JUCE_FIFO实现分析

JUCE_FIFO代码简单剖析，此处的剖析就是给自己留一个方便查询的内容；不做太多内容的要求，只做简单的记录；本文以初学者的角度来些，大牛请飘过O(∩_∩)O

FIFO的功能在博客的其他帖子里面已经有说明了，这里就简单通过图表说明下类里面的两个函数的实现机制，以及使用方法。下面写贴出代码和例子

 void AbstractFifo::prepareToWrite (int numToWrite, int& startIndex1,
  int& blockSize1, int& startIndex2, int& blockSize2) const noexcept
 {
  const int vs = validStart.get();
  const int ve = validEnd.value;
  const int freeSpace = ve >= vs ? (bufferSize - (ve - vs)) : (vs - ve);
  numToWrite = jmin (numToWrite, freeSpace - );
  if (numToWrite <= )
  {
  startIndex1 = ;
  startIndex2 = ;
  blockSize1 = ;
  blockSize2 = ;
  }
  else
  {
  startIndex1 = ve;
  startIndex2 = ;
  blockSize1 = jmin (bufferSize - ve, numToWrite);
  numToWrite -= blockSize1;
  blockSize2 = numToWrite <=  ?  : jmin (numToWrite, vs);
  }
 }

 void AbstractFifo::prepareToRead (int numWanted, int& startIndex1, int& blockSize1,
 int& startIndex2, int& blockSize2) const noexcept
 {
  const int vs = validStart.value;
  const int ve = validEnd.get();
  const int numReady = ve >= vs ? (ve - vs) : (bufferSize - (vs - ve));
  numWanted = jmin (numWanted, numReady);
  if (numWanted <= )
  {
  startIndex1 = ;
  startIndex2 = ;
  blockSize1 = ;
  blockSize2 = ;
  }
  else
  {
  startIndex1 = vs;
  startIndex2 = ;
  blockSize1 = jmin (bufferSize - vs, numWanted);
  numWanted -= blockSize1;
  blockSize2 = numWanted <=  ?  : jmin (numWanted, ve);
  }
 }

以上是程序具体实现，下面贴出代码例子;

 e.g.
  @code
  class MyFifo
  {
  public:
  MyFifo() : abstractFifo ()
  {
  }
  void addToFifo (const int* someData, int numItems)
  {
  int start1, size1, start2, size2;
  abstractFifo.prepareToWrite (numItems, start1, size1, start2, size2);
  if (size1 > )
  copySomeData (myBuffer + start1, someData, size1);
  if (size2 > )
  copySomeData (myBuffer + start2, someData + size1, size2);
  abstractFifo.finishedWrite (size1 + size2);
  }
  void readFromFifo (int* someData, int numItems)
  {
  int start1, size1, start2, size2;
  abstractFifo.prepareToRead (numSamples, start1, size1, start2, size2);
  if (size1 > )
  copySomeData (someData, myBuffer + start1, size1);
  if (size2 > )
  copySomeData (someData + size1, myBuffer + start2, size2);
  abstractFifo.finishedRead (size1 + size2);
  }
  private:
  AbstractFifo abstractFifo;
  int myBuffer [];
  };
  @endcode
 */

其实在这我不想说的太多，主要是刚开始看代码和我自己的想法不太一致，后来详细看了下其实也很简单，就是一个循环队列的实现；使用开始和技术指针确定写入、读取位置提供给外部使用，外部程序无需再自己处理写入、读取位置的判断。就一下两种可能性，一个是开始位置在前结束位置在后，一个是开始位置在后结束位置在前；