获取NonafePointer <uint8>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的存储空间。我需要将Int写入流。

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)
}

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

Answer 1

使用withUnsafePointer，如下所示：

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little-endian顺序写入字节（因为Swift当前运行的所有平台都是little-endian）。如果您想用big-endian编写，请使用encodedDataArray.count.bigEndian。