reuse _unsafe_cast strategy from apache#103

src/arraytypes/fixedsizelist.jl

@@ -39,14 +39,30 @@ Base.size(l::FixedSizeList) = (l.ℓ,)
     else
         off = (i - 1) * N
         if X === T && isbitstype(Y)
-            tup = reinterpret(NTuple{N, Y}, view(l.data, (off + 1):(off + N)))[]
+            tup = _unsafe_load_tuple(NTuple{N,Y}, l.data, off)
         else
             tup = ntuple(j->l.data[off + j], N)
         end
         return ArrowTypes.arrowconvert(T, tup)
     end
 end
 
+function _unsafe_load_tuple(::Type{NTuple{N,T}}, bytes::Vector{UInt8}, i::Integer) where {N,T}
+    a = Ref(bytes, i)
+    b = Ref{NTuple{N,T}}()
+    return _unsafe_cast(a, b, N)
+end
+
+function _unsafe_cast(a::Ref{T}, b::Ref{B}, n::Integer)::B where {T,B}
+    A = eltype(T)
+    GC.@preserve a b begin
+        ptra = Base.unsafe_convert(Ptr{A}, a)
+        ptrb = Base.unsafe_convert(Ptr{B}, b)
+        unsafe_copyto!(Ptr{A}(ptrb), ptra, n)
+    end
+    return b[]
+end
+
 @propagate_inbounds function Base.setindex!(l::FixedSizeList{T}, v::T, i::Integer) where {T}
     @boundscheck checkbounds(l, i)
     if v === missing