From: JamesBritt <james@...>
Date: 2002-08-06T10:59:51+09:00
Subject: Question about Marshal.dump behavior

I had gotten the impression that the third parameter to Marshal.dump acted
as a limit on the depth of the serialization.  One could use it to
deliberately exclude data from serialization if it was stored in nested
objects below a certain level.

But I've run into some behavior that suggests that to use this parameter you
have to know the complete depth of the target object; passing a number lower
than that depth raises an exception.

Here is some example code:
#----------------------------
class LimitTest
  def initialize( x )
    @stuff =  x
  end
end


lt = LimitTest.new( "a" )
mdata = Marshal.dump(lt, 2 )  #OK

lt = LimitTest.new( ["b", "c"])
mdata = Marshal.dump(lt, 2 )  # Error
# `dump': exceed depth limit (ArgumentError)
#----------------------------

This happens with ruby 1.6.7 (2002-03-01) [i586-mswin32],
ruby 1.7.2 (2002-06-29) [i386-mswin32], and ruby 1.7.2 (2002-05-02)
[i586-linux]

Is this behavior correct?  It seems the calling code has to know the depth
of the object and any references it has, and is compelled to serialize the
entire object.  Can one tell Marshal.dump to ignore objects below a certain
depth (without writing your own _dump)?

Thanks,

James