--- JSON-XS/XS.pm 2007/03/22 23:24:18 1.6 +++ JSON-XS/XS.pm 2007/03/24 19:42:14 1.17 @@ -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 = '0.2'; + $VERSION = '0.5'; @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 @@ -113,41 +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) +=item $json = $json->ascii ([$enable]) -If C<$enable> is true, then the C method will not generate -characters outside the code range C<0..127>. Any unicode characters -outside that range will be escaped using either a single \uXXXX (BMP -characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627. +If C<$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) +=item $json = $json->utf8 ([$enable]) -If C<$enable> is true, then the C method will encode the JSON -string into UTF-8, as required by many protocols, while the C -method expects to be handled an UTF-8-encoded string. Please note that -UTF-8-encoded strings do not contain any characters outside the range -C<0..255>, they are thus useful for bytewise/binary I/O. +If C<$enable> is true (or missing), then the C method will encode +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. 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. -=item $json = $json->pretty ($enable) +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]}) => { @@ -157,31 +198,35 @@ ] } -=item $json = $json->indent ($enable) +=item $json = $json->indent ([$enable]) -If C<$enable> is true, then the C method will use a multiline +If C<$enable> is true (or missing), then the C 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. +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) +=item $json = $json->space_before ([$enable]) -If C<$enable> is true, then the C method will add an extra +If C<$enable> is true (or missing), then the C 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 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: -=item $json = $json->space_after ($enable) + {"key" :"value"} -If C<$enable> is true, then the C method will add an extra +=item $json = $json->space_after ([$enable]) + +If C<$enable> is true (or missing), then the C method will add an extra optional space after the C<:> separating keys from values in JSON objects and extra whitespace after the C<,> separating key-value pairs and array members. @@ -189,11 +234,15 @@ If C<$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: -=item $json = $json->canonical ($enable) + {"key": "value"} -If C<$enable> is true, then the C method will output JSON objects +=item $json = $json->canonical ([$enable]) + +If C<$enable> is true (or missing), then the C method will output JSON objects by sorting their keys. This is adding a comparatively high overhead. If C<$enable> is false, then the C method will output key-value @@ -201,25 +250,52 @@ 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) +=item $json = $json->allow_nonref ([$enable]) -If C<$enable> is true, then the C method can convert a +If C<$enable> is true (or missing), then the C method can convert a non-reference into its corresponding string, number or null JSON value, which is an extension to RFC4627. Likewise, C will accept those JSON 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. -=item $json_string = $json->encode ($perl_scalar) +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 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 +space in general. + +If C<$enable> is true (or missing), the string returned by C will be shrunk-to-fit, +while all strings generated by C will also be shrunk-to-fit. + +If C<$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_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 @@ -228,9 +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 @@ -239,6 +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 @@ -273,7 +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). @@ -285,7 +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 @@ -318,7 +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. @@ -332,10 +528,11 @@ 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 (83 bytes), 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). Higher is +better: module | encode | decode | -----------|------------|------------| @@ -350,7 +547,7 @@ 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 | @@ -366,8 +563,18 @@ 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 -(PNG files), resulting in a lot of escaping: +On large strings containing lots of unicode characters, some modules +(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