JSON::PP(3p)

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

SYNOPSIS
 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;
 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
 $perl_scalar = $coder->decode ($unicode_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;

DESCRIPTION
This module is JSON::XS compatible pure Perl module. (Perl 5.8 or later is recommended)

JSON::XS is the fastest and most proper JSON module on CPAN. It is written by Marc Lehmann in C, so must be compiled and installed in the used environment.

JSON::PP is a pure-Perl module and has compatibility to JSON::XS.

  FEATURES

•   correct unicode handling

    This module knows how to handle Unicode (depending on Perl version).

    See to "A FEW NOTES ON UNICODE AND PERL" in JSON::XS and "UNICODE HANDLING ON PERLS".

•   round-trip integrity

    When you serialise a perl data structure using only data types supported by JSON and Perl, the deserialised data structure is identical on the Perl level. (e.g. the string "2.0" doesn't suddenly become "2" just because it looks like a number). There are minor exceptions to this, read the MAPPING section below to learn about those.

•   strict checking of JSON correctness

    There is no guessing, no generating of illegal JSON texts by default, and only JSON is accepted as input by default (the latter is a security feature). But when some options are set, loose chcking features are available.

FUNCTIONS
Basically, check to JSON or JSON::XS.

  encode_json
    $json_text = encode_json $perl_scalar

  decode_json
    $perl_scalar = decode_json $json_text

  JSON::PP::true
Returns JSON true value which is blessed object. It "isa" JSON::PP::Boolean object.

  JSON::PP::false
Returns JSON false value which is blessed object. It "isa" JSON::PP::Boolean object.

  JSON::PP::null
Returns "undef".

METHODS
Basically, check to JSON or JSON::XS.

  new
    $json = new JSON::PP

Rturns a new JSON::PP object that can be used to de/encode JSON strings.

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

    $enabled = $json->get_ascii

If $enable is true (or missing), then the encode method will not generate characters outside the code range 0..127. Any Unicode characters outside that range will be escaped using either a single \uXXXX or a double \uHHHH\uLLLLL escape sequence, as per RFC4627. (See to "OBJECT-ORIENTED INTERFACE" in JSON::XS).

In Perl 5.005, there is no character having high value (more than 255). See to "UNICODE HANDLING ON PERLS".

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.

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

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

    $enabled = $json->get_latin1

If $enable is true (or missing), then the encode method will encode the resulting JSON text as latin1 (or iso-8859-1), escaping any characters outside the code range 0..255.

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

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

See to "UNICODE HANDLING ON PERLS".

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

    $enabled = $json->get_utf8

If $enable is true (or missing), then the encode method will encode the JSON result into UTF-8, as required by many protocols, while the decode method expects to be handled an UTF-8-encoded string. Please note that UTF-8-encoded strings do not contain any characters outside the range 0..255, they are thus useful for bytewise/binary I/O.

(In Perl 5.005, any character outside the range 0..255 does not exist. See to "UNICODE HANDLING ON PERLS".)

In future versions, enabling this option might enable autodetection of the UTF-16 and UTF-32 encoding families, as described in RFC4627.

If $enable is false, then the encode method will return the JSON string as a (non-encoded) Unicode string, while decode expects thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs to be done yourself, e.g. using the Encode module.

Example, output UTF-16BE-encoded JSON:

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

Example, decode UTF-32LE-encoded JSON:

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

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

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

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

    $enabled = $json->get_indent

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

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

    $enabled = $json->get_space_before

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

    $enabled = $json->get_space_after

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

    $enabled = $json->get_relaxed

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

    $enabled = $json->get_canonical

If you want your own sorting routine, you can give a code referece or a subroutine name to "sort_by". See to "JSON::PP OWN METHODS".

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

    $enabled = $json->get_allow_nonref

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

    $enabled = $json->get_allow_unknown

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

    $enabled = $json->get_allow_blessed

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

    $enabled = $json->get_convert_blessed

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

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

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

    $enabled = $json->get_shrink

In JSON::XS, this flag resizes strings generated by either "encode" or "decode" to their minimum size possible. It will also try to downgrade any strings to octet-form if possible.

In JSON::PP, it is noop about resizing strings but tries "utf8::downgrade" to the returned string by "encode". See to utf8.

See to "OBJECT-ORIENTED INTERFACE" in JSON::XS

  max_depth
    $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.

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

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

When a large value (100 or more) was set and it de/encodes a deep nested object/text, it may raise a warning 'Deep recursion on subroutin' at the perl runtime phase.

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

    $max_size = $json->get_max_size

Set the maximum length a JSON text may have (in bytes) where decoding is being attempted. The default is 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 "SSECURITY CONSIDERATIONS" in JSON::XS for more info on why this is useful.

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

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

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

INCREMENTAL PARSING
Most of this section are copied and modified from "INCREMENTAL PARSING" in JSON::XS.

In some cases, there is the need for incremental parsing of JSON texts. This module does allow you to parse a JSON stream incrementally. It does so by accumulating text until it has a full JSON object, which it then can decode. This process is similar to using "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).

This module will only attempt to parse the JSON text once it is sure it has enough text to get a decisive result, using a very simple but truly incremental parser. This means that it sometimes won't stop as early as the full parser, for example, it doesn't detect parenthese mismatches. The only thing it guarantees is that it starts decoding as soon as a syntactically valid JSON text has been seen. This means you need to set resource limits (e.g. "max_size") to ensure the parser will stop parsing in the presence if syntax errors.

The following methods implement this incremental parser.

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

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

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

This is the central parsing function. It can both append new text and extract objects from the stream accumulated so far (both of these functions are optional).

If $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 one 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 errornous part). This is the most common way of using the method.

And finally, in list context, it will try to extract as many objects from the stream as it can find and return them, or the empty list otherwise. For this to work, there must be no separators between the JSON objects or arrays, instead they must be concatenated back-to-back. If an error occurs, an exception will be raised as in the scalar context case. Note that in this case, any previously-parsed JSON texts will be lost.

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

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

  incr_text
    $lvalue_string = $json->incr_text

This method returns the currently stored JSON fragment as an lvalue, that is, you can manipulate it. This only works when a preceding call to "incr_parse" in scalar context successfully returned an object. Under all other circumstances you must not call this function (I mean it. although in simple tests it might actually work, it will fail under real world conditions). As a special exception, you can also call this method before having parsed anything.

This function is useful in two cases: a) finding the trailing text after a JSON object or b) parsing multiple JSON objects separated by non-JSON text (such as commas).

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

In Perl 5.005, "lvalue" attribute is not available. You must write codes like the below:

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

  incr_skip
    $json->incr_skip

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

  incr_reset
    $json->incr_reset

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

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

See to "INCREMENTAL PARSING" in JSON::XS for examples.

JSON::PP OWN METHODS

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

If $enable is true (or missing), then "decode" will accept JSON strings quoted by single quotations that are invalid JSON format.

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

As same as the "relaxed" option, this option may be used to parse application-specific files written by humans.

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

If $enable is true (or missing), then "decode" will accept bare keys of JSON object that are invalid JSON format.

As same as the "relaxed" option, this option may be used to parse application-specific files written by humans.

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

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

If $enable is true (or missing), then "decode" 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.

On the contary, "encode" converts "Math::BigInt" objects and "Math::BigFloat" objects into JSON numbers with "allow_blessed" enable.

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

See to "MAPPING" in JSON::XS aboout the normal conversion of JSON number.

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

The unescaped [\x00-\x1f\x22\x2f\x5c] strings are invalid in JSON strings and the module doesn't allow to "decode" to these (except for \x2f). If $enable is true (or missing), then "decode" will accept these unescaped strings.

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

See "SSECURITY CONSIDERATIONS" in JSON::XS.

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

According to JSON Grammar, slash (U+002F) is escaped. But default JSON::PP (as same as JSON::XS) encodes strings without escaping slash.

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

  (OBSOLETED)as_nonblessed
    $json = $json->as_nonblessed

(OBSOLETED) If $enable is true (or missing), then "encode" will convert a blessed hash reference or a blessed array reference (contains other blessed references) into JSON members and arrays.

This feature is effective only when "allow_blessed" is enable.

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

JSON::XS indent space length is 3 and cannot be changed. JSON::PP set the indent space length with the given $length. The default is 3. The acceptable range is 0 to 15.

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

If $function_name or $subroutine_ref are set, its sort routine are used in encoding JSON objects.

   $js = $pc->sort_by(sub { $JSON::PP::a cmp $JSON::PP::b })->encode($obj);
   # is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);

   $js = $pc->sort_by('own_sort')->encode($obj);
   # is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);

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

As the sorting routine runs in the JSON::PP scope, the given subroutine name and the special variables $a, $b will begin 'JSON::PP::'.

If $integer is set, then the effect is same as "canonical" on.

INTERNAL
For developers.

PP_encode_box
    Returns

            {
                depth        => $depth,
                indent_count => $indent_count,
            }

PP_decode_box
    Returns

            {
                text    => $text,
                at      => $at,
                ch      => $ch,
                len     => $len,
                depth   => $depth,
                encoding      => $encoding,
                is_valid_utf8 => $is_valid_utf8,
            };

MAPPING
See to "MAPPING" in JSON::XS.

UNICODE HANDLING ON PERLS
If you do not know about Unicode on Perl well, please check "A FEW NOTES ON UNICODE AND PERL" in JSON::XS.

  Perl 5.8 and later
Perl can handle Unicode and the JSON::PP de/encode methods also work properly.

    $json->allow_nonref->encode(chr hex 3042);
    $json->allow_nonref->encode(chr hex 12345);

Reuturns "\u3042" and "\ud808\udf45" respectively.

    $json->allow_nonref->decode('"\u3042"');
    $json->allow_nonref->decode('"\ud808\udf45"');

Returns UTF-8 encoded strings with UTF8 flag, regarded as "U+3042" and "U+12345".

Note that the versions from Perl 5.8.0 to 5.8.2, Perl built-in "join" was broken, so JSON::PP wraps the "join" with a subroutine. Thus JSON::PP works slow in the versions.

  Perl 5.6
Perl can handle Unicode and the JSON::PP de/encode methods also work.

  Perl 5.005
Perl 5.005 is a byte sementics world -- all strings are sequences of bytes. That means the unicode handling is not available.

In encoding,

    $json->allow_nonref->encode(chr hex 3042);  # hex 3042 is 12354.
    $json->allow_nonref->encode(chr hex 12345); # hex 12345 is 74565.

Returns "B" and "E", as "chr" takes a value more than 255, it treats as "$value % 256", so the above codes are equivalent to :

    $json->allow_nonref->encode(chr 66);
    $json->allow_nonref->encode(chr 69);

In decoding,

    $json->decode('"\u00e3\u0081\u0082"');

The returned is a byte sequence "0xE3 0x81 0x82" for UTF-8 encoded japanese character ("HIRAGANA LETTER A"). And if it is represented in Unicode code point, "U+3042".

Next,

    $json->decode('"\u3042"');

We ordinary expect the returned value is a Unicode character "U+3042". But here is 5.005 world. This is "0xE3 0x81 0x82".

    $json->decode('"\ud808\udf45"');

This is not a character "U+12345" but bytes - "0xf0 0x92 0x8d 0x85".

TODO

speed
memory saving

SEE ALSO
Most of the document are copied and modified from JSON::XS doc.

JSON::XS

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

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

COPYRIGHT AND LICENSE
Copyright 2007-2010 by Makamaka Hannyaharamitu

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