Provide path for getting sizes on directory iteration #60
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…ntly return a value of the `FieldHash()` of the dagpb link. This change has them instead return a `IterLink`. In both cases, the "exposed" interface of the returned type, `AsLink()` exposes the underlying hash cidLink to the entry. By using a wrapping `IterLink` type, we provide an opportunity to type-cast the response, and instead of treating the response under it's returned `ipld.Node` interface, the client has the ability to do something of the form: ``` k, next, err := iterator.Next() nextSize := next.(*iter.IterLink).Substrate.FieldSize() ```
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Seems reasonable to me and IMO less confusing than #51.
An area I'm fuzzy about is what the expectations are for ipld.Node around getting out data of multiple forms. For example, should this have been able to return a PBLink and PBLink be able to easily return a cidlink.Link and the rest of its fields? If we need a separate wrapper struct (e.g. IterLink) would this be better off as another type of PBLink in go-codec-dagpb?
Answering these isn't a blocker from me, but something I'm curious about from the people who work more closely with go-ipld-prime (e.g. @rvagg). If we need to break this in the future it's not the end of the world or anything, but if we can figure this out sooner it'll save some pain later.
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I went with this so that the This is (if i remember correctly) to provide the higher level semantics of directory traversal that are used for pathing through unixfs. |
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@willscott I agree, and probably changing |
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Good question @aschmahmann, I'm not sure there's a clean answer (or that I'm the best person to provide one!); except to say that I think there should be a reasonable expectation of consistent behaviour of an You could look at #51 with that lens and see how the approach here is a bit cleaner. Not that #51 has obvious breakage potential, but this approach has the standard mapping of Kind:Behaviour. |
When making a map iterator over a directory, calls to
.Next()currently return a value of theFieldHash()of the dagpb link.This change has them instead return a
IterLink.In both cases, the "exposed" interface of the returned type,
AsLink()exposes the underlying hash cidLink to the entry.By using a wrapping
IterLinktype, we provide an opportunity to type-cast the response, and instead of treating the response under it's returnedipld.Nodeinterface, the client has the ability to do something of the form: