abandy commented on code in PR #39091: URL: https://github.com/apache/arrow/pull/39091#discussion_r1492397040
########## swift/Arrow/Sources/Arrow/ArrowCImporter.swift: ########## @@ -0,0 +1,144 @@ +// 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. + +import Foundation +import ArrowC + +public class ArrowCImporter { + private func appendToBuffer( + _ cBuffer: UnsafeRawPointer?, + arrowBuffers: inout [ArrowBuffer], + byteCount: Int, + length: UInt, + nullCount: UInt? = nil) { + if cBuffer == nil { + arrowBuffers.append(ArrowBuffer.createEmptyBuffer()) + return + } + + let pointer = UnsafeMutableRawPointer(mutating: cBuffer)! + arrowBuffers.append( + ArrowBuffer(length: length, capacity: UInt(byteCount), rawPointer: pointer, isMemoryOwner: false)) + } + + public init() {} + + public func importType(_ cArrow: String, name: String = "") -> + Result<ArrowField, ArrowError> { + do { + let type = try ArrowType.fromCDataFormatId(cArrow) + return .success(ArrowField(name, type: ArrowType(type.info), isNullable: true)) + } catch { + return .failure(.invalid("\(error)")) + } + } + + public func importField(_ cSchema: ArrowC.ArrowSchema) -> + Result<ArrowField, ArrowError> { + if cSchema.n_children > 0 { + return .failure(.invalid("Children currently not supported")) + } else if cSchema.dictionary != nil { + return .failure(.invalid("Dictinoary types currently not supported")) + } + + switch importType( + String(cString: cSchema.format), name: String(cString: cSchema.name)) { + case .success(let field): + release(cSchema) + return .success(field) + case .failure(let err): + return .failure(err) + } + } + + public func importArray( + _ cArray: ArrowC.ArrowArray, + arrowType: ArrowType, + isNullable: Bool = false) -> Result<ArrowArrayHolder, ArrowError> { + let arrowField = ArrowField("", type: arrowType, isNullable: isNullable) + return importArray(cArray, arrowField: arrowField) + } + + public func importArray( + _ cArray: ArrowC.ArrowArray, + arrowField: ArrowField) -> Result<ArrowArrayHolder, ArrowError> { + if cArray.null_count < 0 { + return .failure(.invalid("Uncomputed null count is not supported")) + } else if cArray.n_children > 0 { + return .failure(.invalid("Children currently not supported")) + } else if cArray.dictionary != nil { + return .failure(.invalid("Dictionary types currently not supported")) + } else if cArray.offset != 0 { + return .failure(.invalid("Offset of 0 is required but found offset: \(cArray.offset)")) + } + + let arrowType = arrowField.type + let length = UInt(cArray.length) + let nullCount = UInt(cArray.null_count) + let nullBytes = Int(ceil(Double(length) / 8)) + var arrowBuffers = [ArrowBuffer]() + + if cArray.n_buffers > 0 { + if cArray.buffers == nil { + return .failure(.invalid("C array buffers is nil")) + } + + switch arrowType.info { + case .variableInfo: + if cArray.n_buffers != 3 { + return .failure( + .invalid("Variable buffer count expected 3 but found \(cArray.n_buffers)")) + } + + appendToBuffer(cArray.buffers[0], arrowBuffers: &arrowBuffers, byteCount: nullBytes, length: length, + nullCount: nullCount) + let byteCount = MemoryLayout<Int32>.stride * Int(length + 1) + appendToBuffer(cArray.buffers[1], arrowBuffers: &arrowBuffers, byteCount: byteCount, length: length) + let offsetIndex = MemoryLayout<Int32>.stride * Int(length - 1) + let endIndex = arrowBuffers[1].rawPointer.advanced(by: offsetIndex).load(as: Int32.self) + appendToBuffer(cArray.buffers[2], arrowBuffers: &arrowBuffers, byteCount: Int(endIndex), length: length) + default: + if cArray.n_buffers != 2 { + return .failure(.invalid("Expected buffer count 2 but found \(cArray.n_buffers)")) + } + + appendToBuffer(cArray.buffers[0], arrowBuffers: &arrowBuffers, byteCount: nullBytes, length: length, + nullCount: nullCount) + let byteCount = arrowType.getStride() * Int(length) + appendToBuffer(cArray.buffers[1], arrowBuffers: &arrowBuffers, byteCount: byteCount, length: length) + } + } + + return makeArrayHolder(arrowField, buffers: arrowBuffers, nullCount: nullCount) Review Comment: Hi @pitrou, gotcha, thank you for the detailed explanation! I have updated the code to return a wrapped ArrayHolder that will manage releasing the memory associated with the C array. I think this will resolve the issue. Also, I altered the arrayToSwift go test to check if released was called to ensure memory was deallocated. This is not as comprehensive as the test description above but it is a sanity check. I will follow up with a future task to make this more robust as you have explained. Let me know if this works. -- 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]
