--- JSON-XS/XS.pm 2007/03/23 16:00:19 1.9 +++ JSON-XS/XS.pm 2007/03/24 22:57:12 1.19 @@ -6,6 +6,17 @@ 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 @@ -20,13 +31,17 @@ 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 @@ -36,12 +51,14 @@ =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). +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. +Compared to other JSON modules, this module compares favourably in terms +of speed, too. =item * simple to use @@ -50,8 +67,10 @@ =item * reasonably versatile output formats -You can choose between the most compact format possible, a pure-ascii -format, or a pretty-printed format. Or you can combine those features in +You can choose between the most compact guarenteed single-line format +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 @@ -61,7 +80,7 @@ package JSON::XS; BEGIN { - $VERSION = '0.3'; + $VERSION = '0.7'; @ISA = qw(Exporter); @EXPORT = qw(to_json from_json); @@ -78,23 +97,29 @@ =over 4 -=item $json_string = to_json $perl_scalar +=item $json_text = to_json $perl_scalar Converts the given Perl data structure (a simple scalar or a reference to a hash or array) to a UTF-8 encoded, binary string (that is, the string contains octets only). Croaks on error. -This function call is functionally identical to C<< JSON::XS->new->utf8 -(1)->encode ($perl_scalar) >>. +This function call is functionally identical to: -=item $perl_scalar = from_json $json_string + $json_text = JSON::XS->new->utf8->encode ($perl_scalar) + +except being faster. + +=item $perl_scalar = from_json $json_text The opposite of C: expects an UTF-8 (binary) string and tries to -parse that as an UTF-8 encoded JSON string, returning the resulting simple +parse that as an UTF-8 encoded JSON text, returning the resulting simple scalar or reference. Croaks on error. -This function call is functionally identical to C<< JSON::XS->new->utf8 -(1)->decode ($json_string) >>. +This function call is functionally identical to: + + $perl_scalar = JSON::XS->new->utf8->decode ($json_text) + +except being faster. =back @@ -113,42 +138,57 @@ The mutators for flags all return the JSON object again and thus calls can be chained: - my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]}) + my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) => {"a": [1, 2]} =item $json = $json->ascii ([$enable]) -If C<$enable> is true (or missing), then the C method will -not generate characters outside the code range C<0..127>. Any unicode -characters outside that range will be escaped using either a single -\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per -RFC4627. +If C<$enable> is true (or missing), then the C 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 +single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, +as per RFC4627. If C<$enable> is false, then the C method will not escape Unicode -characters unless necessary. +characters unless required by the JSON syntax. This results in a faster +and more compact format. - JSON::XS->new->ascii (1)->encode (chr 0x10401) - => \ud801\udc01 + JSON::XS->new->ascii (1)->encode ([chr 0x10401]) + => ["\ud801\udc01"] =item $json = $json->utf8 ([$enable]) If C<$enable> is true (or missing), then the C method will encode -the JSON string into UTF-8, as required by many protocols, while the +the JSON result into UTF-8, as required by many protocols, while the C method expects to be handled an UTF-8-encoded string. Please note that UTF-8-encoded strings do not contain any characters outside the -range C<0..255>, they are thus useful for bytewise/binary I/O. +range C<0..255>, they are thus useful for bytewise/binary I/O. In future +versions, enabling this option might enable autodetection of the UTF-16 +and UTF-32 encoding families, as described in RFC4627. If C<$enable> is false, then the C method will return the JSON string as a (non-encoded) unicode string, while C 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-16BE-encoded JSON: + + use Encode; + $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); + +Example, decode UTF-32LE-encoded JSON: + + use Encode; + $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext); + =item $json = $json->pretty ([$enable]) This enables (or disables) all of the C, C and C (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 $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]}) => { @@ -165,9 +205,9 @@ into its own line, identing them properly. If C<$enable> is false, no newlines or indenting will be produced, and the -resulting JSON strings is guarenteed not to contain any C. +resulting JSON text is guarenteed not to contain any C. -This setting has no effect when decoding JSON strings. +This setting has no effect when decoding JSON texts. =item $json = $json->space_before ([$enable]) @@ -177,8 +217,12 @@ If C<$enable> is false, then the C 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. +This setting has no effect when decoding JSON texts. You will also +most likely combine this setting with C. + +Example, space_before enabled, space_after and indent disabled: + + {"key" :"value"} =item $json = $json->space_after ([$enable]) @@ -190,7 +234,11 @@ If C<$enable> is false, then the C method will not add any extra space at those places. -This setting has no effect when decoding JSON strings. +This setting has no effect when decoding JSON texts. + +Example, space_before and indent disabled, space_after enabled: + + {"key": "value"} =item $json = $json->canonical ([$enable]) @@ -202,11 +250,11 @@ of the same script). This option is useful if you want the same data structure to be encoded as -the same JSON string (given the same overall settings). If it is disabled, +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, as key-value pairs have no inherent ordering in Perl. -This setting has no effect when decoding JSON strings. +This setting has no effect when decoding JSON texts. =item $json = $json->allow_nonref ([$enable]) @@ -216,16 +264,22 @@ values instead of croaking. If C<$enable> is false, then the C method will croak if it isn't -passed an arrayref or hashref, as JSON strings must either be an object +passed an arrayref or hashref, as JSON texts must either be an object or array. Likewise, C will croak if given something that is not a JSON object or array. +Example, encode a Perl scalar as JSON value with enabled C, +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 or C to their minimum size possible. This can save -memory when your JSON strings are either very very long or you have many +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 @@ -241,7 +295,7 @@ 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) +=item $json_text = $json->encode ($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 @@ -250,9 +304,9 @@ Perl values (e.g. C) become JSON C values. Neither C nor C values will be generated. -=item $perl_scalar = $json->decode ($json_string) +=item $perl_scalar = $json->decode ($json_text) -The opposite of C: expects a JSON string and tries to parse it, +The opposite of C: expects a JSON text and tries to parse it, returning the resulting simple scalar or reference. Croaks on error. JSON numbers and strings become simple Perl scalars. JSON arrays become @@ -261,6 +315,126 @@ =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 refers to the Perl interpreter, while uppcercase I +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 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 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 @@ -295,7 +469,7 @@ values will make it croak). Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> -which is not a valid JSON string. +which is not a valid JSON text. Unmaintained (maintainer unresponsive for many months, bugs are not getting fixed). @@ -307,7 +481,7 @@ 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 strings). +generate ASCII-only JSON texts). Completely broken (and confusingly documented) Unicode handling (unicode escapes are not working properly, you need to set ImplicitUnicode to @@ -340,7 +514,7 @@ No roundtripping. -Does not generate valid JSON (key strings are often unquoted, empty keys +Does not generate valid JSON texts (key strings are often unquoted, empty keys result in nothing being output) Does not check input for validity. @@ -354,42 +528,56 @@ 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 -string, showing the number of encodes/decodes per second (JSON::XS is -the functional interface, while JSON::XS/2 is the OO interface with -pretty-printing and hashkey sorting enabled). +First comes a comparison between various modules using a very short JSON +string: + + {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} + +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: module | encode | decode | -----------|------------|------------| - JSON | 14006 | 6820 | - JSON::DWIW | 200937 | 120386 | - JSON::PC | 85065 | 129366 | - JSON::Syck | 59898 | 44232 | - JSON::XS | 1171478 | 342435 | - JSON::XS/2 | 730760 | 328714 | + JSON | 11488.516 | 7823.035 | + JSON::DWIW | 94708.054 | 129094.260 | + JSON::PC | 63884.157 | 128528.212 | + JSON::Syck | 34898.677 | 42096.911 | + JSON::XS | 654027.064 | 396423.669 | + JSON::XS/2 | 371564.190 | 371725.613 | -----------+------------+------------+ -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. +That is, JSON::XS is more than six times faster than JSON::DWIW on +encoding, more than three times faster on decoding, and about thirty 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 | - JSON::DWIW | 5271 | 770 | - JSON::PC | 9901 | 2491 | - JSON::Syck | 2360 | 786 | - JSON::XS | 37398 | 3202 | - JSON::XS/2 | 13765 | 3153 | + JSON | 273.023 | 44.674 | + JSON::DWIW | 1089.383 | 1145.704 | + JSON::PC | 3097.419 | 2393.921 | + JSON::Syck | 514.060 | 843.053 | + JSON::XS | 6479.668 | 3636.364 | + JSON::XS/2 | 3774.221 | 3599.124 | -----------+------------+------------+ -Again, JSON::XS leads by far in the encoding case, while still beating -every other module in the decoding case. +Again, JSON::XS leads by far. -Last example is an almost 8MB large hash with many large binary values -(PNG files), resulting in a lot of escaping: +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 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