JsonScanner
Extract values from JSON without full parsing. This gem uses yajl lib to scan a json string and allows you to parse pieces of it.
Installation
Install the gem and add to the application's Gemfile by executing:
$ bundle add json_scanner
If bundler is not being used to manage dependencies, install the gem by executing:
$ gem install json_scanner
Usage
require "json"
require "json_scanner"
large_json = "[#{"4," * 100_000}42#{",2" * 100_000}]"
where_is_42 = JsonScanner.scan(large_json, [[100_000]], false).first
# => [[200001, 200003, :number]]
where_is_42.map do |begin_pos, end_pos, _type|
JSON.parse(large_json.byteslice(begin_pos...end_pos), quirks_mode: true)
end
# => [42]
emoji_json = '{"grin": "😁", "heart": "😍", "rofl": "🤣"}'
begin_pos, end_pos, = JsonScanner.scan(emoji_json, [["heart"]], false).first.first
emoji_json.byteslice(begin_pos...end_pos)
# => "\"😍\""
# Note: most likely don't need `quirks_mode` option, unless you are using some old ruby
# with stdlib version of json gem or its old version. In new versions `quirks_mode` is default
JSON.parse(emoji_json.byteslice(begin_pos...end_pos), quirks_mode: true)
# => "😍"
# You can also do this
# emoji_json.force_encoding(Encoding::BINARY)[begin_pos...end_pos].force_encoding(Encoding::UTF_8)
# => "\"😍\""Development
After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.
Contributing
Bug reports and pull requests are welcome on GitHub at github.
License
The gem is available as open source under the terms of the MIT License.