JezK
Edit File: const_generator.rb
require 'tempfile' require 'open3' module FFI # ConstGenerator turns C constants into ruby values. # # @example a simple example for stdio # require 'ffi/tools/const_generator' # cg = FFI::ConstGenerator.new('stdio') do |gen| # gen.const(:SEEK_SET) # gen.const('SEEK_CUR') # gen.const('seek_end') # this constant does not exist # end # #calculate called automatically at the end of the block # # cg['SEEK_SET'] # => 0 # cg['SEEK_CUR'] # => 1 # cg['seek_end'] # => nil # cg.to_ruby # => "SEEK_SET = 0\nSEEK_CUR = 1\n# seek_end not available" class ConstGenerator @options = {} attr_reader :constants # 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. # # @param [#to_s] prefix # @param [Hash] options # @return # @option options [Boolean] :required # @overload initialize(prefix, options) # @overload initialize(prefix, options) { |gen| ... } # @yieldparam [ConstGenerator] gen new generator is passed to the block # When passed a block, {#calculate} is automatically called at the end of # the block, otherwise you must call it yourself. def initialize(prefix = nil, options = {}) @includes = ['stdio.h', 'stddef.h'] @constants = {} @prefix = prefix @required = options[:required] @options = options if block_given? then yield self calculate self.class.options.merge(options) end end # Set class options # These options are merged with {#initialize} options when it is called with a block. # @param [Hash] options # @return [Hash] class options def self.options=(options) @options = options end # Get class options. # @return [Hash] class options def self.options @options end # @param [String] name # @return constant value (converted if a +converter+ was defined). # Access a constant by name. def [](name) @constants[name].converted_value end # Request the value for C constant +name+. # # @param [#to_s] name C constant name # @param [String] format a printf format string to print the value out # @param [String] cast a C cast for the value # @param ruby_name alternate ruby name for {#to_ruby} # # @overload const(name, format=nil, cast='', ruby_name=nil, converter=nil) # +converter+ is a Method or a Proc. # @param [#call] converter convert the value from a string to the appropriate # type for {#to_ruby}. # @overload const(name, format=nil, cast='', ruby_name=nil) { |value| ... } # Use a converter block. This block convert the value from a string to the # appropriate type for {#to_ruby}. # @yieldparam value constant value 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 # Calculate constants values. # @param [Hash] options # @option options [String] :cppflags flags for C compiler # @return [nil] # @raise if a constant is missing and +:required+ was set to +true+ (see {#initialize}) 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 # Dump constants to +io+. # @param [#puts] io # @return [nil] def dump_constants(io) @constants.each do |name, constant| name = [@prefix, name].join '.' if @prefix io.puts "#{name} = #{constant.converted_value}" end end # Outputs values for discovered constants. If the constant's value was # not discovered it is not omitted. # @return [String] 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 # Add additional C include file(s) to calculate constants from. # @note +stdio.h+ and +stddef.h+ automatically included # @param [List<String>, Array<String>] i include file(s) # @return [Array<String>] array of include files def include(*i) @includes |= i.flatten end end # This class hold constants for {ConstGenerator} class ConstGenerator::Constant attr_reader :name, :format, :cast attr_accessor :value # @param [#to_s] name # @param [String] format a printf format string to print the value out # @param [String] cast a C cast for the value # @param ruby_name alternate ruby name for {#to_ruby} # @param [#call] converter convert the value from a string to the appropriate # type for {#to_ruby}. def initialize(name, format, cast, ruby_name = nil, converter=nil) @name = name @format = format @cast = cast @ruby_name = ruby_name @converter = converter @value = nil end # Return constant value (converted if a +converter+ was defined). # @return constant value. def converted_value if @converter @converter.call(@value) else @value end end # get constant ruby name # @return [String] def ruby_name @ruby_name || @name end # Get an evaluable string from constant. # @return [String] def to_ruby "#{ruby_name} = #{converted_value}" end end end