https://github.com/cjhdev/contrived_json
A JSON parser implemented using Flex, Bison, and Ruby
https://github.com/cjhdev/contrived_json
bison flex json
Last synced: about 1 month ago
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A JSON parser implemented using Flex, Bison, and Ruby
- Host: GitHub
- URL: https://github.com/cjhdev/contrived_json
- Owner: cjhdev
- License: mit
- Created: 2017-02-19T01:39:10.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2018-11-13T11:25:34.000Z (over 6 years ago)
- Last Synced: 2025-04-05T05:51:09.436Z (2 months ago)
- Topics: bison, flex, json
- Language: C
- Size: 58.6 KB
- Stars: 19
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: readme.md
- License: LICENSE
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README
ContrivedJSON
=============
A Ruby JSON parser implemented using Flex and Bison.
This project is an example of how to use Flex and Bison with Ruby to produce LALR based parsers.
[](https://travis-ci.org/cjhdev/contrived_json)
[](https://badge.fury.io/rb/contrived_json)
## ContrivedJSON Highlights
- Can read from a stream or a string
- Big number support
- Fractions and exponents are captured using `BigDecimal::new`
- Integers are captured using `String#to_i`
- Syntax error reporting with location and token information
- Bulk of implementation within ~200 lines of configuration ([parser.l](etc/contrived_json/ext_parser/parser.l) and [parser.y](etc/contrived_json/ext_parser/parser.y))
- Works on MRI Ruby 1.9.3 and up
## The Interface
ContrivedJSON implements a parse method similar to the standard library
`JSON.parse`. It looks like this:
~~~ ruby
module ContrivedJSON
class JSON
# @param source [String,#readpartial] JSON string or a stream
# @param opts [Hash]
#
# @return [Hash,Array]
#
# @raise [ArgumentError]
# @raise [TypeError]
# @raise [ContrivedJSON::ParseError]
#
def self.parse(source, opts={})
end
end
end
~~~
## Usage
Installing:
~~~
$ gem install contrived_json
~~~
Hello world:
~~~
$ irb
2.3.3 :001 > require 'contrived_json'
=> true
2.3.3 :002 > ContrivedJSON::JSON.parse('{"hello":"world"}')
=> {"hello"=>"world"}
~~~
Syntax error:
~~~
$ irb
2.3.3 :001 > require 'contrived_json'
=> true
2.3.3 :002 > ContrivedJSON::JSON.parse('{"hello":"world"')
1:10: error: syntax error, unexpected EOF, expecting ',' or '}'
ContrivedJSON::ParseError: parse error
from (irb):2:in `parse'
from (irb):2
from /home/cjh/.rvm/rubies/ruby-2.3.3/bin/irb:11:in `'
~~~
## Under The Hood
In this project the lexer is configured in [parser.l](etc/contrived_json/ext_parser/parser.l) and the parser is configured in [parser.y](etc/contrived_json/ext_parser/parser.y).
The rake task `:flexbison` is used by the developer to convert configuration into source:
~~~
task :flexbison do
system "flex --outfile=#{DIR_SRC}/lexer.c --header-file=#{DIR_SRC}/lexer.h #{DIR_ETC}/parser.l"
system "bison -d #{DIR_ETC}/parser.y --output=#{DIR_SRC}/parser.c"
end
~~~
The result is checked into Git:
- [lexer.c](ext/contrived_json/ext_parser/lexer.c)
- [lexer.h](ext/contrived_json/ext_parser/lexer.h)
- [parser.c](ext/contrived_json/ext_parser/parser.c)
- [parser.h](ext/contrived_json/ext_parser/parser.h)
The remainder of the code and structure in the repository is for packaging
up the project as a Gem which will handle compilation of the parser
source on installation.
## Further Reading
- [Bison user manual](https://www.gnu.org/software/bison/manual/)
- The Flex user manual is included with the distribution and can be accessed from the terminal via the command `$ info flex`
- [A Flex/Bison tutorial](http://aquamentus.com/flex_bison.html)
## License
ContrivedJSON has an MIT license