westonpace commented on code in PR #35565:
URL: https://github.com/apache/arrow/pull/35565#discussion_r1205262340
##########
cpp/src/arrow/type_traits.h:
##########
@@ -1309,6 +1309,28 @@ static inline int offset_bit_width(Type::type type_id) {
return 0;
}
+/// \brief get the alignment a buffer should have to be considered "value
aligned"
+///
+/// Some buffers are frequently type-punned. For example, in an int32 array
the
+/// values buffer is frequently cast to int32_t*
+///
+/// This sort of punning is technically only valid if the pointer is aligned
to a
+/// proper width (e.g. 4 bytes in the case of int32). However, most modern
compilers
+/// are quite permissive if we get this wrong. Note that this alignment is
something
+/// that is guaranteed by malloc (e.g. new int32_t[] will return a buffer that
is 4
+/// byte aligned) or common libraries (e.g. numpy) but it is not currently
guaranteed
+/// by flight (GH-32276).
+///
+/// We call this "value aligned" and this method will calculate that required
alignment.
+///
+/// \param type_id the type of the array containing the buffer
+/// Note: this should be the indices type for a dictionary
array since
+/// A dictionary array's buffers are indices. It should be the
storage
+/// type for an extension array.
+/// \param buffer_index the index of the buffer to check, for example 0 will
typically
+/// give you the alignment expected of the validity buffer
Review Comment:
Fixed
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