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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.106 by root, Tue May 27 05:31:39 2008 UTC vs.
Revision 1.124 by root, Sun Aug 9 16:01:39 2009 UTC

 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 COMPARISON, below, for a comparison to some other JSON modules.
 See MAPPING, below, on how JSON::XS maps perl values to JSON values and
 vice versa.
 =head2 FEATURES
 =cut
 package JSON::XS;
-use strict;
+use common::sense;
-our $VERSION = '2.2';
+our $VERSION = '2.25';
 our @ISA = qw(Exporter);
 our @EXPORT = qw(encode_json decode_json to_json from_json);
 sub to_json($) {
 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 setting has currently no effect on tied hashes.
 =item $json = $json->allow_nonref ([$enable])
 =item $enabled = $json->get_allow_nonref
 In some cases, there is the need for incremental parsing of JSON
 texts. While this module always has to keep both JSON text and resulting
 Perl data structure in memory at one time, it does allow you to parse a
 JSON stream incrementally. It does so by accumulating text until it has
 a full JSON object, which it then can decode. This process is similar to
-using C<decode_prefix> to see if a full JSON object is available, but is
+using C<decode_prefix> to see if a full JSON object is available, but
-much more efficient (JSON::XS will only attempt to parse the JSON text
+is much more efficient (and can be implemented with a minimum of method
+calls).
+JSON::XS will only attempt to parse the JSON text once it is sure it
-once it is sure it has enough text to get a decisive result, using a very
+has enough text to get a decisive result, using a very simple but
-simple but truly incremental parser).
+truly incremental parser. This means that it sometimes won't stop as
+early as the full parser, for example, it doesn't detect parenthese
+mismatches. 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. C<max_size>) to ensure the parser will stop
+parsing in the presence if syntax errors.
-The following two methods deal with this.
+The following methods implement this incremental parser.
 =over 4
 =item [void, scalar or list context] = $json->incr_parse ([$string])
 JSON object or b) parsing multiple JSON objects separated by non-JSON text
 (such as commas).
 =item $json->incr_skip
-This will reset the state of the incremental parser and will remove the
+This will reset the state of the incremental parser and will remove
-parsed text from the input buffer. This is useful after C<incr_parse>
+the parsed text from the input buffer so far. This is useful after
-died, in which case the input buffer and incremental parser state is left
+C<incr_parse> died, in which case the input buffer and incremental parser
-unchanged, to skip the text parsed so far and to reset the parse state.
+state is left unchanged, to skip the text parsed so far and to reset the
+parse state.
+The difference to C<incr_reset> is that only text until the parse error
+occured is removed.
 =item $json->incr_reset
 This completely resets the incremental parser, that is, after this call,
 it will be as if the parser had never parsed anything.
-This is useful if you want ot repeatedly parse JSON objects and want to
+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.
 =back
 proper subset of most 8-bit and multibyte encodings in use in the world.
 =back
+=head2 JSON and ECMAscript
+JSON syntax is based on how literals are represented in javascript (the
+not-standardised predecessor of ECMAscript) which is presumably why it is
+called "JavaScript Object Notation".
+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 C<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 C<eval>:
+   use 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 C<eval> (see for example Douglas Crockford's
+F<json2.js> parser).
+If this is not an option, you can, as a stop-gap measure, simply encode to
+ASCII-only JSON:
+   use JSON::XS;
+   print 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 = 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 I<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 C<eval> naively simply I<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
+C<__proto__> property name for it's 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 C<__proto__> is not valid outside of strings, so every
+occurence of C<"__proto__"\s*:> must be a string used as property name.
+If you know of other incompatibilities, please let me know.
 =head2 JSON and YAML
 You often hear that JSON is a subset of YAML. This is, however, a mass
 hysteria(*) and very far from the truth (as of the time of this writing),
 so let me state it clearly: I<in general, there is no way to configure
    my $yaml = $to_yaml->encode ($ref) . "\n";
 This will I<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 and also has different and incompatible
-unicode handling, so you should make sure that your hash keys are
+unicode character escape syntax, so you should make sure that your hash
-noticeably shorter than the 1024 "stream characters" YAML allows and that
+keys are noticeably shorter than the 1024 "stream characters" YAML allows
-you do not have characters with codepoint values outside the Unicode BMP
+and that you do not have characters with codepoint values outside the
-(basic multilingual page). YAML also does not allow C<\/> sequences in
+Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
-strings (which JSON::XS does not I<currently> generate, but other JSON
+sequences in strings (which JSON::XS does not I<currently> generate, but
-generators might).
+other JSON generators might).
 There might be other incompatibilities that I am not aware of (or the YAML
 specification has been changed yet again - it does so quite often). 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
 proponents, I would kindly suggest reading the JSON spec (which is not
 that difficult or long) and finally make YAML compatible to it, and
 educating users about the changes, instead of spreading lies about the
 real compatibility for many I<years> and trying to silence people who
 point out that it isn't true.
+Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON, even
+though the incompatibilities have been documented (and are known to
+Brian) for many years and the spec makes explicit claims that YAML is a
+superset of JSON. It would be so easy to fix, but apparently, bullying and
+corrupting userdata is so much easier.
 =back
 =head2 SPEED

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Comparing JSON-XS/XS.pm (file contents): Revision 1.106 by root, Tue May 27 05:31:39 2008 UTC vs. Revision 1.124 by root, Sun Aug 9 16:01:39 2009 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.106 by root, Tue May 27 05:31:39 2008 UTC vs.
Revision 1.124 by root, Sun Aug 9 16:01:39 2009 UTC