def calculate(options = {})
binary = File.join Dir.tmpdir, "rb_struct_gen_bin_#{Process.pid}"
raise "struct name not set" if @struct_name.nil?
Tempfile.open("#{@name}.struct_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{"
f.puts " #{@struct_name} s;"
f.puts %[ printf("sizeof(#{@struct_name}) %u\\n", (unsigned int) sizeof(#{@struct_name}));]
@fields.each do |field|
f.puts "printf(\"\#{field.name} %u %u\\\\n\", (unsigned int) offsetof(\#{@struct_name}, \#{field.name}),\n(unsigned int) sizeof(s.\#{field.name}));\n"
end
f.puts "\n return 0;\n}"
f.flush
output = `gcc #{options[:cppflags]} #{options[:cflags]} -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
@found = false
output = output.split("\n").map { |l| "\t#{l}" }.join "\n"
raise "Compilation error generating struct #{@name} (#{@struct_name}):\n#{output}"
end
end
output = `#{binary}`.split "\n"
File.unlink(binary + (FFI::Platform.windows? ? ".exe" : ""))
sizeof = output.shift
unless @size
m = /\s*sizeof\([^)]+\) (\d+)/.match sizeof
@size = m[1]
end
line_no = 0
output.each do |line|
md = line.match(/.+ (\d+) (\d+)/)
@fields[line_no].offset = md[1].to_i
@fields[line_no].size = md[2].to_i
line_no += 1
end
@found = true
end