swift: add a set of Windows extensions

This adds a new set of API overloads which provide an interface which
use the HANDLE rather than file descriptor.  This makes it easier to
create the dispatch sources without having to convert the file handle to
a file descriptor.

Author: compnerd

src/swift/IO.swift

@@ -11,6 +11,9 @@
 //===----------------------------------------------------------------------===//
 
 import CDispatch
+#if os(Windows)
+import WinSDK
+#endif
 
 extension DispatchIO {
 
@@ -34,12 +37,28 @@ extension DispatchIO {
 		public static let strictInterval = IntervalFlags(rawValue: 1)
 	}
 
+#if os(Windows)
+	public class func read(fromHandle: HANDLE, maxLength: Int, runningHandlerOn queue: DispatchQueue, handler: @escaping (_ data: DispatchData, _ error: Int32) -> Void) {
+		dispatch_read(dispatch_fd_t(bitPattern: fromHandle), maxLength, queue.__wrapped) { (data: dispatch_data_t, error: Int32) in
+			handler(DispatchData(borrowedData: data), error)
+		}
+	}
+#endif
+
 	public class func read(fromFileDescriptor: Int32, maxLength: Int, runningHandlerOn queue: DispatchQueue, handler: @escaping (_ data: DispatchData, _ error: Int32) -> Void) {
 		dispatch_read(dispatch_fd_t(fromFileDescriptor), maxLength, queue.__wrapped) { (data: dispatch_data_t, error: Int32) in
 			handler(DispatchData(borrowedData: data), error)
 		}
 	}
 
+#if os(Windows)
+	public class func write(toHandle: HANDLE, data: DispatchData, runningHandlerOn queue: DispatchQueue, handler: @escaping(_ data: DispatchData??, _ error: Int32) -> Void) {
+		dispatch_write(dispatch_fd_t(bitPattern: toHandle), data.__wrapped.__wrapped, queue.__wrapped) { (data: dispatch_data_t?, error: Int32) in
+			handler(data.map { DispatchData(borrowedData: $0) }, error)
+		}
+	}
+#endif
+
 	public class func write(toFileDescriptor: Int32, data: DispatchData, runningHandlerOn queue: DispatchQueue, handler: @escaping (_ data: DispatchData?, _ error: Int32) -> Void) {
 		dispatch_write(dispatch_fd_t(toFileDescriptor), data.__wrapped.__wrapped, queue.__wrapped) { (data: dispatch_data_t?, error: Int32) in
 			handler(data.map { DispatchData(borrowedData: $0) }, error)

src/swift/Source.swift

@@ -181,6 +181,13 @@ extension DispatchSource {
 	}
 #endif
 
+#if os(Windows)
+	public class func makeReadSource(handle: HANDLE, queue: DispatchQueue? = nil) -> DispatchSourceRead {
+		let source = dispatch_source_create(_swift_dispatch_source_type_READ(), UInt(bitPattern: handle), 0, queue?.__wrapped)
+		return DispatchSource(source: source) as DispatchSourceRead
+	}
+#endif
+
 	public class func makeReadSource(fileDescriptor: Int32, queue: DispatchQueue? = nil) -> DispatchSourceRead {
 #if os(Windows)
 		let handle: UInt = UInt(_get_osfhandle(fileDescriptor))
@@ -224,6 +231,13 @@ extension DispatchSource {
 	}
 #endif
 
+#if os(Windows)
+	public class func makeWriteSource(handle: HANDLE, queue: DispatchQueue? = nil) -> DispatchSourceWrite {
+		let source = dispatch_source_create(_swift_dispatch_source_type_WRITE(), UInt(bitPattern: handle), 0, queue?.__wrapped)
+		return DispatchSource(source: source) as DispatchSourceWrite
+	}
+#endif
+
 	public class func makeWriteSource(fileDescriptor: Int32, queue: DispatchQueue? = nil) -> DispatchSourceWrite {
 #if os(Windows)
 		let handle: UInt = UInt(_get_osfhandle(fileDescriptor))