[Spice-devel] [PATCH 2/5] improve lz4 protocol

[Uri Lublin]

On 05/16/2016 06:59 PM, Frediano Ziglio wrote:
> Reduce size if not compressed and compute compressed size using message
> length
>
> This should be merged in previous patch
> ---
>  common/messages.h |  2 +-
>  spice.proto       | 17 +++++++++++++----
>  2 files changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/common/messages.h b/common/messages.h
> index d001850..516a345 100644
> --- a/common/messages.h
> +++ b/common/messages.h
> @@ -59,7 +59,7 @@ typedef struct SpiceMsgCompressedData {
>      uint8_t type;
>      uint32_t uncompressed_size;
>      uint32_t compressed_size;
> -    uint8_t compressed_data[0];
> +    uint8_t *compressed_data;
>  } SpiceMsgCompressedData;
>
>  typedef struct SpiceMsgEmpty {
> diff --git a/spice.proto b/spice.proto
> index a515aef..0bfc515 100644
> --- a/spice.proto
> +++ b/spice.proto
> @@ -121,16 +121,25 @@ message Data {
>  } @nocopy;
>
>  enum8 data_compression_type {
> -    INVALID,
>      NONE,
>      LZ4,
>  };
>
> +struct EmptyStructure {
> +};
> +
>  message CompressedData {
>      data_compression_type type;
> -    uint32 uncompressed_size;
> -    uint32 compressed_size;
> -    uint8 compressed_data[] @end;
> +    switch (type) {
> +    /* we cannot use !NONE (works only with flags) */
> +    case NONE:
> +        /* due to the way cases are defined after NONE we must have something */
> +        /* due to a bug we cannot use @virtual to write 0 to compressed_size */
> +        EmptyStructure empty;
> +    default:
> +        uint32 uncompressed_size;

Hi Frediano,

Is it better if we replace the order, meaning
do not case NONE but case  LZ4

         case LZ4:
             uint32 uncompressed_size;


> +    } u @anon;
> +    uint8 compressed_data[] @as_ptr(compressed_size);


I find it confusing that compressed_size is not a part
of this definition but is used here.
(defined in common/messages.h above)

Thanks,
     Uri.