Sources/SparkConnect/ArrowBuffer.swift

// 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

/// @nodoc
public class ArrowBuffer {
  static let minLength: UInt = 1 << 5
  static let maxLength = UInt.max
  fileprivate(set) var length: UInt
  let capacity: UInt
  public let rawPointer: UnsafeMutableRawPointer
  let isMemoryOwner: Bool

  init(
    length: UInt, capacity: UInt, rawPointer: UnsafeMutableRawPointer, isMemoryOwner: Bool = true
  ) {
    self.length = length
    self.capacity = capacity
    self.rawPointer = rawPointer
    self.isMemoryOwner = isMemoryOwner
  }

  deinit {
    if isMemoryOwner {
      self.rawPointer.deallocate()
    }
  }

  func append(to data: inout Data) {
    let ptr = UnsafePointer(rawPointer.assumingMemoryBound(to: UInt8.self))
    data.append(ptr, count: Int(capacity))
  }

  static func createEmptyBuffer() -> ArrowBuffer {
    return ArrowBuffer(
      length: 0,
      capacity: 0,
      rawPointer: UnsafeMutableRawPointer.allocate(byteCount: 0, alignment: .zero))
  }

  static func createBuffer(_ data: [UInt8], length: UInt) -> ArrowBuffer {
    let byteCount = UInt(data.count)
    let capacity = alignTo64(byteCount)
    let memory = MemoryAllocator(64)
    let rawPointer = memory.allocateArray(Int(capacity))
    rawPointer.copyMemory(from: data, byteCount: data.count)
    return ArrowBuffer(length: length, capacity: capacity, rawPointer: rawPointer)
  }

  static func createBuffer(_ length: UInt, size: UInt, doAlign: Bool = true) -> ArrowBuffer {
    let actualLen = max(length, ArrowBuffer.minLength)
    let byteCount = size * actualLen
    var capacity = byteCount
    if doAlign {
      capacity = alignTo64(byteCount)
    }

    let memory = MemoryAllocator(64)
    let rawPointer = memory.allocateArray(Int(capacity))
    rawPointer.initializeMemory(as: UInt8.self, repeating: 0, count: Int(capacity))
    return ArrowBuffer(length: length, capacity: capacity, rawPointer: rawPointer)
  }

  static func copyCurrent(_ from: ArrowBuffer, to: inout ArrowBuffer, len: UInt) {
    to.rawPointer.copyMemory(from: from.rawPointer, byteCount: Int(len))
  }

  private static func alignTo64(_ length: UInt) -> UInt {
    let bufAlignment = length % 64
    if bufAlignment != 0 {
      return length + (64 - bufAlignment) + 8
    }

    return length + 8
  }
}