I think all this works ok. I've enclosed an example interaction from
the docs, which I've just extended to evolve `fish` in addition to
`aq`.
So, it's all implemented, and I can push if it seems like an ok
interface...
At Tue, 7 Jun 2016 17:14:54 +0200, Berthold Bäuml wrote:
> Sorry, I did not think this through completely. Serialization of cstructs, as
> it is currently implemented, loses all “sub-structure” for non-pointer
> content, correct?
>
> But wouldn’t because of this lost sub-structure your alternative
> compatibility
> protocol also fail when it comes to hierarchically embedded structs where
> deep
> down in the hierarchy a new version of a struct should be used?
>
>
> (define-serializable-cstruct _pond ([depth _float]))
> (define-serializable-cstruct _forrest ([a_pond _pond]))
>
> and then a new version:
> (define-serializable-cstruct _old-pond ([depth _float]))
> (define-serializable-cstruct _pond ([num-fish _int]
> [depth _float])
>
> (define-serializable-cstruct _forrest ([a_pond _pond]))
>
> So, the version of _forrest does not change and, hence, there is no way to
> deserialize the correct, new version of the _pond.
>
> I think this could only be resolved by changing the serialization so that it
> keeps all relevant information also for non-pointer content.
>
> Berthold
> > On 06 Jun 2016, at 19:22, Matthew Flatt <mfl...@cs.utah.edu> wrote:
> >
> > Yes, but I think a different protocol will be needed than for
> > `serializable-struct`.
> >
> > With
> >
> > (serializable-struct pond (depth))
> >
> > it's clear that the deserializer receives a single value for the single
> > field (or, more generally, N values for N fields). So, it's clear how
> > to make a compatibility deserialization function:
> >
> > (serializable-struct/versions pond 1 (num-fish depth)
> > ([0 (lambda (d) (pond 0 d))
> > (lambda () ....)]))
> >
> > With
> >
> > (define-serializable-cstruct _pond ([depth _float]))
> >
> > the deserializer internally deals with a byte-string representation of
> > non-pointer content plus a structured representation of pointer
> > content. We probably don't want to expose those details, and you don't
> > want to deal with them.
> >
> > An alternative it to make the compatibility protocol work in terms of a
> > separate cstruct declaration:
> >
> > (define-serializable-cstruct _old-pond ([depth _float]))
> >
> > (define-serializable-cstruct _pond ([num-fish _int]
> > [depth _float])
> > #:version 1
> > #:other-versions ([0 deserialize-chain:cstruct:old-pond
> > (lambda (op)
> > (make-pond 0 (old-pond-depth op)))
> > (lambda () ....)]))
> >
> > That is, compatibility deserialization is based on a reference to
> > deserialization information for a cstruct that has the same shape as
> > the old version, plus converters from instances of the old shape to the
> > new cstruct.
> >
> > Does that interface seem ok?
> >
> >
> > At Sun, 5 Jun 2016 22:04:23 +0200, Berthold Bäuml wrote:
> >> Would it be possible to add for the serializable cstruct
> >> (define-serializable-cstruct) versioning like in
> >> define-serializable-struct/versions?
> >>
> >> Berthold
> >>
> >> --
> >> -----------------------------------------------------------------------
> >> Berthold Bäuml -- Head of Autonomous Learning Robots Lab
> >> DLR, Robotics and Mechatronics Center (RMC)
> >> Münchner Str. 20, D-82234 Wessling
> >> Phone +49 8153 282489
> >> http://www.robotic.de/Berthold.Baeuml
> >>
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> --
> -----------------------------------------------------------------------
> Berthold Bäuml -- Head of Autonomous Learning Robots Lab
> DLR, Robotics and Mechatronics Center (RMC)
> Münchner Str. 20, D-82234 Wessling
> Phone +49 8153 282489
> http://www.robotic.de/Berthold.Baeuml
>
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> (define-serializable-cstruct fish ([color _int]))
> (define f0/s (serialize (make-fish 1)))
> (fish-color (deserialize f0/s))
1
> (define-serializable-cstruct aq ([a fish-pointer]
[d aq-pointer/null])
#:malloc-mode 'nonatomic)
> (define aq1 (make-aq/mode (make-fish 6) #f))
> (set-aq-d! aq1 aq1) ; create a cycle
> (define aq0/s (serialize aq1))
> (aq-a (aq-d (aq-d (deserialize aq0/s))))
#<cpointer:fish>
; Same shape as original aq:
> (define-serializable-cstruct old-aq ([a fish-pointer]
[d _pointer])
#:malloc-mode 'nonatomic)
; Replace the original aq:
> (define-serializable-cstruct aq ([a fish-pointer]
[b fish-pointer]
[d aq-pointer/null])
#:malloc-mode 'nonatomic
#:version 1
#:other-versions ([0 deserialize-chain:cstruct:old-aq
(lambda (oa)
(make-aq/mode (old-aq-a oa)
(old-aq-a oa)
(cast (old-aq-d oa) _pointer
aq-pointer)))
(lambda (a)
(make-old-aq/mode (aq-a a)
(aq-d a)))
(lambda ()
(define tmp-fish (make-fish 0))
(define a (make-aq/mode tmp-fish tmp-fish #f))
(values a
(lambda (oa)
(set-aq-a! a (old-aq-a oa))
(set-aq-b! a (old-aq-a oa))
(set-aq-d! a (cast (old-aq-d oa) _pointer
aq-pointer)))))]))
; Deserialize old instance to new cstruct:
> (fish-color (aq-a (aq-d (aq-d (deserialize aq0/s)))))
6
> (define aq1/s (serialize (make-aq (make-fish 1) (make-fish 2) #f)))
; New version of fish:
> (define-serializable-cstruct old-fish ([color _int]))
> (define-serializable-cstruct fish ([weight _float]
[color _int])
#:version 1
#:other-versions ([0 deserialize-chain:cstruct:old-fish
(lambda (of)
(make-fish 10.0 (old-fish-color of)))
(lambda (a) (error "cycles not possible!"))
(lambda () (error "cycles not possible!"))]))
; Deserialized content upgraded to new fish:
> (fish-color (aq-b (deserialize aq1/s)))
2
> (fish-weight (aq-b (deserialize aq1/s)))
10.0
