NIO: implement address resolution on Windows (#1684)

Windows has a slightly different API for address resolution.  Implement
the Windows path for addrinfo resolution.

Sources/NIO/GetaddrinfoResolver.swift

@@ -23,6 +23,21 @@
 /// This resolver is a single-use object: it can only be used to perform a single host resolution.
 import CNIOLinux
 
+#if os(Windows)
+import let WinSDK.AF_INET
+import let WinSDK.AF_INET6
+
+import func WinSDK.FreeAddrInfoW
+import func WinSDK.GetAddrInfoW
+import func WinSDK.gai_strerrorA
+
+import struct WinSDK.ADDRESS_FAMILY
+import struct WinSDK.ADDRINFOW
+import struct WinSDK.SOCKADDR_IN
+import struct WinSDK.SOCKADDR_IN6
+#endif
+
+
 internal class GetaddrinfoResolver: Resolver {
     private let v4Future: EventLoopPromise<[SocketAddress]>
     private let v6Future: EventLoopPromise<[SocketAddress]>
@@ -85,6 +100,30 @@ internal class GetaddrinfoResolver: Resolver {
     ///     - host: The hostname to do the DNS queries on.
     ///     - port: The port we'll be connecting to.
     private func resolve(host: String, port: Int) {
+#if os(Windows)
+        host.withCString(encodedAs: UTF16.self) { wszHost in
+            String(port).withCString(encodedAs: UTF16.self) { wszPort in
+                var pResult: UnsafeMutablePointer<ADDRINFOW>?
+
+                var aiHints: ADDRINFOW = ADDRINFOW()
+                aiHints.ai_socktype = self.aiSocktype.rawValue
+                aiHints.ai_protocol = self.aiProtocol
+
+                let iResult = GetAddrInfoW(wszHost, wszPort, &aiHints, &pResult)
+                guard iResult == 0 else {
+                    self.fail(SocketAddressError.unknown(host: host, port: port))
+                    return
+                }
+
+                if let pResult = pResult {
+                    parseResults(pResult, host: host)
+                    FreeAddrInfoW(pResult)
+                } else {
+                    self.fail(SocketAddressError.unsupported)
+                }
+            }
+        }
+#else
         var info: UnsafeMutablePointer<addrinfo>?
 
         var hint = addrinfo()
@@ -102,6 +141,7 @@ internal class GetaddrinfoResolver: Resolver {
             /* this is odd, getaddrinfo returned NULL */
             self.fail(SocketAddressError.unsupported)
         }
+#endif
     }
 
     /// Parses the DNS results from the `addrinfo` linked list.
@@ -109,11 +149,17 @@ internal class GetaddrinfoResolver: Resolver {
     /// - parameters:
     ///     - info: The pointer to the first of the `addrinfo` structures in the list.
     ///     - host: The hostname we resolved.
-    private func parseResults(_ info: UnsafeMutablePointer<addrinfo>, host: String) {
+#if os(Windows)
-        var info = info
+    internal typealias CAddrInfo = ADDRINFOW
-        var v4Results = [SocketAddress]()
+#else
-        var v6Results = [SocketAddress]()
+    internal typealias CAddrInfo = addrinfo
+#endif
 
+    private func parseResults(_ info: UnsafeMutablePointer<CAddrInfo>, host: String) {
+        var v4Results: [SocketAddress] = []
+        var v6Results: [SocketAddress] = []
+
+        var info: UnsafeMutablePointer<CAddrInfo> = info
         while true {
             switch NIOBSDSocket.AddressFamily(rawValue: info.pointee.ai_family) {
             case .inet:

Sources/NIO/SocketAddresses.swift

@@ -339,7 +339,7 @@ public enum SocketAddress: CustomStringConvertible {
             return try String(port).withCString(encodedAs: UTF16.self) { wszPort in
                 var pResult: UnsafeMutablePointer<ADDRINFOW>?
 
-                guard GetAddrInfoW(wsHost, wszPort, nil, &pResult) == 0 else {
+                guard GetAddrInfoW(wszHost, wszPort, nil, &pResult) == 0 else {
                     throw SocketAddressError.unknown(host: host, port: port)
                 }