felipecrv commented on code in PR #36489:
URL: https://github.com/apache/arrow/pull/36489#discussion_r1254875245
##########
cpp/src/arrow/c/bridge.cc:
##########
@@ -663,6 +672,115 @@ Status ExportRecordBatch(const RecordBatch& batch, struct
ArrowArray* out,
return Status::OK();
}
+//////////////////////////////////////////////////////////////////////////
+// C device arrays
+
+Result<std::pair<DeviceType, int64_t>> validate_device_info(const ArrayData&
data) {
+ DeviceType device_type = DeviceType::UNKNOWN;
+ int64_t device_id = -1;
+
+ for (const auto& buf : data.buffers) {
+ if (!buf) {
+ // some buffers might be null
+ // for example, the null bitmap is optional if there's no nulls
+ continue;
+ }
+
+ if (device_type == DeviceType::UNKNOWN) {
+ device_type = buf->device_type();
+ device_id = buf->device()->device_id();
+ continue;
+ }
+
+ if (buf->device_type() != device_type) {
+ return Status::Invalid(
+ "exporting device array with buffers on more than one device.");
+ }
+
+ if (buf->device()->device_id() != device_id) {
+ return Status::Invalid(
+ "exporting device array with buffers on multiple device ids.");
+ }
+ }
+
+ // recursively check the children
+ auto info = std::make_pair(device_type, device_id);
Review Comment:
I think the pattern I suggest means you don't have to rely on any assumption.
You can wrap the auxiliary recursive function for ease of use. This pattern
is common in functional programming when turning a recursive function into a
tail-call optimized one: create aux function that takes accumulator, return
accumulator when done, wrap aux in a simple interface.
```cpp
Status validate_device_info(const ArrayData& data, DeviceType *device_type,
int64_t *device_id);
Result<pair> validade_device_info(concst ArrayData& data) {
DeviceType device_type;
int64_t device_id;
RETURN_NOT_OK(validate_device_info(data, &device_type, &device_id));
return {device_type, device_id};
}
```
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