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;
}

static inline uint32_t
kni_fifo_count(struct rte_kni_fifo *fifo)
{
    return (fifo->len + fifo->write - fifo->read) & (fifo->len - 1);
}