zeroshade commented on code in PR #43632:
URL: https://github.com/apache/arrow/pull/43632#discussion_r1750452544
##########
cpp/src/arrow/c/abi.h:
##########
@@ -228,6 +228,180 @@ struct ArrowDeviceArrayStream {
#endif // ARROW_C_DEVICE_STREAM_INTERFACE
+#ifndef ARROW_C_ASYNC_STREAM_INTERFACE
+#define ARROW_C_ASYNC_STREAM_INTERFACE
+
+// ArrowAsyncTask represents available data from a producer that was passed to
+// an invocation of `on_next_task` on the ArrowAsyncDeviceStreamHandler.
+struct ArrowAsyncTask {
+ // This callback should populate the ArrowDeviceArray associated with this
task.
+ // The order of ArrowAsyncTasks provided by the producer enables a consumer
to
+ // ensure the order of data to process.
+ //
+ // Returns: 0 if successful, errno-compatible error otherwise.
+ //
+ // If a non-0 value is returned then it should be followed by a call to
`on_error`
+ // on the appropriate ArrowAsyncDeviceStreamHandler.
+ //
+ // Rather than a release callback, any required cleanup should be performed
as part
+ // of the invocation of `get_data`. Ownership of the Array is passed to the
consumer
+ // calling this, and so it must be released separately.
+ //
+ // It is only valid to call this method exactly once.
+ int (*get_data)(struct ArrowArrayTask* self, struct ArrowDeviceArray* out);
+
+ // opaque task-specific data
+ void* private_data;
+};
+
+// ArrowAsyncProducer represents a 1-to-1 relationship between an async
producer
+// and consumer. This object allows the consumer to perform backpressure and
flow
+// control on the asynchronous stream processing. This object must be owned by
the
+// producer who creates it, and thus is responsible for cleaning it up.
+struct ArrowAsyncProducer {
+ // A consumer must call this function to start receiving on_next_task calls.
+ //
+ // It *must* be valid to call this synchronously from within on_next_task or
+ // on_schema, with a producer placing an upper bound on possible synchronous
+ // recursion between calls of on_next_task -> request -> on_next_task ->....
+ //
+ // After cancel has been called, additional calls to this function must be
NOPs,
+ // but allowed.
+ //
+ // While not cancelled, calling this function must register the given number
of
+ // additional arrays/batches to be produced with the producer. The producer
should
+ // only call `on_next_task` at most the registered number of arrays before
propagating
+ // backpressure.
+ //
+ // While not cancelled, calling request MAY synchronously call
`on_next_task`,
+ // `on_error`, or `release` on the ArrowAsyncDeviceStreamHandler.
+ //
+ // Any error encountered by calling request must be propagated by calling
the `on_error`
+ // callback of the ArrowAsyncDeviceStreamHandler.
+ //
+ // A producer must support an unbounded number of calls to request and must
support
+ // a total registered demand (sum requested - sum delivered) of up to
UINT64_MAX.
+ void (*request)(struct ArrowAsyncProducer* self, uint64_t n);
+
+ // This cancel callback signals a producer that it must eventually stop
making calls
+ // to on_next_task. It must be idempotent and thread-safe.
+ //
+ // After calling cancel once, subsequent calls must be NOPs.
+ //
+ // It is not required that calling cancel affect the producer immediately,
only that it
+ // must eventually stop calling on_next_task and subsequently call release
on the
+ // async handler. As such, a consumer must be prepared to receive one or
more calls to
+ // `on_next_task` even after calling cancel if there are still requested
arrays pending.
+ //
+ // Any error encountered during handling a call to cancel must be reported
via the on_error
+ // callback on the async stream handler.
+ void (*cancel)(struct ArrowAsyncProducer* self);
Review Comment:
successful cancellation should lead only to `release`. The producer should
only call `on_error` if an error occurs during processing of `cancel`.
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