Re: [Qemu-devel] [PATCH 1/5] qemu-char: Add new char device CirMemCharDriver

[Luiz Capitulino <lcapitulino@redhat.com>]

On Wed, 12 Sep 2012 19:57:22 +0800
Lei Li <lilei@linux.vnet.ibm.com> wrote:

> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> ---
>  qemu-char.c |   84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 84 insertions(+), 0 deletions(-)
> 
> diff --git a/qemu-char.c b/qemu-char.c
> index 767da93..0470085 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -2591,6 +2591,90 @@ size_t qemu_chr_mem_osize(const CharDriverState *chr)
>      return d->outbuf_size;
>  }
>  
> +/*********************************************************/
> +/*CircularMemory chardev*/
> +
> +typedef struct {
> +    size_t cbuf_capacity;
> +    size_t cbuf_in;
> +    size_t cbuf_out;
> +    size_t cbuf_count;
> +    uint8_t *cbuf;
> +} CircMemCharDriver;
> +
> +static int cirmem_chr_is_empty(CharDriverState *chr)
> +{
> +    CircMemCharDriver *d = chr->opaque;
> +
> +    return d->cbuf_count == 0;
> +}
> +
> +static int cirmem_chr_is_full(CharDriverState *chr)
> +{
> +    CircMemCharDriver *d = chr->opaque;
> +
> +    return d->cbuf_count == d->cbuf_capacity;
> +}

Both argument's from the functions above can be const.

> +
> +static int cirmem_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
> +{
> +    CircMemCharDriver *d = chr->opaque;
> +    int left;
> +
> +    if (d->cbuf_capacity < len) {
> +        return -1;
> +    }
> +
> +    left = d->cbuf_capacity - d->cbuf_count % d->cbuf_capacity;
> +
> +    /* Some of cbuf need to be overwrited */
> +    if (left < len) {
> +        memcpy(d->cbuf + d->cbuf_in, buf, left);
> +        memcpy(d->cbuf + d->cbuf_out, buf + left, len - left);
> +        d->cbuf_out = (d->cbuf_out + len - left) % d->cbuf_capacity;
> +        d->cbuf_count = d->cbuf_count + left;
> +    } else {
> +        /* Completely overwrite */
> +        if (cirmem_chr_is_full(chr)) {
> +            d->cbuf_out = (d->cbuf_out + len) % d->cbuf_capacity;
> +        } else {
> +        /* Enough cbuf to write */
> +        d->cbuf_count += len;
> +        }
> +        memcpy(d->cbuf + d->cbuf_in, buf, len);
> +    }
> +
> +    d->cbuf_in = (d->cbuf_in + len) % d->cbuf_capacity;
> +
> +    return len;
> +}

I remember I made a few comments about using pointers instead
of indexes, did you consider doing that?

Btw, does this patch even build by its own? You're adding static
functions but no users.

> +
> +static void cirmem_chr_read(CharDriverState *chr, uint8_t *buf, int len)
> +{
> +    CircMemCharDriver *d = chr->opaque;
> +    int left;
> +
> +    if (cirmem_chr_is_empty(chr)) {
> +        return;
> +    }
> +
> +    left = d->cbuf_capacity - d->cbuf_count % d->cbuf_capacity;
> +
> +    if (d->cbuf_capacity < len) {
> +        len = d->cbuf_capacity;
> +    }
> +
> +    if (left < len) {
> +        memcpy(buf, d->cbuf + d->cbuf_out, left);
> +        memcpy(buf + left, d->cbuf + d->cbuf_out + left, len - left);
> +    } else {
> +        memcpy(buf, d->cbuf + d->cbuf_out, len);
> +    }
> +
> +    d->cbuf_out = (d->cbuf_out + len) % d->cbuf_capacity;
> +    d->cbuf_count -= len;
> +}
> +
>  QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
>  {
>      char host[65], port[33], width[8], height[8];