JSON::PP(3p) Perl Programmers Reference Guide JSON::PP(3p)

JSON::PP(3p) Perl Programmers Reference Guide JSON::PP(3p) #

JSON::PP(3p) Perl Programmers Reference Guide JSON::PP(3p)

NNAAMMEE #

 JSON::PP - JSON::XS compatible pure-Perl module.

SSYYNNOOPPSSIISS #

  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

  $json = JSON::PP->new->ascii->pretty->allow_nonref;

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

  # 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;

DDEESSCCRRIIPPTTIIOONN #

 JSON::PP is a pure perl JSON decoder/encoder, and (almost) compatible to
 much faster JSON::XS written by Marc Lehmann in C. JSON::PP works as a
 fallback module when you use JSON module without having installed

JSON::XS. #

 Because of this fallback feature of JSON.pm, JSON::PP tries not to be
 more JavaScript-friendly than JSON::XS (i.e. not to escape extra
 characters such as U+2028 and U+2029, etc), in order for you not to lose
 such JavaScript-friendliness silently when you use JSON.pm and install
 JSON::XS for speed or by accident.  If you need JavaScript-friendly
 RFC7159-compliant pure perl module, try JSON::Tiny, which is derived from
 Mojolicious web framework and is also smaller and faster than JSON::PP.

 JSON::PP has been in the Perl core since Perl 5.14, mainly for CPAN
 toolchain modules to parse META.json.

FFUUNNCCTTIIOONNAALL IINNTTEERRFFAACCEE #

 This section is taken from JSON::XS almost verbatim. "encode_json" and
 "decode_json" are exported by default.

eennccooddee__jjssoonn $json_text = encode_json $perl_scalar

 Converts the given Perl data structure to a UTF-8 encoded, binary string
 (that is, the string contains octets only). Croaks on error.

 This function call is functionally identical to:

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

 Except being faster.

ddeeccooddee__jjssoonn $perl_scalar = decode_json $json_text

 The opposite of "encode_json": expects an UTF-8 (binary) string and tries
 to parse that as an UTF-8 encoded JSON text, returning the resulting
 reference. Croaks on error.

 This function call is functionally identical to:

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

 Except being faster.

JJSSOONN::::PPPP::::iiss__bbooooll $is_boolean = JSON::PP::is_bool($scalar)

 Returns true if the passed scalar represents either JSON::PP::true or
 JSON::PP::false, two constants that act like 1 and 0 respectively and are
 also used to represent JSON "true" and "false" in Perl strings.

 See MAPPING, below, for more information on how JSON values are mapped to
 Perl.

OOBBJJEECCTT--OORRIIEENNTTEEDD IINNTTEERRFFAACCEE #

 This section is also taken from JSON::XS.

 The object oriented interface lets you configure your own encoding or
 decoding style, within the limits of supported formats.

nneeww $json = JSON::PP->new

 Creates a new JSON::PP object that can be used to de/encode JSON strings.
 All boolean flags described below are by default _d_i_s_a_b_l_e_d (with the
 exception of "allow_nonref", which defaults to _e_n_a_b_l_e_d since version
 4.0).

 The mutators for flags all return the JSON::PP object again and thus
 calls can be chained:

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

aasscciiii $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 (which is ASCII). Any
 Unicode characters outside that range will be escaped using either a
 single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
 as per RFC4627. The resulting encoded JSON text can be treated as a
 native Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded
 string, or any other superset of ASCII.

 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.

 See also the section _E_N_C_O_D_I_N_G_/_C_O_D_E_S_E_T _F_L_A_G _N_O_T_E_S later in this document.

 The main use for this flag is to produce JSON texts that can be
 transmitted over a 7-bit channel, as the encoded JSON texts will not
 contain any 8 bit characters.

   JSON::PP->new->ascii(1)->encode([chr 0x10401])
   => ["\ud801\udc01"]

llaattiinn11 $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. The resulting string can be treated as a
 latin1-encoded JSON text or a native Unicode string. The "decode" method
 will not be affected in any way by this flag, as "decode" by default
 expects Unicode, which is a strict superset of latin1.

 If $enable is false, then the "encode" method will not escape Unicode
 characters unless required by the JSON syntax or other flags.

 See also the section _E_N_C_O_D_I_N_G_/_C_O_D_E_S_E_T _F_L_A_G _N_O_T_E_S later in this document.

 The main use for this flag is efficiently encoding binary data as JSON
 text, as most octets will not be escaped, resulting in a smaller encoded
 size. The disadvantage is that the resulting JSON text is encoded in
 latin1 (and must correctly be treated as such when storing and
 transferring), a rare encoding for JSON. It is therefore most useful when
 you want to store data structures known to contain binary data
 efficiently in files or databases, not when talking to other JSON
 encoders/decoders.

   JSON::PP->new->latin1->encode (["\x{89}\x{abc}"]
   => ["\x{89}\\u0abc"]    # (perl syntax, U+abc escaped, U+89 not)

uuttff88 $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.

 See also the section _E_N_C_O_D_I_N_G_/_C_O_D_E_S_E_T _F_L_A_G _N_O_T_E_S later in this document.

 Example, output UTF-16BE-encoded JSON:

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

 Example, decode UTF-32LE-encoded JSON:

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

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

 This enables (or disables) all of the "indent", "space_before" and
 "space_after" (and in the future possibly more) flags in one call to
 generate the most readable (or most compact) form possible.

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

     $enabled = $json->get_indent

 If $enable is true (or missing), then the "encode" method will use a
 multiline format as output, putting every array member or object/hash
 key-value pair into its own line, indenting them properly.

 If $enable is false, no newlines or indenting will be produced, and the
 resulting JSON text is guaranteed not to contain any "newlines".

 This setting has no effect when decoding JSON texts.

 The default indent space length is three.  You can use "indent_length" to
 change the length.

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

     $enabled = $json->get_space_before

 If $enable is true (or missing), then the "encode" method will add an
 extra optional space before the ":" separating keys from values in JSON
 objects.

 If $enable is false, then the "encode" method will not add any extra
 space at those places.

 This setting has no effect when decoding JSON texts. You will also most
 likely combine this setting with "space_after".

 Example, space_before enabled, space_after and indent disabled:

    {"key" :"value"}

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

     $enabled = $json->get_space_after

 If $enable is true (or missing), then the "encode" method will add an
 extra optional space after the ":" separating keys from values in JSON
 objects and extra whitespace after the "," separating key-value pairs and
 array members.

 If $enable is false, then the "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"}

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

     $enabled = $json->get_relaxed

 If $enable is true (or missing), then "decode" will accept some
 extensions to normal JSON syntax (see below). "encode" will not be
 affected in anyway. _B_e _a_w_a_r_e _t_h_a_t _t_h_i_s _o_p_t_i_o_n _m_a_k_e_s _y_o_u _a_c_c_e_p_t _i_n_v_a_l_i_d
 _J_S_O_N _t_e_x_t_s _a_s _i_f _t_h_e_y _w_e_r_e _v_a_l_i_d_!. I suggest only to use this option to
 parse application-specific files written by humans (configuration files,
 resource files etc.)

 If $enable is false (the default), then "decode" will only accept valid
 JSON texts.

 Currently accepted extensions are:

 •   list items can have an end-comma

     JSON _s_e_p_a_r_a_t_e_s 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
        }

 •   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...
       ]

 •   C-style multiple-line '/* */'-comments (JSON::PP only)

     Whenever JSON allows whitespace, C-style multiple-line comments are
     additionally allowed. Everything between "/*" and "*/" is a comment,
     after which more white-space and comments are allowed.

       [
          1, /* this comment not allowed in JSON */
             /* neither this one... */
       ]

 •   C++-style one-line '//'-comments (JSON::PP only)

     Whenever JSON allows whitespace, C++-style one-line 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...
       ]

 •   literal ASCII TAB characters in strings

     Literal ASCII TAB characters are now allowed in strings (and treated
     as "\t").

       [
          "Hello\tWorld",
          "Hello<TAB>World", # literal <TAB> would not normally be allowed
       ]

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

     $enabled = $json->get_canonical

 If $enable is true (or missing), then the "encode" method will output
 JSON objects by sorting their keys. This is adding a comparatively high
 overhead.

 If $enable is false, then the "encode" method will output key-value pairs
 in the order Perl stores them (which will likely change between runs of
 the same script, and can change even within the same run from 5.18
 onwards).

 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.

 This setting has currently no effect on tied hashes.

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

     $enabled = $json->get_allow_nonref

 Unlike other boolean options, this opotion is enabled by default
 beginning with version 4.0.

 If $enable is true (or missing), then the "encode" method can convert a
 non-reference into its corresponding string, number or null JSON value,
 which is an extension to RFC4627. Likewise, "decode" will accept those
 JSON values instead of croaking.

 If $enable is false, then the "encode" method will croak if it isn't
 passed an arrayref or hashref, as JSON texts must either be an object or
 array. Likewise, "decode" will croak if given something that is not a
 JSON object or array.

 Example, encode a Perl scalar as JSON value without enabled
 "allow_nonref", resulting in an error:

    JSON::PP->new->allow_nonref(0)->encode ("Hello, World!")
    => hash- or arrayref expected...

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

     $enabled = $json->get_allow_unknown

 If $enable is true (or missing), then "encode" will _n_o_t 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_blessed>.

 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.

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

     $enabled = $json->get_allow_blessed

 See "OBJECT SERIALISATION" for details.

 If $enable is true (or missing), then the "encode" method will not barf
 when it encounters a blessed reference that it cannot convert otherwise.
 Instead, a JSON "null" value is encoded instead of the object.

 If $enable is false (the default), then "encode" will throw an exception
 when it encounters a blessed object that it cannot convert otherwise.

 This setting has no effect on "decode".

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

     $enabled = $json->get_convert_blessed

 See "OBJECT SERIALISATION" for details.

 If $enable is true (or missing), then "encode", upon encountering a
 blessed object, will check for the availability of the "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.

 The "TO_JSON" method may safely call die if it wants. If "TO_JSON"
 returns other blessed objects, those will be handled in the same way.
 "TO_JSON" must take care of not causing an endless recursion cycle (==
 crash) in this case. The name of "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 any "to_json"
 function or method.

 If $enable is false (the default), then "encode" will not consider this
 type of conversion.

 This setting has no effect on "decode".

aallllooww__ttaaggss $json = $json->allow_tags([$enable])

     $enabled = $json->get_allow_tags

 See "OBJECT SERIALISATION" for details.

 If $enable is true (or missing), then "encode", upon encountering a
 blessed object, will check for the availability of the "FREEZE" method on
 the object's class. If found, it will be used to serialise the object
 into a nonstandard tagged JSON value (that JSON decoders cannot decode).

 It also causes "decode" to parse such tagged JSON values and deserialise
 them via a call to the "THAW" method.

 If $enable is false (the default), then "encode" will not consider this
 type of conversion, and tagged JSON values will cause a parse error in
 "decode", as if tags were not part of the grammar.

bboooolleeaann__vvaalluueess $json->boolean_values([$false, $true])

     ($false,  $true) = $json->get_boolean_values

 By default, JSON booleans will be decoded as overloaded $JSON::PP::false
 and $JSON::PP::true objects.

 With this method you can specify your own boolean values for decoding -
 on decode, JSON "false" will be decoded as a copy of $false, and JSON
 "true" will be decoded as $true ("copy" here is the same thing as
 assigning a value to another variable, i.e. "$copy = $false").

 This is useful when you want to pass a decoded data structure directly to
 other serialisers like YAML, Data::MessagePack and so on.

 Note that this works only when you "decode". You can set incompatible
 boolean objects (like boolean), but when you "encode" a data structure
 with such boolean objects, you still need to enable "convert_blessed"
 (and add a "TO_JSON" method if necessary).

 Calling this method without any arguments will reset the booleans to
 their default values.

 "get_boolean_values" will return both $false and $true values, or the
 empty list when they are set to the default.

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

 When $coderef is specified, it will be called from "decode" each time it
 decodes a JSON object. The only argument is a reference to the newly-
 created hash. If the code references returns a single scalar (which need
 not be a reference), this value (or rather a copy of it) is inserted into
 the deserialised data structure. If it returns an empty list (NOTE: _n_o_t
 "undef", which is a valid scalar), the original deserialised hash will be
 inserted. This setting can slow down decoding considerably.

 When $coderef is omitted or undefined, any existing callback will be
 removed and "decode" will not change the deserialised hash in any way.

 Example, convert all JSON objects into the integer 5:

    my $js = JSON::PP->new->filter_json_object(sub { 5 });
    # returns [5]
    $js->decode('[{}]');
    # returns 5
    $js->decode('{"a":1, "b":2}');

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

 Works remotely similar to "filter_json_object", but is only called for
 JSON objects having a single key named $key.

 This $coderef is called before the one specified via
 "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 "undef" but the empty list),
 the callback from "filter_json_object" will be called next, as if no
 single-key callback were specified.

 If $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 "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 "__class_whatever__", or
 "$__dollars_are_rarely_used__$" or "}ugly_brace_placement", or even
 things like "__class_md5sum(classname)__", to reduce the risk of clashing
 with real hashes.

 Example, decode JSON objects of the form "{ "__widget__" => <id> }" into
 the corresponding $WIDGET{<id>} object:

    # return whatever is in $WIDGET{5}:

JSON::PP #

       ->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} }
    }

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

     $enabled = $json->get_shrink

 If $enable is true (or missing), the string returned by "encode" will be
 shrunk (i.e. downgraded if possible).

 The actual definition of what shrink does might change in future
 versions, but it will always try to save space at the expense of time.

 If $enable is false, then JSON::PP does nothing.

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

     $max_depth = $json->get_max_depth

 Sets the maximum nesting level (default 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 "{" or "["
 characters without their matching closing parenthesis crossed to reach a
 given character in a string.

 Setting the maximum depth to one disallows any nesting, so that ensures
 that the object is only a single hash/object or array.

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

 See "SECURITY CONSIDERATIONS" in JSON::XS for more info on why this is
 useful.

mmaaxx__ssiizzee $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 0, meaning no limit. When "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 "encode" (yet).

 If no argument is given, the limit check will be deactivated (same as
 when 0 is specified).

 See "SECURITY CONSIDERATIONS" in JSON::XS for more info on why this is
 useful.

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

 Converts the given Perl value or data structure to its JSON
 representation. Croaks on error.

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

 The opposite of "encode": expects a JSON text and tries to parse it,
 returning the resulting simple scalar or reference. Croaks on error.

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

 This works like the "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.

 This is useful if your JSON texts are not delimited by an outer protocol
 and you need to know where the JSON text ends.

    JSON::PP->new->decode_prefix ("[1] the tail")
    => ([1], 3)

FFLLAAGGSS FFOORR JJSSOONN::::PPPP OONNLLYY #

 The following flags and properties are for JSON::PP only. If you use any
 of these, you can't make your application run faster by replacing
 JSON::PP with JSON::XS. If you need these and also speed boost, you might
 want to try Cpanel::JSON::XS, a fork of JSON::XS by Reini Urban, which
 supports some of these (with a different set of incompatibilities). Most
 of these historical flags are only kept for backward compatibility, and
 should not be used in a new application.

aallllooww__ssiinngglleeqquuoottee $json = $json->allow_singlequote([$enable]) $enabled = $json->get_allow_singlequote

 If $enable is true (or missing), then "decode" will accept invalid JSON
 texts that contain strings that begin and end with single quotation
 marks. "encode" will not be affected in any way.  _B_e _a_w_a_r_e _t_h_a_t _t_h_i_s
 _o_p_t_i_o_n _m_a_k_e_s _y_o_u _a_c_c_e_p_t _i_n_v_a_l_i_d _J_S_O_N _t_e_x_t_s _a_s _i_f _t_h_e_y _w_e_r_e _v_a_l_i_d_!. I
 suggest only to use this option to parse application-specific files
 written by humans (configuration files, resource files etc.)

 If $enable is false (the default), then "decode" will only accept valid
 JSON texts.

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

aallllooww__bbaarreekkeeyy $json = $json->allow_barekey([$enable]) $enabled = $json->get_allow_barekey

 If $enable is true (or missing), then "decode" will accept invalid JSON
 texts that contain JSON objects whose names don't begin and end with
 quotation marks. "encode" will not be affected in any way. _B_e _a_w_a_r_e _t_h_a_t
 _t_h_i_s _o_p_t_i_o_n _m_a_k_e_s _y_o_u _a_c_c_e_p_t _i_n_v_a_l_i_d _J_S_O_N _t_e_x_t_s _a_s _i_f _t_h_e_y _w_e_r_e _v_a_l_i_d_!. I
 suggest only to use this option to parse application-specific files
 written by humans (configuration files, resource files etc.)

 If $enable is false (the default), then "decode" will only accept valid
 JSON texts.

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

aallllooww__bbiiggnnuumm $json = $json->allow_bignum([$enable]) $enabled = $json->get_allow_bignum

 If $enable is true (or missing), then "decode" will convert big integers
 Perl cannot handle as integer into Math::BigInt objects and convert
 floating numbers into Math::BigFloat objects. "encode" will convert
 "Math::BigInt" and "Math::BigFloat" objects into JSON numbers.

    $json->allow_nonref->allow_bignum;
    $bigfloat = $json->decode('2.000000000000000000000000001');
    print $json->encode($bigfloat);
    # => 2.000000000000000000000000001

 See also MAPPING.

lloooossee $json = $json->loose([$enable]) $enabled = $json->get_loose

 If $enable is true (or missing), then "decode" will accept invalid JSON
 texts that contain unescaped [\x00-\x1f\x22\x5c] characters. "encode"
 will not be affected in any way.  _B_e _a_w_a_r_e _t_h_a_t _t_h_i_s _o_p_t_i_o_n _m_a_k_e_s _y_o_u
 _a_c_c_e_p_t _i_n_v_a_l_i_d _J_S_O_N _t_e_x_t_s _a_s _i_f _t_h_e_y _w_e_r_e _v_a_l_i_d_!. I suggest only to use
 this option to parse application-specific files written by humans
 (configuration files, resource files etc.)

 If $enable is false (the default), then "decode" will only accept valid
 JSON texts.

     $json->loose->decode(qq|["abc
                                    def"]|);

eessccaappee__ssllaasshh $json = $json->escape_slash([$enable]) $enabled = $json->get_escape_slash

 If $enable is true (or missing), then "encode" will explicitly escape
 _s_l_a_s_h (solidus; "U+002F") characters to reduce the risk of XSS (cross
 site scripting) that may be caused by "</script>" in a JSON text, with
 the cost of bloating the size of JSON texts.

 This option may be useful when you embed JSON in HTML, but embedding
 arbitrary JSON in HTML (by some HTML template toolkit or by string
 interpolation) is risky in general. You must escape necessary characters
 in correct order, depending on the context.

 "decode" will not be affected in any way.

iinnddeenntt__lleennggtthh $json = $json->indent_length($number_of_spaces) $length = $json->get_indent_length

 This option is only useful when you also enable "indent" or "pretty".

 JSON::XS indents with three spaces when you "encode" (if requested by
 "indent" or "pretty"), and the number cannot be changed.  JSON::PP allows
 you to change/get the number of indent spaces with these
 mutator/accessor. The default number of spaces is three (the same as
 JSON::XS), and the acceptable range is from 0 (no indentation; it'd be
 better to disable indentation by indent(0)) to 15.

ssoorrtt__bbyy $json = $json->sort_by($code_ref) $json = $json->sort_by($subroutine_name)

 If you just want to sort keys (names) in JSON objects when you "encode",
 enable "canonical" option (see above) that allows you to sort object keys
 alphabetically.

 If you do need to sort non-alphabetically for whatever reasons, you can
 give a code reference (or a subroutine name) to "sort_by", then the
 argument will be passed to Perl's "sort" built-in function.

 As the sorting is done in the JSON::PP scope, you usually need to prepend
 "JSON::PP::" to the subroutine name, and the special variables $a and $b
 used in the subrontine used by "sort" function.

 Example:

    my %ORDER = (id => 1, class => 2, name => 3);
    $json->sort_by(sub {
        ($ORDER{$JSON::PP::a} // 999) <=> ($ORDER{$JSON::PP::b} // 999)
        or $JSON::PP::a cmp $JSON::PP::b
    });
    print $json->encode([
        {name => 'CPAN', id => 1, href => 'http://cpan.org'}
    ]);
    # [{"id":1,"name":"CPAN","href":"http://cpan.org"}]

 Note that "sort_by" affects all the plain hashes in the data structure.
 If you need finer control, "tie" necessary hashes with a module that
 implements ordered hash (such as Hash::Ordered and Tie::IxHash).
 "canonical" and "sort_by" don't affect the key order in "tie"d hashes.

    use Hash::Ordered;
    tie my %hash, 'Hash::Ordered',
        (name => 'CPAN', id => 1, href => 'http://cpan.org');
    print $json->encode([\%hash]);
    # [{"name":"CPAN","id":1,"href":"http://cpan.org"}] # order is kept

IINNCCRREEMMEENNTTAALL PPAARRSSIINNGG #

 This section is also taken from JSON::XS.

 In some cases, there is the need for incremental parsing of JSON texts.
 While this module always has to keep both JSON text and resulting Perl
 data structure in memory at one time, it 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
 "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).

 JSON::PP 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 mismatched parentheses.
 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. "max_size") to ensure the parser will stop parsing
 in the presence if syntax errors.

 The following methods implement this incremental parser.

iinnccrr__ppaarrssee $json->incr_parse( [$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 $string is given, then this string is appended to the already existing
 JSON fragment stored in the $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 _o_n_e JSON object. If that is successful, it will return this
 object, otherwise it will return "undef". If there is a parse error, this
 method will croak just as "decode" would do (one can then use "incr_skip"
 to skip the erroneous part). This is the most common way of using the
 method.

 And finally, in list context, it will try to extract as many objects from
 the stream as it can find and return them, or the empty list otherwise.
 For this to work, there must be no separators (other than whitespace)
 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::PP->new->incr_parse ("[5][7][1,2]");

iinnccrr__tteexxtt $lvalue_string = $json->incr_text

 This method returns the currently stored JSON fragment as an lvalue, that
 is, you can manipulate it. This _o_n_l_y works when a preceding call to
 "incr_parse" in _s_c_a_l_a_r _c_o_n_t_e_x_t 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 _w_i_l_l fail under real world
 conditions). As a special exception, you can also call this method before
 having parsed anything.

 That means you can only use this function to look at or manipulate text
 before or after complete JSON objects, not while the parser is in the
 middle of parsing a JSON object.

 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).

iinnccrr__sskkiipp $json->incr_skip

 This will reset the state of the incremental parser and will remove the
 parsed text from the input buffer so far. This is useful after
 "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.

 The difference to "incr_reset" is that only text until the parse error
 occurred is removed.

iinnccrr__rreesseett $json->incr_reset

 This completely resets the incremental parser, that is, after this call,
 it will be as if the parser had never parsed anything.

 This is useful if you want to repeatedly parse JSON objects and want to
 ignore any trailing data, which means you have to reset the parser after
 each successful decode.

MMAAPPPPIINNGG #

 Most of this section is also taken from JSON::XS.

 This section describes how JSON::PP maps Perl values to JSON values and
 vice versa. These mappings are designed to "do the right thing" in most
 circumstances automatically, preserving round-tripping characteristics
 (what you put in comes out as something equivalent).

 For the more enlightened: note that in the following descriptions,
 lowercase _p_e_r_l refers to the Perl interpreter, while uppercase _P_e_r_l
 refers to the abstract Perl language itself.

JJSSOONN -->> PPEERRLL #

 object
     A JSON object becomes a reference to a hash in Perl. No ordering of
     object keys is preserved (JSON does not preserve object key ordering
     itself).

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

 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.

 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, JSON::PP will try to represent
     it as an integer value. If that fails, it will try to represent it as
     a numeric (floating point) value if that is possible without loss of
     precision. Otherwise it will preserve the number as a string value
     (in which case you lose roundtripping ability, as the JSON number
     will be re-encoded to a JSON string).

     Numbers containing a fractional or exponential part will always be
     represented as numeric (floating point) values, possibly at a loss of
     precision (in which case you might lose perfect roundtripping
     ability, but the JSON number will still be re-encoded as a JSON
     number).

     Note that precision is not accuracy - binary floating point values
     cannot represent most decimal fractions exactly, and when converting
     from and to floating point, JSON::PP only guarantees precision up to
     but not including the least significant bit.

     When "allow_bignum" is enabled, big integer values and any numeric
     values will be converted into Math::BigInt and Math::BigFloat objects
     respectively, without becoming string scalars or losing precision.

 true, false
     These JSON atoms become "JSON::PP::true" and "JSON::PP::false",
     respectively. They are overloaded to act almost exactly like the
     numbers 1 and 0. You can check whether a scalar is a JSON boolean by
     using the "JSON::PP::is_bool" function.

 null
     A JSON null atom becomes "undef" in Perl.

 shell-style comments ("# _t_e_x_t")
     As a nonstandard extension to the JSON syntax that is enabled by the
     "relaxed" setting, shell-style comments are allowed. They can start
     anywhere outside strings and go till the end of the line.

 tagged values ("(_t_a_g)_v_a_l_u_e").
     Another nonstandard extension to the JSON syntax, enabled with the
     "allow_tags" setting, are tagged values. In this implementation, the
     _t_a_g must be a perl package/class name encoded as a JSON string, and
     the _v_a_l_u_e must be a JSON array encoding optional constructor
     arguments.

     See "OBJECT SERIALISATION", below, for details.

PPEERRLL -->> JJSSOONN #

 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.

 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. JSON::PP can optionally sort the hash keys
     (determined by the _c_a_n_o_n_i_c_a_l flag and/or _s_o_r_t___b_y property), so the
     same data structure will serialise to the same JSON text (given same
     settings and version of JSON::PP), 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.

 array references
     Perl array references become JSON arrays.

 other references
     Other unblessed references are generally not allowed and will cause
     an exception to be thrown, except for references to the integers 0
     and 1, which get turned into "false" and "true" atoms in JSON. You
     can also use "JSON::PP::false" and "JSON::PP::true" to improve
     readability.

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

 JSON::PP::true, JSON::PP::false
     These special values become JSON true and JSON false values,
     respectively. You can also use "\1" and "\0" directly if you want.

 JSON::PP::null
     This special value becomes JSON null.

 blessed objects
     Blessed objects are not directly representable in JSON, but
     "JSON::PP" allows various ways of handling objects. See "OBJECT
     SERIALISATION", below, for details.

 simple scalars
     Simple Perl scalars (any scalar that is not a reference) are the most
     difficult objects to encode: JSON::PP will encode undefined scalars
     as JSON "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 JSON 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
                     # (but for older perls)

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

        my $x = "3"; # some variable containing a string
        $x += 0;     # numify it, ensuring it will be dumped as a number
        $x *= 1;     # same thing, the choice is yours.

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

     Since version 2.91_01, JSON::PP uses a different number detection
     logic that converts a scalar that is possible to turn into a number
     safely.  The new logic is slightly faster, and tends to help people
     who use older perl or who want to encode complicated data structure.
     However, this may results in a different JSON text from the one
     JSON::XS encodes (and thus may break tests that compare entire JSON
     texts). If you do need the previous behavior for compatibility or for
     finer control, set PERL_JSON_PP_USE_B environmental variable to true
     before you "use" JSON::PP (or JSON.pm).

     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.

     JSON::PP (and JSON::XS) trusts what you pass to "encode" method (or
     "encode_json" function) is a clean, validated data structure with
     values that can be represented as valid JSON values only, because
     it's not from an external data source (as opposed to JSON texts you
     pass to "decode" or "decode_json", which JSON::PP considers tainted
     and doesn't trust). As JSON::PP doesn't know exactly what you and
     consumers of your JSON texts want the unexpected values to be (you
     may want to convert them into null, or to stringify them with or
     without normalisation (string representation of infinities/NaN may
     vary depending on platforms), or to croak without conversion), you're
     advised to do what you and your consumers need before you encode, and
     also not to numify values that may start with values that look like a
     number (including infinities/NaN), without validating.

OOBBJJEECCTT SSEERRIIAALLIISSAATTIIOONN #

 As JSON cannot directly represent Perl objects, you have to choose
 between a pure JSON representation (without the ability to deserialise
 the object automatically again), and a nonstandard extension to the JSON
 syntax, tagged values.

_S_E_R_I_A_L_I_S_A_T_I_O_N #

 What happens when "JSON::PP" encounters a Perl object depends on the
 "allow_blessed", "convert_blessed", "allow_tags" and "allow_bignum"
 settings, which are used in this order:

 1. "allow_tags" is enabled and the object has a "FREEZE" method.
     In this case, "JSON::PP" creates a tagged JSON value, using a
     nonstandard extension to the JSON syntax.

     This works by invoking the "FREEZE" method on the object, with the
     first argument being the object to serialise, and the second argument
     being the constant string "JSON" to distinguish it from other
     serialisers.

     The "FREEZE" method can return any number of values (i.e. zero or
     more). These values and the paclkage/classname of the object will
     then be encoded as a tagged JSON value in the following format:

        ("classname")[FREEZE return values...]

     e.g.:

        ("URI")["http://www.google.com/"]
        ("MyDate")[2013,10,29]
        ("ImageData::JPEG")["Z3...VlCg=="]

     For example, the hypothetical "My::Object" "FREEZE" method might use
     the objects "type" and "id" members to encode the object:

        sub My::Object::FREEZE {
           my ($self, $serialiser) = @_;

           ($self->{type}, $self->{id})
        }

 2. "convert_blessed" is enabled and the object has a "TO_JSON" method.
     In this case, the "TO_JSON" method of the object is invoked in scalar
     context. It must return a single scalar that can be directly encoded
     into JSON. This scalar replaces the object in the JSON text.

     For example, the following "TO_JSON" method will convert all URI
     objects to JSON strings when serialised. The fact that these values
     originally were URI objects is lost.

        sub URI::TO_JSON {
           my ($uri) = @_;
           $uri->as_string
        }

 3. "allow_bignum" is enabled and the object is a "Math::BigInt" or
 "Math::BigFloat".
     The object will be serialised as a JSON number value.

 4. "allow_blessed" is enabled.
     The object will be serialised as a JSON null value.

 5. none of the above
     If none of the settings are enabled or the respective methods are
     missing, "JSON::PP" throws an exception.

_D_E_S_E_R_I_A_L_I_S_A_T_I_O_N #

 For deserialisation there are only two cases to consider: either
 nonstandard tagging was used, in which case "allow_tags" decides, or
 objects cannot be automatically be deserialised, in which case you can
 use postprocessing or the "filter_json_object" or
 "filter_json_single_key_object" callbacks to get some real objects our of
 your JSON.

 This section only considers the tagged value case: a tagged JSON object
 is encountered during decoding and "allow_tags" is disabled, a parse
 error will result (as if tagged values were not part of the grammar).

 If "allow_tags" is enabled, "JSON::PP" will look up the "THAW" method of
 the package/classname used during serialisation (it will not attempt to
 load the package as a Perl module). If there is no such method, the
 decoding will fail with an error.

 Otherwise, the "THAW" method is invoked with the classname as first
 argument, the constant string "JSON" as second argument, and all the
 values from the JSON array (the values originally returned by the
 "FREEZE" method) as remaining arguments.

 The method must then return the object. While technically you can return
 any Perl scalar, you might have to enable the "allow_nonref" setting to
 make that work in all cases, so better return an actual blessed
 reference.

 As an example, let's implement a "THAW" function that regenerates the
 "My::Object" from the "FREEZE" example earlier:

    sub My::Object::THAW {
       my ($class, $serialiser, $type, $id) = @_;

       $class->new (type => $type, id => $id)
    }

EENNCCOODDIINNGG//CCOODDEESSEETT FFLLAAGG NNOOTTEESS #

 This section is taken from JSON::XS.

 The interested reader might have seen a number of flags that signify
 encodings or codesets - "utf8", "latin1" and "ascii". There seems to be
 some confusion on what these do, so here is a short comparison:

 "utf8" controls whether the JSON text created by "encode" (and expected
 by "decode") is UTF-8 encoded or not, while "latin1" and "ascii" only
 control whether "encode" escapes character values outside their
 respective codeset range. Neither of these flags conflict with each
 other, although some combinations make less sense than others.

 Care has been taken to make all flags symmetrical with respect to
 "encode" and "decode", that is, texts encoded with any combination of
 these flag values will be correctly decoded when the same flags are used
 - in general, if you use different flag settings while encoding vs. when
 decoding you likely have a bug somewhere.

 Below comes a verbose discussion of these flags. Note that a "codeset" is
 simply an abstract set of character-codepoint pairs, while an encoding
 takes those codepoint numbers and _e_n_c_o_d_e_s them, in our case into octets.
 Unicode is (among other things) a codeset, UTF-8 is an encoding, and
 ISO-8859-1 (= latin 1) and ASCII are both codesets _a_n_d encodings at the
 same time, which can be confusing.

 "utf8" flag disabled
     When "utf8" is disabled (the default), then "encode"/"decode"
     generate and expect Unicode strings, that is, characters with high
     ordinal Unicode values (> 255) will be encoded as such characters,
     and likewise such characters are decoded as-is, no changes to them
     will be done, except "(re-)interpreting" them as Unicode codepoints
     or Unicode characters, respectively (to Perl, these are the same
     thing in strings unless you do funny/weird/dumb stuff).

     This is useful when you want to do the encoding yourself (e.g. when
     you want to have UTF-16 encoded JSON texts) or when some other layer
     does the encoding for you (for example, when printing to a terminal
     using a filehandle that transparently encodes to UTF-8 you certainly
     do NOT want to UTF-8 encode your data first and have Perl encode it
     another time).

 "utf8" flag enabled
     If the "utf8"-flag is enabled, "encode"/"decode" will encode all
     characters using the corresponding UTF-8 multi-byte sequence, and
     will expect your input strings to be encoded as UTF-8, that is, no
     "character" of the input string must have any value > 255, as UTF-8
     does not allow that.

     The "utf8" flag therefore switches between two modes: disabled means
     you will get a Unicode string in Perl, enabled means you get an UTF-8
     encoded octet/binary string in Perl.

 "latin1" or "ascii" flags enabled
     With "latin1" (or "ascii") enabled, "encode" will escape characters
     with ordinal values > 255 (> 127 with "ascii") and encode the
     remaining characters as specified by the "utf8" flag.

     If "utf8" is disabled, then the result is also correctly encoded in
     those character sets (as both are proper subsets of Unicode, meaning
     that a Unicode string with all character values < 256 is the same
     thing as a ISO-8859-1 string, and a Unicode string with all character
     values < 128 is the same thing as an ASCII string in Perl).

     If "utf8" is enabled, you still get a correct UTF-8-encoded string,
     regardless of these flags, just some more characters will be escaped
     using "\uXXXX" then before.

     Note that ISO-8859-1-_e_n_c_o_d_e_d strings are not compatible with UTF-8
     encoding, while ASCII-encoded strings are. That is because the
     ISO-8859-1 encoding is NOT a subset of UTF-8 (despite the ISO-8859-1
     _c_o_d_e_s_e_t being a subset of Unicode), while ASCII is.

     Surprisingly, "decode" will ignore these flags and so treat all input
     values as governed by the "utf8" flag. If it is disabled, this allows
     you to decode ISO-8859-1- and ASCII-encoded strings, as both strict
     subsets of Unicode. If it is enabled, you can correctly decode UTF-8
     encoded strings.

     So neither "latin1" nor "ascii" are incompatible with the "utf8" flag
     - they only govern when the JSON output engine escapes a character or
     not.

     The main use for "latin1" is to relatively efficiently store binary
     data as JSON, at the expense of breaking compatibility with most JSON
     decoders.

     The main use for "ascii" is to force the output to not contain
     characters with values > 127, which means you can interpret the
     resulting string as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about
     any character set and 8-bit-encoding, and still get the same data
     structure back. This is useful when your channel for JSON transfer is
     not 8-bit clean or the encoding might be mangled in between (e.g. in
     mail), and works because ASCII is a proper subset of most 8-bit and
     multibyte encodings in use in the world.

BBUUGGSS #

 Please report bugs on a specific behavior of this module to RT or GitHub
 issues (preferred):

 <https://github.com/makamaka/JSON-PP/issues>

 <https://rt.cpan.org/Public/Dist/Display.html?Queue=JSON-PP>

 As for new features and requests to change common behaviors, please ask
 the author of JSON::XS (Marc Lehmann, <schmorp[at]schmorp.de>) first, by
 email (important!), to keep compatibility among JSON.pm backends.

 Generally speaking, if you need something special for you, you are
 advised to create a new module, maybe based on JSON::Tiny, which is
 smaller and written in a much cleaner way than this module.

SSEEEE AALLSSOO #

 The _j_s_o_n___p_p command line utility for quick experiments.

 JSON::XS, Cpanel::JSON::XS, and JSON::Tiny for faster alternatives.  JSON
 and JSON::MaybeXS for easy migration.

 JSON::PP::Compat5005 and JSON::PP::Compat5006 for older perl users.

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

 RFC7159 (<http://www.ietf.org/rfc/rfc7159.txt>)

 RFC8259 (<http://www.ietf.org/rfc/rfc8259.txt>)

AAUUTTHHOORR #

 Makamaka Hannyaharamitu, <makamaka[at]cpan.org>

CCUURRRREENNTT MMAAIINNTTAAIINNEERR #

 Kenichi Ishigaki, <ishigaki[at]cpan.org>

CCOOPPYYRRIIGGHHTT AANNDD LLIICCEENNSSEE #

 Copyright 2007-2016 by Makamaka Hannyaharamitu

 Most of the documentation is taken from JSON::XS by Marc Lehmann

 This library is free software; you can redistribute it and/or modify it
 under the same terms as Perl itself.

perl v5.36.3 2023-02-15 JSON::PP(3p)