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mrbgems

mrbgems is a library manager to integrate C and Ruby extensions in an easy and standardised way into mruby. Conventionally, each mrbgem name is prefixed by mruby-, e.g. mruby-time for a gem that provides Time class functionality.

Usage

You have to activate mrbgems explicitly in your build configuration. To add a gem, add the following line to your build configuration file, for example:

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

You can also use a relative path to specify a gem.

conf.gem 'examples/mrbgems/ruby_extension_example'

In that case,

  • if your build configuration file is in the build_config directory, it's relative from MRUBY_ROOT.
  • otherwise, it is relative from the directory where your build configuration is.

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.

You can specify the subdirectory of the repository with :path option:

conf.gem github: 'mruby/mruby', path: 'mrbgems/mruby-socket'

To use mrbgem from mgem-list use :mgem option:

conf.gem :mgem => 'mruby-yaml'
conf.gem :mgem => 'yaml' # 'mruby-' prefix could be omitted

For specifying the commit hash to checkout use :checksum_hash option:

conf.gem mgem: 'mruby-redis', checksum_hash: '3446d19fc4a3f9697b5ddbf2a904f301c42f2f4e'

If there are missing dependencies, mrbgem dependencies solver will reference mrbgem from the core or mgem-list.

Note that if more than one git-based gem has the same base name (i.e. the default checkout directory name), it is (now) an error UNLESS they have the same repository URL, branch name and commit-id (i.e. checksum hash). You can bypass this by explicitly importing your preferred version first and setting the canonical: option to true:

conf.gem github: 'me/mruby-yaml', branch: 'my-hacked-branch', canonical: true

If you do this, the system will (mostly) silently ignore other attempts to clone a gem with this name.

Note that this only affects cloning the gem from git. It does not resolve version conflicts. If the version as specified in the gem's rakefile is incompatible with a dependency, your build will still fail.

Tweak the gem in your build configuration file

You can give blocks in the conf.gem call to make adjustments for environments where the original gem does not expect them:

conf.gem core: "mruby-bin-mirb" do |g|
  # For cross build to NetBSD
  g.linker.libraries = %w(edit termcap)
end

However, it should be used with caution, as it may deviate from the intent of the gem's author.

Gem Testing

If you enable unit tests in your build with enable_test, tests will be generated for all gems and their dependencies by default. If necessary, it is possible to suppress tests for a specific gem like so:

conf.gem 'mruby-noisygem' do |g|
  g.skip_test = true
end

However, it is considered best practice to leave all tests enabled whenever possible. A warning message will be generated for each gem with disabled tests.

GemBox

There are instances when you wish to add a collection of mrbgems into mruby at once, or be able to substitute mrbgems based on configuration, without having to add each gem to your build configuration file. A packaged collection of mrbgems is called a GemBox. A GemBox is a file that contains a list of mrbgems to load into mruby, in the same format as if you were adding them to the build config 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 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 your build configuration 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.

If you want, you can put GemBox outside the mruby directory. In that case you must specify an absolute path like below.

conf.gembox "#{ENV["HOME"]}/mygemboxes/custom"

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
    |
    +- README.md        <- Readme for GEM
    |
    +- mrbgem.rake      <- GEM Specification
    |
    +- include/         <- Header for Ruby extension (will exported)
    |
    +- mrblib/          <- Source for Ruby extension
    |
    +- src/             <- Source for C extension
    |
    +- tools/           <- Source for Executable (in C)
    |
    +- test/            <- Test code (Ruby)

The mrblib directory contains pure Ruby files to extend mruby. The src directory contains C/C++ files to extend mruby. The include directory contains C/C++ header files. The test directory contains C/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 specification file called mrbgem.rake inside of your GEM directory. 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.author  = 'mruby developers'
  spec.summary = 'Example mrbgem using C and Ruby'
end

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

The following properties can be set inside 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
    • One line short description of mrbgem.
    • Printed in build summary of rake when set.
  • spec.homepage (Homepage)
  • spec.requirements (External requirements as information for user)

The license and author properties are required in every GEM!

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

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

  # Add GEM dependency mruby-parser.
  # The version must be between 1.0.0 and 1.5.2 .
  spec.add_dependency('mruby-parser', '>= 1.0.0', '<= 1.5.2')

  # Use any version of mruby-uv from GitHub.
  spec.add_dependency('mruby-uv', '>= 0.0.0', :github => 'mattn/mruby-uv')

  # Use latest mruby-onig-regexp from GitHub. (version requirements can be omitted)
  spec.add_dependency('mruby-onig-regexp', :github => 'mattn/mruby-onig-regexp')

  # You can add extra mgems active only on test
  spec.add_test_dependency('mruby-process', :github => 'iij/mruby-process')
end

The version requirements and default gem information are optional.

Version requirement supports following operators:

  • '=': is equal
  • '!=': is not equal
  • '>': is greater
  • '<': is lesser
  • '>=': is equal or greater
  • '<=': is equal or lesser
  • '~>': is equal or greater and is lesser than the next major version
    • example 1: '~> 2.2.2' means '>= 2.2.2' and '< 2.3.0'
    • example 2: '~> 2.2' means '>= 2.2.0' and '< 3.0.0'

When more than one version requirements is passed, the dependency must satisfy all of it.

You can have default gem to use as dependency when it's not defined in your build configuration. When the last argument of add_dependency call is Hash, it will be treated as default gem information. Its format is same as argument of method MRuby::Build#gem, expect that it can't be treated as path gem location.

When a special version of dependency is required, use MRuby::Build#gem in the build configuration to override default gem.

If you have conflicting GEMs use the following method:

  • spec.add_conflict(gem, *requirements)
    • The requirements argument is same as in add_dependency method.

like following code:

MRuby::Gem::Specification.new 'some-regexp-binding' do |spec|
  spec.license = 'BSD'
  spec.author = 'John Doe'

  spec.add_conflict 'mruby-onig-regexp', '> 0.0.0'
  spec.add_conflict 'mruby-hs-regexp'
  spec.add_conflict 'mruby-pcre-regexp'
  spec.add_conflict 'mruby-regexp-pcre'
end

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

  • spec.cc.flags (C compiler flags)
  • spec.cc.defines (C compiler defines)
  • spec.cc.include_paths (C compiler include paths)
  • spec.linker.flags (Linker flags)
  • spec.linker.libraries (Linker libraries)
  • spec.linker.library_paths (Linker additional library path)
  • spec.bins (Generate binary file)
  • 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)

You also can use spec.mruby.cc and spec.mruby.linker to add extra global parameters for the compiler and linker.

include_paths and dependency

Your GEM can export include paths to another GEMs that depends on your GEM. By default, /...absolute path.../{GEM_NAME}/include will be exported. So it is recommended not to put GEM's local header files on include/.

These exports are retroactive. For example: when B depends on C and A depends on B, A will get include paths exported by C.

Exported include_paths are automatically appended to GEM local include_paths by rake. You can use spec.export_include_paths accessor if you want more complex build.

C Extension

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

Preconditions

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

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 directory.

Pre-Conditions

none

Example

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

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 directory and all C files into the src directory.

mruby codes under mrblib directory would be executed after gem init C function is called. Make sure mruby script depends on C code and C code doesn't depend on mruby script.

Pre-Conditions

See C and Ruby example.

Example

+- c_and_ruby_extension_example/
    |
    +- README.md        (Optional)
    |
    +- 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

Binary gems

Some gems can generate executables under bin directory. Those gems are called binary gems. Names of binary gems are conventionally prefixed by mruby-bin, e.g. mruby-bin-mirb and mruby-bin-strip.

To specify the name of executable, you need to specify spec.bins in the mrbgem.rake. The entry point main() should be in the C source file under tools/<bin>/*.c where <bin> is a name of the executable. C files under the <bin> directory are compiled and linked to the executable, but not included in libmruby.a, whereas files under mrblib and src are.

It is strongly recommended not to include mrblib and src directories in the binary gems, to separate normal gems and binary gems.

Example

+- mruby-bin-example/
    |
    +- README.md          (Optional)
    |
    +- bintest/
    |   |
    |   +- example.rb     <- Test code for binary gem
    |
    +- mrbgem.rake        <- Gem specification
    |
    +- mrblib/            <- Source for Ruby extension (Optional)
    |
    +- src/               <- Source for C extension (Optional)
    |
    +- tools/
        |
        +- example/       <- Executable name directory
            |
            +- example.c  <- Source for Executable (includes main)