rte_kni_fifo.h

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static void
kni_fifo_init(struct rte_kni_fifo *fifo, unsigned size)
{
        /* Ensure size is power of 2 */
        if (size & (size - 1))
                rte_panic("KNI fifo size must be power of 2\n");

        fifo->write = 0;
        fifo->read = 0;
        fifo->len = size;
        fifo->elem_size = sizeof(void *);
}

static inline unsigned
kni_fifo_put(struct rte_kni_fifo *fifo, void **data, unsigned num)
{
        unsigned i = 0;
        unsigned fifo_write = fifo->write;
        unsigned fifo_read = fifo->read;
        unsigned new_write = fifo_write;

        for (i = 0; i < num; i++) {
                new_write = (new_write + 1) & (fifo->len - 1);

                if (new_write == fifo_read)
                        break;
                fifo->buffer[fifo_write] = data[i];
                fifo_write = new_write;
        }
        fifo->write = fifo_write;
        return i;
}

static inline unsigned
kni_fifo_get(struct rte_kni_fifo *fifo, void **data, unsigned num)
{
        unsigned i = 0;
        unsigned new_read = fifo->read;
        unsigned fifo_write = fifo->write;
        for (i = 0; i < num; i++) {
                if (new_read == fifo_write)
                        break;

                data[i] = fifo->buffer[new_read];
                new_read = (new_read + 1) & (fifo->len - 1);
        }
        fifo->read = new_read;
        return i;
}