class FFI::ConstGenerator

ConstGenerator turns C constants into ruby values.

Attributes

constants[R]

Public Class Methods

new(prefix = nil, options = {}) { |self| ... } click to toggle source

Creates a new constant generator that uses prefix as a name, and an options hash.

The only option is :required, which if set to true raises an error if a constant you have requested was not found.

When passed a block, calculate is automatically called at the end of the block, otherwise you must call it yourself.

# File lib/ffi/tools/const_generator.rb, line 23
def initialize(prefix = nil, options = {})
  @includes = []
  @constants = {}
  @prefix = prefix

  @required = options[:required]
  @options = options

  if block_given? then
    yield self
    calculate self.class.options.merge(options)
  end
end
options() click to toggle source
# File lib/ffi/tools/const_generator.rb, line 39
def self.options
  @options
end
options=(options) click to toggle source
# File lib/ffi/tools/const_generator.rb, line 36
def self.options=(options)
  @options = options
end

Public Instance Methods

[](name) click to toggle source
# File lib/ffi/tools/const_generator.rb, line 42
def [](name)
  @constants[name].value
end
calculate(options = {}) click to toggle source
# File lib/ffi/tools/const_generator.rb, line 69
    def calculate(options = {})
      binary = File.join Dir.tmpdir, "rb_const_gen_bin_#{Process.pid}"

      Tempfile.open("#{@prefix}.const_generator") do |f|
        f.puts "#include <stdio.h>"

        @includes.each do |inc|
          f.puts "#include <#{inc}>"
        end

        f.puts "#include <stddef.h>\n\n"
        f.puts "int main(int argc, char **argv)\n{"

        @constants.each_value do |const|
          f.puts "  #ifdef #{const.name}
  printf("#{const.name} #{const.format}\\n", #{const.cast}#{const.name});
  #endif
"
        end

        f.puts "\n\treturn 0;\n}"
        f.flush

        output = %xgcc #{options[:cppflags]} -D_DARWIN_USE_64_BIT_INODE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -x c -Wall -Werror #{f.path} -o #{binary} 2>&1`

        unless $?.success? then
          output = output.split("\n").map { |l| "\t#{l}" }.join "\n"
          raise "Compilation error generating constants #{@prefix}:\n#{output}"
        end
      end

      output = %x#{binary}`
      File.unlink(binary + (FFI::Platform.windows? ? ".exe" : ""))
      output.each_line do |line|
        line =~ %r^(\S+)\s(.*)$/
        const = @constants[$1]
        const.value = $2
      end

      missing_constants = @constants.select do |name, constant|
        constant.value.nil?
      end.map { |name,| name }

      if @required and not missing_constants.empty? then
        raise "Missing required constants for #{@prefix}: #{missing_constants.join ', '}"
      end
    end
const(name, format = nil, cast = '', ruby_name = nil, converter = nil, &converter_proc) click to toggle source

Request the value for C constant name. format is a printf format string to print the value out, and cast is a C cast for the value. ruby_name allows you to give the constant an alternate ruby name for to_ruby. converter or converter_proc allow you to convert the value from a string to the appropriate type for to_ruby.

# File lib/ffi/tools/const_generator.rb, line 53
def const(name, format = nil, cast = '', ruby_name = nil, converter = nil,
          &converter_proc)
  format ||= '%d'
  cast ||= ''

  if converter_proc and converter then
    raise ArgumentError, "Supply only converter or converter block"
  end

  converter = converter_proc if converter.nil?

  const = Constant.new name, format, cast, ruby_name, converter
  @constants[name.to_s] = const
  return const
end
dump_constants(io) click to toggle source
# File lib/ffi/tools/const_generator.rb, line 118
def dump_constants(io)
  @constants.each do |name, constant|
    name = [@prefix, name].join '.' if @prefix
    io.puts "#{name} = #{constant.converted_value}"
  end
end
include(i) click to toggle source
# File lib/ffi/tools/const_generator.rb, line 139
def include(i)
  @includes << i
end
to_ruby() click to toggle source

Outputs values for discovered constants. If the constant's value was not discovered it is not omitted.

# File lib/ffi/tools/const_generator.rb, line 129
def to_ruby
  @constants.sort_by { |name,| name }.map do |name, constant|
    if constant.value.nil? then
      "# #{name} not available"
    else
      constant.to_ruby
    end
  end.join "\n"
end