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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.100 by root, Sun Mar 30 09:27:16 2008 UTC vs.
Revision 1.121 by root, Mon Jul 13 22:13:17 2009 UTC

 =head1 NAME
+JSON::XS - JSON serialising/deserialising, done correctly and fast
 =encoding utf-8
-JSON::XS - JSON serialising/deserialising, done correctly and fast
 JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
            (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
 =head1 SYNOPSIS
 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
-overriden) with no overhead due to emulation (by inheritign constructor
+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.
 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
 This module knows how to handle Unicode, documents how and when it does
 so, and even documents what "correct" means.
 =item * round-trip integrity
-When you serialise a perl data structure using only datatypes supported
+When you serialise a perl data structure using only data types supported
 by JSON, the deserialised data structure is identical on the Perl level.
 (e.g. the string "2.0" doesn't suddenly become "2" just because it looks
 like a number). There minor I<are> exceptions to this, read the MAPPING
 section below to learn about those.
 Compared to other JSON modules and other serialisers such as Storable,
 this module usually compares favourably in terms of speed, too.
 =item * simple to use
-This module has both a simple functional interface as well as an objetc
+This module has both a simple functional interface as well as an object
 oriented interface interface.
 =item * reasonably versatile output formats
 You can choose between the most compact guaranteed-single-line format
-possible (nice for simple line-based protocols), a pure-ascii format
+possible (nice for simple line-based protocols), a pure-ASCII format
 (for when your transport is not 8-bit clean, still supports the whole
 Unicode range), or a pretty-printed format (for when you want to read that
 stuff). Or you can combine those features in whatever way you like.
 =back
 =cut
 package JSON::XS;
-use strict;
+use common::sense;
-our $VERSION = '2.2';
+our $VERSION = '2.24';
 our @ISA = qw(Exporter);
 our @EXPORT = qw(encode_json decode_json to_json from_json);
 sub to_json($) {
 This function call is functionally identical to:
    $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
-except being faster.
+Except being faster.
 =item $perl_scalar = decode_json $json_text
 The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
 to parse that as an UTF-8 encoded JSON text, returning the resulting
 This function call is functionally identical to:
    $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
-except being faster.
+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
 If you didn't know about that flag, just the better, pretend it doesn't
 exist.
 =item 4. A "Unicode String" is simply a string where each character can be
-validly interpreted as a Unicode codepoint.
+validly interpreted as a Unicode code point.
 If you have UTF-8 encoded data, it is no longer a Unicode string, but a
 Unicode string encoded in UTF-8, giving you a binary string.
 =item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
 =item $json = $json->max_depth ([$maximum_nesting_depth])
 =item $max_depth = $json->get_max_depth
 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
+or decoding. If a higher nesting level is detected in JSON text or a Perl
-higher nesting level then this limit, then the encoder and decoder will
+data structure, then the encoder and decoder will stop and croak at that
-stop and croak at that point.
+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 C<{> or C<[>
 characters without their matching closing parenthesis crossed to reach a
 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 highest power
-of two. If no argument is given, the highest possible setting will be
+If no argument is given, the highest possible setting will be used, which
-used, which is rarely useful.
+is rarely useful.
+Note that nesting is implemented by recursion in C. The default value has
+been chosen to be as large as typical operating systems allow without
+crashing.
 See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
 =item $json = $json->max_size ([$maximum_string_size])
 =item $max_size = $json->get_max_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
+is called on a string that is longer then this many bytes, 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>
+If no argument is given, the limit check will be deactivated (same as when
-power of two (so may be more than requested). If no argument is given, the
+C<0> is specified).
-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)
 =back
 =head1 INCREMENTAL PARSING
-[This section and the API it details is still EXPERIMENTAL]
 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 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
 =head2 LIMITATIONS
 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.
-   encode_json [\0,JSON::XS::true]      # yields [false,true]
+   encode_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 can also use C<\1> and C<\0> directly if you want.
 when your channel for JSON transfer is not 8-bit clean or the encoding
 might be mangled in between (e.g. in mail), and works because ASCII is a
 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
 =head1 BUGS
 While the goal of this module is to be correct, that unfortunately does
-not mean it's bug-free, only that I think its design is bug-free. It is
+not mean it's bug-free, only that I think its design is bug-free. If you
-still relatively early in its development. If you keep reporting bugs they
+keep reporting bugs they will be fixed swiftly, though.
-will be fixed swiftly, though.
 Please refrain from using rt.cpan.org or any other bug reporting
 service. I put the contact address into my modules for a reason.
 =cut

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Comparing JSON-XS/XS.pm (file contents): Revision 1.100 by root, Sun Mar 30 09:27:16 2008 UTC vs. Revision 1.121 by root, Mon Jul 13 22:13:17 2009 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.100 by root, Sun Mar 30 09:27:16 2008 UTC vs.
Revision 1.121 by root, Mon Jul 13 22:13:17 2009 UTC