uroman/lib/JSON.pm

package JSON;


use strict;
use Carp ();
use base qw(Exporter);
@JSON::EXPORT = qw(from_json to_json jsonToObj objToJson encode_json decode_json);

BEGIN {
    $JSON::VERSION = '2.90';
    $JSON::DEBUG   = 0 unless (defined $JSON::DEBUG);
    $JSON::DEBUG   = $ENV{ PERL_JSON_DEBUG } if exists $ENV{ PERL_JSON_DEBUG };
}

my $Module_XS  = 'JSON::XS';
my $Module_PP  = 'JSON::PP';
my $Module_bp  = 'JSON::backportPP'; # included in JSON distribution
my $PP_Version = '2.27203';
my $XS_Version = '2.34';


# XS and PP common methods

my @PublicMethods = qw/
    ascii latin1 utf8 pretty indent space_before space_after relaxed canonical allow_nonref 
    allow_blessed convert_blessed filter_json_object filter_json_single_key_object 
    shrink max_depth max_size encode decode decode_prefix allow_unknown
/;

my @Properties = qw/
    ascii latin1 utf8 indent space_before space_after relaxed canonical allow_nonref
    allow_blessed convert_blessed shrink max_depth max_size allow_unknown
/;

my @XSOnlyMethods = qw/allow_tags/; # Currently nothing

my @PPOnlyMethods = qw/
    indent_length sort_by
    allow_singlequote allow_bignum loose allow_barekey escape_slash as_nonblessed
/; # JSON::PP specific


# used in _load_xs and _load_pp ($INSTALL_ONLY is not used currently)
my $_INSTALL_DONT_DIE  = 1; # When _load_xs fails to load XS, don't die.
my $_INSTALL_ONLY      = 2; # Don't call _set_methods()
my $_ALLOW_UNSUPPORTED = 0;
my $_UNIV_CONV_BLESSED = 0;
my $_USSING_bpPP       = 0;


# Check the environment variable to decide worker module. 

unless ($JSON::Backend) {
    $JSON::DEBUG and  Carp::carp("Check used worker module...");

    my $backend = exists $ENV{PERL_JSON_BACKEND} ? $ENV{PERL_JSON_BACKEND} : 1;

    if ($backend eq '1' or $backend =~ /JSON::XS\s*,\s*JSON::PP/) {
        _load_xs($_INSTALL_DONT_DIE) or _load_pp();
    }
    elsif ($backend eq '0' or $backend eq 'JSON::PP') {
        _load_pp();
    }
    elsif ($backend eq '2' or $backend eq 'JSON::XS') {
        _load_xs();
    }
    elsif ($backend eq 'JSON::backportPP') {
        $_USSING_bpPP = 1;
        _load_pp();
    }
    else {
        Carp::croak "The value of environmental variable 'PERL_JSON_BACKEND' is invalid.";
    }
}


sub import {
    my $pkg = shift;
    my @what_to_export;
    my $no_export;

    for my $tag (@_) {
        if ($tag eq '-support_by_pp') {
            if (!$_ALLOW_UNSUPPORTED++) {
                JSON::Backend::XS
                    ->support_by_pp(@PPOnlyMethods) if ($JSON::Backend eq $Module_XS);
            }
            next;
        }
        elsif ($tag eq '-no_export') {
            $no_export++, next;
        }
        elsif ( $tag eq '-convert_blessed_universally' ) {
            eval q|

                require B;

                *UNIVERSAL::TO_JSON = sub {

                    my $b_obj = B::svref_2object( $_[0] );

                    return    $b_obj->isa('B::HV') ? { %{ $_[0] } }

                            : $b_obj->isa('B::AV') ? [ @{ $_[0] } ]

                            : undef

                            ;

                }

            | if ( !$_UNIV_CONV_BLESSED++ );
            next;
        }
        push @what_to_export, $tag;
    }

    return if ($no_export);

    __PACKAGE__->export_to_level(1, $pkg, @what_to_export);
}


# OBSOLETED

sub jsonToObj {
    my $alternative = 'from_json';
    if (defined $_[0] and UNIVERSAL::isa($_[0], 'JSON')) {
        shift @_; $alternative = 'decode';
    }
    Carp::carp "'jsonToObj' will be obsoleted. Please use '$alternative' instead.";
    return JSON::from_json(@_);
};

sub objToJson {
    my $alternative = 'to_json';
    if (defined $_[0] and UNIVERSAL::isa($_[0], 'JSON')) {
        shift @_; $alternative = 'encode';
    }
    Carp::carp "'objToJson' will be obsoleted. Please use '$alternative' instead.";
    JSON::to_json(@_);
};


# INTERFACES

sub to_json ($@) {
    if (
        ref($_[0]) eq 'JSON'
        or (@_ > 2 and $_[0] eq 'JSON')
    ) {
        Carp::croak "to_json should not be called as a method.";
    }
    my $json = JSON->new;

    if (@_ == 2 and ref $_[1] eq 'HASH') {
        my $opt  = $_[1];
        for my $method (keys %$opt) {
            $json->$method( $opt->{$method} );
        }
    }

    $json->encode($_[0]);
}


sub from_json ($@) {
    if ( ref($_[0]) eq 'JSON' or $_[0] eq 'JSON' ) {
        Carp::croak "from_json should not be called as a method.";
    }
    my $json = JSON->new;

    if (@_ == 2 and ref $_[1] eq 'HASH') {
        my $opt  = $_[1];
        for my $method (keys %$opt) {
            $json->$method( $opt->{$method} );
        }
    }

    return $json->decode( $_[0] );
}



sub true  { $JSON::true  }

sub false { $JSON::false }

sub null  { undef; }


sub require_xs_version { $XS_Version; }

sub backend {
    my $proto = shift;
    $JSON::Backend;
}

#*module = *backend;


sub is_xs {
    return $_[0]->backend eq $Module_XS;
}


sub is_pp {
    return not $_[0]->is_xs;
}


sub pureperl_only_methods { @PPOnlyMethods; }


sub property {
    my ($self, $name, $value) = @_;

    if (@_ == 1) {
        my %props;
        for $name (@Properties) {
            my $method = 'get_' . $name;
            if ($name eq 'max_size') {
                my $value = $self->$method();
                $props{$name} = $value == 1 ? 0 : $value;
                next;
            }
            $props{$name} = $self->$method();
        }
        return \%props;
    }
    elsif (@_ > 3) {
        Carp::croak('property() can take only the option within 2 arguments.');
    }
    elsif (@_ == 2) {
        if ( my $method = $self->can('get_' . $name) ) {
            if ($name eq 'max_size') {
                my $value = $self->$method();
                return $value == 1 ? 0 : $value;
            }
            $self->$method();
        }
    }
    else {
        $self->$name($value);
    }

}



# INTERNAL

sub _load_xs {
    my $opt = shift;

    $JSON::DEBUG and Carp::carp "Load $Module_XS.";

    # if called after install module, overload is disable.... why?
    JSON::Boolean::_overrride_overload($Module_XS);
    JSON::Boolean::_overrride_overload($Module_PP);

    eval qq|

        use $Module_XS $XS_Version ();

    |;

    if ($@) {
        if (defined $opt and $opt & $_INSTALL_DONT_DIE) {
            $JSON::DEBUG and Carp::carp "Can't load $Module_XS...($@)";
            return 0;
        }
        Carp::croak $@;
    }

    unless (defined $opt and $opt & $_INSTALL_ONLY) {
        _set_module( $JSON::Backend = $Module_XS );
        my $data = join("", <DATA>); # this code is from Jcode 2.xx.
        close(DATA);
        eval $data;
        JSON::Backend::XS->init;
    }

    return 1;
};


sub _load_pp {
    my $opt = shift;
    my $backend = $_USSING_bpPP ? $Module_bp : $Module_PP;

    $JSON::DEBUG and Carp::carp "Load $backend.";

    # if called after install module, overload is disable.... why?
    JSON::Boolean::_overrride_overload($Module_XS);
    JSON::Boolean::_overrride_overload($backend);

    if ( $_USSING_bpPP ) {
        eval qq| require $backend |;
    }
    else {
        eval qq| use $backend $PP_Version () |;
    }

    if ($@) {
        if ( $backend eq $Module_PP ) {
            $JSON::DEBUG and Carp::carp "Can't load $Module_PP ($@), so try to load $Module_bp";
            $_USSING_bpPP++;
            $backend = $Module_bp;
            JSON::Boolean::_overrride_overload($backend);
            local $^W; # if PP installed but invalid version, backportPP redefines methods.
            eval qq| require $Module_bp |;
        }
        Carp::croak $@ if $@;
    }

    unless (defined $opt and $opt & $_INSTALL_ONLY) {
        _set_module( $JSON::Backend = $Module_PP ); # even if backportPP, set $Backend with 'JSON::PP'
        JSON::Backend::PP->init;
    }
};


sub _set_module {
    return if defined $JSON::true;

    my $module = shift;

    local $^W;
    no strict qw(refs);

    $JSON::true  = ${"$module\::true"};
    $JSON::false = ${"$module\::false"};

    push @JSON::ISA, $module;
    if ( JSON->is_xs and JSON->backend->VERSION < 3 ) {
        eval 'package JSON::PP::Boolean';
        push @{"$module\::Boolean::ISA"}, qw(JSON::PP::Boolean);
    }

    *{"JSON::is_bool"} = \&{"$module\::is_bool"};

    for my $method ($module eq $Module_XS ? @PPOnlyMethods : @XSOnlyMethods) {
        *{"JSON::$method"} = sub {
            Carp::carp("$method is not supported in $module.");
            $_[0];
        };
    }

    return 1;
}



#
# JSON Boolean
#

package JSON::Boolean;

my %Installed;

sub _overrride_overload {
    return; # this function is currently disable.
    return if ($Installed{ $_[0] }++);

    my $boolean = $_[0] . '::Boolean';

    eval sprintf(q|

        package %s;

        use overload (

            '""' => sub { ${$_[0]} == 1 ? 'true' : 'false' },

            'eq' => sub {

                my ($obj, $op) = ref ($_[0]) ? ($_[0], $_[1]) : ($_[1], $_[0]);

                if ($op eq 'true' or $op eq 'false') {

                    return "$obj" eq 'true' ? 'true' eq $op : 'false' eq $op;

                }

                else {

                    return $obj ? 1 == $op : 0 == $op;

                }

            },

        );

    |, $boolean);

    if ($@) { Carp::croak $@; }

    if ( exists $INC{'JSON/XS.pm'} and $boolean eq 'JSON::XS::Boolean' ) {
        local $^W;
        my $true  = do { bless \(my $dummy = 1), $boolean };
        my $false = do { bless \(my $dummy = 0), $boolean };
        *JSON::XS::true  = sub () { $true };
        *JSON::XS::false = sub () { $false };
    }
    elsif ( exists $INC{'JSON/PP.pm'} and $boolean eq 'JSON::PP::Boolean' ) {
        local $^W;
        my $true  = do { bless \(my $dummy = 1), $boolean };
        my $false = do { bless \(my $dummy = 0), $boolean };
        *JSON::PP::true  = sub { $true };
        *JSON::PP::false = sub { $false };
    }

    return 1;
}


#
# Helper classes for Backend Module (PP)
#

package JSON::Backend::PP;

sub init {
    local $^W;
    no strict qw(refs); # this routine may be called after JSON::Backend::XS init was called.
    *{"JSON::decode_json"} = \&{"JSON::PP::decode_json"};
    *{"JSON::encode_json"} = \&{"JSON::PP::encode_json"};
    *{"JSON::PP::is_xs"}  = sub { 0 };
    *{"JSON::PP::is_pp"}  = sub { 1 };
    return 1;
}

#
# To save memory, the below lines are read only when XS backend is used.
#

package JSON;

1;
__DATA__





#

# Helper classes for Backend Module (XS)

#



package JSON::Backend::XS;



use constant INDENT_LENGTH_FLAG => 15 << 12;



use constant UNSUPPORTED_ENCODE_FLAG => {

    ESCAPE_SLASH      => 0x00000010,

    ALLOW_BIGNUM      => 0x00000020,

    AS_NONBLESSED     => 0x00000040,

    EXPANDED          => 0x10000000, # for developer's

};



use constant UNSUPPORTED_DECODE_FLAG => {

    LOOSE             => 0x00000001,

    ALLOW_BIGNUM      => 0x00000002,

    ALLOW_BAREKEY     => 0x00000004,

    ALLOW_SINGLEQUOTE => 0x00000008,

    EXPANDED          => 0x20000000, # for developer's

};





sub init {

    local $^W;

    no strict qw(refs);

    *{"JSON::decode_json"} = \&{"JSON::XS::decode_json"};

    *{"JSON::encode_json"} = \&{"JSON::XS::encode_json"};

    *{"JSON::XS::is_xs"}  = sub { 1 };

    *{"JSON::XS::is_pp"}  = sub { 0 };

    return 1;

}





sub support_by_pp {

    my ($class, @methods) = @_;



    local $^W;

    no strict qw(refs);



    my $JSON_XS_encode_orignal     = \&JSON::XS::encode;

    my $JSON_XS_decode_orignal     = \&JSON::XS::decode;

    my $JSON_XS_incr_parse_orignal = \&JSON::XS::incr_parse;



    *JSON::XS::decode     = \&JSON::Backend::XS::Supportable::_decode;

    *JSON::XS::encode     = \&JSON::Backend::XS::Supportable::_encode;

    *JSON::XS::incr_parse = \&JSON::Backend::XS::Supportable::_incr_parse;



    *{JSON::XS::_original_decode}     = $JSON_XS_decode_orignal;

    *{JSON::XS::_original_encode}     = $JSON_XS_encode_orignal;

    *{JSON::XS::_original_incr_parse} = $JSON_XS_incr_parse_orignal;



    push @JSON::Backend::XS::Supportable::ISA, 'JSON';



    my $pkg = 'JSON::Backend::XS::Supportable';



    *{JSON::new} = sub {

        my $proto = JSON::XS->new; $$proto = 0;

        bless  $proto, $pkg;

    };





    for my $method (@methods) {

        my $flag = uc($method);

        my $type |= (UNSUPPORTED_ENCODE_FLAG->{$flag} || 0);

           $type |= (UNSUPPORTED_DECODE_FLAG->{$flag} || 0);



        next unless($type);



        $pkg->_make_unsupported_method($method => $type);

    }



#    push @{"JSON::XS::Boolean::ISA"}, qw(JSON::PP::Boolean);

#    push @{"JSON::PP::Boolean::ISA"}, qw(JSON::Boolean);



    $JSON::DEBUG and Carp::carp("set -support_by_pp mode.");



    return 1;

}









#

# Helper classes for XS

#



package JSON::Backend::XS::Supportable;



$Carp::Internal{'JSON::Backend::XS::Supportable'} = 1;



sub _make_unsupported_method {

    my ($pkg, $method, $type) = @_;



    local $^W;

    no strict qw(refs);



    *{"$pkg\::$method"} = sub {

        local $^W;

        if (defined $_[1] ? $_[1] : 1) {

            ${$_[0]} |= $type;

        }

        else {

            ${$_[0]} &= ~$type;

        }

        $_[0];

    };



    *{"$pkg\::get_$method"} = sub {

        ${$_[0]} & $type ? 1 : '';

    };



}





sub _set_for_pp {

    JSON::_load_pp( $_INSTALL_ONLY );



    my $type  = shift;

    my $pp    = JSON::PP->new;

    my $prop = $_[0]->property;



    for my $name (keys %$prop) {

        $pp->$name( $prop->{$name} ? $prop->{$name} : 0 );

    }



    my $unsupported = $type eq 'encode' ? JSON::Backend::XS::UNSUPPORTED_ENCODE_FLAG

                                        : JSON::Backend::XS::UNSUPPORTED_DECODE_FLAG;

    my $flags       = ${$_[0]} || 0;



    for my $name (keys %$unsupported) {

        next if ($name eq 'EXPANDED'); # for developer's

        my $enable = ($flags & $unsupported->{$name}) ? 1 : 0;

        my $method = lc $name;

        $pp->$method($enable);

    }



    $pp->indent_length( $_[0]->get_indent_length );



    return $pp;

}



sub _encode { # using with PP encode

    if (${$_[0]}) {

        _set_for_pp('encode' => @_)->encode($_[1]);

    }

    else {

        $_[0]->_original_encode( $_[1] );

    }

}





sub _decode { # if unsupported-flag is set, use PP

    if (${$_[0]}) {

        _set_for_pp('decode' => @_)->decode($_[1]);

    }

    else {

        $_[0]->_original_decode( $_[1] );

    }

}





sub decode_prefix { # if unsupported-flag is set, use PP

    _set_for_pp('decode' => @_)->decode_prefix($_[1]);

}





sub _incr_parse {

    if (${$_[0]}) {

        _set_for_pp('decode' => @_)->incr_parse($_[1]);

    }

    else {

        $_[0]->_original_incr_parse( $_[1] );

    }

}





sub get_indent_length {

    ${$_[0]} << 4 >> 16;

}





sub indent_length {

    my $length = $_[1];



    if (!defined $length or $length > 15 or $length < 0) {

        Carp::carp "The acceptable range of indent_length() is 0 to 15.";

    }

    else {

        local $^W;

        $length <<= 12;

        ${$_[0]} &= ~ JSON::Backend::XS::INDENT_LENGTH_FLAG;

        ${$_[0]} |= $length;

        *JSON::XS::encode = \&JSON::Backend::XS::Supportable::_encode;

    }



    $_[0];

}





1;

__END__

=head1 NAME



JSON - JSON (JavaScript Object Notation) encoder/decoder



=head1 SYNOPSIS



 use JSON; # imports encode_json, decode_json, to_json and from_json.

 

 # simple and fast interfaces (expect/generate UTF-8)

 

 $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;

 $perl_hash_or_arrayref  = decode_json $utf8_encoded_json_text;

 

 # OO-interface

 

 $json = JSON->new->allow_nonref;

 

 $json_text   = $json->encode( $perl_scalar );

 $perl_scalar = $json->decode( $json_text );

 

 $pretty_printed = $json->pretty->encode( $perl_scalar ); # pretty-printing

 

 # If you want to use PP only support features, call with '-support_by_pp'

 # When XS unsupported feature is enable, using PP (de|en)code instead of XS ones.

 

 use JSON -support_by_pp;

 

 # option-acceptable interfaces (expect/generate UNICODE by default)

 

 $json_text   = to_json( $perl_scalar, { ascii => 1, pretty => 1 } );

 $perl_scalar = from_json( $json_text, { utf8  => 1 } );

 

 # Between (en|de)code_json and (to|from)_json, if you want to write

 # a code which communicates to an outer world (encoded in UTF-8),

 # recommend to use (en|de)code_json.

 

=head1 VERSION



    2.90



This version is compatible with JSON::XS B<2.34> and later.

(Not yet compatble to JSON::XS B<3.0x>.)





=head1 NOTE



JSON::PP was earlier included in the C<JSON> distribution, but

has since Perl 5.14 been a core module. For this reason,

L<JSON::PP> was removed from the JSON distribution and can now

be found also in the Perl5 repository at



=over



=item * L<http://perl5.git.perl.org/perl.git>



=back



(The newest JSON::PP version still exists in CPAN.)



Instead, the C<JSON> distribution will include JSON::backportPP

for backwards computability. JSON.pm should thus work as it did

before.



=head1 DESCRIPTION



 *************************** CAUTION **************************************

 *                                                                        *

 * INCOMPATIBLE CHANGE (JSON::XS version 2.90)                            *

 *                                                                        *

 * JSON.pm had patched JSON::XS::Boolean and JSON::PP::Boolean internally *

 * on loading time for making these modules inherit JSON::Boolean.        *

 * But since JSON::XS v3.0 it use Types::Serialiser as boolean class.     *

 * Then now JSON.pm breaks boolean classe overload features and           *

 * -support_by_pp if JSON::XS v3.0 or later is installed.                 *

 *                                                                        *

 * JSON::true and JSON::false returned JSON::Boolean objects.             *

 * For workaround, they return JSON::PP::Boolean objects in this version. *

 *                                                                        *

 *     isa_ok(JSON::true, 'JSON::PP::Boolean');                           *

 *                                                                        *

 * And it discards a feature:                                             *

 *                                                                        *

 *     ok(JSON::true eq 'true');                                          *

 *                                                                        *

 * In other word, JSON::PP::Boolean overload numeric only.                *

 *                                                                        *

 *     ok( JSON::true == 1 );                                             *

 *                                                                        *

 **************************************************************************



 ************************** CAUTION ********************************

 * This is 'JSON module version 2' and there are many differences  *

 * to version 1.xx                                                 *

 * Please check your applications using old version.              *

 *   See to 'INCOMPATIBLE CHANGES TO OLD VERSION'                  *

 *******************************************************************



JSON (JavaScript Object Notation) is a simple data format.

See to L<http://www.json.org/> and C<RFC4627>(L<http://www.ietf.org/rfc/rfc4627.txt>).



This module converts Perl data structures to JSON and vice versa using either

L<JSON::XS> or L<JSON::PP>.



JSON::XS is the fastest and most proper JSON module on CPAN which must be

compiled and installed in your environment.

JSON::PP is a pure-Perl module which is bundled in this distribution and

has a strong compatibility to JSON::XS.



This module try to use JSON::XS by default and fail to it, use JSON::PP instead.

So its features completely depend on JSON::XS or JSON::PP.



See to L<BACKEND MODULE DECISION>.



To distinguish the module name 'JSON' and the format type JSON,

the former is quoted by CE<lt>E<gt> (its results vary with your using media),

and the latter is left just as it is.



Module name : C<JSON>



Format type : JSON



=head2 FEATURES



=over



=item * correct unicode handling



This module (i.e. backend modules) knows how to handle Unicode, documents

how and when it does so, and even documents what "correct" means.



Even though there are limitations, this feature is available since Perl version 5.6.



JSON::XS requires Perl 5.8.2 (but works correctly in 5.8.8 or later), so in older versions

C<JSON> should call JSON::PP as the backend which can be used since Perl 5.005.



With Perl 5.8.x JSON::PP works, but from 5.8.0 to 5.8.2, because of a Perl side problem,

JSON::PP works slower in the versions. And in 5.005, the Unicode handling is not available.

See to L<JSON::PP/UNICODE HANDLING ON PERLS> for more information.



See also to L<JSON::XS/A FEW NOTES ON UNICODE AND PERL>

and L<JSON::XS/ENCODING/CODESET_FLAG_NOTES>.





=item * round-trip integrity



When you serialise a perl data structure using only data types supported

by JSON and Perl, the deserialised data structure is identical on the Perl

level. (e.g. the string "2.0" doesn't suddenly become "2" just because

it looks like a number). There I<are> minor exceptions to this, read the

L</MAPPING> section below to learn about those.





=item * strict checking of JSON correctness



There is no guessing, no generating of illegal JSON texts by default,

and only JSON is accepted as input by default (the latter is a security

feature).



See to L<JSON::XS/FEATURES> and L<JSON::PP/FEATURES>.



=item * fast



This module returns a JSON::XS object itself if available.

Compared to other JSON modules and other serialisers such as Storable,

JSON::XS usually compares favorably in terms of speed, too.



If not available, C<JSON> returns a JSON::PP object instead of JSON::XS and

it is very slow as pure-Perl.



=item * simple to use



This module has both a simple functional interface as well as an

object oriented interface interface.



=item * reasonably versatile output formats



You can choose between the most compact guaranteed-single-line format possible

(nice for simple line-based protocols), a pure-ASCII format (for when your transport

is not 8-bit clean, still supports the whole Unicode range), or a pretty-printed

format (for when you want to read that stuff). Or you can combine those features

in whatever way you like.



=back



=head1 FUNCTIONAL INTERFACE



Some documents are copied and modified from L<JSON::XS/FUNCTIONAL INTERFACE>.

C<to_json> and C<from_json> are additional functions.



=head2 encode_json



    $json_text = encode_json $perl_scalar



Converts the given Perl data structure to a UTF-8 encoded, binary string.



This function call is functionally identical to:



    $json_text = JSON->new->utf8->encode($perl_scalar)



=head2 decode_json



    $perl_scalar = decode_json $json_text



The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries

to parse that as an UTF-8 encoded JSON text, returning the resulting

reference.



This function call is functionally identical to:



    $perl_scalar = JSON->new->utf8->decode($json_text)





=head2 to_json



   $json_text = to_json($perl_scalar)



Converts the given Perl data structure to a json string.



This function call is functionally identical to:



   $json_text = JSON->new->encode($perl_scalar)



Takes a hash reference as the second.



   $json_text = to_json($perl_scalar, $flag_hashref)



So,



   $json_text = to_json($perl_scalar, {utf8 => 1, pretty => 1})



equivalent to:



   $json_text = JSON->new->utf8(1)->pretty(1)->encode($perl_scalar)



If you want to write a modern perl code which communicates to outer world,

you should use C<encode_json> (supposed that JSON data are encoded in UTF-8).



=head2 from_json



   $perl_scalar = from_json($json_text)



The opposite of C<to_json>: expects a json string and tries

to parse it, returning the resulting reference.



This function call is functionally identical to:



    $perl_scalar = JSON->decode($json_text)



Takes a hash reference as the second.



    $perl_scalar = from_json($json_text, $flag_hashref)



So,



    $perl_scalar = from_json($json_text, {utf8 => 1})



equivalent to:



    $perl_scalar = JSON->new->utf8(1)->decode($json_text)



If you want to write a modern perl code which communicates to outer world,

you should use C<decode_json> (supposed that JSON data are encoded in UTF-8).



=head2 JSON::is_bool



    $is_boolean = JSON::is_bool($scalar)



Returns true if the passed scalar represents either JSON::true or

JSON::false, two constants that act like C<1> and C<0> respectively

and are also used to represent JSON C<true> and C<false> in Perl strings.



=head2 JSON::true



Returns JSON true value which is blessed object.

It C<isa> JSON::Boolean object.



=head2 JSON::false



Returns JSON false value which is blessed object.

It C<isa> JSON::Boolean object.



=head2 JSON::null



Returns C<undef>.



See L<MAPPING>, below, for more information on how JSON values are mapped to

Perl.



=head1 HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER



This section supposes that your perl version is 5.8 or later.



If you know a JSON text from an outer world - a network, a file content, and so on,

is encoded in UTF-8, you should use C<decode_json> or C<JSON> module object

with C<utf8> enable. And the decoded result will contain UNICODE characters.



  # from network

  my $json        = JSON->new->utf8;

  my $json_text   = CGI->new->param( 'json_data' );

  my $perl_scalar = $json->decode( $json_text );

  

  # from file content

  local $/;

  open( my $fh, '<', 'json.data' );

  $json_text   = <$fh>;

  $perl_scalar = decode_json( $json_text );



If an outer data is not encoded in UTF-8, firstly you should C<decode> it.



  use Encode;

  local $/;

  open( my $fh, '<', 'json.data' );

  my $encoding = 'cp932';

  my $unicode_json_text = decode( $encoding, <$fh> ); # UNICODE

  

  # or you can write the below code.

  #

  # open( my $fh, "<:encoding($encoding)", 'json.data' );

  # $unicode_json_text = <$fh>;



In this case, C<$unicode_json_text> is of course UNICODE string.

So you B<cannot> use C<decode_json> nor C<JSON> module object with C<utf8> enable.

Instead of them, you use C<JSON> module object with C<utf8> disable or C<from_json>.



  $perl_scalar = $json->utf8(0)->decode( $unicode_json_text );

  # or

  $perl_scalar = from_json( $unicode_json_text );



Or C<encode 'utf8'> and C<decode_json>:



  $perl_scalar = decode_json( encode( 'utf8', $unicode_json_text ) );

  # this way is not efficient.



And now, you want to convert your C<$perl_scalar> into JSON data and

send it to an outer world - a network or a file content, and so on.



Your data usually contains UNICODE strings and you want the converted data to be encoded

in UTF-8, you should use C<encode_json> or C<JSON> module object with C<utf8> enable.



  print encode_json( $perl_scalar ); # to a network? file? or display?

  # or

  print $json->utf8->encode( $perl_scalar );



If C<$perl_scalar> does not contain UNICODE but C<$encoding>-encoded strings

for some reason, then its characters are regarded as B<latin1> for perl

(because it does not concern with your $encoding).

You B<cannot> use C<encode_json> nor C<JSON> module object with C<utf8> enable.

Instead of them, you use C<JSON> module object with C<utf8> disable or C<to_json>.

Note that the resulted text is a UNICODE string but no problem to print it.



  # $perl_scalar contains $encoding encoded string values

  $unicode_json_text = $json->utf8(0)->encode( $perl_scalar );

  # or 

  $unicode_json_text = to_json( $perl_scalar );

  # $unicode_json_text consists of characters less than 0x100

  print $unicode_json_text;



Or C<decode $encoding> all string values and C<encode_json>:



  $perl_scalar->{ foo } = decode( $encoding, $perl_scalar->{ foo } );

  # ... do it to each string values, then encode_json

  $json_text = encode_json( $perl_scalar );



This method is a proper way but probably not efficient.



See to L<Encode>, L<perluniintro>.





=head1 COMMON OBJECT-ORIENTED INTERFACE



=head2 new



    $json = JSON->new



Returns a new C<JSON> object inherited from either JSON::XS or JSON::PP

that can be used to de/encode JSON strings.



All boolean flags described below are by default I<disabled>.



The mutators for flags all return the JSON object again and thus calls can

be chained:



   my $json = JSON->new->utf8->space_after->encode({a => [1,2]})

   => {"a": [1, 2]}



=head2 ascii



    $json = $json->ascii([$enable])

    

    $enabled = $json->get_ascii



If $enable is true (or missing), then the encode method will not generate characters outside

the code range 0..127. Any Unicode characters outside that range will be escaped using either

a single \uXXXX or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.



If $enable is false, then the encode method will not escape Unicode characters unless

required by the JSON syntax or other flags. This results in a faster and more compact format.



This feature depends on the used Perl version and environment.



See to L<JSON::PP/UNICODE HANDLING ON PERLS> if the backend is PP.



  JSON->new->ascii(1)->encode([chr 0x10401])

  => ["\ud801\udc01"]



=head2 latin1



    $json = $json->latin1([$enable])

    

    $enabled = $json->get_latin1



If $enable is true (or missing), then the encode method will encode the resulting JSON

text as latin1 (or iso-8859-1), escaping any characters outside the code range 0..255.



If $enable is false, then the encode method will not escape Unicode characters

unless required by the JSON syntax or other flags.



  JSON->new->latin1->encode (["\x{89}\x{abc}"]

  => ["\x{89}\\u0abc"]    # (perl syntax, U+abc escaped, U+89 not)



=head2 utf8



    $json = $json->utf8([$enable])

    

    $enabled = $json->get_utf8



If $enable is true (or missing), then the encode method will encode the JSON result

into UTF-8, as required by many protocols, while the decode method expects to be handled

an UTF-8-encoded string. Please note that UTF-8-encoded strings do not contain any

characters outside the range 0..255, they are thus useful for bytewise/binary I/O.



In future versions, enabling this option might enable autodetection of the UTF-16 and UTF-32

encoding families, as described in RFC4627.



If $enable is false, then the encode method will return the JSON string as a (non-encoded)

Unicode string, while decode expects thus a Unicode string. Any decoding or encoding

(e.g. to UTF-8 or UTF-16) needs to be done yourself, e.g. using the Encode module.





Example, output UTF-16BE-encoded JSON:



  use Encode;

  $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);



Example, decode UTF-32LE-encoded JSON:



  use Encode;

  $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);



See to L<JSON::PP/UNICODE HANDLING ON PERLS> if the backend is PP.





=head2 pretty



    $json = $json->pretty([$enable])



This enables (or disables) all of the C<indent>, C<space_before> and

C<space_after> (and in the future possibly more) flags in one call to

generate the most readable (or most compact) form possible.



Equivalent to:



   $json->indent->space_before->space_after



The indent space length is three and JSON::XS cannot change the indent

space length.



=head2 indent



    $json = $json->indent([$enable])

    

    $enabled = $json->get_indent



If C<$enable> is true (or missing), then the C<encode> method will use a multiline

format as output, putting every array member or object/hash key-value pair

into its own line, identifying them properly.



If C<$enable> is false, no newlines or indenting will be produced, and the

resulting JSON text is guaranteed not to contain any C<newlines>.



This setting has no effect when decoding JSON texts.



The indent space length is three.

With JSON::PP, you can also access C<indent_length> to change indent space length.





=head2 space_before



    $json = $json->space_before([$enable])

    

    $enabled = $json->get_space_before



If C<$enable> is true (or missing), then the C<encode> method will add an extra

optional space before the C<:> separating keys from values in JSON objects.



If C<$enable> is false, then the C<encode> method will not add any extra

space at those places.



This setting has no effect when decoding JSON texts.



Example, space_before enabled, space_after and indent disabled:



   {"key" :"value"}





=head2 space_after



    $json = $json->space_after([$enable])

    

    $enabled = $json->get_space_after



If C<$enable> is true (or missing), then the C<encode> method will add an extra

optional space after the C<:> separating keys from values in JSON objects

and extra whitespace after the C<,> separating key-value pairs and array

members.



If C<$enable> is false, then the C<encode> method will not add any extra

space at those places.



This setting has no effect when decoding JSON texts.



Example, space_before and indent disabled, space_after enabled:



   {"key": "value"}





=head2 relaxed



    $json = $json->relaxed([$enable])

    

    $enabled = $json->get_relaxed



If C<$enable> is true (or missing), then C<decode> will accept some

extensions to normal JSON syntax (see below). C<encode> will not be

affected in anyway. I<Be aware that this option makes you accept invalid

JSON texts as if they were valid!>. I suggest only to use this option to

parse application-specific files written by humans (configuration files,

resource files etc.)



If C<$enable> is false (the default), then C<decode> will only accept

valid JSON texts.



Currently accepted extensions are:



=over 4



=item * list items can have an end-comma



JSON I<separates> array elements and key-value pairs with commas. This

can be annoying if you write JSON texts manually and want to be able to

quickly append elements, so this extension accepts comma at the end of

such items not just between them:



   [

      1,

      2, <- this comma not normally allowed

   ]

   {

      "k1": "v1",

      "k2": "v2", <- this comma not normally allowed

   }



=item * shell-style '#'-comments



Whenever JSON allows whitespace, shell-style comments are additionally

allowed. They are terminated by the first carriage-return or line-feed

character, after which more white-space and comments are allowed.



  [

     1, # this comment not allowed in JSON

        # neither this one...

  ]



=back





=head2 canonical



    $json = $json->canonical([$enable])

    

    $enabled = $json->get_canonical



If C<$enable> is true (or missing), then the C<encode> method will output JSON objects

by sorting their keys. This is adding a comparatively high overhead.



If C<$enable> is false, then the C<encode> method will output key-value

pairs in the order Perl stores them (which will likely change between runs

of the same script).



This option is useful if you want the same data structure to be encoded as

the same JSON text (given the same overall settings). If it is disabled,

the same hash might be encoded differently even if contains the same data,

as key-value pairs have no inherent ordering in Perl.



This setting has no effect when decoding JSON texts.



=head2 allow_nonref



    $json = $json->allow_nonref([$enable])

    

    $enabled = $json->get_allow_nonref



If C<$enable> is true (or missing), then the C<encode> method can convert a

non-reference into its corresponding string, number or null JSON value,

which is an extension to RFC4627. Likewise, C<decode> will accept those JSON

values instead of croaking.



If C<$enable> is false, then the C<encode> method will croak if it isn't

passed an arrayref or hashref, as JSON texts must either be an object

or array. Likewise, C<decode> will croak if given something that is not a

JSON object or array.



   JSON->new->allow_nonref->encode ("Hello, World!")

   => "Hello, World!"



=head2 allow_unknown



    $json = $json->allow_unknown ([$enable])

    

    $enabled = $json->get_allow_unknown



If $enable is true (or missing), then "encode" will *not* throw an

exception when it encounters values it cannot represent in JSON (for

example, filehandles) but instead will encode a JSON "null" value.

Note that blessed objects are not included here and are handled

separately by c<allow_nonref>.



If $enable is false (the default), then "encode" will throw an

exception when it encounters anything it cannot encode as JSON.



This option does not affect "decode" in any way, and it is

recommended to leave it off unless you know your communications

partner.



=head2 allow_blessed



    $json = $json->allow_blessed([$enable])

    

    $enabled = $json->get_allow_blessed



If C<$enable> is true (or missing), then the C<encode> method will not

barf when it encounters a blessed reference. Instead, the value of the

B<convert_blessed> option will decide whether C<null> (C<convert_blessed>

disabled or no C<TO_JSON> method found) or a representation of the

object (C<convert_blessed> enabled and C<TO_JSON> method found) is being

encoded. Has no effect on C<decode>.



If C<$enable> is false (the default), then C<encode> will throw an

exception when it encounters a blessed object.





=head2 convert_blessed



    $json = $json->convert_blessed([$enable])

    

    $enabled = $json->get_convert_blessed



If C<$enable> is true (or missing), then C<encode>, upon encountering a

blessed object, will check for the availability of the C<TO_JSON> method

on the object's class. If found, it will be called in scalar context

and the resulting scalar will be encoded instead of the object. If no

C<TO_JSON> method is found, the value of C<allow_blessed> will decide what

to do.



The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>

returns other blessed objects, those will be handled in the same

way. C<TO_JSON> must take care of not causing an endless recursion cycle

(== crash) in this case. The name of C<TO_JSON> was chosen because other

methods called by the Perl core (== not by the user of the object) are

usually in upper case letters and to avoid collisions with the C<to_json>

function or method.



This setting does not yet influence C<decode> in any way.



If C<$enable> is false, then the C<allow_blessed> setting will decide what

to do when a blessed object is found.



=over



=item convert_blessed_universally mode



If use C<JSON> with C<-convert_blessed_universally>, the C<UNIVERSAL::TO_JSON>

subroutine is defined as the below code:



   *UNIVERSAL::TO_JSON = sub {

       my $b_obj = B::svref_2object( $_[0] );

       return    $b_obj->isa('B::HV') ? { %{ $_[0] } }

               : $b_obj->isa('B::AV') ? [ @{ $_[0] } ]

               : undef

               ;

   }



This will cause that C<encode> method converts simple blessed objects into

JSON objects as non-blessed object.



   JSON -convert_blessed_universally;

   $json->allow_blessed->convert_blessed->encode( $blessed_object )



This feature is experimental and may be removed in the future.



=back



=head2 filter_json_object



    $json = $json->filter_json_object([$coderef])



When C<$coderef> is specified, it will be called from C<decode> each

time it decodes a JSON object. The only argument passed to the coderef

is a reference to the newly-created hash. If the code references returns

a single scalar (which need not be a reference), this value

(i.e. a copy of that scalar to avoid aliasing) is inserted into the

deserialised data structure. If it returns an empty list

(NOTE: I<not> C<undef>, which is a valid scalar), the original deserialised

hash will be inserted. This setting can slow down decoding considerably.



When C<$coderef> is omitted or undefined, any existing callback will

be removed and C<decode> will not change the deserialised hash in any

way.



Example, convert all JSON objects into the integer 5:



   my $js = JSON->new->filter_json_object (sub { 5 });

   # returns [5]

   $js->decode ('[{}]'); # the given subroutine takes a hash reference.

   # throw an exception because allow_nonref is not enabled

   # so a lone 5 is not allowed.

   $js->decode ('{"a":1, "b":2}');





=head2 filter_json_single_key_object



    $json = $json->filter_json_single_key_object($key [=> $coderef])



Works remotely similar to C<filter_json_object>, but is only called for

JSON objects having a single key named C<$key>.



This C<$coderef> is called before the one specified via

C<filter_json_object>, if any. It gets passed the single value in the JSON

object. If it returns a single value, it will be inserted into the data

structure. If it returns nothing (not even C<undef> but the empty list),

the callback from C<filter_json_object> will be called next, as if no

single-key callback were specified.



If C<$coderef> is omitted or undefined, the corresponding callback will be

disabled. There can only ever be one callback for a given key.



As this callback gets called less often then the C<filter_json_object>

one, decoding speed will not usually suffer as much. Therefore, single-key

objects make excellent targets to serialise Perl objects into, especially

as single-key JSON objects are as close to the type-tagged value concept

as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not

support this in any way, so you need to make sure your data never looks

like a serialised Perl hash.



Typical names for the single object key are C<__class_whatever__>, or

C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even

things like C<__class_md5sum(classname)__>, to reduce the risk of clashing

with real hashes.



Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>

into the corresponding C<< $WIDGET{<id>} >> object:



   # return whatever is in $WIDGET{5}:

   JSON

      ->new

      ->filter_json_single_key_object (__widget__ => sub {

            $WIDGET{ $_[0] }

         })

      ->decode ('{"__widget__": 5')



   # this can be used with a TO_JSON method in some "widget" class

   # for serialisation to json:

   sub WidgetBase::TO_JSON {

      my ($self) = @_;



      unless ($self->{id}) {

         $self->{id} = ..get..some..id..;

         $WIDGET{$self->{id}} = $self;

      }



      { __widget__ => $self->{id} }

   }





=head2 shrink



    $json = $json->shrink([$enable])

    

    $enabled = $json->get_shrink



With JSON::XS, this flag resizes strings generated by either

C<encode> or C<decode> to their minimum size possible. This can save

memory when your JSON texts are either very very long or you have many

short strings. It will also try to downgrade any strings to octet-form

if possible: perl stores strings internally either in an encoding called

UTF-X or in octet-form. The latter cannot store everything but uses less

space in general (and some buggy Perl or C code might even rely on that

internal representation being used).



With JSON::PP, it is noop about resizing strings but tries

C<utf8::downgrade> to the returned string by C<encode>. See to L<utf8>.



See to L<JSON::XS/OBJECT-ORIENTED INTERFACE> and L<JSON::PP/METHODS>.



=head2 max_depth



    $json = $json->max_depth([$maximum_nesting_depth])

    

    $max_depth = $json->get_max_depth



Sets the maximum nesting level (default C<512>) accepted while encoding

or decoding. If a higher nesting level is detected in JSON text or a Perl

data structure, then the encoder and decoder will stop and croak at that

point.



Nesting level is defined by number of hash- or arrayrefs that the encoder

needs to traverse to reach a given point or the number of C<{> or C<[>

characters without their matching closing parenthesis crossed to reach a

given character in a string.



If no argument is given, the highest possible setting will be used, which

is rarely useful.



Note that nesting is implemented by recursion in C. The default value has

been chosen to be as large as typical operating systems allow without

crashing. (JSON::XS)



With JSON::PP as the backend, when a large value (100 or more) was set and

it de/encodes a deep nested object/text, it may raise a warning

'Deep recursion on subroutine' at the perl runtime phase.



See L<JSON::XS/SECURITY CONSIDERATIONS> for more info on why this is useful.



=head2 max_size



    $json = $json->max_size([$maximum_string_size])

    

    $max_size = $json->get_max_size



Set the maximum length a JSON text may have (in bytes) where decoding is

being attempted. The default is C<0>, meaning no limit. When C<decode>

is called on a string that is longer then this many bytes, it will not

attempt to decode the string but throw an exception. This setting has no

effect on C<encode> (yet).



If no argument is given, the limit check will be deactivated (same as when

C<0> is specified).



See L<JSON::XS/SECURITY CONSIDERATIONS>, below, for more info on why this is useful.



=head2 encode



    $json_text = $json->encode($perl_scalar)



Converts the given Perl data structure (a simple scalar or a reference

to a hash or array) to its JSON representation. Simple scalars will be

converted into JSON string or number sequences, while references to arrays

become JSON arrays and references to hashes become JSON objects. Undefined

Perl values (e.g. C<undef>) become JSON C<null> values.

References to the integers C<0> and C<1> are converted into C<true> and C<false>.



=head2 decode



    $perl_scalar = $json->decode($json_text)



The opposite of C<encode>: expects a JSON text and tries to parse it,

returning the resulting simple scalar or reference. Croaks on error.



JSON numbers and strings become simple Perl scalars. JSON arrays become

Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes

C<1> (C<JSON::true>), C<false> becomes C<0> (C<JSON::false>) and

C<null> becomes C<undef>.



=head2 decode_prefix



    ($perl_scalar, $characters) = $json->decode_prefix($json_text)



This works like the C<decode> method, but instead of raising an exception

when there is trailing garbage after the first JSON object, it will

silently stop parsing there and return the number of characters consumed

so far.



   JSON->new->decode_prefix ("[1] the tail")

   => ([], 3)



See to L<JSON::XS/OBJECT-ORIENTED INTERFACE>



=head2 property



    $boolean = $json->property($property_name)



Returns a boolean value about above some properties.



The available properties are C<ascii>, C<latin1>, C<utf8>,

C<indent>,C<space_before>, C<space_after>, C<relaxed>, C<canonical>,

C<allow_nonref>, C<allow_unknown>, C<allow_blessed>, C<convert_blessed>,

C<shrink>, C<max_depth> and C<max_size>.



   $boolean = $json->property('utf8');

    => 0

   $json->utf8;

   $boolean = $json->property('utf8');

    => 1



Sets the property with a given boolean value.



    $json = $json->property($property_name => $boolean);



With no argument, it returns all the above properties as a hash reference.



    $flag_hashref = $json->property();



=head1 INCREMENTAL PARSING



Most of this section are copied and modified from L<JSON::XS/INCREMENTAL PARSING>.



In some cases, there is the need for incremental parsing of JSON texts.

This module does allow you to parse a JSON stream incrementally.

It does so by accumulating text until it has a full JSON object, which

it then can decode. This process is similar to using C<decode_prefix>

to see if a full JSON object is available, but is much more efficient

(and can be implemented with a minimum of method calls).



The backend module will only attempt to parse the JSON text once it is sure it

has enough text to get a decisive result, using a very simple but

truly incremental parser. This means that it sometimes won't stop as

early as the full parser, for example, it doesn't detect parenthesis

mismatches. The only thing it guarantees is that it starts decoding as

soon as a syntactically valid JSON text has been seen. This means you need

to set resource limits (e.g. C<max_size>) to ensure the parser will stop

parsing in the presence if syntax errors.



The following methods implement this incremental parser.



=head2 incr_parse



    $json->incr_parse( [$string] ) # void context

    

    $obj_or_undef = $json->incr_parse( [$string] ) # scalar context

    

    @obj_or_empty = $json->incr_parse( [$string] ) # list context



This is the central parsing function. It can both append new text and

extract objects from the stream accumulated so far (both of these

functions are optional).



If C<$string> is given, then this string is appended to the already

existing JSON fragment stored in the C<$json> object.



After that, if the function is called in void context, it will simply

return without doing anything further. This can be used to add more text

in as many chunks as you want.



If the method is called in scalar context, then it will try to extract

exactly I<one> JSON object. If that is successful, it will return this

object, otherwise it will return C<undef>. If there is a parse error,

this method will croak just as C<decode> would do (one can then use

C<incr_skip> to skip the erroneous part). This is the most common way of

using the method.



And finally, in list context, it will try to extract as many objects

from the stream as it can find and return them, or the empty list

otherwise. For this to work, there must be no separators between the JSON

objects or arrays, instead they must be concatenated back-to-back. If

an error occurs, an exception will be raised as in the scalar context

case. Note that in this case, any previously-parsed JSON texts will be

lost.



Example: Parse some JSON arrays/objects in a given string and return them.



    my @objs = JSON->new->incr_parse ("[5][7][1,2]");



=head2 incr_text



    $lvalue_string = $json->incr_text



This method returns the currently stored JSON fragment as an lvalue, that

is, you can manipulate it. This I<only> works when a preceding call to

C<incr_parse> in I<scalar context> successfully returned an object. Under

all other circumstances you must not call this function (I mean it.

although in simple tests it might actually work, it I<will> fail under

real world conditions). As a special exception, you can also call this

method before having parsed anything.



This function is useful in two cases: a) finding the trailing text after a

JSON object or b) parsing multiple JSON objects separated by non-JSON text

(such as commas).



    $json->incr_text =~ s/\s*,\s*//;



In Perl 5.005, C<lvalue> attribute is not available.

You must write codes like the below:



    $string = $json->incr_text;

    $string =~ s/\s*,\s*//;

    $json->incr_text( $string );



=head2 incr_skip



    $json->incr_skip



This will reset the state of the incremental parser and will remove the

parsed text from the input buffer. This is useful after C<incr_parse>

died, in which case the input buffer and incremental parser state is left

unchanged, to skip the text parsed so far and to reset the parse state.



=head2 incr_reset



    $json->incr_reset



This completely resets the incremental parser, that is, after this call,

it will be as if the parser had never parsed anything.



This is useful if you want to repeatedly parse JSON objects and want to

ignore any trailing data, which means you have to reset the parser after

each successful decode.



See to L<JSON::XS/INCREMENTAL PARSING> for examples.





=head1 JSON::PP SUPPORT METHODS



The below methods are JSON::PP own methods, so when C<JSON> works

with JSON::PP (i.e. the created object is a JSON::PP object), available.

See to L<JSON::PP/JSON::PP OWN METHODS> in detail.



If you use C<JSON> with additional C<-support_by_pp>, some methods

are available even with JSON::XS. See to L<USE PP FEATURES EVEN THOUGH XS BACKEND>.



   BEING { $ENV{PERL_JSON_BACKEND} = 'JSON::XS' }

   

   use JSON -support_by_pp;

   

   my $json = JSON->new;

   $json->allow_nonref->escape_slash->encode("/");



   # functional interfaces too.

   print to_json(["/"], {escape_slash => 1});

   print from_json('["foo"]', {utf8 => 1});



If you do not want to all functions but C<-support_by_pp>,

use C<-no_export>.



   use JSON -support_by_pp, -no_export;

   # functional interfaces are not exported.



=head2 allow_singlequote



    $json = $json->allow_singlequote([$enable])



If C<$enable> is true (or missing), then C<decode> will accept

any JSON strings quoted by single quotations that are invalid JSON

format.



    $json->allow_singlequote->decode({"foo":'bar'});

    $json->allow_singlequote->decode({'foo':"bar"});

    $json->allow_singlequote->decode({'foo':'bar'});



As same as the C<relaxed> option, this option may be used to parse

application-specific files written by humans.



=head2 allow_barekey



    $json = $json->allow_barekey([$enable])



If C<$enable> is true (or missing), then C<decode> will accept

bare keys of JSON object that are invalid JSON format.



As same as the C<relaxed> option, this option may be used to parse

application-specific files written by humans.



    $json->allow_barekey->decode('{foo:"bar"}');



=head2 allow_bignum



    $json = $json->allow_bignum([$enable])



If C<$enable> is true (or missing), then C<decode> will convert

the big integer Perl cannot handle as integer into a L<Math::BigInt>

object and convert a floating number (any) into a L<Math::BigFloat>.



On the contrary, C<encode> converts C<Math::BigInt> objects and C<Math::BigFloat>

objects into JSON numbers with C<allow_blessed> enable.



   $json->allow_nonref->allow_blessed->allow_bignum;

   $bigfloat = $json->decode('2.000000000000000000000000001');

   print $json->encode($bigfloat);

   # => 2.000000000000000000000000001



See to L<MAPPING> about the conversion of JSON number.



=head2 loose



    $json = $json->loose([$enable])



The unescaped [\x00-\x1f\x22\x2f\x5c] strings are invalid in JSON strings

and the module doesn't allow to C<decode> to these (except for \x2f).

If C<$enable> is true (or missing), then C<decode>  will accept these

unescaped strings.



    $json->loose->decode(qq|["abc

                                   def"]|);



See to L<JSON::PP/JSON::PP OWN METHODS>.



=head2 escape_slash



    $json = $json->escape_slash([$enable])



According to JSON Grammar, I<slash> (U+002F) is escaped. But by default

JSON backend modules encode strings without escaping slash.



If C<$enable> is true (or missing), then C<encode> will escape slashes.



=head2 indent_length



    $json = $json->indent_length($length)



With JSON::XS, The indent space length is 3 and cannot be changed.

With JSON::PP, it sets the indent space length with the given $length.

The default is 3. The acceptable range is 0 to 15.



=head2 sort_by



    $json = $json->sort_by($function_name)

    $json = $json->sort_by($subroutine_ref)



If $function_name or $subroutine_ref are set, its sort routine are used.



   $js = $pc->sort_by(sub { $JSON::PP::a cmp $JSON::PP::b })->encode($obj);

   # is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);



   $js = $pc->sort_by('own_sort')->encode($obj);

   # is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);



   sub JSON::PP::own_sort { $JSON::PP::a cmp $JSON::PP::b }



As the sorting routine runs in the JSON::PP scope, the given

subroutine name and the special variables C<$a>, C<$b> will begin

with 'JSON::PP::'.



If $integer is set, then the effect is same as C<canonical> on.



See to L<JSON::PP/JSON::PP OWN METHODS>.



=head1 MAPPING



This section is copied from JSON::XS and modified to C<JSON>.

JSON::XS and JSON::PP mapping mechanisms are almost equivalent.



See to L<JSON::XS/MAPPING>.



=head2 JSON -> PERL



=over 4



=item object



A JSON object becomes a reference to a hash in Perl. No ordering of object

keys is preserved (JSON does not preserver object key ordering itself).



=item array



A JSON array becomes a reference to an array in Perl.



=item string



A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON

are represented by the same codepoints in the Perl string, so no manual

decoding is necessary.



=item number



A JSON number becomes either an integer, numeric (floating point) or

string scalar in perl, depending on its range and any fractional parts. On

the Perl level, there is no difference between those as Perl handles all

the conversion details, but an integer may take slightly less memory and

might represent more values exactly than floating point numbers.



If the number consists of digits only, C<JSON> will try to represent

it as an integer value. If that fails, it will try to represent it as

a numeric (floating point) value if that is possible without loss of

precision. Otherwise it will preserve the number as a string value (in

which case you lose roundtripping ability, as the JSON number will be

re-encoded to a JSON string).



Numbers containing a fractional or exponential part will always be

represented as numeric (floating point) values, possibly at a loss of

precision (in which case you might lose perfect roundtripping ability, but

the JSON number will still be re-encoded as a JSON number).



Note that precision is not accuracy - binary floating point values cannot

represent most decimal fractions exactly, and when converting from and to

floating point, C<JSON> only guarantees precision up to but not including

the least significant bit.



If the backend is JSON::PP and C<allow_bignum> is enable, the big integers 

and the numeric can be optionally converted into L<Math::BigInt> and

L<Math::BigFloat> objects.



=item true, false



These JSON atoms become C<JSON::true> and C<JSON::false>,

respectively. They are overloaded to act almost exactly like the numbers

C<1> and C<0>. You can check whether a scalar is a JSON boolean by using

the C<JSON::is_bool> function.



   print JSON::true + 1;

    => 1



   ok(JSON::true eq  '1');

   ok(JSON::true == 1);



C<JSON> will install these missing overloading features to the backend modules.





=item null



A JSON null atom becomes C<undef> in Perl.



C<JSON::null> returns C<undef>.



=back





=head2 PERL -> JSON



The mapping from Perl to JSON is slightly more difficult, as Perl is a

truly typeless language, so we can only guess which JSON type is meant by

a Perl value.



=over 4



=item hash references



Perl hash references become JSON objects. As there is no inherent ordering

in hash keys (or JSON objects), they will usually be encoded in a

pseudo-random order that can change between runs of the same program but

stays generally the same within a single run of a program. C<JSON>

optionally sort the hash keys (determined by the I<canonical> flag), so

the same data structure will serialise to the same JSON text (given same

settings and version of JSON::XS), but this incurs a runtime overhead

and is only rarely useful, e.g. when you want to compare some JSON text

against another for equality.



In future, the ordered object feature will be added to JSON::PP using C<tie> mechanism.





=item array references



Perl array references become JSON arrays.



=item other references



Other unblessed references are generally not allowed and will cause an

exception to be thrown, except for references to the integers C<0> and

C<1>, which get turned into C<false> and C<true> atoms in JSON. You can

also use C<JSON::false> and C<JSON::true> to improve readability.



   to_json [\0,JSON::true]      # yields [false,true]



=item JSON::true, JSON::false, JSON::null



These special values become JSON true and JSON false values,

respectively. You can also use C<\1> and C<\0> directly if you want.



JSON::null returns C<undef>.



=item blessed objects



Blessed objects are not directly representable in JSON. See the

C<allow_blessed> and C<convert_blessed> methods on various options on

how to deal with this: basically, you can choose between throwing an

exception, encoding the reference as if it weren't blessed, or provide

your own serialiser method.



With C<convert_blessed_universally> mode,  C<encode> converts blessed

hash references or blessed array references (contains other blessed references)

into JSON members and arrays.



   use JSON -convert_blessed_universally;

   JSON->new->allow_blessed->convert_blessed->encode( $blessed_object );



See to L<convert_blessed>.



=item simple scalars



Simple Perl scalars (any scalar that is not a reference) are the most

difficult objects to encode: JSON::XS and JSON::PP will encode undefined scalars as

JSON C<null> values, scalars that have last been used in a string context

before encoding as JSON strings, and anything else as number value:



   # dump as number

   encode_json [2]                      # yields [2]

   encode_json [-3.0e17]                # yields [-3e+17]

   my $value = 5; encode_json [$value]  # yields [5]



   # used as string, so dump as string

   print $value;

   encode_json [$value]                 # yields ["5"]



   # undef becomes null

   encode_json [undef]                  # yields [null]



You can force the type to be a string by stringifying it:



   my $x = 3.1; # some variable containing a number

   "$x";        # stringified

   $x .= "";    # another, more awkward way to stringify

   print $x;    # perl does it for you, too, quite often



You can force the type to be a number by numifying it:



   my $x = "3"; # some variable containing a string

   $x += 0;     # numify it, ensuring it will be dumped as a number

   $x *= 1;     # same thing, the choice is yours.



You can not currently force the type in other, less obscure, ways.



Note that numerical precision has the same meaning as under Perl (so

binary to decimal conversion follows the same rules as in Perl, which

can differ to other languages). Also, your perl interpreter might expose

extensions to the floating point numbers of your platform, such as

infinities or NaN's - these cannot be represented in JSON, and it is an

error to pass those in.



=item Big Number



If the backend is JSON::PP and C<allow_bignum> is enable, 

C<encode> converts C<Math::BigInt> objects and C<Math::BigFloat>

objects into JSON numbers.





=back



=head1 JSON and ECMAscript



See to L<JSON::XS/JSON and ECMAscript>.



=head1 JSON and YAML



JSON is not a subset of YAML.

See to L<JSON::XS/JSON and YAML>.





=head1 BACKEND MODULE DECISION



When you use C<JSON>, C<JSON> tries to C<use> JSON::XS. If this call failed, it will

C<uses> JSON::PP. The required JSON::XS version is I<2.2> or later.



The C<JSON> constructor method returns an object inherited from the backend module,

and JSON::XS object is a blessed scalar reference while JSON::PP is a blessed hash

reference.



So, your program should not depend on the backend module, especially

returned objects should not be modified.



 my $json = JSON->new; # XS or PP?

 $json->{stash} = 'this is xs object'; # this code may raise an error!



To check the backend module, there are some methods - C<backend>, C<is_pp> and C<is_xs>.



  JSON->backend; # 'JSON::XS' or 'JSON::PP'

  

  JSON->backend->is_pp: # 0 or 1

  

  JSON->backend->is_xs: # 1 or 0

  

  $json->is_xs; # 1 or 0

  

  $json->is_pp; # 0 or 1





If you set an environment variable C<PERL_JSON_BACKEND>, the calling action will be changed.



=over



=item PERL_JSON_BACKEND = 0 or PERL_JSON_BACKEND = 'JSON::PP'



Always use JSON::PP



=item PERL_JSON_BACKEND == 1 or PERL_JSON_BACKEND = 'JSON::XS,JSON::PP'



(The default) Use compiled JSON::XS if it is properly compiled & installed,

otherwise use JSON::PP.



=item PERL_JSON_BACKEND == 2 or PERL_JSON_BACKEND = 'JSON::XS'



Always use compiled JSON::XS, die if it isn't properly compiled & installed.



=item PERL_JSON_BACKEND = 'JSON::backportPP'



Always use JSON::backportPP.

JSON::backportPP is JSON::PP back port module.

C<JSON> includes JSON::backportPP instead of JSON::PP.



=back



These ideas come from L<DBI::PurePerl> mechanism.



example:



 BEGIN { $ENV{PERL_JSON_BACKEND} = 'JSON::PP' }

 use JSON; # always uses JSON::PP



In future, it may be able to specify another module.



=head1 USE PP FEATURES EVEN THOUGH XS BACKEND



Many methods are available with either JSON::XS or JSON::PP and

when the backend module is JSON::XS, if any JSON::PP specific (i.e. JSON::XS unsupported)

method is called, it will C<warn> and be noop.



But If you C<use> C<JSON> passing the optional string C<-support_by_pp>,

it makes a part of those unsupported methods available.

This feature is achieved by using JSON::PP in C<de/encode>.



   BEGIN { $ENV{PERL_JSON_BACKEND} = 2 } # with JSON::XS

   use JSON -support_by_pp;

   my $json = JSON->new;

   $json->allow_nonref->escape_slash->encode("/");



At this time, the returned object is a C<JSON::Backend::XS::Supportable>

object (re-blessed XS object), and  by checking JSON::XS unsupported flags

in de/encoding, can support some unsupported methods - C<loose>, C<allow_bignum>,

C<allow_barekey>, C<allow_singlequote>, C<escape_slash> and C<indent_length>.



When any unsupported methods are not enable, C<XS de/encode> will be

used as is. The switch is achieved by changing the symbolic tables.



C<-support_by_pp> is effective only when the backend module is JSON::XS

and it makes the de/encoding speed down a bit.



See to L<JSON::PP SUPPORT METHODS>.



=head1 INCOMPATIBLE CHANGES TO OLD VERSION



There are big incompatibility between new version (2.00) and old (1.xx).

If you use old C<JSON> 1.xx in your code, please check it.



See to L<Transition ways from 1.xx to 2.xx.>



=over



=item jsonToObj and objToJson are obsoleted.



Non Perl-style name C<jsonToObj> and C<objToJson> are obsoleted

(but not yet deleted from the source).

If you use these functions in your code, please replace them

with C<from_json> and C<to_json>.





=item Global variables are no longer available.



C<JSON> class variables - C<$JSON::AUTOCONVERT>, C<$JSON::BareKey>, etc...

- are not available any longer.

Instead, various features can be used through object methods.





=item Package JSON::Converter and JSON::Parser are deleted.



Now C<JSON> bundles with JSON::PP which can handle JSON more properly than them.



=item Package JSON::NotString is deleted.



There was C<JSON::NotString> class which represents JSON value C<true>, C<false>, C<null>

and numbers. It was deleted and replaced by C<JSON::Boolean>.



C<JSON::Boolean> represents C<true> and C<false>.



C<JSON::Boolean> does not represent C<null>.



C<JSON::null> returns C<undef>.



C<JSON> makes L<JSON::XS::Boolean> and L<JSON::PP::Boolean> is-a relation

to L<JSON::Boolean>.



=item function JSON::Number is obsoleted.



C<JSON::Number> is now needless because JSON::XS and JSON::PP have

round-trip integrity.



=item JSONRPC modules are deleted.



Perl implementation of JSON-RPC protocol - C<JSONRPC >, C<JSONRPC::Transport::HTTP>

and C<Apache::JSONRPC > are deleted in this distribution.

Instead of them, there is L<JSON::RPC> which supports JSON-RPC protocol version 1.1.



=back



=head2 Transition ways from 1.xx to 2.xx.



You should set C<suport_by_pp> mode firstly, because

it is always successful for the below codes even with JSON::XS.



    use JSON -support_by_pp;



=over



=item Exported jsonToObj (simple)



  from_json($json_text);



=item Exported objToJson (simple)



  to_json($perl_scalar);



=item Exported jsonToObj (advanced)



  $flags = {allow_barekey => 1, allow_singlequote => 1};

  from_json($json_text, $flags);



equivalent to:



  $JSON::BareKey = 1;

  $JSON::QuotApos = 1;

  jsonToObj($json_text);



=item Exported objToJson (advanced)



  $flags = {allow_blessed => 1, allow_barekey => 1};

  to_json($perl_scalar, $flags);



equivalent to:



  $JSON::BareKey = 1;

  objToJson($perl_scalar);



=item jsonToObj as object method



  $json->decode($json_text);



=item objToJson as object method



  $json->encode($perl_scalar);



=item new method with parameters



The C<new> method in 2.x takes any parameters no longer.

You can set parameters instead;



   $json = JSON->new->pretty;



=item $JSON::Pretty, $JSON::Indent, $JSON::Delimiter



If C<indent> is enable, that means C<$JSON::Pretty> flag set. And

C<$JSON::Delimiter> was substituted by C<space_before> and C<space_after>.

In conclusion:



   $json->indent->space_before->space_after;



Equivalent to:



  $json->pretty;



To change indent length, use C<indent_length>.



(Only with JSON::PP, if C<-support_by_pp> is not used.)



  $json->pretty->indent_length(2)->encode($perl_scalar);



=item $JSON::BareKey



(Only with JSON::PP, if C<-support_by_pp> is not used.)



  $json->allow_barekey->decode($json_text)



=item $JSON::ConvBlessed



use C<-convert_blessed_universally>. See to L<convert_blessed>.



=item $JSON::QuotApos



(Only with JSON::PP, if C<-support_by_pp> is not used.)



  $json->allow_singlequote->decode($json_text)



=item $JSON::SingleQuote



Disable. C<JSON> does not make such a invalid JSON string any longer.



=item $JSON::KeySort



  $json->canonical->encode($perl_scalar)



This is the ascii sort.



If you want to use with your own sort routine, check the C<sort_by> method.



(Only with JSON::PP, even if C<-support_by_pp> is used currently.)



  $json->sort_by($sort_routine_ref)->encode($perl_scalar)

 

  $json->sort_by(sub { $JSON::PP::a <=> $JSON::PP::b })->encode($perl_scalar)



Can't access C<$a> and C<$b> but C<$JSON::PP::a> and C<$JSON::PP::b>.



=item $JSON::SkipInvalid



  $json->allow_unknown



=item $JSON::AUTOCONVERT



Needless. C<JSON> backend modules have the round-trip integrity.



=item $JSON::UTF8



Needless because C<JSON> (JSON::XS/JSON::PP) sets

the UTF8 flag on properly.



    # With UTF8-flagged strings



    $json->allow_nonref;

    $str = chr(1000); # UTF8-flagged



    $json_text  = $json->utf8(0)->encode($str);

    utf8::is_utf8($json_text);

    # true

    $json_text  = $json->utf8(1)->encode($str);

    utf8::is_utf8($json_text);

    # false



    $str = '"' . chr(1000) . '"'; # UTF8-flagged



    $perl_scalar  = $json->utf8(0)->decode($str);

    utf8::is_utf8($perl_scalar);

    # true

    $perl_scalar  = $json->utf8(1)->decode($str);

    # died because of 'Wide character in subroutine'



See to L<JSON::XS/A FEW NOTES ON UNICODE AND PERL>.



=item $JSON::UnMapping



Disable. See to L<MAPPING>.



=item $JSON::SelfConvert



This option was deleted.

Instead of it, if a given blessed object has the C<TO_JSON> method,

C<TO_JSON> will be executed with C<convert_blessed>.



  $json->convert_blessed->encode($blessed_hashref_or_arrayref)

  # if need, call allow_blessed



Note that it was C<toJson> in old version, but now not C<toJson> but C<TO_JSON>.



=back



=head1 TODO



=over



=item example programs



=back



=head1 THREADS



No test with JSON::PP. If with JSON::XS, See to L<JSON::XS/THREADS>.





=head1 BUGS



Please report bugs relevant to C<JSON> to E<lt>makamaka[at]cpan.orgE<gt>.





=head1 SEE ALSO



Most of the document is copied and modified from JSON::XS doc.



L<JSON::XS>, L<JSON::PP>



C<RFC4627>(L<http://www.ietf.org/rfc/rfc4627.txt>)



=head1 AUTHOR



Makamaka Hannyaharamitu, E<lt>makamaka[at]cpan.orgE<gt>



JSON::XS was written by  Marc Lehmann <schmorp[at]schmorp.de>



The release of this new version owes to the courtesy of Marc Lehmann.





=head1 COPYRIGHT AND LICENSE



Copyright 2005-2013 by Makamaka Hannyaharamitu



This library is free software; you can redistribute it and/or modify

it under the same terms as Perl itself. 



=cut