Blame lib/JSON.pm

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package JSON;
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use strict;
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use Carp ();
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use Exporter;
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BEGIN { @JSON::ISA = 'Exporter' }
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@JSON::EXPORT = qw(from_json to_json jsonToObj objToJson encode_json decode_json);
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BEGIN {
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    $JSON::VERSION = '2.97001';
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    $JSON::DEBUG   = 0 unless (defined $JSON::DEBUG);
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    $JSON::DEBUG   = $ENV{ PERL_JSON_DEBUG } if exists $ENV{ PERL_JSON_DEBUG };
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}
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my %RequiredVersion = (
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    'JSON::PP' => '2.27203',
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    'JSON::XS' => '2.34',
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);
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# XS and PP common methods
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my @PublicMethods = qw/
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    ascii latin1 utf8 pretty indent space_before space_after relaxed canonical allow_nonref 
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    allow_blessed convert_blessed filter_json_object filter_json_single_key_object 
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    shrink max_depth max_size encode decode decode_prefix allow_unknown
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/;
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my @Properties = qw/
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    ascii latin1 utf8 indent space_before space_after relaxed canonical allow_nonref
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    allow_blessed convert_blessed shrink max_depth max_size allow_unknown
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/;
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my @XSOnlyMethods = qw/allow_tags/; # Currently nothing
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my @PPOnlyMethods = qw/
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    indent_length sort_by
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    allow_singlequote allow_bignum loose allow_barekey escape_slash as_nonblessed
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/; # JSON::PP specific
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# used in _load_xs and _load_pp ($INSTALL_ONLY is not used currently)
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my $_INSTALL_DONT_DIE  = 1; # When _load_xs fails to load XS, don't die.
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my $_ALLOW_UNSUPPORTED = 0;
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my $_UNIV_CONV_BLESSED = 0;
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# Check the environment variable to decide worker module. 
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unless ($JSON::Backend) {
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    $JSON::DEBUG and  Carp::carp("Check used worker module...");
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    my $backend = exists $ENV{PERL_JSON_BACKEND} ? $ENV{PERL_JSON_BACKEND} : 1;
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    if ($backend eq '1') {
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        $backend = 'JSON::XS,JSON::PP';
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    }
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    elsif ($backend eq '0') {
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        $backend = 'JSON::PP';
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    }
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    elsif ($backend eq '2') {
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        $backend = 'JSON::XS';
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    }
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    $backend =~ s/\s+//g;
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    my @backend_modules = split /,/, $backend;
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    while(my $module = shift @backend_modules) {
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        if ($module =~ /JSON::XS/) {
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            _load_xs($module, @backend_modules ? $_INSTALL_DONT_DIE : 0);
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        }
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        elsif ($module =~ /JSON::PP/) {
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            _load_pp($module);
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        }
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        elsif ($module =~ /JSON::backportPP/) {
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            _load_pp($module);
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        }
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        else {
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            Carp::croak "The value of environmental variable 'PERL_JSON_BACKEND' is invalid.";
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        }
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        last if $JSON::Backend;
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    }
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}
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sub import {
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    my $pkg = shift;
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    my @what_to_export;
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    my $no_export;
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    for my $tag (@_) {
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        if ($tag eq '-support_by_pp') {
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            if (!$_ALLOW_UNSUPPORTED++) {
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                JSON::Backend::XS
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                    ->support_by_pp(@PPOnlyMethods) if ($JSON::Backend->is_xs);
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            }
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            next;
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        }
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        elsif ($tag eq '-no_export') {
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            $no_export++, next;
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        }
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        elsif ( $tag eq '-convert_blessed_universally' ) {
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            my $org_encode = $JSON::Backend->can('encode');
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            eval q|
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                require B;
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                local $^W;
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                no strict 'refs';
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                *{"${JSON::Backend}\::encode"} = sub {
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                    # only works with Perl 5.18+
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                    local *UNIVERSAL::TO_JSON = sub {
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                        my $b_obj = B::svref_2object( $_[0] );
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                        return    $b_obj->isa('B::HV') ? { %{ $_[0] } }
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                                : $b_obj->isa('B::AV') ? [ @{ $_[0] } ]
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                                : undef
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                                ;
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                    };
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                    $org_encode->(@_);
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                };
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            | if ( !$_UNIV_CONV_BLESSED++ );
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            next;
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        }
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        push @what_to_export, $tag;
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    }
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    return if ($no_export);
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    __PACKAGE__->export_to_level(1, $pkg, @what_to_export);
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}
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# OBSOLETED
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sub jsonToObj {
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    my $alternative = 'from_json';
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    if (defined $_[0] and UNIVERSAL::isa($_[0], 'JSON')) {
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        shift @_; $alternative = 'decode';
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    }
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    Carp::carp "'jsonToObj' will be obsoleted. Please use '$alternative' instead.";
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    return JSON::from_json(@_);
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};
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sub objToJson {
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    my $alternative = 'to_json';
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    if (defined $_[0] and UNIVERSAL::isa($_[0], 'JSON')) {
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        shift @_; $alternative = 'encode';
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    }
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    Carp::carp "'objToJson' will be obsoleted. Please use '$alternative' instead.";
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    JSON::to_json(@_);
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};
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# INTERFACES
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sub to_json ($@) {
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    if (
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        ref($_[0]) eq 'JSON'
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        or (@_ > 2 and $_[0] eq 'JSON')
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    ) {
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        Carp::croak "to_json should not be called as a method.";
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    }
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    my $json = JSON->new;
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    if (@_ == 2 and ref $_[1] eq 'HASH') {
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        my $opt  = $_[1];
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        for my $method (keys %$opt) {
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            $json->$method( $opt->{$method} );
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        }
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    }
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    $json->encode($_[0]);
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}
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sub from_json ($@) {
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    if ( ref($_[0]) eq 'JSON' or $_[0] eq 'JSON' ) {
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        Carp::croak "from_json should not be called as a method.";
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    }
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    my $json = JSON->new;
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    if (@_ == 2 and ref $_[1] eq 'HASH') {
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        my $opt  = $_[1];
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        for my $method (keys %$opt) {
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            $json->$method( $opt->{$method} );
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        }
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    }
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    return $json->decode( $_[0] );
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}
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sub true  { $JSON::true  }
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sub false { $JSON::false }
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sub null  { undef; }
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sub require_xs_version { $RequiredVersion{'JSON::XS'}; }
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sub backend {
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    my $proto = shift;
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    $JSON::Backend;
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}
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#*module = *backend;
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sub is_xs {
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    return $_[0]->backend->is_xs;
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}
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sub is_pp {
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    return $_[0]->backend->is_pp;
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}
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sub pureperl_only_methods { @PPOnlyMethods; }
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sub property {
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    my ($self, $name, $value) = @_;
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    if (@_ == 1) {
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        my %props;
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        for $name (@Properties) {
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            my $method = 'get_' . $name;
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            if ($name eq 'max_size') {
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                my $value = $self->$method();
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                $props{$name} = $value == 1 ? 0 : $value;
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                next;
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            }
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            $props{$name} = $self->$method();
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        }
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        return \%props;
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    }
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    elsif (@_ > 3) {
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        Carp::croak('property() can take only the option within 2 arguments.');
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    }
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    elsif (@_ == 2) {
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        if ( my $method = $self->can('get_' . $name) ) {
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            if ($name eq 'max_size') {
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                my $value = $self->$method();
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                return $value == 1 ? 0 : $value;
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            }
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            $self->$method();
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        }
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    }
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    else {
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        $self->$name($value);
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    }
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}
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# INTERNAL
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sub __load_xs {
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    my ($module, $opt) = @_;
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    $JSON::DEBUG and Carp::carp "Load $module.";
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    my $required_version = $RequiredVersion{$module} || '';
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    eval qq|
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        use $module $required_version ();
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    |;
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    if ($@) {
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        if (defined $opt and $opt & $_INSTALL_DONT_DIE) {
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            $JSON::DEBUG and Carp::carp "Can't load $module...($@)";
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            return 0;
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        }
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        Carp::croak $@;
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    }
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    $JSON::BackendModuleXS = $module;
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    return 1;
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}
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sub _load_xs {
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    my ($module, $opt) = @_;
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    __load_xs($module, $opt) or return;
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    my $data = join("", <DATA>); # this code is from Jcode 2.xx.
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    close(DATA);
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    eval $data;
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    JSON::Backend::XS->init($module);
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    return 1;
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};
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sub __load_pp {
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    my ($module, $opt) = @_;
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    $JSON::DEBUG and Carp::carp "Load $module.";
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    my $required_version = $RequiredVersion{$module} || '';
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    eval qq| use $module $required_version () |;
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    if ($@) {
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        if ( $module eq 'JSON::PP' ) {
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            $JSON::DEBUG and Carp::carp "Can't load $module ($@), so try to load JSON::backportPP";
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            $module = 'JSON::backportPP';
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            local $^W; # if PP installed but invalid version, backportPP redefines methods.
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            eval qq| require $module |;
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        }
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        Carp::croak $@ if $@;
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    }
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    $JSON::BackendModulePP = $module;
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    return 1;
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}
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sub _load_pp {
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    my ($module, $opt) = @_;
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    __load_pp($module, $opt);
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    JSON::Backend::PP->init($module);
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};
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#
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# Helper classes for Backend Module (PP)
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#
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package JSON::Backend::PP;
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sub init {
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    my ($class, $module) = @_;
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    # name may vary, but the module should (always) be a JSON::PP
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    local $^W;
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    no strict qw(refs); # this routine may be called after JSON::Backend::XS init was called.
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    *{"JSON::decode_json"} = \&{"JSON::PP::decode_json"};
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    *{"JSON::encode_json"} = \&{"JSON::PP::encode_json"};
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    *{"JSON::is_bool"} = \&{"JSON::PP::is_bool"};
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    $JSON::true  = ${"JSON::PP::true"};
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    $JSON::false = ${"JSON::PP::false"};
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    push @JSON::Backend::PP::ISA, 'JSON::PP';
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    push @JSON::ISA, $class;
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    $JSON::Backend = $class;
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    $JSON::BackendModule = $module;
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    ${"$class\::VERSION"} = $module->VERSION;
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    for my $method (@XSOnlyMethods) {
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        *{"JSON::$method"} = sub {
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            Carp::carp("$method is not supported in $module.");
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            $_[0];
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        };
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    }
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    return 1;
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}
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sub is_xs { 0 };
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sub is_pp { 1 };
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#
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# To save memory, the below lines are read only when XS backend is used.
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#
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package JSON;
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1;
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__DATA__
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#
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# Helper classes for Backend Module (XS)
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#
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package JSON::Backend::XS;
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sub init {
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    my ($class, $module) = @_;
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    local $^W;
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    no strict qw(refs);
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    *{"JSON::decode_json"} = \&{"$module\::decode_json"};
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    *{"JSON::encode_json"} = \&{"$module\::encode_json"};
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    *{"JSON::is_bool"} = \&{"$module\::is_bool"};
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    $JSON::true  = ${"$module\::true"};
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    $JSON::false = ${"$module\::false"};
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    push @JSON::Backend::XS::ISA, $module;
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    push @JSON::ISA, $class;
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    $JSON::Backend = $class;
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    $JSON::BackendModule = $module;
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    ${"$class\::VERSION"} = $module->VERSION;
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    if ( $module->VERSION < 3 ) {
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        eval 'package JSON::PP::Boolean';
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        push @{"$module\::Boolean::ISA"}, qw(JSON::PP::Boolean);
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    }
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    for my $method (@PPOnlyMethods) {
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        *{"JSON::$method"} = sub {
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            Carp::carp("$method is not supported in $module.");
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            $_[0];
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        };
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    }
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    return 1;
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}
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sub is_xs { 1 };
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sub is_pp { 0 };
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sub support_by_pp {
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    my ($class, @methods) = @_;
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    JSON::__load_pp('JSON::PP');
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    local $^W;
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    no strict qw(refs);
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    for my $method (@methods) {
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        my $pp_method = JSON::PP->can($method) or next;
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        *{"JSON::$method"} = sub {
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            if (!$_[0]->isa('JSON::PP')) {
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                my $xs_self = $_[0];
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                my $pp_self = JSON::PP->new;
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                for (@Properties) {
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                     my $getter = "get_$_";
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                    $pp_self->$_($xs_self->$getter);
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                }
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                $_[0] = $pp_self;
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            }
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            $pp_method->(@_);
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        };
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    }
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    $JSON::DEBUG and Carp::carp("set -support_by_pp mode.");
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}
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1;
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__END__
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=head1 NAME
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JSON - JSON (JavaScript Object Notation) encoder/decoder
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=head1 SYNOPSIS
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 use JSON; # imports encode_json, decode_json, to_json and from_json.
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 # simple and fast interfaces (expect/generate UTF-8)
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 $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
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 $perl_hash_or_arrayref  = decode_json $utf8_encoded_json_text;
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 # OO-interface
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 $json = JSON->new->allow_nonref;
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 $json_text   = $json->encode( $perl_scalar );
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 $perl_scalar = $json->decode( $json_text );
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 $pretty_printed = $json->pretty->encode( $perl_scalar ); # pretty-printing
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=head1 VERSION
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    2.97001
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=head1 DESCRIPTION
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This module is a thin wrapper for L<JSON::XS>-compatible modules with a few
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additional features. All the backend modules convert a Perl data structure
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to a JSON text as of RFC4627 (which we know is obsolete but we still stick
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to; see below for an option to support part of RFC7159) and vice versa.
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This module uses L<JSON::XS> by default, and when JSON::XS is not available,
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this module falls back on L<JSON::PP>, which is in the Perl core since 5.14.
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If JSON::PP is not available either, this module then falls back on
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JSON::backportPP (which is actually JSON::PP in a different .pm file)
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bundled in the same distribution as this module. You can also explicitly
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specify to use L<Cpanel::JSON::XS>, a fork of JSON::XS by Reini Urban.
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All these backend modules have slight incompatibilities between them,
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including extra features that other modules don't support, but as long as you
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use only common features (most important ones are described below), migration
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from backend to backend should be reasonably easy. For details, see each
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backend module you use.
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=head1 CHOOSING BACKEND
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This module respects an environmental variable called C<PERL_JSON_BACKEND>
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when it decides a backend module to use. If this environmental variable is
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not set, it tries to load JSON::XS, and if JSON::XS is not available, it
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falls back on JSON::PP, and then JSON::backportPP if JSON::PP is not available
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either.
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If you always don't want it to fall back on pure perl modules, set the
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variable like this (C<export> may be C<setenv>, C<set> and the likes,
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depending on your environment):
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  > export PERL_JSON_BACKEND=JSON::XS
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If you prefer Cpanel::JSON::XS to JSON::XS, then:
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  > export PERL_JSON_BACKEND=Cpanel::JSON::XS,JSON::XS,JSON::PP
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You may also want to set this variable at the top of your test files, in order
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not to be bothered with incompatibilities between backends (you need to wrap
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this in C<BEGIN>, and set before actually C<use>-ing JSON module, as it decides
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its backend as soon as it's loaded):
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  BEGIN { $ENV{PERL_JSON_BACKEND}='JSON::backportPP'; }
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  use JSON;
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=head1 USING OPTIONAL FEATURES
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There are a few options you can set when you C<use> this module:
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=over
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=item -support_by_pp
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   BEGIN { $ENV{PERL_JSON_BACKEND} = 'JSON::XS' }
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   use JSON -support_by_pp;
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   my $json = JSON->new;
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   # escape_slash is for JSON::PP only.
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   $json->allow_nonref->escape_slash->encode("/");
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With this option, this module loads its pure perl backend along with
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its XS backend (if available), and lets the XS backend to watch if you set
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a flag only JSON::PP supports. When you do, the internal JSON::XS object
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is replaced with a newly created JSON::PP object with the setting copied
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from the XS object, so that you can use JSON::PP flags (and its slower
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C<decode>/C<encode> methods) from then on. In other words, this is not
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something that allows you to hook JSON::XS to change its behavior while
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keeping its speed. JSON::XS and JSON::PP objects are quite different
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(JSON::XS object is a blessed scalar reference, while JSON::PP object is
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a blessed hash reference), and can't share their internals.
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To avoid needless overhead (by copying settings), you are advised not
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to use this option and just to use JSON::PP explicitly when you need
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JSON::PP features.
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=item -convert_blessed_universally
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   use JSON -convert_blessed_universally;
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   my $json = JSON->new->allow_nonref->convert_blessed;
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   my $object = bless {foo => 'bar'}, 'Foo';
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   $json->encode($object); # => {"foo":"bar"}
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JSON::XS-compatible backend modules don't encode blessed objects by
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default (except for their boolean values, which are typically blessed
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JSON::PP::Boolean objects). If you need to encode a data structure
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that may contain objects, you usually need to look into the structure
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and replace objects with alternative non-blessed values, or enable
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C<convert_blessed> and provide a C<TO_JSON> method for each object's
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(base) class that may be found in the structure, in order to let the
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methods replace the objects with whatever scalar values the methods
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return.
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If you need to serialise data structures that may contain arbitrary
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objects, it's probably better to use other serialisers (such as
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L<Sereal> or L<Storable> for example), but if you do want to use
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this module for that purpose, C<-convert_blessed_universally> option
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may help, which tweaks C<encode> method of the backend to install
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C<UNIVERSAL::TO_JSON> method (locally) before encoding, so that
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all the objects that don't have their own C<TO_JSON> method can
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fall back on the method in the C<UNIVERSAL> namespace. Note that you
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still need to enable C<convert_blessed> flag to actually encode
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objects in a data structure, and C<UNIVERSAL::TO_JSON> method
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installed by this option only converts blessed hash/array references
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into their unblessed clone (including private keys/values that are
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not supposed to be exposed). Other blessed references will be
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converted into null.
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This feature is experimental and may be removed in the future.
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=item -no_export
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When you don't want to import functional interfaces from a module, you
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usually supply C<()> to its C<use> statement.
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    use JSON (); # no functional interfaces
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If you don't want to import functional interfaces, but you also want to
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use any of the above options, add C<-no_export> to the option list.
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   # no functional interfaces, while JSON::PP support is enabled.
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   use JSON -support_by_pp, -no_export;
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=back
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=head1 FUNCTIONAL INTERFACE
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This section is taken from JSON::XS. C<encode_json> and C<decode_json>
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are exported by default.
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This module also exports C<to_json> and C<from_json> for backward
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compatibility. These are slower, and may expect/generate different stuff
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from what C<encode_json> and C<decode_json> do, depending on their
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options. It's better just to use Object-Oriented interfaces than using
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these two functions.
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=head2 encode_json
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    $json_text = encode_json $perl_scalar
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Converts the given Perl data structure to a UTF-8 encoded, binary string
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(that is, the string contains octets only). Croaks on error.
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This function call is functionally identical to:
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    $json_text = JSON->new->utf8->encode($perl_scalar)
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Except being faster.
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=head2 decode_json
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    $perl_scalar = decode_json $json_text
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The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
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to parse that as an UTF-8 encoded JSON text, returning the resulting
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reference. Croaks on error.
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This function call is functionally identical to:
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    $perl_scalar = JSON->new->utf8->decode($json_text)
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Except being faster.
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=head2 to_json
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   $json_text = to_json($perl_scalar[, $optional_hashref])
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Converts the given Perl data structure to a Unicode string by default.
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Croaks on error.
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Basically, this function call is functionally identical to:
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   $json_text = JSON->new->encode($perl_scalar)
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Except being slower.
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You can pass an optional hash reference to modify its behavior, but
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that may change what C<to_json> expects/generates (see
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C<ENCODING/CODESET FLAG NOTES> for details).
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   $json_text = to_json($perl_scalar, {utf8 => 1, pretty => 1})
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   # => JSON->new->utf8(1)->pretty(1)->encode($perl_scalar)
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=head2 from_json
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   $perl_scalar = from_json($json_text[, $optional_hashref])
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The opposite of C<to_json>: expects a Unicode string and tries
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to parse it, returning the resulting reference. Croaks on error.
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Basically, this function call is functionally identical to:
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    $perl_scalar = JSON->new->decode($json_text)
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You can pass an optional hash reference to modify its behavior, but
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that may change what C<from_json> expects/generates (see
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C<ENCODING/CODESET FLAG NOTES> for details).
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    $perl_scalar = from_json($json_text, {utf8 => 1})
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    # => JSON->new->utf8(1)->decode($json_text)
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=head2 JSON::is_bool
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    $is_boolean = JSON::is_bool($scalar)
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Returns true if the passed scalar represents either JSON::true or
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JSON::false, two constants that act like C<1> and C<0> respectively
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and are also used to represent JSON C<true> and C<false> in Perl strings.
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See L<MAPPING>, below, for more information on how JSON values are mapped to
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Perl.
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=head1 COMMON OBJECT-ORIENTED INTERFACE
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This section is also taken from JSON::XS.
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The object oriented interface lets you configure your own encoding or
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decoding style, within the limits of supported formats.
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=head2 new
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    $json = JSON->new
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Creates a new JSON::XS-compatible backend object that can be used to de/encode JSON
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strings. All boolean flags described below are by default I<disabled>.
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The mutators for flags all return the backend object again and thus calls can
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be chained:
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   my $json = JSON->new->utf8->space_after->encode({a => [1,2]})
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   => {"a": [1, 2]}
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=head2 ascii
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    $json = $json->ascii([$enable])
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    $enabled = $json->get_ascii
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If C<$enable> is true (or missing), then the C<encode> method will not
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generate characters outside the code range C<0..127> (which is ASCII). Any
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Unicode characters outside that range will be escaped using either a
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single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
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as per RFC4627. The resulting encoded JSON text can be treated as a native
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Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
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or any other superset of ASCII.
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If C<$enable> is false, then the C<encode> method will not escape Unicode
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characters unless required by the JSON syntax or other flags. This results
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in a faster and more compact format.
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See also the section I<ENCODING/CODESET FLAG NOTES> later in this document.
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The main use for this flag is to produce JSON texts that can be
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transmitted over a 7-bit channel, as the encoded JSON texts will not
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contain any 8 bit characters.
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Packit a557cb
  JSON->new->ascii(1)->encode([chr 0x10401])
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  => ["\ud801\udc01"]
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=head2 latin1
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    $json = $json->latin1([$enable])
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    $enabled = $json->get_latin1
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If C<$enable> is true (or missing), then the C<encode> method will encode
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the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
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outside the code range C<0..255>. The resulting string can be treated as a
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latin1-encoded JSON text or a native Unicode string. The C<decode> method
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will not be affected in any way by this flag, as C<decode> by default
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expects Unicode, which is a strict superset of latin1.
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If C<$enable> is false, then the C<encode> method will not escape Unicode
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characters unless required by the JSON syntax or other flags.
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See also the section I<ENCODING/CODESET FLAG NOTES> later in this document.
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The main use for this flag is efficiently encoding binary data as JSON
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text, as most octets will not be escaped, resulting in a smaller encoded
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size. The disadvantage is that the resulting JSON text is encoded
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in latin1 (and must correctly be treated as such when storing and
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transferring), a rare encoding for JSON. It is therefore most useful when
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you want to store data structures known to contain binary data efficiently
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in files or databases, not when talking to other JSON encoders/decoders.
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Packit a557cb
  JSON->new->latin1->encode (["\x{89}\x{abc}"]
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  => ["\x{89}\\u0abc"]    # (perl syntax, U+abc escaped, U+89 not)
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=head2 utf8
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    $json = $json->utf8([$enable])
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    $enabled = $json->get_utf8
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If C<$enable> is true (or missing), then the C<encode> method will encode
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the JSON result into UTF-8, as required by many protocols, while the
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C<decode> method expects to be handled an UTF-8-encoded string.  Please
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note that UTF-8-encoded strings do not contain any characters outside the
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range C<0..255>, they are thus useful for bytewise/binary I/O. In future
Packit a557cb
versions, enabling this option might enable autodetection of the UTF-16
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and UTF-32 encoding families, as described in RFC4627.
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If C<$enable> is false, then the C<encode> method will return the JSON
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string as a (non-encoded) Unicode string, while C<decode> expects thus a
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Unicode string.  Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
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to be done yourself, e.g. using the Encode module.
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Packit a557cb
See also the section I<ENCODING/CODESET FLAG NOTES> later in this document.
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Packit a557cb
Example, output UTF-16BE-encoded JSON:
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Packit a557cb
  use Encode;
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  $jsontext = encode "UTF-16BE", JSON->new->encode ($object);
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Packit a557cb
Example, decode UTF-32LE-encoded JSON:
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Packit a557cb
  use Encode;
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  $object = JSON->new->decode (decode "UTF-32LE", $jsontext);
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Packit a557cb
=head2 pretty
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Packit a557cb
    $json = $json->pretty([$enable])
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This enables (or disables) all of the C<indent>, C<space_before> and
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C<space_after> (and in the future possibly more) flags in one call to
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generate the most readable (or most compact) form possible.
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=head2 indent
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Packit a557cb
    $json = $json->indent([$enable])
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Packit a557cb
    $enabled = $json->get_indent
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If C<$enable> is true (or missing), then the C<encode> method will use a multiline
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format as output, putting every array member or object/hash key-value pair
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into its own line, indenting them properly.
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If C<$enable> is false, no newlines or indenting will be produced, and the
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resulting JSON text is guaranteed not to contain any C<newlines>.
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This setting has no effect when decoding JSON texts.
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Packit a557cb
=head2 space_before
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Packit a557cb
    $json = $json->space_before([$enable])
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Packit a557cb
    $enabled = $json->get_space_before
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Packit a557cb
If C<$enable> is true (or missing), then the C<encode> method will add an extra
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optional space before the C<:> separating keys from values in JSON objects.
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Packit a557cb
If C<$enable> is false, then the C<encode> method will not add any extra
Packit a557cb
space at those places.
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Packit a557cb
This setting has no effect when decoding JSON texts. You will also
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most likely combine this setting with C<space_after>.
Packit a557cb
Packit a557cb
Example, space_before enabled, space_after and indent disabled:
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Packit a557cb
   {"key" :"value"}
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Packit a557cb
=head2 space_after
Packit a557cb
Packit a557cb
    $json = $json->space_after([$enable])
Packit a557cb
    
Packit a557cb
    $enabled = $json->get_space_after
Packit a557cb
Packit a557cb
If C<$enable> is true (or missing), then the C<encode> method will add an extra
Packit a557cb
optional space after the C<:> separating keys from values in JSON objects
Packit a557cb
and extra whitespace after the C<,> separating key-value pairs and array
Packit a557cb
members.
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Packit a557cb
If C<$enable> is false, then the C<encode> method will not add any extra
Packit a557cb
space at those places.
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Packit a557cb
This setting has no effect when decoding JSON texts.
Packit a557cb
Packit a557cb
Example, space_before and indent disabled, space_after enabled:
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Packit a557cb
   {"key": "value"}
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Packit a557cb
=head2 relaxed
Packit a557cb
Packit a557cb
    $json = $json->relaxed([$enable])
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Packit a557cb
    $enabled = $json->get_relaxed
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Packit a557cb
If C<$enable> is true (or missing), then C<decode> will accept some
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extensions to normal JSON syntax (see below). C<encode> will not be
Packit a557cb
affected in anyway. I
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JSON texts as if they were valid!>. I suggest only to use this option to
Packit a557cb
parse application-specific files written by humans (configuration files,
Packit a557cb
resource files etc.)
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Packit a557cb
If C<$enable> is false (the default), then C<decode> will only accept
Packit a557cb
valid JSON texts.
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Packit a557cb
Currently accepted extensions are:
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Packit a557cb
=over 4
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Packit a557cb
=item * list items can have an end-comma
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Packit a557cb
JSON I<separates> array elements and key-value pairs with commas. This
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can be annoying if you write JSON texts manually and want to be able to
Packit a557cb
quickly append elements, so this extension accepts comma at the end of
Packit a557cb
such items not just between them:
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Packit a557cb
   [
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      1,
Packit a557cb
      2, <- this comma not normally allowed
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   ]
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   {
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      "k1": "v1",
Packit a557cb
      "k2": "v2", <- this comma not normally allowed
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   }
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Packit a557cb
=item * shell-style '#'-comments
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Packit a557cb
Whenever JSON allows whitespace, shell-style comments are additionally
Packit a557cb
allowed. They are terminated by the first carriage-return or line-feed
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character, after which more white-space and comments are allowed.
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Packit a557cb
  [
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     1, # this comment not allowed in JSON
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        # neither this one...
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  ]
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Packit a557cb
=back
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Packit a557cb
=head2 canonical
Packit a557cb
Packit a557cb
    $json = $json->canonical([$enable])
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Packit a557cb
    $enabled = $json->get_canonical
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Packit a557cb
If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
Packit a557cb
by sorting their keys. This is adding a comparatively high overhead.
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Packit a557cb
If C<$enable> is false, then the C<encode> method will output key-value
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pairs in the order Perl stores them (which will likely change between runs
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of the same script, and can change even within the same run from 5.18
Packit a557cb
onwards).
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Packit a557cb
This option is useful if you want the same data structure to be encoded as
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the same JSON text (given the same overall settings). If it is disabled,
Packit a557cb
the same hash might be encoded differently even if contains the same data,
Packit a557cb
as key-value pairs have no inherent ordering in Perl.
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Packit a557cb
This setting has no effect when decoding JSON texts.
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Packit a557cb
This setting has currently no effect on tied hashes.
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Packit a557cb
=head2 allow_nonref
Packit a557cb
Packit a557cb
    $json = $json->allow_nonref([$enable])
Packit a557cb
    
Packit a557cb
    $enabled = $json->get_allow_nonref
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If C<$enable> is true (or missing), then the C<encode> method can convert a
Packit a557cb
non-reference into its corresponding string, number or null JSON value,
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which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
Packit a557cb
values instead of croaking.
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Packit a557cb
If C<$enable> is false, then the C<encode> method will croak if it isn't
Packit a557cb
passed an arrayref or hashref, as JSON texts must either be an object
Packit a557cb
or array. Likewise, C<decode> will croak if given something that is not a
Packit a557cb
JSON object or array.
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Packit a557cb
Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
Packit a557cb
resulting in an invalid JSON text:
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Packit a557cb
   JSON->new->allow_nonref->encode ("Hello, World!")
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   => "Hello, World!"
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Packit a557cb
=head2 allow_unknown
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Packit a557cb
    $json = $json->allow_unknown ([$enable])
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Packit a557cb
    $enabled = $json->get_allow_unknown
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Packit a557cb
If C<$enable> is true (or missing), then C<encode> will I<not> throw an
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exception when it encounters values it cannot represent in JSON (for
Packit a557cb
example, filehandles) but instead will encode a JSON C<null> value. Note
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that blessed objects are not included here and are handled separately by
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c<allow_nonref>.
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Packit a557cb
If C<$enable> is false (the default), then C<encode> will throw an
Packit a557cb
exception when it encounters anything it cannot encode as JSON.
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Packit a557cb
This option does not affect C<decode> in any way, and it is recommended to
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leave it off unless you know your communications partner.
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Packit a557cb
=head2 allow_blessed
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Packit a557cb
    $json = $json->allow_blessed([$enable])
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Packit a557cb
    $enabled = $json->get_allow_blessed
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Packit a557cb
See L<OBJECT SERIALISATION> for details.
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Packit a557cb
If C<$enable> is true (or missing), then the C<encode> method will not
Packit a557cb
barf when it encounters a blessed reference that it cannot convert
Packit a557cb
otherwise. Instead, a JSON C<null> value is encoded instead of the object.
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Packit a557cb
If C<$enable> is false (the default), then C<encode> will throw an
Packit a557cb
exception when it encounters a blessed object that it cannot convert
Packit a557cb
otherwise.
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Packit a557cb
This setting has no effect on C<decode>.
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=head2 convert_blessed
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    $json = $json->convert_blessed([$enable])
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    $enabled = $json->get_convert_blessed
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See L<OBJECT SERIALISATION> for details.
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If C<$enable> is true (or missing), then C<encode>, upon encountering a
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blessed object, will check for the availability of the C<TO_JSON> method
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on the object's class. If found, it will be called in scalar context and
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the resulting scalar will be encoded instead of the object.
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The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
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returns other blessed objects, those will be handled in the same
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way. C<TO_JSON> must take care of not causing an endless recursion cycle
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(== crash) in this case. The name of C<TO_JSON> was chosen because other
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methods called by the Perl core (== not by the user of the object) are
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usually in upper case letters and to avoid collisions with any C<to_json>
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function or method.
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If C<$enable> is false (the default), then C<encode> will not consider
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this type of conversion.
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This setting has no effect on C<decode>.
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=head2 filter_json_object
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    $json = $json->filter_json_object([$coderef])
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When C<$coderef> is specified, it will be called from C<decode> each
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time it decodes a JSON object. The only argument is a reference to the
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newly-created hash. If the code references returns a single scalar (which
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need not be a reference), this value (i.e. a copy of that scalar to avoid
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aliasing) is inserted into the deserialised data structure. If it returns
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an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
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original deserialised hash will be inserted. This setting can slow down
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decoding considerably.
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When C<$coderef> is omitted or undefined, any existing callback will
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be removed and C<decode> will not change the deserialised hash in any
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way.
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Example, convert all JSON objects into the integer 5:
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   my $js = JSON->new->filter_json_object (sub { 5 });
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   # returns [5]
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   $js->decode ('[{}]'); # the given subroutine takes a hash reference.
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   # throw an exception because allow_nonref is not enabled
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   # so a lone 5 is not allowed.
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   $js->decode ('{"a":1, "b":2}');
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=head2 filter_json_single_key_object
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    $json = $json->filter_json_single_key_object($key [=> $coderef])
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Works remotely similar to C<filter_json_object>, but is only called for
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JSON objects having a single key named C<$key>.
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This C<$coderef> is called before the one specified via
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C<filter_json_object>, if any. It gets passed the single value in the JSON
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object. If it returns a single value, it will be inserted into the data
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structure. If it returns nothing (not even C<undef> but the empty list),
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the callback from C<filter_json_object> will be called next, as if no
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single-key callback were specified.
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If C<$coderef> is omitted or undefined, the corresponding callback will be
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disabled. There can only ever be one callback for a given key.
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As this callback gets called less often then the C<filter_json_object>
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one, decoding speed will not usually suffer as much. Therefore, single-key
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objects make excellent targets to serialise Perl objects into, especially
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as single-key JSON objects are as close to the type-tagged value concept
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as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
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support this in any way, so you need to make sure your data never looks
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like a serialised Perl hash.
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Typical names for the single object key are C<__class_whatever__>, or
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C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
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things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
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with real hashes.
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Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
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into the corresponding C<< $WIDGET{<id>} >> object:
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   # return whatever is in $WIDGET{5}:
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   JSON
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      ->new
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      ->filter_json_single_key_object (__widget__ => sub {
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            $WIDGET{ $_[0] }
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         })
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      ->decode ('{"__widget__": 5')
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   # this can be used with a TO_JSON method in some "widget" class
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   # for serialisation to json:
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   sub WidgetBase::TO_JSON {
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      my ($self) = @_;
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      unless ($self->{id}) {
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         $self->{id} = ..get..some..id..;
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         $WIDGET{$self->{id}} = $self;
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      }
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      { __widget__ => $self->{id} }
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   }
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=head2 max_depth
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    $json = $json->max_depth([$maximum_nesting_depth])
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    $max_depth = $json->get_max_depth
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Sets the maximum nesting level (default C<512>) accepted while encoding
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or decoding. If a higher nesting level is detected in JSON text or a Perl
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data structure, then the encoder and decoder will stop and croak at that
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point.
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Nesting level is defined by number of hash- or arrayrefs that the encoder
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needs to traverse to reach a given point or the number of C<{> or C<[>
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characters without their matching closing parenthesis crossed to reach a
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given character in a string.
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Setting the maximum depth to one disallows any nesting, so that ensures
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that the object is only a single hash/object or array.
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If no argument is given, the highest possible setting will be used, which
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is rarely useful.
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=head2 max_size
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    $json = $json->max_size([$maximum_string_size])
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    $max_size = $json->get_max_size
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Set the maximum length a JSON text may have (in bytes) where decoding is
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being attempted. The default is C<0>, meaning no limit. When C<decode>
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is called on a string that is longer then this many bytes, it will not
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attempt to decode the string but throw an exception. This setting has no
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effect on C<encode> (yet).
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If no argument is given, the limit check will be deactivated (same as when
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C<0> is specified).
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=head2 encode
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    $json_text = $json->encode($perl_scalar)
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Converts the given Perl value or data structure to its JSON
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representation. Croaks on error.
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=head2 decode
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    $perl_scalar = $json->decode($json_text)
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The opposite of C<encode>: expects a JSON text and tries to parse it,
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returning the resulting simple scalar or reference. Croaks on error.
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=head2 decode_prefix
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    ($perl_scalar, $characters) = $json->decode_prefix($json_text)
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This works like the C<decode> method, but instead of raising an exception
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when there is trailing garbage after the first JSON object, it will
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silently stop parsing there and return the number of characters consumed
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so far.
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This is useful if your JSON texts are not delimited by an outer protocol
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and you need to know where the JSON text ends.
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   JSON->new->decode_prefix ("[1] the tail")
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   => ([1], 3)
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=head1 ADDITIONAL METHODS
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The following methods are for this module only.
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=head2 backend
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    $backend = $json->backend
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Since 2.92, C<backend> method returns an abstract backend module used currently,
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which should be JSON::Backend::XS (which inherits JSON::XS or Cpanel::JSON::XS),
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or JSON::Backend::PP (which inherits JSON::PP), not to monkey-patch the actual
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backend module globally.
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If you need to know what is used actually, use C<isa>, instead of string comparison.
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=head2 is_xs
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    $boolean = $json->is_xs
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Returns true if the backend inherits JSON::XS or Cpanel::JSON::XS.
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=head2 is_pp
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    $boolean = $json->is_pp
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Returns true if the backend inherits JSON::PP.
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=head2 property
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    $settings = $json->property()
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Returns a reference to a hash that holds all the common flag settings.
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    $json = $json->property('utf8' => 1)
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    $value = $json->property('utf8') # 1
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You can use this to get/set a value of a particular flag.
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=head1 INCREMENTAL PARSING
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This section is also taken from JSON::XS.
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In some cases, there is the need for incremental parsing of JSON
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texts. While this module always has to keep both JSON text and resulting
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Perl data structure in memory at one time, it does allow you to parse a
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JSON stream incrementally. It does so by accumulating text until it has
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a full JSON object, which it then can decode. This process is similar to
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using C<decode_prefix> to see if a full JSON object is available, but
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is much more efficient (and can be implemented with a minimum of method
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calls).
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This module will only attempt to parse the JSON text once it is sure it
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has enough text to get a decisive result, using a very simple but
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truly incremental parser. This means that it sometimes won't stop as
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early as the full parser, for example, it doesn't detect mismatched
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parentheses. The only thing it guarantees is that it starts decoding as
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soon as a syntactically valid JSON text has been seen. This means you need
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to set resource limits (e.g. C<max_size>) to ensure the parser will stop
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parsing in the presence if syntax errors.
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The following methods implement this incremental parser.
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=head2 incr_parse
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    $json->incr_parse( [$string] ) # void context
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    $obj_or_undef = $json->incr_parse( [$string] ) # scalar context
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    @obj_or_empty = $json->incr_parse( [$string] ) # list context
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This is the central parsing function. It can both append new text and
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extract objects from the stream accumulated so far (both of these
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functions are optional).
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If C<$string> is given, then this string is appended to the already
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existing JSON fragment stored in the C<$json> object.
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After that, if the function is called in void context, it will simply
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return without doing anything further. This can be used to add more text
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in as many chunks as you want.
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If the method is called in scalar context, then it will try to extract
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exactly I<one> JSON object. If that is successful, it will return this
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object, otherwise it will return C<undef>. If there is a parse error,
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this method will croak just as C<decode> would do (one can then use
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C<incr_skip> to skip the erroneous part). This is the most common way of
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using the method.
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And finally, in list context, it will try to extract as many objects
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from the stream as it can find and return them, or the empty list
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otherwise. For this to work, there must be no separators (other than
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whitespace) between the JSON objects or arrays, instead they must be
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concatenated back-to-back. If an error occurs, an exception will be
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raised as in the scalar context case. Note that in this case, any
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previously-parsed JSON texts will be lost.
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Example: Parse some JSON arrays/objects in a given string and return
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them.
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    my @objs = JSON->new->incr_parse ("[5][7][1,2]");
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=head2 incr_text
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Packit a557cb
    $lvalue_string = $json->incr_text
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This method returns the currently stored JSON fragment as an lvalue, that
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is, you can manipulate it. This I<only> works when a preceding call to
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C<incr_parse> in I<scalar context> successfully returned an object. Under
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all other circumstances you must not call this function (I mean it.
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although in simple tests it might actually work, it I<will> fail under
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real world conditions). As a special exception, you can also call this
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method before having parsed anything.
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That means you can only use this function to look at or manipulate text
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before or after complete JSON objects, not while the parser is in the
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middle of parsing a JSON object.
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This function is useful in two cases: a) finding the trailing text after a
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JSON object or b) parsing multiple JSON objects separated by non-JSON text
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(such as commas).
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=head2 incr_skip
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    $json->incr_skip
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This will reset the state of the incremental parser and will remove
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the parsed text from the input buffer so far. This is useful after
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C<incr_parse> died, in which case the input buffer and incremental parser
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state is left unchanged, to skip the text parsed so far and to reset the
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parse state.
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The difference to C<incr_reset> is that only text until the parse error
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occurred is removed.
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Packit a557cb
=head2 incr_reset
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Packit a557cb
    $json->incr_reset
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Packit a557cb
This completely resets the incremental parser, that is, after this call,
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it will be as if the parser had never parsed anything.
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Packit a557cb
This is useful if you want to repeatedly parse JSON objects and want to
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ignore any trailing data, which means you have to reset the parser after
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each successful decode.
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=head1 MAPPING
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Packit a557cb
Most of this section is also taken from JSON::XS.
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Packit a557cb
This section describes how the backend modules map Perl values to JSON values and
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vice versa. These mappings are designed to "do the right thing" in most
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circumstances automatically, preserving round-tripping characteristics
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(what you put in comes out as something equivalent).
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For the more enlightened: note that in the following descriptions,
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lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
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refers to the abstract Perl language itself.
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=head2 JSON -> PERL
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=over 4
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=item object
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A JSON object becomes a reference to a hash in Perl. No ordering of object
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keys is preserved (JSON does not preserver object key ordering itself).
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=item array
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A JSON array becomes a reference to an array in Perl.
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=item string
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A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
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are represented by the same codepoints in the Perl string, so no manual
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decoding is necessary.
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=item number
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A JSON number becomes either an integer, numeric (floating point) or
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string scalar in perl, depending on its range and any fractional parts. On
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the Perl level, there is no difference between those as Perl handles all
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the conversion details, but an integer may take slightly less memory and
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might represent more values exactly than floating point numbers.
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If the number consists of digits only, this module will try to represent
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it as an integer value. If that fails, it will try to represent it as
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a numeric (floating point) value if that is possible without loss of
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precision. Otherwise it will preserve the number as a string value (in
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which case you lose roundtripping ability, as the JSON number will be
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re-encoded to a JSON string).
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Packit a557cb
Numbers containing a fractional or exponential part will always be
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represented as numeric (floating point) values, possibly at a loss of
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precision (in which case you might lose perfect roundtripping ability, but
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the JSON number will still be re-encoded as a JSON number).
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Packit a557cb
Note that precision is not accuracy - binary floating point values cannot
Packit a557cb
represent most decimal fractions exactly, and when converting from and to
Packit a557cb
floating point, this module only guarantees precision up to but not including
Packit a557cb
the least significant bit.
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Packit a557cb
=item true, false
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These JSON atoms become C<JSON::true> and C<JSON::false>,
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respectively. They are overloaded to act almost exactly like the numbers
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C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
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the C<JSON::is_bool> function.
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=item null
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Packit a557cb
A JSON null atom becomes C<undef> in Perl.
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=item shell-style comments (C<< # I<text> >>)
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As a nonstandard extension to the JSON syntax that is enabled by the
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C<relaxed> setting, shell-style comments are allowed. They can start
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anywhere outside strings and go till the end of the line.
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Packit a557cb
=back
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=head2 PERL -> JSON
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The mapping from Perl to JSON is slightly more difficult, as Perl is a
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truly typeless language, so we can only guess which JSON type is meant by
Packit a557cb
a Perl value.
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Packit a557cb
=over 4
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Packit a557cb
=item hash references
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Packit a557cb
Perl hash references become JSON objects. As there is no inherent
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ordering in hash keys (or JSON objects), they will usually be encoded
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in a pseudo-random order. This module can optionally sort the hash keys
Packit a557cb
(determined by the I<canonical> flag), so the same data structure will
Packit a557cb
serialise to the same JSON text (given same settings and version of
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the same backend), but this incurs a runtime overhead and is only rarely useful,
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e.g. when you want to compare some JSON text against another for equality.
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Packit a557cb
=item array references
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Perl array references become JSON arrays.
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=item other references
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Packit a557cb
Other unblessed references are generally not allowed and will cause an
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exception to be thrown, except for references to the integers C<0> and
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C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
Packit a557cb
also use C<JSON::false> and C<JSON::true> to improve readability.
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Packit a557cb
   encode_json [\0,JSON::true]      # yields [false,true]
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=item JSON::true, JSON::false, JSON::null
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Packit a557cb
These special values become JSON true and JSON false values,
Packit a557cb
respectively. You can also use C<\1> and C<\0> directly if you want.
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Packit a557cb
=item blessed objects
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Blessed objects are not directly representable in JSON, but C<JSON::XS>
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allows various ways of handling objects. See L<OBJECT SERIALISATION>,
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below, for details.
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=item simple scalars
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Simple Perl scalars (any scalar that is not a reference) are the most
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difficult objects to encode: this module will encode undefined scalars as
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JSON C<null> values, scalars that have last been used in a string context
Packit a557cb
before encoding as JSON strings, and anything else as number value:
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Packit a557cb
   # dump as number
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   encode_json [2]                      # yields [2]
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   encode_json [-3.0e17]                # yields [-3e+17]
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   my $value = 5; encode_json [$value]  # yields [5]
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Packit a557cb
   # used as string, so dump as string
Packit a557cb
   print $value;
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   encode_json [$value]                 # yields ["5"]
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Packit a557cb
   # undef becomes null
Packit a557cb
   encode_json [undef]                  # yields [null]
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Packit a557cb
You can force the type to be a string by stringifying it:
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Packit a557cb
   my $x = 3.1; # some variable containing a number
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   "$x";        # stringified
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   $x .= "";    # another, more awkward way to stringify
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   print $x;    # perl does it for you, too, quite often
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Packit a557cb
You can force the type to be a number by numifying it:
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Packit a557cb
   my $x = "3"; # some variable containing a string
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   $x += 0;     # numify it, ensuring it will be dumped as a number
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   $x *= 1;     # same thing, the choice is yours.
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Packit a557cb
You can not currently force the type in other, less obscure, ways. Tell me
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if you need this capability (but don't forget to explain why it's needed
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:).
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Note that numerical precision has the same meaning as under Perl (so
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binary to decimal conversion follows the same rules as in Perl, which
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can differ to other languages). Also, your perl interpreter might expose
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extensions to the floating point numbers of your platform, such as
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infinities or NaN's - these cannot be represented in JSON, and it is an
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error to pass those in.
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=back
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=head2 OBJECT SERIALISATION
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As for Perl objects, this module only supports a pure JSON representation
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(without the ability to deserialise the object automatically again).
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=head3 SERIALISATION
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What happens when this module encounters a Perl object depends on the
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C<allow_blessed> and C<convert_blessed> settings, which are used in
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this order:
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=over 4
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=item 1. C<convert_blessed> is enabled and the object has a C<TO_JSON> method.
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In this case, the C<TO_JSON> method of the object is invoked in scalar
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context. It must return a single scalar that can be directly encoded into
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JSON. This scalar replaces the object in the JSON text.
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For example, the following C<TO_JSON> method will convert all L<URI>
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objects to JSON strings when serialised. The fact that these values
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originally were L<URI> objects is lost.
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   sub URI::TO_JSON {
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      my ($uri) = @_;
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      $uri->as_string
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   }
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=item 2. C<allow_blessed> is enabled.
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The object will be serialised as a JSON null value.
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=item 3. none of the above
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If none of the settings are enabled or the respective methods are missing,
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this module throws an exception.
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=back
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=head1 ENCODING/CODESET FLAG NOTES
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This section is taken from JSON::XS.
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The interested reader might have seen a number of flags that signify
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encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
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some confusion on what these do, so here is a short comparison:
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C<utf8> controls whether the JSON text created by C<encode> (and expected
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by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
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control whether C<encode> escapes character values outside their respective
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codeset range. Neither of these flags conflict with each other, although
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some combinations make less sense than others.
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Care has been taken to make all flags symmetrical with respect to
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C<encode> and C<decode>, that is, texts encoded with any combination of
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these flag values will be correctly decoded when the same flags are used
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- in general, if you use different flag settings while encoding vs. when
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decoding you likely have a bug somewhere.
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Below comes a verbose discussion of these flags. Note that a "codeset" is
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simply an abstract set of character-codepoint pairs, while an encoding
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takes those codepoint numbers and I<encodes> them, in our case into
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octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
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and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
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the same time, which can be confusing.
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=over 4
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=item C<utf8> flag disabled
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When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
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and expect Unicode strings, that is, characters with high ordinal Unicode
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values (> 255) will be encoded as such characters, and likewise such
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characters are decoded as-is, no changes to them will be done, except
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"(re-)interpreting" them as Unicode codepoints or Unicode characters,
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respectively (to Perl, these are the same thing in strings unless you do
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funny/weird/dumb stuff).
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This is useful when you want to do the encoding yourself (e.g. when you
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want to have UTF-16 encoded JSON texts) or when some other layer does
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the encoding for you (for example, when printing to a terminal using a
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filehandle that transparently encodes to UTF-8 you certainly do NOT want
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to UTF-8 encode your data first and have Perl encode it another time).
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=item C<utf8> flag enabled
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If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
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characters using the corresponding UTF-8 multi-byte sequence, and will
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expect your input strings to be encoded as UTF-8, that is, no "character"
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of the input string must have any value > 255, as UTF-8 does not allow
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that.
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The C<utf8> flag therefore switches between two modes: disabled means you
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will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
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octet/binary string in Perl.
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=item C<latin1> or C<ascii> flags enabled
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With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
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with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
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characters as specified by the C<utf8> flag.
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If C<utf8> is disabled, then the result is also correctly encoded in those
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character sets (as both are proper subsets of Unicode, meaning that a
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Unicode string with all character values < 256 is the same thing as a
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ISO-8859-1 string, and a Unicode string with all character values < 128 is
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the same thing as an ASCII string in Perl).
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If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
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regardless of these flags, just some more characters will be escaped using
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C<\uXXXX> then before.
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Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
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encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
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encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
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a subset of Unicode), while ASCII is.
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Surprisingly, C<decode> will ignore these flags and so treat all input
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values as governed by the C<utf8> flag. If it is disabled, this allows you
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to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
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Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
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So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
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they only govern when the JSON output engine escapes a character or not.
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The main use for C<latin1> is to relatively efficiently store binary data
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as JSON, at the expense of breaking compatibility with most JSON decoders.
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The main use for C<ascii> is to force the output to not contain characters
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with values > 127, which means you can interpret the resulting string
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as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
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8-bit-encoding, and still get the same data structure back. This is useful
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when your channel for JSON transfer is not 8-bit clean or the encoding
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might be mangled in between (e.g. in mail), and works because ASCII is a
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proper subset of most 8-bit and multibyte encodings in use in the world.
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=back
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=head1 BACKWARD INCOMPATIBILITY
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Since version 2.90, stringification (and string comparison) for
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C<JSON::true> and C<JSON::false> has not been overloaded. It shouldn't
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matter as long as you treat them as boolean values, but a code that
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expects they are stringified as "true" or "false" doesn't work as
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you have expected any more.
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    if (JSON::true eq 'true') {  # now fails
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    print "The result is $JSON::true now."; # => The result is 1 now.
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And now these boolean values don't inherit JSON::Boolean, either.
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When you need to test a value is a JSON boolean value or not, use
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C<JSON::is_bool> function, instead of testing the value inherits
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a particular boolean class or not.
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=head1 BUGS
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Please report bugs on backend selection and additional features
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this module provides to RT or GitHub issues for this module:
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=over 4
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=item https://rt.cpan.org/Public/Dist/Display.html?Queue=JSON
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=item https://github.com/makamaka/JSON/issues
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=back
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Please report bugs and feature requests on decoding/encoding
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and boolean behaviors to the author of the backend module you
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are using.
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=head1 SEE ALSO
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L<JSON::XS>, L<Cpanel::JSON::XS>, L<JSON::PP> for backends.
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L<JSON::MaybeXS>, an alternative that prefers Cpanel::JSON::XS.
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C<RFC4627>(L<http://www.ietf.org/rfc/rfc4627.txt>)
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=head1 AUTHOR
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Makamaka Hannyaharamitu, E<lt>makamaka[at]cpan.orgE<gt>
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JSON::XS was written by  Marc Lehmann <schmorp[at]schmorp.de>
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The release of this new version owes to the courtesy of Marc Lehmann.
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=head1 COPYRIGHT AND LICENSE
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Copyright 2005-2013 by Makamaka Hannyaharamitu
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This library is free software; you can redistribute it and/or modify
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it under the same terms as Perl itself. 
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=cut
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