获取UnsafePointer <UInt8> 将Int写入流中

Question

How do you get a pointer to a number variable? Eg convert get an UnsafePointer<UInt8> that points to the storage containing a Swift Int . I need to write the Int to a stream.

My example:

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)
}

I need encodedDataArray.count to be an UnsafePointer<UInt8> if I want to send the data length too.

Answer 1

Use withUnsafePointer , like this:

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)

Result:

<04030201>

Note that it'll write the bytes in little-endian order (because all platforms on which Swift currently runs are little-endian). If you want to write in big-endian, use encodedDataArray.count.bigEndian .