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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.23 by root, Sun Mar 25 21:19:13 2007 UTC vs.
Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC

  # exported functions, they croak on error
  # and expect/generate UTF-8
  $utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
  $perl_hash_or_arrayref  = from_json $utf8_encoded_json_text;
- # objToJson and jsonToObj aliases to to_json and from_json
- # are exported for compatibility to the JSON module,
- # but should not be used in new code.
  # OO-interface
  $coder = JSON::XS->new->ascii->pretty->allow_nonref;
  $pretty_printed_unencoded = $coder->encode ($perl_scalar);
 package JSON::XS;
 use strict;
-BEGIN {
-   our $VERSION = '0.8';
+our $VERSION = '1.4';
-   our @ISA = qw(Exporter);
+our @ISA = qw(Exporter);
-   our @EXPORT = qw(to_json from_json objToJson jsonToObj);
+our @EXPORT = qw(to_json from_json);
-   require Exporter;
-   require XSLoader;
+use Exporter;
-   XSLoader::load JSON::XS::, $VERSION;
+use XSLoader;
-}
 =head1 FUNCTIONAL INTERFACE
 The following convinience methods are provided by this module. They are
 exported by default:
 This function call is functionally identical to:
    $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
 except being faster.
+=item $is_boolean = JSON::XS::is_bool $scalar
+Returns true if the passed scalar represents either JSON::XS::true or
+JSON::XS::false, two constants that act like C<1> and C<0>, respectively
+and are used to represent JSON C<true> and C<false> values in Perl.
+See MAPPING, below, for more information on how JSON values are mapped to
+Perl.
 =back
 =head1 OBJECT-ORIENTED INTERFACE
 If C<$enable> is true (or missing), then the C<encode> method will not
 generate characters outside the code range C<0..127> (which is ASCII). Any
 unicode characters outside that range will be escaped using either a
 single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
-as per RFC4627.
+as per RFC4627. The resulting encoded JSON text can be treated as a native
+unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
+or any other superset of ASCII.
 If C<$enable> is false, then the C<encode> method will not escape Unicode
-characters unless required by the JSON syntax. This results in a faster
+characters unless required by the JSON syntax or other flags. This results
-and more compact format.
+in a faster and more compact format.
+The main use for this flag is to produce JSON texts that can be
+transmitted over a 7-bit channel, as the encoded JSON texts will not
+contain any 8 bit characters.
   JSON::XS->new->ascii (1)->encode ([chr 0x10401])
   => ["\ud801\udc01"]
+=item $json = $json->latin1 ([$enable])
+If C<$enable> is true (or missing), then the C<encode> method will encode
+the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
+outside the code range C<0..255>. The resulting string can be treated as a
+latin1-encoded JSON text or a native unicode string. The C<decode> method
+will not be affected in any way by this flag, as C<decode> by default
+expects unicode, which is a strict superset of latin1.
+If C<$enable> is false, then the C<encode> method will not escape Unicode
+characters unless required by the JSON syntax or other flags.
+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
+transfering), a rare encoding for JSON. It is therefore most useful when
+you want to store data structures known to contain binary data efficiently
+in files or databases, not when talking to other JSON encoders/decoders.
+  JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
+  => ["\x{89}\\u0abc"]    # (perl syntax, U+abc escaped, U+89 not)
 =item $json = $json->utf8 ([$enable])
 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
 resulting in an invalid JSON text:
    JSON::XS->new->allow_nonref->encode ("Hello, World!")
    => "Hello, World!"
+=item $json = $json->allow_blessed ([$enable])
+If C<$enable> is true (or missing), then the C<encode> method will not
+barf when it encounters a blessed reference. Instead, the value of the
+B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
+disabled or no C<to_json> method found) or a representation of the
+object (C<convert_blessed> enabled and C<to_json> method found) is being
+encoded. Has no effect on C<decode>.
+If C<$enable> is false (the default), then C<encode> will throw an
+exception when it encounters a blessed object.
+=item $json = $json->convert_blessed ([$enable])
+If C<$enable> is true (or missing), then C<encode>, upon encountering a
+blessed object, will check for the availability of the C<TO_JSON> method
+on the object's class. If found, it will be called in scalar context
+and the resulting scalar will be encoded instead of the object. If no
+C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
+to do.
+The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
+returns other blessed objects, those will be handled in the same
+way. C<TO_JSON> must take care of not causing an endless recursion cycle
+(== crash) in this case. The name of C<TO_JSON> was chosen because other
+methods called by the Perl core (== not by the user of the object) are
+usually in upper case letters and to avoid collisions with the C<to_json>
+function.
+This setting does not yet influence C<decode> in any way, but in the
+future, global hooks might get installed that influence C<decode> and are
+enabled by this setting.
+If C<$enable> is false, then the C<allow_blessed> setting will decide what
+to do when a blessed object is found.
+=item $json = $json->filter_json_object ([$coderef])
+When C<$coderef> is specified, it will be called from C<decode> each
+time it decodes a JSON object. The only argument is a reference to the
+newly-created hash. If the code references returns a single scalar (which
+need not be a reference), this value (i.e. a copy of that scalar to avoid
+aliasing) is inserted into the deserialised data structure. If it returns
+an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
+original deserialised hash will be inserted. This setting can slow down
+decoding considerably.
+When C<$coderef> is omitted or undefined, C<decode> will not change the
+deserialised hash in any way. This is maximally fast.
+Example, convert all JSON objects into the integer 5:
+   my $js = JSON::XS->new->filter_json_object (sub { 5 });
+   # returns [5]
+   $js->decode ('[{}]')
+   # throw an exception because allow_nonref is not enabled:
+   $js->decode ('{"a":1, "b":2}');
+=item $json = $json->filter_json_single_key_object ([$coderef])
+Works like C<filter_json_object>, but is only called for JSON objects
+having only a single key.
+This C<$coderef> is called before the one specified via
+C<filter_json_object>, if any. If it returns something, that will be
+inserted into the data structure. If it returns nothing, the callback
+from C<filter_json_object> will be called next. If you want to force
+insertion of single-key objects even in the presence of a mutating
+C<filter_json_object> callback, simply return the passed hash.
+As this callback gets called less often then the C<filter_json_object>
+one, decoding speed will not usually suffer as much. Therefore, single-key
+objects make excellent targets to serialise Perl objects into, especially
+as single-key JSON objects are as close to the type-tagged value concept
+as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
+support this in any way, so you need to make sure your data never looks
+like a serialised Perl hash.
+Typical names for the single object key are C<__class_whatever__>, or
+C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
+things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
+with real hashes.
+Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
+into the corresponding C<< $WIDGET{<id>} >> object:
+   # return whatever is in $WIDGET{5}:
+   JSON::XS
+      ->new
+      ->filter_json_single_key_object (sub {
+         exists $_[0]{__widget__}
+            ? $WIDGET{ $_[0]{__widget__} }
+            : ()
+         })
+      ->decode ('{"__widget__": 5')
+   # this can be used with a TO_JSON method in some "widget" class
+   # for serialisation to json:
+   sub WidgetBase::TO_JSON {
+      my ($self) = @_;
+      unless ($self->{id}) {
+         $self->{id} = ..get..some..id..;
+         $WIDGET{$self->{id}} = $self;
+      }
+      { __widget__ => $self->{id} }
+   }
 =item $json = $json->shrink ([$enable])
 Perl usually over-allocates memory a bit when allocating space for
-strings.  This flag optionally resizes strings generated by either
+strings. This flag optionally resizes strings generated by either
 C<encode> or C<decode> to their minimum size possible. This can save
 memory when your JSON texts are either very very long or you have many
 short strings. It will also try to downgrade any strings to octet-form
 if possible: perl stores strings internally either in an encoding called
 UTF-X or in octet-form. The latter cannot store everything but uses less
-space in general.
+space in general (and some buggy Perl or C code might even rely on that
+internal representation being used).
+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 C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,
+If C<$enable> is true (or missing), the string returned by C<encode> will
-while all strings generated by C<decode> will also be shrunk-to-fit.
+be shrunk-to-fit, while all strings generated by C<decode> will also be
+shrunk-to-fit.
 If C<$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.
 =item $json = $json->max_depth ([$maximum_nesting_depth])
-Sets the maximum nesting level (default C<8192>) accepted while encoding
+Sets the maximum nesting level (default C<512>) accepted while encoding
 or decoding. If the JSON text or Perl data structure has an equal or
 higher nesting level then this limit, 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
 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.
-The argument to C<max_depth> will be rounded up to the next nearest power
+The argument to C<max_depth> will be rounded up to the next highest power
-of two.
+of two. If no argument is given, the highest possible setting will be
+used, which is rarely useful.
+See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
+=item $json = $json->max_size ([$maximum_string_size])
+Set the maximum length a JSON text may have (in bytes) where decoding is
+being attempted. The default is C<0>, meaning no limit. When C<decode>
+is called on a string longer then this number of characters it will not
+attempt to decode the string but throw an exception. This setting has no
+effect on C<encode> (yet).
+The argument to C<max_size> will be rounded up to the next B<highest>
+power of two (so may be more than requested). If no argument is given, the
+limit check will be deactivated (same as when C<0> is specified).
 See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
 =item $json_text = $json->encode ($perl_scalar)
 JSON numbers and strings become simple Perl scalars. JSON arrays become
 Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
 C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
+=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
+This works like the C<decode> method, but instead of raising an exception
+when there is trailing garbage after the first JSON object, it will
+silently stop parsing there and return the number of characters consumed
+so far.
+This is useful if your JSON texts are not delimited by an outer protocol
+(which is not the brightest thing to do in the first place) and you need
+to know where the JSON text ends.
+   JSON::XS->new->decode_prefix ("[1] the tail")
+   => ([], 3)
 =back
 =head1 MAPPING
 (what you put in comes out as something equivalent).
 For the more enlightened: note that in the following descriptions,
 lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
 refers to the abstract Perl language itself.
 =head2 JSON -> PERL
 =over 4
 conversion details, but an integer may take slightly less memory and might
 represent more values exactly than (floating point) numbers.
 =item true, false
-These JSON atoms become C<0>, C<1>, respectively. Information is lost in
+These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
-this process. Future versions might represent those values differently,
+respectively. They are overloaded to act almost exactly like the numbers
-but they will be guarenteed to act like these integers would normally in
+C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
-Perl.
+the C<JSON::XS::is_bool> function.
 =item null
 A JSON null atom becomes C<undef> in Perl.
 =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
 =over 4
 =item hash references
 Perl hash references become JSON objects. As there is no inherent ordering
-in hash keys, they will usually be encoded in a pseudo-random order that
+in hash keys (or JSON objects), they will usually be encoded in a
-can change between runs of the same program but stays generally the same
+pseudo-random order that can change between runs of the same program but
-within a single run of a program. JSON::XS can optionally sort the hash
+stays generally the same within a single run of a program. JSON::XS can
-keys (determined by the I<canonical> flag), so the same datastructure
+optionally sort the hash keys (determined by the I<canonical> flag), so
-will serialise to the same JSON text (given same settings and version of
+the same datastructure will serialise to the same JSON text (given same
-JSON::XS), but this incurs a runtime overhead.
+settings and version of JSON::XS), but this incurs a runtime overhead
+and is only rarely useful, e.g. when you want to compare some JSON text
+against another for equality.
 =item array references
 Perl array references become JSON arrays.
+=item other references
+Other unblessed references are generally not allowed and will cause an
+exception to be thrown, except for references to the integers C<0> and
+C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
+also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
+   to_json [\0,JSON::XS::true]      # yields [false,true]
+=item JSON::XS::true, JSON::XS::false
+These special values become JSON true and JSON false values,
+respectively. You cna alos use C<\1> and C<\0> directly if you want.
 =item blessed objects
 Blessed objects are not allowed. JSON::XS currently tries to encode their
 underlying representation (hash- or arrayref), but this behaviour might
    $x += 0;     # numify it, ensuring it will be dumped as a number
    $x *= 1;     # same thing, the choise is yours.
 You can not currently output JSON booleans or force the type in other,
 less obscure, ways. Tell me if you need this capability.
-=item circular data structures
-Those will be encoded until memory or stackspace runs out.
 =back
 =head1 COMPARISON
 Does not check input for validity.
 =back
+=head2 JSON and YAML
+You often hear that JSON is a subset (or a close subset) of YAML. This is,
+however, a mass hysteria and very far from the truth. In general, there is
+no way to configure JSON::XS to output a data structure as valid YAML.
+If you really must use JSON::XS to generate YAML, you should use this
+algorithm (subject to change in future versions):
+   my $to_yaml = 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. Please note that YAML has hardcoded limits on (simple) object key
+lengths that JSON doesn't have, so you should make sure that your hash
+keys are noticably shorter than the 1024 characters YAML allows.
+There might be other incompatibilities that I am not aware of. In 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.
 =head2 SPEED
 It seems that JSON::XS is surprisingly fast, as shown in the following
 tables. They have been generated with the help of the C<eg/bench> program
 in the JSON::XS distribution, to make it easy to compare on your own
 system.
-First comes a comparison between various modules using a very short JSON
+First comes a comparison between various modules using a very short
-string:
+single-line JSON string:
-   {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}
+   {"method": "handleMessage", "params": ["user1", "we were just talking"], \
+   "id": null, "array":[1,11,234,-5,1e5,1e7, true,  false]}
-It shows the number of encodes/decodes per second (JSON::XS uses the
+It shows the number of encodes/decodes per second (JSON::XS uses
-functional interface, while JSON::XS/2 uses the OO interface with
+the functional interface, while JSON::XS/2 uses the OO interface
-pretty-printing and hashkey sorting enabled). Higher is better:
+with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
+shrink). Higher is better:
+   Storable   |  15779.925 |  14169.946 |
+   -----------+------------+------------+
    module     |     encode |     decode |
    -----------|------------|------------|
-   JSON       |  11488.516 |   7823.035 |
+   JSON       |   4990.842 |   4088.813 |
-   JSON::DWIW |  94708.054 | 129094.260 |
+   JSON::DWIW |  51653.990 |  71575.154 |
-   JSON::PC   |  63884.157 | 128528.212 |
+   JSON::PC   |  65948.176 |  74631.744 |
-   JSON::Syck |  34898.677 |  42096.911 |
+   JSON::PP   |   8931.652 |   3817.168 |
-   JSON::XS   | 654027.064 | 396423.669 |
+   JSON::Syck |  24877.248 |  27776.848 |
-   JSON::XS/2 | 371564.190 | 371725.613 |
+   JSON::XS   | 388361.481 | 227951.304 |
+   JSON::XS/2 | 227951.304 | 218453.333 |
+   JSON::XS/3 | 338250.323 | 218453.333 |
+   Storable   |  16500.016 | 135300.129 |
    -----------+------------+------------+
-That is, JSON::XS is more than six times faster than JSON::DWIW on
+That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
-encoding, more than three times faster on decoding, and about thirty times
+about three times faster on decoding, and over fourty times faster
-faster than JSON, even with pretty-printing and key sorting.
+than JSON, even with pretty-printing and key sorting. 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://nanoref.com/yahooapis/mgPdGg):
    module     |     encode |     decode |
    -----------|------------|------------|
-   JSON       |    273.023 |     44.674 |
+   JSON       |     55.260 |     34.971 |
-   JSON::DWIW |   1089.383 |   1145.704 |
+   JSON::DWIW |    825.228 |   1082.513 |
-   JSON::PC   |   3097.419 |   2393.921 |
+   JSON::PC   |   3571.444 |   2394.829 |
-   JSON::Syck |    514.060 |    843.053 |
+   JSON::PP   |    210.987 |     32.574 |
-   JSON::XS   |   6479.668 |   3636.364 |
+   JSON::Syck |    552.551 |    787.544 |
-   JSON::XS/2 |   3774.221 |   3599.124 |
+   JSON::XS   |   5780.463 |   4854.519 |
+   JSON::XS/2 |   3869.998 |   4798.975 |
+   JSON::XS/3 |   5862.880 |   4798.975 |
+   Storable   |   4445.002 |   5235.027 |
    -----------+------------+------------+
-Again, JSON::XS leads by far.
+Again, JSON::XS leads by far (except for Storable which non-surprisingly
+decodes 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
 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, thats 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.
+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, 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
+machine with 8MB of stack size I can decode around 180k nested arrays but
-but only 14k nested JSON objects. If that is exceeded, the program
+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
-crashes. Thats why the default nesting limit is set to 8192. If your
+conservative, the default nesting limit is set to 512. If your process
-process has a smaller stack, you should adjust this setting accordingly
+has a smaller stack, you should adjust this setting accordingly with the
-with the C<max_depth> method.
+C<max_depth> method.
 And last but least, something else could bomb you that I forgot to think
-of. In that case, you get to keep the pieces. I am alway sopen for hints,
+of. In that case, you get to keep the pieces. I am always open for hints,
 though...
+If you are using JSON::XS to return packets to consumption
+by javascript scripts in a browser you should have a look at
+L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
+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 doing security
+right).
 =head1 BUGS
 While the goal of this module is to be correct, that unfortunately does
 still relatively early in its development. If you keep reporting bugs they
 will be fixed swiftly, though.
 =cut
+our $true  = do { bless \(my $dummy = "1"), "JSON::XS::Boolean" };
+our $false = do { bless \(my $dummy = "0"), "JSON::XS::Boolean" };
+sub true()  { $true  }
+sub false() { $false }
+sub is_bool($) {
+   UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
+#      or UNIVERSAL::isa $_[0], "JSON::Literal"
+}
+XSLoader::load "JSON::XS", $VERSION;
+package JSON::XS::Boolean;
+use overload
+   "0+"     => sub { ${$_[0]} },
+   "++"     => sub { $_[0] = ${$_[0]} + 1 },
+   "--"     => sub { $_[0] = ${$_[0]} - 1 },
+   fallback => 1;
 1;
 =head1 AUTHOR
  Marc Lehmann <schmorp@schmorp.de>

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Comparing JSON-XS/XS.pm (file contents): Revision 1.23 by root, Sun Mar 25 21:19:13 2007 UTC vs. Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.23 by root, Sun Mar 25 21:19:13 2007 UTC vs.
Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC