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.\" ========================================================================
.\"
.IX Title "JSON::backportPP 3"
.TH JSON::backportPP 3 "2013-05-23" "perl v5.16.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
JSON::PP \- JSON::XS compatible pure\-Perl module.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& use JSON::PP;
\&
\& # exported functions, they croak on error
\& # and 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
\&
\& $coder = JSON::PP\->new\->ascii\->pretty\->allow_nonref;
\& 
\& $json_text   = $json\->encode( $perl_scalar );
\& $perl_scalar = $json\->decode( $json_text );
\& 
\& $pretty_printed = $json\->pretty\->encode( $perl_scalar ); # pretty\-printing
\& 
\& # Note that JSON version 2.0 and above will automatically use
\& # JSON::XS or JSON::PP, so you should be able to just:
\& 
\& use JSON;
.Ve
.SH "VERSION"
.IX Header "VERSION"
.Vb 1
\&    2.27200
.Ve
.PP
\&\s-1JSON::XS\s0 2.27 (~2.30) compatible.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module is \s-1JSON::XS\s0 compatible pure Perl module.
(Perl 5.8 or later is recommended)
.PP
\&\s-1JSON::XS\s0 is the fastest and most proper \s-1JSON\s0 module on \s-1CPAN.\s0
It is written by Marc Lehmann in C, so must be compiled and
installed in the used environment.
.PP
\&\s-1JSON::PP\s0 is a pure-Perl module and has compatibility to \s-1JSON::XS.\s0
.SS "\s-1FEATURES\s0"
.IX Subsection "FEATURES"
.IP "\(bu" 4
correct unicode handling
.Sp
This module knows how to handle Unicode (depending on Perl version).
.Sp
See to \*(L"A \s-1FEW NOTES ON UNICODE AND PERL\*(R"\s0 in \s-1JSON::XS\s0 and
\&\*(L"\s-1UNICODE HANDLING ON PERLS\*(R"\s0.
.IP "\(bu" 4
round-trip integrity
.Sp
When you serialise a perl data structure using only data types
supported by \s-1JSON\s0 and Perl, the deserialised data structure is
identical on the Perl level. (e.g. the string \*(L"2.0\*(R" doesn't suddenly
become \*(L"2\*(R" just because it looks like a number). There \fIare\fR minor
exceptions to this, read the \s-1MAPPING\s0 section below to learn about
those.
.IP "\(bu" 4
strict checking of \s-1JSON\s0 correctness
.Sp
There is no guessing, no generating of illegal \s-1JSON\s0 texts by default,
and only \s-1JSON\s0 is accepted as input by default (the latter is a
security feature). But when some options are set, loose checking
features are available.
.SH "FUNCTIONAL INTERFACE"
.IX Header "FUNCTIONAL INTERFACE"
Some documents are copied and modified from \*(L"\s-1FUNCTIONAL INTERFACE\*(R"\s0 in \s-1JSON::XS\s0.
.SS "encode_json"
.IX Subsection "encode_json"
.Vb 1
\&    $json_text = encode_json $perl_scalar
.Ve
.PP
Converts the given Perl data structure to a \s-1UTF\-8\s0 encoded, binary string.
.PP
This function call is functionally identical to:
.PP
.Vb 1
\&    $json_text = JSON::PP\->new\->utf8\->encode($perl_scalar)
.Ve
.SS "decode_json"
.IX Subsection "decode_json"
.Vb 1
\&    $perl_scalar = decode_json $json_text
.Ve
.PP
The opposite of \f(CW\*(C`encode_json\*(C'\fR: expects an \s-1UTF\-8 \s0(binary) string and tries
to parse that as an \s-1UTF\-8\s0 encoded \s-1JSON\s0 text, returning the resulting
reference.
.PP
This function call is functionally identical to:
.PP
.Vb 1
\&    $perl_scalar = JSON::PP\->new\->utf8\->decode($json_text)
.Ve
.SS "JSON::PP::is_bool"
.IX Subsection "JSON::PP::is_bool"
.Vb 1
\&    $is_boolean = JSON::PP::is_bool($scalar)
.Ve
.PP
Returns true if the passed scalar represents either JSON::PP::true or
JSON::PP::false, two constants that act like \f(CW1\fR and \f(CW0\fR respectively
and are also used to represent \s-1JSON \s0\f(CW\*(C`true\*(C'\fR and \f(CW\*(C`false\*(C'\fR in Perl strings.
.SS "JSON::PP::true"
.IX Subsection "JSON::PP::true"
Returns \s-1JSON\s0 true value which is blessed object.
It \f(CW\*(C`isa\*(C'\fR JSON::PP::Boolean object.
.SS "JSON::PP::false"
.IX Subsection "JSON::PP::false"
Returns \s-1JSON\s0 false value which is blessed object.
It \f(CW\*(C`isa\*(C'\fR JSON::PP::Boolean object.
.SS "JSON::PP::null"
.IX Subsection "JSON::PP::null"
Returns \f(CW\*(C`undef\*(C'\fR.
.PP
See \s-1MAPPING\s0, below, for more information on how \s-1JSON\s0 values are mapped to
Perl.
.SH "HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER"
.IX Header "HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER"
This section supposes that your perl version is 5.8 or later.
.PP
If you know a \s-1JSON\s0 text from an outer world \- a network, a file content, and so on,
is encoded in \s-1UTF\-8,\s0 you should use \f(CW\*(C`decode_json\*(C'\fR or \f(CW\*(C`JSON\*(C'\fR module object
with \f(CW\*(C`utf8\*(C'\fR enable. And the decoded result will contain \s-1UNICODE\s0 characters.
.PP
.Vb 4
\&  # from network
\&  my $json        = JSON::PP\->new\->utf8;
\&  my $json_text   = CGI\->new\->param( \*(Aqjson_data\*(Aq );
\&  my $perl_scalar = $json\->decode( $json_text );
\&  
\&  # from file content
\&  local $/;
\&  open( my $fh, \*(Aq<\*(Aq, \*(Aqjson.data\*(Aq );
\&  $json_text   = <$fh>;
\&  $perl_scalar = decode_json( $json_text );
.Ve
.PP
If an outer data is not encoded in \s-1UTF\-8,\s0 firstly you should \f(CW\*(C`decode\*(C'\fR it.
.PP
.Vb 5
\&  use Encode;
\&  local $/;
\&  open( my $fh, \*(Aq<\*(Aq, \*(Aqjson.data\*(Aq );
\&  my $encoding = \*(Aqcp932\*(Aq;
\&  my $unicode_json_text = decode( $encoding, <$fh> ); # UNICODE
\&  
\&  # or you can write the below code.
\&  #
\&  # open( my $fh, "<:encoding($encoding)", \*(Aqjson.data\*(Aq );
\&  # $unicode_json_text = <$fh>;
.Ve
.PP
In this case, \f(CW$unicode_json_text\fR is of course \s-1UNICODE\s0 string.
So you \fBcannot\fR use \f(CW\*(C`decode_json\*(C'\fR nor \f(CW\*(C`JSON\*(C'\fR module object with \f(CW\*(C`utf8\*(C'\fR enable.
Instead of them, you use \f(CW\*(C`JSON\*(C'\fR module object with \f(CW\*(C`utf8\*(C'\fR disable.
.PP
.Vb 1
\&  $perl_scalar = $json\->utf8(0)\->decode( $unicode_json_text );
.Ve
.PP
Or \f(CW\*(C`encode \*(Aqutf8\*(Aq\*(C'\fR and \f(CW\*(C`decode_json\*(C'\fR:
.PP
.Vb 2
\&  $perl_scalar = decode_json( encode( \*(Aqutf8\*(Aq, $unicode_json_text ) );
\&  # this way is not efficient.
.Ve
.PP
And now, you want to convert your \f(CW$perl_scalar\fR into \s-1JSON\s0 data and
send it to an outer world \- a network or a file content, and so on.
.PP
Your data usually contains \s-1UNICODE\s0 strings and you want the converted data to be encoded
in \s-1UTF\-8,\s0 you should use \f(CW\*(C`encode_json\*(C'\fR or \f(CW\*(C`JSON\*(C'\fR module object with \f(CW\*(C`utf8\*(C'\fR enable.
.PP
.Vb 3
\&  print encode_json( $perl_scalar ); # to a network? file? or display?
\&  # or
\&  print $json\->utf8\->encode( $perl_scalar );
.Ve
.PP
If \f(CW$perl_scalar\fR does not contain \s-1UNICODE\s0 but \f(CW$encoding\fR\-encoded strings
for some reason, then its characters are regarded as \fBlatin1\fR for perl
(because it does not concern with your \f(CW$encoding\fR).
You \fBcannot\fR use \f(CW\*(C`encode_json\*(C'\fR nor \f(CW\*(C`JSON\*(C'\fR module object with \f(CW\*(C`utf8\*(C'\fR enable.
Instead of them, you use \f(CW\*(C`JSON\*(C'\fR module object with \f(CW\*(C`utf8\*(C'\fR disable.
Note that the resulted text is a \s-1UNICODE\s0 string but no problem to print it.
.PP
.Vb 4
\&  # $perl_scalar contains $encoding encoded string values
\&  $unicode_json_text = $json\->utf8(0)\->encode( $perl_scalar );
\&  # $unicode_json_text consists of characters less than 0x100
\&  print $unicode_json_text;
.Ve
.PP
Or \f(CW\*(C`decode $encoding\*(C'\fR all string values and \f(CW\*(C`encode_json\*(C'\fR:
.PP
.Vb 3
\&  $perl_scalar\->{ foo } = decode( $encoding, $perl_scalar\->{ foo } );
\&  # ... do it to each string values, then encode_json
\&  $json_text = encode_json( $perl_scalar );
.Ve
.PP
This method is a proper way but probably not efficient.
.PP
See to Encode, perluniintro.
.SH "METHODS"
.IX Header "METHODS"
Basically, check to \s-1JSON\s0 or \s-1JSON::XS\s0.
.SS "new"
.IX Subsection "new"
.Vb 1
\&    $json = JSON::PP\->new
.Ve
.PP
Returns a new \s-1JSON::PP\s0 object that can be used to de/encode \s-1JSON\s0
strings.
.PP
All boolean flags described below are by default \fIdisabled\fR.
.PP
The mutators for flags all return the \s-1JSON\s0 object again and thus calls can
be chained:
.PP
.Vb 2
\&   my $json = JSON::PP\->new\->utf8\->space_after\->encode({a => [1,2]})
\&   => {"a": [1, 2]}
.Ve
.SS "ascii"
.IX Subsection "ascii"
.Vb 1
\&    $json = $json\->ascii([$enable])
\&    
\&    $enabled = $json\->get_ascii
.Ve
.PP
If \f(CW$enable\fR 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 \euXXXX or a double \euHHHH\euLLLLL escape sequence, as per \s-1RFC4627.
\&\s0(See to \*(L"OBJECT-ORIENTED \s-1INTERFACE\*(R"\s0 in \s-1JSON::XS\s0).
.PP
In Perl 5.005, there is no character having high value (more than 255).
See to \*(L"\s-1UNICODE HANDLING ON PERLS\*(R"\s0.
.PP
If \f(CW$enable\fR is false, then the encode method will not escape Unicode characters unless
required by the \s-1JSON\s0 syntax or other flags. This results in a faster and more compact format.
.PP
.Vb 2
\&  JSON::PP\->new\->ascii(1)\->encode([chr 0x10401])
\&  => ["\eud801\eudc01"]
.Ve
.SS "latin1"
.IX Subsection "latin1"
.Vb 1
\&    $json = $json\->latin1([$enable])
\&    
\&    $enabled = $json\->get_latin1
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then the encode method will encode the resulting \s-1JSON\s0
text as latin1 (or iso\-8859\-1), escaping any characters outside the code range 0..255.
.PP
If \f(CW$enable\fR is false, then the encode method will not escape Unicode characters
unless required by the \s-1JSON\s0 syntax or other flags.
.PP
.Vb 2
\&  JSON::XS\->new\->latin1\->encode (["\ex{89}\ex{abc}"]
\&  => ["\ex{89}\e\eu0abc"]    # (perl syntax, U+abc escaped, U+89 not)
.Ve
.PP
See to \*(L"\s-1UNICODE HANDLING ON PERLS\*(R"\s0.
.SS "utf8"
.IX Subsection "utf8"
.Vb 1
\&    $json = $json\->utf8([$enable])
\&    
\&    $enabled = $json\->get_utf8
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then the encode method will encode the \s-1JSON\s0 result
into \s-1UTF\-8,\s0 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.
.PP
(In Perl 5.005, any character outside the range 0..255 does not exist.
See to \*(L"\s-1UNICODE HANDLING ON PERLS\*(R"\s0.)
.PP
In future versions, enabling this option might enable autodetection of the \s-1UTF\-16\s0 and \s-1UTF\-32\s0
encoding families, as described in \s-1RFC4627.\s0
.PP
If \f(CW$enable\fR is false, then the encode method will return the \s-1JSON\s0 string as a (non-encoded)
Unicode string, while decode expects thus a Unicode string. Any decoding or encoding
(e.g. to \s-1UTF\-8\s0 or \s-1UTF\-16\s0) needs to be done yourself, e.g. using the Encode module.
.PP
Example, output UTF\-16BE\-encoded \s-1JSON:\s0
.PP
.Vb 2
\&  use Encode;
\&  $jsontext = encode "UTF\-16BE", JSON::PP\->new\->encode ($object);
.Ve
.PP
Example, decode UTF\-32LE\-encoded \s-1JSON:\s0
.PP
.Vb 2
\&  use Encode;
\&  $object = JSON::PP\->new\->decode (decode "UTF\-32LE", $jsontext);
.Ve
.SS "pretty"
.IX Subsection "pretty"
.Vb 1
\&    $json = $json\->pretty([$enable])
.Ve
.PP
This enables (or disables) all of the \f(CW\*(C`indent\*(C'\fR, \f(CW\*(C`space_before\*(C'\fR and
\&\f(CW\*(C`space_after\*(C'\fR flags in one call to generate the most readable
(or most compact) form possible.
.PP
Equivalent to:
.PP
.Vb 1
\&   $json\->indent\->space_before\->space_after
.Ve
.SS "indent"
.IX Subsection "indent"
.Vb 1
\&    $json = $json\->indent([$enable])
\&    
\&    $enabled = $json\->get_indent
.Ve
.PP
The default indent space length is three.
You can use \f(CW\*(C`indent_length\*(C'\fR to change the length.
.SS "space_before"
.IX Subsection "space_before"
.Vb 1
\&    $json = $json\->space_before([$enable])
\&    
\&    $enabled = $json\->get_space_before
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then the \f(CW\*(C`encode\*(C'\fR method will add an extra
optional space before the \f(CW\*(C`:\*(C'\fR separating keys from values in \s-1JSON\s0 objects.
.PP
If \f(CW$enable\fR is false, then the \f(CW\*(C`encode\*(C'\fR method will not add any extra
space at those places.
.PP
This setting has no effect when decoding \s-1JSON\s0 texts.
.PP
Example, space_before enabled, space_after and indent disabled:
.PP
.Vb 1
\&   {"key" :"value"}
.Ve
.SS "space_after"
.IX Subsection "space_after"
.Vb 1
\&    $json = $json\->space_after([$enable])
\&    
\&    $enabled = $json\->get_space_after
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then the \f(CW\*(C`encode\*(C'\fR method will add an extra
optional space after the \f(CW\*(C`:\*(C'\fR separating keys from values in \s-1JSON\s0 objects
and extra whitespace after the \f(CW\*(C`,\*(C'\fR separating key-value pairs and array
members.
.PP
If \f(CW$enable\fR is false, then the \f(CW\*(C`encode\*(C'\fR method will not add any extra
space at those places.
.PP
This setting has no effect when decoding \s-1JSON\s0 texts.
.PP
Example, space_before and indent disabled, space_after enabled:
.PP
.Vb 1
\&   {"key": "value"}
.Ve
.SS "relaxed"
.IX Subsection "relaxed"
.Vb 1
\&    $json = $json\->relaxed([$enable])
\&    
\&    $enabled = $json\->get_relaxed
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then \f(CW\*(C`decode\*(C'\fR will accept some
extensions to normal \s-1JSON\s0 syntax (see below). \f(CW\*(C`encode\*(C'\fR will not be
affected in anyway. \fIBe aware that this option makes you accept invalid
\&\s-1JSON\s0 texts as if they were valid!\fR. I suggest only to use this option to
parse application-specific files written by humans (configuration files,
resource files etc.)
.PP
If \f(CW$enable\fR is false (the default), then \f(CW\*(C`decode\*(C'\fR will only accept
valid \s-1JSON\s0 texts.
.PP
Currently accepted extensions are:
.IP "\(bu" 4
list items can have an end-comma
.Sp
\&\s-1JSON \s0\fIseparates\fR array elements and key-value pairs with commas. This
can be annoying if you write \s-1JSON\s0 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:
.Sp
.Vb 8
\&   [
\&      1,
\&      2, <\- this comma not normally allowed
\&   ]
\&   {
\&      "k1": "v1",
\&      "k2": "v2", <\- this comma not normally allowed
\&   }
.Ve
.IP "\(bu" 4
shell-style '#'\-comments
.Sp
Whenever \s-1JSON\s0 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.
.Sp
.Vb 4
\&  [
\&     1, # this comment not allowed in JSON
\&        # neither this one...
\&  ]
.Ve
.SS "canonical"
.IX Subsection "canonical"
.Vb 1
\&    $json = $json\->canonical([$enable])
\&    
\&    $enabled = $json\->get_canonical
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then the \f(CW\*(C`encode\*(C'\fR method will output \s-1JSON\s0 objects
by sorting their keys. This is adding a comparatively high overhead.
.PP
If \f(CW$enable\fR is false, then the \f(CW\*(C`encode\*(C'\fR method will output key-value
pairs in the order Perl stores them (which will likely change between runs
of the same script).
.PP
This option is useful if you want the same data structure to be encoded as
the same \s-1JSON\s0 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.
.PP
This setting has no effect when decoding \s-1JSON\s0 texts.
.PP
If you want your own sorting routine, you can give a code reference
or a subroutine name to \f(CW\*(C`sort_by\*(C'\fR. See to \f(CW\*(C`JSON::PP OWN METHODS\*(C'\fR.
.SS "allow_nonref"
.IX Subsection "allow_nonref"
.Vb 1
\&    $json = $json\->allow_nonref([$enable])
\&    
\&    $enabled = $json\->get_allow_nonref
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then the \f(CW\*(C`encode\*(C'\fR method can convert a
non-reference into its corresponding string, number or null \s-1JSON\s0 value,
which is an extension to \s-1RFC4627.\s0 Likewise, \f(CW\*(C`decode\*(C'\fR will accept those \s-1JSON\s0
values instead of croaking.
.PP
If \f(CW$enable\fR is false, then the \f(CW\*(C`encode\*(C'\fR method will croak if it isn't
passed an arrayref or hashref, as \s-1JSON\s0 texts must either be an object
or array. Likewise, \f(CW\*(C`decode\*(C'\fR will croak if given something that is not a
\&\s-1JSON\s0 object or array.
.PP
.Vb 2
\&   JSON::PP\->new\->allow_nonref\->encode ("Hello, World!")
\&   => "Hello, World!"
.Ve
.SS "allow_unknown"
.IX Subsection "allow_unknown"
.Vb 1
\&    $json = $json\->allow_unknown ([$enable])
\&    
\&    $enabled = $json\->get_allow_unknown
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then \*(L"encode\*(R" will *not* throw an
exception when it encounters values it cannot represent in \s-1JSON \s0(for
example, filehandles) but instead will encode a \s-1JSON \s0\*(L"null\*(R" value.
Note that blessed objects are not included here and are handled
separately by c<allow_nonref>.
.PP
If \f(CW$enable\fR is false (the default), then \*(L"encode\*(R" will throw an
exception when it encounters anything it cannot encode as \s-1JSON.\s0
.PP
This option does not affect \*(L"decode\*(R" in any way, and it is
recommended to leave it off unless you know your communications
partner.
.SS "allow_blessed"
.IX Subsection "allow_blessed"
.Vb 1
\&    $json = $json\->allow_blessed([$enable])
\&    
\&    $enabled = $json\->get_allow_blessed
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then the \f(CW\*(C`encode\*(C'\fR method will not
barf when it encounters a blessed reference. Instead, the value of the
\&\fBconvert_blessed\fR option will decide whether \f(CW\*(C`null\*(C'\fR (\f(CW\*(C`convert_blessed\*(C'\fR
disabled or no \f(CW\*(C`TO_JSON\*(C'\fR method found) or a representation of the
object (\f(CW\*(C`convert_blessed\*(C'\fR enabled and \f(CW\*(C`TO_JSON\*(C'\fR method found) is being
encoded. Has no effect on \f(CW\*(C`decode\*(C'\fR.
.PP
If \f(CW$enable\fR is false (the default), then \f(CW\*(C`encode\*(C'\fR will throw an
exception when it encounters a blessed object.
.SS "convert_blessed"
.IX Subsection "convert_blessed"
.Vb 1
\&    $json = $json\->convert_blessed([$enable])
\&    
\&    $enabled = $json\->get_convert_blessed
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then \f(CW\*(C`encode\*(C'\fR, upon encountering a
blessed object, will check for the availability of the \f(CW\*(C`TO_JSON\*(C'\fR 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
\&\f(CW\*(C`TO_JSON\*(C'\fR method is found, the value of \f(CW\*(C`allow_blessed\*(C'\fR will decide what
to do.
.PP
The \f(CW\*(C`TO_JSON\*(C'\fR method may safely call die if it wants. If \f(CW\*(C`TO_JSON\*(C'\fR
returns other blessed objects, those will be handled in the same
way. \f(CW\*(C`TO_JSON\*(C'\fR must take care of not causing an endless recursion cycle
(== crash) in this case. The name of \f(CW\*(C`TO_JSON\*(C'\fR 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 \f(CW\*(C`to_json\*(C'\fR
function or method.
.PP
This setting does not yet influence \f(CW\*(C`decode\*(C'\fR in any way.
.PP
If \f(CW$enable\fR is false, then the \f(CW\*(C`allow_blessed\*(C'\fR setting will decide what
to do when a blessed object is found.
.SS "filter_json_object"
.IX Subsection "filter_json_object"
.Vb 1
\&    $json = $json\->filter_json_object([$coderef])
.Ve
.PP
When \f(CW$coderef\fR is specified, it will be called from \f(CW\*(C`decode\*(C'\fR each
time it decodes a \s-1JSON\s0 object. The only argument passed to the coderef
is a reference to the newly-created hash. If the code references returns
a single scalar (which need not be a reference), this value
(i.e. a copy of that scalar to avoid aliasing) is inserted into the
deserialised data structure. If it returns an empty list
(\s-1NOTE: \s0\fInot\fR \f(CW\*(C`undef\*(C'\fR, which is a valid scalar), the original deserialised
hash will be inserted. This setting can slow down decoding considerably.
.PP
When \f(CW$coderef\fR is omitted or undefined, any existing callback will
be removed and \f(CW\*(C`decode\*(C'\fR will not change the deserialised hash in any
way.
.PP
Example, convert all \s-1JSON\s0 objects into the integer 5:
.PP
.Vb 6
\&   my $js = JSON::PP\->new\->filter_json_object (sub { 5 });
\&   # returns [5]
\&   $js\->decode (\*(Aq[{}]\*(Aq); # 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 (\*(Aq{"a":1, "b":2}\*(Aq);
.Ve
.SS "filter_json_single_key_object"
.IX Subsection "filter_json_single_key_object"
.Vb 1
\&    $json = $json\->filter_json_single_key_object($key [=> $coderef])
.Ve
.PP
Works remotely similar to \f(CW\*(C`filter_json_object\*(C'\fR, but is only called for
\&\s-1JSON\s0 objects having a single key named \f(CW$key\fR.
.PP
This \f(CW$coderef\fR is called before the one specified via
\&\f(CW\*(C`filter_json_object\*(C'\fR, if any. It gets passed the single value in the \s-1JSON\s0
object. If it returns a single value, it will be inserted into the data
structure. If it returns nothing (not even \f(CW\*(C`undef\*(C'\fR but the empty list),
the callback from \f(CW\*(C`filter_json_object\*(C'\fR will be called next, as if no
single-key callback were specified.
.PP
If \f(CW$coderef\fR is omitted or undefined, the corresponding callback will be
disabled. There can only ever be one callback for a given key.
.PP
As this callback gets called less often then the \f(CW\*(C`filter_json_object\*(C'\fR
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 \s-1JSON\s0 objects are as close to the type-tagged value concept
as \s-1JSON\s0 gets (it's basically an \s-1ID/VALUE\s0 tuple). Of course, \s-1JSON\s0 does not
support this in any way, so you need to make sure your data never looks
like a serialised Perl hash.
.PP
Typical names for the single object key are \f(CW\*(C`_\|_class_whatever_\|_\*(C'\fR, or
\&\f(CW\*(C`$_\|_dollars_are_rarely_used_\|_$\*(C'\fR or \f(CW\*(C`}ugly_brace_placement\*(C'\fR, or even
things like \f(CW\*(C`_\|_class_md5sum(classname)_\|_\*(C'\fR, to reduce the risk of clashing
with real hashes.
.PP
Example, decode \s-1JSON\s0 objects of the form \f(CW\*(C`{ "_\|_widget_\|_" => <id> }\*(C'\fR
into the corresponding \f(CW$WIDGET{<id>}\fR object:
.PP
.Vb 7
\&   # return whatever is in $WIDGET{5}:
\&   JSON::PP
\&      \->new
\&      \->filter_json_single_key_object (_\|_widget_\|_ => sub {
\&            $WIDGET{ $_[0] }
\&         })
\&      \->decode (\*(Aq{"_\|_widget_\|_": 5\*(Aq)
\&
\&   # this can be used with a TO_JSON method in some "widget" class
\&   # for serialisation to json:
\&   sub WidgetBase::TO_JSON {
\&      my ($self) = @_;
\&
\&      unless ($self\->{id}) {
\&         $self\->{id} = ..get..some..id..;
\&         $WIDGET{$self\->{id}} = $self;
\&      }
\&
\&      { _\|_widget_\|_ => $self\->{id} }
\&   }
.Ve
.SS "shrink"
.IX Subsection "shrink"
.Vb 1
\&    $json = $json\->shrink([$enable])
\&    
\&    $enabled = $json\->get_shrink
.Ve
.PP
In \s-1JSON::XS,\s0 this flag resizes strings generated by either
\&\f(CW\*(C`encode\*(C'\fR or \f(CW\*(C`decode\*(C'\fR to their minimum size possible.
It will also try to downgrade any strings to octet-form if possible.
.PP
In \s-1JSON::PP,\s0 it is noop about resizing strings but tries
\&\f(CW\*(C`utf8::downgrade\*(C'\fR to the returned string by \f(CW\*(C`encode\*(C'\fR.
See to utf8.
.PP
See to \*(L"OBJECT-ORIENTED \s-1INTERFACE\*(R"\s0 in \s-1JSON::XS\s0
.SS "max_depth"
.IX Subsection "max_depth"
.Vb 1
\&    $json = $json\->max_depth([$maximum_nesting_depth])
\&    
\&    $max_depth = $json\->get_max_depth
.Ve
.PP
Sets the maximum nesting level (default \f(CW512\fR) accepted while encoding
or decoding. If a higher nesting level is detected in \s-1JSON\s0 text or a Perl
data structure, then the encoder and decoder will stop and croak at that
point.
.PP
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 \f(CW\*(C`{\*(C'\fR or \f(CW\*(C`[\*(C'\fR
characters without their matching closing parenthesis crossed to reach a
given character in a string.
.PP
If no argument is given, the highest possible setting will be used, which
is rarely useful.
.PP
See \*(L"\s-1SSECURITY CONSIDERATIONS\*(R"\s0 in \s-1JSON::XS\s0 for more info on why this is useful.
.PP
When a large value (100 or more) was set and it de/encodes a deep nested object/text,
it may raise a warning 'Deep recursion on subroutine' at the perl runtime phase.
.SS "max_size"
.IX Subsection "max_size"
.Vb 1
\&    $json = $json\->max_size([$maximum_string_size])
\&    
\&    $max_size = $json\->get_max_size
.Ve
.PP
Set the maximum length a \s-1JSON\s0 text may have (in bytes) where decoding is
being attempted. The default is \f(CW0\fR, meaning no limit. When \f(CW\*(C`decode\*(C'\fR
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 \f(CW\*(C`encode\*(C'\fR (yet).
.PP
If no argument is given, the limit check will be deactivated (same as when
\&\f(CW0\fR is specified).
.PP
See \*(L"\s-1SECURITY CONSIDERATIONS\*(R"\s0 in \s-1JSON::XS\s0 for more info on why this is useful.
.SS "encode"
.IX Subsection "encode"
.Vb 1
\&    $json_text = $json\->encode($perl_scalar)
.Ve
.PP
Converts the given Perl data structure (a simple scalar or a reference
to a hash or array) to its \s-1JSON\s0 representation. Simple scalars will be
converted into \s-1JSON\s0 string or number sequences, while references to arrays
become \s-1JSON\s0 arrays and references to hashes become \s-1JSON\s0 objects. Undefined
Perl values (e.g. \f(CW\*(C`undef\*(C'\fR) become \s-1JSON \s0\f(CW\*(C`null\*(C'\fR values.
References to the integers \f(CW0\fR and \f(CW1\fR are converted into \f(CW\*(C`true\*(C'\fR and \f(CW\*(C`false\*(C'\fR.
.SS "decode"
.IX Subsection "decode"
.Vb 1
\&    $perl_scalar = $json\->decode($json_text)
.Ve
.PP
The opposite of \f(CW\*(C`encode\*(C'\fR: expects a \s-1JSON\s0 text and tries to parse it,
returning the resulting simple scalar or reference. Croaks on error.
.PP
\&\s-1JSON\s0 numbers and strings become simple Perl scalars. \s-1JSON\s0 arrays become
Perl arrayrefs and \s-1JSON\s0 objects become Perl hashrefs. \f(CW\*(C`true\*(C'\fR becomes
\&\f(CW1\fR (\f(CW\*(C`JSON::true\*(C'\fR), \f(CW\*(C`false\*(C'\fR becomes \f(CW0\fR (\f(CW\*(C`JSON::false\*(C'\fR) and
\&\f(CW\*(C`null\*(C'\fR becomes \f(CW\*(C`undef\*(C'\fR.
.SS "decode_prefix"
.IX Subsection "decode_prefix"
.Vb 1
\&    ($perl_scalar, $characters) = $json\->decode_prefix($json_text)
.Ve
.PP
This works like the \f(CW\*(C`decode\*(C'\fR method, but instead of raising an exception
when there is trailing garbage after the first \s-1JSON\s0 object, it will
silently stop parsing there and return the number of characters consumed
so far.
.PP
.Vb 2
\&   JSON\->new\->decode_prefix ("[1] the tail")
\&   => ([], 3)
.Ve
.SH "INCREMENTAL PARSING"
.IX Header "INCREMENTAL PARSING"
Most of this section are copied and modified from \*(L"\s-1INCREMENTAL PARSING\*(R"\s0 in \s-1JSON::XS\s0.
.PP
In some cases, there is the need for incremental parsing of \s-1JSON\s0 texts.
This module does allow you to parse a \s-1JSON\s0 stream incrementally.
It does so by accumulating text until it has a full \s-1JSON\s0 object, which
it then can decode. This process is similar to using \f(CW\*(C`decode_prefix\*(C'\fR
to see if a full \s-1JSON\s0 object is available, but is much more efficient
(and can be implemented with a minimum of method calls).
.PP
This module will only attempt to parse the \s-1JSON\s0 text once it is sure it
has enough text to get a decisive result, using a very simple but
truly incremental parser. This means that it sometimes won't stop as
early as the full parser, for example, it doesn't detect parenthesis
mismatches. The only thing it guarantees is that it starts decoding as
soon as a syntactically valid \s-1JSON\s0 text has been seen. This means you need
to set resource limits (e.g. \f(CW\*(C`max_size\*(C'\fR) to ensure the parser will stop
parsing in the presence if syntax errors.
.PP
The following methods implement this incremental parser.
.SS "incr_parse"
.IX Subsection "incr_parse"
.Vb 1
\&    $json\->incr_parse( [$string] ) # void context
\&    
\&    $obj_or_undef = $json\->incr_parse( [$string] ) # scalar context
\&    
\&    @obj_or_empty = $json\->incr_parse( [$string] ) # list context
.Ve
.PP
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).
.PP
If \f(CW$string\fR is given, then this string is appended to the already
existing \s-1JSON\s0 fragment stored in the \f(CW$json\fR object.
.PP
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.
.PP
If the method is called in scalar context, then it will try to extract
exactly \fIone\fR \s-1JSON\s0 object. If that is successful, it will return this
object, otherwise it will return \f(CW\*(C`undef\*(C'\fR. If there is a parse error,
this method will croak just as \f(CW\*(C`decode\*(C'\fR would do (one can then use
\&\f(CW\*(C`incr_skip\*(C'\fR to skip the erroneous part). This is the most common way of
using the method.
.PP
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 \s-1JSON\s0
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 \s-1JSON\s0 texts will be
lost.
.PP
Example: Parse some \s-1JSON\s0 arrays/objects in a given string and return them.
.PP
.Vb 1
\&    my @objs = JSON\->new\->incr_parse ("[5][7][1,2]");
.Ve
.SS "incr_text"
.IX Subsection "incr_text"
.Vb 1
\&    $lvalue_string = $json\->incr_text
.Ve
.PP
This method returns the currently stored \s-1JSON\s0 fragment as an lvalue, that
is, you can manipulate it. This \fIonly\fR works when a preceding call to
\&\f(CW\*(C`incr_parse\*(C'\fR in \fIscalar context\fR 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 \fIwill\fR fail under
real world conditions). As a special exception, you can also call this
method before having parsed anything.
.PP
This function is useful in two cases: a) finding the trailing text after a
\&\s-1JSON\s0 object or b) parsing multiple \s-1JSON\s0 objects separated by non-JSON text
(such as commas).
.PP
.Vb 1
\&    $json\->incr_text =~ s/\es*,\es*//;
.Ve
.PP
In Perl 5.005, \f(CW\*(C`lvalue\*(C'\fR attribute is not available.
You must write codes like the below:
.PP
.Vb 3
\&    $string = $json\->incr_text;
\&    $string =~ s/\es*,\es*//;
\&    $json\->incr_text( $string );
.Ve
.SS "incr_skip"
.IX Subsection "incr_skip"
.Vb 1
\&    $json\->incr_skip
.Ve
.PP
This will reset the state of the incremental parser and will remove the
parsed text from the input buffer. This is useful after \f(CW\*(C`incr_parse\*(C'\fR
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.
.SS "incr_reset"
.IX Subsection "incr_reset"
.Vb 1
\&    $json\->incr_reset
.Ve
.PP
This completely resets the incremental parser, that is, after this call,
it will be as if the parser had never parsed anything.
.PP
This is useful if you want to repeatedly parse \s-1JSON\s0 objects and want to
ignore any trailing data, which means you have to reset the parser after
each successful decode.
.PP
See to \*(L"\s-1INCREMENTAL PARSING\*(R"\s0 in \s-1JSON::XS\s0 for examples.
.SH "JSON::PP OWN METHODS"
.IX Header "JSON::PP OWN METHODS"
.SS "allow_singlequote"
.IX Subsection "allow_singlequote"
.Vb 1
\&    $json = $json\->allow_singlequote([$enable])
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then \f(CW\*(C`decode\*(C'\fR will accept
\&\s-1JSON\s0 strings quoted by single quotations that are invalid \s-1JSON\s0
format.
.PP
.Vb 3
\&    $json\->allow_singlequote\->decode({"foo":\*(Aqbar\*(Aq});
\&    $json\->allow_singlequote\->decode({\*(Aqfoo\*(Aq:"bar"});
\&    $json\->allow_singlequote\->decode({\*(Aqfoo\*(Aq:\*(Aqbar\*(Aq});
.Ve
.PP
As same as the \f(CW\*(C`relaxed\*(C'\fR option, this option may be used to parse
application-specific files written by humans.
.SS "allow_barekey"
.IX Subsection "allow_barekey"
.Vb 1
\&    $json = $json\->allow_barekey([$enable])
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then \f(CW\*(C`decode\*(C'\fR will accept
bare keys of \s-1JSON\s0 object that are invalid \s-1JSON\s0 format.
.PP
As same as the \f(CW\*(C`relaxed\*(C'\fR option, this option may be used to parse
application-specific files written by humans.
.PP
.Vb 1
\&    $json\->allow_barekey\->decode(\*(Aq{foo:"bar"}\*(Aq);
.Ve
.SS "allow_bignum"
.IX Subsection "allow_bignum"
.Vb 1
\&    $json = $json\->allow_bignum([$enable])
.Ve
.PP
If \f(CW$enable\fR is true (or missing), then \f(CW\*(C`decode\*(C'\fR will convert
the big integer Perl cannot handle as integer into a Math::BigInt
object and convert a floating number (any) into a Math::BigFloat.
.PP
On the contrary, \f(CW\*(C`encode\*(C'\fR converts \f(CW\*(C`Math::BigInt\*(C'\fR objects and \f(CW\*(C`Math::BigFloat\*(C'\fR
objects into \s-1JSON\s0 numbers with \f(CW\*(C`allow_blessed\*(C'\fR enable.
.PP
.Vb 4
\&   $json\->allow_nonref\->allow_blessed\->allow_bignum;
\&   $bigfloat = $json\->decode(\*(Aq2.000000000000000000000000001\*(Aq);
\&   print $json\->encode($bigfloat);
\&   # => 2.000000000000000000000000001
.Ve
.PP
See to \*(L"\s-1MAPPING\*(R"\s0 in \s-1JSON::XS\s0 about the normal conversion of \s-1JSON\s0 number.
.SS "loose"
.IX Subsection "loose"
.Vb 1
\&    $json = $json\->loose([$enable])
.Ve
.PP
The unescaped [\ex00\-\ex1f\ex22\ex2f\ex5c] strings are invalid in \s-1JSON\s0 strings
and the module doesn't allow to \f(CW\*(C`decode\*(C'\fR to these (except for \ex2f).
If \f(CW$enable\fR is true (or missing), then \f(CW\*(C`decode\*(C'\fR  will accept these
unescaped strings.
.PP
.Vb 2
\&    $json\->loose\->decode(qq|["abc
\&                                   def"]|);
.Ve
.PP
See \*(L"\s-1SSECURITY CONSIDERATIONS\*(R"\s0 in \s-1JSON::XS\s0.
.SS "escape_slash"
.IX Subsection "escape_slash"
.Vb 1
\&    $json = $json\->escape_slash([$enable])
.Ve
.PP
According to \s-1JSON\s0 Grammar, \fIslash\fR (U+002F) is escaped. But default
\&\s-1JSON::PP \s0(as same as \s-1JSON::XS\s0) encodes strings without escaping slash.
.PP
If \f(CW$enable\fR is true (or missing), then \f(CW\*(C`encode\*(C'\fR will escape slashes.
.SS "indent_length"
.IX Subsection "indent_length"
.Vb 1
\&    $json = $json\->indent_length($length)
.Ve
.PP
\&\s-1JSON::XS\s0 indent space length is 3 and cannot be changed.
\&\s-1JSON::PP\s0 set the indent space length with the given \f(CW$length\fR.
The default is 3. The acceptable range is 0 to 15.
.SS "sort_by"
.IX Subsection "sort_by"
.Vb 2
\&    $json = $json\->sort_by($function_name)
\&    $json = $json\->sort_by($subroutine_ref)
.Ve
.PP
If \f(CW$function_name\fR or \f(CW$subroutine_ref\fR are set, its sort routine are used
in encoding \s-1JSON\s0 objects.
.PP
.Vb 2
\&   $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 = $pc\->sort_by(\*(Aqown_sort\*(Aq)\->encode($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 $JSON::PP::b }
.Ve
.PP
As the sorting routine runs in the \s-1JSON::PP\s0 scope, the given
subroutine name and the special variables \f(CW$a\fR, \f(CW$b\fR will begin
\&'\s-1JSON::PP::\s0'.
.PP
If \f(CW$integer\fR is set, then the effect is same as \f(CW\*(C`canonical\*(C'\fR on.
.SH "INTERNAL"
.IX Header "INTERNAL"
For developers.
.IP "PP_encode_box" 4
.IX Item "PP_encode_box"
Returns
.Sp
.Vb 4
\&        {
\&            depth        => $depth,
\&            indent_count => $indent_count,
\&        }
.Ve
.IP "PP_decode_box" 4
.IX Item "PP_decode_box"
Returns
.Sp
.Vb 9
\&        {
\&            text    => $text,
\&            at      => $at,
\&            ch      => $ch,
\&            len     => $len,
\&            depth   => $depth,
\&            encoding      => $encoding,
\&            is_valid_utf8 => $is_valid_utf8,
\&        };
.Ve
.SH "MAPPING"
.IX Header "MAPPING"
This section is copied from \s-1JSON::XS\s0 and modified to \f(CW\*(C`JSON::PP\*(C'\fR.
\&\s-1JSON::XS\s0 and \s-1JSON::PP\s0 mapping mechanisms are almost equivalent.
.PP
See to \*(L"\s-1MAPPING\*(R"\s0 in \s-1JSON::XS\s0.
.SS "\s-1JSON \-\s0> \s-1PERL\s0"
.IX Subsection "JSON -> PERL"
.IP "object" 4
.IX Item "object"
A \s-1JSON\s0 object becomes a reference to a hash in Perl. No ordering of object
keys is preserved (\s-1JSON\s0 does not preserver object key ordering itself).
.IP "array" 4
.IX Item "array"
A \s-1JSON\s0 array becomes a reference to an array in Perl.
.IP "string" 4
.IX Item "string"
A \s-1JSON\s0 string becomes a string scalar in Perl \- Unicode codepoints in \s-1JSON\s0
are represented by the same codepoints in the Perl string, so no manual
decoding is necessary.
.IP "number" 4
.IX Item "number"
A \s-1JSON\s0 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.
.Sp
If the number consists of digits only, \f(CW\*(C`JSON\*(C'\fR 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 \s-1JSON\s0 number will be
re-encoded to a \s-1JSON\s0 string).
.Sp
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 \s-1JSON\s0 number will still be re-encoded as a \s-1JSON\s0 number).
.Sp
Note that precision is not accuracy \- binary floating point values cannot
represent most decimal fractions exactly, and when converting from and to
floating point, \f(CW\*(C`JSON\*(C'\fR only guarantees precision up to but not including
the least significant bit.
.Sp
When \f(CW\*(C`allow_bignum\*(C'\fR is enable, the big integers 
and the numeric can be optionally converted into Math::BigInt and
Math::BigFloat objects.
.IP "true, false" 4
.IX Item "true, false"
These \s-1JSON\s0 atoms become \f(CW\*(C`JSON::PP::true\*(C'\fR and \f(CW\*(C`JSON::PP::false\*(C'\fR,
respectively. They are overloaded to act almost exactly like the numbers
\&\f(CW1\fR and \f(CW0\fR. You can check whether a scalar is a \s-1JSON\s0 boolean by using
the \f(CW\*(C`JSON::is_bool\*(C'\fR function.
.Sp
.Vb 4
\&   print JSON::PP::true . "\en";
\&    => true
\&   print JSON::PP::true + 1;
\&    => 1
\&
\&   ok(JSON::true eq  \*(Aq1\*(Aq);
\&   ok(JSON::true == 1);
.Ve
.Sp
\&\f(CW\*(C`JSON\*(C'\fR will install these missing overloading features to the backend modules.
.IP "null" 4
.IX Item "null"
A \s-1JSON\s0 null atom becomes \f(CW\*(C`undef\*(C'\fR in Perl.
.Sp
\&\f(CW\*(C`JSON::PP::null\*(C'\fR returns \f(CW\*(C`undef\*(C'\fR.
.SS "\s-1PERL \-\s0> \s-1JSON\s0"
.IX Subsection "PERL -> JSON"
The mapping from Perl to \s-1JSON\s0 is slightly more difficult, as Perl is a
truly typeless language, so we can only guess which \s-1JSON\s0 type is meant by
a Perl value.
.IP "hash references" 4
.IX Item "hash references"
Perl hash references become \s-1JSON\s0 objects. As there is no inherent ordering
in hash keys (or \s-1JSON\s0 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. \f(CW\*(C`JSON\*(C'\fR
optionally sort the hash keys (determined by the \fIcanonical\fR flag), so
the same data structure will serialise to the same \s-1JSON\s0 text (given same
settings and version of \s-1JSON::XS\s0), but this incurs a runtime overhead
and is only rarely useful, e.g. when you want to compare some \s-1JSON\s0 text
against another for equality.
.IP "array references" 4
.IX Item "array references"
Perl array references become \s-1JSON\s0 arrays.
.IP "other references" 4
.IX Item "other references"
Other unblessed references are generally not allowed and will cause an
exception to be thrown, except for references to the integers \f(CW0\fR and
\&\f(CW1\fR, which get turned into \f(CW\*(C`false\*(C'\fR and \f(CW\*(C`true\*(C'\fR atoms in \s-1JSON.\s0 You can
also use \f(CW\*(C`JSON::false\*(C'\fR and \f(CW\*(C`JSON::true\*(C'\fR to improve readability.
.Sp
.Vb 1
\&   to_json [\e0,JSON::PP::true]      # yields [false,true]
.Ve
.IP "JSON::PP::true, JSON::PP::false, JSON::PP::null" 4
.IX Item "JSON::PP::true, JSON::PP::false, JSON::PP::null"
These special values become \s-1JSON\s0 true and \s-1JSON\s0 false values,
respectively. You can also use \f(CW\*(C`\e1\*(C'\fR and \f(CW\*(C`\e0\*(C'\fR directly if you want.
.Sp
JSON::PP::null returns \f(CW\*(C`undef\*(C'\fR.
.IP "blessed objects" 4
.IX Item "blessed objects"
Blessed objects are not directly representable in \s-1JSON.\s0 See the
\&\f(CW\*(C`allow_blessed\*(C'\fR and \f(CW\*(C`convert_blessed\*(C'\fR 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.
.Sp
See to convert_blessed.
.IP "simple scalars" 4
.IX Item "simple scalars"
Simple Perl scalars (any scalar that is not a reference) are the most
difficult objects to encode: \s-1JSON::XS\s0 and \s-1JSON::PP\s0 will encode undefined scalars as
\&\s-1JSON \s0\f(CW\*(C`null\*(C'\fR values, scalars that have last been used in a string context
before encoding as \s-1JSON\s0 strings, and anything else as number value:
.Sp
.Vb 4
\&   # 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]
.Ve
.Sp
You can force the type to be a string by stringifying it:
.Sp
.Vb 4
\&   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
.Ve
.Sp
You can force the type to be a number by numifying it:
.Sp
.Vb 3
\&   my $x = "3"; # some variable containing a string
\&   $x += 0;     # numify it, ensuring it will be dumped as a number
\&   $x *= 1;     # same thing, the choice is yours.
.Ve
.Sp
You can not currently force the type in other, less obscure, ways.
.Sp
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 \s-1JSON,\s0 and it is an
error to pass those in.
.IP "Big Number" 4
.IX Item "Big Number"
When \f(CW\*(C`allow_bignum\*(C'\fR is enable, 
\&\f(CW\*(C`encode\*(C'\fR converts \f(CW\*(C`Math::BigInt\*(C'\fR objects and \f(CW\*(C`Math::BigFloat\*(C'\fR
objects into \s-1JSON\s0 numbers.
.SH "UNICODE HANDLING ON PERLS"
.IX Header "UNICODE HANDLING ON PERLS"
If you do not know about Unicode on Perl well,
please check \*(L"A \s-1FEW NOTES ON UNICODE AND PERL\*(R"\s0 in \s-1JSON::XS\s0.
.SS "Perl 5.8 and later"
.IX Subsection "Perl 5.8 and later"
Perl can handle Unicode and the \s-1JSON::PP\s0 de/encode methods also work properly.
.PP
.Vb 2
\&    $json\->allow_nonref\->encode(chr hex 3042);
\&    $json\->allow_nonref\->encode(chr hex 12345);
.Ve
.PP
Returns \f(CW"\eu3042"\fR and \f(CW"\eud808\eudf45"\fR respectively.
.PP
.Vb 2
\&    $json\->allow_nonref\->decode(\*(Aq"\eu3042"\*(Aq);
\&    $json\->allow_nonref\->decode(\*(Aq"\eud808\eudf45"\*(Aq);
.Ve
.PP
Returns \s-1UTF\-8\s0 encoded strings with \s-1UTF8\s0 flag, regarded as \f(CW\*(C`U+3042\*(C'\fR and \f(CW\*(C`U+12345\*(C'\fR.
.PP
Note that the versions from Perl 5.8.0 to 5.8.2, Perl built-in \f(CW\*(C`join\*(C'\fR was broken,
so \s-1JSON::PP\s0 wraps the \f(CW\*(C`join\*(C'\fR with a subroutine. Thus \s-1JSON::PP\s0 works slow in the versions.
.SS "Perl 5.6"
.IX Subsection "Perl 5.6"
Perl can handle Unicode and the \s-1JSON::PP\s0 de/encode methods also work.
.SS "Perl 5.005"
.IX Subsection "Perl 5.005"
Perl 5.005 is a byte semantics world \*(-- all strings are sequences of bytes.
That means the unicode handling is not available.
.PP
In encoding,
.PP
.Vb 2
\&    $json\->allow_nonref\->encode(chr hex 3042);  # hex 3042 is 12354.
\&    $json\->allow_nonref\->encode(chr hex 12345); # hex 12345 is 74565.
.Ve
.PP
Returns \f(CW\*(C`B\*(C'\fR and \f(CW\*(C`E\*(C'\fR, as \f(CW\*(C`chr\*(C'\fR takes a value more than 255, it treats
as \f(CW\*(C`$value % 256\*(C'\fR, so the above codes are equivalent to :
.PP
.Vb 2
\&    $json\->allow_nonref\->encode(chr 66);
\&    $json\->allow_nonref\->encode(chr 69);
.Ve
.PP
In decoding,
.PP
.Vb 1
\&    $json\->decode(\*(Aq"\eu00e3\eu0081\eu0082"\*(Aq);
.Ve
.PP
The returned is a byte sequence \f(CW\*(C`0xE3 0x81 0x82\*(C'\fR for \s-1UTF\-8\s0 encoded
japanese character (\f(CW\*(C`HIRAGANA LETTER A\*(C'\fR).
And if it is represented in Unicode code point, \f(CW\*(C`U+3042\*(C'\fR.
.PP
Next,
.PP
.Vb 1
\&    $json\->decode(\*(Aq"\eu3042"\*(Aq);
.Ve
.PP
We ordinary expect the returned value is a Unicode character \f(CW\*(C`U+3042\*(C'\fR.
But here is 5.005 world. This is \f(CW\*(C`0xE3 0x81 0x82\*(C'\fR.
.PP
.Vb 1
\&    $json\->decode(\*(Aq"\eud808\eudf45"\*(Aq);
.Ve
.PP
This is not a character \f(CW\*(C`U+12345\*(C'\fR but bytes \- \f(CW\*(C`0xf0 0x92 0x8d 0x85\*(C'\fR.
.SH "TODO"
.IX Header "TODO"
.IP "speed" 4
.IX Item "speed"
.PD 0
.IP "memory saving" 4
.IX Item "memory saving"
.PD
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Most of the document are copied and modified from \s-1JSON::XS\s0 doc.
.PP
\&\s-1JSON::XS\s0
.PP
\&\s-1RFC4627 \s0(<http://www.ietf.org/rfc/rfc4627.txt>)
.SH "AUTHOR"
.IX Header "AUTHOR"
Makamaka Hannyaharamitu, <makamaka[at]cpan.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright 2007\-2012 by Makamaka Hannyaharamitu
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
