[Java.Interop.Tools.Cecil] DirectoryAssemblyResolver+MemoryMappedFile (#1103)

Context: dotnet/linker#1130
Context: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1783420
In dotnet/linker#1130, their version of `DirectoryAssemblyResolver`
was reworked to use [`MemoryMappedFile`][0] in the .NET 6 time frame.
Port these changes to Java.Interop, as we have MSBuild tasks in
xamarin/xamarin-android that use `DirectoryAssemblyResolver`.
Primarily, the [`<GenerateJavaStubs/>` MSBuild task][1] uses
`DirectoryAssemblyResolver` to iterate over types in assembly to emit
Java source code and generate `AndroidManifest.xml`.
Note: `MemoryMappedFile` can *only* be used when we are *not* opening
the assembly as `.ReadWrite`. Trying to use `MemoryMappedFile` for
read+write scenarios would result in an `InvalidOperationException`:
error XAGJS7009: System.InvalidOperationException: Operation is not valid due to the current state of the object.
error XAGJS7009: at Mono.Cecil.Cil.DefaultSymbolWriterProvider.GetSymbolWriter(ModuleDefinition module, String fileName)
error XAGJS7009: at Mono.Cecil.ModuleWriter.GetSymbolWriter(ModuleDefinition module, String fq_name, ISymbolWriterProvider symbol_writer_provider, WriterParameters parameters)
error XAGJS7009: at Mono.Cecil.ModuleWriter.Write(ModuleDefinition module, Disposable`1 stream, WriterParameters parameters)
error XAGJS7009: at Mono.Cecil.ModuleWriter.WriteModule(ModuleDefinition module, Disposable`1 stream, WriterParameters parameters)
error XAGJS7009: at Mono.Cecil.ModuleDefinition.Write(String fileName, WriterParameters parameters)
error XAGJS7009: at Mono.Cecil.AssemblyDefinition.Write(String fileName, WriterParameters parameters)
error XAGJS7009: at Xamarin.Android.Tasks.MarshalMethodsAssemblyRewriter.Rewrite(DirectoryAssemblyResolver resolver, List`1 targetAssemblyPaths, Boolean brokenExceptionTransitions)
error XAGJS7009: at Xamarin.Android.Tasks.GenerateJavaStubs.Run(DirectoryAssemblyResolver res, Boolean useMarshalMethods)
error XAGJS7009: at Xamarin.Android.Tasks.GenerateJavaStubs.RunTask()
The results of these changes in a `dotnet new maui` project,
an initial clean build:
* Before MemoryMappedFile: GenerateJavaStubs = 1.318 s, 1 calls.
* After MemoryMappedFile: GenerateJavaStubs = 1.254 s, 1 calls.
Saving ~64ms or about ~5% in this example.
Note: The current version of the linker's resolver in .NET 8+ has
[moved to the dotnet/runtime repo][2].
[0]: https://learn.microsoft.com/dotnet/api/system.io.memorymappedfiles.memorymappedfile?view=net-8.0
[1]: https://github.com/xamarin/xamarin-android/blob/e694ba52a0cf5f45b213c8902bdbfb0ed348374a/src/Xamarin.Android.Build.Tasks/Tasks/GenerateJavaStubs.cs#L131
[2]: https://github.com/dotnet/runtime/blob/cd7d006030a7feace9076fa275fb5bffc1bf4a90/src/tools/illink/src/linker/Linker/AssemblyResolver.cs

Author: jonathanpeppers

src/Java.Interop.Tools.Cecil/Java.Interop.Tools.Cecil/DirectoryAssemblyResolver.cs

@@ -32,6 +32,7 @@
 usingSystem.Collections;
 usingSystem.Collections.Generic;
 usingSystem.IO;
+usingSystem.IO.MemoryMappedFiles;
 usingSystem.Linq;
 usingSystem.Reflection;
 
@@ -61,6 +62,7 @@ public class DirectoryAssemblyResolver : IAssemblyResolver {
 
 publicICollection<string>SearchDirectories{get;privateset;}
 
+readonlyList<MemoryMappedViewStream>viewStreams=newList<MemoryMappedViewStream>();
 Dictionary<string,AssemblyDefinition?>cache;
 boolloadDebugSymbols;
 Action<TraceLevel,string>logger;
@@ -103,6 +105,10 @@ protected virtual void Dispose (bool disposing)
 e.Value?.Dispose();
 }
 cache.Clear();
+foreach(varviewStreaminviewStreams){
+viewStream.Dispose();
+}
+viewStreams.Clear();
 }
 
 publicDictionary<string,AssemblyDefinition?>ToResolverCache()
@@ -160,14 +166,41 @@ protected virtual AssemblyDefinition ReadAssembly (string file)
 SymbolStream=loadReaderParameters.SymbolStream,
 };
 try{
-returnAssemblyDefinition.ReadAssembly(file,reader_parameters);
+returnLoadFromMemoryMappedFile(file,reader_parameters);
 }catch(Exceptionex){
 logger(
 TraceLevel.Verbose,
 $"Failed to read '{file}' with debugging symbols. Retrying to load it without it. Error details are logged below.");
 logger(TraceLevel.Verbose,$"{ex.ToString()}");
 reader_parameters.ReadSymbols=false;
-returnAssemblyDefinition.ReadAssembly(file,reader_parameters);
+returnLoadFromMemoryMappedFile(file,reader_parameters);
+}
+}
+
+AssemblyDefinitionLoadFromMemoryMappedFile(stringfile,ReaderParametersoptions)
+{
+// We can't use MemoryMappedFile when ReadWrite is true
+if(options.ReadWrite){
+returnAssemblyDefinition.ReadAssembly(file,options);
+}
+
+MemoryMappedViewStream?viewStream=null;
+try{
+// Create stream because CreateFromFile(string, ...) uses FileShare.None which is too strict
+usingvarfileStream=newFileStream(file,FileMode.Open,FileAccess.Read,FileShare.Read,4096,false);
+usingvarmappedFile=MemoryMappedFile.CreateFromFile(
+fileStream,null,fileStream.Length,MemoryMappedFileAccess.Read,HandleInheritability.None,true);
+viewStream=mappedFile.CreateViewStream(0,0,MemoryMappedFileAccess.Read);
+
+AssemblyDefinitionresult=ModuleDefinition.ReadModule(viewStream,options).Assembly;
+viewStreams.Add(viewStream);
+
+// We transferred the ownership of the viewStream to the collection.
+viewStream=null;
+
+returnresult;
+}finally{
+viewStream?.Dispose();
 }
 }