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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.4 by root, Thu Mar 22 21:13:58 2007 UTC vs.
Revision 1.14 by root, Fri Mar 23 19:02:02 2007 UTC

 JSON::XS - JSON serialising/deserialising, done correctly and fast
 =head1 SYNOPSIS
  use JSON::XS;
+ # exported functions, croak on error
+ $utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
+ $perl_hash_or_arrayref  = from_json $utf8_encoded_json_text;
+ # oo-interface
+ $coder = JSON::XS->new->ascii->pretty->allow_nonref;
+ $pretty_printed_unencoded = $coder->encode ($perl_scalar);
+ $perl_scalar = $coder->decode ($unicode_json_text);
 =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
 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
 =over 4
 =item * correct handling of unicode issues
-This module knows how to handle Unicode, and even documents how it does so.
+This module knows how to handle Unicode, and even documents how and when
+it does so.
 =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").
 =item * strict checking of JSON correctness
 There is no guessing, no generating of illegal JSON strings by default,
-and only JSON is accepted as input (the latter is a security feature).
+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.
+Compared to other JSON modules, this module compares favourably in terms
+of speed, too.
 =item * simple to use
 This module has both a simple functional interface as well as an OO
 interface.
 =item * reasonably versatile output formats
-You can choose between the most compact format possible, a pure-ascii
+You can choose between the most compact guarenteed single-line format
-format, or a pretty-printed format. Or you can combine those features in
+possible (nice for simple line-based protocols), a pure-ascii format (for
+when your transport is not 8-bit clean), 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;
 BEGIN {
-   $VERSION = '0.1';
+   $VERSION = '0.3';
    @ISA = qw(Exporter);
    @EXPORT = qw(to_json from_json);
    require Exporter;
 Converts the given Perl data structure (a simple scalar or a reference to
 a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
 octets only). Croaks on error.
-This function call is functionally identical to C<< JSON::XS->new->utf8
+This function call is functionally identical to C<< JSON::XS->new->utf8->encode ($perl_scalar) >>.
-(1)->encode ($perl_scalar) >>.
 =item $perl_scalar = from_json $json_string
 The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
 parse that as an UTF-8 encoded JSON string, returning the resulting simple
 scalar or reference. Croaks on error.
-This function call is functionally identical to C<< JSON::XS->new->utf8
+This function call is functionally identical to C<< JSON::XS->new->utf8->decode ($json_string) >>.
-(1)->decode ($json_string) >>.
 =back
 =head1 OBJECT-ORIENTED INTERFACE
 be chained:
    my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})
    => {"a": [1, 2]}
-=item $json = $json->ascii ($enable)
+=item $json = $json->ascii ([$enable])
-If C<$enable> is true, then the C<encode> method will not generate
+If C<$enable> is true (or missing), then the C<encode> method will
-characters outside the code range C<0..127>. Any unicode characters
+not generate characters outside the code range C<0..127>. Any unicode
-outside that range will be escaped using either a single \uXXXX (BMP
+characters outside that range will be escaped using either a single
-characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.
+\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per
+RFC4627.
 If C<$enable> is false, then the C<encode> method will not escape Unicode
 characters unless necessary.
   JSON::XS->new->ascii (1)->encode (chr 0x10401)
   => \ud801\udc01
-=item $json = $json->utf8 ($enable)
+=item $json = $json->utf8 ([$enable])
-If C<$enable> is true, then the C<encode> method will encode the JSON
+If C<$enable> is true (or missing), then the C<encode> method will encode
-string into UTF-8, as required by many protocols, while the C<decode>
+the JSON string into UTF-8, as required by many protocols, while the
-method expects to be handled an UTF-8-encoded string.  Please note that
+C<decode> method expects to be handled an UTF-8-encoded string.  Please
-UTF-8-encoded strings do not contain any characters outside the range
+note that UTF-8-encoded strings do not contain any characters outside the
-C<0..255>, they are thus useful for bytewise/binary I/O.
+range C<0..255>, they are thus useful for bytewise/binary I/O.
 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
 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-16-encoded JSON:
-=item $json = $json->pretty ($enable)
+=item $json = $json->pretty ([$enable])
 This enables (or disables) all of the C<indent>, C<space_before> and
 C<space_after> (and in the future possibly more) flags in one call to
 generate the most readable (or most compact) form possible.
+Example, pretty-print some simple structure:
    my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
    =>
    {
       "a" : [
          1,
          2
       ]
    }
-=item $json = $json->indent ($enable)
+=item $json = $json->indent ([$enable])
-If C<$enable> is true, then the C<encode> method will use a multiline
+If C<$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.
 If C<$enable> is false, no newlines or indenting will be produced, and the
 resulting JSON strings is guarenteed not to contain any C<newlines>.
 This setting has no effect when decoding JSON strings.
-=item $json = $json->space_before ($enable)
+=item $json = $json->space_before ([$enable])
-If C<$enable> is true, then the C<encode> method will add an extra
+If C<$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
 space at those places.
 This setting has no effect when decoding JSON strings. You will also most
 likely combine this setting with C<space_after>.
+Example, space_before enabled, space_after and indent disabled:
+   {"key" :"value"}
-=item $json = $json->space_after ($enable)
+=item $json = $json->space_after ([$enable])
-If C<$enable> is true, then the C<encode> method will add an extra
+If C<$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.
 If C<$enable> is false, then the C<encode> method will not add any extra
 space at those places.
 This setting has no effect when decoding JSON strings.
+Example, space_before and indent disabled, space_after enabled:
+   {"key": "value"}
-=item $json = $json->canonical ($enable)
+=item $json = $json->canonical ([$enable])
-If C<$enable> is true, then the C<encode> method will output JSON objects
+If C<$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).
 the same hash migh 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 strings.
-=item $json = $json->allow_nonref ($enable)
+=item $json = $json->allow_nonref ([$enable])
-If C<$enable> is true, then the C<encode> method can convert a
+If C<$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.
 If C<$enable> is false, then the C<encode> method will croak if it isn't
 passed an arrayref or hashref, as JSON strings must either be an object
 or array. Likewise, C<decode> will croak if given something that is not a
 JSON object or array.
+Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
+resulting in an invalid JSON text:
+   JSON::XS->new->allow_nonref->encode ("Hello, World!")
+   => "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
+C<encode> or C<decode> to their minimum size possible. This can save
+memory when your JSON strings 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.
+If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,
+while all strings generated by C<decode> will also be shrunk-to-fit.
+If C<$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_string = $json->encode ($perl_scalar)
 Converts the given Perl data structure (a simple scalar or a reference
 to a hash or array) to its JSON representation. Simple scalars will be
 Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
 C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
 =back
+=head1 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).
+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
+=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).
+=item array
+A JSON array becomes a reference to an array in Perl.
+=item string
+A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
+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)
+scalar in perl, depending on its range and any fractional parts. On the
+Perl level, there is no difference between those as Perl handles all the
+conversion details, but an integer may take slightly less memory and might
+represent more values exactly than (floating point) numbers.
+=item true, false
+These JSON atoms become C<0>, C<1>, respectively. Information is lost in
+this process. Future versions might represent those values differently,
+but they will be guarenteed to act like these integers would normally in
+Perl.
+=item null
+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
+can change between runs of the same program but stays generally the same
+within a single run of a program. JSON::XS can optionally sort the hash
+keys (determined by the I<canonical> flag), so the same datastructure
+will serialise to the same JSON text (given same settings and version of
+JSON::XS), but this incurs a runtime overhead.
+=item array references
+Perl array references become JSON arrays.
+=item 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.
+=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
+before encoding as JSON strings and anything else as number value:
+   # dump as number
+   to_json [2]                      # yields [2]
+   to_json [-3.0e17]                # yields [-3e+17]
+   my $value = 5; to_json [$value]  # yields [5]
+   # used as string, so dump as string
+   print $value;
+   to_json [$value]                 # yields ["5"]
+   # undef becomes null
+   to_json [undef]                  # yields [null]
+You can force the type to be a 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:
+   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.
+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
 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 JSON modules,
 followed by some benchmark values. JSON::XS was designed not to suffer
 from any of these problems or limitations.
 =over 4
-=item JSON
+=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. One can get far by feeding it unicode strings and doing
 No roundtripping (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
+=item JSON::PC 0.01
 Very fast.
 Undocumented/buggy Unicode handling.
 which is not a valid JSON string.
 Unmaintained (maintainer unresponsive for many months, bugs are not
 getting fixed).
-=item JSON::Syck
+=item JSON::Syck 0.21
 Very buggy (often crashes).
 Very inflexible (no human-readable format supported, format pretty much
 undocumented. I need at least a format for easy reading by humans and a
 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
+=item JSON::DWIW 0.04
 Very fast. Very natural. Very nice.
 Undocumented unicode handling (but the best of the pack. Unicode escapes
 still don't get parsed properly).
 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 is a comparison between various modules using a very simple JSON
+First comes a comparison between various modules using a very short JSON
-string, showing the number of encodes/decodes per second (JSON::XS is
+string (83 bytes), showing the number of encodes/decodes per second
-the functional interface, while JSON::XS/2 is the OO interface with
+(JSON::XS is the functional interface, while JSON::XS/2 is the OO
-pretty-printing and hashkey sorting enabled).
+interface with pretty-printing and hashkey sorting enabled). Higher is
+better:
    module     |     encode |     decode |
    -----------|------------|------------|
    JSON       |      14006 |       6820 |
    JSON::DWIW |     200937 |     120386 |
    -----------+------------+------------+
 That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80
 times faster than JSON, even with pretty-printing and key sorting.
-Using a longer test string (roughly 8KB, generated from Yahoo! Locals
+Using a longer test string (roughly 18KB, generated from Yahoo! Locals
 search API (http://nanoref.com/yahooapis/mgPdGg):
    module     |     encode |     decode |
    -----------|------------|------------|
    JSON       |        673 |         38 |
    -----------+------------+------------+
 Again, JSON::XS leads by far in the encoding case, while still beating
 every other module in the decoding case.
-Last example is an almost 8MB large hash with many large binary values
+On large strings containing lots of unicode characters, some modules
-(PNG files), resulting in a lot of escaping:
+(such as JSON::PC) decode faster than JSON::XS, but the result will be
+broken due to missing unicode handling. Others refuse to decode or encode
+properly, so it was impossible to prepare a fair comparison table for that
+case.
+=head1 RESOURCE LIMITS
+JSON::XS does not impose any limits on the size of JSON texts or Perl
+values they represent - if your machine can handle it, JSON::XS will
+encode or decode it. Future versions might optionally impose structure
+depth and memory use resource limits.
 =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

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Comparing JSON-XS/XS.pm (file contents): Revision 1.4 by root, Thu Mar 22 21:13:58 2007 UTC vs. Revision 1.14 by root, Fri Mar 23 19:02:02 2007 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.4 by root, Thu Mar 22 21:13:58 2007 UTC vs.
Revision 1.14 by root, Fri Mar 23 19:02:02 2007 UTC