/Users/craigcornelius/Projects/SPRING Mac Release 0.2/blockQueue.h

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#ifndef BLOCKQUEUE_H
#define BLOCKQUEUE_H
#include <string.h>

class blockQueue
{
public:
  blockQueue(int blockSize = 16*16*3, int queueSize = 512);
  ~blockQueue();

  int Enqueue(void *block);
  void *GetTailBlock();
  int Dequeue();
  bool isEmpty();
  inline bool isFull();

private:
  int updateCurrentSize();

  unsigned char* data;
  int currentSize;
  int blockSize;
  int queueSize;
  long int tail;
  long int head;
};



inline int blockQueue::Enqueue(void *block)
{
  // No DeQueue / EnQueue concurency pb since only Enqueue modifies head
  // and only Dequeue modifies tail
  // Moreover, we will not write on tail (that is write on a block possibly been
  // read by the GetNextBlock) since the ++tail happens only after Dequeue... and
  // we test if queue full
  if (!isFull())
  {
    memcpy(data + (head%queueSize)*blockSize, block, blockSize);
    ++head;
    return updateCurrentSize();
  }
  else
    return -1;
}

inline void *blockQueue::GetTailBlock()
{
  return (void *)(data + (tail%queueSize)*blockSize);
}

inline int blockQueue::Dequeue()
{
  // Must happen AFTER reading/processing the data (thru GetNextBlock), thus preventing basic concurency
  // pb where, in case of a full queue, enqueue tries to write on the block currently processed, because
  // the ++tail has been executed too early (before processing the data)
  if (!isEmpty())
  {
    ++tail;
    return updateCurrentSize();
  }
  else
    return -1;
}

inline bool blockQueue::isEmpty()
{
  return (currentSize <= 0);
}

inline bool blockQueue::isFull()
{
  return (currentSize >= queueSize);
}

inline int blockQueue::updateCurrentSize()
{
   return (currentSize = head - tail);
}

#endif // blockQueue.h

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