From 68232374abb583fc20038b940ea0350ab31aa686 Mon Sep 17 00:00:00 2001
From: FenPhoenix <FenPhoenix@users.noreply.github.com>
Date: Sun, 3 Sep 2023 21:32:50 -0700
Subject: [PATCH] Reduce SharpCompress allocs some more

---
 .../Archives/SevenZip/SevenZipArchiveEntry.cs |  2 ++
 .../Common/SevenZip/ArchiveDatabase.cs        |  7 +++---
 .../Common/SevenZip/ArchiveReader.cs          | 25 +++++++++++++------
 SharpCompress/Common/SevenZip/CFolder.cs      | 15 +++++++++--
 4 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/SharpCompress/Archives/SevenZip/SevenZipArchiveEntry.cs b/SharpCompress/Archives/SevenZip/SevenZipArchiveEntry.cs
index c22c06ec4..6adb45a76 100644
--- a/SharpCompress/Archives/SevenZip/SevenZipArchiveEntry.cs
+++ b/SharpCompress/Archives/SevenZip/SevenZipArchiveEntry.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.CompilerServices;
 
 namespace SharpCompress.Archives.SevenZip;
 
@@ -38,6 +39,7 @@ public DateTime? LastModifiedTime
 
     public bool IsDirectory;
 
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
     internal void Reset()
     {
         HasStream = true;
diff --git a/SharpCompress/Common/SevenZip/ArchiveDatabase.cs b/SharpCompress/Common/SevenZip/ArchiveDatabase.cs
index ca5d224e0..66207de3b 100644
--- a/SharpCompress/Common/SevenZip/ArchiveDatabase.cs
+++ b/SharpCompress/Common/SevenZip/ArchiveDatabase.cs
@@ -1,7 +1,7 @@
 #nullable disable
 
 using System;
-using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 using SharpCompress.Archives.SevenZip;
 using static AL_Common.Common;
 
@@ -13,17 +13,18 @@ internal sealed class ArchiveDatabase
     internal byte _minorVersion;
     internal long _startPositionAfterHeader;
 
-    internal readonly List<CFolder> _folders = new();
+    internal readonly ListFast<CFolder> _folders = new(0);
     internal readonly ListFast<int> _numUnpackStreamsVector = new(0);
     internal readonly ListFast<SevenZipArchiveEntry> _files = new(0);
 
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
     internal void Clear()
     {
         _majorVersion = 0;
         _minorVersion = 0;
         _startPositionAfterHeader = 0;
 
-        _folders.Clear();
+        _folders.ClearFast();
         _numUnpackStreamsVector.ClearFast();
         _files.ClearFast();
     }
diff --git a/SharpCompress/Common/SevenZip/ArchiveReader.cs b/SharpCompress/Common/SevenZip/ArchiveReader.cs
index 911eec2a9..9078b6cee 100644
--- a/SharpCompress/Common/SevenZip/ArchiveReader.cs
+++ b/SharpCompress/Common/SevenZip/ArchiveReader.cs
@@ -261,7 +261,7 @@ private void ReadAttributeVector(
     private void GetNextFolderItem(CFolder folder)
     {
         int numCoders = ReadNum();
-        folder._coders = new List<CCoderInfo>(numCoders);
+        folder._coders.ClearAndEnsureCapacity(numCoders);
         int numInStreams = 0;
         int numOutStreams = 0;
         for (int i = 0; i < numCoders; i++)
@@ -319,7 +319,7 @@ private void GetNextFolderItem(CFolder folder)
         }
 
         int numBindPairs = numOutStreams - 1;
-        folder._bindPairs = new List<CBindPair>(numBindPairs);
+        folder._bindPairs.ClearAndEnsureCapacity(numBindPairs);
         for (int i = 0; i < numBindPairs; i++)
         {
             var bp = new CBindPair
@@ -419,12 +419,21 @@ private void ReadUnpackInfo(List<byte[]> dataVector)
         {
             streamSwitch.Set(this, dataVector);
 
-            db._folders.ClearAndEnsureCapacity(numFolders);
+            db._folders.SetRecycleState(numFolders, 25_000);
             for (int i = 0; i < numFolders; i++)
             {
-                var f = new CFolder();
-                db._folders.Add(f);
-                GetNextFolderItem(f);
+                CFolder folder = db._folders[i];
+                if (folder != null)
+                {
+                    folder.Reset();
+                }
+                else
+                {
+                    folder = new CFolder();
+                    db._folders[i] = folder;
+                }
+
+                GetNextFolderItem(folder);
             }
         }
 
@@ -609,8 +618,10 @@ out _
 
         var dataVector = new List<byte[]>(db._folders.Count);
         const int packIndex = 0;
-        foreach (CFolder folder in db._folders)
+        for (int folderIndex = 0; folderIndex < db._folders.Count; folderIndex++)
         {
+            CFolder folder = db._folders[folderIndex];
+
             long oldDataStartPos = dataStartPos;
             int myPackSizesLength = folder._packStreams.Count;
             long[] myPackSizes = _context.LongArrayPool.Rent(myPackSizesLength);
diff --git a/SharpCompress/Common/SevenZip/CFolder.cs b/SharpCompress/Common/SevenZip/CFolder.cs
index cf47098a9..7e33f6898 100644
--- a/SharpCompress/Common/SevenZip/CFolder.cs
+++ b/SharpCompress/Common/SevenZip/CFolder.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 using AL_Common;
 using SharpCompress.Archives.SevenZip;
 using SharpCompress.Compressors.LZMA;
@@ -8,14 +9,24 @@ namespace SharpCompress.Common.SevenZip;
 
 internal sealed class CFolder
 {
-    internal List<CCoderInfo> _coders = new();
-    internal List<CBindPair> _bindPairs = new();
+    internal readonly List<CCoderInfo> _coders = new();
+    internal readonly List<CBindPair> _bindPairs = new();
     internal readonly List<int> _packStreams = new();
     internal readonly List<long> _unpackSizes = new();
     internal uint? _unpackCrc;
 
     internal bool UnpackCrcDefined => _unpackCrc != null;
 
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    internal void Reset()
+    {
+        _coders.Clear();
+        _bindPairs.Clear();
+        _packStreams.Clear();
+        _unpackSizes.Clear();
+        _unpackCrc = null;
+    }
+
     public long GetUnpackSize()
     {
         if (_unpackSizes.Count == 0)