Re: [Qemu-devel] [v4 04/13] qemu-file: Add compression functions to QEMUFile

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Liang Li (liang.z.li@intel.com) wrote:
> qemu_put_compression_data() compress the data and put it to QEMUFile.
> qemu_put_qemu_file() put the data in the buffer of source QEMUFile to
> destination QEMUFile.
> 
> Signed-off-by: Liang Li <liang.z.li@intel.com>
> Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
> ---
>  include/migration/qemu-file.h |  3 +++
>  migration/qemu-file.c         | 39 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 42 insertions(+)
> 
> diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
> index d843c00..2204fb9 100644
> --- a/include/migration/qemu-file.h
> +++ b/include/migration/qemu-file.h
> @@ -159,6 +159,9 @@ void qemu_put_be32(QEMUFile *f, unsigned int v);
>  void qemu_put_be64(QEMUFile *f, uint64_t v);
>  int qemu_peek_buffer(QEMUFile *f, uint8_t *buf, int size, size_t offset);
>  int qemu_get_buffer(QEMUFile *f, uint8_t *buf, int size);
> +size_t qemu_put_compression_data(QEMUFile *f, const uint8_t *p, size_t size,
> +                                 int level);
> +int qemu_put_qemu_file(QEMUFile *f_des, QEMUFile *f_src);
>  /*
>   * Note that you can only peek continuous bytes from where the current pointer
>   * is; you aren't guaranteed to be able to peak to +n bytes unless you've
> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> index edc2830..de2da2d 100644
> --- a/migration/qemu-file.c
> +++ b/migration/qemu-file.c
> @@ -21,6 +21,7 @@
>   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
>   * THE SOFTWARE.
>   */
> +#include <zlib.h>
>  #include "qemu-common.h"
>  #include "qemu/iov.h"
>  #include "qemu/sockets.h"
> @@ -529,3 +530,41 @@ uint64_t qemu_get_be64(QEMUFile *f)
>      v |= qemu_get_be32(f);
>      return v;
>  }
> +
> +/* compress size bytes of data start at p with specific compression
> + * leve and store the compressed data to the buffer of f.

Typo: 'leve'

> + */
> +
> +size_t qemu_put_compression_data(QEMUFile *f, const uint8_t *p, size_t size,
> +                                 int level)
> +{
> +    size_t blen = IO_BUF_SIZE - f->buf_index - sizeof(int32_t);
> +
> +    if (blen < compressBound(size)) {
> +        return 0;
> +    }

Imagine that there were only 3 bytes space in the buffer; so that
   IO_BUF_SIZE - f->buf_index = 3
then you subtract sizeof(int32_t) and get -1, but size_t is unsigned
so the calculation works out as a very big number, and that comparison
fails and it carries on to call compress2.

> +    if (compress2(f->buf + f->buf_index + sizeof(int32_t), &blen, (Bytef *)p,
> +                  size, level) != Z_OK) {
> +        error_report("Compress Failed!");
> +        return 0;
> +    }
> +    qemu_put_be32(f, blen);
> +    f->buf_index += blen;
> +    return blen + sizeof(int32_t);
> +}
> +
> +/* Put the data in the buffer of f_src to the buffer of f_des, and
> + * then reset the buf_index of f_src to 0.
> + */
> +
> +int qemu_put_qemu_file(QEMUFile *f_des, QEMUFile *f_src)
> +{
> +    int len = 0;
> +
> +    if (f_src->buf_index > 0) {
> +        len = f_src->buf_index;
> +        qemu_put_buffer(f_des, f_src->buf, f_src->buf_index);
> +        f_src->buf_index = 0;
> +    }
> +    return len;
> +}
> -- 
> 1.9.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK