c - 简单循环缓冲区: Need to extend function to overwrite old data

Question

我正在尝试实现一个简单的循环缓冲区并覆盖旧数据(只是尝试缓冲区)。实际上我实现了一个缓冲区，但它并没有覆盖旧数据。当缓冲区已满时，它不会向数组添加新数据。

我有以下内容:

//Struct with 8 bytes
typedef struct
{
   int8 data_A;                        
   int16 data_B;
   int8 data_C;
   int32 data_D; 
} MyData_Struct_t

//The Circular buffer struct
typedef struct {
   MyData_Struct_t  myData[10]; // 10 elemtns of MyData_Struct_t
   int8 write_idx
   int8 read_idx
   int8 NrOfMessagesinTheQue
} RingBuffer


static MyData_Struct_t  myDataVariable =  {0}; // Instance of MyData_Struct_t
static RingBuffer myRingBuffer= { 0 };      // Instance of myRingBuffer

myDataVariable.data_A = getData(A);  // Lets' say getData() function is called cyclic and new data is received
myDataVariable.data_B = getData(B);  
myDataVariable.data_C = getData(C);   
myDataVariable.data_D = getData(D); 

// Here I call a function to fill the array with data
writeDataToRingbuffer(&myRingBuffer, &myDataVariable); 

void writeDataToRingbuffer(RingBuffer *pBuf, MyData_Struct_t *Data)
{
   if (10 <= pBuf->NrOfMessagesinTheQue)
   {
        // Buffer is Full
   }

   else if (pBuf->write_idx < 10)
   {
      (void)memcpy(&pBuf->myData[pBuf->write_idx], Data, 
sizeof(MyData_Struct_t));  //myData will be read later by another function

      if ((10 - 1u) == pBuf->write_idx)
      {
         pBuf->write_idx = 0u;
      }

      else
      {
         pBuf->write_idx += 1;
      }

      pBuf->NrOfMessagesinTheQue++;
   }

   else
   {
      // Out of boundary
   }
}

我需要一些想法如何扩展此功能以覆盖旧数据？

非常感谢!

Answer 1

如果您只想覆盖最旧的数据，只需使用索引对缓冲区大小取模即可:

#define BUFFER_SIZE 10  // size of myData

void writeDataToRingbuffer(RingBuffer *pBuf, MyData_Struct_t *Data)
{
    (void)memcpy(&pBuf->myData[pBuf->write_idx % BUFFER_SIZE], Data, 
         sizeof(MyData_Struct_t));  //myData will be read later by another function

    pBuf->write_idx += 1;
    pBuf->NrOfMessagesinTheQue++;
}

使用此方法，您还可以组合 write_idx 和 NrOfMessageinTheQue，因为您现在不必将索引重置为 0。