src/cobalt/script/global_environment.h

// Copyright 2014 The Cobalt Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef COBALT_SCRIPT_GLOBAL_ENVIRONMENT_H_
#define COBALT_SCRIPT_GLOBAL_ENVIRONMENT_H_

#include <string>
#include <vector>

#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "base/optional.h"
#include "cobalt/script/error_report.h"
#include "cobalt/script/script_value.h"
#include "cobalt/script/script_value_factory.h"
#include "cobalt/script/stack_frame.h"
#include "cobalt/script/value_handle.h"
#include "cobalt/script/wrappable.h"

namespace cobalt {
namespace script {

class EnvironmentSettings;
class JavaScriptEngine;
class SourceCode;

// Manages a handle to a JavaScript engine's global object.
class GlobalEnvironment : public base::RefCounted<GlobalEnvironment>,
                          public base::SupportsWeakPtr<GlobalEnvironment> {
 public:
  typedef base::Callback<bool(const ErrorReport& error_report)>
      ReportErrorCallback;

  // Create a new global object with bindings as defined for the definition of
  // the GlobalInterface type. The IDL for this interface must have the
  // PrimaryGlobal or Global extended attribute.
  //
  // Specializations of this template function are implemented in the
  // generated bindings code for each JavaScript engine.
  template <typename GlobalInterface>
  void CreateGlobalObject(
      const scoped_refptr<GlobalInterface>& global_interface,
      EnvironmentSettings* environment_settings);

  // Create a new global object with no bindings.
  virtual void CreateGlobalObject() = 0;

  // Evaluate the JavaScript source code. Returns true on success,
  // false if there is an exception.
  // If out_result is non-NULL, it will be set to hold the result of the script
  // evaluation if the script succeeds, or an exception message if it fails.
  virtual bool EvaluateScript(const scoped_refptr<SourceCode>& script_utf8,
                              std::string* out_result_utf8) = 0;

  // Evaluate the JavaScript source code. Returns true on success,
  // false if there is an exception.
  // Set |out_value_handle| to be a reference to the result of the evaluation
  // of the script that is owned by |owner|.
  virtual bool EvaluateScript(
      const scoped_refptr<SourceCode>& script_utf8,
      const scoped_refptr<Wrappable>& owning_object,
      base::Optional<ValueHandleHolder::Reference>* out_value_handle) = 0;

  // Returns the stack trace as a vector of individual frames.
  // Set |max_frames| to 0 to retrieve all available frames. Otherwise
  // return at most |max_frames|.
  virtual std::vector<StackFrame> GetStackTrace(int max_frames) = 0;
  // Our style guide bans default arguments for virtual functions, however we
  // ended up taking a dependency on them in our bindings code before it was
  // caught. Instead, provide a non-virtual overload that wraps virtual
  // |GetStackTrace(int)| to make everyone happy.
  std::vector<StackFrame> GetStackTrace() { return GetStackTrace(0); }

  // Register |traceable| as a member of the root set, i.e., an a priori
  // reachable node.  In a manner similar to |PreventGarbageCollection|,
  // multiple calls are supported.
  virtual void AddRoot(Traceable* traceable) = 0;

  // Undo a registration from |AddRoot|.
  virtual void RemoveRoot(Traceable* traceable) = 0;

  // Disable eval() and specify the message to report in the exception.
  virtual void DisableEval(const std::string& message) = 0;

  // Allow eval().
  virtual void EnableEval() = 0;

  // Disable just-in-time compilation of JavaScript source code to native
  // code.  Calling this is a no-op if JIT was not enabled in the first place,
  // or if the engine does not support disabling JIT.
  virtual void DisableJit() = 0;

  // Set a callback that will be fired whenever eval() or a Function()
  // constructor is used.
  virtual void SetReportEvalCallback(const base::Closure& report_eval) = 0;

  // Set a callback that will be fired whenever a JavaScript error occurs.
  virtual void SetReportErrorCallback(
      const ReportErrorCallback& report_error) = 0;

  // Dynamically bind a cpp object to the JavaScript global object with the
  // supplied identifier.
  // This method is useful for testing and debug purposes, as well as for
  // dynamically injecting an API into a JavaScript environment.
  //
  // This static function must be implemented by the JavaScriptEngine
  // implementation
  virtual void Bind(const std::string& identifier,
                    const scoped_refptr<Wrappable>& impl) = 0;

  // Get the ScriptValueFactory for this global environment. The
  // GlobalEnvironment instance retains ownership of the ScriptValueFactory and
  // should live longer than any ScriptValueFactory pointer.
  virtual ScriptValueFactory* script_value_factory() = 0;

  class ScopedPreventGarbageCollection {
   public:
    ScopedPreventGarbageCollection(GlobalEnvironment* global_environment,
                                   Wrappable* wrappable)
        : global_environment(global_environment->AsWeakPtr()), wrappable(wrappable) {
      global_environment->PreventGarbageCollection(
          base::WrapRefCounted(wrappable));
    }

    ~ScopedPreventGarbageCollection() {
      if (global_environment) {
        global_environment->AllowGarbageCollection(wrappable);
      }
    }

   private:
    base::WeakPtr<GlobalEnvironment> global_environment;
    Wrappable* wrappable;
  };

 protected:
  // Prevent this wrappable's associated JavaScript wrapper object from being
  // garbage collected. |AllowGarbageCollection| must be called some time
  // afterwards, or else both the JavaScript wrapper object and Wrappable will
  // leak. Note that multiple calls to |PreventGarbageCollection| *are*
  // counted, in that calling (e.g.) prevent, prevent, allow on |wrappable|,
  // implies that |wrappable| is still garbage collection prevented.
  virtual void PreventGarbageCollection(
      const scoped_refptr<Wrappable>& wrappable) = 0;

  // Allow this wrappable's associated JavaScript wrapper object to be garbage
  // collected.
  virtual void AllowGarbageCollection(Wrappable* wrappable) = 0;

  virtual ~GlobalEnvironment() {}
  friend class base::RefCounted<GlobalEnvironment>;
};

}  // namespace script
}  // namespace cobalt

#endif  // COBALT_SCRIPT_GLOBAL_ENVIRONMENT_H_