From a9c3f82c1196854e59a000d53645b29d8e6e239d Mon Sep 17 00:00:00 2001
From: David Capello <davidcapello@gmail.com>
Date: Tue, 15 Sep 2015 08:18:52 -0300
Subject: [PATCH] Use a binary search to find cels in LayerImage

---
 src/doc/layer.cpp | 68 +++++++++++++++++++++++++++++++++--------------
 src/doc/layer.h   |  5 ++++
 2 files changed, 53 insertions(+), 20 deletions(-)

diff --git a/src/doc/layer.cpp b/src/doc/layer.cpp
index 4d574bc31..c4865b535 100644
--- a/src/doc/layer.cpp
+++ b/src/doc/layer.cpp
@@ -125,16 +125,11 @@ void LayerImage::destroyAllCels()
 
 Cel* LayerImage::cel(frame_t frame) const
 {
-  CelConstIterator it = getCelBegin();
-  CelConstIterator end = getCelEnd();
-
-  for (; it != end; ++it) {
-    Cel* cel = *it;
-    if (cel->frame() == frame)
-      return cel;
-  }
-
-  return NULL;
+  CelConstIterator it = findCelIterator(frame);
+  if (it != getCelEnd())
+    return *it;
+  else
+    return nullptr;
 }
 
 void LayerImage::getCels(CelList& cels) const
@@ -154,6 +149,46 @@ Cel* LayerImage::getLastCel() const
     return NULL;
 }
 
+CelConstIterator LayerImage::findCelIterator(frame_t frame) const
+{
+  CelIterator it = const_cast<LayerImage*>(this)->findCelIterator(frame);
+  return CelConstIterator(it);
+}
+
+CelIterator LayerImage::findCelIterator(frame_t frame)
+{
+  auto first = getCelBegin();
+  auto end = getCelEnd();
+
+  // Here we use a binary search to find the first cel equal to "frame" (or after frame)
+  first = std::lower_bound(
+    first, end, nullptr,
+    [frame](Cel* cel, Cel*) -> bool {
+      return cel->frame() < frame;
+    });
+
+  // We return the iterator only if it's an exact match
+  if (first != end && (*first)->frame() == frame)
+    return first;
+  else
+    return end;
+}
+
+CelIterator LayerImage::findFirstCelIteratorAfter(frame_t firstAfterFrame)
+{
+  auto first = getCelBegin();
+  auto end = getCelEnd();
+
+  // Here we use a binary search to find the first cel after the given frame
+  first = std::lower_bound(
+    first, end, nullptr,
+    [firstAfterFrame](Cel* cel, Cel*) -> bool {
+      return cel->frame() <= firstAfterFrame;
+    });
+
+  return first;
+}
+
 void LayerImage::addCel(Cel* cel)
 {
   ASSERT(cel);
@@ -162,14 +197,7 @@ void LayerImage::addCel(Cel* cel)
   ASSERT(sprite());
   ASSERT(cel->image()->pixelFormat() == sprite()->pixelFormat());
 
-  CelIterator it = getCelBegin();
-  CelIterator end = getCelEnd();
-
-  for (; it != end; ++it) {
-    if ((*it)->frame() > cel->frame())
-      break;
-  }
-
+  CelIterator it = findFirstCelIteratorAfter(cel->frame());
   m_cels.insert(it, cel);
 
   cel->setParentLayer(this);
@@ -183,8 +211,8 @@ void LayerImage::addCel(Cel* cel)
  */
 void LayerImage::removeCel(Cel* cel)
 {
-  CelIterator it = std::find(m_cels.begin(), m_cels.end(), cel);
-
+  ASSERT(cel);
+  CelIterator it = findCelIterator(cel->frame());
   ASSERT(it != m_cels.end());
 
   m_cels.erase(it);
diff --git a/src/doc/layer.h b/src/doc/layer.h
index 84e70f2dc..e7882b8d9 100644
--- a/src/doc/layer.h
+++ b/src/doc/layer.h
@@ -125,10 +125,15 @@ namespace doc {
     void addCel(Cel *cel);
     void removeCel(Cel *cel);
     void moveCel(Cel *cel, frame_t frame);
+
     Cel* cel(frame_t frame) const override;
     void getCels(CelList& cels) const override;
     void displaceFrames(frame_t fromThis, frame_t delta) override;
+
     Cel* getLastCel() const;
+    CelConstIterator findCelIterator(frame_t frame) const;
+    CelIterator findCelIterator(frame_t frame);
+    CelIterator findFirstCelIteratorAfter(frame_t firstAfterFrame);
 
     void configureAsBackground();