Disabled in memory caching of decompressed zip content in the VFS

Author: martindevans

Wazzy.Tests/TestFolder.zip

@@ -0,0 +1,20 @@
+using Wazzy.WasiSnapshotPreview1.FileSystem;
+using Wazzy.WasiSnapshotPreview1.FileSystem.Implementations.VirtualFileSystem.Builder;
+
+namespace Wazzy.Tests;
+
+[TestClass]
+public class VirtualFileSystemTests
+{
+    [TestMethod]
+    public void ReadMappedZipEntry()
+    {
+        var vfs = (IWasiFileSystem)new VirtualFileSystemBuilder()
+            .Readonly(true)
+            .WithVirtualRoot(root =>
+            {
+                root.MapReadonlyZipArchiveDirectory("TestFolder", "TestFolder.zip");
+            })
+            .Build();
+    }
+}

Wazzy.Tests/VirtualFileSystemTests.cs

@@ -56,6 +56,9 @@
     <None Update="Scripts\Simple_Async.wasm">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Update="TestFolder.zip">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
     <None Update="wasi-testsuite\tests\assemblyscript\testsuite\args_get-multiple-arguments.json">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>

Wazzy.Tests/Wazzy.Tests.csproj

@@ -159,18 +159,20 @@ public DirectoryBuilder MapDirectory(
     /// </remarks>
     /// <param name="name"></param>
     /// <param name="hostPath"></param>
+    /// <param name="contentCaching">Set whether or not decompressed file content should be cached in memory after the first read</param>
     /// <returns></returns>
     public DirectoryBuilder MapReadonlyZipArchiveDirectory(
         string name,
-        string hostPath)
+        string hostPath,
+        bool contentCaching = false)
     {
         if (!File.Exists(hostPath))
             throw new ArgumentException($"File {hostPath} does not exist", nameof(hostPath));
 
         var path = _fullPath + '/' + ValidatePath(name);
 
         _contentConstructors.Add(
-            (path, context => new MappedZipArchiveDirectoryContent(hostPath, context.Clock))
+            (path, context => new MappedZipArchiveDirectoryContent(hostPath, context.Clock, contentCaching))
         );
 
         return this;

Wazzy/WasiSnapshotPreview1/FileSystem/Implementations/VirtualFileSystem/Builder/DirectoryBuilder.cs

@@ -47,9 +47,12 @@ public override IReadOnlyList<DirectoryItem> EnumerateChildren(ulong timestamp)
     public ulong ModificationTime { get; set; }
     public ulong ChangeTime { get; set; }
 
-    public MappedZipArchiveDirectoryContent(string archivePath, IVFSClock clock)
+    private readonly bool _contentCaching;
+
+    public MappedZipArchiveDirectoryContent(string archivePath, IVFSClock clock, bool contentCaching)
         : this(File.OpenRead(archivePath), clock)
     {
+        _contentCaching = contentCaching;
     }
 
     public MappedZipArchiveDirectoryContent(Stream archiveStream, IVFSClock clock)
@@ -225,7 +228,7 @@ private MappedZipEntryFile GetOrCreateFileByEntry(string entry)
     {
         if (!_fileEntryCache.TryGetValue(entry, out var file))
         {
-            file = new MappedZipEntryFile(this, entry);
+            file = new MappedZipEntryFile(this, entry, _contentCaching);
             _fileEntryCache[entry] = file;
         }
 

Wazzy/WasiSnapshotPreview1/FileSystem/Implementations/VirtualFileSystem/Directories/MappedZipArchiveDirectoryContent.cs

@@ -74,8 +74,9 @@ public override void Truncate(ulong timestamp, long size)
         }
     }
 
-    public MappedZipEntryFile(MappedZipArchiveDirectoryContent archive, string fullPath)
+    public MappedZipEntryFile(MappedZipArchiveDirectoryContent archive, string fullPath, bool contentCaching)
     {
+        _contentCaching = contentCaching;
         _entry = archive.GetEntry(fullPath) ?? throw new InvalidOperationException("No such ZipArchive entry");
     }
 
@@ -85,22 +86,30 @@ public MappedZipEntryFile(MappedZipArchiveDirectoryContent archive, string fullP
     public ulong ModificationTime { get; set; }
     public ulong ChangeTime { get; set; }
 
+    private readonly bool _contentCaching;
     private readonly ZipArchiveEntry _entry;
     private byte[]? _decompressedCache;
 
     public ulong Size => checked((ulong)_entry.Length);
 
     private byte[] GetDecompressedContent()
     {
-        if (_decompressedCache == null)
-        {
-            using var stream = _entry.Open();
-            _decompressedCache = new byte[_entry.Length];
-            var output = new MemoryStream(_decompressedCache);
-            stream.CopyTo(output);
-        }
+        var content = _decompressedCache ?? Decompress();
+
+        if (_contentCaching)
+            _decompressedCache = content;
+
+        return content;
+    }
+
+    private byte[] Decompress()
+    {
+        using var stream = _entry.Open();
+        var content = new byte[_entry.Length];
+        var output = new MemoryStream(content);
+        stream.CopyTo(output);
 
-        return _decompressedCache;
+        return content;
     }
 
     public IFilesystemEntry ToInMemory()

Wazzy/WasiSnapshotPreview1/FileSystem/Implementations/VirtualFileSystem/Files/MappedZipEntryFile.cs

@@ -6,7 +6,7 @@
     <Nullable>enable</Nullable>
     <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
     <Title>Wazzy</Title>
-    <Version>0.0.38</Version>
+    <Version>0.0.39</Version>
     <Authors>Martin Evans</Authors>
     <Description>A pure C# implementation of WASI</Description>
     <PackageProjectUrl>https://github.com/martindevans/Wazzy</PackageProjectUrl>