Enhanced circular_queue from EspSoftwareSerial.

Author: dok-net

libraries/FastScheduler/src/circular_queue/circular_queue.h

@@ -123,19 +123,35 @@ class circular_queue
     }
 
     /*!
-        @brief	Peek at the next element pop returns without removing it from the queue.
-        @return An rvalue copy of the next element that can be popped, or a default
-                value of type T if the queue is empty.
+        @brief	Peek at the next element pop will return without removing it from the queue.
+        @return An rvalue copy of the next element that can be popped. If the queue is empty,
+                return an rvalue copy of the element that is pending the next push.
     */
     T peek() const
     {
-        const auto outPos = m_outPos.load(std::memory_order_acquire);
+        const auto outPos = m_outPos.load(std::memory_order_relaxed);
+        std::atomic_thread_fence(std::memory_order_acquire);
+        return m_buffer[outPos];
+    }
+
+    /*!
+        @brief	Peek at the next pending input value.
+        @return A reference to the next element that can be pushed.
+    */
+    T& IRAM_ATTR pushpeek()
+    {
         const auto inPos = m_inPos.load(std::memory_order_relaxed);
         std::atomic_thread_fence(std::memory_order_acquire);
-        if (inPos == outPos) return defaultValue;
-        else return m_buffer[outPos];
+        return m_buffer[inPos];
     }
 
+    /*!
+        @brief	Release the next pending input value, accessible by pushpeek(), into the queue.
+        @return true if the queue accepted the value, false if the queue
+                was full.
+    */
+    bool IRAM_ATTR push();
+
     /*!
         @brief	Move the rvalue parameter into the queue.
         @return true if the queue accepted the value, false if the queue
@@ -212,6 +228,21 @@ bool circular_queue<T>::capacity(const size_t cap)
     return true;
 }
 
+template< typename T >
+bool IRAM_ATTR circular_queue<T>::push()
+{
+    const auto inPos = m_inPos.load(std::memory_order_acquire);
+    const unsigned next = (inPos + 1) % m_bufSize;
+    if (next == m_outPos.load(std::memory_order_relaxed)) {
+        return false;
+    }
+
+    std::atomic_thread_fence(std::memory_order_acquire);
+
+    m_inPos.store(next, std::memory_order_release);
+    return true;
+}
+
 template< typename T >
 bool IRAM_ATTR circular_queue<T>::push(T&& val)
 {

libraries/FastScheduler/src/circular_queue/circular_queue_mp.h

@@ -71,6 +71,14 @@ class circular_queue_mp : protected circular_queue<T>
         return circular_queue<T>::capacity(cap);
     }
 
+    bool IRAM_ATTR push() = delete;
+
+    /*!
+        @brief	Move the rvalue parameter into the queue, guarded
+                for multiple concurrent producers.
+        @return true if the queue accepted the value, false if the queue
+                was full.
+    */
     bool IRAM_ATTR push(T&& val)
     {
 #ifdef ESP8266
@@ -82,7 +90,7 @@ class circular_queue_mp : protected circular_queue<T>
     }
 
     /*!
-        @brief	Move the rvalue parameter into the queue, guarded
+        @brief	Push a copy of the parameter into the queue, guarded
                 for multiple concurrent producers.
         @return true if the queue accepted the value, false if the queue
                 was full.