内存泄漏，我的问题可能与指针有关吗？

Question

iOS 12.x Swift 5

我正在使用套接字与另一个盒子通信，我编写了这段代码，我认为这很有意义。但我想咨询专家。我问是因为我认为这个应用程序存在某种内存泄漏。我怀疑指针，就像你一样。我正在观察它使用的内存在我运行时慢慢增加。

func sendMessage(message: String) {

    let data = message.data(using: String.Encoding.utf8, allowLossyConversion: false)!
    let dataMutablePointer = UnsafeMutablePointer<UInt8>.allocate(capacity: data.count)
    //Copies the bytes to the Mutable Pointer

    dataMutablePointer.initialize(to: 0)
    data.copyBytes(to: dataMutablePointer, count: data.count)

    //Cast to regular UnsafePointer
    let dataPointer = UnsafePointer<UInt8>(dataMutablePointer)

    //Your stream
    outputStream.write(dataPointer, maxLength: data.count)
    defer {
      dataMutablePointer.deinitialize(count: data.count)
    }
}

这段代码看起来正常吗？这可能是我的内存泄漏的根源吗？我需要取消初始化这个指针吗？

Answer 1

这可能是我的内存泄漏的根源吗？

是的，当然。

我需要取消初始化这个指针吗？

正如 bscothern 所评论的，如果 Pointee 是非平凡类型，则需要取消指针的初始化。但对于UInt8，则不是强制性的。

但您最终需要释放指针。

你的代码应该是这样的：

func sendMessage(message: String) {

    let data = message.data(using: String.Encoding.utf8, allowLossyConversion: false)!
    let dataMutablePointer = UnsafeMutablePointer<UInt8>.allocate(capacity: data.count)
    defer {
        dataMutablePointer.deallocate()
    }

    //Copies the bytes to the Mutable Pointer
    dataMutablePointer.initialize(to: 0)
    defer {
        //This is not required, but you can put `deinitialize` here if you prefer
        dataMutablePointer.deinitialize(count: data.count)
    }
    data.copyBytes(to: dataMutablePointer, count: data.count)

    //Cast to regular UnsafePointer
    let dataPointer = UnsafePointer<UInt8>(dataMutablePointer)

    //Your stream
    outputStream.write(dataPointer, maxLength: data.count)
}

defer 将其块的执行推迟到封闭块的末尾，因此 dataMutablePointer.deallocate() 将在 outputStream.write(dataPointer, maxLength: data.count) 完成后执行。

但我会在不复制数据的情况下写一些等效的东西：

func sendMessage(message: String) {

    let data = message.data(using: String.Encoding.utf8, allowLossyConversion: false)!

    data.withUnsafeBytes {bytes in
        let dataPointer = bytes.baseAddress!.assumingMemoryBound(to: UInt8.self)
        //Your stream
        outputStream.write(dataPointer, maxLength: data.count)
    }
}

或者，更简单地说：

func sendMessage(message: String) {
    //Your stream
    outputStream.write(message, maxLength: message.utf8.count)
}