From e09016cea57cb8c56c6209bcc88f3b773063ada1 Mon Sep 17 00:00:00 2001
From: BruceChen <MrChen131217@gmail.com>
Date: Tue, 30 Aug 2022 12:33:13 +0800
Subject: [PATCH] Improve ReadBlockStatesField

---
 MinecraftClient/Mapping/Chunk.cs               | 18 ++++++++++++++----
 MinecraftClient/Protocol/Handlers/DataTypes.cs |  6 ++++++
 .../Protocol/Handlers/Protocol18Terrain.cs     | 13 ++++++++-----
 3 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/MinecraftClient/Mapping/Chunk.cs b/MinecraftClient/Mapping/Chunk.cs
index 66039f43..89991bfd 100644
--- a/MinecraftClient/Mapping/Chunk.cs
+++ b/MinecraftClient/Mapping/Chunk.cs
@@ -19,7 +19,17 @@ namespace MinecraftClient.Mapping
         /// <summary>
         /// Blocks contained into the chunk
         /// </summary>
-        private readonly Block[,,] blocks = new Block[SizeX, SizeY, SizeZ];
+        private readonly Block[] blocks;
+
+        public Chunk()
+        {
+            this.blocks = new Block[SizeY * SizeZ * SizeX];
+        }
+
+        public Chunk(Block[] blocks)
+        {
+            this.blocks = blocks;
+        }
 
         /// <summary>
         /// Read, or set the specified block
@@ -39,7 +49,7 @@ namespace MinecraftClient.Mapping
                 if (blockZ < 0 || blockZ >= SizeZ)
                     throw new ArgumentOutOfRangeException("blockZ", "Must be between 0 and " + (SizeZ - 1) + " (inclusive)");
 
-                return blocks[blockY, blockZ, blockX];
+                return blocks[(blockY << 8) | (blockZ << 4) | blockX];
             }
             set
             {
@@ -50,7 +60,7 @@ namespace MinecraftClient.Mapping
                 if (blockZ < 0 || blockZ >= SizeZ)
                     throw new ArgumentOutOfRangeException("blockZ", "Must be between 0 and " + (SizeZ - 1) + " (inclusive)");
 
-                blocks[blockY, blockZ, blockX] = value;
+                blocks[(blockY << 8) | (blockZ << 4) | blockX] = value;
             }
         }
 
@@ -64,7 +74,7 @@ namespace MinecraftClient.Mapping
         [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
         public void SetWithoutCheck(int blockX, int blockY, int blockZ, Block block)
         {
-            blocks[blockY, blockZ, blockX] = block;
+            blocks[(blockY << 8) | (blockZ << 4) | blockX] = block;
         }
 
         /// <summary>
diff --git a/MinecraftClient/Protocol/Handlers/DataTypes.cs b/MinecraftClient/Protocol/Handlers/DataTypes.cs
index 2ca27533..a352757c 100644
--- a/MinecraftClient/Protocol/Handlers/DataTypes.cs
+++ b/MinecraftClient/Protocol/Handlers/DataTypes.cs
@@ -46,6 +46,12 @@ namespace MinecraftClient.Protocol.Handlers
             return result;
         }
 
+        /// <summary>
+        /// Read some data from a cache of bytes and remove it from the cache
+        /// </summary>
+        /// <param name="cache">Cache of bytes to read from</param>
+        /// <param name="dest">Storage results</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
         public void ReadDataReverse(Queue<byte> cache, Span<byte> dest)
         {
             for (int i = (dest.Length - 1); i >= 0; --i)
diff --git a/MinecraftClient/Protocol/Handlers/Protocol18Terrain.cs b/MinecraftClient/Protocol/Handlers/Protocol18Terrain.cs
index 84e2fe93..8685ecea 100644
--- a/MinecraftClient/Protocol/Handlers/Protocol18Terrain.cs
+++ b/MinecraftClient/Protocol/Handlers/Protocol18Terrain.cs
@@ -86,9 +86,10 @@ namespace MinecraftClient.Protocol.Handlers
                 //// Block IDs are packed in the array of 64-bits integers
                 dataTypes.SkipNextVarInt(cache);
                 Span<byte> entryDataByte = stackalloc byte[8];
+                Span<long> entryDataLong = MemoryMarshal.Cast<byte, long>(entryDataByte);
                 dataTypes.ReadDataReverse(cache, entryDataByte); // read long
 
-                Chunk chunk = new();
+                Block[] blocks = new Block[Chunk.SizeX * Chunk.SizeY * Chunk.SizeZ];
                 int startOffset = 0 - bitsPerEntry;
                 for (int blockY = 0; blockY < Chunk.SizeY; blockY++)
                 {
@@ -112,7 +113,7 @@ namespace MinecraftClient.Protocol.Handlers
 
                             // NOTICE: In the future a single ushort may not store the entire block id;
                             // the Block class may need to change if block state IDs go beyond 65535
-                            ushort blockId = (ushort)((MemoryMarshal.Read<long>(entryDataByte) >> startOffset) & valueMask);
+                            uint blockId = (uint)(entryDataLong[0] >> startOffset) & valueMask;
 
                             // Map small IDs to actual larger block IDs
                             if (usePalette)
@@ -127,15 +128,17 @@ namespace MinecraftClient.Protocol.Handlers
                                         blockNumber));
                                 }
 
-                                blockId = (ushort)palette[blockId];
+                                blockId = palette[(int)blockId];
                             }
 
+                            Block block = new((ushort)blockId);
+
                             // We have our block, save the block into the chunk
-                            chunk.SetWithoutCheck(blockX, blockY, blockZ, new Block(blockId));
+                            blocks[(blockY << 8) | (blockZ << 4) | blockX] = block;
                         }
                     }
                 }
-                return chunk;
+                return new Chunk(blocks);
             }
         }