Extract the creation application version and saved version of an Illustrator file (ai, eps) ref: https://gist.github.com/monokano/8bffac0c07401627c5a1ebf020b93b0e

aiver.swift

import Cocoa

/// ファイルを指定されたバイト数分ずつ読み込む
final class StreamReader: NSObject, StreamDelegate {
    let maxLength: Int
    let inputStream: InputStream?
    var readedAction: (Versions) -> Void = { _ in }

    var createVersion = ""
    var saveVersion = ""

    init(filePath: String, maxLength: Int) {
        self.maxLength = maxLength
        self.inputStream = InputStream(fileAtPath: filePath)
        super.init()
        inputStream?.delegate = self
    }

    func start(readedAction: @escaping (Versions) -> Void) {
        self.readedAction = readedAction
        inputStream?.schedule(in: RunLoop.current, forMode: .default)
        inputStream?.open()
    }

    func stop() {
        inputStream?.close()
    }

    func stream(_ aStream: Stream, handle eventCode: Stream.Event) {
        switch eventCode {
        case .openCompleted:
            ()
        case .hasBytesAvailable:
            guard let inputStream = inputStream else {
                self.inputStream?.close()
                return
            }
            var buffer = [UInt8](repeating: 0, count: maxLength)
            while inputStream.hasBytesAvailable {
                let result = inputStream.read(&buffer, maxLength: buffer.capacity)
                if result > 0 {
                    let save = extractString(from: Data(buffer),
                                             prefix: "%%Creator: Adobe Illustrator(R)",
                                             suffix:  "%%AI8_CreatorVersion:")
                    let create = extractString(from: Data(buffer),
                                               prefix: "AI8_CreatorVersion:",
                                               suffix: "%%For")
                    if !save.isEmpty {
                        saveVersion = save
                    }
                    if !create.isEmpty {
                        saveVersion = create
                    }
                    if !save.isEmpty, !create.isEmpty {
                        // 作成バージョンと保存バージョンを抽出できたらクロージャを実行
                        readedAction(Versions(createVersion: create, saveVersion: save))
                        // ストリームを閉じる
                        self.inputStream?.close()
                    }
                }
            }
        case .errorOccurred:
            inputStream?.close()
        case .endEncountered:
            inputStream?.close()
        default:
            inputStream?.close()
        }
    }

    /// 渡された2つの文字列の間の文字を取り出す
    func extractString(from data: Data, prefix: String, suffix: String) -> String {
        guard let prefixData = prefix.data(using: .utf8),
              let suffixData = suffix.data(using: .utf8),
        let prefixRange = data.range(of: prefixData),
        let suffixRange = data.range(of: suffixData) else { return "" }

        // prefixの文字列のrangeの最後のIndexの一文字先の文字のindex
        let startIndex = prefixRange.endIndex + 1
        // prefixの文字列のrangeの最初のIndexの一文字前の文字のindex
        let endIndex = suffixRange.startIndex - 1

        let verStrData = data.subdata(in: startIndex ..< endIndex)

        return String(data: verStrData, encoding: .utf8) ?? ""
    }
}

/// バージョンを格納する構造体
struct Versions {
    let createVersion: String
    let saveVersion: String

    var description: String {
        return "createVersion: \(createVersion) saveVersion: \(saveVersion)"
    }
}

let filePath = "(file_path)"

// 10MBずつ読み込む
let kb = 1024 * 1024 * 1
let steramReader = StreamReader(filePath: filePath, maxLength: kb)
steramReader.start { result in
    // とりだしたバージョンを出力する
    print(result.description)
}

// createVersion: 24.2.3 saveVersion: 24.0