[ViewVC] Diff of: cvs/JSON-XS/README

Comparing JSON-XS/README (file contents):
Revision 1.8 by root, Sun Mar 25 22:11:06 2007 UTC vs.
Revision 1.14 by root, Sat Jun 23 23:50:03 2007 UTC

            $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
         except being faster.
+    $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 1 and 0,
+        respectively and are used to represent JSON "true" and "false"
+        values in Perl.
+        See MAPPING, below, for more information on how JSON values are
+        mapped to Perl.
 OBJECT-ORIENTED INTERFACE
     The object oriented interface lets you configure your own encoding or
     decoding style, within the limits of supported formats.
     $json = new JSON::XS
     $json = $json->ascii ([$enable])
         If $enable is true (or missing), then the "encode" method will not
         generate characters outside the code range 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.
+        escape sequence, 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 $enable is false, then the "encode" method will not escape
-        Unicode characters unless required by the JSON syntax. This results
+        Unicode characters unless required by the JSON syntax or other
-        in a faster and more compact format.
+        flags. This results 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"]
+    $json = $json->latin1 ([$enable])
+        If $enable is true (or missing), then the "encode" method will
+        encode the resulting JSON text as latin1 (or iso-8859-1), escaping
+        any characters outside the code range 0..255. The resulting string
+        can be treated as a latin1-encoded JSON text or a native unicode
+        string. The "decode" method will not be affected in any way by this
+        flag, as "decode" by default expects unicode, which is a strict
+        superset of latin1.
+        If $enable is false, then the "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)
     $json = $json->utf8 ([$enable])
         If $enable is true (or missing), then the "encode" method will
         encode the JSON result into UTF-8, as required by many protocols,
         while the "decode" method expects to be handled an UTF-8-encoded
         "encode" or "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.
+        everything but uses less 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 $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.
         converting strings that look like integers or floats into integers
         or floats internally (there is no difference on the Perl level),
         saving space.
     $json = $json->max_depth ([$maximum_nesting_depth])
-        Sets the maximum nesting level (default 8192) accepted while
+        Sets the maximum nesting level (default 512) accepted while encoding
-        encoding or decoding. If the JSON text or Perl data structure has an
+        or decoding. If the JSON text or Perl data structure has an equal or
-        equal or higher nesting level then this limit, then the encoder and
+        higher nesting level then this limit, then the encoder and decoder
-        decoder will stop and croak at that point.
+        will stop and croak at that point.
         Nesting level is defined by number of hash- or arrayrefs that the
         encoder needs to traverse to reach a given point or the number of
         "{" or "[" characters without their matching closing parenthesis
         crossed to reach a given character in a string.
         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".
+    ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
+        This works like the "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)
 MAPPING
     This section describes how JSON::XS maps Perl values to JSON values and
     vice versa. These mappings are designed to "do the right thing" in most
     circumstances automatically, preserving round-tripping characteristics
     (what you put in comes out as something equivalent).
         all the conversion details, but an integer may take slightly less
         memory and might represent more values exactly than (floating point)
         numbers.
     true, false
-        These JSON atoms become 0, 1, respectively. Information is lost in
+        These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
-        this process. Future versions might represent those values
+        respectively. They are overloaded to act almost exactly like the
-        differently, but they will be guarenteed to act like these integers
+        numbers 1 and 0. You can check wether a scalar is a JSON boolean by
-        would normally in Perl.
+        using the "JSON::XS::is_bool" function.
     null
         A JSON null atom becomes "undef" in Perl.
   PERL -> JSON
     truly typeless language, so we can only guess which JSON type is meant
     by a Perl value.
     hash references
         Perl hash references become JSON objects. As there is no inherent
-        ordering in hash keys, they will usually be encoded in a
+        ordering in hash keys (or JSON objects), they will usually be
-        pseudo-random order that can change between runs of the same program
+        encoded in a pseudo-random order that can change between runs of the
-        but stays generally the same within a single run of a program.
+        same program but stays generally the same within a single run of a
-        JSON::XS can optionally sort the hash keys (determined by the
+        program. JSON::XS can optionally sort the hash keys (determined by
-        *canonical* flag), so the same datastructure will serialise to the
+        the *canonical* flag), so the same datastructure will serialise to
-        same JSON text (given same settings and version of JSON::XS), but
+        the same JSON text (given same settings and version of JSON::XS),
-        this incurs a runtime overhead.
+        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.
     array references
         Perl array references become JSON arrays.
+    other references
+        Other unblessed references are generally not allowed and will cause
+        an exception to be thrown, except for references to the integers 0
+        and 1, which get turned into "false" and "true" atoms in JSON. You
+        can also use "JSON::XS::false" and "JSON::XS::true" to improve
+        readability.
+           to_json [\0,JSON::XS::true]      # yields [false,true]
+    JSON::XS::true, JSON::XS::false
+        These special values become JSON true and JSON false values,
+        respectively. You cna alos use "\1" and "\0" directly if you want.
     blessed objects
         Blessed objects are not allowed. JSON::XS currently tries to encode
         their underlying representation (hash- or arrayref), but this
         behaviour might change in future versions.
            $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.
-    circular data structures
-        Those will be encoded until memory or stackspace runs out.
 COMPARISON
     As already mentioned, this module was created because none of the
     existing JSON modules could be made to work correctly. First I will
     describe the problems (or pleasures) I encountered with various existing
         Does not generate valid JSON texts (key strings are often unquoted,
         empty keys result in nothing being output)
         Does not check input for validity.
+  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.
   SPEED
     It seems that JSON::XS is surprisingly fast, as shown in the following
     tables. They have been generated with the help of the "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
     functional interface, while JSON::XS/2 uses the OO interface with
-    pretty-printing and hashkey sorting enabled). Higher is better:
+    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 |  40721.398 |  77101.176 |
-       JSON::PC   |  63884.157 | 128528.212 |
+       JSON::PC   |  65948.176 |  78251.940 |
-       JSON::Syck |  34898.677 |  42096.911 |
+       JSON::Syck |  22844.793 |  26479.192 |
-       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   |  15779.925 |  14169.946 |
        -----------+------------+------------+
-    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, more than three times faster on decoding, and about thirty
+    encoding, about three times faster on decoding, and over fourty times
-    times faster than JSON, even with pretty-printing and key sorting.
+    faster 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 |    843.343 |   1049.731 |
-       JSON::PC   |   3097.419 |   2393.921 |
+       JSON::PC   |   3602.116 |   2307.352 |
-       JSON::Syck |    514.060 |    843.053 |
+       JSON::Syck |    505.107 |    787.899 |
-       JSON::XS   |   6479.668 |   3636.364 |
+       JSON::XS   |   5747.196 |   3690.220 |
-       JSON::XS/2 |   3774.221 |   3599.124 |
+       JSON::XS/2 |   3968.121 |   3676.634 |
+       JSON::XS/3 |   6105.246 |   3662.508 |
+       Storable   |   4417.337 |   5285.161 |
        -----------+------------+------------+
-    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
     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
-    but only 14k nested JSON objects. If that is exceeded, the program
+    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.
-    crashes. Thats why the default nesting limit is set to 8192. If your
+    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.
     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
+    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
+    <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).
 BUGS
     While the goal of this module is to be correct, that unfortunately does
     not mean its bug-free, only that I think its design is bug-free. It is
     still relatively early in its development. If you keep reporting bugs

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Comparing JSON-XS/README (file contents): Revision 1.8 by root, Sun Mar 25 22:11:06 2007 UTC vs. Revision 1.14 by root, Sat Jun 23 23:50:03 2007 UTC

Diff Legend

Comparing JSON-XS/README (file contents):
Revision 1.8 by root, Sun Mar 25 22:11:06 2007 UTC vs.
Revision 1.14 by root, Sat Jun 23 23:50:03 2007 UTC