rgommers commented on code in PR #38472: URL: https://github.com/apache/arrow/pull/38472#discussion_r1417350931
########## cpp/src/arrow/c/dlpack.cc: ########## @@ -0,0 +1,151 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +#include "arrow/c/dlpack.h" + +#include "arrow/array/array_base.h" +#include "arrow/c/dlpack_abi.h" +#include "arrow/device.h" +#include "arrow/type.h" + +namespace arrow { + +namespace dlpack { + +Status getDLDataType(const std::shared_ptr<DataType>& type, DLDataType* out) { + DLDataType dtype; + dtype.lanes = 1; + dtype.bits = type->bit_width(); + switch (type->id()) { + case Type::INT8: + case Type::INT16: + case Type::INT32: + case Type::INT64: + dtype.code = DLDataTypeCode::kDLInt; + *out = dtype; + return Status::OK(); + case Type::UINT8: + case Type::UINT16: + case Type::UINT32: + case Type::UINT64: + dtype.code = DLDataTypeCode::kDLUInt; + *out = dtype; + return Status::OK(); + case Type::HALF_FLOAT: + case Type::FLOAT: + case Type::DOUBLE: + dtype.code = DLDataTypeCode::kDLFloat; + *out = dtype; + return Status::OK(); + case Type::BOOL: + // DLPack supports byte-packed boolean values + return Status::TypeError("Bit-packed boolean data type not supported by DLPack."); + default: + return Status::TypeError( + "Can only use __dlpack__ on primitive arrays without NullType and Decimal " + "types."); + } +} + +struct DLMTensorCtx { + std::shared_ptr<ArrayData> ref; + std::vector<int64_t> shape; + DLManagedTensor tensor; +}; + +static void deleter(DLManagedTensor* arg) { + delete static_cast<DLMTensorCtx*>(arg->manager_ctx); +} + +Status ExportArray(const std::shared_ptr<Array>& arr, DLManagedTensor** out) { + if (arr->null_count() > 0) { + return Status::TypeError("Can only use __dlpack__ on arrays with no nulls."); + } + + // Define the DLDataType struct + // Supported data types: int, uint, float + DLDataType arr_type; + RETURN_NOT_OK(getDLDataType(arr->type(), &arr_type)); + + // Create DLMTensorCtx struct with the reference to + // the data of the array + std::shared_ptr<ArrayData> array_ref = arr->data(); + DLMTensorCtx* DLMTensor = new DLMTensorCtx; + DLMTensor->ref = array_ref; + + // Define DLManagedTensor struct defined by + // DLPack (dlpack_structure.h) + DLManagedTensor* dlm_tensor = &DLMTensor->tensor; + dlm_tensor->manager_ctx = DLMTensor; + dlm_tensor->deleter = &deleter; + + // Define the data pointer to the DLTensor + // If array is of length 0, data pointer should be NULL Review Comment: That's because most of it wasn't new content, but extensively reviewed over several PRs, including by the lead DLPack maintainer. Digging into the largest of those PRs did help me find the relevant data pointer comment: https://github.com/data-apis/array-api/pull/106#discussion_r557091538: "_it'd be also nice to note if the array is of zero size, in the DLTensor its data pointer should set to nullptr (or 0). In the events where strides are not specified, this is the only effective way to inform the consumer that a zero-size array is coming. Numba/CuPy received a few bug reports when CAI v0/v1 were not clear about this, thus leading to the v2 revision._" I'm not sure that the above is actually true, because there is a `shape` field as well. But checking `data` for being NULL is perhaps easier. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
