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https://github.com/olbat/libgen

Automatic C-bindings generator for the Crystal language
https://github.com/olbat/libgen

binding-generator code-generation crystal

Last synced: 2 months ago
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Automatic C-bindings generator for the Crystal language

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# Crystal lib generator



Libgen is a small tool based on the [crystal_lib](https://github.com/crystal-lang/crystal_lib) project that allows to generate [libs](https://crystal-lang.org/docs/syntax_and_semantics/c_bindings/lib.html) following rules specified in config files.



## Overview

This project aims to ease the port of big C libraries and to provide a convinient way to define re-generable bindings.  

Lib generation is parametrized using a YAML or JSON configuration file (_how to generate_).  

Bindings definitions are specified in YAML, JSON or Crystal files or in the generation config file directly (_what to generate_).  

It's possible to split lib's definitions in several files in order to make the binding more readable/easy to maintain.  

There is also an option to perform AST node renaming at generation time.



## Installation

__Debian/Ubuntu__

```bash

# install build dependencies

apt-get install -y build-essential llvm-7-dev libclang-7-dev

# then, build and install

make && make install

```



__macOS__

```bash

# if necessary, install build dependencies

brew install llvm@7

# then, build and install

make && make install

```



## Usage

```bash

usage: libgen []

```



## Example

A generation config file, [examples/icu/lib.yml](https://github.com/olbat/libgen/blob/master/examples/icu/lib.yml):

```yaml

name: LibICU

cflags: "-DU_COMMON_IMPLEMENTATION"

ldflags: "-licuuc -licudata -licui18n -licuio"

packages: icu-uc icu-i18n icu-io

destdir: src/lib_icu/

includes:

- include/*.yml

- include/*.json

- include/*.cr

definitions:

  ubrk:

    description: Text Boundary Analysis (Break Iteration)

    includes: [ unicode/ubrk.h ]

    prefixes: [ ubrk_ ]

rename:

  rules:

    "*":

    - pattern: _\d+$

      replacement: ""

options:

  import_docstrings: brief

```



A definition file, [examples/icu/include/ucsdet.yml](https://github.com/olbat/libgen/blob/master/examples/icu/include/ucsdet.yml):

```yaml

description: Charset detection

includes:

- unicode/ucsdet.h

prefixes:

- ucsdet_

```



Generation of the lib:

```bash

$ libgen examples/icu/lib.yml

loading library from examples/icu/lib.yml

moving to examples/icu/

loading ubrk definition from lib.yml

loading lib_icu definition from include/lib_icu.yml

loading ucsdet definition from include/ucsdet.yml

loading ucurr definition from include/ucurr.json

loading udat definition from include/udat.cr

generate src/lib_icu/ubrk.cr

generate src/lib_icu/lib_icu.cr

generate src/lib_icu/ucsdet.cr

generate src/lib_icu/ucurr.cr

generate src/lib_icu/udat.cr



# or, using docker-compose

$ docker-compose run --rm -u $UID libgen examples/icu/lib.yml

```



The generated files: [examples/icu/src/lib_icu](https://github.com/olbat/libgen/blob/master/examples/icu/src/lib_icu).



## Specifications



See [SPECS.md](https://github.com/olbat/libgen/blob/master/SPECS.md)



## Development

__How does it work__



To generate Crystal libs from C headers, the `libgen` tool:

1. loads [Library](https://github.com/olbat/libgen/blob/master/src/lib_generator/library.cr) and [Definition](https://github.com/olbat/libgen/blob/master/src/lib_generator/definition.cr) objects from configuration files

2. generates Crystal ASTs (one per Definition) from C headers using [crystal_lib](https://github.com/olbat/libgen/blob/master/https://github.com/crystal-lang/crystal_lib)'s parser (see [Definition#parse_lib](https://github.com/olbat/libgen/blob/master/src/lib_generator/definition.cr))

3. transforms the Crystal ASTs:

    1. applies transformers following the configuration (AST nodes renaming, sorting, ... see [transformers](https://github.com/olbat/libgen/blob/master/src/lib_generator/transformers))

    2. groups AST nodes that are common to several libs into a common lib

    3. adds requires to non-empty libs in the common lib's AST

4. generates and formats the libs from ASTs adding the _@Link/ldflags_ attribute (see [Generator::Lib#generate](https://github.com/olbat/libgen/blob/master/src/lib_generator/generator/lib.cr))

5. saves the generated libs to their respective output files



__Known limitations__

* it's only possible to filter functions to bind by prefix (and not by name, such as in [example](https://github.com/crystal-lang/crystal_lib/blob/master/examples/lib_readline.cr))

* it's not possible to specify the `description` field in definitions written in Crystal

* the `description` field specified in definitions is not used ATM (it should be added as a comment in the generated bindings)



__LLVM versions__



Libgen is [tested](.travis.yml) using the versions of LLVM that are [currently supported](https://crystal-lang.org/docs/installation/from_source_repository.html) by Crystal: LLVM `3.8`→`6.0`.



The tool is not dependent on this versions of LLVM, it may be working with other versions as well but it's not tested/guaranteed.



__Launch the tests__

```

make test



# or, using docker-compose

docker-compose run --rm -u $UID devel make test

```



__Build the Docker image__

```bash

make

docker build .

```



## Projects using libgen

- [icu.cr](https://github.com/olbat/icu.cr)

- [nacl](https://github.com/watzon/nacl)



__Note__: you are using _libgen_ in your project and want to link it here, please [submit a PR](contributing)



## Contributing

1. Fork it ( https://github.com/olbat/libgen/fork )

2. Create your feature branch (git checkout -b my-new-feature)

3. Commit your changes (git commit -am 'Add some feature')

4. Push to the branch (git push origin my-new-feature)

5. Create a new Pull Request



## Contributors

- [olbat](https://github.com/olbat) - creator, maintainer