What's the difference between Pinned and StableRef...
# kotlin-nativen
natario1
11/08/2021, 10:28 AMWhat's the difference between Pinned and StableRef? They look so similar besides maybe one being a data class and another a value class. Wouldn't one of them be enough?
d
Dominaezzz
11/08/2021, 4:20 PMWell, the former allows access to data and the latter is just an opaque reference.
n
natario1
11/08/2021, 4:28 PMWhat do you mean exactly? I can see both StableRef.get and Pinned.get, returning an instance of the pinned type T
d
Dominaezzz
11/08/2021, 4:29 PMAccessible from C.
n
natario1
11/08/2021, 4:33 PMIf you look at source code they seem to do exactly the same thing, a stable opaque pointer. I can see slight differences in the api (Pinned offers refTo / addressOf for arrays, maybe this is what you are referring to?), but I don't think this justifies having two separate concepts? I am probably missing something
natario1
11/08/2021, 4:37 PMOne interesting difference is that StableRef is in "main" folder here https://github.com/JetBrains/kotlin/tree/master/kotlin-native/Interop/Runtime/src , and Pinned is in "native" only. Maybe we have both for historical reasons
d
Dominaezzz
11/08/2021, 4:39 PMStableRef is useful for callbacks in C, especially the ones that let you pass "user data" , this lets you reference kotlin objects from staticCFunctions. Pinning just lets you pass a pointer to the underlying array to some C function like fread.
👍 1
n
natario1
11/08/2021, 4:46 PMYeah I get it. But it's the same concept, if Pinned constructor was public, you could do both things with pinned
natario1
11/08/2021, 4:48 PMAnyway, I now wrapped my head around both so I can live with this 😄 it was confusing though, if there's no reason to, I think that a single concept would be better for beginners.
j
jimn
11/25/2021, 10:44 PMwas this the intent of `pin`ned? is there a more succint solution?
i am just feeling along to satisfy intellij for the most part until the generics somehow line up.
Copy code
var buffer= ByteArray(128)
var iov:iovec =alloc {
iov_base = buffer.pin().objcPtr().toLong().toCPointer<COpaque>() as COpaquePointer /* = kotlinx.cinterop.CPointer<out kotlinx.cinterop.CPointed> */
iov_len = 128.toULong()
}14 Views