source: EcnlProtoTool/trunk/mruby-2.1.1/doc/guides/mrbgems.md@ 439

# 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:
```ruby
conf.gem '/path/to/your/gem/dir'
```

You can also use a relative path which would be relative from the mruby root:
```ruby
conf.gem 'examples/mrbgems/ruby_extension_example'
```

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

You can specify the sub directory of the repository with `:path` option:
```ruby
conf.gem github: 'mruby/mruby', path: 'mrbgems/mruby-socket'
```

To use mrbgem from [mgem-list](https://github.com/mruby/mgem-list) use `:mgem` option:
```ruby
conf.gem :mgem => 'mruby-yaml'
conf.gem :mgem => 'yaml' # 'mruby-' prefix could be omitted
```

For specifying commit hash to checkout use `:checksum_hash` option:
```ruby
conf.gem mgem: 'mruby-redis', checksum_hash: '3446d19fc4a3f9697b5ddbf2a904f301c42f2f4e'
```

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

To pull all gems from remote GIT repository on build, call ```rake -p```,
or ```rake --pull-gems```.

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

## 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 the *build_config.rb* 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 *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*:
```ruby
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:
```ruby
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 of mruby directory. In that case you must
specify an absolute path like below.
```ruby
conf.gembox "#{ENV["HOME"]}/mygemboxes/custom"
```

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

## GEM Structure

The maximal GEM structure looks like this:

        +- GEM_NAME         <- Name of GEM
           |
           +- include/      <- Header for Ruby extension (will exported)
           |
           +- 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/C++ files to extend mruby. The folder *include* contains C/C++ header
files. The folder *test* 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:
```ruby
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 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`
  * 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:
```ruby
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 *build_config.rb*.
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 *build_config.rb* 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:
```ruby
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 of 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 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 to C and A depends to 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:
```C
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:

```C
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.

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/
           |
           +- 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