From: Jim Morris <morris@...>
Date: 2005-06-20T06:17:46+09:00
Subject: Ruby/DL struct inspection?

Hi Ruby/DL experts...

I want to print out the values of the members of a DL struct, is there a 
way for the actual instance of the struct to know this?
An example of how I currently do it is below in printStruct, however 
this requires that I have both the instance
and the Class name of the struct, then I use the Struct::members method 
of the class.

However it would be nice if I could get this all from the instance s 
which appears to be type DL::Importable::Internal::Memory and seems to 
have no reference to Svn_status_t which is DL::Importable::Internal::Struct

require 'dl/import'
require 'dl/struct'

module Svnrb
    extend DL::Importable

    Svn_status_t = struct [
        "void *entry",
        "int text_status",
        "int prop_status",
        "int locked",
        "int copied",
        "int switched",
        "int repos_text_status",
        "int repos_prop_status",
        "void *repos_lock"
    ]

   # I want to print the value of each member of s, but I also need to 
know the class
   # which is hard coded here and shouldn't be
    def printStruct(s)
        Svn_status_t.members.each do |name|
            print "  ", name, ": " , eval("s.#{name}"), "\n"
        end
    end

    # pstatus comes from a c routine and is a pointer to a c struct
    status= Svn_status_t.new(pstatus)
   
p status
printStruct(status)

end