DeepCloning a datastructure

[Marc Schöchlin]

Hello List,

i am searching for a convenient way to deep-clone a nested datastructure.

My data structure looks like this:

(map[string]map[string]*processing.AccountingSet) (len=1) {
 (string) (len=16) "foo1.bar.com:443": (map[string]*processing.AccountingSet) (len=1) {
  (string) (len=3) "all": (*processing.AccountingSet)(0xc000090060)({
   count: (int64) 90,
   sum: (int64) 80000001480,
   codes: (map[int]int) (len=1) {
    (int) 301: (int) 90
   },
   classes: (map[int]int) (len=6) {
    (int) 0: (int) 90,
    (int) 500000: (int) 0,
    (int) 5000000: (int) 0,
    (int) 10000000: (int) 0,
    (int) 60000000: (int) 0,
    (int) 300000000: (int) 0
   }
  })
 }
}

How can i make a exact, deep, and completely independent copy of that structure?

What i tried:
(c.stats contains the mentioned data structure which should by copied to c.stats)

import "github.com/ulule/deepcopier"

c.lastStats = map[string]map[string]*AccountingSet{}
err = deepcopier.Copy(c.stats).To(c.lastStats)
if err != nil {
        glog.Errorf("unable to clone : '%s'", err.Error())
}

This doesn't work. The target structure is empty after the copy operation.

Regards
Marc

[Hugh Emberson]

On Thu, Apr 16, 2020 at 2:07 PM Marc Schöchlin <m...@256bit.org> wrote:

i am searching for a convenient way to deep-clone a nested datastructure.

I've used https://github.com/mohae/deepcopy with some success.  YMMV.

Regards,

Hugh

[Hugh Emberson]

And, I realized just after posting that your data structure has private fields in it as https://github.com/mohae/deepcopy won't work on those.

[Carsten Orthbandt]

The easiest way is to marshal everything into some sort of byte slice, then unmarshal back. JSON doesn't work for this if there are private fields. But gotiny (https://github.com/niubaoshu/gotiny) does. If you use interfaces in your data, you have to register their types, everthing else is automatic.

[Ankit R Gadiya]

How about doing it manually? You can define a DeepCopy method on the type and manually allocate a new struct and initialize the maps and slices by looping over them. That way you get to have more control over all the fields and problem of private fields is solved as well. I would guess this would be faster as well because no reflection is required.

As far as I know Kubernetes uses this approach and they have a code-generator which can conveniently generate the code for the structs.

https://github.com/kubernetes/code-generator/tree/master/cmd/deepcopy-gen

On Fri, Apr 17, 2020 at 2:07 PM Carsten Orthbandt <carsten....@gmail.com> wrote:

The easiest way is to marshal everything into some sort of byte slice, then unmarshal back. JSON doesn't work for this if there are private fields. But gotiny (https://github.com/niubaoshu/gotiny) does. If you use interfaces in your data, you have to register their types, everthing else is automatic.

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[Zhaoxun Yan]

Yes there are two open source packages regarding "DeepCopy"

https://github.com/mohae/deepcopy/

https://github.com/barkimedes/go-deepcopy/

Has anyone tried them yet?