Moving headers into include/sls (#212)

slsReceiverSoftware/include/sls/CircularFifo.h

@@ -0,0 +1,129 @@
+#pragma once
+/* CircularFifo.h
+ * Code & platform dependent issues with it was originally
+ * published at http://www.kjellkod.cc/threadsafecircularqueue
+ * 2009-11-02
+ * @author Kjell Hedstr<74>m, hedstrom@kjellkod.cc
+ * modified by the sls detector group
+ * */
+
+#include <iostream>
+#include <semaphore.h>
+#include <vector>
+
+/** Circular Fifo (a.k.a. Circular Buffer)
+ * Thread safe for one reader, and one writer */
+template <typename Element> class CircularFifo {
+  private:
+    size_t tail{0};
+    size_t head{0};
+    size_t capacity;
+    std::vector<Element *> data;
+    mutable sem_t data_mutex;
+    mutable sem_t free_mutex;
+    size_t increment(size_t i) const;
+
+  public:
+    explicit CircularFifo(size_t size) : capacity(size + 1), data(capacity) {
+        sem_init(&data_mutex, 0, 0);
+        sem_init(&free_mutex, 0, size);
+    }
+
+    CircularFifo(const CircularFifo &) = delete;
+    CircularFifo(CircularFifo &&) = delete;
+
+    virtual ~CircularFifo() {
+        sem_destroy(&data_mutex);
+        sem_destroy(&free_mutex);
+    }
+
+    bool push(Element *&item, bool no_block = false);
+    bool pop(Element *&item, bool no_block = false);
+
+    bool isEmpty() const;
+    bool isFull() const;
+
+    int getDataValue() const;
+    int getFreeValue() const;
+};
+
+template <typename Element> int CircularFifo<Element>::getDataValue() const {
+    int value;
+    sem_getvalue(&data_mutex, &value);
+    return value;
+}
+
+template <typename Element> int CircularFifo<Element>::getFreeValue() const {
+    int value;
+    sem_getvalue(&free_mutex, &value);
+    return value;
+}
+
+/** Producer only: Adds item to the circular queue.
+ * If queue is full at 'push' operation no update/overwrite
+ * will happen, it is up to the caller to handle this case
+ *
+ * \param item copy by reference the input item
+ * \param no_block if true, return immediately if fifo is full
+ * \return whether operation was successful or not */
+template <typename Element>
+bool CircularFifo<Element>::push(Element *&item, bool no_block) {
+    // check for fifo full
+    if (no_block && isFull())
+        return false;
+
+    sem_wait(&free_mutex);
+    data[tail] = item;
+    tail = increment(tail);
+    sem_post(&data_mutex);
+    return true;
+}
+
+/** Consumer only: Removes and returns item from the queue
+ * If queue is empty at 'pop' operation no retrieve will happen
+ * It is up to the caller to handle this case
+ *
+ * \param item return by reference the wanted item
+ * \param no_block if true, return immediately if fifo is full
+ * \return whether operation was successful or not */
+template <typename Element>
+bool CircularFifo<Element>::pop(Element *&item, bool no_block) {
+    // check for fifo empty
+    if (no_block && isEmpty())
+        return false;
+
+    sem_wait(&data_mutex);
+    item = data[head];
+    head = increment(head);
+    sem_post(&free_mutex);
+    return true;
+}
+
+/** Useful for testing and Consumer check of status
+ * Remember that the 'empty' status can change quickly
+ * as the Producer adds more items.
+ *
+ * \return true if circular buffer is empty */
+template <typename Element> bool CircularFifo<Element>::isEmpty() const {
+    return (getDataValue() == 0);
+}
+
+/** Useful for testing and Producer check of status
+ * Remember that the 'full' status can change quickly
+ * as the Consumer catches up.
+ *
+ * \return true if circular buffer is full.  */
+template <typename Element> bool CircularFifo<Element>::isFull() const {
+    return (getFreeValue() == 0);
+}
+
+/** Increment helper function for index of the circular queue
+ * index is incremented or wrapped
+ *
+ *  \param i the index to the incremented/wrapped
+ *  \return new value for the index */
+template <typename Element>
+size_t CircularFifo<Element>::increment(size_t i) const {
+    i = (i + 1) % capacity;
+    return i;
+}