Object
ConstGenerator turns C constants into ruby values.
@example a simple example for stdio
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"
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.
# File lib/ffi/tools/const_generator.rb, line 38 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
@param [String] name @return constant value (converted if a converter was defined). Access a constant by name.
# File lib/ffi/tools/const_generator.rb, line 66 def [](name) @constants[name].converted_value 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})
# File lib/ffi/tools/const_generator.rb, line 106 def calculate(options = {}) binary = File.join Dir.tmpdir, "rb_const_gen_bin_#{Process.pid}" Tempfile.open("#{@prefix}.const_generator") do |f| @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 #ifdef #{const.name} printf("#{const.name} #{const.format}\\n", #{const.cast}#{const.name}); #endif end f.puts "\n\treturn 0;\n}" f.flush output = `gcc #{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 $?.success? then output = output.split("\n").map { |l| "\t#{l}" }.join "\n" raise "Compilation error generating constants #{@prefix}:\n#{output}" end end output = `#{binary}` File.unlink(binary + (FFI::Platform.windows? ? ".exe" : "")) output.each_line do |line| line =~ /^(\S+)\s(.*)$/ 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
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
# File lib/ffi/tools/const_generator.rb, line 85 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 to io. @param [puts] io @return [nil]
# File lib/ffi/tools/const_generator.rb, line 154 def dump_constants(io) @constants.each do |name, constant| name = [@prefix, name].join '.' if @prefix io.puts "#{name} = #{constant.converted_value}" end 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
# File lib/ffi/tools/const_generator.rb, line 178 def include(*i) @includes |= i.flatten end
Outputs values for discovered constants. If the constant's value was not discovered it is not omitted. @return [String]
# File lib/ffi/tools/const_generator.rb, line 164 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
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