Add cache of patterns matching discovered topics

rosbag_snapshot/include/rosbag_snapshot/snapshotter.h

@@ -53,6 +53,7 @@
 #include <utility>
 #include <vector>
 #include <memory>
+#include <unordered_map>
 
 namespace rosbag_snapshot
 {
@@ -136,6 +137,8 @@ struct ROSBAG_DECL SnapshotterOptions
   typedef std::vector<SnapshotterTopicPatternConstPtr> patterns_t;
   // List of regexs that match topics which should be tracked by the recorder.
   patterns_t patterns_;
+  // Cache of the first pattern that has matched a given topic (or nullptr if no pattern matched).
+  std::unordered_map<std::string, SnapshotterTopicPatternConstPtr> matching_patterns_cache_;
 
   SnapshotterOptions(ros::Duration default_duration_limit = ros::Duration(30), int32_t default_memory_limit = -1,
                      int32_t default_count_limit = -1, ros::Duration status_period = ros::Duration(1),

rosbag_snapshot/src/snapshotter.cpp

@@ -82,6 +82,7 @@ SnapshotterOptions::SnapshotterOptions(ros::Duration default_duration_limit, int
   , clear_buffer_(clear_buffer)
   , topics_()
   , patterns_()
+  , matching_patterns_cache_()
 {
 }
 
@@ -120,10 +121,18 @@ bool SnapshotterOptions::addTopicOrPattern(std::string const& topic_or_pattern,
 
 SnapshotterTopicPatternConstPtr SnapshotterOptions::findFirstMatchingPattern(const std::string &topic)
 {
-  for (const auto& pattern : patterns_)
+  auto it = matching_patterns_cache_.find(topic);
+  if (it != matching_patterns_cache_.end())
+    return it->second;
+  SnapshotterTopicPatternConstPtr matching_pattern = nullptr;
+  for (auto& pattern : patterns_)
     if (pattern->matches(topic))
-      return pattern;
-  return nullptr;
+    {
+      matching_pattern = pattern;
+      break;
+    }
+  matching_patterns_cache_[topic] = matching_pattern;
+  return matching_pattern;
 }
 
 SnapshotterTopicPattern::SnapshotterTopicPattern(const std::string &pattern,