chore: initialize standalone UPM package

Editor/PostProcessorAssemblyResolver.cs

@@ -0,0 +1,84 @@
+#nullable enable
+
+using System.Collections.Generic;
+using System.IO;
+using System.Threading;
+using Mono.Cecil;
+using Unity.CompilationPipeline.Common.ILPostProcessing;
+
+namespace ShrinkShared.CodeGen
+{
+    internal sealed class PostProcessorAssemblyResolver : IAssemblyResolver
+    {
+        private readonly string[] _references;
+        private readonly Dictionary<string, AssemblyDefinition> _cache = new();
+        private AssemblyDefinition? _self;
+
+        public PostProcessorAssemblyResolver(ICompiledAssembly compiledAssembly)
+        {
+            _references = compiledAssembly.References;
+        }
+
+        public void AddAssemblyDefinitionBeingOperatedOn(AssemblyDefinition assemblyDefinition)
+        {
+            _self = assemblyDefinition;
+        }
+
+        public AssemblyDefinition? Resolve(AssemblyNameReference name)
+            => Resolve(name, new ReaderParameters(ReadingMode.Deferred));
+
+        public AssemblyDefinition? Resolve(AssemblyNameReference name, ReaderParameters parameters)
+        {
+            lock (_cache)
+            {
+                if (name.Name == _self?.Name.Name)
+                    return _self;
+
+                var path = FindPath(name);
+                if (path == null)
+                    return null;
+
+                var key = $"{path}{File.GetLastWriteTime(path)}";
+                if (_cache.TryGetValue(key, out var cached))
+                    return cached;
+
+                parameters.AssemblyResolver = this;
+                var assembly = AssemblyDefinition.ReadAssembly(ReadFileWithRetry(path), parameters);
+                _cache[key] = assembly;
+                return assembly;
+            }
+        }
+
+        private string? FindPath(AssemblyNameReference name)
+        {
+            foreach (var reference in _references)
+            {
+                if (Path.GetFileNameWithoutExtension(reference) == name.Name)
+                    return reference;
+            }
+
+            return null;
+        }
+
+        private static MemoryStream ReadFileWithRetry(string path, int retries = 5)
+        {
+            for (var i = 0; i < retries; i++)
+            {
+                try
+                {
+                    return new MemoryStream(File.ReadAllBytes(path));
+                }
+                catch (IOException) when (i < retries - 1)
+                {
+                    Thread.Sleep(100);
+                }
+            }
+
+            throw new IOException($"[ShrinkShared.CodeGen] 无法读取文件: {path}");
+        }
+
+        public void Dispose()
+        {
+        }
+    }
+}