From 7591d45008471d89bb2e4452221a86b2c09de518 Mon Sep 17 00:00:00 2001
From: elsid <elsid.mail@gmail.com>
Date: Thu, 8 Oct 2020 00:58:11 +0200
Subject: [PATCH] Use memcpy to create navmesh key

Implementation with memcpy is ~13 times faster.
---
 .../detournavigator/navmeshtilescache.cpp     | 64 ++++++++-----------
 .../detournavigator/navmeshtilescache.hpp     | 31 ++++++---
 2 files changed, 50 insertions(+), 45 deletions(-)

diff --git a/components/detournavigator/navmeshtilescache.cpp b/components/detournavigator/navmeshtilescache.cpp
index 466d2e708..f554cd414 100644
--- a/components/detournavigator/navmeshtilescache.cpp
+++ b/components/detournavigator/navmeshtilescache.cpp
@@ -9,42 +9,32 @@ namespace DetourNavigator
 {
     namespace
     {
-        inline std::string makeNavMeshKey(const RecastMesh& recastMesh,
+        inline std::vector<unsigned char> makeNavMeshKey(const RecastMesh& recastMesh,
             const std::vector<OffMeshConnection>& offMeshConnections)
         {
-            std::string result;
-            result.reserve(
-                recastMesh.getIndices().size() * sizeof(int)
-                + recastMesh.getVertices().size() * sizeof(float)
-                + recastMesh.getAreaTypes().size() * sizeof(AreaType)
-                + recastMesh.getWater().size() * sizeof(RecastMesh::Water)
-                + offMeshConnections.size() * sizeof(OffMeshConnection)
-            );
-            std::copy(
-                reinterpret_cast<const char*>(recastMesh.getIndices().data()),
-                reinterpret_cast<const char*>(recastMesh.getIndices().data() + recastMesh.getIndices().size()),
-                std::back_inserter(result)
-            );
-            std::copy(
-                reinterpret_cast<const char*>(recastMesh.getVertices().data()),
-                reinterpret_cast<const char*>(recastMesh.getVertices().data() + recastMesh.getVertices().size()),
-                std::back_inserter(result)
-            );
-            std::copy(
-                reinterpret_cast<const char*>(recastMesh.getAreaTypes().data()),
-                reinterpret_cast<const char*>(recastMesh.getAreaTypes().data() + recastMesh.getAreaTypes().size()),
-                std::back_inserter(result)
-            );
-            std::copy(
-                reinterpret_cast<const char*>(recastMesh.getWater().data()),
-                reinterpret_cast<const char*>(recastMesh.getWater().data() + recastMesh.getWater().size()),
-                std::back_inserter(result)
-            );
-            std::copy(
-                reinterpret_cast<const char*>(offMeshConnections.data()),
-                reinterpret_cast<const char*>(offMeshConnections.data() + offMeshConnections.size()),
-                std::back_inserter(result)
-            );
+            const std::size_t indicesSize = recastMesh.getIndices().size() * sizeof(int);
+            const std::size_t verticesSize = recastMesh.getVertices().size() * sizeof(float);
+            const std::size_t areaTypesSize = recastMesh.getAreaTypes().size() * sizeof(AreaType);
+            const std::size_t waterSize = recastMesh.getWater().size() * sizeof(RecastMesh::Water);
+            const std::size_t offMeshConnectionsSize = offMeshConnections.size() * sizeof(OffMeshConnection);
+
+            std::vector<unsigned char> result(indicesSize + verticesSize + areaTypesSize + waterSize + offMeshConnectionsSize);
+            unsigned char* dst = result.data();
+
+            std::memcpy(dst, recastMesh.getIndices().data(), indicesSize);
+            dst += indicesSize;
+
+            std::memcpy(dst, recastMesh.getVertices().data(), verticesSize);
+            dst += verticesSize;
+
+            std::memcpy(dst, recastMesh.getAreaTypes().data(), areaTypesSize);
+            dst += areaTypesSize;
+
+            std::memcpy(dst, recastMesh.getWater().data(), waterSize);
+            dst += waterSize;
+
+            std::memcpy(dst, offMeshConnections.data(), offMeshConnectionsSize);
+
             return result;
         }
     }
@@ -189,8 +179,8 @@ namespace DetourNavigator
     {
         struct CompareBytes
         {
-            const char* mRhsIt;
-            const char* mRhsEnd;
+            const unsigned char* mRhsIt;
+            const unsigned char* const mRhsEnd;
 
             template <class T>
             int operator ()(const std::vector<T>& lhs)
@@ -225,7 +215,7 @@ namespace DetourNavigator
         };
     }
 
-    int NavMeshTilesCache::RecastMeshKeyView::compare(const std::string& other) const
+    int NavMeshTilesCache::RecastMeshKeyView::compare(const std::vector<unsigned char>& other) const
     {
         CompareBytes compareBytes {other.data(), other.data() + other.size()};
 
diff --git a/components/detournavigator/navmeshtilescache.hpp b/components/detournavigator/navmeshtilescache.hpp
index 57f57a56f..064d9e185 100644
--- a/components/detournavigator/navmeshtilescache.hpp
+++ b/components/detournavigator/navmeshtilescache.hpp
@@ -11,6 +11,8 @@
 #include <list>
 #include <mutex>
 #include <cassert>
+#include <cstring>
+#include <vector>
 
 namespace osg
 {
@@ -33,10 +35,10 @@ namespace DetourNavigator
             std::atomic<std::int64_t> mUseCount;
             osg::Vec3f mAgentHalfExtents;
             TilePosition mChangedTile;
-            std::string mNavMeshKey;
+            std::vector<unsigned char> mNavMeshKey;
             NavMeshData mNavMeshData;
 
-            Item(const osg::Vec3f& agentHalfExtents, const TilePosition& changedTile, std::string navMeshKey)
+            Item(const osg::Vec3f& agentHalfExtents, const TilePosition& changedTile, std::vector<unsigned char>&& navMeshKey)
                 : mUseCount(0)
                 , mAgentHalfExtents(agentHalfExtents)
                 , mChangedTile(changedTile)
@@ -120,19 +122,32 @@ namespace DetourNavigator
 
             virtual ~KeyView() = default;
 
-            KeyView(const std::string& value)
+            KeyView(const std::vector<unsigned char>& value)
                 : mValue(&value) {}
 
-            const std::string& getValue() const
+            const std::vector<unsigned char>& getValue() const
             {
                 assert(mValue);
                 return *mValue;
             }
 
-            virtual int compare(const std::string& other) const
+            virtual int compare(const std::vector<unsigned char>& other) const
             {
                 assert(mValue);
-                return mValue->compare(other);
+
+                const auto valueSize = mValue->size();
+                const auto otherSize = other.size();
+
+                if (const auto result = std::memcmp(mValue->data(), other.data(), std::min(valueSize, otherSize)))
+                    return result;
+
+                if (valueSize < otherSize)
+                    return -1;
+
+                if (valueSize > otherSize)
+                    return 1;
+
+                return 0;
             }
 
             virtual bool isLess(const KeyView& other) const
@@ -147,7 +162,7 @@ namespace DetourNavigator
             }
 
         private:
-            const std::string* mValue = nullptr;
+            const std::vector<unsigned char>* mValue = nullptr;
         };
 
         class RecastMeshKeyView : public KeyView
@@ -156,7 +171,7 @@ namespace DetourNavigator
             RecastMeshKeyView(const RecastMesh& recastMesh, const std::vector<OffMeshConnection>& offMeshConnections)
                 : mRecastMesh(recastMesh), mOffMeshConnections(offMeshConnections) {}
 
-            int compare(const std::string& other) const override;
+            int compare(const std::vector<unsigned char>& other) const override;
 
             bool isLess(const KeyView& other) const override
             {