[macOS] Allow loading of AOT snapshots and instructions from elf bundle (flutter#21670)

Author: iskakaushik

shell/platform/darwin/macos/framework/Source/FlutterEngine.mm

@@ -7,6 +7,7 @@
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
 
 #include <algorithm>
+#include <filesystem>
 #include <vector>
 
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterDartProject_Internal.h"
@@ -162,6 +163,16 @@ static bool OnAcquireExternalTexture(FlutterEngine* engine,
 
 #pragma mark -
 
+namespace {
+
+struct AotDataDeleter {
+  void operator()(FlutterEngineAOTData aot_data) { FlutterEngineCollectAOTData(aot_data); }
+};
+
+using UniqueAotDataPtr = std::unique_ptr<_FlutterEngineAOTData, AotDataDeleter>;
+
+}
+
 @implementation FlutterEngine {
   // The embedding-API-level engine object.
   FLUTTER_API_SYMBOL(FlutterEngine) _engine;
@@ -184,6 +195,9 @@ @implementation FlutterEngine {
 
   // A mapping of textureID to internal FlutterExternalTextureGL adapter.
   NSMutableDictionary<NSNumber*, FlutterExternalTextureGL*>* _textures;
+
+  // Pointer to the Dart AOT snapshot and instruction data.
+  UniqueAotDataPtr _aotData;
 }
 
 - (instancetype)initWithName:(NSString*)labelPrefix project:(FlutterDartProject*)project {
@@ -274,6 +288,11 @@ - (BOOL)runWithEntrypoint:(NSString*)entrypoint {
   };
   flutterArguments.custom_task_runners = &custom_task_runners;
 
+  _aotData = [self loadAotData:flutterArguments.assets_path];
+  if (_aotData) {
+    flutterArguments.aot_data = _aotData.get();
+  }
+
   FlutterEngineResult result = FlutterEngineInitialize(
       FLUTTER_ENGINE_VERSION, &rendererConfig, &flutterArguments, (__bridge void*)(self), &_engine);
   if (result != kSuccess) {
@@ -293,6 +312,33 @@ - (BOOL)runWithEntrypoint:(NSString*)entrypoint {
   return YES;
 }
 
+- (UniqueAotDataPtr)loadAotData:(std::string)assetsDir {
+  if (!FlutterEngineRunsAOTCompiledDartCode()) {
+    return nullptr;
+  }
+
+  std::filesystem::path assetsFsDir(assetsDir);
+  std::filesystem::path elfFile("app_elf_snapshot.so");
+  auto fullElfPath = assetsFsDir / elfFile;
+
+  if (!std::filesystem::exists(fullElfPath)) {
+    return nullptr;
+  }
+
+  FlutterEngineAOTDataSource source = {};
+  source.type = kFlutterEngineAOTDataSourceTypeElfPath;
+  source.elf_path = fullElfPath.c_str();
+
+  FlutterEngineAOTData data = nullptr;
+  auto result = FlutterEngineCreateAOTData(&source, &data);
+  if (result != kSuccess) {
+    NSLog(@"Failed to load AOT data from: %@", @(fullElfPath.c_str()));
+    return nullptr;
+  }
+
+  return UniqueAotDataPtr(data);
+}
+
 - (void)setViewController:(FlutterViewController*)controller {
   _viewController = controller;
   _mainOpenGLContext = controller.flutterView.openGLContext;