將NSData轉換爲swift中的sockaddr結構體

Question

我試圖在swift中做一個簡單的DNS查找。到目前爲止，這裏是我的代碼：

let hostRef = CFHostCreateWithName(kCFAllocatorDefault, "google.com").takeRetainedValue() 
var resolved = CFHostStartInfoResolution(hostRef, CFHostInfoType.Addresses, nil) 
let addresses = CFHostGetAddressing(hostRef, &resolved).takeRetainedValue() as NSArray 

在這一點上，每一個元素中的「地址」的NSArray是一個CFDataRef對象包裝一個套接字地址結構。

由於CFDataRef可撥打免費電話橋接NSData的，我可以通過他們循環，像這樣：

for address: AnyObject in addresses { 
    println(address) // address is of type NSData. 
} 

到目前爲止好（我認爲）。當我在單元測試中運行它時打印出有效的外觀數據。這裏是我卡住的地方。對於我的生活，我無法弄清楚如何將NSData對象中的字節轉換爲sockaddr結構體。

如何將address.bytes（類型爲COpaquePointer？）轉換爲c結構？任何幫助讚賞。試圖弄清楚這一點，我正在撞牆。

Answer 1

您可以使用NSData的方法getBytes(_, length:)方法和使用前綴&運營商的sockaddr結構傳遞到INOUT參數：

var data: NSData ... 
var address: sockaddr ... 

data.getBytes(&address, length: MemoryLayout<sockaddr>.size) 

更新了斯威夫特3：

let host = CFHostCreateWithName(kCFAllocatorDefault, "google.com" as CFString).takeRetainedValue() 
var resolved = DarwinBoolean(CFHostStartInfoResolution(host, .addresses, nil)) 
let addresses = CFHostGetAddressing(host, &resolved)?.takeUnretainedValue() as! [NSData]? 

if let data = addresses?.first { 
    var storage = sockaddr_storage() 
    data.getBytes(&storage, length: MemoryLayout<sockaddr_storage>.size) 

    if Int32(storage.ss_family) == AF_INET { 
     let addr4 = withUnsafePointer(to: &storage) { 
      $0.withMemoryRebound(to: sockaddr_in.self, capacity: 1) { 
       $0.pointee 
      } 
     } 

     // prints 74.125.239.132 
     print(String(cString: inet_ntoa(addr4.sin_addr), encoding: .ascii)) 
    } 
} 

---

2015年6月3日更新： 現在，C中的結構可以很容易地初始化爲零，這變得簡單多了：

let host = CFHostCreateWithName(kCFAllocatorDefault, "google.com").takeRetainedValue() 
var resolved = CFHostStartInfoResolution(host, .Addresses, nil) 
let addresses = CFHostGetAddressing(host, &resolved)?.takeUnretainedValue() as! [NSData]? 

if let data = addresses?.first { 
    var storage = sockaddr_storage() 
    data.getBytes(&storage, length: sizeof(sockaddr_storage)) 

    if Int32(storage.ss_family) == AF_INET { 
     let addr4 = withUnsafePointer(&storage) { UnsafePointer<sockaddr_in>($0).memory } 

     // prints 74.125.239.132 
     println(String(CString: inet_ntoa(addr4.sin_addr), encoding: NSASCIIStringEncoding)) 
    } 
} 

---

不幸的是，這需要 sockaddr首先被初始化。爲了避免這種情況，你可以做這樣的事情：

func makeWithUnsafePointer<T>(body: UnsafePointer<T> ->()) -> T { 
    let ptr = UnsafePointer<T>.alloc(sizeof(T)) 
    body(ptr) 
    return ptr.move() 
} 

let addr: sockaddr = makeWithUnsafePointer { 
    data.getBytes($0 as UnsafePointer<sockaddr>, length: sizeof(sockaddr)) 
} 

或者這樣：

func makeWithUninitialized<T>(body: inout T ->()) -> T { 
    let ptr = UnsafePointer<T>.alloc(sizeof(T)) 
    body(&ptr.memory) 
    return ptr.move() 
} 

let addr = makeWithUninitialized { (inout addr: sockaddr) in 
    data.getBytes(&addr, length: sizeof(sockaddr)) 
} 

更多的討論，參見 Swift: Pass Uninitialized C Structure to Imported C function