compression.swift

// https://developer.apple.com/documentation/accelerate/compressing_and_decompressing_data_with_input_and_output_filters

import Compression

let sourceString = """
    Lorem ipsum dolor sit amet consectetur adipiscing elit mi
    nibh ornare proin blandit diam ridiculus, faucibus mus
    dui eu vehicula nam donec dictumst sed vivamus bibendum
    aliquet efficitur. Felis imperdiet sodales dictum morbi
    vivamus augue dis duis aliquet velit ullamcorper porttitor,
    lobortis dapibus hac purus aliquam natoque iaculis blandit
    montes nunc pretium.
    """

let sourceData = Data(sourceString.utf8)

let pageSize = 128

var compressedData = Data()

do {
  let outputFilter = try OutputFilter(.compress, using: .lzfse, writingTo: { data in
    if let data = data {
      compressedData.append(data)
    }
  })

  var index = 0
  let bufferSize = sourceData.count

  while true {
    let rangeLength = min(pageSize, bufferSize - index)

    let subdata = sourceData.subdata(in: index..<index + rangeLength)
    index += rangeLength

    try outputFilter.write(subdata)

    if rangeLength == 0 {
      break
    }
  }
} catch {
  fatalError("ENCODING \(error.localizedDescription)")
}

var decompressedData = Data()

do {
  var index = 0
  let bufferSize = compressedData.count

  let inputFilter = try InputFilter(.decompress, using: .lzfse) { length -> Data in
    let rangeLength = min(length, bufferSize - index)
    let subdata = compressedData.subdata(in: index..<index + rangeLength)
    index += rangeLength

    return subdata
  }

  while let page = try inputFilter.readData(ofLength: pageSize) {
    decompressedData.append(page)
  }
} catch {
  fatalError("DECODING \(error.localizedDescription)")
}

let decompressedString = String(data: decompressedData, encoding: .utf8)

decompressedString == sourceString