From: Hugh Sasse Staff Elec Eng <hgs@...>
Date: 2002-08-15T01:15:59+09:00
Subject: RE: Problems with Marshal

On Thu, 15 Aug 2002, Berger, Daniel wrote:

> > -----Original Message-----
> > From: Hugh Sasse Staff Elec Eng [mailto:hgs@dmu.ac.uk]
> >
> > How are you sending and receiving the data?
>
> Ok, I've narrowed it down partially to a newline issue with Marshal.  Here

Curious.  I didn't expect marshal to make much use of whitespace...

> are a sample client and server to demonstrate.  Just start the server in one
        [...]
> The question I have, then, is how do I make sure that the marshalled object
> is properly newline terminated?

When I wanted to do this I took the somewhat paranoid approach that
the only characters which are guaranteed to be passable between
systems are those that make up base64 -- which is why base64 was
invented.  See RFC989 Section 5.2 for details of this.

#!/usr/local/bin/ruby -w

# Routine to encode an object into a string for transmission.

# Author: Hugh Sasse
# Created: 07-APR-2000

# RCS Infromation:
# $Revision: 1.3 $
# last put in RCS: $Date: 2000-12-12 11:36:17+00 $
# ID: $Id: Encode.rb,v 1.3 2000-12-12 11:36:17+00 hgs Exp hgs $

# This takes an object, and it uses Marshal to create a string.
# It then converts that string to base 64.
# Marshal is used even on strings so that the process is reversible.

# If this file is executed directly (i.e. not using "require") then
# it performs a basc self test.

class Encoded
    include Marshal

    def decode
        @decoded
    end

    def encode
        @encoded
    end

    private

    def initialize(thing, code = true, depth=-1)
        if code == true
	    @decoded = thing
            @encoded = [Marshal.dump(@decoded,depth)].pack("m")
        else
	    @encoded = thing
            @decoded = Marshal.load(@encoded.unpack("m")[0])
        end
    end

end

if __FILE__ == $0

    print "Self test\n"

    # define an arbitrary class to save.

    class Fish
        def swim
            print "#{@name} is swimming\n"
        end
        def initialize(name)
            @name = name
        end
    end

    eric = Fish.new("Eric")

    # Build an arrray of varying things to save...

    x = [1,3.4,"hello!",{"this" => "that"},eric]
    p(x)
    e = Encoded.new(x, true, 20)

    # s is the string to decode...
    s = e.encode()
    p(s.type())
    p(s)

    # decode it anew. New instance not a copy of the old
    f = Encoded.new(s,false)
    result = f.decode()
    p(result)

    p(result[-1].type())

    # show that the las item is really of the class we defined.
    result[-1].swim()

end

>
> Regards,
>
> Dan
>
        Hugh