added benchmarks

ParadoxSaveParser.Benchmarks/ParserInputBenchmarks.cs

@@ -0,0 +1,29 @@
+using System.IO;
+using BenchmarkDotNet.Attributes;
+using BenchmarkDotNet.Engines;
+using ParadoxSaveParser.Lib;
+
+namespace ParadoxSaveParser.Benchmarks;
+
+/// <summary>
+///     SearchExpression only, parsing straight from the save file on disk:
+///     the file is opened inside the benchmark and is never preloaded into a byte[].
+///     Run it once with and once without the internal <c>MemoryStream</c> copy in
+///     <see cref="SaveParserEU4" /> to see what that copy buys.
+/// </summary>
+[MemoryDiagnoser]
+[SimpleJob(RunStrategy.Monitoring, launchCount: 1, warmupCount: 1, iterationCount: 5)]
+public class ParserInputBenchmarks
+{
+    private ISearchExpression _query = null!;
+
+    [GlobalSetup]
+    public void Setup() => _query = SearchExpressionCompiler.Compile(BenchData.PdxQuery);
+
+    [Benchmark(Description = "SearchExpression over FileStream")]
+    public long FromFile()
+    {
+        using var file = File.OpenRead(BenchData.PdxPath);
+        return Extractors.SearchExpressionFromStream(file, _query);
+    }
+}