How to count no of elements in an Atomic_FIFO ?

[Salman Azmat]

Hi, I'm using Atomic_FIFO library and for my application I need to know the number of elements currently in the fifo, the library itself doesn't provide any functionality that tells the fifo size so I made some changes to it. I added following two lines in the header file.

static nrf_atomic_u32_t fifo_size;
uint32_t get_fifo_size();

And added some lines in the c file, shown below.

bool nrf_atfifo_item_put(nrf_atfifo_t * const p_fifo, nrf_atfifo_item_put_t * p_context)
{
    if ((p_context->last_tail.pos.wr) == (p_context->last_tail.pos.rd))
    {
        nrf_atfifo_wspace_close(p_fifo);
	    nrf_atomic_u32_add(&fifo_size, 1);  //my addition
        return true;
    }
    return false;
}

bool nrf_atfifo_item_free(nrf_atfifo_t * const p_fifo, nrf_atfifo_item_get_t * p_context)
{
    if ((p_context->last_head.pos.wr) == (p_context->last_head.pos.rd))
    {
        nrf_atfifo_rspace_close(p_fifo);
        nrf_atomic_u32_sub(&fifo_size, 1);  // my addition
        return true;
    }
    return false;
}


// my addition
uint32_t get_fifo_size()
{	return fifo_size;
}

So i declared a variable and increment and decrement it on successful push/pop operations. It works fine(well, at least it seems to work fine). But now I need another fifo, and as you might have noticed, my implementation of getSize(), will count all the push/pop operations across all the fifos created. So my question is how to add getSize() function that gives the current size of the respective fifos ?

Also, how to peek at an element at the front of fifo without actually removing it ?

[Jørgen Holmefjord]

Hi,

You should be able to get the available size from the FIFO object, nrf_atfifo_t. This object contain buffer size, item size, head and tail position for read and write.

If you are not able to utilize this, you will have to create an array that can hold the size for each available FIFO, and update the size value for the corresponding FIFO object.

Best regards,
Jørgen

[Salman Azmat]

Hi,

The buffer size tells the total buffer size allocated for fifo, so I think I'll have to keep an array for fifo_size.