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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.45 by root, Mon Jun 25 04:16:46 2007 UTC vs.
Revision 1.84 by root, Wed Mar 19 02:52:15 2008 UTC

+=encoding utf-8
 =head1 NAME
 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
  use JSON::XS;
  # exported functions, they croak on error
  # and expect/generate UTF-8
- $utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
+ $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
- $perl_hash_or_arrayref  = from_json $utf8_encoded_json_text;
+ $perl_hash_or_arrayref  = decode_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);
  $perl_scalar = $coder->decode ($unicode_json_text);
+ # Note that JSON version 2.0 and above will automatically use JSON::XS
+ # if available, at virtually no speed overhead either, so you should
+ # be able to just:
+ use JSON;
+ # and do the same things, except that you have a pure-perl fallback now.
 =head1 DESCRIPTION
 This module converts Perl data structures to JSON and vice versa. Its
 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
+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.
 As this is the n-th-something JSON module on CPAN, what was the reason
 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
 =head2 FEATURES
 =over 4
-=item * correct unicode handling
+=item * correct Unicode handling
-This module knows how to handle Unicode, and even documents how and when
+This module knows how to handle Unicode, documents how and when it does
-it does so.
+so, and even documents what "correct" means.
 =item * round-trip integrity
 When you serialise a perl data structure using only datatypes 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).
+like a number). There minor I<are> exceptions to this, read the MAPPING
+section below to learn about those.
 =item * strict checking of JSON correctness
 There is no guessing, no generating of illegal JSON texts by default,
 and only JSON is accepted as input by default (the latter is a security
 feature).
 =item * fast
-Compared to other JSON modules, this module compares favourably in terms
+Compared to other JSON modules and other serialisers such as Storable,
-of speed, too.
+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 OO
+This module has both a simple functional interface as well as an objetc
-interface.
+oriented interface interface.
 =item * reasonably versatile output formats
-You can choose between the most compact guarenteed single-line format
+You can choose between the most compact guaranteed-single-line 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
+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;
-our $VERSION = '1.4';
+our $VERSION = '2.01';
 our @ISA = qw(Exporter);
-our @EXPORT = qw(to_json from_json objToJson jsonToObj);
+our @EXPORT = qw(encode_json decode_json to_json from_json);
+sub to_json($) {
+   require Carp;
+   Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
+}
+sub from_json($) {
+   require Carp;
+   Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
+}
 use Exporter;
 use XSLoader;
 =head1 FUNCTIONAL INTERFACE
-The following convinience methods are provided by this module. They are
+The following convenience methods are provided by this module. They are
 exported by default:
 =over 4
-=item $json_text = to_json $perl_scalar
+=item $json_text = encode_json $perl_scalar
-Converts the given Perl data structure (a simple scalar or a reference to
+Converts the given Perl data structure to a UTF-8 encoded, binary string
-a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
+(that is, the string contains octets only). Croaks on error.
-octets only). Croaks on error.
 This function call is functionally identical to:
    $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
 except being faster.
-=item $perl_scalar = from_json $json_text
+=item $perl_scalar = decode_json $json_text
-The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
+The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
-parse that as an UTF-8 encoded JSON text, returning the resulting simple
+to parse that as an UTF-8 encoded JSON text, returning the resulting
-scalar or reference. Croaks on error.
+reference. Croaks on error.
 This function call is functionally identical to:
    $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
 Perl.
 =back
+=head1 A FEW NOTES ON UNICODE AND PERL
+Since this often leads to confusion, here are a few very clear words on
+how Unicode works in Perl, modulo bugs.
+=over 4
+=item 1. Perl strings can store characters with ordinal values > 255.
+This enables you to store Unicode characters as single characters in a
+Perl string - very natural.
+=item 2. Perl does I<not> associate an encoding with your strings.
+... until you force it to, e.g. when matching it against a regex, or
+printing the scalar to a file, in which case Perl either interprets your
+string as locale-encoded text, octets/binary, or as Unicode, depending
+on various settings. In no case is an encoding stored together with your
+data, it is I<use> that decides encoding, not any magical meta data.
+=item 3. The internal utf-8 flag has no meaning with regards to the
+encoding of your string.
+Just ignore that flag unless you debug a Perl bug, a module written in
+XS or want to dive into the internals of perl. Otherwise it will only
+confuse you, as, despite the name, it says nothing about how your string
+is encoded. You can have Unicode strings with that flag set, with that
+flag clear, and you can have binary data with that flag set and that flag
+clear. Other possibilities exist, too.
+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.
+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.
+It's a fact. Learn to live with it.
+=back
+I hope this helps :)
 =head1 OBJECT-ORIENTED INTERFACE
 The object oriented interface lets you configure your own encoding or
 decoding style, within the limits of supported formats.
    my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
    => {"a": [1, 2]}
 =item $json = $json->ascii ([$enable])
+=item $enabled = $json->get_ascii
 If C<$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
+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. The resulting encoded JSON text can be treated as a native
-unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
+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 or other flags. This results
 in a faster and more compact format.
   JSON::XS->new->ascii (1)->encode ([chr 0x10401])
   => ["\ud801\udc01"]
 =item $json = $json->latin1 ([$enable])
+=item $enabled = $json->get_latin1
 If C<$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
+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.
+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
+transferring), 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])
+=item $enabled = $json->get_utf8
 If C<$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
 C<decode> method expects to be handled an UTF-8-encoded string.  Please
 note that UTF-8-encoded strings do not contain any characters outside the
 range C<0..255>, they are thus useful for bytewise/binary I/O. In future
 versions, enabling this option might enable autodetection of the UTF-16
 and UTF-32 encoding families, as described in RFC4627.
 If C<$enable> is false, then the C<encode> method will return the JSON
-string as a (non-encoded) unicode string, while C<decode> expects thus a
+string as a (non-encoded) Unicode string, while C<decode> expects thus a
-unicode string.  Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
+Unicode string.  Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
 to be done yourself, e.g. using the Encode module.
 Example, output UTF-16BE-encoded JSON:
   use Encode;
       ]
    }
 =item $json = $json->indent ([$enable])
+=item $enabled = $json->get_indent
 If C<$enable> is true (or missing), then the C<encode> method will use a multiline
 format as output, putting every array member or object/hash key-value pair
-into its own line, identing them properly.
+into its own line, indenting them properly.
 If C<$enable> is false, no newlines or indenting will be produced, and the
-resulting JSON text is guarenteed not to contain any C<newlines>.
+resulting JSON text is guaranteed not to contain any C<newlines>.
 This setting has no effect when decoding JSON texts.
 =item $json = $json->space_before ([$enable])
+=item $enabled = $json->get_space_before
 If C<$enable> is true (or missing), then the C<encode> method will add an extra
 optional space before the C<:> separating keys from values in JSON objects.
 If C<$enable> is false, then the C<encode> method will not add any extra
 Example, space_before enabled, space_after and indent disabled:
    {"key" :"value"}
 =item $json = $json->space_after ([$enable])
+=item $enabled = $json->get_space_after
 If C<$enable> is true (or missing), then the C<encode> method will add an extra
 optional space after the C<:> separating keys from values in JSON objects
 and extra whitespace after the C<,> separating key-value pairs and array
 members.
 Example, space_before and indent disabled, space_after enabled:
    {"key": "value"}
+=item $json = $json->relaxed ([$enable])
+=item $enabled = $json->get_relaxed
+If C<$enable> is true (or missing), then C<decode> will accept some
+extensions to normal JSON syntax (see below). C<encode> will not be
+affected in anyway. I<Be aware that this option makes you accept invalid
+JSON texts as if they were valid!>. I suggest only to use this option to
+parse application-specific files written by humans (configuration files,
+resource files etc.)
+If C<$enable> is false (the default), then C<decode> will only accept
+valid JSON texts.
+Currently accepted extensions are:
+=over 4
+=item * list items can have an end-comma
+JSON I<separates> array elements and key-value pairs with commas. This
+can be annoying if you write JSON texts manually and want to be able to
+quickly append elements, so this extension accepts comma at the end of
+such items not just between them:
+   [
+      1,
+      2, <- this comma not normally allowed
+   ]
+   {
+      "k1": "v1",
+      "k2": "v2", <- this comma not normally allowed
+   }
+=item * shell-style '#'-comments
+Whenever JSON allows whitespace, shell-style comments are additionally
+allowed. They are terminated by the first carriage-return or line-feed
+character, after which more white-space and comments are allowed.
+  [
+     1, # this comment not allowed in JSON
+        # neither this one...
+  ]
+=back
 =item $json = $json->canonical ([$enable])
+=item $enabled = $json->get_canonical
 If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
 by sorting their keys. This is adding a comparatively high overhead.
 If C<$enable> is false, then the C<encode> method will output key-value
 pairs in the order Perl stores them (which will likely change between runs
 of the same script).
 This option is useful if you want the same data structure to be encoded as
 the same JSON text (given the same overall settings). If it is disabled,
-the same hash migh be encoded differently even if contains the same data,
+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.
 =item $json = $json->allow_nonref ([$enable])
+=item $enabled = $json->get_allow_nonref
 If C<$enable> is true (or missing), then the C<encode> method can convert a
 non-reference into its corresponding string, number or null JSON value,
 which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
 values instead of croaking.
    JSON::XS->new->allow_nonref->encode ("Hello, World!")
    => "Hello, World!"
 =item $json = $json->allow_blessed ([$enable])
+=item $enabled = $json->get_allow_blessed
 If C<$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>
+B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
-disabled or no C<to_json> method found) or a representation of the
+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
+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])
+=item $enabled = $json->get_convert_blessed
 If C<$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
 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 the user of the object) are
+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>
+usually in upper case letters and to avoid collisions with any C<to_json>
-function.
+function or method.
 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->($hashref)])
+When C<$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, any existing callback will
+be removed and C<decode> will not change the deserialised hash in any
+way.
+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
+   # so a lone 5 is not allowed.
+   $js->decode ('{"a":1, "b":2}');
+=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
+Works remotely similar to C<filter_json_object>, but is only called for
+JSON objects having a single key named C<$key>.
+This C<$coderef> is called before the one specified via
+C<filter_json_object>, if any. It gets passed the single value in the JSON
+object. If it returns a single value, it will be inserted into the data
+structure. If it returns nothing (not even C<undef> but the empty list),
+the callback from C<filter_json_object> will be called next, as if no
+single-key callback were specified.
+If C<$coderef> is omitted or undefined, the corresponding callback will be
+disabled. There can only ever be one callback for a given key.
+As this callback gets called less often then the C<filter_json_object>
+one, decoding speed will not usually suffer as much. Therefore, single-key
+objects make excellent targets to serialise Perl objects into, especially
+as single-key JSON objects are as close to the type-tagged value concept
+as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
+support this in any way, so you need to make sure your data never looks
+like a serialised Perl hash.
+Typical names for the single object key are C<__class_whatever__>, or
+C<$__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 (__widget__ => sub {
+            $WIDGET{ $_[0] }
+         })
+      ->decode ('{"__widget__": 5')
+   # this can be used with a TO_JSON method in some "widget" class
+   # for serialisation to json:
+   sub WidgetBase::TO_JSON {
+      my ($self) = @_;
+      unless ($self->{id}) {
+         $self->{id} = ..get..some..id..;
+         $WIDGET{$self->{id}} = $self;
+      }
+      { __widget__ => $self->{id} }
+   }
 =item $json = $json->shrink ([$enable])
+=item $enabled = $json->get_shrink
 Perl usually over-allocates memory a bit when allocating space for
 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
 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])
+=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
 higher nesting level then this limit, then the encoder and decoder will
 stop and croak at that point.
 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])
+=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
+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)
 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).
 For the more enlightened: note that in the following descriptions,
-lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
+lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
 refers to the abstract Perl language itself.
 =head2 JSON -> PERL
 =over 4
 =item object
 A JSON object becomes a reference to a hash in Perl. No ordering of object
-keys is preserved (JSON does not preserver object key ordering itself).
+keys is preserved (JSON does not preserve object key ordering itself).
 =item array
 A JSON array becomes a reference to an array in Perl.
 are represented by the same codepoints in the Perl string, so no manual
 decoding is necessary.
 =item number
-A JSON number becomes either an integer or numeric (floating point)
+A JSON number becomes either an integer, numeric (floating point) or
-scalar in perl, depending on its range and any fractional parts. On the
+string scalar in perl, depending on its range and any fractional parts. On
-Perl level, there is no difference between those as Perl handles all the
+the Perl level, there is no difference between those as Perl handles all
-conversion details, but an integer may take slightly less memory and might
+the conversion details, but an integer may take slightly less memory and
-represent more values exactly than (floating point) numbers.
+might represent more values exactly than floating point numbers.
+If the number consists of digits only, JSON::XS will try to represent
+it as an integer value. If that fails, it will try to represent it as
+a numeric (floating point) value if that is possible without loss of
+precision. Otherwise it will preserve the number as a string value (in
+which case you lose roundtripping ability, as the JSON number will be
+re-encoded toa JSON string).
+Numbers containing a fractional or exponential part will always be
+represented as numeric (floating point) values, possibly at a loss of
+precision (in which case you might lose perfect roundtripping ability, but
+the JSON number will still be re-encoded as a JSON number).
 =item true, false
 These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
 respectively. They are overloaded to act almost exactly like the numbers
-C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
+C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
 the C<JSON::XS::is_bool> function.
 =item null
 A JSON null atom becomes C<undef> in Perl.
 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]
+   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 cna alos use C<\1> and C<\0> directly if you want.
+respectively. You can also 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
+Blessed objects are not directly representable in JSON. See the
-underlying representation (hash- or arrayref), but this behaviour might
+C<allow_blessed> and C<convert_blessed> methods on various options on
-change in future versions.
+how to deal with this: basically, you can choose between throwing an
+exception, encoding the reference as if it weren't blessed, or provide
+your own serialiser method.
 =item simple scalars
 Simple Perl scalars (any scalar that is not a reference) are the most
 difficult objects to encode: JSON::XS will encode undefined scalars as
-JSON null value, scalars that have last been used in a string context
+JSON C<null> values, scalars that have last been used in a string context
-before encoding as JSON strings and anything else as number value:
+before encoding as JSON strings, and anything else as number value:
    # dump as number
-   to_json [2]                      # yields [2]
+   encode_json [2]                      # yields [2]
-   to_json [-3.0e17]                # yields [-3e+17]
+   encode_json [-3.0e17]                # yields [-3e+17]
-   my $value = 5; to_json [$value]  # yields [5]
+   my $value = 5; encode_json [$value]  # yields [5]
    # used as string, so dump as string
    print $value;
-   to_json [$value]                 # yields ["5"]
+   encode_json [$value]                 # yields ["5"]
    # undef becomes null
-   to_json [undef]                  # yields [null]
+   encode_json [undef]                  # yields [null]
-You can force the type to be a string by stringifying it:
+You can force the type to be a JSON string by stringifying it:
    my $x = 3.1; # some variable containing a number
    "$x";        # stringified
    $x .= "";    # another, more awkward way to stringify
    print $x;    # perl does it for you, too, quite often
-You can force the type to be a number by numifying it:
+You can force the type to be a JSON number by numifying it:
    my $x = "3"; # some variable containing a string
    $x += 0;     # numify it, ensuring it will be dumped as a number
-   $x *= 1;     # same thing, the choise is yours.
+   $x *= 1;     # same thing, the choice is yours.
-You can not currently output JSON booleans or force the type in other,
+You can not currently force the type in other, less obscure, ways. Tell me
-less obscure, ways. Tell me if you need this capability.
+if you need this capability (but don't forget to explain why its needed
+:).
+=back
+=head1 ENCODING/CODESET FLAG NOTES
+The interested reader might have seen a number of flags that signify
+encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
+some confusion on what these do, so here is a short comparison:
+C<utf8> controls wether the JSON text created by C<encode> (and expected
+by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
+control wether C<encode> escapes character values outside their respective
+codeset range. Neither of these flags conflict with each other, although
+some combinations make less sense than others.
+Care has been taken to make all flags symmetrical with respect to
+C<encode> and C<decode>, that is, texts encoded with any combination of
+these flag values will be correctly decoded when the same flags are used
+- in general, if you use different flag settings while encoding vs. when
+decoding you likely have a bug somewhere.
+Below comes a verbose discussion of these flags. Note that a "codeset" is
+simply an abstract set of character-codepoint pairs, while an encoding
+takes those codepoint numbers and I<encodes> them, in our case into
+octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
+and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
+the same time, which can be confusing.
+=over 4
+=item C<utf8> flag disabled
+When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
+and expect Unicode strings, that is, characters with high ordinal Unicode
+values (> 255) will be encoded as such characters, and likewise such
+characters are decoded as-is, no canges to them will be done, except
+"(re-)interpreting" them as Unicode codepoints or Unicode characters,
+respectively (to Perl, these are the same thing in strings unless you do
+funny/weird/dumb stuff).
+This is useful when you want to do the encoding yourself (e.g. when you
+want to have UTF-16 encoded JSON texts) or when some other layer does
+the encoding for you (for example, when printing to a terminal using a
+filehandle that transparently encodes to UTF-8 you certainly do NOT want
+to UTF-8 encode your data first and have Perl encode it another time).
+=item C<utf8> flag enabled
+If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
+characters using the corresponding UTF-8 multi-byte sequence, and will
+expect your input strings to be encoded as UTF-8, that is, no "character"
+of the input string must have any value > 255, as UTF-8 does not allow
+that.
+The C<utf8> flag therefore switches between two modes: disabled means you
+will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
+octet/binary string in Perl.
+=item C<latin1> or C<ascii> flags enabled
+With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
+with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
+characters as specified by the C<utf8> flag.
+If C<utf8> is disabled, then the result is also correctly encoded in those
+character sets (as both are proper subsets of Unicode, meaning that a
+Unicode string with all character values < 256 is the same thing as a
+ISO-8859-1 string, and a Unicode string with all character values < 128 is
+the same thing as an ASCII string in Perl).
+If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
+regardless of these flags, just some more characters will be escaped using
+C<\uXXXX> then before.
+Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
+encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
+encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
+a subset of Unicode), while ASCII is.
+Surprisingly, C<decode> will ignore these flags and so treat all input
+values as governed by the C<utf8> flag. If it is disabled, this allows you
+to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
+Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
+So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
+they only govern when the JSON output engine escapes a character or not.
+The main use for C<latin1> is to relatively efficiently store binary data
+as JSON, at the expense of breaking compatibility with most JSON decoders.
+The main use for C<ascii> is to force the output to not contain characters
+with values > 127, which means you can interpret the resulting string
+as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
+8-bit-encoding, and still get the same data structure back. This is useful
+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
 =head1 COMPARISON
 followed by some benchmark values. JSON::XS was designed not to suffer
 from any of these problems or limitations.
 =over 4
+=item JSON 2.xx
+A marvellous piece of engineering, this module either uses JSON::XS
+directly when available (so will be 100% compatible with it, including
+speed), or it uses JSON::PP, which is basically JSON::XS translated to
+Pure Perl, which should be 100% compatible with JSON::XS, just a bit
+slower.
+You cannot really lose by using this module.
 =item JSON 1.07
 Slow (but very portable, as it is written in pure Perl).
-Undocumented/buggy Unicode handling (how JSON handles unicode values is
+Undocumented/buggy Unicode handling (how JSON handles Unicode values is
-undocumented. One can get far by feeding it unicode strings and doing
+undocumented. One can get far by feeding it Unicode strings and doing
-en-/decoding oneself, but unicode escapes are not working properly).
+en-/decoding oneself, but Unicode escapes are not working properly).
-No roundtripping (strings get clobbered if they look like numbers, e.g.
+No round-tripping (strings get clobbered if they look like numbers, e.g.
 the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
 decode into the number 2.
 =item JSON::PC 0.01
 Very fast.
 Undocumented/buggy Unicode handling.
-No roundtripping.
+No round-tripping.
 Has problems handling many Perl values (e.g. regex results and other magic
 values will make it croak).
 Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
 Very inflexible (no human-readable format supported, format pretty much
 undocumented. I need at least a format for easy reading by humans and a
 single-line compact format for use in a protocol, and preferably a way to
 generate ASCII-only JSON texts).
-Completely broken (and confusingly documented) Unicode handling (unicode
+Completely broken (and confusingly documented) Unicode handling (Unicode
 escapes are not working properly, you need to set ImplicitUnicode to
 I<different> values on en- and decoding to get symmetric behaviour).
-No roundtripping (simple cases work, but this depends on wether the scalar
+No round-tripping (simple cases work, but this depends on whether the scalar
 value was used in a numeric context or not).
 Dumping hashes may skip hash values depending on iterator state.
 Unmaintained (maintainer unresponsive for many months, bugs are not
 getting fixed).
 Does not check input for validity (i.e. will accept non-JSON input and
 return "something" instead of raising an exception. This is a security
-issue: imagine two banks transfering money between each other using
+issue: imagine two banks transferring money between each other using
 JSON. One bank might parse a given non-JSON request and deduct money,
 while the other might reject the transaction with a syntax error. While a
 good protocol will at least recover, that is extra unnecessary work and
 the transaction will still not succeed).
 =item JSON::DWIW 0.04
 Very fast. Very natural. Very nice.
-Undocumented unicode handling (but the best of the pack. Unicode escapes
+Undocumented Unicode handling (but the best of the pack. Unicode escapes
 still don't get parsed properly).
 Very inflexible.
-No roundtripping.
+No round-tripping.
 Does not generate valid JSON texts (key strings are often unquoted, empty keys
 result in nothing being output)
 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,
+You often hear that JSON is a subset of YAML. This is, however, a mass
-however, a mass hysteria and very far from the truth. In general, there is
+hysteria(*) and very far from the truth. In general, there is no way to
-no way to configure JSON::XS to output a data structure as valid YAML.
+configure JSON::XS to output a data structure as valid YAML that works for
+all cases.
 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
+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, so you should make sure that your hash
+lengths that JSON doesn't have and also has different and incompatible
+unicode handling, so you should make sure that your hash keys are
-keys are noticably shorter than the 1024 characters YAML allows.
+noticeably shorter than the 1024 "stream characters" YAML allows and that
+you do not have codepoints with values outside the Unicode BMP (basic
+multilingual page). YAML also does not allow C<\/> sequences in strings
+(which JSON::XS does not I<currently> generate).
-There might be other incompatibilities that I am not aware of. In general
+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
-you should not try to generate YAML with a JSON generator or vice versa,
+general you should not try to generate YAML with a JSON generator or vice
-or try to parse JSON with a YAML parser or vice versa: chances are high
+versa, or try to parse JSON with a YAML parser or vice versa: chances are
-that you will run into severe interoperability problems.
+high that you will run into severe interoperability problems when you
+least expect it.
+=over 4
+=item (*)
+This is spread actively by the YAML team, however. For many years now they
+claim YAML were a superset of JSON, even when proven otherwise.
+Even the author of this manpage was at some point accused of providing
+"incorrect" information, despite the evidence presented (claims ranged
+from "your documentation contains inaccurate and negative statements about
+YAML" (the only negative comment is this footnote, and it didn't exist
+back then; the question on which claims were inaccurate was never answered
+etc.) to "the YAML spec is not up-to-date" (the *real* and supposedly
+JSON-compatible spec is apparently not currently publicly available)
+to actual requests to replace this section by *incorrect* information,
+suppressing information about the real problem).
+So whenever you are told that YAML was a superset of JSON, first check
+wether it is really true (it might be when you check it, but it certainly
+was not true when this was written). I would much prefer if the YAML team
+would spent their time on actually making JSON compatibility a truth
+(JSON, after all, has a very small and simple specification) instead of
+trying to lobby/force people into reporting untruths.
+=back
 =head2 SPEED
 It seems that JSON::XS is surprisingly fast, as shown in the following
 with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
 shrink). Higher is better:
    module     |     encode |     decode |
    -----------|------------|------------|
-   JSON       |   7645.468 |   4208.613 |
+   JSON 1.x   |   4990.842 |   4088.813 |
-   JSON::DWIW |  40721.398 |  77101.176 |
+   JSON::DWIW |  51653.990 |  71575.154 |
-   JSON::PC   |  65948.176 |  78251.940 |
+   JSON::PC   |  65948.176 |  74631.744 |
-   JSON::Syck |  22844.793 |  26479.192 |
+   JSON::PP   |   8931.652 |   3817.168 |
+   JSON::Syck |  24877.248 |  27776.848 |
-   JSON::XS   | 388361.481 | 199728.762 |
+   JSON::XS   | 388361.481 | 227951.304 |
-   JSON::XS/2 | 218453.333 | 192399.266 |
+   JSON::XS/2 | 227951.304 | 218453.333 |
-   JSON::XS/3 | 338250.323 | 192399.266 |
+   JSON::XS/3 | 338250.323 | 218453.333 |
-   Storable   |  15779.925 |  14169.946 |
+   Storable   |  16500.016 | 135300.129 |
    -----------+------------+------------+
 That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
-about three times faster on decoding, and over fourty times faster
+about three times faster on decoding, and over forty times 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       |    254.685 |     37.665 |
+   JSON 1.x   |     55.260 |     34.971 |
-   JSON::DWIW |    843.343 |   1049.731 |
+   JSON::DWIW |    825.228 |   1082.513 |
-   JSON::PC   |   3602.116 |   2307.352 |
+   JSON::PC   |   3571.444 |   2394.829 |
+   JSON::PP   |    210.987 |     32.574 |
-   JSON::Syck |    505.107 |    787.899 |
+   JSON::Syck |    552.551 |    787.544 |
-   JSON::XS   |   5747.196 |   3690.220 |
+   JSON::XS   |   5780.463 |   4854.519 |
-   JSON::XS/2 |   3968.121 |   3676.634 |
+   JSON::XS/2 |   3869.998 |   4798.975 |
-   JSON::XS/3 |   6105.246 |   3662.508 |
+   JSON::XS/3 |   5862.880 |   4798.975 |
-   Storable   |   4417.337 |   5285.161 |
+   Storable   |   4445.002 |   5235.027 |
    -----------+------------+------------+
 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
+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
+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
 comparison table for that case.
 =head1 SECURITY CONSIDERATIONS
 any buffer overflows. Obviously, this module should ensure that and I am
 trying hard on making that true, but you never know.
 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
+resources run out, that's 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 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. to be
+to free the temporary). If that is exceeded, the program crashes. 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
 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 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
+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
+L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
 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
+browser developers care only for features, not about getting security
 right).
+=head1 THREADS
+This module is I<not> guaranteed to be thread safe and there are no
+plans to change this until Perl gets thread support (as opposed to the
+horribly slow so-called "threads" which are simply slow and bloated
+process simulations - use fork, its I<much> faster, cheaper, better).
+(It might actually work, but you have been warned).
 =head1 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 they
 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
 our $true  = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
 our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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Revision 1.84 by root, Wed Mar 19 02:52:15 2008 UTC