use Cpanel::JSON::XS; # 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 = Cpanel::JSON::XS->new->ascii->pretty->allow_nonref; $pretty_printed_unencoded = $coder->encode ($perl_scalar); $perl_scalar = $coder->decode ($unicode_json_text); # Note that 5.6 misses most smart utf8 and encoding functionalities # of newer releases. # Note that L<JSON::MaybeXS> will automatically use Cpanel::JSON::XS # if available, at virtually no speed overhead either, so you should # be able to just: use JSON::MaybeXS; # and do the same things, except that you have a pure-perl fallback now. Note that this module will be replaced by a new JSON::Safe module soon, with the same API just guaranteed safe defaults.
As this is the n-th-something JSON module on CPAN, what was the reason to write yet another JSON module? While it seems there are many JSON modules, none of them correctly handle all corner cases, and in most cases their maintainers are unresponsive, gone missing, or not listening to bug reports for other reasons.
See below for the cPanel fork.
See MAPPING, below, on how Cpanel::JSON::XS maps perl values to JSON values and vice versa.
This module knows how to handle Unicode with Perl version higher than 5.8.5, documents how and when it does so, and even documents what ``correct'' means.
When you serialize a perl data structure using only data types supported by JSON and Perl, the deserialized 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.
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.
Compared to other JSON modules and other serializers such as Storable, this module usually compares favourably in terms of speed, too.
This module has both a simple functional interface as well as an object oriented interface.
You can choose between the most compact guaranteed-single-line format possible (nice for simple line-based protocols), a pure-ASCII format (for when your transport is not 8-bit clean, still supports the whole Unicode range), or a pretty-printed format (for when you want to read that stuff). Or you can combine those features in whatever way you like.
src repo: <https://github.com/rurban/Cpanel-JSON-XS> original: <http://cvs.schmorp.de/JSON-XS/>
RT: <https://github.com/rurban/Cpanel-JSON-XS/issues> or <https://rt.cpan.org/Public/Dist/Display.html?Queue=Cpanel-JSON-XS>
Changes to JSON::XS
- stricter decode_json() as documented. non-refs are disallowed.
added a 2nd optional argument. decode() honors now allow_nonref.
- fixed encode of numbers for dual-vars. Different string
representations are preserved, but numbers with temporary strings
which represent the same number are here treated as numbers, not
strings. Cpanel::JSON::XS is a bit slower, but preserves numeric
types better.
- numbers ending with .0 stray numbers, are not converted to
integers. [#63] dual-vars which are represented as number not
integer (42+``bar'' != 5.8.9) are now encoded as number (=> 42.0)
because internally it's now a NOK type. However !!1 which is
wrongly encoded in 5.8 as ``1''/1.0 is still represented as integer.
- different handling of inf/nan. Default now to null, optionally with
stringify_infnan() to ``inf''/``nan''. [#28, #32]
- added "binary" extension, non-JSON and non JSON parsable, allows
"\xNN" and "\NNN" sequences.
- 5.6.2 support; sacrificing some utf8 features (assuming bytes
all-over), no multi-byte unicode characters with 5.6.
- interop for true/false overloading. JSON::XS, JSON::PP and Mojo::JSON
representations for booleans are accepted and JSON::XS accepts
Cpanel::JSON::XS booleans [#13, #37]
Fixed overloading of booleans. Cpanel::JSON::XS::true stringifies again
to ``1'', not ``true'', analog to all other JSON modules.
- native boolean mapping of yes and no to true and false, as in YAML::XS.
In perl "!0" is yes, "!1" is no.
The JSON value true maps to 1, false maps to 0. [#39]
- support arbitrary stringification with encode, with convert_blessed
and allow_blessed.
- ithread support. Cpanel::JSON::XS is thread-safe, JSON::XS not
- is_bool can be called as method, JSON::XS::is_bool not.
- performance optimizations for threaded Perls
- relaxed mode, allowing many popular extensions
- additional fixes for:
- [cpan #88061] AIX atof without USE_LONG_DOUBLE - #10 unshare_hek crash - #7, #29 avoid re-blessing where possible. It fails in JSON::XS for READONLY values, i.e. restricted hashes. - #41 overloading of booleans, use the object not the reference. - #62 -Dusequadmath conversion and no SEGV. - #72 parsing of values followed \0, like 1\0 does fail. - #72 parsing of illegal unicode or non-unicode characters. - #96 locale-insensitive numeric conversion. - #154 numeric conversion fixed since 5.22, using the same strtold as perl5. - #167 sort tied hashes with canonical.
- public maintenance and bugtracker
- use ppport.h, sanify XS.xs comment styles, harness C coding style
- common::sense is optional. When available it is not used in the
published production module, just during development and testing.
- extended testsuite, passes all http://seriot.ch/parsing_json.html
tests. In fact it is the only know JSON decoder which does so,
while also being the fastest.
- support many more options and methods from JSON::PP:
stringify_infnan, allow_unknown, allow_stringify, allow_barekey,
encode_stringify, allow_bignum, allow_singlequote, sort_by
(partially), escape_slash, convert_blessed, ... optional
decode_json(, allow_nonref) arg.
relaxed implements allow_dupkeys.
- support all 5 unicode BOM's: UTF-8, UTF-16LE, UTF-16BE, UTF-32LE,
UTF-32BE, encoding internally to UTF-8.
This function call is functionally identical to:
$json_text = Cpanel::JSON::XS->new->utf8->encode ($perl_scalar, $json_type)
Except being faster.
For the type argument see Cpanel::JSON::XS::Type.
This function call is functionally identical to:
$perl_scalar = Cpanel::JSON::XS->new->utf8->decode ($json_text, $json_type)
except being faster.
Note that older decode_json versions in Cpanel::JSON::XS older than 3.0116 and JSON::XS did not set allow_nonref but allowed them due to a bug in the decoder.
If the new 2nd optional $allow_nonref argument is set and not false, the "allow_nonref" option will be set and the function will act is described as in the relaxed RFC 7159 allowing all values such as objects, arrays, strings, numbers, ``null'', ``true'', and ``false''. See "``OLD'' VS. ``NEW'' JSON (RFC 4627 VS. RFC 7159)" below, why you don't want to do that.
For the 3rd optional type argument see Cpanel::JSON::XS::Type.
See MAPPING, below, for more information on how JSON values are mapped to Perl.
The mutators for flags all return the JSON object again and thus calls can be chained:
my $json = Cpanel::JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
=> {"a": [1, 2]}
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 ENCODING/CODESET FLAG NOTES 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.
Cpanel::JSON::XS->new->ascii (1)->encode ([chr 0x10401]) => ["\ud801\udc01"]
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 ENCODING/CODESET FLAG NOTES 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.
Cpanel::JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
There is also a special logic for perl 5.6 and utf8. 5.6 encodes any string to utf-8 automatically when seeing a codepoint >= 0x80 and < 0x100. With the binary flag enabled decode the perl utf8 encoded string to the original byte encoding and encode this with "\xNN" escapes. This will result to the same encodings as with newer perls. But note that binary multi-byte codepoints with 5.6 will result in "illegal unicode character in binary string" errors, unlike with newer perls.
If $enable is false, then the "encode" method will smartly try to detect Unicode characters unless required by the JSON syntax or other flags and hex and octal sequences are forbidden.
See also the section ENCODING/CODESET FLAG NOTES later in this document.
The main use for this flag is to avoid the smart unicode detection and possible double encoding. The disadvantage is that the resulting JSON text is encoded in new "\xNN" and in latin1 characters and must correctly be treated as such when storing and transferring, a rare encoding for JSON. It will produce non-readable JSON strings in the browser. 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. The binary decoding method can also be used when an encoder produced a non-JSON conformant hex or octal encoding "\xNN" or "\NNN".
Cpanel::JSON::XS->new->binary->encode (["\x{89}\x{abc}"])
5.6: Error: malformed or illegal unicode character in binary string
>=5.8: ['\x89\xe0\xaa\xbc']
Cpanel::JSON::XS->new->binary->encode (["\x{89}\x{bc}"])
=> ["\x89\xbc"]
Cpanel::JSON::XS->new->binary->decode (["\x89\ua001"])
Error: malformed or illegal unicode character in binary string
Cpanel::JSON::XS->new->decode (["\x89"])
Error: illegal hex character in non-binary string
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 ENCODING/CODESET FLAG NOTES later in this document.
Example, output UTF-16BE-encoded JSON:
use Encode; $jsontext = encode "UTF-16BE", Cpanel::JSON::XS->new->encode ($object);
Example, decode UTF-32LE-encoded JSON:
use Encode; $object = Cpanel::JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
Example, pretty-print some simple structure:
my $json = Cpanel::JSON::XS->new->pretty(1)->encode ({a => [1,2]}) => { "a" : [ 1, 2 ] }
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.
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"}
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"}
If $enable is false (the default), then "decode" will only accept valid JSON texts.
Currently accepted extensions are:
JSON separates array elements and key-value pairs with commas. This can be annoying if you write JSON texts manually and want to be able to quickly append elements, so this extension accepts comma at the end of such items not just between them:
[
1,
2, <- this comma not normally allowed
]
{
"k1": "v1",
"k2": "v2", <- this comma not normally allowed
}
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...
]
Literal ASCII TAB characters are now allowed in strings (and treated as "\t") in relaxed mode. Despite JSON mandates, that TAB character is substituted for ``\t'' sequence.
[
"Hello\tWorld",
"Hello<TAB>World", # literal <TAB> would not normally be allowed
]
Single quotes are accepted instead of double quotes. See the ``allow_singlequote'' option.
{ "foo":'bar' }
{ 'foo':"bar" }
{ 'foo':'bar' }
Accept unquoted object keys instead of with mandatory double quotes. See the ``allow_barekey'' option.
{ foo:"bar" }
Allow decoding of duplicate keys in hashes. By default duplicate keys are forbidden. See <http://seriot.ch/parsing_json.php#24>: RFC 7159 section 4: ``The names within an object should be unique.'' See the ``allow_dupkeys'' option.
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 is now also done with tied hashes, contrary to JSON::XS. But note that with most large tied hashes stored as tree it is advised to sort the iterator already and don't sort the hash output here. Most such iterators are already sorted, as such e.g. DB_File with "DB_BTREE".
This setting has no effect when decoding JSON texts.
This setting has currently no effect on tied hashes.
If $enable is true (or missing), then "encode" will escape slashes, "\/".
This setting has no effect when decoding JSON texts.
$json = $json->unblessed_bool([$enable])
If $enable is true (or missing), then "decode" will return Perl non-object boolean variables (1 and 0) for JSON booleans ("true" and "false"). If $enable is false, then "decode" will return "JSON::PP::Boolean" objects for JSON booleans.
$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'});
This is also enabled with "relaxed". As same as the "relaxed" option, this option may be used to parse application-specific files written by humans.
$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.
Same as with the "relaxed" option, this option may be used to parse application-specific files written by humans.
$json->allow_barekey->decode('{foo:"bar"}');
$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 contrary, "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 ``MAPPING'' about the normal conversion of JSON number.
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 with enabled "allow_nonref", resulting in an invalid JSON text:
Cpanel::JSON::XS->new->allow_nonref->encode ("Hello, World!")
=> "Hello, World!"
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.
This option does not affect "decode" in any way.
This option is special to this module, it is not supported by other encoders. So it is not recommended to use it.
$json = $json->require_types([$enable])
If $enable is true (or missing), then "encode" will require either enabled "type_all_string" or second argument with supplied JSON types. See Cpanel::JSON::XS::Type. When "type_all_string" is not enabled or second argument is not provided (or is undef), then "encode" croaks. It also croaks when the type for provided structure in "encode" is incomplete.
$json = $json->type_all_string([$enable])
If $enable is true (or missing), then "encode" will always produce stable deterministic JSON string types in resulted output.
When $enable is false, then result of encoded JSON output may be different for different Perl versions and may depends on loaded modules.
This is useful it you need deterministic JSON types, independently of used Perl version and other modules, but do not want to write complicated type definitions for Cpanel::JSON::XS::Type.
The JSON spec allows duplicate name in objects but recommends to disable it, however with Perl hashes they are impossible, parsing JSON in Perl silently ignores duplicate names, using the last value found.
See <http://seriot.ch/parsing_json.php#24>: RFC 7159 section 4: ``The names within an object should be unique.''
If $enable is false (the default), then "encode" will throw an exception when it encounters a blessed object without "convert_blessed" and a "TO_JSON" method.
This setting has no effect on "decode".
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 same care must be taken with calling encode in stringify overloads (even if this works by luck in older perls) or other callbacks. 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".
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 serialize the object into a nonstandard tagged JSON value (that JSON decoders cannot decode).
It also causes "decode" to parse such tagged JSON values and deserialize 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.
When $coderef is omitted or undefined, any existing callback will be removed and "decode" will not change the deserialized hash in any way.
Example, convert all JSON objects into the integer 5:
my $js = Cpanel::JSON::XS->new->filter_json_object (sub { 5 });
# returns [5]
$js->decode ('[{}]')
# throw an exception because allow_nonref is not enabled
# so a lone 5 is not allowed.
$js->decode ('{"a":1, "b":2}');
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 $coderef is omitted or undefined, the corresponding callback will be disabled. There can only ever be one callback for a given key.
As this callback gets called less often then the "filter_json_object" one, decoding speed will not usually suffer as much. Therefore, single-key objects make excellent targets to serialize Perl objects into, especially as single-key JSON objects are as close to the type-tagged value concept as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not support this in any way, so you need to make sure your data never looks like a serialized Perl hash.
Typical names for the single object key are "__class_whatever__", or "$__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}:
Cpanel::JSON::XS
->new
->filter_json_single_key_object (__widget__ => sub {
$WIDGET{ $_[0] }
})
->decode ('{"__widget__": 5')
# this can be used with a TO_JSON method in some "widget" class
# for serialization to json:
sub WidgetBase::TO_JSON {
my ($self) = @_;
unless ($self->{id}) {
$self->{id} = ..get..some..id..;
$WIDGET{$self->{id}} = $self;
}
{ __widget__ => $self->{id} }
}
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 true (or missing), the string returned by "encode" will be shrunk-to-fit, while all strings generated by "decode" will also be shrunk-to-fit.
If $enable is false, then the normal perl allocation algorithms are used. If you work with your data, then this is likely to be faster.
In the future, this setting might control other things, such as converting strings that look like integers or floats into integers or floats internally (there is no difference on the Perl level), saving space.
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.
Note that nesting is implemented by recursion in C. The default value has been chosen to be as large as typical operating systems allow without crashing.
See ``SECURITY CONSIDERATIONS'', below, for more info on why this is useful.
If no argument is given, the limit check will be deactivated (same as when 0 is specified).
See ``SECURITY CONSIDERATIONS'', below, for more info on why this is useful.
"null": infnan_mode = 0. Similar to most JSON modules in other languages. Always null.
stringified: infnan_mode = 1. As in Mojo::JSON. Platform specific strings. Stringified via sprintf(%g), with double quotes.
inf/nan: infnan_mode = 2. As in JSON::XS, and older releases. Passes through platform dependent values, invalid JSON. Stringified via sprintf(%g), but without double quotes.
``inf/-inf/nan'': infnan_mode = 3. Platform independent inf/nan/-inf strings. No QNAN/SNAN/negative NAN support, unified to ``nan''. Much easier to detect, but may conflict with valid strings.
For the type argument see Cpanel::JSON::XS::Type.
JSON numbers and strings become simple Perl scalars. JSON arrays become Perl arrayrefs and JSON objects become Perl hashrefs. "true" becomes 1, "false" becomes 0 and "null" becomes "undef".
For the type argument see Cpanel::JSON::XS::Type.
This is useful if your JSON texts are not delimited by an outer protocol and you need to know where the JSON text ends.
Cpanel::JSON::XS->new->decode_prefix ("[1] the tail")
=> ([1], 3)
Cpanel::JSON::XS 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.
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 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 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 = Cpanel::JSON::XS->new->incr_parse ("[5][7][1,2]");
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).
The difference to "incr_reset" is that only text until the parse error occurred is removed.
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.
For example, is the string 1 a single JSON number, or is it simply the start of 12? Or is 12 a single JSON number, or the concatenation of 1 and 2? In neither case you can tell, and this is why Cpanel::JSON::XS takes the conservative route and disallows this case.
my $text = "[1,2,3] hello";
my $json = new Cpanel::JSON::XS;
my $obj = $json->incr_parse ($text)
or die "expected JSON object or array at beginning of string";
my $tail = $json->incr_text;
# $tail now contains " hello"
Easy, isn't it?
Now for a more complicated example: Imagine a hypothetical protocol where you read some requests from a TCP stream, and each request is a JSON array, without any separation between them (in fact, it is often useful to use newlines as ``separators'', as these get interpreted as whitespace at the start of the JSON text, which makes it possible to test said protocol with "telnet"...).
Here is how you'd do it (it is trivial to write this in an event-based manner):
my $json = new Cpanel::JSON::XS;
# read some data from the socket
while (sysread $socket, my $buf, 4096) {
# split and decode as many requests as possible
for my $request ($json->incr_parse ($buf)) {
# act on the $request
}
}
Another complicated example: Assume you have a string with JSON objects or arrays, all separated by (optional) comma characters (e.g. "[1],[2], [3]"). To parse them, we have to skip the commas between the JSON texts, and here is where the lvalue-ness of "incr_text" comes in useful:
my $text = "[1],[2], [3]";
my $json = new Cpanel::JSON::XS;
# void context, so no parsing done
$json->incr_parse ($text);
# now extract as many objects as possible. note the
# use of scalar context so incr_text can be called.
while (my $obj = $json->incr_parse) {
# do something with $obj
# now skip the optional comma
$json->incr_text =~ s/^ \s* , //x;
}
Now lets go for a very complex example: Assume that you have a gigantic JSON array-of-objects, many gigabytes in size, and you want to parse it, but you cannot load it into memory fully (this has actually happened in the real world :).
Well, you lost, you have to implement your own JSON parser. But Cpanel::JSON::XS can still help you: You implement a (very simple) array parser and let JSON decode the array elements, which are all full JSON objects on their own (this wouldn't work if the array elements could be JSON numbers, for example):
my $json = new Cpanel::JSON::XS;
# open the monster
open my $fh, "<bigfile.json"
or die "bigfile: $!";
# first parse the initial "["
for (;;) {
sysread $fh, my $buf, 65536
or die "read error: $!";
$json->incr_parse ($buf); # void context, so no parsing
# Exit the loop once we found and removed(!) the initial "[".
# In essence, we are (ab-)using the $json object as a simple scalar
# we append data to.
last if $json->incr_text =~ s/^ \s* \[ //x;
}
# now we have the skipped the initial "[", so continue
# parsing all the elements.
for (;;) {
# in this loop we read data until we got a single JSON object
for (;;) {
if (my $obj = $json->incr_parse) {
# do something with $obj
last;
}
# add more data
sysread $fh, my $buf, 65536
or die "read error: $!";
$json->incr_parse ($buf); # void context, so no parsing
}
# in this loop we read data until we either found and parsed the
# separating "," between elements, or the final "]"
for (;;) {
# first skip whitespace
$json->incr_text =~ s/^\s*//;
# if we find "]", we are done
if ($json->incr_text =~ s/^\]//) {
print "finished.\n";
exit;
}
# if we find ",", we can continue with the next element
if ($json->incr_text =~ s/^,//) {
last;
}
# if we find anything else, we have a parse error!
if (length $json->incr_text) {
die "parse error near ", $json->incr_text;
}
# else add more data
sysread $fh, my $buf, 65536
or die "read error: $!";
$json->incr_parse ($buf); # void context, so no parsing
}
This is a complex example, but most of the complexity comes from the fact that we are trying to be correct (bear with me if I am wrong, I never ran the above example :).
The BOM encoding is set only for one specific decode call, it does not change the state of the JSON object.
Warning: With perls older than 5.20 you need load the Encode module before loading a multibyte BOM, i.e. >= UTF-16. Otherwise an error is thrown. This is an implementation limitation and might get fixed later.
See <https://tools.ietf.org/html/rfc7159#section-8.1> ``JSON text SHALL be encoded in UTF-8, UTF-16, or UTF-32.''
``Implementations MUST NOT add a byte order mark to the beginning of a JSON text'', ``implementations (...) MAY ignore the presence of a byte order mark rather than treating it as an error''.
See also <http://www.unicode.org/faq/utf_bom.html#BOM>.
Beware that Cpanel::JSON::XS is currently the only JSON module which does accept and decode a BOM.
The latest JSON spec <https://www.greenbytes.de/tech/webdav/rfc8259.html#character.encoding> forbid the usage of UTF-16 or UTF-32, the character encoding is UTF-8. Thus in subsequent updates BOM's of UTF-16 or UTF-32 will throw an error.
For the more enlightened: note that in the following descriptions, lowercase perl refers to the Perl interpreter, while uppercase Perl refers to the abstract Perl language itself.
If the number consists of digits only, Cpanel::JSON::XS 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, "Cpanel::JSON::XS" only guarantees precision up to but not including the least significant bit.
Otherwise these JSON atoms become "JSON::PP::true" and "JSON::PP::false", respectively. They are "JSON::PP::Boolean" objects and 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 "Cpanel::JSON::XS::is_bool" function.
The other round, from perl to JSON, "!0" which is represented as "yes" becomes "true", and "!1" which is represented as "no" becomes "false".
Via Cpanel::JSON::XS::Type you can now even force negation in "encode", without overloading of "!":
my $false = Cpanel::JSON::XS::false;
print($json->encode([!$false], [JSON_TYPE_BOOL]));
=> [true]
See ``OBJECT SERIALIZATION'', below, for details.
With the option "allow_stringify", you can ignore the exception and return the stringification of the perl value.
With the option "allow_unknown", you can ignore the exception and return "null" instead.
encode_json [\"x"] # => cannot encode reference to scalar 'SCALAR(0x..)'
# unless the scalar is 0 or 1
encode_json [\0, \1] # yields [false,true]
allow_stringify->encode_json [\"x"] # yields "x" unlike JSON::PP
allow_unknown->encode_json [\"x"] # yields null as in JSON::PP
encode_json [Cpanel::JSON::XS::false, Cpanel::JSON::XS::true] # yields [false,true] encode_json [!1, !0], [JSON_TYPE_BOOL, JSON_TYPE_BOOL] # yields [false,true]
eq/ne comparisons with true, false:
false is eq to the empty string or the string 'false' or the special empty string "!!0" or "!1", i.e. "SV_NO", or the numbers 0 or 0.0.
true is eq to the string 'true' or to the special string "!0" (i.e. "SV_YES") or to the numbers 1 or 1.0.
See the "allow_blessed" and "convert_blessed" methods on various options on how to deal with this: basically, you can choose between throwing an exception, encoding the reference as if it weren't blessed, use the objects overloaded stringification method or provide your own serializer method.
If you want to have stable and deterministic types in JSON encoder then use Cpanel::JSON::XS::Type.
Alternative way for deterministic types is to use "type_all_string" method when all perl scalars are encoded to JSON strings.
Non-deterministic behavior is following: 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, but the two representations are for the same number print $value; encode_json [$value] # yields [5] # used as different string (non-matching dual-var) my $str = '0 but true'; my $num = 1 + $str; encode_json [$num, $str] # yields [1,"0 but true"] # undef becomes null encode_json [undef] # yields [null] # inf or nan becomes null, unless you answered # "Do you want to handle inf/nan as strings" with yes encode_json [9**9**9] # 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
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 $x *= 1; # same thing, the choice is yours.
Note that numerical precision has the same meaning as under Perl (so binary to decimal conversion follows the same rules as in Perl, which can differ to other languages). Also, your perl interpreter might expose extensions to the floating point numbers of your platform, such as infinities or NaN's - these cannot be represented in JSON, and thus null is returned instead. Optionally you can configure it to stringify inf and nan values.
SERIALIZATION
What happens when "Cpanel::JSON::XS" encounters a Perl object depends on the "allow_blessed", "convert_blessed" and "allow_tags" settings, which are used in this order:
This works by invoking the "FREEZE" method on the object, with the first argument being the object to serialize, and the second argument being the constant string "JSON" to distinguish it from other serializers.
The "FREEZE" method can return any number of values (i.e. zero or more). These values and the paclkage/classname of the object will then be encoded as a tagged JSON value in the following format:
("classname")[FREEZE return values...]
e.g.:
("URI")["http://www.google.com/"]
("MyDate")[2013,10,29]
("ImageData::JPEG")["Z3...VlCg=="]
For example, the hypothetical "My::Object" "FREEZE" method might use the objects "type" and "id" members to encode the object:
sub My::Object::FREEZE {
my ($self, $serializer) = @_;
($self->{type}, $self->{id})
}
For example, the following "TO_JSON" method will convert all URI objects to JSON strings when serialized. The fact that these values originally were URI objects is lost.
sub URI::TO_JSON {
my ($uri) = @_;
$uri->as_string
}
For example, the following "" method will convert all URI objects to JSON strings when serialized. The fact that these values originally were URI objects is lost.
package URI;
use overload '""' => sub { shift->as_string };
DESERIALIZATION
For deserialization there are only two cases to consider: either nonstandard tagging was used, in which case "allow_tags" decides, or objects cannot be automatically be deserialized, in which case you can use postprocessing or the "filter_json_object" or "filter_json_single_key_object" callbacks to get some real objects our of your JSON.
This section only considers the tagged value case: I a tagged JSON object is encountered during decoding and "allow_tags" is disabled, a parse error will result (as if tagged values were not part of the grammar).
If "allow_tags" is enabled, "Cpanel::JSON::XS" will look up the "THAW" method of the package/classname used during serialization (it will not attempt to load the package as a Perl module). If there is no such method, the decoding will fail with an error.
Otherwise, the "THAW" method is invoked with the classname as first argument, the constant string "JSON" as second argument, and all the values from the JSON array (the values originally returned by the "FREEZE" method) as remaining arguments.
The method must then return the object. While technically you can return any Perl scalar, you might have to enable the "enable_nonref" setting to make that work in all cases, so better return an actual blessed reference.
As an example, let's implement a "THAW" function that regenerates the "My::Object" from the "FREEZE" example earlier:
sub My::Object::THAW {
my ($class, $serializer, $type, $id) = @_;
$class->new (type => $type, id => $id)
}
See the ``SECURITY CONSIDERATIONS'' section below. Allowing external json objects being deserialized to perl objects is usually a very bad idea.
"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 encodes 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 and encodings at the same time, which can be confusing.
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).
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.
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-encoded 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 codeset 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", "binary" 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" or "binary" 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.
However, JSON is not a subset (and also not a superset of course) of ECMAscript (the standard) or javascript (whatever browsers actually implement).
If you want to use javascript's "eval" function to ``parse'' JSON, you might run into parse errors for valid JSON texts, or the resulting data structure might not be queryable:
One of the problems is that U+2028 and U+2029 are valid characters inside JSON strings, but are not allowed in ECMAscript string literals, so the following Perl fragment will not output something that can be guaranteed to be parsable by javascript's "eval":
use Cpanel::JSON::XS; print encode_json [chr 0x2028];
The right fix for this is to use a proper JSON parser in your javascript programs, and not rely on "eval" (see for example Douglas Crockford's json2.js parser).
If this is not an option, you can, as a stop-gap measure, simply encode to ASCII-only JSON:
use Cpanel::JSON::XS; print Cpanel::JSON::XS->new->ascii->encode ([chr 0x2028]);
Note that this will enlarge the resulting JSON text quite a bit if you have many non-ASCII characters. You might be tempted to run some regexes to only escape U+2028 and U+2029, e.g.:
# DO NOT USE THIS! my $json = Cpanel::JSON::XS->new->utf8->encode ([chr 0x2028]); $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028 $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029 print $json;
Note that this is a bad idea: the above only works for U+2028 and U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing javascript implementations, however, have issues with other characters as well - using "eval" naively simply will cause problems.
Another problem is that some javascript implementations reserve some property names for their own purposes (which probably makes them non-ECMAscript-compliant). For example, Iceweasel reserves the "__proto__" property name for its own purposes.
If that is a problem, you could parse try to filter the resulting JSON output for these property strings, e.g.:
$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
This works because "__proto__" is not valid outside of strings, so every occurrence of ""__proto__"\s*:" must be a string used as property name.
Unicode non-characters between U+FFFD and U+10FFFF are decoded either to the recommended U+FFFD REPLACEMENT CHARACTER (see Unicode PR #121: Recommended Practice for Replacement Characters), or in the binary or relaxed mode left as is, keeping the illegal non-characters as before.
Raw non-Unicode characters outside the valid unicode range fail now to parse, because ``A string is a sequence of zero or more Unicode characters'' RFC 7159 section 1 and "JSON text SHALL be encoded in Unicode RFC 7159 section 8.1. We use now the UTF8_DISALLOW_SUPER flag when parsing unicode.
If you know of other incompatibilities, please let me know.
my $to_yaml = Cpanel::JSON::XS->new->utf8->space_after (1); my $yaml = $to_yaml->encode ($ref) . "\n";
This will usually generate JSON texts that also parse as valid YAML.
JSON::XS is with Data::MessagePack and Sereal one of the fastest serializers, because JSON and JSON::XS do not support backrefs (no graph structures), only trees. Storable supports backrefs, i.e. graphs. Data::MessagePack encodes its data binary (as Storable) and supports only very simple subset of JSON.
First comes a comparison between various modules using a very short single-line JSON string (also available at <http://dist.schmorp.de/misc/json/short.json>).
{"method": "handleMessage", "params": ["user1",
"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
1, 0]}
It shows the number of encodes/decodes per second (JSON::XS uses the functional interface, while Cpanel::JSON::XS/2 uses the OO interface with pretty-printing and hash key sorting enabled, Cpanel::JSON::XS/3 enables shrink. JSON::DWIW/DS uses the deserialize function, while JSON::DWIW::FJ uses the from_json method). Higher is better:
module | encode | decode | --------------|------------|------------| JSON::DWIW/DS | 86302.551 | 102300.098 | JSON::DWIW/FJ | 86302.551 | 75983.768 | JSON::PP | 15827.562 | 6638.658 | JSON::Syck | 63358.066 | 47662.545 | JSON::XS | 511500.488 | 511500.488 | JSON::XS/2 | 291271.111 | 388361.481 | JSON::XS/3 | 361577.931 | 361577.931 | Storable | 66788.280 | 265462.278 | --------------+------------+------------+
That is, JSON::XS is almost six times faster than JSON::DWIW on encoding, about five times faster on decoding, and over thirty to seventy times faster than JSON's pure perl implementation. It also compares favourably to Storable for small amounts of data.
Using a longer test string (roughly 18KB, generated from Yahoo! Locals search API (<http://dist.schmorp.de/misc/json/long.json>).
module | encode | decode | --------------|------------|------------| JSON::DWIW/DS | 1647.927 | 2673.916 | JSON::DWIW/FJ | 1630.249 | 2596.128 | JSON::PP | 400.640 | 62.311 | JSON::Syck | 1481.040 | 1524.869 | JSON::XS | 20661.596 | 9541.183 | JSON::XS/2 | 10683.403 | 9416.938 | JSON::XS/3 | 20661.596 | 9400.054 | Storable | 19765.806 | 10000.725 | --------------+------------+------------+
Again, JSON::XS leads by far (except for Storable which non-surprisingly decodes a bit faster).
On large strings containing lots of high Unicode characters, some modules (such as JSON::PC) seem to decode faster than JSON::XS, but the result will be broken due to missing (or wrong) Unicode handling. Others refuse to decode or encode properly, so it was impossible to prepare a fair comparison table for that case.
For updated graphs see <https://github.com/Sereal/Sereal/wiki/Sereal-Comparison-Graphs>
When you have trouble decoding JSON generated by this module using other decoders, then it is very likely that you have an encoding mismatch or the other decoder is broken.
When decoding, "JSON::XS" is strict by default and will likely catch all errors. There are currently two settings that change this: "relaxed" makes "JSON::XS" accept (but not generate) some non-standard extensions, and "allow_tags" or "allow_blessed" will allow you to encode and decode Perl objects, at the cost of being totally insecure and not outputting valid JSON anymore.
JSON-XS-3.01 broke interoperability with JSON-2.90 with booleans. See JSON.
Cpanel::JSON::XS needs to know the JSON and JSON::XS versions to be able work with those objects, especially when encoding a booleans like "{"is_true":true}". So you need to load these modules before.
true/false overloading and boolean representations are supported.
JSON::XS and JSON::PP representations are accepted and older JSON::XS accepts Cpanel::JSON::XS booleans. All JSON modules JSON, JSON, PP, JSON::XS, Cpanel::JSON::XS produce JSON::PP::Boolean objects, just Mojo and JSON::YAJL not. Mojo produces Mojo::JSON::_Bool and JSON::YAJL::Parser just an unblessed IV.
Cpanel::JSON::XS accepts JSON::PP::Boolean and Mojo::JSON::_Bool objects as booleans.
I cannot think of any reason to still use JSON::XS anymore.
# if your FREEZE methods return no values, you need this replace first:
$json =~ s/\( \s* (" (?: [^\\":,]+|\\.|::)* ") \s* \) \s* \[\s*\]/[$1]/gx;
# this works for non-empty constructor arg lists:
$json =~ s/\( \s* (" (?: [^\\":,]+|\\.|::)* ") \s* \) \s* \[/[$1,/gx;
And here is a less readable version that is easy to adapt to other languages:
$json =~ s/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/[$1,/g;
Here is an ECMAScript version (same regex):
json = json.replace (/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/g, "[$1,");
Since this syntax converts to standard JSON arrays, it might be hard to distinguish serialized objects from normal arrays. You can prepend a ``magic number'' as first array element to reduce chances of a collision:
$json =~ s/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g;
And after decoding the JSON text, you could walk the data structure looking for arrays with a first element of "XU1peReLzT4ggEllLanBYq4G9VzliwKF".
The same approach can be used to create the tagged format with another encoder. First, you create an array with the magic string as first member, the classname as second, and constructor arguments last, encode it as part of your JSON structure, and then:
$json =~ s/\[\s*"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s*,\s*("([^\\":,]+|\\.|::)*")\s*,/($1)[/g;
Again, this has some limitations - the magic string must not be encoded with character escapes, and the constructor arguments must be non-empty.
As far as I can see, you can get partial compatibility when parsing by using "->allow_nonref". However, consider the security implications of doing so.
I haven't decided yet when to break compatibility with RFC4627 by default (and potentially leave applications insecure) and change the default to follow RFC7159, but application authors are well advised to call "->allow_nonref(0)" even if this is the current default, if they cannot handle non-reference values, in preparation for the day when the default will change.
It is trivial for any attacker to create such serialized objects in JSON and trick perl into expanding them, thereby triggering certain methods. Watch <https://www.youtube.com/watch?v=Gzx6KlqiIZE> for an exploit demo for ``CVE-2015-1592 SixApart MovableType Storable Perl Code Execution'' for a deserializer which expands objects. Deserializing even coderefs (methods, functions) or external data would be considered the most dangerous.
Security relevant overview of serializers regarding deserializing objects by default:
Objects Coderefs External Data
Data::Dumper YES YES YES
Storable YES NO (def) NO
Sereal YES NO NO
YAML YES NO NO
B::C YES YES YES
B::Bytecode YES YES YES
BSON YES YES NO
JSON::SL YES NO YES
JSON NO (def) NO NO
Data::MessagePack NO NO NO
XML NO NO YES
Pickle YES YES YES
PHP Deserialize YES NO NO
When you are using JSON in a protocol, talking to untrusted potentially hostile creatures requires relatively few measures.
First of all, your JSON decoder should be secure, that is, should not have any buffer overflows. Obviously, this module should ensure that.
Second, you need to avoid resource-starving attacks. That means you should limit the size of JSON texts you accept, or make sure then when your resources run out, that's just fine (e.g. by using a separate process that can crash safely). The size of a JSON text in octets or characters is usually a good indication of the size of the resources required to decode it into a Perl structure. While JSON::XS can check the size of the JSON text, it might be too late when you already have it in memory, so you might want to check the size before you accept the string.
Third, Cpanel::JSON::XS recurses using the C stack when decoding objects and arrays. The C stack is a limited resource: for instance, on my amd64 machine with 8MB of stack size I can decode around 180k nested arrays but only 14k nested JSON objects (due to perl itself recursing deeply on croak to free the temporary). If that is exceeded, the program crashes. To be conservative, the default nesting limit is set to 512. If your process has a smaller stack, you should adjust this setting accordingly with the "max_depth" method.
Also keep in mind that Cpanel::JSON::XS might leak contents of your Perl data structures in its error messages, so when you serialize sensitive information you might want to make sure that exceptions thrown by JSON::XS will not end up in front of untrusted eyes.
If you are using Cpanel::JSON::XS to return packets to consumption by JavaScript scripts in a browser you should have a look at <http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to see whether you are vulnerable to some common attack vectors (which really are browser design bugs, but it is still you who will have to deal with it, as major browser developers care only for features, not about getting security right). You might also want to also look at Mojo::JSON special escape rules to prevent from XSS attacks.
my $json = JSON::XS->new->allow_nonref; $text = $json->encode ($data); $data = $json->decode ($text);
The long version: JSON being an important and supposedly stable format, the IETF standardized it as RFC 4627 in 2006. Unfortunately the inventor of JSON Douglas Crockford unilaterally changed the definition of JSON in javascript. Rather than create a fork, the IETF decided to standardize the new syntax (apparently, so I as told, without finding it very amusing).
The biggest difference between the original JSON and the new JSON is that the new JSON supports scalars (anything other than arrays and objects) at the top-level of a JSON text. While this is strictly backwards compatible to older versions, it breaks a number of protocols that relied on sending JSON back-to-back, and is a minor security concern.
For example, imagine you have two banks communicating, and on one side, the JSON coder gets upgraded. Two messages, such as 10 and 1000 might then be confused to mean 101000, something that couldn't happen in the original JSON, because neither of these messages would be valid JSON.
If one side accepts these messages, then an upgrade in the coder on either side could result in this becoming exploitable.
This module has always allowed these messages as an optional extension, by default disabled. The security concerns are the reason why the default is still disabled, but future versions might/will likely upgrade to the newer RFC as default format, so you are advised to check your implementation and/or override the default with "->allow_nonref (0)" to ensure that future versions are safe.
From Version 4.00 - 4.19 you couldn't encode true with threads::shared magic.
Since the JSON::XS author refuses to use a public bugtracker and prefers private emails, we use the tracker at github, so you might want to report any issues twice. Once in private to MLEHMANN to be fixed in JSON::XS and one to our the public tracker. Issues fixed by JSON::XS with a new release will also be backported to Cpanel::JSON::XS and 5.6.2, as long as cPanel relies on 5.6.2 and Cpanel::JSON::XS as our serializer of choice.
<https://github.com/rurban/Cpanel-JSON-XS/issues>
JSON, JSON::XS, JSON::MaybeXS, Mojo::JSON, Mojo::JSON::MaybeXS, JSON::SL, JSON::DWIW, JSON::YAJL, JSON::Any, Test::JSON, Locale::Wolowitz, <https://metacpan.org/search?q=JSON>
<https://tools.ietf.org/html/rfc7159>
<https://tools.ietf.org/html/rfc4627>
Marc Lehmann <schmorp@schmorp.de>, http://home.schmorp.de/