- Add new ESP-NOW mesh backend.

- Add HelloEspnow.ino example to demonstrate the ESP-NOW mesh backend features.

- Deprecate the ESP8266WiFiMesh class in favour of the new ESP-NOW and TCP/IP backends.

- Update the TCP/IP mesh backend to use the new lwIP version preprocessor flag and remove obsolete preprocessor flags.

libraries/ESP8266WiFiMesh/src/MutexTracker.h

@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2019 Anders Löfgren
+ *
+ * License (MIT license):
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef __MUTEXTRACKER_H__
+#define __MUTEXTRACKER_H__
+
+#include <functional>
+
+/**
+ * A SLIM (Scope LImited Manager)/Scope-Bound Resource Management/RAII class to manage the state of a mutex.
+ */
+class MutexTracker
+{
+  public:
+
+    /**
+    * Attempts to capture the mutex. Use the mutexCaptured() method to check success.
+    */
+    MutexTracker(bool &mutexToCapture);
+
+    /**
+    * Attempts to capture the mutex. Use the mutexCaptured() method to check success.
+    * 
+    * @param destructorHook A function to hook into the MutexTracker destructor. Will be called when the MutexTracker instance is being destroyed, after the mutex has been released.
+    */
+    MutexTracker(bool &mutexToCapture, std::function<void()> destructorHook);
+
+    ~MutexTracker();
+
+    bool mutexCaptured();
+
+    /**
+     * Set the mutex free to roam the binary plains, giving new MutexTrackers a chance to capture it.
+     */
+    void releaseMutex();
+
+  private:
+
+    bool *_capturedMutex = nullptr;
+    std::function<void()> _destructorHook = [](){ };
+
+    /**
+     * Attempt to capture the mutex.
+     * 
+     * @returns True if mutex was caught (meaning no other instance is holding the mutex). False otherwise.
+     */
+    bool attemptMutexCapture(bool &mutexToCapture);
+};
+
+#endif