Re: [Qemu-devel] [PATCH 2/2] io/buffer: avoid memmove at each qio_buffer_advance

[Gerd Hoffmann <kraxel@redhat.com>]

> diff --git a/include/io/buffer.h b/include/io/buffer.h
> index f63869e..43688cc 100644
> --- a/include/io/buffer.h
> +++ b/include/io/buffer.h
> @@ -39,6 +39,8 @@ struct QIOBuffer {
>      size_t offset;
>      uint64_t avg_size;
>      uint8_t *buffer;
> +    size_t base_offs;
> +    uint8_t *base_ptr;

Why a separate base_ptr?

While being at it I'd much prefer to replace offset with start & end.
The buffer content is buffer[start] ... buffer[end-1] then.

We can allow the buffer to wrap around, i.e. end < start.  Buffer
content is buf[start] ... buffer[size-1] and buffer[0] .. buffer[end-1]
then.  Makes the buffer management a bit more complicated, but we never
have to memmove then (except when changing buffer size) and the
WASTED_SIZE logic isn't needed too ...

cheers,
  Gerd