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mrbgems

mrbgems is a library manager to integrate C and Ruby extension in an easy and standardised way into mruby.

Usage

By default mrbgems is currently deactivated. As soon as you add a GEM to your build configuration (i.e. build_config.rb), mrbgems will be activated and the extension integrated.

To add a GEM into the build_config.rb add the following line for example:

conf.gem '/path/to/your/gem/dir'

You can also use a relative path which would be relative from the mruby root:

conf.gem 'examples/mrbgems/ruby_extension_example'

A remote GIT repository location for a GEM is also supported:

conf.gem :git => 'https://github.com/masuidrive/mrbgems-example.git', :branch => 'master'

conf.gem :github => 'masuidrive/mrbgems-example', :branch => 'master'

conf.gem :bitbucket => 'mruby/mrbgems-example', :branch => 'master'

NOTE: :bitbucket option supports only git. Hg is unsupported in this version.

GemBox

There are instances when you wish to add a collection of gems into mruby at once, or be able to substitute gems based on configuration, without having to add each gem to the build_config.rb file. A packaged collection of mrbgems is called a GemBox. A GemBox is a file that contains a list of gems to load into mruby, in the same format as if you were adding them to build_config.rb via config.gem, but wrapped in an MRuby::GemBox object. GemBoxes are loaded into mruby via config.gembox 'boxname'.

Below we have created a GemBox containing mruby-time and mrbgems-example:

MRuby::GemBox.new do |conf|
  conf.gem "#{root}/mrbgems/mruby-time"
  conf.gem :github => 'masuidrive/mrbgems-example'
end

As mentioned, the GemBox uses the same conventions as MRuby::Build. The GemBox must be saved with a .gembox extension inside the mrbgems directory to to be picked up by mruby.

To use this example GemBox, we save it as custom.gembox inside the mrbgems directory in mruby, and add the following to our build_config.rb file inside the build block:

conf.gembox 'custom'

This will cause the custom GemBox to be read in during the build process, adding mruby-time and mrbgems-example to the build.

There are two GemBoxes that ship with mruby: default and full-core. The default GemBox contains several core components of mruby, and full-core contains every gem found in the mrbgems directory.

GEM Structure

The maximal GEM structure looks like this:

+- GEM_NAME         <- Name of GEM
   |
   +- mrblib/       <- Source for Ruby extension
   |
   +- src/          <- Source for C extension
   |
   +- test/         <- Test code (Ruby)
   |
   +- mrbgem.rake   <- GEM Specification
   |
   +- README.md     <- Readme for GEM

The folder mrblib contains pure Ruby files to extend mruby. The folder src contains C files to extend mruby. The folder test contains C and pure Ruby files for testing purposes which will be used by mrbtest. mrbgem.rake contains the specification to compile C and Ruby files. README.md is a short description of your GEM.

Build process

mrbgems expects a specifcation file called mrbgem.rake inside of your GEM direcotry. A typical GEM specification could look like this for example:

MRuby::Gem::Specification.new('c_and_ruby_extension_example') do |spec|
  spec.license = 'MIT'
  spec.authors = 'mruby developers'
end

The mrbgems build process will use this specification to compile Object and Ruby files. The compilation results will be add to lib/libmruby.a. This file is used by tools like mruby and mirb to empower the GEM functionality.

The following properties can be set inside of your MRuby::Gem::Specification for information purpose:

  • spec.license or spec.licenses (A single license or a list of them under which this GEM is licensed)
  • spec.author or spec.authors (Developer name or a list of them)
  • spec.version (Current version)
  • spec.description (Detailed description)
  • spec.summary (Short summary)
  • spec.homepage (Homepage)
  • spec.requirements (External requirements as information for user)

It is required for every GEM to have a license and an author!

In case your GEM is depending on other GEMs please use spec.add_dependency(gem, *requirements) like:

MRuby::Gem::Specification.new('c_and_ruby_extension_example') do |spec|
  spec.license = 'MIT'
  spec.authors = 'mruby developers'

  # add GEM dependency mruby-parser.
  # Version has to be between 1.0.0 and 1.5.2
  spec.add_dependency('mruby-parser', '> 1.0.0', '< 1.5.2')
end

The usage of versions is optional.

ATTENTION: The dependency system is currently (May 2013) under development and doesn't check or resolve dependencies!

In case your GEM has more complex build requirements you can use the following options additionally inside of your GEM specification:

  • spec.cflags (C compiler flags)
  • spec.mruby_cflags (global C compiler flags for everything)
  • spec.mruby_ldflags (global linker flags for everything)
  • spec.mruby_libs (global libraries for everything)
  • spec.mruby_includes (global includes for everything)
  • spec.rbfiles (Ruby files to compile)
  • spec.objs (Object files to compile)
  • spec.test_rbfiles (Ruby test files for integration into mrbtest)
  • spec.test_objs (Object test files for integration into mrbtest)
  • spec.test_preload (Initialization files for mrbtest)

C Extension

mruby can be extended with C. This is possible by using the C API to integrate C libraries into mruby.

Pre-Conditions

mrbgems expects that you have implemented a C method called mrb_YOURGEMNAME_gem_init(mrb_state). YOURGEMNAME will be replaced by the name of your GEM. If you call your GEM c_extension_example, your initialisation method could look like this:

void
mrb_c_extension_example_gem_init(mrb_state* mrb) {
  struct RClass *class_cextension = mrb_define_module(mrb, "CExtension");
  mrb_define_class_method(mrb, class_cextension, "c_method", mrb_c_method, MRB_ARGS_NONE());
}

Finalize

mrbgems expects that you have implemented a C method called mrb_YOURGEMNAME_gem_final(mrb_state). YOURGEMNAME will be replaced by the name of your GEM. If you call your GEM c_extension_example, your finalizer method could look like this:

void
mrb_c_extension_example_gem_final(mrb_state* mrb) {
  free(someone);
}

Example

+- c_extension_example/
   |
   +- src/
   |  |
   |  +- example.c         <- C extension source
   |
   +- test/
   |  |
   |  +- example.rb        <- Test code for C extension
   |
   +- mrbgem.rake          <- GEM specification
   |
   +- README.md

Ruby Extension

mruby can be extended with pure Ruby. It is possible to override existing classes or add new ones in this way. Put all Ruby files into the mrblib folder.

Pre-Conditions

none

Example

+- ruby_extension_example/
   |
   +- mrblib/
   |  |
   |  +- example.rb        <- Ruby extension source
   |
   +- test/
   |  |
   |  +- example.rb        <- Test code for Ruby extension
   |
   +- mrbgem.rake          <- GEM specification
   |
   +- README.md

C and Ruby Extension

mruby can be extended with C and Ruby at the same time. It is possible to override existing classes or add new ones in this way. Put all Ruby files into the mrblib folder and all C files into the src folder.

Pre-Conditions

See C and Ruby example.

Example

+- c_and_ruby_extension_example/
   |
   +- mrblib/
   |  |
   |  +- example.rb        <- Ruby extension source
   |
   +- src/
   |  |
   |  +- example.c         <- C extension source
   |
   +- test/
   |  |
   |  +- example.rb        <- Test code for C and Ruby extension
   |
   +- mrbgem.rake          <- GEM specification
   |
   +- README.md
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