[class-parse] Use BufferedStream to increase performance (#1092)

jpobst · web-flow · commit a172402ae40e · 2023-04-10T16:01:44.000-04:00
While building `AndroidX.sln`, `class-parse` is taking up a considerable amount of time. After some quick profiling, this seems to be caused by reading from a `ZipStream` one or two bytes at a time. Wrapping the `ZipStream` in a `BufferedStream` makes `class-parse` about 10x faster on larger test cases. | | 0d5cddb | Now | | --------------------------------------------------------------- | --------: | --------: | | `class-parse` on API-33 `android.jar` (26.5 MB) | 16.675s | 2.759s | | `class-parse` on `androidx.compose.runtime.runtime` (1.044 MB) | 9.713s | .893s | | Total `class-parse` time building `AndroidX.sln` | 5:48.46m | 2:09.73m | | Total time building `AndroidX.sln` | 7:40.19m | 4:42.34m |
diff --git a/src/Xamarin.Android.Tools.Bytecode/ClassPath.cs b/src/Xamarin.Android.Tools.Bytecode/ClassPath.cs
@@ -72,7 +72,8 @@ public void Load (Stream jarStream, bool leaveOpen = false)
 						if (!ClassFile.IsClassFile (s) || entry.Name.EndsWith (".jnilib", StringComparison.OrdinalIgnoreCase))
 							continue;
 					}
-					using (var s = entry.Open ()) {
+					using (var entry_stream = entry.Open ())
+					using (var s = new BufferedStream (entry_stream)) {
 						try {
 							var c   = new ClassFile (s);
 							Add (c);
