From 8c0b0990a8327429de741b89ea5c4df4344163df Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Tue, 30 Dec 2014 00:06:15 +0100
Subject: [PATCH] Dramatically improve performance when sorting vectors of
 PointerTo objects

---
 panda/src/express/pointerTo.h     | 14 ++++++++++++++
 panda/src/express/pointerToVoid.I | 10 ++++++++++
 panda/src/express/pointerToVoid.h |  4 ++++
 3 files changed, 28 insertions(+)

diff --git a/panda/src/express/pointerTo.h b/panda/src/express/pointerTo.h
index b989b0f944..144bc0eb87 100644
--- a/panda/src/express/pointerTo.h
+++ b/panda/src/express/pointerTo.h
@@ -163,6 +163,20 @@ PUBLISHED:
 };
 
 
+// The existence of these functions makes it possible to sort vectors
+// of PointerTo objects without incurring the cost of unnecessary
+// reference count changes.  The performance difference is dramatic!
+template <class T>
+void swap(PointerTo<T> &one, PointerTo<T> &two) {
+  one.swap(two);
+}
+
+template <class T>
+void swap(ConstPointerTo<T> &one, ConstPointerTo<T> &two) {
+  one.swap(two);
+}
+
+
 // Finally, we'll define a couple of handy abbreviations to save on
 // all that wasted typing time.
 
diff --git a/panda/src/express/pointerToVoid.I b/panda/src/express/pointerToVoid.I
index 0834b25f60..108e959323 100644
--- a/panda/src/express/pointerToVoid.I
+++ b/panda/src/express/pointerToVoid.I
@@ -105,3 +105,13 @@ operator != (const PointerToVoid &other) const {
   return _void_ptr != other._void_ptr;
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: PointerToVoid::swap
+//       Access: Public
+//  Description: Swaps the contents of this PointerTo with the other,
+//               without touching the reference counts.
+////////////////////////////////////////////////////////////////////
+INLINE void PointerToVoid::
+swap(PointerToVoid &other) {
+  std::swap(_void_ptr, other._void_ptr);
+}
diff --git a/panda/src/express/pointerToVoid.h b/panda/src/express/pointerToVoid.h
index 7b1a9ff335..2556b1eb8c 100644
--- a/panda/src/express/pointerToVoid.h
+++ b/panda/src/express/pointerToVoid.h
@@ -20,6 +20,8 @@
 #include "memoryBase.h"
 #include "atomicAdjust.h"
 
+#include <algorithm>
+
 ////////////////////////////////////////////////////////////////////
 //       Class : PointerToVoid
 // Description : This is the non-template part of the base class for
@@ -52,6 +54,8 @@ public:
   INLINE bool operator == (const PointerToVoid &other) const;
   INLINE bool operator != (const PointerToVoid &other) const;
 
+  INLINE void swap(PointerToVoid &other);
+
 protected:
   // Within the PointerToVoid class, we only store a void pointer.
   // This is actually the (To *) pointer that is typecast to (void *)