stream: add pw_stream_get_nsec() to get current time

Make a method to get the current time to compare agains the pw_time-now
field. This is currently CLOCK_MONOTONIC but make this into a method
so that we can more easily change it later.

src/pipewire/filter.c

@@ -1993,6 +1993,14 @@ int pw_filter_get_time(struct pw_filter *filter, struct pw_time *time)
 	return 0;
 }
 
+SPA_EXPORT
+uint64_t pw_filter_get_nsec(struct pw_filter *filter)
+{
+	struct timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return SPA_TIMESPEC_TO_NSEC(&ts);
+}
+
 SPA_EXPORT
 struct pw_buffer *pw_filter_dequeue_buffer(void *port_data)
 {

src/pipewire/filter.h

@@ -215,6 +215,10 @@ pw_filter_update_params(struct pw_filter *filter,	/**< a \ref pw_filter */
 SPA_DEPRECATED
 int pw_filter_get_time(struct pw_filter *filter, struct pw_time *time);
 
+/** Get the current time in nanoseconds. This value can be compared with
+ * the nsec value in the spa_io_position. Since 1.1.0 */
+uint64_t pw_filter_get_nsec(struct pw_filter *filter);
+
 /** Get a buffer that can be filled for output ports or consumed
  * for input ports.  */
 struct pw_buffer *pw_filter_dequeue_buffer(void *port_data);

src/pipewire/stream.c

@@ -2409,6 +2409,14 @@ int pw_stream_get_time_n(struct pw_stream *stream, struct pw_time *time, size_t
 	return 0;
 }
 
+SPA_EXPORT
+uint64_t pw_stream_get_nsec(struct pw_stream *stream)
+{
+	struct timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return SPA_TIMESPEC_TO_NSEC(&ts);
+}
+
 static int
 do_trigger_deprecated(struct spa_loop *loop,
                  bool async, uint32_t seq, const void *data, size_t size, void *user_data)

src/pipewire/stream.h

@@ -245,9 +245,8 @@ struct pw_stream_control {
  * to the current time like this:
  *
  *\code{.c}
- *    struct timespec ts;
- *    clock_gettime(CLOCK_MONOTONIC, &ts);
- *    int64_t diff = SPA_TIMESPEC_TO_NSEC(&ts) - pw_time.now;
+ *    uint64_t now = pw_stream_get_nsec(stream);
+ *    int64_t diff = now - pw_time.now;
  *    int64_t elapsed = (pw_time.rate.denom * diff) / (pw_time.rate.num * SPA_NSEC_PER_SEC);
  *\endcode
  *
@@ -523,6 +522,10 @@ int pw_stream_set_control(struct pw_stream *stream, uint32_t id, uint32_t n_valu
 /** Query the time on the stream */
 int pw_stream_get_time_n(struct pw_stream *stream, struct pw_time *time, size_t size);
 
+/** Get the current time in nanoseconds. This value can be compared with
+ * the pw_time_now value. Since 1.1.0 */
+uint64_t pw_stream_get_nsec(struct pw_stream *stream);
+
 /** Query the time on the stream, deprecated since 0.3.50,
  * use pw_stream_get_time_n() to get the fields added since 0.3.50. */
 SPA_DEPRECATED