chore: import upstream snapshot with attribution

express/ExecutorScope.cpp

@@ -0,0 +1,72 @@
+//
+//  ExecutorScope.cpp
+//  MNN
+//
+//  Created by MNN on 2020/10/26.
+//  Copyright © 2018, Alibaba Group Holding Limited
+//
+
+#include <thread>
+#include <mutex>
+#include <MNN/expr/Executor.hpp>
+#include <MNN/expr/Scope.hpp>
+#include <MNN/expr/ExecutorScope.hpp>
+
+namespace MNN {
+namespace Express {
+
+typedef std::shared_ptr<Express::Executor> ExecutorRef;
+#if TARGET_OS_IPHONE
+#include <pthread.h>
+static pthread_key_t gKey;
+static std::once_flag gInitFlag;
+#else
+thread_local static std::once_flag gInitFlag;
+thread_local static Scope<ExecutorRef>* g_executor_scope = nullptr;
+#endif
+
+static Scope<ExecutorRef>* _getGlobalScope() {
+    std::call_once(gInitFlag,
+                   [&]() {
+#if TARGET_OS_IPHONE
+        pthread_key_create(&gKey, NULL);
+#else
+        thread_local static Scope<ExecutorRef> initValue;
+        g_executor_scope = &initValue;
+#endif
+    });
+#if TARGET_OS_IPHONE
+    Scope<ExecutorRef>* scope = static_cast<Scope<ExecutorRef>*>(pthread_getspecific(gKey));
+    if (!scope) {
+        scope = new Scope<ExecutorRef>;
+        pthread_setspecific(gKey, static_cast<void*>(scope));
+    }
+    return scope;
+#else
+    return g_executor_scope;
+#endif
+}
+
+ExecutorScope::ExecutorScope(const std::shared_ptr<Executor>& current) {
+    _getGlobalScope()->EnterScope(current);
+}
+
+ExecutorScope::ExecutorScope(const std::string& scope_name,
+                             const std::shared_ptr<Executor>& current) {
+    _getGlobalScope()->EnterScope(scope_name, current);
+}
+
+ExecutorScope::~ExecutorScope() {
+    _getGlobalScope()->ExitScope();
+}
+
+const std::shared_ptr<Executor> ExecutorScope::Current() {
+    auto exe = _getGlobalScope()->Content();
+    if (exe) {
+        return exe;
+    }
+    return Executor::getGlobalExecutor();
+}
+
+}  // namespace Express
+}  // namespace MNN