Fixing RingBufferN

Author: aentinger

api/RingBuffer.h

@@ -39,6 +39,7 @@ class RingBufferN
     uint8_t _aucBuffer[N] ;
     volatile int _iHead ;
     volatile int _iTail ;
+    volatile int _numElems;
 
   public:
     RingBufferN( void ) ;
@@ -67,16 +68,15 @@ RingBufferN<N>::RingBufferN( void )
 template <int N>
 void RingBufferN<N>::store_char( uint8_t c )
 {
-  int i = nextIndex(_iHead);
-
   // if we should be storing the received character into the location
   // just before the tail (meaning that the head would advance to the
   // current location of the tail), we're about to overflow the buffer
   // and so we don't write the character or advance the head.
-  if ( i != _iTail )
+  if (!isFull())
   {
     _aucBuffer[_iHead] = c ;
-    _iHead = i ;
+    _iHead = nextIndex(_iHead);
+    _numElems++;
   }
 }
 
@@ -85,6 +85,7 @@ void RingBufferN<N>::clear()
 {
   _iHead = 0;
   _iTail = 0;
+  _numElems = 0;
 }
 
 template <int N>
@@ -95,28 +96,21 @@ int RingBufferN<N>::read_char()
 
   uint8_t value = _aucBuffer[_iTail];
   _iTail = nextIndex(_iTail);
+  _numElems--;
 
   return value;
 }
 
 template <int N>
 int RingBufferN<N>::available()
 {
-  int delta = _iHead - _iTail;
-
-  if(delta < 0)
-    return N + delta;
-  else
-    return delta;
+  return _numElems;
 }
 
 template <int N>
 int RingBufferN<N>::availableForStore()
 {
-  if (_iHead >= _iTail)
-    return N - 1 - _iHead + _iTail;
-  else
-    return _iTail - _iHead - 1;
+  return (N - _numElems);
 }
 
 template <int N>
@@ -137,7 +131,7 @@ int RingBufferN<N>::nextIndex(int index)
 template <int N>
 bool RingBufferN<N>::isFull()
 {
-  return (nextIndex(_iHead) == _iTail);
+  return (_numElems == N);
 }
 
 }