From: Robert Klemme <shortcutter@...>
Date: 2008-05-23T04:40:10+09:00
Subject: Re: customized serialization unreliable????

On 22.05.2008 18:48, sayoyo Sayoyo wrote:
> First, Thanks you very much for helping me, Yes, I have tried it, and 
> the serialization still works randomly. no idea why...
> 
> I suspect the there is a problem in memory allocation somewhere when 
> data is written to the "file", since it is an random effect, I can 
> hardly put a hand on it.

My gut feeling rather points to an effect caused by different ordering 
of objects in a Hash.  Or you have an issue caused by a loop in your 
object graph.  As far as I can see custom serialization works ok - at 
least for non complex structures:

irb(main):016:0> F = Struct.new :a, :b do
irb(main):017:1*   def marshal_dump
irb(main):018:2>     [a,b]
irb(main):019:2>   end
irb(main):020:1>
irb(main):021:1*   def marshal_load(x)
irb(main):022:2>     self.a = x[0]
irb(main):023:2>     self.b = x[1]
irb(main):024:2>   end
irb(main):025:1> end
=> F
irb(main):026:0> x = F.new 1,2
=> #<struct F a=1, b=2>
irb(main):027:0> s = Marshal.load(Marshal.dump(x))
=> #<struct F a=1, b=2>
irb(main):028:0>

I am not sure why you need custom serialization.  But here is an 
alternative approach: create a method that returns a data structure 
which you then serialize and add a class method that constructs your in 
memory structure from that state.  E.g.

class Foo
   attr_accessor :name, :size

   def to_serial
     [name, size]
   end

   def self.from_serial(obj)
     f = new
     f.name = obj[0]
     f.size = obj[1]
     f
   end
end

Of course, this only works if you know what you are deserializing.

Another alternative is to separate "configuration state" (which is 
serializable, e.g. file name) from "operation state" (which is not 
serializable, e.g. file descriptor) and serialize only the configuration 
state.  This is probably the cleanest approach.

> do you know who is the responsible of this part of ruby?

You probably can find out by looking at the sources.

Kind regards

	robert