Re: [Qemu-devel] [PATCH v3 05/46] ivshmem: factor out the incoming fifo handling

[Claudio Fontana]

On 15.09.2015 18:07, address@hidden wrote:
> From: Marc-André Lureau <address@hidden>
> 
> Make a new function fifo_update_and_get() that can be reused by other
> functions (in next commits).
> 
> Signed-off-by: Marc-André Lureau <address@hidden>
> ---
>  hw/misc/ivshmem.c | 59 
> ++++++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 39 insertions(+), 20 deletions(-)
> 
> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> index 2162d02..dd15f0e 100644
> --- a/hw/misc/ivshmem.c
> +++ b/hw/misc/ivshmem.c
> @@ -441,6 +441,42 @@ static int increase_dynamic_storage(IVShmemState *s, int 
> new_min_size)
>      return 0;
>  }
>  
> +static bool fifo_update_and_get(IVShmemState *s, const uint8_t *buf, int 
> size,
> +                                void *data, size_t len)
> +{
> +    const uint8_t *p;
> +    uint32_t num;
> +
> +    assert(len <= sizeof(long)); /* limitation of the fifo */
> +    if (fifo8_is_empty(&s->incoming_fifo) && size == len) {
> +        memcpy(data, buf, size);
> +        return true;
> +    }
> +
> +    IVSHMEM_DPRINTF("short read of %d bytes\n", size);
> +
> +    num = MIN(size, sizeof(long) - fifo8_num_used(&s->incoming_fifo));
> +    fifo8_push_all(&s->incoming_fifo, buf, num);
> +
> +    if (fifo8_num_used(&s->incoming_fifo) < len) {
> +        assert(num == 0);
> +        return false;
> +    }
> +
> +    size -= num;
> +    buf += num;
> +    p = fifo8_pop_buf(&s->incoming_fifo, len, &num);
> +    assert(num == len);
> +
> +    memcpy(data, p, len);
> +
> +    if (size > 0) {
> +        fifo8_push_all(&s->incoming_fifo, buf, size);
> +    }
> +
> +    return true;
> +}
> +
>  static void ivshmem_read(void *opaque, const uint8_t *buf, int size)
>  {
>      IVShmemState *s = opaque;
> @@ -448,26 +484,9 @@ static void ivshmem_read(void *opaque, const uint8_t 
> *buf, int size)
>      int guest_max_eventfd;
>      long incoming_posn;
>  
> -    if (fifo8_is_empty(&s->incoming_fifo) && size == sizeof(incoming_posn)) {
> -        memcpy(&incoming_posn, buf, size);
> -    } else {
> -        const uint8_t *p;
> -        uint32_t num;
> -
> -        IVSHMEM_DPRINTF("short read of %d bytes\n", size);
> -        num = MIN(size, sizeof(long) - fifo8_num_used(&s->incoming_fifo));
> -        fifo8_push_all(&s->incoming_fifo, buf, num);
> -        if (fifo8_num_used(&s->incoming_fifo) < sizeof(incoming_posn)) {
> -            return;
> -        }
> -        size -= num;
> -        buf += num;
> -        p = fifo8_pop_buf(&s->incoming_fifo, sizeof(incoming_posn), &num);
> -        g_assert(num == sizeof(incoming_posn));
> -        memcpy(&incoming_posn, p, sizeof(incoming_posn));
> -        if (size > 0) {
> -            fifo8_push_all(&s->incoming_fifo, buf, size);
> -        }
> +    if (!fifo_update_and_get(s, buf, size,
> +                             &incoming_posn, sizeof(incoming_posn))) {
> +        return;
>      }
>  
>      if (incoming_posn < -1) {
> 


Fine in principle, I have that reservation about using sizeof(long) as part of 
the interface.

Ciao

C.