paleolimbot commented on code in PR #387:
URL: https://github.com/apache/arrow-nanoarrow/pull/387#discussion_r1492780215
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src/nanoarrow/nanoarrow.hpp:
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@@ -273,6 +280,49 @@ using UniqueArrayView = internal::Unique<struct
ArrowArrayView>;
/// @}
+/// \defgroup nanoarrow_hpp-buffer Buffer helpers
+///
+/// Helpers to wrap buffer-like C++ objects as ArrowBuffer objects that can
+/// be used to build ArrowArray objects.
+///
+/// @{
+
+/// \brief Initialize a buffer wrapping an arbitrary C++ object
+///
+/// Initializes a buffer with a release callback that deletes the moved obj
+/// when ArrowBufferReset is called. T must be movable.
+template <typename T>
+static inline void BufferInitWrapped(struct ArrowBuffer* buffer, T obj, const
void* ptr,
+ int64_t size_bytes) {
+ T* obj_moved = new T(std::move(obj));
+ buffer->data = const_cast<uint8_t*>(reinterpret_cast<const uint8_t*>(ptr));
+ buffer->size_bytes = size_bytes;
+ buffer->capacity_bytes = 0;
+ buffer->allocator =
+ ArrowBufferDeallocator(&internal::DeallocateWrappedBuffer<T>, obj_moved);
+}
Review Comment:
I'll update the documentation here, but the `ptr` (which gets assigned to
`buffer->data`) can be whatever you want. The C++ object `T` manages the
lifecycle, but this constructor doesn't try to guess what the actual pointer
value that it keeps valid is.
In the context of your PR, it would replace your `set_buffer()` with
`BufferInitWrapped(device_buf, device_buf->data(), device_buf.size())`.
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