From 53c3f95ac8fdbcbf6a36a589c2bd5ccd11b3efa1 Mon Sep 17 00:00:00 2001
From: elsid <elsid.mail@gmail.com>
Date: Mon, 7 Aug 2023 11:14:27 +0200
Subject: [PATCH] Avoid redundant copy for LandData underlying data

---
 components/esm/esmterrain.cpp | 69 +++++++++++++++++------------------
 components/esm/esmterrain.hpp | 15 +++++---
 2 files changed, 42 insertions(+), 42 deletions(-)

diff --git a/components/esm/esmterrain.cpp b/components/esm/esmterrain.cpp
index 18a267d51c..27f21b6a32 100644
--- a/components/esm/esmterrain.cpp
+++ b/components/esm/esmterrain.cpp
@@ -2,67 +2,64 @@
 
 #include "esmterrain.hpp"
 
+namespace
+{
+    constexpr std::uint16_t textures[ESM::Land::LAND_NUM_TEXTURES]{ 0 };
+
+    std::unique_ptr<const ESM::Land::LandData> loadData(const ESM::Land& land, int loadFlags)
+    {
+        std::unique_ptr<ESM::Land::LandData> result = std::make_unique<ESM::Land::LandData>();
+        land.loadData(loadFlags, *result);
+        return result;
+    }
+}
+
 ESM::LandData::LandData(const ESM::Land& land, int loadFlags)
-    : mLoadFlags(loadFlags)
+    : mData(loadData(land, loadFlags))
+    , mLoadFlags(mData->mDataLoaded)
+    , mMinHeight(mData->mMinHeight)
+    , mMaxHeight(mData->mMaxHeight)
     , mSize(Constants::CellSizeInUnits)
     , mLandSize(ESM::Land::LAND_SIZE)
     , mPlugin(land.getPlugin())
+    , mHeights(mData->mHeights)
+    , mNormals(mData->mNormals)
+    , mColors(mData->mColours)
+    , mTextures(mData->mTextures)
 {
-    ESM::Land::LandData data;
-    land.loadData(loadFlags, data);
-    mLoadFlags = data.mDataLoaded;
-    std::span<const float> heights(data.mHeights);
-    mHeights = std::vector(heights.begin(), heights.end());
-
-    std::span<const std::int8_t> normals(data.mNormals);
-    mNormals = std::vector(normals.begin(), normals.end());
-
-    std::span<const std::uint8_t> colors(data.mColours);
-    mColors = std::vector(colors.begin(), colors.end());
-
-    std::span<const uint16_t> textures(data.mTextures);
-    mTextures = std::vector(textures.begin(), textures.end());
-
-    mMinHeight = data.mMinHeight;
-    mMaxHeight = data.mMaxHeight;
 }
 
 ESM::LandData::LandData(const ESM4::Land& land, int /*loadFlags*/)
     : mLoadFlags(land.mDataTypes) // ESM4::Land is always fully loaded. TODO: implement lazy loading
+    , mHeightsData(ESM4::Land::sLandNumVerts)
+    , mMinHeight(std::numeric_limits<float>::max())
+    , mMaxHeight(std::numeric_limits<float>::lowest())
     , mSize(Constants::ESM4CellSizeInUnits)
     , mLandSize(ESM4::Land::sVertsPerSide)
+    , mNormals(land.mVertNorm)
+    , mColors(land.mVertColr)
+    , mTextures(textures)
 {
-
-    mMinHeight = std::numeric_limits<float>::max();
-    mMaxHeight = std::numeric_limits<float>::lowest();
-    mHeights.resize(ESM4::Land::sLandNumVerts);
-    mTextures.resize(ESM::Land::LAND_NUM_TEXTURES);
-    std::fill(mTextures.begin(), mTextures.end(), 0);
-
-    float row_offset = land.mHeightMap.heightOffset;
+    float rowOffset = land.mHeightMap.heightOffset;
     for (int y = 0; y < mLandSize; y++)
     {
-        row_offset += land.mHeightMap.gradientData[y * mLandSize];
+        rowOffset += land.mHeightMap.gradientData[y * mLandSize];
 
-        const float heightY = row_offset * ESM4::Land::sHeightScale;
-        mHeights[y * mLandSize] = heightY;
+        const float heightY = rowOffset * ESM4::Land::sHeightScale;
+        mHeightsData[y * mLandSize] = heightY;
         mMinHeight = std::min(mMinHeight, heightY);
         mMaxHeight = std::max(mMaxHeight, heightY);
 
-        float colOffset = row_offset;
+        float colOffset = rowOffset;
         for (int x = 1; x < mLandSize; x++)
         {
             colOffset += land.mHeightMap.gradientData[y * mLandSize + x];
             const float heightX = colOffset * ESM4::Land::sHeightScale;
             mMinHeight = std::min(mMinHeight, heightX);
             mMaxHeight = std::max(mMaxHeight, heightX);
-            mHeights[x + y * mLandSize] = heightX;
+            mHeightsData[x + y * mLandSize] = heightX;
         }
     }
 
-    std::span<const std::int8_t> normals(land.mVertNorm);
-    mNormals = std::vector(normals.begin(), normals.end());
-
-    std::span<const std::uint8_t> colors(land.mVertColr);
-    mColors = std::vector(colors.begin(), colors.end());
+    mHeights = mHeightsData;
 }
diff --git a/components/esm/esmterrain.hpp b/components/esm/esmterrain.hpp
index 0f2a5eb1cb..8aaf4d078c 100644
--- a/components/esm/esmterrain.hpp
+++ b/components/esm/esmterrain.hpp
@@ -2,6 +2,7 @@
 #define COMPONENTS_ESM_ESMTERRAIN
 
 #include <cstdint>
+#include <memory>
 #include <span>
 #include <vector>
 
@@ -15,8 +16,8 @@ namespace ESM
     public:
         ~LandData() = default;
         LandData() = default;
-        LandData(const ESM::Land& Land, int loadFLags);
-        LandData(const ESM4::Land& Land, int loadFLags);
+        LandData(const ESM::Land& Land, int loadFlags);
+        LandData(const ESM4::Land& Land, int loadFlags);
 
         std::span<const float> getHeights() const { return mHeights; }
         std::span<const std::int8_t> getNormals() const { return mNormals; }
@@ -30,16 +31,18 @@ namespace ESM
         int getPlugin() const { return mPlugin; }
 
     private:
+        std::unique_ptr<const ESM::Land::LandData> mData;
         int mLoadFlags = 0;
+        std::vector<float> mHeightsData;
         float mMinHeight = 0.f;
         float mMaxHeight = 0.f;
         float mSize = 0.f;
         int mLandSize = 0;
         int mPlugin = 0;
-        std::vector<float> mHeights;
-        std::vector<std::int8_t> mNormals;
-        std::vector<std::uint8_t> mColors;
-        std::vector<std::uint16_t> mTextures;
+        std::span<const float> mHeights;
+        std::span<const std::int8_t> mNormals;
+        std::span<const std::uint8_t> mColors;
+        std::span<const std::uint16_t> mTextures;
     };
 
 }