ios - 将 UnsafePointer<UInt8> 获取到 Int 以将编码的 Int 写入流

Question

如何获得指向数字变量的指针？例如。转换得到 UnsafePointer<UInt8>指向包含 Swift Int 的存储.我需要写 Int到一个流。

我的例子:

public static func writeToOutputStream(text: String!, outputStream:NSOutputStream!){
    let encodedDataArray = [UInt8](text.utf8)
    //send length of the data so the server knows when the message ends.
    outputStream.write(encodedDataArray.count, maxLength: 4)
    outputStream.write(encodedDataArray, maxLength: encodedDataArray.count)
}

我需要 encodedDataArray.count成为UnsafePointer<UInt8>如果我也想发送数据长度。

Answer 1

使用withUnsafePointer，像这样:

let outputStream = NSOutputStream(toMemory: ())
outputStream.open()

var count: Int = 0x01020304 // = encodedDataArray.count in your program
withUnsafePointer(&count) { (pointer: UnsafePointer<Int>) -> Void in
    outputStream.write(UnsafePointer<UInt8>(pointer), maxLength: 4)
}

outputStream.propertyForKey(NSStreamDataWrittenToMemoryStreamKey)

结果:

<04030201>

请注意，它将以小端顺序写入字节(因为 Swift 当前运行的所有平台都是小端)。如果您想以大端方式写入，请使用 encodedDataArray.count.bigEndian。