[Qemu-devel] Re: [RFC PATCH 07/20] Introduce qemu_put_vector() and qemu_put_vector_prepare() to use put_vector() in QEMUFile.

[Anthony Liguori <aliguori@linux.vnet.ibm.com>]

On 04/21/2010 12:57 AM, Yoshiaki Tamura wrote:
> For fool proof purpose, qemu_put_vector_parepare should be called
> before qemu_put_vector.  Then, if qemu_put_* functions except this is
> called after qemu_put_vector_prepare, program will abort().
>
> Signed-off-by: Yoshiaki Tamura<tamura.yoshiaki@lab.ntt.co.jp>
>    

I don't get it.  What's this protecting against?

Regards,

Anthony Liguori

> ---
>   hw/hw.h  |    2 ++
>   savevm.c |   53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 55 insertions(+), 0 deletions(-)
>
> diff --git a/hw/hw.h b/hw/hw.h
> index 921cf90..10e6dda 100644
> --- a/hw/hw.h
> +++ b/hw/hw.h
> @@ -77,6 +77,8 @@ void qemu_fflush(QEMUFile *f);
>   int qemu_fclose(QEMUFile *f);
>   void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size);
>   void qemu_put_byte(QEMUFile *f, int v);
> +void qemu_put_vector(QEMUFile *f, QEMUIOVector *qiov);
> +void qemu_put_vector_prepare(QEMUFile *f);
>   void *qemu_realloc_buffer(QEMUFile *f, int size);
>   void qemu_clear_buffer(QEMUFile *f);
>
> diff --git a/savevm.c b/savevm.c
> index 944e788..22d928c 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -180,6 +180,7 @@ struct QEMUFile {
>       uint8_t *buf;
>
>       int has_error;
> +    int prepares_vector;
>   };
>
>   typedef struct QEMUFileStdio
> @@ -557,6 +558,58 @@ void qemu_put_byte(QEMUFile *f, int v)
>           qemu_fflush(f);
>   }
>
> +void qemu_put_vector(QEMUFile *f, QEMUIOVector *v)
> +{
> +    struct iovec *iov;
> +    int cnt;
> +    size_t bufsize;
> +    uint8_t *buf;
> +
> +    if (qemu_file_get_rate_limit(f) != 0) {
> +        fprintf(stderr,
> +                "Attempted to write vector while bandwidth limit is not zero.\n");
> +        abort();
> +    }
> +
> +    /* checks prepares vector.
> +     * For fool proof purpose, qemu_put_vector_parepare should be called
> +     * before qemu_put_vector.  Then, if qemu_put_* functions except this
> +     * is called after qemu_put_vector_prepare, program will abort().
> +     */
> +    if (!f->prepares_vector) {
> +        fprintf(stderr,
> +            "You should prepare with qemu_put_vector_prepare.\n");
> +        abort();
> +    } else if (f->prepares_vector&&  f->buf_index != 0) {
> +        fprintf(stderr, "Wrote data after qemu_put_vector_prepare.\n");
> +        abort();
> +    }
> +    f->prepares_vector = 0;
> +
> +    if (f->put_vector) {
> +        qemu_iovec_to_vector(v,&iov,&cnt);
> +        f->put_vector(f->opaque, iov, 0, cnt);
> +    } else {
> +        qemu_iovec_to_size(v,&bufsize);
> +        buf = qemu_malloc(bufsize + 1 /* for '\0' */);
> +        qemu_iovec_to_buffer(v, buf);
> +        qemu_put_buffer(f, buf, bufsize);
> +        qemu_free(buf);
> +    }
> +
> +}
> +
> +void qemu_put_vector_prepare(QEMUFile *f)
> +{
> +    if (f->prepares_vector) {
> +        /* prepare vector */
> +        fprintf(stderr, "Attempted to prepare vector twice\n");
> +        abort();
> +    }
> +    f->prepares_vector = 1;
> +    qemu_fflush(f);
> +}
> +
>   int qemu_get_buffer(QEMUFile *f, uint8_t *buf, int size1)
>   {
>       int size, l;
>