Xamarin Blueprints

Creating the AsyncSemaphore

Let's add a new folder called Threading to the FileStorage.Portable project. Inside this folder, we are going to add a new file called AsyncSemaphore.cs and implement the first part as follows:

public class AsyncSemaphore { private readonly static Task s_completed = Task.FromResult(true); private readonly Queue<TaskCompletionSource<bool>> m_waiters = new Queue<TaskCompletionSource<bool>>(); private int m_currentCount; public AsyncSemaphore(int initialCount) { if (initialCount < 0) throw new ArgumentOutOfRangeException("initialCount"); m_currentCount = initialCount; } public Task WaitAsync() { lock (m_waiters) { if (m_currentCount > 0) { --m_currentCount; return s_completed; } else { var waiter = new TaskCompletionSource<bool>(); ...