获取UnsafePointer <UInt8> 将Int写入流中

Question

如何获得指向数字变量的指针？ 例如，转换将获得一个UnsafePointer<UInt8> ，它指向包含Swift Int的存储。 我需要将Int写入流中。

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)
}

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

Answer 1

与withUnsafePointer使用，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，它将以低字节序写入字节（因为当前运行Swift的所有平台都是低字节序）。 如果要使用big-endian编写，请使用encodedDataArray.count.bigEndian 。