONRPC::Transport::HTTP>
2013 :     and C<Apache::JSONRPC > are deleted in this distribution.
2014 :     Instead of them, there is L<JSON::RPC> which supports JSON-RPC protocol version 1.1.
2015 :    
2016 :     =back
2017 :    
2018 :     =head2 Transition ways from 1.xx to 2.xx.
2019 :    
2020 :     You should set C<suport_by_pp> mode firstly, because
2021 :     it is always successful for the below codes even with JSON::XS.
2022 :    
2023 :     use JSON -support_by_pp;
2024 :    
2025 :     =over
2026 :    
2027 :     =item Exported jsonToObj (simple)
2028 :    
2029 :     from_json($json_text);
2030 :    
2031 :     =item Exported objToJson (simple)
2032 :    
2033 :     to_json($perl_scalar);
2034 :    
2035 :     =item Exported jsonToObj (advanced)
2036 :    
2037 :     $flags = {allow_barekey => 1, allow_singlequote => 1};
2038 :     from_json($json_text, $flags);
2039 :    
2040 :     equivalent to:
2041 :    
2042 :     $JSON::BareKey = 1;
2043 :     $JSON::QuotApos = 1;
2044 :     jsonToObj($json_text);
2045 :    
2046 :     =item Exported objToJson (advanced)
2047 :    
2048 :     $flags = {allow_blessed => 1, allow_barekey => 1};
2049 :     to_json($perl_scalar, $flags);
2050 :    
2051 :     equivalent to:
2052 :    
2053 :     $JSON::BareKey = 1;
2054 :     objToJson($perl_scalar);
2055 :    
2056 :     =item jsonToObj as object method
2057 :    
2058 :     $json->decode($json_text);
2059 :    
2060 :     =item objToJson as object method
2061 :    
2062 :     $json->encode($perl_scalar);
2063 :    
2064 :     =item new method with parameters
2065 :    
2066 :     The C<new> method in 2.x takes any parameters no longer.
2067 :     You can set parameters instead;
2068 :    
2069 :     $json = JSON->new->pretty;
2070 :    
2071 :     =item $JSON::Pretty, $JSON::Indent, $JSON::Delimiter
2072 :    
2073 :     If C<indent> is enable, that menas C<$JSON::Pretty> flag set. And
2074 :     C<$JSON::Delimiter> was substituted by C<space_before> and C<space_after>.
2075 :     In conclusion:
2076 :    
2077 :     $json->indent->space_before->space_after;
2078 :    
2079 :     Equivalent to:
2080 :    
2081 :     $json->pretty;
2082 :    
2083 :     To change indent length, use C<indent_length>.
2084 :    
2085 :     (Only with JSON::PP, if C<-support_by_pp> is not used.)
2086 :    
2087 :     $json->pretty->indent_length(2)->encode($perl_scalar);
2088 :    
2089 :     =item $JSON::BareKey
2090 :    
2091 :     (Only with JSON::PP, if C<-support_by_pp> is not used.)
2092 :    
2093 :     $json->allow_barekey->decode($json_text)
2094 :    
2095 :     =item $JSON::ConvBlessed
2096 :    
2097 :     use C<-convert_blessed_universally>. See to L<convert_blessed>.
2098 :    
2099 :     =item $JSON::QuotApos
2100 :    
2101 :     (Only with JSON::PP, if C<-support_by_pp> is not used.)
2102 :    
2103 :     $json->allow_singlequote->decode($json_text)
2104 :    
2105 :     =item $JSON::SingleQuote
2106 :    
2107 :     Disable. C<JSON> does not make such a invalid JSON string any longer.
2108 :    
2109 :     =item $JSON::KeySort
2110 :    
2111 :     $json->canonical->encode($perl_scalar)
2112 :    
2113 :     This is the ascii sort.
2114 :    
2115 :     If you want to use with your own sort routine, check the C<sort_by> method.
2116 :    
2117 :     (Only with JSON::PP, even if C<-support_by_pp> is used currently.)
2118 :    
2119 :     $json->sort_by($sort_routine_ref)->encode($perl_scalar)
2120 :    
2121 :     $json->sort_by(sub { $JSON::PP::a <=> $JSON::PP::b })->encode($perl_scalar)
2122 :    
2123 :     Can't access C<$a> and C<$b> but C<$JSON::PP::a> and C<$JSON::PP::b>.
2124 :    
2125 :     =item $JSON::SkipInvalid
2126 :    
2127 :     $json->allow_unknown
2128 :    
2129 :     =item $JSON::AUTOCONVERT
2130 :    
2131 :     Needless. C<JSON> backend modules have the round-trip integrity.
2132 :    
2133 :     =item $JSON::UTF8
2134 :    
2135 :     Needless because C<JSON> (JSON::XS/JSON::PP) sets
2136 :     the UTF8 flag on properly.
2137 :    
2138 :     # With UTF8-flagged strings
2139 :    
2140 :     $json->allow_nonref;
2141 :     $str = chr(1000); # UTF8-flagged
2142 :    
2143 :     $json_text = $json->utf8(0)->encode($str);
2144 :     utf8::is_utf8($json_text);
2145 :     # true
2146 :     $json_text = $json->utf8(1)->encode($str);
2147 :     utf8::is_utf8($json_text);
2148 :     # false
2149 :    
2150 :     $str = '"' . chr(1000) . '"'; # UTF8-flagged
2151 :    
2152 :     $perl_scalar = $json->utf8(0)->decode($str);
2153 :     utf8::is_utf8($perl_scalar);
2154 :     # true
2155 :     $perl_scalar = $json->utf8(1)->decode($str);
2156 :     # died because of 'Wide character in subroutine'
2157 :    
2158 :     See to L<JSON::XS/A FEW NOTES ON UNICODE AND PERL>.
2159 :    
2160 :     =item $JSON::UnMapping
2161 :    
2162 :     Disable. See to L<MAPPING>.
2163 :    
2164 :     =item $JSON::SelfConvert
2165 :    
2166 :     This option was deleted.
2167 :     Instead of it, if a givien blessed object has the C<TO_JSON> method,
2168 :     C<TO_JSON> will be executed with C<convert_blessed>.
2169 :    
2170 :     $json->convert_blessed->encode($bleesed_hashref_or_arrayref)
2171 :     # if need, call allow_blessed
2172 :    
2173 :     Note that it was C<toJson> in old version, but now not C<toJson> but C<TO_JSON>.
2174 :    
2175 :     =back
2176 :    
2177 :     =head1 TODO
2178 :    
2179 :     =over
2180 :    
2181 :     =item example programs
2182 :    
2183 :     =back
2184 :    
2185 :     =head1 THREADS
2186 :    
2187 :     No test with JSON::PP. If with JSON::XS, See to L<JSON::XS/THREADS>.
2188 :    
2189 :    
2190 :     =head1 BUGS
2191 :    
2192 :     Please report bugs relevant to C<JSON> to E<lt>makamaka[at]cpan.orgE<gt>.
2193 :    
2194 :    
2195 :     =head1 SEE ALSO
2196 :    
2197 :     Most of the document is copied and modified from JSON::XS doc.
2198 :    
2199 :     L<JSON::XS>, L<JSON::PP>
2200 :    
2201 :     C<RFC4627>(L<http://www.ietf.org/rfc/rfc4627.txt>)
2202 :    
2203 :     =head1 AUTHOR
2204 :    
2205 :     Makamaka Hannyaharamitu, E<lt>makamaka[at]cpan.orgE<gt>
2206 :    
2207 :     JSON::XS was written by Marc Lehmann <schmorp[at]schmorp.de>
2208 :    
2209 :     The relese of this new version owes to the courtesy of Marc Lehmann.
2210 :    
2211 :    
2212 :     =head1 COPYRIGHT AND LICENSE
2213 :    
2214 :     Copyright 2005-2010 by Makamaka Hannyaharamitu
2215 :    
2216 :     This library is free software; you can redistribute it and/or modify
2217 :     it under the same terms as Perl itself.
2218 :    
2219 :     =cut
2220 :    

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