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diff --git a/README.md b/README.md new file mode 100644 index 0000000..7fc6c14 --- /dev/null +++ b/README.md @@ -0,0 +1,345 @@ +# JSON implementation for Ruby {<img src="https://secure.travis-ci.org/flori/json.png" />}[http://travis-ci.org/flori/json] + +## Description + +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: + +* 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 native extension variant, which is in parts + implemented in C or Java and comes with its own unicode conversion + functions and a parser generated by the ragel state machine compiler + http://www.complang.org/ragel/ . + +Both variants of the JSON generator generate UTF-8 character sequences by +default. If an :ascii\_only option with a true value is given, they 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. + +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. + +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 + +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 + +The above command will build the extensions and install them on your system. + + # rake install_pure + +or + + # ruby install.rb + +will just install the pure ruby implementation of JSON. + +If you use Rubygems you can type + + # 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 + +## Compiling the extensions yourself + +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.complang.org/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: + + JSON JSON(1..10) # => 1..10 + +To find out how to add JSON support to other or your own classes, read the +section "More Examples" below. + +To get the best compatibility to rails' JSON implementation, you can + require 'json/add/rails' + +Both of the additions attempt to require 'json' (like above) first, if it has +not been required yet. + +## More Examples + +To create a JSON document from a ruby data structure, you can call +JSON.generate like that: + + 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. + +## 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 + +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! + +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 https://www.ruby-lang.org/en/about/license.txt. + +## Download + +The latest version of this library can be downloaded at + +* https://rubygems.org/gems/json + +Online Documentation should be located at + +* http://json.rubyforge.org |