Method: FFI::ConstGenerator#calculate

Defined in:
lib/ffi/tools/const_generator.rb

#calculate(options = {}) ⇒ nil

Calculate constants values.

Parameters:

  • options (Hash) (defaults to: {})

Options Hash (options):

  • :cppflags (String) —

    flags for C compiler

Returns:

  • (nil)

Raises:

  • if a constant is missing and :required was set to true (see #initialize)



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# File 'lib/ffi/tools/const_generator.rb', line 107

def calculate(options = {})
  binary_path = nil

  Tempfile.open("#{@prefix}.const_generator") do |f|
    binary_path = f.path + ".bin"
    @includes.each do |inc|
      f.puts "#include <#{inc}>"
    end
    f.puts "\nint main(int argc, char **argv)\n{"

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

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

    cc = ENV['CC'] || 'gcc'
    output = `#{cc} #{options[:cppflags]} -D_DARWIN_USE_64_BIT_INODE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -x c -Wall -Werror #{f.path} -o #{binary_path} 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 = `#{binary_path}`
  File.unlink(binary_path + (FFI::Platform.windows? ? ".exe" : ""))
  output.each_line do |line|
    line =~ /^(\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