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@@ -1,78 +1,360 @@ -Dependencies for Building -========================= +== json - JSON Implementation for Ruby -- You need rake to build the extensions and install them. +=== Description - You can get it from rubyforge: - http://rubyforge.org/projects/rake +This is a implementation of the JSON specification according to RFC 4627 +(http://www.ietf.org/rfc/rfc4627.txt). Starting from version 1.0.0 on there +will be two variants available: - or just type +* A pure ruby variant, that relies on the iconv and the stringscan + extensions, which are both part of the ruby standard library. +* The quite a bit faster C extension variant, which is in parts implemented + in C and comes with its own unicode conversion functions and a parser + generated by the ragel state machine compiler + (http://www.cs.queensu.ca/~thurston/ragel). - # gem install rake +Both variants of the JSON generator escape all non-ASCII and control characters +with \uXXXX escape sequences, and support UTF-16 surrogate pairs in order to be +able to generate the whole range of unicode code points. This means that +generated JSON document is encoded as UTF-8 (because ASCII is a subset of +UTF-8) and at the same time avoids decoding problems for receiving endpoints, +that don't expect UTF-8 encoded texts. On the negative side this may lead to a +bit longer strings than necessarry. - for the installation via rubygems. +All strings, that are to be encoded as JSON strings, should be UTF-8 byte +sequences on the Ruby side. To encode raw binary strings, that aren't UTF-8 +encoded, please use the to_json_raw_object method of String (which produces +an object, that contains a byte array) and decode the result on the receiving +endpoint. -- If you want to rebuild the parser.c file or draw nice graphviz images of the - state machines, you need ragel from: - http://www.cs.queensu.ca/~thurston/ragel +The JSON parsers can parse UTF-8, UTF-16BE, UTF-16LE, UTF-32BE, and UTF-32LE +JSON documents under Ruby 1.8. Under Ruby 1.9 they take advantage of Ruby's +M17n features and can parse all documents which have the correct +String#encoding set. If a document string has ASCII-8BIT as an encoding the +parser attempts to figure out which of the UTF encodings from above it is and +trys to parse it. -Installation -============ +=== Installation -It's recommended to use the extension variant of JSON, because it's quite a bit -faster than the pure ruby variant. If you cannot build it on your system, you -can settle for the latter. +It's recommended to use the extension variant of JSON, because it's faster than +the pure ruby variant. If you cannot build it on your system, you can settle +for the latter. Just type into the command line as root: -# rake install + # rake install The above command will build the extensions and install them on your system. -# rake install_pure + # rake install_pure or -# ruby install.rb + # ruby install.rb will just install the pure ruby implementation of JSON. If you use Rubygems you can type -# gem install json + # gem install json instead, to install the newest JSON version. There is also a pure ruby json only variant of the gem, that can be installed with: -# gem install json_pure + # gem install json_pure + +=== Compiling the extensions yourself + +If you want to build the extensions yourself you need rake: + + You can get it from rubyforge: + http://rubyforge.org/projects/rake + + or just type + + # gem install rake + + for the installation via rubygems. + +If you want to create the parser.c file from its parser.rl file or draw nice +graphviz images of the state machines, you need ragel from: http://www.cs.queensu.ca/~thurston/ragel + + +=== Usage + +To use JSON you can + require 'json' +to load the installed variant (either the extension 'json' or the pure +variant 'json_pure'). If you have installed the extension variant, you can +pick either the extension variant or the pure variant by typing + require 'json/ext' +or + require 'json/pure' + +Now you can parse a JSON document into a ruby data structure by calling + + JSON.parse(document) + +If you want to generate a JSON document from a ruby data structure call + JSON.generate(data) + +You can also use the pretty_generate method (which formats the output more +verbosely and nicely) or fast_generate (which doesn't do any of the security +checks generate performs, e. g. nesting deepness checks). + +To create a valid JSON document you have to make sure, that the output is +embedded in either a JSON array [] or a JSON object {}. The easiest way to do +this, is by putting your values in a Ruby Array or Hash instance. + +There are also the JSON and JSON[] methods which use parse on a String or +generate a JSON document from an array or hash: + + document = JSON 'test' => 23 # => "{\"test\":23}" + document = JSON['test'] => 23 # => "{\"test\":23}" + +and + + data = JSON '{"test":23}' # => {"test"=>23} + data = JSON['{"test":23}'] # => {"test"=>23} + +You can choose to load a set of common additions to ruby core's objects if +you + require 'json/add/core' + +After requiring this you can, e. g., serialise/deserialise Ruby ranges: -Testing and Examples -==================== + JSON JSON(1..10) # => 1..10 -To run the tests type: +To find out how to add JSON support to other or your own classes, read the +section "More Examples" below. -$ rake test_ext +To get the best compatibility to rails' JSON implementation, you can + require 'json/add/rails' -This will build the extensions first and then test them. +Both of the additions attempt to require 'json' (like above) first, if it has +not been required yet. -$ rake test_pure +=== More Examples -This will test the pure ruby extensions. +To create a JSON document from a ruby data structure, you can call +JSON.generate like that: -There is also a small example in tools/server.rb if you want to see, how + json = JSON.generate [1, 2, {"a"=>3.141}, false, true, nil, 4..10] + # => "[1,2,{\"a\":3.141},false,true,null,\"4..10\"]" + +To get back a ruby data structure from a JSON document, you have to call +JSON.parse on it: + + JSON.parse json + # => [1, 2, {"a"=>3.141}, false, true, nil, "4..10"] + +Note, that the range from the original data structure is a simple +string now. The reason for this is, that JSON doesn't support ranges +or arbitrary classes. In this case the json library falls back to call +Object#to_json, which is the same as #to_s.to_json. + +It's possible to add JSON support serialization to arbitrary classes by +simply implementing a more specialized version of the #to_json method, that +should return a JSON object (a hash converted to JSON with #to_json) like +this (don't forget the *a for all the arguments): + + class Range + def to_json(*a) + { + 'json_class' => self.class.name, # = 'Range' + 'data' => [ first, last, exclude_end? ] + }.to_json(*a) + end + end + +The hash key 'json_class' is the class, that will be asked to deserialise the +JSON representation later. In this case it's 'Range', but any namespace of +the form 'A::B' or '::A::B' will do. All other keys are arbitrary and can be +used to store the necessary data to configure the object to be deserialised. + +If a the key 'json_class' is found in a JSON object, the JSON parser checks +if the given class responds to the json_create class method. If so, it is +called with the JSON object converted to a Ruby hash. So a range can +be deserialised by implementing Range.json_create like this: + + class Range + def self.json_create(o) + new(*o['data']) + end + end + +Now it possible to serialise/deserialise ranges as well: + + json = JSON.generate [1, 2, {"a"=>3.141}, false, true, nil, 4..10] + # => "[1,2,{\"a\":3.141},false,true,null,{\"json_class\":\"Range\",\"data\":[4,10,false]}]" + JSON.parse json + # => [1, 2, {"a"=>3.141}, false, true, nil, 4..10] + +JSON.generate always creates the shortest possible string representation of a +ruby data structure in one line. This is good for data storage or network +protocols, but not so good for humans to read. Fortunately there's also +JSON.pretty_generate (or JSON.pretty_generate) that creates a more readable +output: + + puts JSON.pretty_generate([1, 2, {"a"=>3.141}, false, true, nil, 4..10]) + [ + 1, + 2, + { + "a": 3.141 + }, + false, + true, + null, + { + "json_class": "Range", + "data": [ + 4, + 10, + false + ] + } + ] + +There are also the methods Kernel#j for generate, and Kernel#jj for +pretty_generate output to the console, that work analogous to Core Ruby's p and +the pp library's pp methods. + +The script tools/server.rb contains a small example if you want to test, how receiving a JSON object from a webrick server in your browser with the javasript prototype library (http://www.prototypejs.org) works. -Author -====== +=== Speed Comparisons + +I have created some benchmark results (see the benchmarks/data-p4-3Ghz +subdir of the package) for the JSON-parser to estimate the speed up in the C +extension: + + Comparing times (call_time_mean): + 1 ParserBenchmarkExt#parser 900 repeats: + 553.922304770 ( real) -> 21.500x + 0.001805307 + 2 ParserBenchmarkYAML#parser 1000 repeats: + 224.513358139 ( real) -> 8.714x + 0.004454078 + 3 ParserBenchmarkPure#parser 1000 repeats: + 26.755020642 ( real) -> 1.038x + 0.037376163 + 4 ParserBenchmarkRails#parser 1000 repeats: + 25.763381731 ( real) -> 1.000x + 0.038814780 + calls/sec ( time) -> speed covers + secs/call -Florian Frank <flori@ping.de> +In the table above 1 is JSON::Ext::Parser, 2 is YAML.load with YAML +compatbile JSON document, 3 is is JSON::Pure::Parser, and 4 is +ActiveSupport::JSON.decode. The ActiveSupport JSON-decoder converts the +input first to YAML and then uses the YAML-parser, the conversion seems to +slow it down so much that it is only as fast as the JSON::Pure::Parser! -License -======= +If you look at the benchmark data you can see that this is mostly caused by +the frequent high outliers - the median of the Rails-parser runs is still +overall smaller than the median of the JSON::Pure::Parser runs: + + Comparing times (call_time_median): + 1 ParserBenchmarkExt#parser 900 repeats: + 800.592479481 ( real) -> 26.936x + 0.001249075 + 2 ParserBenchmarkYAML#parser 1000 repeats: + 271.002390644 ( real) -> 9.118x + 0.003690004 + 3 ParserBenchmarkRails#parser 1000 repeats: + 30.227910865 ( real) -> 1.017x + 0.033082008 + 4 ParserBenchmarkPure#parser 1000 repeats: + 29.722384421 ( real) -> 1.000x + 0.033644676 + calls/sec ( time) -> speed covers + secs/call + +I have benchmarked the JSON-Generator as well. This generated a few more +values, because there are different modes that also influence the achieved +speed: + + Comparing times (call_time_mean): + 1 GeneratorBenchmarkExt#generator_fast 1000 repeats: + 547.354332608 ( real) -> 15.090x + 0.001826970 + 2 GeneratorBenchmarkExt#generator_safe 1000 repeats: + 443.968212317 ( real) -> 12.240x + 0.002252414 + 3 GeneratorBenchmarkExt#generator_pretty 900 repeats: + 375.104545883 ( real) -> 10.341x + 0.002665923 + 4 GeneratorBenchmarkPure#generator_fast 1000 repeats: + 49.978706968 ( real) -> 1.378x + 0.020008521 + 5 GeneratorBenchmarkRails#generator 1000 repeats: + 38.531868759 ( real) -> 1.062x + 0.025952543 + 6 GeneratorBenchmarkPure#generator_safe 1000 repeats: + 36.927649925 ( real) -> 1.018x 7 (>=3859) + 0.027079979 + 7 GeneratorBenchmarkPure#generator_pretty 1000 repeats: + 36.272134441 ( real) -> 1.000x 6 (>=3859) + 0.027569373 + calls/sec ( time) -> speed covers + secs/call + +In the table above 1-3 are JSON::Ext::Generator methods. 4, 6, and 7 are +JSON::Pure::Generator methods and 5 is the Rails JSON generator. It is now a +bit faster than the generator_safe and generator_pretty methods of the pure +variant but slower than the others. + +To achieve the fastest JSON document output, you can use the fast_generate +method. Beware, that this will disable the checking for circular Ruby data +structures, which may cause JSON to go into an infinite loop. + +Here are the median comparisons for completeness' sake: + + Comparing times (call_time_median): + 1 GeneratorBenchmarkExt#generator_fast 1000 repeats: + 708.258020939 ( real) -> 16.547x + 0.001411915 + 2 GeneratorBenchmarkExt#generator_safe 1000 repeats: + 569.105020353 ( real) -> 13.296x + 0.001757145 + 3 GeneratorBenchmarkExt#generator_pretty 900 repeats: + 482.825371244 ( real) -> 11.280x + 0.002071142 + 4 GeneratorBenchmarkPure#generator_fast 1000 repeats: + 62.717626652 ( real) -> 1.465x + 0.015944481 + 5 GeneratorBenchmarkRails#generator 1000 repeats: + 43.965681162 ( real) -> 1.027x + 0.022745013 + 6 GeneratorBenchmarkPure#generator_safe 1000 repeats: + 43.929073409 ( real) -> 1.026x 7 (>=3859) + 0.022763968 + 7 GeneratorBenchmarkPure#generator_pretty 1000 repeats: + 42.802514491 ( real) -> 1.000x 6 (>=3859) + 0.023363113 + calls/sec ( time) -> speed covers + secs/call + +=== Author + +Florian Frank <mailto:flori@ping.de> + +=== License Ruby License, see the COPYING file included in the source distribution. The Ruby License includes the GNU General Public License (GPL), Version 2, so see the file GPL as well. + +=== Download + +The latest version of this library can be downloaded at + +* http://rubyforge.org/frs?group_id=953 + +Online Documentation should be located at + +* http://json.rubyforge.org |