From 91364c6a7ca50d1fee2c4bb8ed34fed66449a499 Mon Sep 17 00:00:00 2001
From: majorro <majorrowk@gmail.com>
Date: Mon, 13 Jan 2025 23:28:26 +0300
Subject: [PATCH] stackalloc readtables

---
 src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs      | 6 +++---
 src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs    | 8 +++-----
 .../Compressors/Rar/UnpackV1/UnpackUtility.cs             | 5 ++---
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs b/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs
index 6cadcede..1af0965c 100644
--- a/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs
+++ b/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs
@@ -866,9 +866,9 @@ internal sealed partial class Unpack : BitInput, IRarUnpack, IDisposable
 
     private bool ReadTables()
     {
-        var bitLength = new byte[PackDef.BC];
+        Span<byte> bitLength = stackalloc byte[PackDef.BC];
+        Span<byte> table = stackalloc byte[PackDef.HUFF_TABLE_SIZE];
 
-        var table = new byte[PackDef.HUFF_TABLE_SIZE];
         if (inAddr > readTop - 25)
         {
             if (!unpReadBuf())
@@ -996,7 +996,7 @@ internal sealed partial class Unpack : BitInput, IRarUnpack, IDisposable
 
         // memcpy(unpOldTable,table,sizeof(unpOldTable));
 
-        Buffer.BlockCopy(table, 0, unpOldTable, 0, unpOldTable.Length);
+        table.CopyTo(unpOldTable);
         return (true);
     }
 
diff --git a/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs b/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs
index 3a5d008d..33900961 100644
--- a/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs
+++ b/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs
@@ -391,11 +391,9 @@ internal partial class Unpack
 
     private bool ReadTables20()
     {
-        var BitLength = new byte[PackDef.BC20];
-        var Table = new byte[PackDef.MC20 * 4];
-        int TableSize,
-            N,
-            I;
+        Span<byte> BitLength = stackalloc byte[PackDef.BC20];
+        Span<byte> Table = stackalloc byte[PackDef.MC20 * 4];
+        int TableSize, N, I;
         if (inAddr > readTop - 25)
         {
             if (!unpReadBuf())
diff --git a/src/SharpCompress/Compressors/Rar/UnpackV1/UnpackUtility.cs b/src/SharpCompress/Compressors/Rar/UnpackV1/UnpackUtility.cs
index b501337b..c388cdcb 100644
--- a/src/SharpCompress/Compressors/Rar/UnpackV1/UnpackUtility.cs
+++ b/src/SharpCompress/Compressors/Rar/UnpackV1/UnpackUtility.cs
@@ -181,13 +181,12 @@ internal static class UnpackUtility
         return (dec.DecodeNum[N]);
     }
 
-    internal static void makeDecodeTables(byte[] lenTab, int offset, Decode.Decode dec, int size)
+    internal static void makeDecodeTables(Span<byte> lenTab, int offset, Decode.Decode dec, int size)
     {
         Span<int> lenCount = stackalloc int[16];
         Span<int> tmpPos = stackalloc int[16];
         int i;
-        long M,
-            N;
+        long M, N;
 
         new Span<int>(dec.DecodeNum).Clear(); // memset(Dec->DecodeNum,0,Size*sizeof(*Dec->DecodeNum));