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From esp...@apache.org
Subject [2/2] incubator-hawq git commit: Revert "HAWQ-1062. Remove ASF incompatible Perl JSON module"
Date Tue, 20 Sep 2016 10:15:38 GMT
Revert "HAWQ-1062. Remove ASF incompatible Perl JSON module"

This reverts commit eb10af42dfd23e71e6d8d46e8bbc48b5593d90c4.


Project: http://git-wip-us.apache.org/repos/asf/incubator-hawq/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-hawq/commit/98f7e8e9
Tree: http://git-wip-us.apache.org/repos/asf/incubator-hawq/tree/98f7e8e9
Diff: http://git-wip-us.apache.org/repos/asf/incubator-hawq/diff/98f7e8e9

Branch: refs/heads/master
Commit: 98f7e8e93c944d87010b967e7f14d52215517e52
Parents: 08ed4bc
Author: Ed Espino <espino@apache.org>
Authored: Tue Sep 20 03:15:06 2016 -0700
Committer: Ed Espino <espino@apache.org>
Committed: Tue Sep 20 03:15:06 2016 -0700

----------------------------------------------------------------------
 LICENSE                                |    3 +
 licenses/LICENSE-json.txt              |  131 ++
 src/include/catalog/JSON.pm            | 2223 +++++++++++++++++++++++++++
 src/include/catalog/JSON/PP.pm         | 2191 ++++++++++++++++++++++++++
 src/include/catalog/JSON/PP/Boolean.pm |   26 +
 src/include/catalog/JSON/PP5005.pm     |  146 ++
 src/include/catalog/JSON/PP56.pm       |  198 +++
 src/include/catalog/JSON/PP58.pm       |   93 ++
 8 files changed, 5011 insertions(+)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/incubator-hawq/blob/98f7e8e9/LICENSE
----------------------------------------------------------------------
diff --git a/LICENSE b/LICENSE
index 02e1967..62a4872 100644
--- a/LICENSE
+++ b/LICENSE
@@ -383,6 +383,9 @@ Perl LICENSE
   license. See project link for details.  The text of each license is
   also included at licenses/LICENSE-[project].txt.
 
+     JSON 
+       src/include/catalog/JSON
+  
      plperl
        src/pl/plperl
       

http://git-wip-us.apache.org/repos/asf/incubator-hawq/blob/98f7e8e9/licenses/LICENSE-json.txt
----------------------------------------------------------------------
diff --git a/licenses/LICENSE-json.txt b/licenses/LICENSE-json.txt
new file mode 100644
index 0000000..71dd596
--- /dev/null
+++ b/licenses/LICENSE-json.txt
@@ -0,0 +1,131 @@
+Copyright 2007-2010 by Makamaka Hannyaharamitu
+
+The "Artistic License"
+
+Preamble
+
+The intent of this document is to state the conditions under which a
+Package may be copied, such that the Copyright Holder maintains some
+semblance of artistic control over the development of the package,
+while giving the users of the package the right to use and distribute
+the Package in a more-or-less customary fashion, plus the right to make
+reasonable modifications.
+
+Definitions:
+
+"Package" refers to the collection of files distributed by the
+Copyright Holder, and derivatives of that collection of files
+created through textual modification.
+
+"Standard Version" refers to such a Package if it has not been
+modified, or has been modified in accordance with the wishes
+of the Copyright Holder as specified below.
+
+"Copyright Holder" is whoever is named in the copyright or
+copyrights for the package.
+
+"You" is you, if you're thinking about copying or distributing
+this Package.
+
+"Reasonable copying fee" is whatever you can justify on the
+basis of media cost, duplication charges, time of people involved,
+and so on.  (You will not be required to justify it to the
+                 Copyright Holder, but only to the computing community at large
+                 as a market that must bear the fee.)
+
+"Freely Available" means that no fee is charged for the item
+itself, though there may be fees involved in handling the item.
+It also means that recipients of the item may redistribute it
+under the same conditions they received it.
+
+1. You may make and give away verbatim copies of the source form of the
+Standard Version of this Package without restriction, provided that you
+duplicate all of the original copyright notices and associated disclaimers.
+
+2. You may apply bug fixes, portability fixes and other modifications
+derived from the Public Domain or from the Copyright Holder.  A Package
+modified in such a way shall still be considered the Standard Version.
+
+3. You may otherwise modify your copy of this Package in any way, provided
+that you insert a prominent notice in each changed file stating how and
+when you changed that file, and provided that you do at least ONE of the
+following:
+
+a) place your modifications in the Public Domain or otherwise make them
+Freely Available, such as by posting said modifications to Usenet or
+an equivalent medium, or placing the modifications on a major archive
+site such as uunet.uu.net, or by allowing the Copyright Holder to include
+your modifications in the Standard Version of the Package.
+
+b) use the modified Package only within your corporation or organization.
+
+c) rename any non-standard executables so the names do not conflict
+with standard executables, which must also be provided, and provide
+a separate manual page for each non-standard executable that clearly
+documents how it differs from the Standard Version.
+
+d) make other distribution arrangements with the Copyright Holder.
+
+4. You may distribute the programs of this Package in object code or
+executable form, provided that you do at least ONE of the following:
+
+a) distribute a Standard Version of the executables and library files,
+together with instructions (in the manual page or equivalent) on where
+to get the Standard Version.
+
+b) accompany the distribution with the machine-readable source of
+the Package with your modifications.
+
+c) give non-standard executables non-standard names, and clearly
+document the differences in manual pages (or equivalent), together
+with instructions on where to get the Standard Version.
+
+d) make other distribution arrangements with the Copyright Holder.
+
+5. You may charge a reasonable copying fee for any distribution of this
+Package.  You may charge any fee you choose for support of this
+Package.  You may not charge a fee for this Package itself.  However,
+you may distribute this Package in aggregate with other (possibly
+commercial) programs as part of a larger (possibly commercial) software
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+form of aggregation, provided that the complete Standard Version of the
+interpreter is so embedded.
+
+6. The scripts and library files supplied as input to or produced as
+output from the programs of this Package do not automatically fall
+under the copyright of this Package, but belong to whoever generated
+them, and may be sold commercially, and may be aggregated with this
+Package.  If such scripts or library files are aggregated with this
+Package via the so-called "undump" or "unexec" methods of producing a
+binary executable image, then distribution of such an image shall
+neither be construed as a distribution of this Package nor shall it
+fall under the restrictions of Paragraphs 3 and 4, provided that you do
+not represent such an executable image as a Standard Version of this
+Package.
+
+7. C subroutines (or comparably compiled subroutines in other
+languages) supplied by you and linked into this Package in order to
+emulate subroutines and variables of the language defined by this
+Package shall not be considered part of this Package, but are the
+equivalent of input as in Paragraph 6, provided these subroutines do
+not change the language in any way that would cause it to fail the
+regression tests for the language.
+
+8. Aggregation of this Package with a commercial distribution is always
+permitted provided that the use of this Package is embedded; that is,
+when no overt attempt is made to make this Package's interfaces visible
+to the end user of the commercial distribution.  Such use shall not be
+construed as a distribution of this Package.
+
+9. The name of the Copyright Holder may not be used to endorse or promote
+products derived from this software without specific prior written permission.
+
+10. THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+
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+© 2016 GitHub, Inc. Terms Privacy Security Status Help

http://git-wip-us.apache.org/repos/asf/incubator-hawq/blob/98f7e8e9/src/include/catalog/JSON.pm
----------------------------------------------------------------------
diff --git a/src/include/catalog/JSON.pm b/src/include/catalog/JSON.pm
new file mode 100644
index 0000000..661cb25
--- /dev/null
+++ b/src/include/catalog/JSON.pm
@@ -0,0 +1,2223 @@
+package JSON;
+
+
+use strict;
+use Carp ();
+use base qw(Exporter);
+@JSON::EXPORT = qw(from_json to_json jsonToObj objToJson encode_json decode_json);
+
+BEGIN {
+    $JSON::VERSION = '2.27';
+    $JSON::DEBUG   = 0 unless (defined $JSON::DEBUG);
+}
+
+my $Module_XS  = 'JSON::XS';
+my $Module_PP  = 'JSON::PP';
+my $XS_Version = '2.27';
+
+
+# XS and PP common methods
+
+my @PublicMethods = qw/
+    ascii latin1 utf8 pretty indent space_before space_after relaxed canonical allow_nonref 
+    allow_blessed convert_blessed filter_json_object filter_json_single_key_object 
+    shrink max_depth max_size encode decode decode_prefix allow_unknown
+/;
+
+my @Properties = qw/
+    ascii latin1 utf8 indent space_before space_after relaxed canonical allow_nonref
+    allow_blessed convert_blessed shrink max_depth max_size allow_unknown
+/;
+
+my @XSOnlyMethods = qw//; # Currently nothing
+
+my @PPOnlyMethods = qw/
+    indent_length sort_by
+    allow_singlequote allow_bignum loose allow_barekey escape_slash as_nonblessed
+/; # JSON::PP specific
+
+
+# used in _load_xs and _load_pp ($INSTALL_ONLY is not used currently)
+my $_INSTALL_DONT_DIE  = 1; # When _load_xs fails to load XS, don't die.
+my $_INSTALL_ONLY      = 2; # Don't call _set_methods()
+my $_ALLOW_UNSUPPORTED = 0;
+my $_UNIV_CONV_BLESSED = 0;
+
+
+# Check the environment variable to decide worker module. 
+
+unless ($JSON::Backend) {
+    $JSON::DEBUG and  Carp::carp("Check used worker module...");
+
+    my $backend = exists $ENV{PERL_JSON_BACKEND} ? $ENV{PERL_JSON_BACKEND} : 1;
+
+    if ($backend eq '1' or $backend =~ /JSON::XS\s*,\s*JSON::PP/) {
+        _load_xs($_INSTALL_DONT_DIE) or _load_pp();
+    }
+    elsif ($backend eq '0' or $backend eq 'JSON::PP') {
+        _load_pp();
+    }
+    elsif ($backend eq '2' or $backend eq 'JSON::XS') {
+        _load_xs();
+    }
+    else {
+        Carp::croak "The value of environmental variable 'PERL_JSON_BACKEND' is invalid.";
+    }
+}
+
+
+sub import {
+    my $pkg = shift;
+    my @what_to_export;
+    my $no_export;
+
+    for my $tag (@_) {
+        if ($tag eq '-support_by_pp') {
+            if (!$_ALLOW_UNSUPPORTED++) {
+                JSON::Backend::XS
+                    ->support_by_pp(@PPOnlyMethods) if ($JSON::Backend eq $Module_XS);
+            }
+            next;
+        }
+        elsif ($tag eq '-no_export') {
+            $no_export++, next;
+        }
+        elsif ( $tag eq '-convert_blessed_universally' ) {
+            eval q|
+                require B;
+                *UNIVERSAL::TO_JSON = sub {
+                    my $b_obj = B::svref_2object( $_[0] );
+                    return    $b_obj->isa('B::HV') ? { %{ $_[0] } }
+                            : $b_obj->isa('B::AV') ? [ @{ $_[0] } ]
+                            : undef
+                            ;
+                }
+            | if ( !$_UNIV_CONV_BLESSED++ );
+            next;
+        }
+        push @what_to_export, $tag;
+    }
+
+    return if ($no_export);
+
+    __PACKAGE__->export_to_level(1, $pkg, @what_to_export);
+}
+
+
+# OBSOLETED
+
+sub jsonToObj {
+    my $alternative = 'from_json';
+    if (defined $_[0] and UNIVERSAL::isa($_[0], 'JSON')) {
+        shift @_; $alternative = 'decode';
+    }
+    Carp::carp "'jsonToObj' will be obsoleted. Please use '$alternative' instead.";
+    return JSON::from_json(@_);
+};
+
+sub objToJson {
+    my $alternative = 'to_json';
+    if (defined $_[0] and UNIVERSAL::isa($_[0], 'JSON')) {
+        shift @_; $alternative = 'encode';
+    }
+    Carp::carp "'objToJson' will be obsoleted. Please use '$alternative' instead.";
+    JSON::to_json(@_);
+};
+
+
+# INTERFACES
+
+sub to_json ($@) {
+    if ( ref($_[0]) eq 'JSON' or $_[0] eq 'JSON' ) {
+        Carp::croak "to_json should not be called as a method.";
+    }
+    my $json = new JSON;
+
+    if (@_ == 2 and ref $_[1] eq 'HASH') {
+        my $opt  = $_[1];
+        for my $method (keys %$opt) {
+            $json->$method( $opt->{$method} );
+        }
+    }
+
+    $json->encode($_[0]);
+}
+
+
+sub from_json ($@) {
+    if ( ref($_[0]) eq 'JSON' or $_[0] eq 'JSON' ) {
+        Carp::croak "from_json should not be called as a method.";
+    }
+    my $json = new JSON;
+
+    if (@_ == 2 and ref $_[1] eq 'HASH') {
+        my $opt  = $_[1];
+        for my $method (keys %$opt) {
+            $json->$method( $opt->{$method} );
+        }
+    }
+
+    return $json->decode( $_[0] );
+}
+
+
+sub true  { $JSON::true  }
+
+sub false { $JSON::false }
+
+sub null  { undef; }
+
+
+sub require_xs_version { $XS_Version; }
+
+sub backend {
+    my $proto = shift;
+    $JSON::Backend;
+}
+
+#*module = *backend;
+
+
+sub is_xs {
+    return $_[0]->module eq $Module_XS;
+}
+
+
+sub is_pp {
+    return $_[0]->module eq $Module_PP;
+}
+
+
+sub pureperl_only_methods { @PPOnlyMethods; }
+
+
+sub property {
+    my ($self, $name, $value) = @_;
+
+    if (@_ == 1) {
+        my %props;
+        for $name (@Properties) {
+            my $method = 'get_' . $name;
+            if ($name eq 'max_size') {
+                my $value = $self->$method();
+                $props{$name} = $value == 1 ? 0 : $value;
+                next;
+            }
+            $props{$name} = $self->$method();
+        }
+        return \%props;
+    }
+    elsif (@_ > 3) {
+        Carp::croak('property() can take only the option within 2 arguments.');
+    }
+    elsif (@_ == 2) {
+        if ( my $method = $self->can('get_' . $name) ) {
+            if ($name eq 'max_size') {
+                my $value = $self->$method();
+                return $value == 1 ? 0 : $value;
+            }
+            $self->$method();
+        }
+    }
+    else {
+        $self->$name($value);
+    }
+
+}
+
+
+
+# INTERNAL
+
+sub _load_xs {
+    my $opt = shift;
+
+    $JSON::DEBUG and Carp::carp "Load $Module_XS.";
+
+    # if called after install module, overload is disable.... why?
+    JSON::Boolean::_overrride_overload($Module_XS);
+    JSON::Boolean::_overrride_overload($Module_PP);
+
+    eval qq|
+        use $Module_XS $XS_Version ();
+    |;
+
+    if ($@) {
+        if (defined $opt and $opt & $_INSTALL_DONT_DIE) {
+            $JSON::DEBUG and Carp::carp "Can't load $Module_XS...($@)";
+            return 0;
+        }
+        Carp::croak $@;
+    }
+
+    unless (defined $opt and $opt & $_INSTALL_ONLY) {
+        _set_module( $JSON::Backend = $Module_XS );
+        my $data = join("", <DATA>); # this code is from Jcode 2.xx.
+        close(DATA);
+        eval $data;
+        JSON::Backend::XS->init;
+    }
+
+    return 1;
+};
+
+
+sub _load_pp {
+    my $opt = shift;
+
+    $JSON::DEBUG and Carp::carp "Load $Module_PP.";
+
+    # if called after install module, overload is disable.... why?
+    JSON::Boolean::_overrride_overload($Module_XS);
+    JSON::Boolean::_overrride_overload($Module_PP);
+
+    eval qq| require $Module_PP |;
+    if ($@) {
+        Carp::croak $@;
+    }
+
+    unless (defined $opt and $opt & $_INSTALL_ONLY) {
+        _set_module( $JSON::Backend = $Module_PP );
+        JSON::Backend::PP->init;
+    }
+};
+
+
+sub _set_module {
+    my $module = shift;
+
+    local $^W;
+    no strict qw(refs);
+
+    $JSON::true  = ${"$module\::true"};
+    $JSON::false = ${"$module\::false"};
+
+    push @JSON::ISA, $module;
+    push @{"$module\::Boolean::ISA"}, qw(JSON::Boolean);
+
+    *{"JSON::is_bool"} = \&{"$module\::is_bool"};
+
+    for my $method ($module eq $Module_XS ? @PPOnlyMethods : @XSOnlyMethods) {
+        *{"JSON::$method"} = sub {
+            Carp::carp("$method is not supported in $module.");
+            $_[0];
+        };
+    }
+
+    return 1;
+}
+
+
+
+#
+# JSON Boolean
+#
+
+package JSON::Boolean;
+
+my %Installed;
+
+sub _overrride_overload {
+    return if ($Installed{ $_[0] }++);
+
+    my $boolean = $_[0] . '::Boolean';
+
+    eval sprintf(q|
+        package %s;
+        use overload (
+            '""' => sub { ${$_[0]} == 1 ? 'true' : 'false' },
+            'eq' => sub {
+                my ($obj, $op) = ref ($_[0]) ? ($_[0], $_[1]) : ($_[1], $_[0]);
+                if ($op eq 'true' or $op eq 'false') {
+                    return "$obj" eq 'true' ? 'true' eq $op : 'false' eq $op;
+                }
+                else {
+                    return $obj ? 1 == $op : 0 == $op;
+                }
+            },
+        );
+    |, $boolean);
+
+    if ($@) { Carp::croak $@; }
+
+    return 1;
+}
+
+
+#
+# Helper classes for Backend Module (PP)
+#
+
+package JSON::Backend::PP;
+
+sub init {
+    local $^W;
+    no strict qw(refs);
+    *{"JSON::decode_json"} = \&{"JSON::PP::decode_json"};
+    *{"JSON::encode_json"} = \&{"JSON::PP::encode_json"};
+    *{"JSON::PP::is_xs"}  = sub { 0 };
+    *{"JSON::PP::is_pp"}  = sub { 1 };
+    return 1;
+}
+
+#
+# To save memory, the below lines are read only when XS backend is used.
+#
+
+package JSON;
+
+1;
+__DATA__
+
+
+#
+# Helper classes for Backend Module (XS)
+#
+
+package JSON::Backend::XS;
+
+use constant INDENT_LENGTH_FLAG => 15 << 12;
+
+use constant UNSUPPORTED_ENCODE_FLAG => {
+    ESCAPE_SLASH      => 0x00000010,
+    ALLOW_BIGNUM      => 0x00000020,
+    AS_NONBLESSED     => 0x00000040,
+    EXPANDED          => 0x10000000, # for developer's
+};
+
+use constant UNSUPPORTED_DECODE_FLAG => {
+    LOOSE             => 0x00000001,
+    ALLOW_BIGNUM      => 0x00000002,
+    ALLOW_BAREKEY     => 0x00000004,
+    ALLOW_SINGLEQUOTE => 0x00000008,
+    EXPANDED          => 0x20000000, # for developer's
+};
+
+
+sub init {
+    local $^W;
+    no strict qw(refs);
+    *{"JSON::decode_json"} = \&{"JSON::XS::decode_json"};
+    *{"JSON::encode_json"} = \&{"JSON::XS::encode_json"};
+    *{"JSON::XS::is_xs"}  = sub { 1 };
+    *{"JSON::XS::is_pp"}  = sub { 0 };
+    return 1;
+}
+
+
+sub support_by_pp {
+    my ($class, @methods) = @_;
+
+    local $^W;
+    no strict qw(refs);
+
+    my $JSON_XS_encode_orignal     = \&JSON::XS::encode;
+    my $JSON_XS_decode_orignal     = \&JSON::XS::decode;
+    my $JSON_XS_incr_parse_orignal = \&JSON::XS::incr_parse;
+
+    *JSON::XS::decode     = \&JSON::Backend::XS::Supportable::_decode;
+    *JSON::XS::encode     = \&JSON::Backend::XS::Supportable::_encode;
+    *JSON::XS::incr_parse = \&JSON::Backend::XS::Supportable::_incr_parse;
+
+    *{JSON::XS::_original_decode}     = $JSON_XS_decode_orignal;
+    *{JSON::XS::_original_encode}     = $JSON_XS_encode_orignal;
+    *{JSON::XS::_original_incr_parse} = $JSON_XS_incr_parse_orignal;
+
+    push @JSON::Backend::XS::Supportable::ISA, 'JSON';
+
+    my $pkg = 'JSON::Backend::XS::Supportable';
+
+    *{JSON::new} = sub {
+        my $proto = new JSON::XS; $$proto = 0;
+        bless  $proto, $pkg;
+    };
+
+
+    for my $method (@methods) {
+        my $flag = uc($method);
+        my $type |= (UNSUPPORTED_ENCODE_FLAG->{$flag} || 0);
+           $type |= (UNSUPPORTED_DECODE_FLAG->{$flag} || 0);
+
+        next unless($type);
+
+        $pkg->_make_unsupported_method($method => $type);
+    }
+
+    push @{"JSON::XS::Boolean::ISA"}, qw(JSON::PP::Boolean);
+    push @{"JSON::PP::Boolean::ISA"}, qw(JSON::Boolean);
+
+    $JSON::DEBUG and Carp::carp("set -support_by_pp mode.");
+
+    return 1;
+}
+
+
+
+
+#
+# Helper classes for XS
+#
+
+package JSON::Backend::XS::Supportable;
+
+$Carp::Internal{'JSON::Backend::XS::Supportable'} = 1;
+
+sub _make_unsupported_method {
+    my ($pkg, $method, $type) = @_;
+
+    local $^W;
+    no strict qw(refs);
+
+    *{"$pkg\::$method"} = sub {
+        local $^W;
+        if (defined $_[1] ? $_[1] : 1) {
+            ${$_[0]} |= $type;
+        }
+        else {
+            ${$_[0]} &= ~$type;
+        }
+        $_[0];
+    };
+
+    *{"$pkg\::get_$method"} = sub {
+        ${$_[0]} & $type ? 1 : '';
+    };
+
+}
+
+
+sub _set_for_pp {
+    require JSON::PP;
+    my $type  = shift;
+    my $pp    = new JSON::PP;
+    my $prop = $_[0]->property;
+
+    for my $name (keys %$prop) {
+        $pp->$name( $prop->{$name} ? $prop->{$name} : 0 );
+    }
+
+    my $unsupported = $type eq 'encode' ? JSON::Backend::XS::UNSUPPORTED_ENCODE_FLAG
+                                        : JSON::Backend::XS::UNSUPPORTED_DECODE_FLAG;
+    my $flags       = ${$_[0]} || 0;
+
+    for my $name (keys %$unsupported) {
+        next if ($name eq 'EXPANDED'); # for developer's
+        my $enable = ($flags & $unsupported->{$name}) ? 1 : 0;
+        my $method = lc $name;
+        $pp->$method($enable);
+    }
+
+    $pp->indent_length( $_[0]->get_indent_length );
+
+    return $pp;
+}
+
+sub _encode { # using with PP encod
+    if (${$_[0]}) {
+        _set_for_pp('encode' => @_)->encode($_[1]);
+    }
+    else {
+        $_[0]->_original_encode( $_[1] );
+    }
+}
+
+
+sub _decode { # if unsupported-flag is set, use PP
+    if (${$_[0]}) {
+        _set_for_pp('decode' => @_)->decode($_[1]);
+    }
+    else {
+        $_[0]->_original_decode( $_[1] );
+    }
+}
+
+
+sub decode_prefix { # if unsupported-flag is set, use PP
+    _set_for_pp('decode' => @_)->decode_prefix($_[1]);
+}
+
+
+sub _incr_parse {
+    if (${$_[0]}) {
+        _set_for_pp('decode' => @_)->incr_parse($_[1]);
+    }
+    else {
+        $_[0]->_original_incr_parse( $_[1] );
+    }
+}
+
+
+sub get_indent_length {
+    ${$_[0]} << 4 >> 16;
+}
+
+
+sub indent_length {
+    my $length = $_[1];
+
+    if (!defined $length or $length > 15 or $length < 0) {
+        Carp::carp "The acceptable range of indent_length() is 0 to 15.";
+    }
+    else {
+        local $^W;
+        $length <<= 12;
+        ${$_[0]} &= ~ JSON::Backend::XS::INDENT_LENGTH_FLAG;
+        ${$_[0]} |= $length;
+        *JSON::XS::encode = \&JSON::Backend::XS::Supportable::_encode;
+    }
+
+    $_[0];
+}
+
+
+1;
+__END__
+
+=head1 NAME
+
+JSON - JSON (JavaScript Object Notation) encoder/decoder
+
+=head1 SYNOPSIS
+
+ use JSON; # imports encode_json, decode_json, to_json and from_json.
+ 
+ # simple and fast interfaces (expect/generate UTF-8)
+ 
+ $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
+ $perl_hash_or_arrayref  = decode_json $utf8_encoded_json_text;
+ 
+ # OO-interface
+ 
+ $json = JSON->new->allow_nonref;
+ 
+ $json_text   = $json->encode( $perl_scalar );
+ $perl_scalar = $json->decode( $json_text );
+ 
+ $pretty_printed = $json->pretty->encode( $perl_scalar ); # pretty-printing
+ 
+ # If you want to use PP only support features, call with '-support_by_pp'
+ # When XS unsupported feature is enable, using PP (de|en)code instead of XS ones.
+ 
+ use JSON -support_by_pp;
+ 
+ # option-acceptable interfaces (expect/generate UNICODE by default)
+ 
+ $json_text   = to_json( $perl_scalar, { ascii => 1, pretty => 1 } );
+ $perl_scalar = from_json( $json_text, { utf8  => 1 } );
+ 
+ # Between (en|de)code_json and (to|from)_json, if you want to write
+ # a code which communicates to an outer world (encoded in UTF-8),
+ # recommend to use (en|de)code_json.
+ 
+=head1 VERSION
+
+    2.27
+
+This version is compatible with JSON::XS B<2.27> and later.
+
+
+=head1 DESCRIPTION
+
+ ************************** CAUTION ********************************
+ * This is 'JSON module version 2' and there are many differences  *
+ * to version 1.xx                                                 *
+ * Please check your applications useing old version.              *
+ *   See to 'INCOMPATIBLE CHANGES TO OLD VERSION'                  *
+ *******************************************************************
+
+JSON (JavaScript Object Notation) is a simple data format.
+See to L<http://www.json.org/> and C<RFC4627>(L<http://www.ietf.org/rfc/rfc4627.txt>).
+
+This module converts Perl data structures to JSON and vice versa using either
+L<JSON::XS> or L<JSON::PP>.
+
+JSON::XS is the fastest and most proper JSON module on CPAN which must be
+compiled and installed in your environment.
+JSON::PP is a pure-Perl module which is bundled in this distribution and
+has a strong compatibility to JSON::XS.
+
+This module try to use JSON::XS by default and fail to it, use JSON::PP instead.
+So its features completely depend on JSON::XS or JSON::PP.
+
+See to L<BACKEND MODULE DECISION>.
+
+To distinguish the module name 'JSON' and the format type JSON,
+the former is quoted by CE<lt>E<gt> (its results vary with your using media),
+and the latter is left just as it is.
+
+Module name : C<JSON>
+
+Format type : JSON
+
+=head2 FEATURES
+
+=over
+
+=item * correct unicode handling
+
+This module (i.e. backend modules) knows how to handle Unicode, documents
+how and when it does so, and even documents what "correct" means.
+
+Even though there are limitations, this feature is available since Perl version 5.6.
+
+JSON::XS requires Perl 5.8.2 (but works correctly in 5.8.8 or later), so in older versions
+C<JSON> sholud call JSON::PP as the backend which can be used since Perl 5.005.
+
+With Perl 5.8.x JSON::PP works, but from 5.8.0 to 5.8.2, because of a Perl side problem,
+JSON::PP works slower in the versions. And in 5.005, the Unicode handling is not available.
+See to L<JSON::PP/UNICODE HANDLING ON PERLS> for more information.
+
+See also to L<JSON::XS/A FEW NOTES ON UNICODE AND PERL>
+and L<JSON::XS/ENCODING/CODESET_FLAG_NOTES>.
+
+
+=item * round-trip integrity
+
+When you serialise a perl data structure using only data types supported
+by JSON and Perl, the deserialised data structure is identical on the Perl
+level. (e.g. the string "2.0" doesn't suddenly become "2" just because
+it looks like a number). There I<are> minor exceptions to this, read the
+L</MAPPING> section below to learn about those.
+
+
+=item * strict checking of JSON correctness
+
+There is no guessing, no generating of illegal JSON texts by default,
+and only JSON is accepted as input by default (the latter is a security
+feature).
+
+See to L<JSON::XS/FEATURES> and L<JSON::PP/FEATURES>.
+
+=item * fast
+
+This module returns a JSON::XS object itself if available.
+Compared to other JSON modules and other serialisers such as Storable,
+JSON::XS usually compares favourably in terms of speed, too.
+
+If not available, C<JSON> returns a JSON::PP object instead of JSON::XS and
+it is very slow as pure-Perl.
+
+=item * simple to use
+
+This module has both a simple functional interface as well as an
+object oriented interface interface.
+
+=item * reasonably versatile output formats
+
+You can choose between the most compact guaranteed-single-line format possible
+(nice for simple line-based protocols), a pure-ASCII format (for when your transport
+is not 8-bit clean, still supports the whole Unicode range), or a pretty-printed
+format (for when you want to read that stuff). Or you can combine those features
+in whatever way you like.
+
+=back
+
+=head1 FUNCTIONAL INTERFACE
+
+Some documents are copied and modified from L<JSON::XS/FUNCTIONAL INTERFACE>.
+C<to_json> and C<from_json> are additional functions.
+
+=head2 encode_json
+
+    $json_text = encode_json $perl_scalar
+
+Converts the given Perl data structure to a UTF-8 encoded, binary string.
+
+This function call is functionally identical to:
+
+    $json_text = JSON->new->utf8->encode($perl_scalar)
+
+=head2 decode_json
+
+    $perl_scalar = decode_json $json_text
+
+The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
+to parse that as an UTF-8 encoded JSON text, returning the resulting
+reference.
+
+This function call is functionally identical to:
+
+    $perl_scalar = JSON->new->utf8->decode($json_text)
+
+
+=head2 to_json
+
+   $json_text = to_json($perl_scalar)
+
+Converts the given Perl data structure to a json string.
+
+This function call is functionally identical to:
+
+   $json_text = JSON->new->encode($perl_scalar)
+
+Takes a hash reference as the second.
+
+   $json_text = to_json($perl_scalar, $flag_hashref)
+
+So,
+
+   $json_text = encode_json($perl_scalar, {utf8 => 1, pretty => 1})
+
+equivalent to:
+
+   $json_text = JSON->new->utf8(1)->pretty(1)->encode($perl_scalar)
+
+If you want to write a modern perl code which communicates to outer world,
+you should use C<encode_json> (supposed that JSON data are encoded in UTF-8).
+
+=head2 from_json
+
+   $perl_scalar = from_json($json_text)
+
+The opposite of C<to_json>: expects a json string and tries
+to parse it, returning the resulting reference.
+
+This function call is functionally identical to:
+
+    $perl_scalar = JSON->decode($json_text)
+
+Takes a hash reference as the second.
+
+    $perl_scalar = from_json($json_text, $flag_hashref)
+
+So,
+
+    $perl_scalar = from_json($json_text, {utf8 => 1})
+
+equivalent to:
+
+    $perl_scalar = JSON->new->utf8(1)->decode($json_text)
+
+If you want to write a modern perl code which communicates to outer world,
+you should use C<decode_json> (supposed that JSON data are encoded in UTF-8).
+
+=head2 JSON::is_bool
+
+    $is_boolean = JSON::is_bool($scalar)
+
+Returns true if the passed scalar represents either JSON::true or
+JSON::false, two constants that act like C<1> and C<0> respectively
+and are also used to represent JSON C<true> and C<false> in Perl strings.
+
+=head2 JSON::true
+
+Returns JSON true value which is blessed object.
+It C<isa> JSON::Boolean object.
+
+=head2 JSON::false
+
+Returns JSON false value which is blessed object.
+It C<isa> JSON::Boolean object.
+
+=head2 JSON::null
+
+Returns C<undef>.
+
+See L<MAPPING>, below, for more information on how JSON values are mapped to
+Perl.
+
+=head1 HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER
+
+This section supposes that your perl vresion is 5.8 or later.
+
+If you know a JSON text from an outer world - a network, a file content, and so on,
+is encoded in UTF-8, you should use C<decode_json> or C<JSON> module object
+with C<utf8> enable. And the decoded result will contain UNICODE characters.
+
+  # from network
+  my $json        = JSON->new->utf8;
+  my $json_text   = CGI->new->param( 'json_data' );
+  my $perl_scalar = $json->decode( $json_text );
+  
+  # from file content
+  local $/;
+  open( my $fh, '<', 'json.data' );
+  $json_text   = <$fh>;
+  $perl_scalar = decode_json( $json_text );
+
+If an outer data is not encoded in UTF-8, firstly you should C<decode> it.
+
+  use Encode;
+  local $/;
+  open( my $fh, '<', 'json.data' );
+  my $encoding = 'cp932';
+  my $unicode_json_text = decode( $encoding, <$fh> ); # UNICODE
+  
+  # or you can write the below code.
+  #
+  # open( my $fh, "<:encoding($encoding)", 'json.data' );
+  # $unicode_json_text = <$fh>;
+
+In this case, C<$unicode_json_text> is of course UNICODE string.
+So you B<cannot> use C<decode_json> nor C<JSON> module object with C<utf8> enable.
+Instead of them, you use C<JSON> module object with C<utf8> disable or C<from_json>.
+
+  $perl_scalar = $json->utf8(0)->decode( $unicode_json_text );
+  # or
+  $perl_scalar = from_json( $unicode_json_text );
+
+Or C<encode 'utf8'> and C<decode_json>:
+
+  $perl_scalar = decode_json( encode( 'utf8', $unicode_json_text ) );
+  # this way is not efficient.
+
+And now, you want to convert your C<$perl_scalar> into JSON data and
+send it to an outer world - a network or a file content, and so on.
+
+Your data usually contains UNICODE strings and you want the converted data to be encoded
+in UTF-8, you should use C<encode_json> or C<JSON> module object with C<utf8> enable.
+
+  print encode_json( $perl_scalar ); # to a network? file? or display?
+  # or
+  print $json->utf8->encode( $perl_scalar );
+
+If C<$perl_scalar> does not contain UNICODE but C<$encoding>-encoded strings
+for some reason, then its characters are regarded as B<latin1> for perl
+(because it does not concern with your $encoding).
+You B<cannot> use C<encode_json> nor C<JSON> module object with C<utf8> enable.
+Instead of them, you use C<JSON> module object with C<utf8> disable or C<to_json>.
+Note that the resulted text is a UNICODE string but no problem to print it.
+
+  # $perl_scalar contains $encoding encoded string values
+  $unicode_json_text = $json->utf8(0)->encode( $perl_scalar );
+  # or 
+  $unicode_json_text = to_json( $perl_scalar );
+  # $unicode_json_text consists of characters less than 0x100
+  print $unicode_json_text;
+
+Or C<decode $encoding> all string values and C<encode_json>:
+
+  $perl_scalar->{ foo } = decode( $encoding, $perl_scalar->{ foo } );
+  # ... do it to each string values, then encode_json
+  $json_text = encode_json( $perl_scalar );
+
+This method is a proper way but probably not efficient.
+
+See to L<Encode>, L<perluniintro>.
+
+
+=head1 COMMON OBJECT-ORIENTED INTERFACE
+
+=head2 new
+
+    $json = new JSON
+
+Returns a new C<JSON> object inherited from either JSON::XS or JSON::PP
+that can be used to de/encode JSON strings.
+
+All boolean flags described below are by default I<disabled>.
+
+The mutators for flags all return the JSON object again and thus calls can
+be chained:
+
+   my $json = JSON->new->utf8->space_after->encode({a => [1,2]})
+   => {"a": [1, 2]}
+
+=head2 ascii
+
+    $json = $json->ascii([$enable])
+    
+    $enabled = $json->get_ascii
+
+If $enable is true (or missing), then the encode method will not generate characters outside
+the code range 0..127. Any Unicode characters outside that range will be escaped using either
+a single \uXXXX or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.
+
+If $enable is false, then the encode method will not escape Unicode characters unless
+required by the JSON syntax or other flags. This results in a faster and more compact format.
+
+This feature depends on the used Perl version and environment.
+
+See to L<JSON::PP/UNICODE HANDLING ON PERLS> if the backend is PP.
+
+  JSON->new->ascii(1)->encode([chr 0x10401])
+  => ["\ud801\udc01"]
+
+=head2 latin1
+
+    $json = $json->latin1([$enable])
+    
+    $enabled = $json->get_latin1
+
+If $enable is true (or missing), then the encode method will encode the resulting JSON
+text as latin1 (or iso-8859-1), escaping any characters outside the code range 0..255.
+
+If $enable is false, then the encode method will not escape Unicode characters
+unless required by the JSON syntax or other flags.
+
+  JSON->new->latin1->encode (["\x{89}\x{abc}"]
+  => ["\x{89}\\u0abc"]    # (perl syntax, U+abc escaped, U+89 not)
+
+=head2 utf8
+
+    $json = $json->utf8([$enable])
+    
+    $enabled = $json->get_utf8
+
+If $enable is true (or missing), then the encode method will encode the JSON result
+into UTF-8, as required by many protocols, while the decode method expects to be handled
+an UTF-8-encoded string. Please note that UTF-8-encoded strings do not contain any
+characters outside the range 0..255, they are thus useful for bytewise/binary I/O.
+
+In future versions, enabling this option might enable autodetection of the UTF-16 and UTF-32
+encoding families, as described in RFC4627.
+
+If $enable is false, then the encode method will return the JSON string as a (non-encoded)
+Unicode string, while decode expects thus a Unicode string. Any decoding or encoding
+(e.g. to UTF-8 or UTF-16) needs to be done yourself, e.g. using the Encode module.
+
+
+Example, output UTF-16BE-encoded JSON:
+
+  use Encode;
+  $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
+
+Example, decode UTF-32LE-encoded JSON:
+
+  use Encode;
+  $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
+
+See to L<JSON::PP/UNICODE HANDLING ON PERLS> if the backend is PP.
+
+
+=head2 pretty
+
+    $json = $json->pretty([$enable])
+
+This enables (or disables) all of the C<indent>, C<space_before> and
+C<space_after> (and in the future possibly more) flags in one call to
+generate the most readable (or most compact) form possible.
+
+Equivalent to:
+
+   $json->indent->space_before->space_after
+
+The indent space length is three and JSON::XS cannot change the indent
+space length.
+
+=head2 indent
+
+    $json = $json->indent([$enable])
+    
+    $enabled = $json->get_indent
+
+If C<$enable> is true (or missing), then the C<encode> method will use a multiline
+format as output, putting every array member or object/hash key-value pair
+into its own line, identing them properly.
+
+If C<$enable> is false, no newlines or indenting will be produced, and the
+resulting JSON text is guarenteed not to contain any C<newlines>.
+
+This setting has no effect when decoding JSON texts.
+
+The indent space length is three.
+With JSON::PP, you can also access C<indent_length> to change indent space length.
+
+
+=head2 space_before
+
+    $json = $json->space_before([$enable])
+    
+    $enabled = $json->get_space_before
+
+If C<$enable> is true (or missing), then the C<encode> method will add an extra
+optional space before the C<:> separating keys from values in JSON objects.
+
+If C<$enable> is false, then the C<encode> method will not add any extra
+space at those places.
+
+This setting has no effect when decoding JSON texts.
+
+Example, space_before enabled, space_after and indent disabled:
+
+   {"key" :"value"}
+
+
+=head2 space_after
+
+    $json = $json->space_after([$enable])
+    
+    $enabled = $json->get_space_after
+
+If C<$enable> is true (or missing), then the C<encode> method will add an extra
+optional space after the C<:> separating keys from values in JSON objects
+and extra whitespace after the C<,> separating key-value pairs and array
+members.
+
+If C<$enable> is false, then the C<encode> method will not add any extra
+space at those places.
+
+This setting has no effect when decoding JSON texts.
+
+Example, space_before and indent disabled, space_after enabled:
+
+   {"key": "value"}
+
+
+=head2 relaxed
+
+    $json = $json->relaxed([$enable])
+    
+    $enabled = $json->get_relaxed
+
+If C<$enable> is true (or missing), then C<decode> will accept some
+extensions to normal JSON syntax (see below). C<encode> will not be
+affected in anyway. I<Be aware that this option makes you accept invalid
+JSON texts as if they were valid!>. I suggest only to use this option to
+parse application-specific files written by humans (configuration files,
+resource files etc.)
+
+If C<$enable> is false (the default), then C<decode> will only accept
+valid JSON texts.
+
+Currently accepted extensions are:
+
+=over 4
+
+=item * list items can have an end-comma
+
+JSON I<separates> array elements and key-value pairs with commas. This
+can be annoying if you write JSON texts manually and want to be able to
+quickly append elements, so this extension accepts comma at the end of
+such items not just between them:
+
+   [
+      1,
+      2, <- this comma not normally allowed
+   ]
+   {
+      "k1": "v1",
+      "k2": "v2", <- this comma not normally allowed
+   }
+
+=item * shell-style '#'-comments
+
+Whenever JSON allows whitespace, shell-style comments are additionally
+allowed. They are terminated by the first carriage-return or line-feed
+character, after which more white-space and comments are allowed.
+
+  [
+     1, # this comment not allowed in JSON
+        # neither this one...
+  ]
+
+=back
+
+
+=head2 canonical
+
+    $json = $json->canonical([$enable])
+    
+    $enabled = $json->get_canonical
+
+If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
+by sorting their keys. This is adding a comparatively high overhead.
+
+If C<$enable> is false, then the C<encode> method will output key-value
+pairs in the order Perl stores them (which will likely change between runs
+of the same script).
+
+This option is useful if you want the same data structure to be encoded as
+the same JSON text (given the same overall settings). If it is disabled,
+the same hash might be encoded differently even if contains the same data,
+as key-value pairs have no inherent ordering in Perl.
+
+This setting has no effect when decoding JSON texts.
+
+=head2 allow_nonref
+
+    $json = $json->allow_nonref([$enable])
+    
+    $enabled = $json->get_allow_nonref
+
+If C<$enable> is true (or missing), then the C<encode> method can convert a
+non-reference into its corresponding string, number or null JSON value,
+which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
+values instead of croaking.
+
+If C<$enable> is false, then the C<encode> method will croak if it isn't
+passed an arrayref or hashref, as JSON texts must either be an object
+or array. Likewise, C<decode> will croak if given something that is not a
+JSON object or array.
+
+   JSON->new->allow_nonref->encode ("Hello, World!")
+   => "Hello, World!"
+
+=head2 allow_unknown
+
+    $json = $json->allow_unknown ([$enable])
+    
+    $enabled = $json->get_allow_unknown
+
+If $enable is true (or missing), then "encode" will *not* throw an
+exception when it encounters values it cannot represent in JSON (for
+example, filehandles) but instead will encode a JSON "null" value.
+Note that blessed objects are not included here and are handled
+separately by c<allow_nonref>.
+
+If $enable is false (the default), then "encode" will throw an
+exception when it encounters anything it cannot encode as JSON.
+
+This option does not affect "decode" in any way, and it is
+recommended to leave it off unless you know your communications
+partner.
+
+=head2 allow_blessed
+
+    $json = $json->allow_blessed([$enable])
+    
+    $enabled = $json->get_allow_blessed
+
+If C<$enable> is true (or missing), then the C<encode> method will not
+barf when it encounters a blessed reference. Instead, the value of the
+B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
+disabled or no C<TO_JSON> method found) or a representation of the
+object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
+encoded. Has no effect on C<decode>.
+
+If C<$enable> is false (the default), then C<encode> will throw an
+exception when it encounters a blessed object.
+
+
+=head2 convert_blessed
+
+    $json = $json->convert_blessed([$enable])
+    
+    $enabled = $json->get_convert_blessed
+
+If C<$enable> is true (or missing), then C<encode>, upon encountering a
+blessed object, will check for the availability of the C<TO_JSON> method
+on the object's class. If found, it will be called in scalar context
+and the resulting scalar will be encoded instead of the object. If no
+C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
+to do.
+
+The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
+returns other blessed objects, those will be handled in the same
+way. C<TO_JSON> must take care of not causing an endless recursion cycle
+(== crash) in this case. The name of C<TO_JSON> was chosen because other
+methods called by the Perl core (== not by the user of the object) are
+usually in upper case letters and to avoid collisions with the C<to_json>
+function or method.
+
+This setting does not yet influence C<decode> in any way.
+
+If C<$enable> is false, then the C<allow_blessed> setting will decide what
+to do when a blessed object is found.
+
+=over
+
+=item convert_blessed_universally mode
+
+If use C<JSON> with C<-convert_blessed_universally>, the C<UNIVERSAL::TO_JSON>
+subroutine is defined as the below code:
+
+   *UNIVERSAL::TO_JSON = sub {
+       my $b_obj = B::svref_2object( $_[0] );
+       return    $b_obj->isa('B::HV') ? { %{ $_[0] } }
+               : $b_obj->isa('B::AV') ? [ @{ $_[0] } ]
+               : undef
+               ;
+   }
+
+This will cause that C<encode> method converts simple blessed objects into
+JSON objects as non-blessed object.
+
+   JSON -convert_blessed_universally;
+   $json->allow_blessed->convert_blessed->encode( $blessed_object )
+
+This feature is experimental and may be removed in the future.
+
+=back
+
+=head2 filter_json_object
+
+    $json = $json->filter_json_object([$coderef])
+
+When C<$coderef> is specified, it will be called from C<decode> each
+time it decodes a JSON object. The only argument passed to the coderef
+is a reference to the newly-created hash. If the code references returns
+a single scalar (which need not be a reference), this value
+(i.e. a copy of that scalar to avoid aliasing) is inserted into the
+deserialised data structure. If it returns an empty list
+(NOTE: I<not> C<undef>, which is a valid scalar), the original deserialised
+hash will be inserted. This setting can slow down decoding considerably.
+
+When C<$coderef> is omitted or undefined, any existing callback will
+be removed and C<decode> will not change the deserialised hash in any
+way.
+
+Example, convert all JSON objects into the integer 5:
+
+   my $js = JSON->new->filter_json_object (sub { 5 });
+   # returns [5]
+   $js->decode ('[{}]'); # the given subroutine takes a hash reference.
+   # throw an exception because allow_nonref is not enabled
+   # so a lone 5 is not allowed.
+   $js->decode ('{"a":1, "b":2}');
+
+
+=head2 filter_json_single_key_object
+
+    $json = $json->filter_json_single_key_object($key [=> $coderef])
+
+Works remotely similar to C<filter_json_object>, but is only called for
+JSON objects having a single key named C<$key>.
+
+This C<$coderef> is called before the one specified via
+C<filter_json_object>, if any. It gets passed the single value in the JSON
+object. If it returns a single value, it will be inserted into the data
+structure. If it returns nothing (not even C<undef> but the empty list),
+the callback from C<filter_json_object> will be called next, as if no
+single-key callback were specified.
+
+If C<$coderef> is omitted or undefined, the corresponding callback will be
+disabled. There can only ever be one callback for a given key.
+
+As this callback gets called less often then the C<filter_json_object>
+one, decoding speed will not usually suffer as much. Therefore, single-key
+objects make excellent targets to serialise Perl objects into, especially
+as single-key JSON objects are as close to the type-tagged value concept
+as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
+support this in any way, so you need to make sure your data never looks
+like a serialised Perl hash.
+
+Typical names for the single object key are C<__class_whatever__>, or
+C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
+things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
+with real hashes.
+
+Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
+into the corresponding C<< $WIDGET{<id>} >> object:
+
+   # return whatever is in $WIDGET{5}:
+   JSON
+      ->new
+      ->filter_json_single_key_object (__widget__ => sub {
+            $WIDGET{ $_[0] }
+         })
+      ->decode ('{"__widget__": 5')
+
+   # this can be used with a TO_JSON method in some "widget" class
+   # for serialisation to json:
+   sub WidgetBase::TO_JSON {
+      my ($self) = @_;
+
+      unless ($self->{id}) {
+         $self->{id} = ..get..some..id..;
+         $WIDGET{$self->{id}} = $self;
+      }
+
+      { __widget__ => $self->{id} }
+   }
+
+
+=head2 shrink
+
+    $json = $json->shrink([$enable])
+    
+    $enabled = $json->get_shrink
+
+With JSON::XS, this flag resizes strings generated by either
+C<encode> or C<decode> to their minimum size possible. This can save
+memory when your JSON texts are either very very long or you have many
+short strings. It will also try to downgrade any strings to octet-form
+if possible: perl stores strings internally either in an encoding called
+UTF-X or in octet-form. The latter cannot store everything but uses less
+space in general (and some buggy Perl or C code might even rely on that
+internal representation being used).
+
+With JSON::PP, it is noop about resizing strings but tries
+C<utf8::downgrade> to the returned string by C<encode>. See to L<utf8>.
+
+See to L<JSON::XS/OBJECT-ORIENTED INTERFACE> and L<JSON::PP/METHODS>.
+
+=head2 max_depth
+
+    $json = $json->max_depth([$maximum_nesting_depth])
+    
+    $max_depth = $json->get_max_depth
+
+Sets the maximum nesting level (default C<512>) accepted while encoding
+or decoding. If a higher nesting level is detected in JSON text or a Perl
+data structure, then the encoder and decoder will stop and croak at that
+point.
+
+Nesting level is defined by number of hash- or arrayrefs that the encoder
+needs to traverse to reach a given point or the number of C<{> or C<[>
+characters without their matching closing parenthesis crossed to reach a
+given character in a string.
+
+If no argument is given, the highest possible setting will be used, which
+is rarely useful.
+
+Note that nesting is implemented by recursion in C. The default value has
+been chosen to be as large as typical operating systems allow without
+crashing. (JSON::XS)
+
+With JSON::PP as the backend, when a large value (100 or more) was set and
+it de/encodes a deep nested object/text, it may raise a warning
+'Deep recursion on subroutin' at the perl runtime phase.
+
+See L<JSON::XS/SECURITY CONSIDERATIONS> for more info on why this is useful.
+
+=head2 max_size
+
+    $json = $json->max_size([$maximum_string_size])
+    
+    $max_size = $json->get_max_size
+
+Set the maximum length a JSON text may have (in bytes) where decoding is
+being attempted. The default is C<0>, meaning no limit. When C<decode>
+is called on a string that is longer then this many bytes, it will not
+attempt to decode the string but throw an exception. This setting has no
+effect on C<encode> (yet).
+
+If no argument is given, the limit check will be deactivated (same as when
+C<0> is specified).
+
+See L<JSON::XS/SECURITY CONSIDERATIONS>, below, for more info on why this is useful.
+
+=head2 encode
+
+    $json_text = $json->encode($perl_scalar)
+
+Converts the given Perl data structure (a simple scalar or a reference
+to a hash or array) to its JSON representation. Simple scalars will be
+converted into JSON string or number sequences, while references to arrays
+become JSON arrays and references to hashes become JSON objects. Undefined
+Perl values (e.g. C<undef>) become JSON C<null> values.
+References to the integers C<0> and C<1> are converted into C<true> and C<false>.
+
+=head2 decode
+
+    $perl_scalar = $json->decode($json_text)
+
+The opposite of C<encode>: expects a JSON text and tries to parse it,
+returning the resulting simple scalar or reference. Croaks on error.
+
+JSON numbers and strings become simple Perl scalars. JSON arrays become
+Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
+C<1> (C<JSON::true>), C<false> becomes C<0> (C<JSON::false>) and
+C<null> becomes C<undef>.
+
+=head2 decode_prefix
+
+    ($perl_scalar, $characters) = $json->decode_prefix($json_text)
+
+This works like the C<decode> method, but instead of raising an exception
+when there is trailing garbage after the first JSON object, it will
+silently stop parsing there and return the number of characters consumed
+so far.
+
+   JSON->new->decode_prefix ("[1] the tail")
+   => ([], 3)
+
+See to L<JSON::XS/OBJECT-ORIENTED INTERFACE>
+
+=head2 property
+
+    $boolean = $json->property($property_name)
+
+Returns a boolean value about above some properties.
+
+The available properties are C<ascii>, C<latin1>, C<utf8>,
+C<indent>,C<space_before>, C<space_after>, C<relaxed>, C<canonical>,
+C<allow_nonref>, C<allow_unknown>, C<allow_blessed>, C<convert_blessed>,
+C<shrink>, C<max_depth> and C<max_size>.
+
+   $boolean = $json->property('utf8');
+    => 0
+   $json->utf8;
+   $boolean = $json->property('utf8');
+    => 1
+
+Sets the property with a given boolean value.
+
+    $json = $json->property($property_name => $boolean);
+
+With no argumnt, it returns all the above properties as a hash reference.
+
+    $flag_hashref = $json->property();
+
+=head1 INCREMENTAL PARSING
+
+Most of this section are copied and modified from L<JSON::XS/INCREMENTAL PARSING>.
+
+In some cases, there is the need for incremental parsing of JSON texts.
+This module does allow you to parse a JSON stream incrementally.
+It does so by accumulating text until it has a full JSON object, which
+it then can decode. This process is similar to using C<decode_prefix>
+to see if a full JSON object is available, but is much more efficient
+(and can be implemented with a minimum of method calls).
+
+The backend module will only attempt to parse the JSON text once it is sure it
+has enough text to get a decisive result, using a very simple but
+truly incremental parser. This means that it sometimes won't stop as
+early as the full parser, for example, it doesn't detect parenthese
+mismatches. The only thing it guarantees is that it starts decoding as
+soon as a syntactically valid JSON text has been seen. This means you need
+to set resource limits (e.g. C<max_size>) to ensure the parser will stop
+parsing in the presence if syntax errors.
+
+The following methods implement this incremental parser.
+
+=head2 incr_parse
+
+    $json->incr_parse( [$string] ) # void context
+    
+    $obj_or_undef = $json->incr_parse( [$string] ) # scalar context
+    
+    @obj_or_empty = $json->incr_parse( [$string] ) # list context
+
+This is the central parsing function. It can both append new text and
+extract objects from the stream accumulated so far (both of these
+functions are optional).
+
+If C<$string> is given, then this string is appended to the already
+existing JSON fragment stored in the C<$json> object.
+
+After that, if the function is called in void context, it will simply
+return without doing anything further. This can be used to add more text
+in as many chunks as you want.
+
+If the method is called in scalar context, then it will try to extract
+exactly I<one> JSON object. If that is successful, it will return this
+object, otherwise it will return C<undef>. If there is a parse error,
+this method will croak just as C<decode> would do (one can then use
+C<incr_skip> to skip the errornous part). This is the most common way of
+using the method.
+
+And finally, in list context, it will try to extract as many objects
+from the stream as it can find and return them, or the empty list
+otherwise. For this to work, there must be no separators between the JSON
+objects or arrays, instead they must be concatenated back-to-back. If
+an error occurs, an exception will be raised as in the scalar context
+case. Note that in this case, any previously-parsed JSON texts will be
+lost.
+
+Example: Parse some JSON arrays/objects in a given string and return them.
+
+    my @objs = JSON->new->incr_parse ("[5][7][1,2]");
+
+=head2 incr_text
+
+    $lvalue_string = $json->incr_text
+
+This method returns the currently stored JSON fragment as an lvalue, that
+is, you can manipulate it. This I<only> works when a preceding call to
+C<incr_parse> in I<scalar context> successfully returned an object. Under
+all other circumstances you must not call this function (I mean it.
+although in simple tests it might actually work, it I<will> fail under
+real world conditions). As a special exception, you can also call this
+method before having parsed anything.
+
+This function is useful in two cases: a) finding the trailing text after a
+JSON object or b) parsing multiple JSON objects separated by non-JSON text
+(such as commas).
+
+    $json->incr_text =~ s/\s*,\s*//;
+
+In Perl 5.005, C<lvalue> attribute is not available.
+You must write codes like the below:
+
+    $string = $json->incr_text;
+    $string =~ s/\s*,\s*//;
+    $json->incr_text( $string );
+
+=head2 incr_skip
+
+    $json->incr_skip
+
+This will reset the state of the incremental parser and will remove the
+parsed text from the input buffer. This is useful after C<incr_parse>
+died, in which case the input buffer and incremental parser state is left
+unchanged, to skip the text parsed so far and to reset the parse state.
+
+=head2 incr_reset
+
+    $json->incr_reset
+
+This completely resets the incremental parser, that is, after this call,
+it will be as if the parser had never parsed anything.
+
+This is useful if you want ot repeatedly parse JSON objects and want to
+ignore any trailing data, which means you have to reset the parser after
+each successful decode.
+
+See to L<JSON::XS/INCREMENTAL PARSING> for examples.
+
+
+=head1 JSON::PP SUPPORT METHODS
+
+The below methods are JSON::PP own methods, so when C<JSON> works
+with JSON::PP (i.e. the created object is a JSON::PP object), available.
+See to L<JSON::PP/JSON::PP OWN METHODS> in detail.
+
+If you use C<JSON> with additonal C<-support_by_pp>, some methods
+are available even with JSON::XS. See to L<USE PP FEATURES EVEN THOUGH XS BACKEND>.
+
+   BEING { $ENV{PERL_JSON_BACKEND} = 'JSON::XS' }
+   
+   use JSON -support_by_pp;
+   
+   my $json = new JSON;
+   $json->allow_nonref->escape_slash->encode("/");
+
+   # functional interfaces too.
+   print to_json(["/"], {escape_slash => 1});
+   print from_json('["foo"]', {utf8 => 1});
+
+If you do not want to all functions but C<-support_by_pp>,
+use C<-no_export>.
+
+   use JSON -support_by_pp, -no_export;
+   # functional interfaces are not exported.
+
+=head2 allow_singlequote
+
+    $json = $json->allow_singlequote([$enable])
+
+If C<$enable> is true (or missing), then C<decode> will accept
+any JSON strings quoted by single quotations that are invalid JSON
+format.
+
+    $json->allow_singlequote->decode({"foo":'bar'});
+    $json->allow_singlequote->decode({'foo':"bar"});
+    $json->allow_singlequote->decode({'foo':'bar'});
+
+As same as the C<relaxed> option, this option may be used to parse
+application-specific files written by humans.
+
+=head2 allow_barekey
+
+    $json = $json->allow_barekey([$enable])
+
+If C<$enable> is true (or missing), then C<decode> will accept
+bare keys of JSON object that are invalid JSON format.
+
+As same as the C<relaxed> option, this option may be used to parse
+application-specific files written by humans.
+
+    $json->allow_barekey->decode('{foo:"bar"}');
+
+=head2 allow_bignum
+
+    $json = $json->allow_bignum([$enable])
+
+If C<$enable> is true (or missing), then C<decode> will convert
+the big integer Perl cannot handle as integer into a L<Math::BigInt>
+object and convert a floating number (any) into a L<Math::BigFloat>.
+
+On the contary, C<encode> converts C<Math::BigInt> objects and C<Math::BigFloat>
+objects into JSON numbers with C<allow_blessed> enable.
+
+   $json->allow_nonref->allow_blessed->allow_bignum;
+   $bigfloat = $json->decode('2.000000000000000000000000001');
+   print $json->encode($bigfloat);
+   # => 2.000000000000000000000000001
+
+See to L<MAPPING> aboout the conversion of JSON number.
+
+=head2 loose
+
+    $json = $json->loose([$enable])
+
+The unescaped [\x00-\x1f\x22\x2f\x5c] strings are invalid in JSON strings
+and the module doesn't allow to C<decode> to these (except for \x2f).
+If C<$enable> is true (or missing), then C<decode>  will accept these
+unescaped strings.
+
+    $json->loose->decode(qq|["abc
+                                   def"]|);
+
+See to L<JSON::PP/JSON::PP OWN METHODS>.
+
+=head2 escape_slash
+
+    $json = $json->escape_slash([$enable])
+
+According to JSON Grammar, I<slash> (U+002F) is escaped. But by default
+JSON backend modules encode strings without escaping slash.
+
+If C<$enable> is true (or missing), then C<encode> will escape slashes.
+
+=head2 indent_length
+
+    $json = $json->indent_length($length)
+
+With JSON::XS, The indent space length is 3 and cannot be changed.
+With JSON::PP, it sets the indent space length with the given $length.
+The default is 3. The acceptable range is 0 to 15.
+
+=head2 sort_by
+
+    $json = $json->sort_by($function_name)
+    $json = $json->sort_by($subroutine_ref)
+
+If $function_name or $subroutine_ref are set, its sort routine are used.
+
+   $js = $pc->sort_by(sub { $JSON::PP::a cmp $JSON::PP::b })->encode($obj);
+   # is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);
+
+   $js = $pc->sort_by('own_sort')->encode($obj);
+   # is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);
+
+   sub JSON::PP::own_sort { $JSON::PP::a cmp $JSON::PP::b }
+
+As the sorting routine runs in the JSON::PP scope, the given
+subroutine name and the special variables C<$a>, C<$b> will begin
+with 'JSON::PP::'.
+
+If $integer is set, then the effect is same as C<canonical> on.
+
+See to L<JSON::PP/JSON::PP OWN METHODS>.
+
+=head1 MAPPING
+
+This section is copied from JSON::XS and modified to C<JSON>.
+JSON::XS and JSON::PP mapping mechanisms are almost equivalent.
+
+See to L<JSON::XS/MAPPING>.
+
+=head2 JSON -> PERL
+
+=over 4
+
+=item object
+
+A JSON object becomes a reference to a hash in Perl. No ordering of object
+keys is preserved (JSON does not preserver object key ordering itself).
+
+=item array
+
+A JSON array becomes a reference to an array in Perl.
+
+=item string
+
+A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
+are represented by the same codepoints in the Perl string, so no manual
+decoding is necessary.
+
+=item number
+
+A JSON number becomes either an integer, numeric (floating point) or
+string scalar in perl, depending on its range and any fractional parts. On
+the Perl level, there is no difference between those as Perl handles all
+the conversion details, but an integer may take slightly less memory and
+might represent more values exactly than floating point numbers.
+
+If the number consists of digits only, C<JSON> will try to represent
+it as an integer value. If that fails, it will try to represent it as
+a numeric (floating point) value if that is possible without loss of
+precision. Otherwise it will preserve the number as a string value (in
+which case you lose roundtripping ability, as the JSON number will be
+re-encoded toa JSON string).
+
+Numbers containing a fractional or exponential part will always be
+represented as numeric (floating point) values, possibly at a loss of
+precision (in which case you might lose perfect roundtripping ability, but
+the JSON number will still be re-encoded as a JSON number).
+
+Note that precision is not accuracy - binary floating point values cannot
+represent most decimal fractions exactly, and when converting from and to
+floating point, C<JSON> only guarantees precision up to but not including
+the leats significant bit.
+
+If the backend is JSON::PP and C<allow_bignum> is enable, the big integers 
+and the numeric can be optionally converted into L<Math::BigInt> and
+L<Math::BigFloat> objects.
+
+=item true, false
+
+These JSON atoms become C<JSON::true> and C<JSON::false>,
+respectively. They are overloaded to act almost exactly like the numbers
+C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
+the C<JSON::is_bool> function.
+
+If C<JSON::true> and C<JSON::false> are used as strings or compared as strings,
+they represent as C<true> and C<false> respectively.
+
+   print JSON::true . "\n";
+    => true
+   print JSON::true + 1;
+    => 1
+
+   ok(JSON::true eq 'true');
+   ok(JSON::true eq  '1');
+   ok(JSON::true == 1);
+
+C<JSON> will install these missing overloading features to the backend modules.
+
+
+=item null
+
+A JSON null atom becomes C<undef> in Perl.
+
+C<JSON::null> returns C<unddef>.
+
+=back
+
+
+=head2 PERL -> JSON
+
+The mapping from Perl to JSON is slightly more difficult, as Perl is a
+truly typeless language, so we can only guess which JSON type is meant by
+a Perl value.
+
+=over 4
+
+=item hash references
+
+Perl hash references become JSON objects. As there is no inherent ordering
+in hash keys (or JSON objects), they will usually be encoded in a
+pseudo-random order that can change between runs of the same program but
+stays generally the same within a single run of a program. C<JSON>
+optionally sort the hash keys (determined by the I<canonical> flag), so
+the same datastructure will serialise to the same JSON text (given same
+settings and version of JSON::XS), but this incurs a runtime overhead
+and is only rarely useful, e.g. when you want to compare some JSON text
+against another for equality.
+
+In future, the ordered object feature will be added to JSON::PP using C<tie> mechanism.
+
+
+=item array references
+
+Perl array references become JSON arrays.
+
+=item other references
+
+Other unblessed references are generally not allowed and will cause an
+exception to be thrown, except for references to the integers C<0> and
+C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
+also use C<JSON::false> and C<JSON::true> to improve readability.
+
+   to_json [\0,JSON::true]      # yields [false,true]
+
+=item JSON::true, JSON::false, JSON::null
+
+These special values become JSON true and JSON false values,
+respectively. You can also use C<\1> and C<\0> directly if you want.
+
+JSON::null returns C<undef>.
+
+=item blessed objects
+
+Blessed objects are not directly representable in JSON. See the
+C<allow_blessed> and C<convert_blessed> methods on various options on
+how to deal with this: basically, you can choose between throwing an
+exception, encoding the reference as if it weren't blessed, or provide
+your own serialiser method.
+
+With C<convert_blessed_universally> mode,  C<encode> converts blessed
+hash references or blessed array references (contains other blessed references)
+into JSON members and arrays.
+
+   use JSON -convert_blessed_universally;
+   JSON->new->allow_blessed->convert_blessed->encode( $blessed_object );
+
+See to L<convert_blessed>.
+
+=item simple scalars
+
+Simple Perl scalars (any scalar that is not a reference) are the most
+difficult objects to encode: JSON::XS and JSON::PP will encode undefined scalars as
+JSON C<null> values, scalars that have last been used in a string context
+before encoding as JSON strings, and anything else as number value:
+
+   # dump as number
+   encode_json [2]                      # yields [2]
+   encode_json [-3.0e17]                # yields [-3e+17]
+   my $value = 5; encode_json [$value]  # yields [5]
+
+   # used as string, so dump as string
+   print $value;
+   encode_json [$value]                 # yields ["5"]
+
+   # undef becomes null
+   encode_json [undef]                  # yields [null]
+
+You can force the type to be a string by stringifying it:
+
+   my $x = 3.1; # some variable containing a number
+   "$x";        # stringified
+   $x .= "";    # another, more awkward way to stringify
+   print $x;    # perl does it for you, too, quite often
+
+You can force the type to be a number by numifying it:
+
+   my $x = "3"; # some variable containing a string
+   $x += 0;     # numify it, ensuring it will be dumped as a number
+   $x *= 1;     # same thing, the choise is yours.
+
+You can not currently force the type in other, less obscure, ways.
+
+Note that numerical precision has the same meaning as under Perl (so
+binary to decimal conversion follows the same rules as in Perl, which
+can differ to other languages). Also, your perl interpreter might expose
+extensions to the floating point numbers of your platform, such as
+infinities or NaN's - these cannot be represented in JSON, and it is an
+error to pass those in.
+
+=item Big Number
+
+If the backend is JSON::PP and C<allow_bignum> is enable, 
+C<encode> converts C<Math::BigInt> objects and C<Math::BigFloat>
+objects into JSON numbers.
+
+
+=back
+
+=head1 JSON and ECMAscript
+
+See to L<JSON::XS/JSON and ECMAscript>.
+
+=head1 JSON and YAML
+
+JSON is not a subset of YAML.
+See to L<JSON::XS/JSON and YAML>.
+
+
+=head1 BACKEND MODULE DECISION
+
+When you use C<JSON>, C<JSON> tries to C<use> JSON::XS. If this call failed, it will
+C<uses> JSON::PP. The required JSON::XS version is I<2.2> or later.
+
+The C<JSON> constructor method returns an object inherited from the backend module,
+and JSON::XS object is a blessed scaler reference while JSON::PP is a blessed hash
+reference.
+
+So, your program should not depend on the backend module, especially
+returned objects should not be modified.
+
+ my $json = JSON->new; # XS or PP?
+ $json->{stash} = 'this is xs object'; # this code may raise an error!
+
+To check the backend module, there are some methods - C<backend>, C<is_pp> and C<is_xs>.
+
+  JSON->backend; # 'JSON::XS' or 'JSON::PP'
+  
+  JSON->backend->is_pp: # 0 or 1
+  
+  JSON->backend->is_xs: # 1 or 0
+  
+  $json->is_xs; # 1 or 0
+  
+  $json->is_pp; # 0 or 1
+
+
+If you set an enviornment variable C<PERL_JSON_BACKEND>, The calling action will be changed.
+
+=over
+
+=item PERL_JSON_BACKEND = 0 or PERL_JSON_BACKEND = 'JSON::PP'
+
+Always use JSON::PP
+
+=item PERL_JSON_BACKEND == 1 or PERL_JSON_BACKEND = 'JSON::XS,JSON::PP'
+
+(The default) Use compiled JSON::XS if it is properly compiled & installed,
+otherwise use JSON::PP.
+
+=item PERL_JSON_BACKEND == 2 or PERL_JSON_BACKEND = 'JSON::XS'
+
+Always use compiled JSON::XS, die if it isn't properly compiled & installed.
+
+=back
+
+These ideas come from L<DBI::PurePerl> mechanism.
+
+example:
+
+ BEGIN { $ENV{PERL_JSON_BACKEND} = 'JSON::PP' }
+ use JSON; # always uses JSON::PP
+
+In future, it may be able to specify another module.
+
+=head1 USE PP FEATURES EVEN THOUGH XS BACKEND
+
+Many methods are available with either JSON::XS or JSON::PP and
+when the backend module is JSON::XS, if any JSON::PP specific (i.e. JSON::XS unspported)
+method is called, it will C<warn> and be noop.
+
+But If you C<use> C<JSON> passing the optional string C<-support_by_pp>,
+it makes a part of those unupported methods available.
+This feature is achieved by using JSON::PP in C<de/encode>.
+
+   BEGIN { $ENV{PERL_JSON_BACKEND} = 2 } # with JSON::XS
+   use JSON -support_by_pp;
+   my $json = new JSON;
+   $json->allow_nonref->escape_slash->encode("/");
+
+At this time, the returned object is a C<JSON::Backend::XS::Supportable>
+object (re-blessed XS object), and  by checking JSON::XS unsupported flags
+in de/encoding, can support some unsupported methods - C<loose>, C<allow_bignum>,
+C<allow_barekey>, C<allow_singlequote>, C<escape_slash> and C<indent_length>.
+
+When any unsupported methods are not enable, C<XS de/encode> will be
+used as is. The switch is achieved by changing the symbolic tables.
+
+C<-support_by_pp> is effective only when the backend module is JSON::XS
+and it makes the de/encoding speed down a bit.
+
+See to L<JSON::PP SUPPORT METHODS>.
+
+=head1 INCOMPATIBLE CHANGES TO OLD VERSION
+
+There are big incompatibility between new version (2.00) and old (1.xx).
+If you use old C<JSON> 1.xx in your code, please check it.
+
+See to L<Transition ways from 1.xx to 2.xx.>
+
+=over
+
+=item jsonToObj and objToJson are obsoleted.
+
+Non Perl-style name C<jsonToObj> and C<objToJson> are obsoleted
+(but not yet deleted from the source).
+If you use these functions in your code, please replace them
+with C<from_json> and C<to_json>.
+
+
+=item Global variables are no longer available.
+
+C<JSON> class variables - C<$JSON::AUTOCONVERT>, C<$JSON::BareKey>, etc...
+- are not available any longer.
+Instead, various features can be used through object methods.
+
+
+=item Package JSON::Converter and JSON::Parser are deleted.
+
+Now C<JSON> bundles with JSON::PP which can handle JSON more properly than them.
+
+=item Package JSON::NotString is deleted.
+
+There was C<JSON::NotString> class which represents JSON value C<true>, C<false>, C<null>
+and numbers. It was deleted and replaced by C<JSON::Boolean>.
+
+C<JSON::Boolean> represents C<true> and C<false>.
+
+C<JSON::Boolean> does not represent C<null>.
+
+C<JSON::null> returns C<undef>.
+
+C<JSON> makes L<JSON::XS::Boolean> and L<JSON::PP::Boolean> is-a relation
+to L<JSON::Boolean>.
+
+=item function JSON::Number is obsoleted.
+
+C<JSON::Number> is now needless because JSON::XS and JSON::PP have
+round-trip integrity.
+
+=item JSONRPC modules are deleted.
+
+Perl implementation of JSON-RPC protocol - C<JSONRPC >, C<JSONRPC::Transport::HTTP>
+and C<Apache::JSONRPC > are deleted in this distribution.
+Instead of them, there is L<JSON::RPC> which supports JSON-RPC protocol version 1.1.
+
+=back
+
+=head2 Transition ways from 1.xx to 2.xx.
+
+You should set C<suport_by_pp> mode firstly, because
+it is always successful for the below codes even with JSON::XS.
+
+    use JSON -support_by_pp;
+
+=over
+
+=item Exported jsonToObj (simple)
+
+  from_json($json_text);
+
+=item Exported objToJson (simple)
+
+  to_json($perl_scalar);
+
+=item Exported jsonToObj (advanced)
+
+  $flags = {allow_barekey => 1, allow_singlequote => 1};
+  from_json($json_text, $flags);
+
+equivalent to:
+
+  $JSON::BareKey = 1;
+  $JSON::QuotApos = 1;
+  jsonToObj($json_text);
+
+=item Exported objToJson (advanced)
+
+  $flags = {allow_blessed => 1, allow_barekey => 1};
+  to_json($perl_scalar, $flags);
+
+equivalent to:
+
+  $JSON::BareKey = 1;
+  objToJson($perl_scalar);
+
+=item jsonToObj as object method
+
+  $json->decode($json_text);
+
+=item objToJson as object method
+
+  $json->encode($perl_scalar);
+
+=item new method with parameters
+
+The C<new> method in 2.x takes any parameters no longer.
+You can set parameters instead;
+
+   $json = JSON->new->pretty;
+
+=item $JSON::Pretty, $JSON::Indent, $JSON::Delimiter
+
+If C<indent> is enable, that menas C<$JSON::Pretty> flag set. And
+C<$JSON::Delimiter> was substituted by C<space_before> and C<space_after>.
+In conclusion:
+
+   $json->indent->space_before->space_after;
+
+Equivalent to:
+
+  $json->pretty;
+
+To change indent length, use C<indent_length>.
+
+(Only with JSON::PP, if C<-support_by_pp> is not used.)
+
+  $json->pretty->indent_length(2)->encode($perl_scalar);
+
+=item $JSON::BareKey
+
+(Only with JSON::PP, if C<-support_by_pp> is not used.)
+
+  $json->allow_barekey->decode($json_text)
+
+=item $JSON::ConvBlessed
+
+use C<-convert_blessed_universally>. See to L<convert_blessed>.
+
+=item $JSON::QuotApos
+
+(Only with JSON::PP, if C<-support_by_pp> is not used.)
+
+  $json->allow_singlequote->decode($json_text)
+
+=item $JSON::SingleQuote
+
+Disable. C<JSON> does not make such a invalid JSON string any longer.
+
+=item $JSON::KeySort
+
+  $json->canonical->encode($perl_scalar)
+
+This is the ascii sort.
+
+If you want to use with your own sort routine, check the C<sort_by> method.
+
+(Only with JSON::PP, even if C<-support_by_pp> is used currently.)
+
+  $json->sort_by($sort_routine_ref)->encode($perl_scalar)
+ 
+  $json->sort_by(sub { $JSON::PP::a <=> $JSON::PP::b })->encode($perl_scalar)
+
+Can't access C<$a> and C<$b> but C<$JSON::PP::a> and C<$JSON::PP::b>.
+
+=item $JSON::SkipInvalid
+
+  $json->allow_unknown
+
+=item $JSON::AUTOCONVERT
+
+Needless. C<JSON> backend modules have the round-trip integrity.
+
+=item $JSON::UTF8
+
+Needless because C<JSON> (JSON::XS/JSON::PP) sets
+the UTF8 flag on properly.
+
+    # With UTF8-flagged strings
+
+    $json->allow_nonref;
+    $str = chr(1000); # UTF8-flagged
+
+    $json_text  = $json->utf8(0)->encode($str);
+    utf8::is_utf8($json_text);
+    # true
+    $json_text  = $json->utf8(1)->encode($str);
+    utf8::is_utf8($json_text);
+    # false
+
+    $str = '"' . chr(1000) . '"'; # UTF8-flagged
+
+    $perl_scalar  = $json->utf8(0)->decode($str);
+    utf8::is_utf8($perl_scalar);
+    # true
+    $perl_scalar  = $json->utf8(1)->decode($str);
+    # died because of 'Wide character in subroutine'
+
+See to L<JSON::XS/A FEW NOTES ON UNICODE AND PERL>.
+
+=item $JSON::UnMapping
+
+Disable. See to L<MAPPING>.
+
+=item $JSON::SelfConvert
+
+This option was deleted.
+Instead of it, if a givien blessed object has the C<TO_JSON> method,
+C<TO_JSON> will be executed with C<convert_blessed>.
+
+  $json->convert_blessed->encode($bleesed_hashref_or_arrayref)
+  # if need, call allow_blessed
+
+Note that it was C<toJson> in old version, but now not C<toJson> but C<TO_JSON>.
+
+=back
+
+=head1 TODO
+
+=over
+
+=item example programs
+
+=back
+
+=head1 THREADS
+
+No test with JSON::PP. If with JSON::XS, See to L<JSON::XS/THREADS>.
+
+
+=head1 BUGS
+
+Please report bugs relevant to C<JSON> to E<lt>makamaka[at]cpan.orgE<gt>.
+
+
+=head1 SEE ALSO
+
+Most of the document is copied and modified from JSON::XS doc.
+
+L<JSON::XS>, L<JSON::PP>
+
+C<RFC4627>(L<http://www.ietf.org/rfc/rfc4627.txt>)
+
+=head1 AUTHOR
+
+Makamaka Hannyaharamitu, E<lt>makamaka[at]cpan.orgE<gt>
+
+JSON::XS was written by  Marc Lehmann <schmorp[at]schmorp.de>
+
+The relese of this new version owes to the courtesy of Marc Lehmann.
+
+
+=head1 COPYRIGHT AND LICENSE
+
+Copyright 2005-2010 by Makamaka Hannyaharamitu
+
+This library is free software; you can redistribute it and/or modify
+it under the same terms as Perl itself. 
+
+=cut
+


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