pitrou commented on code in PR #34972:
URL: https://github.com/apache/arrow/pull/34972#discussion_r1161988488
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cpp/src/arrow/c/abi.h:
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@@ -106,6 +169,77 @@ struct ArrowArrayStream {
#endif // ARROW_C_STREAM_INTERFACE
+#ifndef ARROW_C_DEVICE_STREAM_INTERFACE
+#define ARROW_C_DEVICE_STREAM_INTERFACE
+
+struct ArrowDeviceArrayStream {
+ // The device that this stream produces data on.
+ // All ArrowDeviceArrays that are produced by this
+ // stream should have the same device_type as set
+ // here. The device_type needs to be provided here
+ // so that consumers can provide the correct type
+ // of stream_ptr when calling get_next.
+ ArrowDeviceType device_type;
+
+ // Callback to get the stream schema
+ // (will be the same for all arrays in the stream).
+ //
+ // Return value: 0 if successful, an `errno`-compatible error code otherwise.
+ //
+ // If successful, the ArrowSchema must be released independently from the
stream.
+ int (*get_schema)(struct ArrowDeviceArrayStream*, struct ArrowSchema* out);
+
+ // Callback to get the device id for the next array.
+ // This is necessary so that the proper/correct stream pointer can be
provided
+ // to get_next. The parameter provided must not be null.
+ //
+ // Return value: 0 if successful, an `errno`-compatible error code otherwise.
+ //
+ // The next call to `get_next` should provide an ArrowDeviceArray whose
+ // device_id matches what is provided here, and whose device_type is the
+ // same as the device_type member of this stream.
+ int (*get_next_device_id)(struct ArrowDeviceArrayStream*, int*
out_device_id);
+
+ // Callback to get the next array
+ // (if no error and the array is released, the stream has ended)
+ //
+ // the provided stream_ptr should be the appropriate stream, or
+ // equivalent object, for the device that the data is allocated on
+ // to indicate where the consumer wants the data to be accessible.
Review Comment:
> The idea of a consumer of the interface passing a stream to the producer
of the interface is that the producer can guarantee that the data is safe to
consume on the passed in stream.
This means that the `ArrowDeviceArray` struct itself doesn't hold any
information about the CUDA stream the array can be accessed from, and the
consumer _has_ to go through the `ArrowDeviceStream` to pass its own stream
information.
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