Problem with circular buffer

Hello,

I haven't examined the whole program, but I see a problem with ElemType *data;

data is just a pointer and doesn't point to anything.  You need to create an ElemType, i.e. ElemType dataItem and then have data point to it, e.g.

ElemType dataItem;

ElemType * data;

data = &dataItem;

Stephen

Hello! Thanks for your answer.

In fact I've changed the declaration of data:

"ElemType data;"

However, I think that it is not working yet.

Are you setting all the Buffer parameters? i.e.

   ElemType dataArray[5];

   Buffer.size = 5;

   Buffer.elems = dataArray;

   Buffer.start = 0;

   Buffer.end = 0;

Also,  you shouldn't update your start pointer in the write function.  That should be done in the read function. 

Stephen

I have initialized the buffer before by setting this:

void

Init_Circular_Buffer(Circular_Buffer *cb, longsize)

{

cb->size=size;

cb->start = 0;

cb->end = 0;

cb->elems = (ElemType*)calloc(cb->size,sizeof(ElementType));

}

calling this function

void Init_Circular_Buffer(&Buffer);

You shouldn't put void before calling the function.  Also, the function call is missing the size parameter.

Otherwise, I don't see anything else wrong with it.  I suggest stepping through the program to see what's happening at each point.

Stephen

Yes, Sorry I call the function Init_Circular_Buffer(%buffer, size); (not any void. typing error)

I step through the program and I can see that the value of the register that i'm saving into the buffer is different from the one that i read from the buffer. And of course, they would be equal.

The following attached file seems to work:

typedef struct
{

   short value;

} ElemType;

typedef struct
{

   long size;

   long start;

   long end;

   ElemType *elems;

} Circular_Buffer;

Circular_Buffer buffer;

void Write_Circular_Buffer(Circular_Buffer *cb, ElemType *elem);

void main(void)
{
   ElemType data[10];
   ;
   ElemType dataArray[5];
   int i;

   Circular_Buffer Buffer;

   Buffer.size = 5;
   Buffer.elems = dataArray;
   Buffer.start = 0;
   Buffer.end = 0;

   for (i = 0; i < 10; i++)
   {
      data[i].value = i;
   }

   Write_Circular_Buffer(&Buffer, &data[0]);
   Write_Circular_Buffer(&Buffer, &data[1]);
   Write_Circular_Buffer(&Buffer, &data[2]);
   Write_Circular_Buffer(&Buffer, &data[3]);
   Write_Circular_Buffer(&Buffer, &data[4]);
   Write_Circular_Buffer(&Buffer, &data[5]);
   Write_Circular_Buffer(&Buffer, &data[6]);
   Write_Circular_Buffer(&Buffer, &data[7]);

}

void Write_Circular_Buffer(Circular_Buffer *cb, ElemType *elem)
{

   cb->elems[cb->end] = *elem;

   cb->end = (cb->end + 1) % cb->size;

   if (cb->end == cb->start)
   {

      cb->start = (cb->start + 1) % cb->size;

   }

}

I would recommend moving the following to a separate Read_Circular_Buffer() function.

if (cb->end == cb->start)   

{

      cb->start = (cb->start + 1) % cb->size;

}

Thank you! I will test it.

I have put the following into the write function for one reason:

if (cb->end == cb->start)   

{

      cb->start = (cb->start + 1) % cb->size;

}

I want to write every time in the buffer, and past a time print all the elements in the buffer. I am not doing write and read each time. I want to write and when the buffer finishes, follow in the beginning overwriting the existing values.

And at a certain time, I will print the elemens contained in the buffer in that moment.

Thank you