unique_ptr is used to designate unique ownership of the buffer
just created. It's fairly compatible with shared_ptr since
unique_ptr can convert implicitly to shared_ptr.
One other refactoring in play here: we've been moving from
Status-returning-out-argument functions to the more ergonomic
Result<T>. I'd recommend you write a new macro for dealing with
Result<T>s, like:
#define ASSIGN_OR_THROW_IMPL(result_name, lhs, rexpr) \
auto&& result_name = (rexpr); \
THROW_NOT_OK((result_name).status()); \
lhs = std::move(result_name).ValueUnsafe();
#define ASSIGN_OR_THROW(lhs, rexpr) \
ASSIGN_OR_THROW_IMPL(_maybe ## __COUNTER__, lhs, rexpr)
Then lines such as
https://github.com/Paradigm4/bridge/blob/master/src/Driver.h#L196
can be rewritten as:
ASSIGN_OR_THROW(buffer, arrow::AllocateBuffer(length));
Does that help?
On Thu, May 27, 2021 at 3:47 PM Rares Vernica <rvern...@gmail.com> wrote:
> Hello,
>
> We are trying to migrate from Arrow 0.16.0 to a newer version, hopefully up
> to 4.0.0. The Arrow 0.17.0 change in AllocateBuffer from taking a
> shared_ptr<Buffer> to returning a unique_ptr<Buffer> is making things very
> difficult. We wonder if there is a strong reason behind the change from
> shared_ptr to unique_ptr and if there is an easier path forward for us.
>
> In our code, we interchangeably use Buffer and ResizableBuffer. We pass
> around these pointers across a number of classes. They are allocated or
> resized here
> https://github.com/Paradigm4/bridge/blob/master/src/Driver.h#L191
> Moreover,
> we cast the ResizableBuffer instance to Buffer in order to have all our
> methods only deal with Buffer, here
> https://github.com/Paradigm4/bridge/blob/master/src/Driver.h#L151
>
> In Arrow 0.16.0 AllocateBuffer took a shared_ptr<Buffer> and this works
> fine. In Arrow 0.17.0 AllocateBuffer returns a unique_ptr<Buffer>. Our cast
> from ResizableBuffer to Buffer won't work on unique_ptr and we won't be
> able to pass the Buffer around so easily.
>
> I noticed that there is another AllocateBuffer in MemoryManger that returns
> a shared_ptr.
>
> https://arrow.apache.org/docs/cpp/api/memory.html?highlight=resizablebuffer#_CPPv4N5arrow13MemoryManager14AllocateBufferE7int64_t
> Is this a better alternative to allocate a buffer? Is there a similar
> method to allocate a resizable buffer?
>
> Thank you,
> Rares
>
