Fix locking in requests, os_unfair_lock not to be directly used in Sw…

…ift (#429)

Source/SwiftyDropbox/Shared/Handwritten/Request+TokenRefresh.swift

@@ -70,16 +70,25 @@ protocol RequestControlling {
 class RequestWithTokenRefresh: ApiRequest {
     class StateAccess {
         private var mutableState: MutableState
-        private var lock = os_unfair_lock()
+        private var lock = { // heap allocate the lock for use in Swift
+            let lock = UnsafeMutablePointer<os_unfair_lock>.allocate(capacity: 1)
+            lock.initialize(to: .init())
+            return lock
+        }()
 
         init(mutableState: MutableState) {
             self.mutableState = mutableState
         }
 
+        deinit {
+            lock.deinitialize(count: 1)
+            lock.deallocate()
+        }
+
         fileprivate func accessStateWithLock<T>(block: (MutableState) throws -> T) rethrows -> T {
-            try lock.sync {
-                try block(mutableState)
-            }
+            os_unfair_lock_lock(lock)
+            defer { os_unfair_lock_unlock(lock) }
+            return try block(mutableState)
         }
     }
 

Source/SwiftyDropbox/Shared/Handwritten/Utilities.swift

@@ -86,16 +86,6 @@ extension Optional where Wrapped: SomeOptional {
     }
 }
 
-// MARK: Concurrency
-
-public extension os_unfair_lock {
-    mutating func sync<T>(execute: () throws -> T) rethrows -> T {
-        os_unfair_lock_lock(&self)
-        defer { os_unfair_lock_unlock(&self) }
-        return try execute()
-    }
-}
-
 // MARK: Logging
 
 public enum LogLevel {