Fix decoding NSData from an NSCoder

Author: gmilos

Foundation/NSData.swift

@@ -373,10 +373,10 @@ open class NSData : NSObject, NSCopying, NSMutableCopying, NSSecureCoding {
             preconditionFailure("Unkeyed coding is unsupported.")
         }
         if type(of: aDecoder) == NSKeyedUnarchiver.self || aDecoder.containsValue(forKey: "NS.data") {
-            guard let data = aDecoder._decodePropertyListForKey("NS.data") as? NSData else {
+            guard let data = aDecoder._decodePropertyListForKey("NS.data") as? Data else {
                 return nil
             }
-            _init(bytes: UnsafeMutableRawPointer(mutating: data.bytes), length: data.length, copy: true)
+            _init(bytes: UnsafeMutableRawPointer(mutating: data._nsObject.bytes), length: data.count, copy: true)
         } else {
             let result : Data? = aDecoder.withDecodedUnsafeBufferPointer(forKey: "NS.bytes") {
                 guard let buffer = $0 else { return nil }

TestFoundation/TestNSData.swift

@@ -518,6 +518,7 @@ class TestNSData: XCTestCase {
             ("test_validateMutation_slice_customBacking_withUnsafeMutableBytes_lengthLessThanLowerBound", test_validateMutation_slice_customBacking_withUnsafeMutableBytes_lengthLessThanLowerBound),
             ("test_validateMutation_slice_customMutableBacking_withUnsafeMutableBytes_lengthLessThanLowerBound",
              test_validateMutation_slice_customMutableBacking_withUnsafeMutableBytes_lengthLessThanLowerBound),
+            ("test_nskeyedarchiving", test_nskeyedarchiving),
         ]
     }
 
@@ -4140,5 +4141,18 @@ extension TestNSData {
         XCTAssertEqual(data[data.startIndex.advanced(by: 1)], 0xFF)
 #endif
     }
+
+    func test_nskeyedarchiving() {
+        let bytes: [UInt8] = [0xd, 0xe, 0xa, 0xd, 0xb, 0xe, 0xe, 0xf]
+        let data = NSData(bytes: bytes, length: bytes.count)
+
+        let archiver = NSKeyedArchiver()
+        data.encode(with: archiver)
+        let encodedData = archiver.encodedData
+
+        let unarchiver = NSKeyedUnarchiver(forReadingWith: encodedData)
+        let decodedData = NSData(coder: unarchiver)
+        XCTAssertEqual(data, decodedData)
+    }
 }