stream.c: allow stream PC's `events_discarded` field to be set by user

If a stream packet context `events_discarded` field is set a flush time,
check if its value keeps the count monotonic, and use this value to set
the stream's current discarded events count if so. If it's not set, do
like before and set it automatically from the stream's current count.

This will make it possible for a ctf.fs sink component to write the
original `events_discarded` field without having to read it, compute
the difference with the previous value, and use
bt_ctf_stream_append_discarded_events() to change the stream's discarded
events count.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/lib/ctf-ir/stream.c b/lib/ctf-ir/stream.c
index e14a014610d71bea1a1daa926e8492ac2482ecce..ce3936da98a8776380a62da025ddad367ba8b825 100644 (file)
--- a/lib/ctf-ir/stream.c
+++ b/lib/ctf-ir/stream.c
@@ -353,18 +353,50 @@ int set_packet_context_events_discarded(struct bt_ctf_stream *stream)
                goto end;
        }
 
-       ret = bt_ctf_field_unsigned_integer_set_value(field,
-               stream->discarded_events);
-       if (ret) {
-               BT_LOGW("Cannot set packet context field's `events_discarded` integer field's value: "
-                       "stream-addr=%p, stream-name=\"%s\", field-addr=%p, value=%" PRIu64,
-                       stream, bt_ctf_stream_get_name(stream),
-                       field, stream->discarded_events);
+       /*
+        * If the field is set by the user, make sure that the value is
+        * greater than or equal to the stream's current count of
+        * discarded events. We do not allow wrapping here. If it's
+        * valid, update the stream's current count.
+        */
+       if (bt_ctf_field_is_set(field)) {
+               uint64_t user_val;
+
+               ret = bt_ctf_field_unsigned_integer_get_value(field,
+                       &user_val);
+               if (ret) {
+                       BT_LOGW("Cannot get packet context `events_discarded` field's unsigned value: "
+                               "stream-addr=%p, stream-name=\"%s\", field-addr=%p",
+                               stream, bt_ctf_stream_get_name(stream), field);
+                       goto end;
+               }
+
+               if (user_val < stream->discarded_events) {
+                       BT_LOGW("Invalid packet context `events_discarded` field's unsigned value: "
+                               "value is lesser than the stream's current discarded events count: "
+                               "stream-addr=%p, stream-name=\"%s\", field-addr=%p, "
+                               "value=%" PRIu64 ", "
+                               "stream-discarded-events-count=%" PRIu64,
+                               stream, bt_ctf_stream_get_name(stream), field,
+                               user_val, stream->discarded_events);
+                       goto end;
+               }
+
+               stream->discarded_events = user_val;
        } else {
-               BT_LOGV("Set packet context field's `events_discarded` field's value: "
-                       "stream-addr=%p, stream-name=\"%s\", field-addr=%p, value=%" PRIu64,
-                       stream, bt_ctf_stream_get_name(stream),
-                       field, stream->discarded_events);
+               ret = bt_ctf_field_unsigned_integer_set_value(field,
+                       stream->discarded_events);
+               if (ret) {
+                       BT_LOGW("Cannot set packet context field's `events_discarded` integer field's value: "
+                               "stream-addr=%p, stream-name=\"%s\", field-addr=%p, value=%" PRIu64,
+                               stream, bt_ctf_stream_get_name(stream),
+                               field, stream->discarded_events);
+               } else {
+                       BT_LOGV("Set packet context field's `events_discarded` field's value: "
+                               "stream-addr=%p, stream-name=\"%s\", field-addr=%p, value=%" PRIu64,
+                               stream, bt_ctf_stream_get_name(stream),
+                               field, stream->discarded_events);
+               }
        }
 
 end:
@@ -1621,6 +1653,7 @@ end:
        reset_structure_field(stream->packet_context, "timestamp_end");
        reset_structure_field(stream->packet_context, "packet_size");
        reset_structure_field(stream->packet_context, "content_size");
+       reset_structure_field(stream->packet_context, "events_discarded");
 
        if (ret < 0) {
                /*