[Borges-users] suggestion: snapshots without weakrefs

[Eric Hodel]

??????? ???????? (slepnev_v at rambler.ru) wrote:

> because weakrefs+continuations turned out so buggy (and ignored by 
> ruby-core), I designed a way to snapshot stuff without weakrefs. The 
> idea is to keep an anonymous module for each session, and use 
> ObjectSpace.each_object(mod) to create snapshots. The snapshots of 
> objects don't keep their class - just their instance variables, so 
> snapshots aren't eligible for snapshotting again. I've unit-tested the 
> stuff a bit (though not with Borges yet), and it seems to work.

This looks very nice, I'm very interested in seeing an integrated
patch...

[snip details]

> Here's the source, it's not optimal yet, much room for improvement:
> 
> module BacktrackMixin
>
> 	def shallow_copy
> 		copy_instance_variables(self,Object.new)
> 	end
> 
> 	def restore_from(copy)
> 		copy_instance_variables(copy,self)
> 	end
> 
> 	private; def copy_instance_variables(src,dest)
> 		src.instance_variables.each do |name|
> 			dest.instance_variable_set(name, 
> 			src.instance_variable_get(name))
> 		end
> 		return dest
> 	end
> 
> end
> 
> class Snapshot
> 
> 	def initialize(mod)
> 		@snap = {}
> 		ObjectSpace.each_object(mod) {|obj|	@snap[obj] = 
> 		obj.shallow_copy}
> 	end

This fetches each object that includes mod, right?  Nifty!

(Since Module.new { include Backtrack } is unique, it only gathers
those objects including exactly that instance, right?)

> 	def restore
> 		@snap.each {|k,v| k.restore_from v}
> 	end
> 
> 	def size; @snap.size end
> 
> end

-- 
Eric Hodel - drbrain at segment7.net - http://segment7.net
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