[Spice-devel] [PATCH spice-gtk] spice-session: Simplify spice_session_get_mm_time formula

[Uri Lublin]

On 08/21/2018 10:06 AM, Frediano Ziglio wrote:
> Instead of keeping 2 fields for the conversion monotonic time ->
> multimedia time compute a single offset.

I'm not sure it's easier to understand it that way, but it does
use 1 fields instead of 2 and the math looks good to me.

Acked-by: Uri Lublin <uril at redhat.com>

> 
> Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> ---
>   src/spice-session.c | 12 +++++-------
>   1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/src/spice-session.c b/src/spice-session.c
> index b1aeb84..fd1856d 100644
> --- a/src/spice-session.c
> +++ b/src/spice-session.c
> @@ -95,9 +95,8 @@ struct _SpiceSessionPrivate {
>       SpiceChannel      *cmain; /* weak reference */
>       Ring              channels;
>       guint             channels_destroying;
> -    guint32           mm_time;
>       gboolean          client_provided_sockets;
> -    guint64           mm_time_at_clock;
> +    guint64           mm_time_offset;
>       SpiceSession      *migration;
>       GList             *migration_left;
>       SpiceSessionMigration migration_state;
> @@ -2357,7 +2356,7 @@ guint32 spice_session_get_mm_time(SpiceSession *session)
>   
>       /* FIXME: we may want to estimate the drift of clocks, and well,
>          do something better than this trivial approach */
> -    return s->mm_time + (g_get_monotonic_time() - s->mm_time_at_clock) / 1000;
> +    return (g_get_monotonic_time() - s->mm_time_offset) / 1000;
>   }
>   
>   #define MM_TIME_DIFF_RESET_THRESH 500 // 0.5 sec
> @@ -2372,12 +2371,11 @@ void spice_session_set_mm_time(SpiceSession *session, guint32 time)
>   
>       old_time = spice_session_get_mm_time(session);
>   
> -    s->mm_time = time;
> -    s->mm_time_at_clock = g_get_monotonic_time();
> -    SPICE_DEBUG("set mm time: %u", spice_session_get_mm_time(session));
> +    s->mm_time_offset = g_get_monotonic_time() - time * (guint64) 1000;
> +    SPICE_DEBUG("set mm time: %u", time);
>       if (spice_mmtime_diff(time, old_time + MM_TIME_DIFF_RESET_THRESH) > 0 ||
>           spice_mmtime_diff(time, old_time) < 0) {
> -        SPICE_DEBUG("%s: mm-time-reset, old %u, new %u", __FUNCTION__, old_time, s->mm_time);
> +        SPICE_DEBUG("%s: mm-time-reset, old %u, new %u", __FUNCTION__, old_time, time);
>           g_coroutine_signal_emit(session, signals[SPICE_SESSION_MM_TIME_RESET], 0);
>       }
>   }
>