[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 1.39 by root, Mon Jun 11 02:58:10 2007 UTC

 package JSON::XS;
 use strict;
 BEGIN {
-   our $VERSION = '0.8';
+   our $VERSION = '1.23';
    our @ISA = qw(Exporter);
    our @EXPORT = qw(to_json from_json objToJson jsonToObj);
    require Exporter;
 If C<$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
    => "Hello, World!"
 =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
 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
 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
 a Perl value.
 =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 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 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 object key lengths
+that JSON doesn't have, so you should make sure that your hash keys are
+noticably shorter than 1024 characters.
+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.
 =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:
    module     |     encode |     decode |
    -----------|------------|------------|
-   JSON       |  11488.516 |   7823.035 |
+   JSON       |   7645.468 |   4208.613 |
-   JSON::DWIW |  94708.054 | 129094.260 |
+   JSON::DWIW |  68534.379 |  79437.576 |
-   JSON::PC   |  63884.157 | 128528.212 |
+   JSON::PC   |  65948.176 |  78251.940 |
-   JSON::Syck |  34898.677 |  42096.911 |
+   JSON::Syck |  23379.621 |  28416.694 |
-   JSON::XS   | 654027.064 | 396423.669 |
+   JSON::XS   | 388361.481 | 199728.762 |
-   JSON::XS/2 | 371564.190 | 371725.613 |
+   JSON::XS/2 | 218453.333 | 192399.266 |
+   JSON::XS/3 | 338250.323 | 192399.266 |
+   Storable   |  15732.573 |  28571.553 |
    -----------+------------+------------+
-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       |    254.685 |     37.665 |
-   JSON::DWIW |   1089.383 |   1145.704 |
+   JSON::DWIW |   1014.244 |   1087.678 |
-   JSON::PC   |   3097.419 |   2393.921 |
+   JSON::PC   |   3602.116 |   2307.352 |
-   JSON::Syck |    514.060 |    843.053 |
+   JSON::Syck |    558.035 |    776.263 |
-   JSON::XS   |   6479.668 |   3636.364 |
+   JSON::XS   |   5747.196 |   3543.684 |
-   JSON::XS/2 |   3774.221 |   3599.124 |
+   JSON::XS/2 |   3968.121 |   3589.170 |
+   JSON::XS/3 |   6105.246 |   3561.134 |
+   Storable   |   4456.337 |   5320.020 |
    -----------+------------+------------+
 Again, JSON::XS leads by far.
 On large strings containing lots of high unicode characters, some modules
 usually a good indication of the size of the resources required to decode
 it into a Perl structure.
 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...
 =head1 BUGS
 still relatively early in its development. If you keep reporting bugs they
 will be fixed swiftly, though.
 =cut
+sub true()  { \1 }
+sub false() { \0 }
 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 1.39 by root, Mon Jun 11 02:58:10 2007 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.23 by root, Sun Mar 25 21:19:13 2007 UTC vs.
Revision 1.39 by root, Mon Jun 11 02:58:10 2007 UTC