Copy fbjni library from react-native

lib/fb/jni/Environment.cpp

@@ -0,0 +1,132 @@
+/*
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#include <pthread.h>
+#include <fb/log.h>
+#include <fb/StaticInitialized.h>
+#include <fb/ThreadLocal.h>
+#include <fb/Environment.h>
+#include <fb/fbjni/CoreClasses.h>
+#include <fb/fbjni/NativeRunnable.h>
+
+#include <functional>
+
+namespace facebook {
+namespace jni {
+
+namespace {
+StaticInitialized<ThreadLocal<JNIEnv>> g_env;
+JavaVM* g_vm = nullptr;
+
+struct JThreadScopeSupport : JavaClass<JThreadScopeSupport> {
+  static auto constexpr kJavaDescriptor = "Lcom/facebook/jni/ThreadScopeSupport;";
+
+  // These reinterpret_casts are a totally dangerous pattern. Don't use them. Use HybridData instead.
+  static void runStdFunction(std::function<void()>&& func) {
+    static auto method = javaClassStatic()->getStaticMethod<void(jlong)>("runStdFunction");
+    method(javaClassStatic(), reinterpret_cast<jlong>(&func));
+  }
+
+  static void runStdFunctionImpl(alias_ref<JClass>, jlong ptr) {
+    (*reinterpret_cast<std::function<void()>*>(ptr))();
+  }
+
+  static void OnLoad() {
+    // We need the javaClassStatic so that the class lookup is cached and that
+    // runStdFunction can be called from a ThreadScope-attached thread.
+    javaClassStatic()->registerNatives({
+        makeNativeMethod("runStdFunctionImpl", runStdFunctionImpl),
+      });
+  }
+};
+}
+
+/* static */
+JNIEnv* Environment::current() {
+  JNIEnv* env = g_env->get();
+  if ((env == nullptr) && (g_vm != nullptr)) {
+    if (g_vm->GetEnv((void**) &env, JNI_VERSION_1_6) != JNI_OK) {
+      FBLOGE("Error retrieving JNI Environment, thread is probably not attached to JVM");
+      // TODO(cjhopman): This should throw an exception.
+      env = nullptr;
+    } else {
+      g_env->reset(env);
+    }
+  }
+  return env;
+}
+
+/* static */
+void Environment::detachCurrentThread() {
+  auto env = g_env->get();
+  if (env) {
+    FBASSERT(g_vm);
+    g_vm->DetachCurrentThread();
+    g_env->reset();
+  }
+}
+
+struct EnvironmentInitializer {
+  EnvironmentInitializer(JavaVM* vm) {
+      FBASSERT(!g_vm);
+      FBASSERT(vm);
+      g_vm = vm;
+      g_env.initialize([] (void*) {});
+  }
+};
+
+/* static */
+void Environment::initialize(JavaVM* vm) {
+  static EnvironmentInitializer init(vm);
+}
+
+/* static */
+JNIEnv* Environment::ensureCurrentThreadIsAttached() {
+  auto env = g_env->get();
+  if (!env) {
+    FBASSERT(g_vm);
+    g_vm->AttachCurrentThread(&env, nullptr);
+    g_env->reset(env);
+  }
+  return env;
+}
+
+ThreadScope::ThreadScope()
+    : attachedWithThisScope_(false) {
+  JNIEnv* env = nullptr;
+  if (g_vm->GetEnv((void**) &env, JNI_VERSION_1_6) != JNI_EDETACHED) {
+    return;
+  }
+  env = facebook::jni::Environment::ensureCurrentThreadIsAttached();
+  FBASSERT(env);
+  attachedWithThisScope_ = true;
+}
+
+ThreadScope::~ThreadScope() {
+  if (attachedWithThisScope_) {
+    Environment::detachCurrentThread();
+  }
+}
+
+/* static */
+void ThreadScope::OnLoad() {
+  // These classes are required for ScopeWithClassLoader. Ensure they are looked up when loading.
+  JThreadScopeSupport::OnLoad();
+}
+
+/* static */
+void ThreadScope::WithClassLoader(std::function<void()>&& runnable) {
+  // TODO(cjhopman): If the classloader is already available in this scope, we
+  // shouldn't have to jump through java.
+  ThreadScope ts;
+  JThreadScopeSupport::runStdFunction(std::move(runnable));
+}
+
+} }
+