class FFI::Generator

Generate files with C structs for FFI::Struct and C constants.

A simple example¶ ↑

In file zlib.rb.ffi:

module Zlib
  @@@
  constants do |c|
    c.include "zlib.h"
    c.const :ZLIB_VERNUM
  end
  @@@

  class ZStream < FFI::Struct

    struct do |s|
      s.name "struct z_stream_s"
      s.include "zlib.h"

      s.field :next_in,   :pointer
      s.field :avail_in,  :uint
      s.field :total_in,  :ulong
    end
    @@@
  end
end

Translate the file:

require "ffi/tools/generator"
FFI::Generator.new "zlib.rb.ffi", "zlib.rb"

Generates the file zlib.rb with constant values and offsets:

module Zlib
ZLIB_VERNUM = 4784

class ZStream < FFI::Struct
  layout :next_in, :pointer, 0,
         :avail_in, :uint, 8,
         :total_in, :ulong, 16
end

@see FFI::Generator::Task for easy integration in a Rakefile

Public Class Methods

new (ffi_name, rb_name, options = {})

# File lib/ffi/tools/generator.rb, line 51
def initialize(ffi_name, rb_name, options = {})
  @ffi_name = ffi_name
  @rb_name = rb_name
  @options = options
  @name = File.basename rb_name, '.rb'

  file = File.read @ffi_name

  new_file = file.gsub(/^( *)@@@(.*?)@@@/m) do
    @constants = []
    @structs = []

    indent = $1
    original_lines = $2.count "\n"

    instance_eval $2, @ffi_name, $`.count("\n")

    new_lines = []
    @constants.each { |c| new_lines << c.to_ruby }
    @structs.each { |s| new_lines << s.generate_layout }

    new_lines = new_lines.join("\n").split "\n" # expand multiline blocks
    new_lines = new_lines.map { |line| indent + line }

    padding = original_lines - new_lines.length
    new_lines += [nil] * padding if padding >= 0

    new_lines.join "\n"
  end

  open @rb_name, 'w' do |f|
    f.puts "# This file is generated from `#{@ffi_name}'. Do not edit."
    f.puts
    f.puts new_file
  end
end

Public Instance Methods

constants (options = {}, &block)

# File lib/ffi/tools/generator.rb, line 88
def constants(options = {}, &block)
  @constants << FFI::ConstGenerator.new(@name, @options.merge(options), &block)
end

struct (options = {}, &block)

# File lib/ffi/tools/generator.rb, line 92
def struct(options = {}, &block)
  @structs << FFI::StructGenerator.new(@name, @options.merge(options), &block)
end

to_s ()

Utility converter for constants

# File lib/ffi/tools/generator.rb, line 99
def to_s
  proc { |obj| obj.to_s.inspect }
end