react-native/ReactCommon/cxxreact/NativeToJsBridge.h

// Copyright 2004-present Facebook. All Rights Reserved.

#pragma once

#include <atomic>
#include <functional>
#include <map>
#include <vector>

#include <cxxreact/Executor.h>
#include <cxxreact/ExecutorToken.h>
#include <cxxreact/JSCExecutor.h>
#include <cxxreact/JSModulesUnbundle.h>
#include <cxxreact/MessageQueueThread.h>
#include <cxxreact/MethodCall.h>
#include <cxxreact/NativeModule.h>
#include <folly/dynamic.h>
#include <jschelpers/Value.h>

namespace folly {

struct dynamic;

}

namespace facebook {
namespace react {

struct InstanceCallback;
class ModuleRegistry;

class ExecutorRegistration {
public:
  ExecutorRegistration(
      std::unique_ptr<JSExecutor> executor,
      std::shared_ptr<MessageQueueThread> executorMessageQueueThread) :
    executor_(std::move(executor)),
    messageQueueThread_(executorMessageQueueThread) {}

  std::unique_ptr<JSExecutor> executor_;
  std::shared_ptr<MessageQueueThread> messageQueueThread_;
};

class JsToNativeBridge;

// This class manages calls from native code to JS.  It also manages
// executors and their threads.  All functions here can be called from
// any thread.
//
// Except for loadApplicationScriptSync(), all void methods will queue
// work to run on the jsQueue passed to the ctor, and return
// immediately.
class NativeToJsBridge {
public:
  friend class JsToNativeBridge;

  /**
   * This must be called on the main JS thread.
   */
  NativeToJsBridge(
      JSExecutorFactory* jsExecutorFactory,
      std::shared_ptr<ModuleRegistry> registry,
      std::shared_ptr<MessageQueueThread> jsQueue,
      std::shared_ptr<InstanceCallback> callback);
  virtual ~NativeToJsBridge();

  /**
   * Executes a function with the module ID and method ID and any additional
   * arguments in JS.
   */
  void callFunction(
    ExecutorToken executorToken,
    std::string&& module,
    std::string&& method,
    folly::dynamic&& args);

  /**
   * Invokes a callback with the cbID, and optional additional arguments in JS.
   */
  void invokeCallback(ExecutorToken executorToken, double callbackId, folly::dynamic&& args);

  /**
   * Executes a JS method on the given executor synchronously, returning its
   * return value.  JSException will be thrown if JS throws an exception;
   * another standard exception may be thrown for C++ bridge failures, or if
   * the executor is not capable of synchronous calls.
   *
   * This method is experimental, and may be modified or removed.
   *
   * loadApplicationScriptSync() must be called and finished executing
   * before callFunctionSync().
   */
  template <typename T>
  Value callFunctionSync(const std::string& module, const std::string& method, T&& args) {
    if (*m_destroyed) {
      throw std::logic_error(
        folly::to<std::string>("Synchronous call to ", module, ".", method,
                               " after bridge is destroyed"));
    }

    JSCExecutor *jscExecutor = dynamic_cast<JSCExecutor*>(m_mainExecutor);
    if (!jscExecutor) {
      throw std::invalid_argument(
        folly::to<std::string>("Executor type ", typeid(*m_mainExecutor).name(),
                               " does not support synchronous calls"));
    }

    return jscExecutor->callFunctionSync(module, method, std::forward<T>(args));
  }

  /**
   * Starts the JS application.  If unbundle is non-null, then it is
   * used to fetch JavaScript modules as individual scripts.
   * Otherwise, the script is assumed to include all the modules.
   */
  void loadApplication(
    std::unique_ptr<JSModulesUnbundle> unbundle,
    std::unique_ptr<const JSBigString> startupCode,
    std::string sourceURL);
  void loadApplicationSync(
    std::unique_ptr<JSModulesUnbundle> unbundle,
    std::unique_ptr<const JSBigString> startupCode,
    std::string sourceURL);

  void setGlobalVariable(std::string propName, std::unique_ptr<const JSBigString> jsonValue);
  void* getJavaScriptContext();
  bool supportsProfiling();
  void startProfiler(const std::string& title);
  void stopProfiler(const std::string& title, const std::string& filename);
  void handleMemoryPressureUiHidden();
  void handleMemoryPressureModerate();
  void handleMemoryPressureCritical();

  /**
   * Returns the ExecutorToken corresponding to the main JSExecutor.
   */
  ExecutorToken getMainExecutorToken() const;

  /**
   * Synchronously tears down the bridge and the main executor.
   */
  void destroy();
private:
  /**
   * Registers the given JSExecutor which runs on the given MessageQueueThread
   * with the NativeToJsBridge. Part of this registration is transfering
   * ownership of this JSExecutor to the NativeToJsBridge for the duration of
   * the registration.
   *
   * Returns a ExecutorToken which can be used to refer to this JSExecutor
   * in the NativeToJsBridge.
   */
  ExecutorToken registerExecutor(
      ExecutorToken token,
      std::unique_ptr<JSExecutor> executor,
      std::shared_ptr<MessageQueueThread> executorMessageQueueThread);

  /**
   * Unregisters a JSExecutor that was previously registered with this NativeToJsBridge
   * using registerExecutor.
   */
  std::unique_ptr<JSExecutor> unregisterExecutor(JSExecutor& executorToken);

  void runOnExecutorQueue(ExecutorToken token, std::function<void(JSExecutor*)> task);

  // This is used to avoid a race condition where a proxyCallback gets queued
  // after ~NativeToJsBridge(), on the same thread. In that case, the callback
  // will try to run the task on m_callback which will have been destroyed
  // within ~NativeToJsBridge(), thus causing a SIGSEGV.
  std::shared_ptr<bool> m_destroyed;
  JSExecutor* m_mainExecutor;
  ExecutorToken m_mainExecutorToken;
  std::shared_ptr<JsToNativeBridge> m_delegate;
  std::unordered_map<JSExecutor*, ExecutorToken> m_executorTokenMap;
  std::unordered_map<ExecutorToken, ExecutorRegistration> m_executorMap;
  std::mutex m_registrationMutex;
  #ifdef WITH_FBSYSTRACE
  std::atomic_uint_least32_t m_systraceCookie = ATOMIC_VAR_INIT();
  #endif

  MessageQueueThread* getMessageQueueThread(const ExecutorToken& executorToken);
  JSExecutor* getExecutor(const ExecutorToken& executorToken);
  ExecutorToken getTokenForExecutor(JSExecutor& executor);
};

} }