[ViewVC] Diff of: cvs/JSON-XS/XS.pm

Comparing JSON-XS/XS.pm (file contents):
Revision 1.147 by root, Tue Oct 29 00:19:08 2013 UTC vs.
Revision 1.170 by root, Thu Nov 15 22:35:35 2018 UTC

 This module converts Perl data structures to JSON and vice versa. Its
 primary goal is to be I<correct> and its secondary goal is to be
 I<fast>. To reach the latter goal it was written in C.
-Beginning with version 2.0 of the JSON module, when both JSON and
-JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
-overridden) with no overhead due to emulation (by inheriting constructor
-and methods). If JSON::XS is not available, it will fall back to the
-compatible JSON::PP module as backend, so using JSON instead of JSON::XS
-gives you a portable JSON API that can be fast when you need and doesn't
-require a C compiler when that is a problem.
-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 MAPPING, below, on how JSON::XS maps perl values to JSON values and
 vice versa.
 =head2 FEATURES
-=over 4
+=over
 =item * correct Unicode handling
 This module knows how to handle Unicode, documents how and when it does
 so, and even documents what "correct" means.
 package JSON::XS;
 use common::sense;
-our $VERSION = '3.0';
+our $VERSION = '4.0';
 our @ISA = qw(Exporter);
 our @EXPORT = qw(encode_json decode_json);
 use Exporter;
 =head1 FUNCTIONAL INTERFACE
 The following convenience methods are provided by this module. They are
 exported by default:
-=over 4
+=over
 =item $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.
 Except being faster.
 =item $perl_scalar = decode_json $json_text
-The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
+The opposite of C<encode_json>: expects a UTF-8 (binary) string and tries
-to parse that as an UTF-8 encoded JSON text, returning the resulting
+to parse that as a UTF-8 encoded JSON text, returning the resulting
 reference. Croaks on error.
 This function call is functionally identical to:
    $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
 =head1 A FEW NOTES ON UNICODE AND PERL
 Since this often leads to confusion, here are a few very clear words on
 how Unicode works in Perl, modulo bugs.
-=over 4
+=over
 =item 1. Perl strings can store characters with ordinal values > 255.
 This enables you to store Unicode characters as single characters in a
 Perl string - very natural.
 =head1 OBJECT-ORIENTED INTERFACE
 The object oriented interface lets you configure your own encoding or
 decoding style, within the limits of supported formats.
-=over 4
+=over
 =item $json = new JSON::XS
 Creates a new JSON::XS object that can be used to de/encode JSON
-strings. All boolean flags described below are by default I<disabled>.
+strings. All boolean flags described below are by default I<disabled>
+(with the exception of C<allow_nonref>, which defaults to I<enabled> since
+version C<4.0>).
 The mutators for flags all return the JSON object again and thus calls can
 be chained:
    my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
 =item $enabled = $json->get_utf8
 If C<$enable> is true (or missing), then the C<encode> method will encode
 the JSON result into UTF-8, as required by many protocols, while the
-C<decode> method expects to be handled an UTF-8-encoded string.  Please
+C<decode> method expects to be handed a UTF-8-encoded string.  Please
 note that UTF-8-encoded strings do not contain any characters outside the
 range C<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.
 =item $enabled = $json->get_relaxed
 If C<$enable> is true (or missing), then C<decode> will accept some
 extensions to normal JSON syntax (see below). C<encode> will not be
-affected in anyway. I<Be aware that this option makes you accept invalid
+affected in any way. I<Be aware that this option makes you accept invalid
 JSON texts as if they were valid!>. I suggest only to use this option to
 parse application-specific files written by humans (configuration files,
 resource files etc.)
 If C<$enable> is false (the default), then C<decode> will only accept
 valid JSON texts.
 Currently accepted extensions are:
-=over 4
+=over
 =item * list items can have an end-comma
 JSON I<separates> array elements and key-value pairs with commas. This
 can be annoying if you write JSON texts manually and want to be able to
   [
      1, # this comment not allowed in JSON
         # neither this one...
   ]
+=item * literal ASCII TAB characters in strings
+Literal ASCII TAB characters are now allowed in strings (and treated as
+C<\t>).
+  [
+     "Hello\tWorld",
+     "Hello<TAB>World", # literal <TAB> would not normally be allowed
+  ]
 =back
 =item $json = $json->canonical ([$enable])
 =item $enabled = $json->get_canonical
 =item $json = $json->allow_nonref ([$enable])
 =item $enabled = $json->get_allow_nonref
+Unlike other boolean options, this opotion is enabled by default beginning
+with version C<4.0>. See L<SECURITY CONSIDERATIONS> for the gory details.
 If C<$enable> is true (or missing), then the C<encode> method can convert a
 non-reference into its corresponding string, number or null JSON value,
 which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
 values instead of croaking.
 If C<$enable> is false, then the C<encode> method will croak if it isn't
 passed an arrayref or hashref, as JSON texts must either be an object
 or array. Likewise, C<decode> will croak if given something that is not a
 JSON object or array.
-Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
+Example, encode a Perl scalar as JSON value without enabled C<allow_nonref>,
-resulting in an invalid JSON text:
+resulting in an error:
-   JSON::XS->new->allow_nonref->encode ("Hello, World!")
+   JSON::XS->new->allow_nonref (0)->encode ("Hello, World!")
-   => "Hello, World!"
+   => hash- or arrayref expected...
 =item $json = $json->allow_unknown ([$enable])
 =item $enabled = $json->get_allow_unknown
 =item $json = $json->convert_blessed ([$enable])
 =item $enabled = $json->get_convert_blessed
-See "OBJECT SERIALISATION" for details.
+See L<OBJECT SERIALISATION> for details.
 If C<$enable> is true (or missing), then C<encode>, upon encountering a
 blessed object, will check for the availability of the C<TO_JSON> method
 on the object's class. If found, it will be called in scalar context and
 the resulting scalar will be encoded instead of the object.
 This setting has no effect on C<decode>.
 =item $json = $json->allow_tags ([$enable])
-=item $enabled = $json->allow_tags
+=item $enabled = $json->get_allow_tags
-See "OBJECT SERIALISATION" for details.
+See L<OBJECT SERIALISATION> for details.
 If C<$enable> is true (or missing), then C<encode>, upon encountering a
 blessed object, will check for the availability of the C<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).
 in C<decode>, as if tags were not part of the grammar.
 =item $json = $json->filter_json_object ([$coderef->($hashref)])
 When C<$coderef> is specified, it will be called from C<decode> each
-time it decodes a JSON object. The only argument is a reference to the
+time it decodes a JSON object. The only argument is a reference to
-newly-created hash. If the code references returns a single scalar (which
+the newly-created hash. If the code reference returns a single scalar
-need not be a reference), this value (i.e. a copy of that scalar to avoid
+(which need not be a reference), this value (or rather a copy of it) is
-aliasing) is inserted into the deserialised data structure. If it returns
+inserted into the deserialised data structure. If it returns an empty
-an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
+list (NOTE: I<not> C<undef>, which is a valid scalar), the original
-original deserialised hash will be inserted. This setting can slow down
+deserialised hash will be inserted. This setting can slow down decoding
-decoding considerably.
+considerably.
 When C<$coderef> is omitted or undefined, any existing callback will
 be removed and C<decode> will not change the deserialised hash in any
 way.
 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::XS->new->decode_prefix ("[1] the tail")
-   => ([], 3)
+   => ([1], 3)
 =back
 =head1 INCREMENTAL PARSING
 to set resource limits (e.g. C<max_size>) to ensure the parser will stop
 parsing in the presence if syntax errors.
 The following methods implement this incremental parser.
-=over 4
+=over
 =item [void, scalar or list context] = $json->incr_parse ([$string])
 This is the central parsing function. It can both append new text and
 extract objects from the stream accumulated so far (both of these
 C<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
+otherwise. For this to work, there must be no separators (other than
-objects or arrays, instead they must be concatenated back-to-back. If
+whitespace) between the JSON objects or arrays, instead they must be
-an error occurs, an exception will be raised as in the scalar context
+concatenated back-to-back. If an error occurs, an exception will be
-case. Note that in this case, any previously-parsed JSON texts will be
+raised as in the scalar context case. Note that in this case, any
-lost.
+previously-parsed JSON texts will be lost.
 Example: Parse some JSON arrays/objects in a given string and return
 them.
    my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
 all other circumstances you must not call this function (I mean it.
 although in simple tests it might actually work, it I<will> fail under
 real world conditions). As a special exception, you can also call this
 method before having parsed anything.
+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).
 =item $json->incr_skip
 =back
 =head2 LIMITATIONS
-All options that affect decoding are supported, except
+The incremental parser is a non-exact parser: it works by gathering as
-C<allow_nonref>. The reason for this is that it cannot be made to work
+much text as possible that I<could> be a valid JSON text, followed by
-sensibly: JSON objects and arrays are self-delimited, i.e. you can
+trying to decode it.
-concatenate them back to back and still decode them perfectly. This does
-not hold true for JSON numbers, however.
-For example, is the string C<1> a single JSON number, or is it simply the
+That means it sometimes needs to read more data than strictly necessary to
-start of C<12>? Or is C<12> a single JSON number, or the concatenation
+diagnose an invalid JSON text. For example, after parsing the following
-of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
+fragment, the parser I<could> stop with an error, as this fragment
-takes the conservative route and disallows this case.
+I<cannot> be the beginning of a valid JSON text:
+   [,
+In reality, hopwever, the parser might continue to read data until a
+length limit is exceeded or it finds a closing bracket.
 =head2 EXAMPLES
 Some examples will make all this clearer. First, a simple example that
 works similarly to C<decode_prefix>: We want to decode the JSON object at
 refers to the abstract Perl language itself.
 =head2 JSON -> PERL
-=over 4
+=over
 =item 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).
 Another nonstandard extension to the JSON syntax, enabled with the
 C<allow_tags> setting, are tagged values. In this implementation, the
 I<tag> must be a perl package/class name encoded as a JSON string, and the
 I<value> must be a JSON array encoding optional constructor arguments.
-See "OBJECT SERIALISATION", below, for details.
+See L<OBJECT SERIALISATION>, below, for details.
 =back
 =head2 PERL -> JSON
 The mapping from Perl to JSON is slightly more difficult, as Perl is a
 truly typeless language, so we can only guess which JSON type is meant by
 a Perl value.
-=over 4
+=over
 =item hash references
 Perl hash references become JSON objects. As there is no inherent
 ordering in hash keys (or JSON objects), they will usually be encoded
 directly if you want.
 =item blessed objects
 Blessed objects are not directly representable in JSON, but C<JSON::XS>
-allows various ways of handling objects. See "OBJECT SERIALISATION",
+allows various ways of handling objects. See L<OBJECT SERIALISATION>,
 below, for details.
 =item simple scalars
 Simple Perl scalars (any scalar that is not a reference) are the most
 What happens when C<JSON::XS> encounters a Perl object depends on the
 C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are
 used in this order:
-=over 4
+=over
-=item 1. C<allow_tags> is enabled and object has a C<FREEZE> method.
+=item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method.
 In this case, C<JSON::XS> uses the L<Types::Serialiser> object
 serialisation protocol to create a tagged JSON value, using a nonstandard
 extension to the JSON syntax.
 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 C<My::Object> C<FREEZE> method might use the
 objects C<type> and C<id> members to encode the object:
    sub My::Object::FREEZE {
       my ($self, $serialiser) = @_;
       ($self->{type}, $self->{id})
    }
-=item 2. C<convert_blessed> is enabled and object has a C<TO_JSON> method.
+=item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method.
 In this case, the C<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.
 takes those codepoint numbers and I<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 I<and> encodings at
 the same time, which can be confusing.
-=over 4
+=over
 =item C<utf8> flag disabled
 When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
 and expect Unicode strings, that is, characters with high ordinal Unicode
 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 C<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
+will get a Unicode string in Perl, enabled means you get a UTF-8 encoded
 octet/binary string in Perl.
 =item C<latin1> or C<ascii> flags enabled
 With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
 general you should not try to generate YAML with a JSON generator or vice
 versa, or try to parse JSON with a YAML parser or vice versa: chances are
 high that you will run into severe interoperability problems when you
 least expect it.
-=over 4
+=over
 =item (*)
 I have been pressured multiple times by Brian Ingerson (one of the
 authors of the YAML specification) to remove this paragraph, despite him
 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).
+=head2 "OLD" VS. "NEW" JSON (RFC4627 VS. RFC7159)
+JSON originally required JSON texts to represent an array or object -
+scalar values were explicitly not allowed. This has changed, and versions
+of JSON::XS beginning with C<4.0> reflect this by allowing scalar values
+by default.
+One reason why one might not want this is that this removes a fundamental
+property of JSON texts, namely that they are self-delimited and
+self-contained, or in other words, you could take any number of "old"
+JSON texts and paste them together, and the result would be unambiguously
+parseable:
+   [1,3]{"k":5}[][null] # four JSON texts, without doubt
+By allowing scalars, this property is lost: in the following example, is
+this one JSON text (the number 12) or two JSON texts (the numbers 1 and
+2):
+   12    # could be 12, or 1 and 2
+Another lost property of "old" JSON is that no lookahead is required to
+know the end of a JSON text, i.e. the JSON text definitely ended at the
+last C<]> or C<}> character, there was no need to read extra characters.
+For example, a viable network protocol with "old" JSON was to simply
+exchange JSON texts without delimiter. For "new" JSON, you have to use a
+suitable delimiter (such as a newline) after every JSON text or ensure you
+never encode/decode scalar values.
+Most protocols do work by only transferring arrays or objects, and the
+easiest way to avoid problems with the "new" JSON definition is to
+explicitly disallow scalar values in your encoder and decoder:
+   $json_coder = JSON::XS->new->allow_nonref (0)
+This is a somewhat unhappy situation, and the blame can fully be put on
+JSON's inmventor, Douglas Crockford, who unilaterally changed the format
+in 2006 without consulting the IETF, forcing the IETF to either fork the
+format or go with it (as I was told, the IETF wasn't amused).
+=head1 RELATIONSHIP WITH I-JSON
+JSON is a somewhat sloppily-defined format - it carries around obvious
+Javascript baggage, such as not really defining number range, probably
+because Javascript only has one type of numbers: IEEE 64 bit floats
+("binary64").
+For this reaosn, RFC7493 defines "Internet JSON", which is a restricted
+subset of JSON that is supposedly more interoperable on the internet.
+While C<JSON::XS> does not offer specific support for I-JSON, it of course
+accepts valid I-JSON and by default implements some of the limitations
+of I-JSON, such as parsing numbers as perl numbers, which are usually a
+superset of binary64 numbers.
+To generate I-JSON, follow these rules:
+=over
+=item * always generate UTF-8
+I-JSON must be encoded in UTF-8, the default for C<encode_json>.
+=item * numbers should be within IEEE 754 binary64 range
+Basically all existing perl installations use binary64 to represent
+floating point numbers, so all you need to do is to avoid large integers.
+=item * objects must not have duplicate keys
+This is trivially done, as C<JSON::XS> does not allow duplicate keys.
+=item * do not generate scalar JSON texts, use C<< ->allow_nonref (0) >>
+I-JSON strongly requests you to only encode arrays and objects into JSON.
+=item * times should be strings in ISO 8601 format
+There are a myriad of modules on CPAN dealing with ISO 8601 - search for
+C<ISO8601> on CPAN and use one.
+=item * encode binary data as base64
+While it's tempting to just dump binary data as a string (and let
+C<JSON::XS> do the escaping), for I-JSON, it's I<recommended> to encode
+binary data as base64.
+=back
+There are some other considerations - read RFC7493 for the details if
+interested.
 =head1 INTEROPERABILITY WITH OTHER MODULES
 C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
 constants. That means that the JSON true and false values will be
-comaptible to true and false values of iother modules that do the same,
+comaptible to true and false values of other modules that do the same,
 such as L<JSON::PP> and L<CBOR::XS>.
+=head1 INTEROPERABILITY WITH OTHER JSON DECODERS
+As long as you only serialise data that can be directly expressed in JSON,
+C<JSON::XS> is incapable of generating invalid JSON output (modulo bugs,
+but C<JSON::XS> has found more bugs in the official JSON testsuite (1)
+than the official JSON testsuite has found in C<JSON::XS> (0)).
+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, C<JSON::XS> is strict by default and will likely catch all
+errors. There are currently two settings that change this: C<relaxed>
+makes C<JSON::XS> accept (but not generate) some non-standard extensions,
+and C<allow_tags> will allow you to encode and decode Perl objects, at the
+cost of not outputting valid JSON anymore.
+=head2 TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS
+When you use C<allow_tags> to use the extended (and also nonstandard and
+invalid) JSON syntax for serialised objects, and you still want to decode
+the generated When you want to serialise objects, you can run a regex
+to replace the tagged syntax by standard JSON arrays (it only works for
+"normal" package names without comma, newlines or single colons). First,
+the readable Perl version:
+   # 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 serialised 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
+C<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.
-=head1 THREADS
+=head1 (I-)THREADS
-This module is I<not> guaranteed to be thread safe and there are no
+This module is I<not> guaranteed to be ithread (or MULTIPLICITY-) safe
-plans to change this until Perl gets thread support (as opposed to the
+and there are no plans to change this. Note that perl's builtin so-called
-horribly slow so-called "threads" which are simply slow and bloated
+threads/ithreads are officially deprecated and should not be used.
-process simulations - use fork, it's I<much> faster, cheaper, better).
-(It might actually work, but you have been warned).
 =head1 THE PERILS OF SETLOCALE
 Sometimes people avoid the Perl locale support and directly call the
 categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
 If you need C<LC_NUMERIC>, you should enable it only around the code that
 actually needs it (avoiding stringification of numbers), and restore it
 afterwards.
+=head1 SOME HISTORY
+At the time this module was created there already were a number of JSON
+modules available on CPAN, so what was the reason to write yet another
+JSON module? While it seems there are many JSON modules, none of them
+correctly handled all corner cases, and in most cases their maintainers
+are unresponsive, gone missing, or not listening to bug reports for other
+reasons.
+Beginning with version 2.0 of the JSON module, when both JSON and
+JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
+overridden) with no overhead due to emulation (by inheriting constructor
+and methods). If JSON::XS is not available, it will fall back to the
+compatible JSON::PP module as backend, so using JSON instead of JSON::XS
+gives you a portable JSON API that can be fast when you need it and
+doesn't require a C compiler when that is a problem.
+Somewhere around version 3, this module was forked into
+C<Cpanel::JSON::XS>, because its maintainer had serious trouble
+understanding JSON and insisted on a fork with many bugs "fixed" that
+weren't actually bugs, while spreading FUD about this module without
+actually giving any details on his accusations. You be the judge, but
+in my personal opinion, if you want quality, you will stay away from
+dangerous forks like that.
 =head1 BUGS
 While the goal of this module is to be correct, that unfortunately does

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Comparing JSON-XS/XS.pm (file contents): Revision 1.147 by root, Tue Oct 29 00:19:08 2013 UTC vs. Revision 1.170 by root, Thu Nov 15 22:35:35 2018 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.147 by root, Tue Oct 29 00:19:08 2013 UTC vs.
Revision 1.170 by root, Thu Nov 15 22:35:35 2018 UTC