ringbuffer.h

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#ifndef QueueRingBufferH
#define QueueRingBufferH
 
template <class T>
class queueRingBuffer
{
  template <class A>
  struct link
  {
    link ( const A &val )
      :value(val)
    {}
    A value;
    link *nextLink;
    link *prevLink;
  };
 
  link<T> *lastFilled;
  link<T> *lastFree;
  unsigned int max;
  int count;
public:
  queueRingBuffer( unsigned int max );
  ~queueRingBuffer();
  int size() { return count; }
  T& queueRingBuffer::dequeue();
  T& queueRingBuffer::current();
  void queueRingBuffer::enqueue( const T &val );
};
 
template <class T>
queueRingBuffer<T>::queueRingBuffer( unsigned int max )
{
  count = 0;
  // constructor for queues based on ring buffers
  // create the first link
  T initialvalue;
  lastFree = new link<T>( initialvalue );
  lastFilled = lastFree;
  // make value point to itself
  lastFilled->nextLink = lastFilled;
  lastFilled->prevLink = lastFilled;
  // now add the remainder of the elements
  while ( max-- > 0 )
  {
    link<T> * newLink = new link<T>( initialvalue );
    newLink->prevLink = lastFilled;
    newLink->nextLink = lastFilled->nextLink;
    lastFilled->nextLink->prevLink = newLink;
    lastFilled->nextLink = newLink;
  }
}
 
template <class T>
queueRingBuffer<T>::~queueRingBuffer()
{
  // delete all memory associated with ring buffer
  link<T> * p = lastFree;
  link<T> * next;
 
  // walk around the circle deleting nodes
  while( p->nextLink != lastFree )
  {
    next = p->nextLink;
    delete p;
    p = next;
  }
}
 
template <class T>
T& queueRingBuffer<T>::dequeue()
{
  // remove element form front of queue
  // advance last free position
  lastFree = lastFree->nextLink;
  count--;
  // return value stored in last free position
  return lastFree->value;
}
 
template <class T>
T& queueRingBuffer<T>::current()
{
  // return value stored in current
  return lastFree->nextLink->value;
}
 
template <class T>
void queueRingBuffer<T>::enqueue( const T &val )
{
  // add new element to end of queue buffer
  // first check for potential overflow
  if( lastFilled->nextLink == lastFree )
  {
//    eDebug("[queueRingBuffer] increase size %d", count);
    link<T> * newLink = new link<T>( val );
    newLink->prevLink = lastFilled;
    newLink->nextLink = lastFilled->nextLink;
    lastFilled->nextLink->prevLink = newLink;
    lastFilled->nextLink = newLink;
  }
  else
  {
    // simply advance the last filled pointer
    lastFilled = lastFilled->nextLink;
    lastFilled->value = val;
  }
  count++;
}
#endif