2 files changed, 29 insertions, 3 deletions

diff --git a/trace/control.c b/trace/control.c
index ed38e81..2c904b7 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -104,6 +104,7 @@ void trace_event_iter_init_all(TraceEventIter *iter)
 {
     iter->event = 0;
     iter->group = 0;
+    iter->group_id = -1;
     iter->pattern = NULL;
 }
 
@@ -113,20 +114,32 @@ void trace_event_iter_init_pattern(TraceEventIter *iter, const char *pattern)
     iter->pattern = pattern;
 }
 
+void trace_event_iter_init_group(TraceEventIter *iter, size_t group_id)
+{
+    trace_event_iter_init_all(iter);
+    iter->group_id = group_id;
+}
+
 TraceEvent *trace_event_iter_next(TraceEventIter *iter)
 {
     while (iter->group < nevent_groups &&
            event_groups[iter->group].events[iter->event] != NULL) {
         TraceEvent *ev = event_groups[iter->group].events[iter->event];
+        size_t group = iter->group;
         iter->event++;
         if (event_groups[iter->group].events[iter->event] == NULL) {
             iter->event = 0;
             iter->group++;
         }
-        if (!iter->pattern ||
-            g_pattern_match_simple(iter->pattern, trace_event_get_name(ev))) {
-            return ev;
+        if (iter->pattern &&
+            !g_pattern_match_simple(iter->pattern, trace_event_get_name(ev))) {
+            continue;
+        }
+        if (iter->group_id != -1 &&
+            iter->group_id != group) {
+            continue;
         }
+        return ev;
     }
 
     return NULL;
diff --git a/trace/control.h b/trace/control.h
index ce40bd0..23b8393 100644
--- a/trace/control.h
+++ b/trace/control.h
@@ -13,8 +13,11 @@
 #include "event-internal.h"
 
 typedef struct TraceEventIter {
+    /* iter state */
     size_t event;
     size_t group;
+    /* filter conditions */
+    size_t group_id;
     const char *pattern;
 } TraceEventIter;
 
@@ -40,6 +43,16 @@ void trace_event_iter_init_all(TraceEventIter *iter);
 void trace_event_iter_init_pattern(TraceEventIter *iter, const char *pattern);
 
 /**
+ * trace_event_iter_init_group:
+ * @iter: the event iterator struct
+ * @group_id: group_id to filter events by group.
+ *
+ * Initialize the event iterator struct @iter,
+ * using @group_id to filter for events in the group.
+ */
+void trace_event_iter_init_group(TraceEventIter *iter, size_t group_id);
+
+/**
  * trace_event_iter_next:
  * @iter: the event iterator struct
  *