Add GetMemoryMappedStreamIfPossible

Fixes #10

ValvePak/ValvePak.Test/MemoryMapTest.cs

@@ -0,0 +1,38 @@
+using System;
+using System.IO;
+using System.IO.MemoryMappedFiles;
+using NUnit.Framework;
+using SteamDatabase.ValvePak;
+
+namespace Tests
+{
+ [TestFixture]
+ public class MemoryMappedTest
+ {
+ [Test]
+ public void ReturnsMemoryMappedViewStream()
+ {
+ var path = Path.Combine(TestContext.CurrentContext.TestDirectory, "Files", "steamdb_test_dir.vpk");
+
+ using var package = new Package();
+ package.Read(path);
+
+ using var stream = package.GetMemoryMappedStreamIfPossible(package.FindEntry("kitten.jpg"));
+
+ Assert.That(stream, Is.InstanceOf<MemoryMappedViewStream>());
+ }
+
+ [Test]
+ public void ReturnsMemoryStream()
+ {
+ var path = Path.Combine(TestContext.CurrentContext.TestDirectory, "Files", "steamdb_test_single.vpk");
+
+ using var package = new Package();
+ package.Read(path);
+
+ using var stream = package.GetMemoryMappedStreamIfPossible(package.FindEntry("kitten.jpg"));
+
+ Assert.That(stream, Is.InstanceOf<MemoryStream>());
+ }
+ }
+}

ValvePak/ValvePak/Package.Read.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.IO.MemoryMappedFiles;
 using System.Runtime.CompilerServices;
 using System.Text;
 
@@ -343,6 +344,31 @@ private Stream GetFileStream(ushort archiveIndex)
  return stream;
  }
 
+ /// <summary>
+ /// Returns <see cref="MemoryMappedViewStream"/> when possible, otherwise reads entry into a byte array and returns <see cref="MemoryStream"/>.
+ /// This only works on split packages (<see cref="IsDirVPK"/>) and when entries have no preload bytes.
+ /// </summary>
+ /// <param name="entry">Package entry.</param>
+ /// <returns>Stream for a given package entry contents.</returns>
+ public Stream GetMemoryMappedStreamIfPossible(PackageEntry entry)
+ {
+ if (!IsDirVPK || entry.ArchiveIndex == 0x7FFF || entry.SmallData.Length > 0)
+ {
+ ReadEntry(entry, out var output, false);
+
+ return new MemoryStream(output);
+ }
+
+ if (!MemoryMappedPaks.TryGetValue(entry.ArchiveIndex, out var stream))
+ {
+ var path = $"{FileName}_{entry.ArchiveIndex:D3}.vpk";
+ stream = MemoryMappedFile.CreateFromFile(path, FileMode.Open, null, 0, MemoryMappedFileAccess.Read);
+ MemoryMappedPaks[entry.ArchiveIndex] = stream;
+ }
+
+ return stream.CreateViewStream(entry.Offset, entry.Length, MemoryMappedFileAccess.Read);
+ }
+
  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  private string ReadNullTermUtf8String(MemoryStream ms)
  {

ValvePak/ValvePak/Package.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.IO.MemoryMappedFiles;
 
 namespace SteamDatabase.ValvePak
 {
@@ -17,6 +18,7 @@ public partial class Package : IDisposable
  public const char DirectorySeparatorChar = '/';
 
  private BinaryReader Reader;
+ private readonly Dictionary<int, MemoryMappedFile> MemoryMappedPaks = [];
 
  /// <summary>
  /// Gets the file name.
@@ -111,10 +113,20 @@ public void Dispose()
 
  protected virtual void Dispose(bool disposing)
  {
- if (disposing && Reader != null)
+ if (disposing)
  {
- Reader.Dispose();
- Reader = null;
+ if (Reader != null)
+ {
+ Reader.Dispose();
+ Reader = null;
+ }
+
+ foreach (var stream in MemoryMappedPaks.Values)
+ {
+ stream.Dispose();
+ }
+
+ MemoryMappedPaks.Clear();
  }
  }