Use a std:.unique_ptr to make Trace a thin wrapper for TraceNode to make the happy path fast.

3 files changed, 52 insertions, 26 deletions

diff --git a/vespalib/src/tests/trace/trace.cpp b/vespalib/src/tests/trace/trace.cpp
index 9c8660fe395..46ebaf95114 100644
--- a/vespalib/src/tests/trace/trace.cpp
+++ b/vespalib/src/tests/trace/trace.cpp
@@ -146,25 +146,25 @@ TEST("testTraceLevel")
     t.setLevel(4);
     EXPECT_EQUAL(4u, t.getLevel());
     t.trace(9, "no");
-    EXPECT_EQUAL(0u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(0u, t.getNumChildren());
     t.trace(8, "no");
-    EXPECT_EQUAL(0u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(0u, t.getNumChildren());
     t.trace(7, "no");
-    EXPECT_EQUAL(0u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(0u, t.getNumChildren());
     t.trace(6, "no");
-    EXPECT_EQUAL(0u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(0u, t.getNumChildren());
     t.trace(5, "no");
-    EXPECT_EQUAL(0u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(0u, t.getNumChildren());
     t.trace(4, "yes");
-    EXPECT_EQUAL(1u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(1u, t.getNumChildren());
     t.trace(3, "yes");
-    EXPECT_EQUAL(2u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(2u, t.getNumChildren());
     t.trace(2, "yes");
-    EXPECT_EQUAL(3u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(3u, t.getNumChildren());
     t.trace(1, "yes");
-    EXPECT_EQUAL(4u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(4u, t.getNumChildren());
     t.trace(0, "yes");
-    EXPECT_EQUAL(5u, t.getRoot().getNumChildren());
+    EXPECT_EQUAL(5u, t.getNumChildren());
 }
 
 TEST("testCompact")
diff --git a/vespalib/src/vespa/vespalib/trace/trace.cpp b/vespalib/src/vespa/vespalib/trace/trace.cpp
index 2a9afc9b36b..ea93f574ed0 100644
--- a/vespalib/src/vespa/vespalib/trace/trace.cpp
+++ b/vespalib/src/vespa/vespalib/trace/trace.cpp
@@ -6,6 +6,15 @@
 
 namespace vespalib {
 
+Trace::Trace(const Trace &rhs)
+    : _root(),
+      _level(rhs._level)
+{
+    if (!rhs.isEmpty()) {
+        _root = std::make_unique<TraceNode>(rhs.getRoot());
+    }
+}
+
 bool
 Trace::trace(uint32_t level, const string &note, bool addTime)
 {
@@ -15,11 +24,30 @@ Trace::trace(uint32_t level, const string &note, bool addTime)
     if (addTime) {
         struct timeval tv;
         gettimeofday(&tv, nullptr);
-        _root.addChild(make_string("[%ld.%06ld] %s", tv.tv_sec, static_cast<long>(tv.tv_usec), note.c_str()));
+        ensureRoot().addChild(make_string("[%ld.%06ld] %s", tv.tv_sec, static_cast<long>(tv.tv_usec), note.c_str()));
     } else {
-        _root.addChild(note);
+        ensureRoot().addChild(note);
     }
     return true;
 }
 
+string
+Trace::toString() const {
+    return _root ? _root->toString(31337) : "";
+}
+
+void
+Trace::clear() {
+    _level = 0;
+    _root.reset();
+}
+
+TraceNode &
+Trace::ensureRoot() {
+    if (!_root) {
+        _root = std::make_unique<TraceNode>();
+    }
+    return *_root;
+}
+
 } // namespace vespalib
diff --git a/vespalib/src/vespa/vespalib/trace/trace.h b/vespalib/src/vespa/vespalib/trace/trace.h
index 5be9b662c89..1300f121404 100644
--- a/vespalib/src/vespa/vespalib/trace/trace.h
+++ b/vespalib/src/vespa/vespalib/trace/trace.h
@@ -27,7 +27,7 @@ public:
     explicit Trace(uint32_t level) : _root(), _level(level) { }
     Trace & operator = (Trace &&) = default;
     Trace(Trace &&) = default;
-    Trace(const Trace &) = default;
+    Trace(const Trace &);
     Trace & operator = (const Trace &) = delete;
     ~Trace() = default;
 
@@ -36,11 +36,7 @@ public:
      *
      * @return This, to allow chaining.
      */
-    Trace &clear() {
-        _level = 0;
-        _root.clear();
-        return *this;
-    }
+    void clear();
 
     /**
      * Swap the internals of this with another.
@@ -97,7 +93,9 @@ public:
     bool trace(uint32_t level, const string &note, bool addTime = true);
 
     void normalize() {
-        _root.normalize();
+        if (_root) {
+            _root->normalize();
+        }
     }
 
     /**
@@ -115,7 +113,7 @@ public:
     }
     void addChild(Trace && child) {
         if (!child.isEmpty()) {
-            addChild(std::move(child._root));
+            addChild(std::move(*child._root));
         }
     }
 
@@ -124,11 +122,11 @@ public:
      *
      * @return The root.
      */
-    const TraceNode &getRoot() const { return _root; }
+    const TraceNode &getRoot() const { return *_root; }
 
-    bool isEmpty() const { return _root.isEmpty(); }
+    bool isEmpty() const { return !_root || _root->isEmpty(); }
 
-    uint32_t getNumChildren() const { return _root.getNumChildren(); }
+    uint32_t getNumChildren() const { return _root ? _root->getNumChildren() : 0; }
     const TraceNode & getChild(uint32_t child) const { return getRoot().getChild(child); }
 
     /**
@@ -137,11 +135,11 @@ public:
      *
      * @return Readable trace string.
      */
-    string toString() const { return _root.toString(31337); }
+    string toString() const;
 private:
-    TraceNode &ensureRoot() { return _root; }
+    TraceNode &ensureRoot();
 
-    TraceNode _root;
+    std::unique_ptr<TraceNode> _root;
     uint32_t  _level;
 };