pitrou commented on code in PR #37797:
URL: https://github.com/apache/arrow/pull/37797#discussion_r1345665191
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python/pyarrow/ipc.pxi:
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@@ -815,6 +817,73 @@ cdef class RecordBatchReader(_Weakrefable):
self.reader = c_reader
return self
+ def __arrow_c_stream__(self, requested_schema=None):
+ """
+ Export to a C ArrowArrayStream PyCapsule.
+
+ Parameters
+ ----------
+ requested_schema: Schema, default None
+ The schema to which the stream should be casted. Currently, this is
+ not supported and will raise a NotImplementedError if the schema
+ doesn't match the current schema.
+
+ Returns
+ -------
+ PyCapsule
+ A capsule containing a C ArrowArrayStream struct.
+ """
+ cdef:
+ ArrowArrayStream* c_stream =
<ArrowArrayStream*>malloc(sizeof(ArrowArrayStream))
+
+ if requested_schema is not None:
+ out_schema = Schema._import_from_c_capsule(requested_schema)
+ # TODO: figure out a way to check if one schema is castable to
+ # another. Once we have that, we can perform validation here and
+ # if successful creating a wrapping reader that casts each batch.
+ if self.schema != out_schema:
+ raise NotImplementedError("Casting to requested_schema")
+
+ with nogil:
+ check_status(ExportRecordBatchReader(self.reader, c_stream))
+
+ return PyCapsule_New(c_stream, "arrow_array_stream",
&pycapsule_stream_deleter)
+
+ @staticmethod
+ def _import_from_c_capsule(stream):
+ """
+ Import RecordBatchReader from a C ArrowArrayStream PyCapsule.
+
+ Parameters
+ ----------
+ stream: PyCapsule
+ A capsule containing a C ArrowArrayStream PyCapsule.
+
+ Returns
+ -------
+ RecordBatchReader
+ """
+ cdef:
+ ArrowArrayStream* c_stream
+ shared_ptr[CRecordBatchReader] c_reader
+ RecordBatchReader self
+
+ # sanity checks
+ if not PyCapsule_IsValid(stream, 'arrow_array_stream'):
+ raise ValueError(
Review Comment:
You can also let PyCapsule_GetPointer raise its own exception.
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