[debug] Revert debug API removal

src/debug/debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/debug/debug.h"
 
 #include <memory>
 
 #include "src/api.h"
 #include "src/arguments.h"
@@ skipping 20 matching lines @@
 
 #include "include/v8-debug.h"
 
 namespace v8 {
 namespace internal {
 
 Debug::Debug(Isolate* isolate)
     : debug_context_(Handle<Context>()),
       event_listener_(Handle<Object>()),
       event_listener_data_(Handle<Object>()),
+      message_handler_(NULL),
+      command_received_(0),
+      command_queue_(isolate->logger(), kQueueInitialSize),
       is_active_(false),
       is_suppressed_(false),
       live_edit_enabled_(true),  // TODO(yangguo): set to false by default.
       break_disabled_(false),
       break_points_active_(true),
       in_debug_event_listener_(false),
       break_on_exception_(false),
       break_on_uncaught_exception_(false),
       debug_info_list_(NULL),
       feature_tracker_(isolate),
@@ skipping 464 matching lines @@
 
   // Find the break location where execution has stopped.
   BreakLocation location = BreakLocation::FromFrame(debug_info, frame);
 
   // Find actual break points, if any, and trigger debug break event.
   Handle<Object> break_points_hit = CheckBreakPoints(debug_info, &location);
   if (!break_points_hit->IsUndefined(isolate_)) {
     // Clear all current stepping setup.
     ClearStepping();
     // Notify the debug event listeners.
-    OnDebugBreak(break_points_hit);
+    OnDebugBreak(break_points_hit, false);
     return;
   }
 
   // No break point. Check for stepping.
   StepAction step_action = last_step_action();
   Address current_fp = frame->UnpaddedFP();
   Address target_fp = thread_local_.target_fp_;
   Address last_fp = thread_local_.last_fp_;
 
   bool step_break = false;
@@ skipping 23 matching lines @@
     case StepFrame:
       step_break = current_fp != last_fp;
       break;
   }
 
   // Clear all current stepping setup.
   ClearStepping();
 
   if (step_break) {
     // Notify the debug event listeners.
-    OnDebugBreak(isolate_->factory()->undefined_value());
+    OnDebugBreak(isolate_->factory()->undefined_value(), false);
   } else {
     // Re-prepare to continue.
     PrepareStep(step_action);
   }
 }
 
 
 // Find break point objects for this location, if any, and evaluate them.
 // Return an array of break point objects that evaluated true.
 Handle<Object> Debug::CheckBreakPoints(Handle<DebugInfo> debug_info,
@@ skipping 1157 matching lines @@
 
   // Create the event data object.
   Handle<Object> event_data;
   // Bail out and don't call debugger if exception.
   if (!MakeExceptionEvent(
           exception, uncaught, promise).ToHandle(&event_data)) {
     return;
   }
 
   // Process debug event.
-  ProcessDebugEvent(v8::Exception, Handle<JSObject>::cast(event_data));
+  ProcessDebugEvent(v8::Exception, Handle<JSObject>::cast(event_data), false);
   // Return to continue execution from where the exception was thrown.
 }
 
-void Debug::OnDebugBreak(Handle<Object> break_points_hit) {
+void Debug::OnDebugBreak(Handle<Object> break_points_hit, bool auto_continue) {
   // The caller provided for DebugScope.
   AssertDebugContext();
   // Bail out if there is no listener for this event
   if (ignore_events()) return;
 
 #ifdef DEBUG
   PrintBreakLocation();
 #endif  // DEBUG
 
   HandleScope scope(isolate_);
   // Create the event data object.
   Handle<Object> event_data;
   // Bail out and don't call debugger if exception.
   if (!MakeBreakEvent(break_points_hit).ToHandle(&event_data)) return;
 
   // Process debug event.
-  ProcessDebugEvent(v8::Break, Handle<JSObject>::cast(event_data));
+  ProcessDebugEvent(v8::Break, Handle<JSObject>::cast(event_data),
+                    auto_continue);
 }
 
 
 void Debug::OnCompileError(Handle<Script> script) {
   ProcessCompileEvent(v8::CompileError, script);
 }
 
+void Debug::OnBeforeCompile(Handle<Script> script) {
+  ProcessCompileEvent(v8::BeforeCompile, script);
+}
 
 // Handle debugger actions when a new script is compiled.
 void Debug::OnAfterCompile(Handle<Script> script) {
   ProcessCompileEvent(v8::AfterCompile, script);
 }
 
 void Debug::OnAsyncTaskEvent(Handle<String> type, Handle<Object> id,
                              Handle<String> name) {
   DCHECK(id->IsNumber());
   if (in_debug_scope() || ignore_events()) return;
 
   HandleScope scope(isolate_);
   DebugScope debug_scope(this);
   if (debug_scope.failed()) return;
 
   // Create the script collected state object.
   Handle<Object> event_data;
   // Bail out and don't call debugger if exception.
   if (!MakeAsyncTaskEvent(type, id, name).ToHandle(&event_data)) return;
 
   // Process debug event.
-  ProcessDebugEvent(v8::AsyncTaskEvent, Handle<JSObject>::cast(event_data));
+  ProcessDebugEvent(v8::AsyncTaskEvent, Handle<JSObject>::cast(event_data),
+                    true);
 }
 
-void Debug::ProcessDebugEvent(v8::DebugEvent event,
-                              Handle<JSObject> event_data) {
+void Debug::ProcessDebugEvent(v8::DebugEvent event, Handle<JSObject> event_data,
+                              bool auto_continue) {
   HandleScope scope(isolate_);
 
   // Create the execution state.
   Handle<Object> exec_state;
   // Bail out and don't call debugger if exception.
   if (!MakeExecutionState().ToHandle(&exec_state)) return;
 
-  // Notify registered debug event listener.
-  if (!event_listener_.is_null()) {
+  // First notify the message handler if any.
+  if (message_handler_ != NULL) {
+    NotifyMessageHandler(event, Handle<JSObject>::cast(exec_state), event_data,
+                         auto_continue);
+  }
+  // Notify registered debug event listener. This can be either a C or
+  // a JavaScript function. Don't call event listener for v8::Break
+  // here, if it's only a debug command -- they will be processed later.
+  if ((event != v8::Break || !auto_continue) && !event_listener_.is_null()) {
     CallEventCallback(event, exec_state, event_data, NULL);
   }
 }
 
 
 void Debug::CallEventCallback(v8::DebugEvent event,
                               Handle<Object> exec_state,
                               Handle<Object> event_data,
                               v8::Debug::ClientData* client_data) {
   // Prevent other interrupts from triggering, for example API callbacks,
@@ skipping 31 matching lines @@
 
 
 void Debug::ProcessCompileEvent(v8::DebugEvent event, Handle<Script> script) {
   if (ignore_events()) return;
   if (script->type() != i::Script::TYPE_NORMAL &&
       script->type() != i::Script::TYPE_WASM) {
     return;
   }
   SuppressDebug while_processing(this);
 
+  bool in_nested_debug_scope = in_debug_scope();
   HandleScope scope(isolate_);
   DebugScope debug_scope(this);
   if (debug_scope.failed()) return;
 
   if (event == v8::AfterCompile) {
     // If debugging there might be script break points registered for this
     // script. Make sure that these break points are set.
     Handle<Object> argv[] = {Script::GetWrapper(script)};
     if (CallFunction("UpdateScriptBreakPoints", arraysize(argv), argv)
             .is_null()) {
       return;
     }
   }
 
   // Create the compile state object.
   Handle<Object> event_data;
   // Bail out and don't call debugger if exception.
   if (!MakeCompileEvent(script, event).ToHandle(&event_data)) return;
 
-  ProcessDebugEvent(event, Handle<JSObject>::cast(event_data));
+  // Don't call NotifyMessageHandler if already in debug scope to avoid running
+  // nested command loop.
+  if (in_nested_debug_scope) {
+    if (event_listener_.is_null()) return;
+    // Create the execution state.
+    Handle<Object> exec_state;
+    // Bail out and don't call debugger if exception.
+    if (!MakeExecutionState().ToHandle(&exec_state)) return;
+
+    CallEventCallback(event, exec_state, event_data, NULL);
+  } else {
+    // Process debug event.
+    ProcessDebugEvent(event, Handle<JSObject>::cast(event_data), true);
+  }
 }
 
 
 Handle<Context> Debug::GetDebugContext() {
   if (!is_loaded()) return Handle<Context>();
   DebugScope debug_scope(this);
   if (debug_scope.failed()) return Handle<Context>();
   // The global handle may be destroyed soon after.  Return it reboxed.
   return handle(*debug_context(), isolate_);
 }
 
+void Debug::NotifyMessageHandler(v8::DebugEvent event,
+                                 Handle<JSObject> exec_state,
+                                 Handle<JSObject> event_data,
+                                 bool auto_continue) {
+  // Prevent other interrupts from triggering, for example API callbacks,
+  // while dispatching message handler callbacks.
+  PostponeInterruptsScope no_interrupts(isolate_);
+  DCHECK(is_active_);
+  HandleScope scope(isolate_);
+  // Process the individual events.
+  bool sendEventMessage = false;
+  switch (event) {
+    case v8::Break:
+      sendEventMessage = !auto_continue;
+      break;
+    case v8::NewFunction:
+    case v8::BeforeCompile:
+    case v8::CompileError:
+    case v8::AsyncTaskEvent:
+      break;
+    case v8::Exception:
+    case v8::AfterCompile:
+      sendEventMessage = true;
+      break;
+  }
+
+  // The debug command interrupt flag might have been set when the command was
+  // added. It should be enough to clear the flag only once while we are in the
+  // debugger.
+  DCHECK(in_debug_scope());
+  isolate_->stack_guard()->ClearDebugCommand();
+
+  // Notify the debugger that a debug event has occurred unless auto continue is
+  // active in which case no event is send.
+  if (sendEventMessage) {
+    MessageImpl message = MessageImpl::NewEvent(
+        event, auto_continue, Handle<JSObject>::cast(exec_state),
+        Handle<JSObject>::cast(event_data));
+    InvokeMessageHandler(message);
+  }
+
+  // If auto continue don't make the event cause a break, but process messages
+  // in the queue if any. For script collected events don't even process
+  // messages in the queue as the execution state might not be what is expected
+  // by the client.
+  if (auto_continue && !has_commands()) return;
+
+  // DebugCommandProcessor goes here.
+  bool running = auto_continue;
+
+  Handle<Object> cmd_processor_ctor =
+      JSReceiver::GetProperty(isolate_, exec_state, "debugCommandProcessor")
+          .ToHandleChecked();
+  Handle<Object> ctor_args[] = {isolate_->factory()->ToBoolean(running)};
+  Handle<JSReceiver> cmd_processor = Handle<JSReceiver>::cast(
+      Execution::Call(isolate_, cmd_processor_ctor, exec_state, 1, ctor_args)
+          .ToHandleChecked());
+  Handle<JSFunction> process_debug_request = Handle<JSFunction>::cast(
+      JSReceiver::GetProperty(isolate_, cmd_processor, "processDebugRequest")
+          .ToHandleChecked());
+  Handle<Object> is_running =
+      JSReceiver::GetProperty(isolate_, cmd_processor, "isRunning")
+          .ToHandleChecked();
+
+  // Process requests from the debugger.
+  do {
+    // Wait for new command in the queue.
+    command_received_.Wait();
+
+    // Get the command from the queue.
+    CommandMessage command = command_queue_.Get();
+    isolate_->logger()->DebugTag(
+        "Got request from command queue, in interactive loop.");
+    if (!is_active()) {
+      // Delete command text and user data.
+      command.Dispose();
+      return;
+    }
+
+    Vector<const uc16> command_text(
+        const_cast<const uc16*>(command.text().start()),
+        command.text().length());
+    Handle<String> request_text = isolate_->factory()
+                                      ->NewStringFromTwoByte(command_text)
+                                      .ToHandleChecked();
+    Handle<Object> request_args[] = {request_text};
+    Handle<Object> answer_value;
+    Handle<String> answer;
+    MaybeHandle<Object> maybe_exception;
+    MaybeHandle<Object> maybe_result =
+        Execution::TryCall(isolate_, process_debug_request, cmd_processor, 1,
+                           request_args, &maybe_exception);
+
+    if (maybe_result.ToHandle(&answer_value)) {
+      if (answer_value->IsUndefined(isolate_)) {
+        answer = isolate_->factory()->empty_string();
+      } else {
+        answer = Handle<String>::cast(answer_value);
+      }
+
+      // Log the JSON request/response.
+      if (FLAG_trace_debug_json) {
+        PrintF("%s\n", request_text->ToCString().get());
+        PrintF("%s\n", answer->ToCString().get());
+      }
+
+      Handle<Object> is_running_args[] = {answer};
+      maybe_result = Execution::Call(isolate_, is_running, cmd_processor, 1,
+                                     is_running_args);
+      Handle<Object> result;
+      if (!maybe_result.ToHandle(&result)) break;
+      running = result->IsTrue(isolate_);
+    } else {
+      Handle<Object> exception;
+      if (!maybe_exception.ToHandle(&exception)) break;
+      Handle<Object> result;
+      if (!Object::ToString(isolate_, exception).ToHandle(&result)) break;
+      answer = Handle<String>::cast(result);
+    }
+
+    // Return the result.
+    MessageImpl message = MessageImpl::NewResponse(
+        event, running, exec_state, event_data, answer, command.client_data());
+    InvokeMessageHandler(message);
+    command.Dispose();
+
+    // Return from debug event processing if either the VM is put into the
+    // running state (through a continue command) or auto continue is active
+    // and there are no more commands queued.
+  } while (!running || has_commands());
+  command_queue_.Clear();
+}
 
 void Debug::SetEventListener(Handle<Object> callback,
                              Handle<Object> data) {
   GlobalHandles* global_handles = isolate_->global_handles();
 
   // Remove existing entry.
   GlobalHandles::Destroy(event_listener_.location());
   event_listener_ = Handle<Object>();
   GlobalHandles::Destroy(event_listener_data_.location());
   event_listener_data_ = Handle<Object>();
 
   // Set new entry.
   if (!callback->IsUndefined(isolate_) && !callback->IsNull(isolate_)) {
     event_listener_ = global_handles->Create(*callback);
     if (data.is_null()) data = isolate_->factory()->undefined_value();
     event_listener_data_ = global_handles->Create(*data);
   }
 
   UpdateState();
 }
 
+void Debug::SetMessageHandler(v8::Debug::MessageHandler handler) {
+  message_handler_ = handler;
+  UpdateState();
+  if (handler == NULL && in_debug_scope()) {
+    // Send an empty command to the debugger if in a break to make JavaScript
+    // run again if the debugger is closed.
+    EnqueueCommandMessage(Vector<const uint16_t>::empty());
+  }
+}
 
 void Debug::UpdateState() {
-  bool is_active = !event_listener_.is_null();
+  bool is_active = message_handler_ != NULL || !event_listener_.is_null();
   if (is_active || in_debug_scope()) {
     // Note that the debug context could have already been loaded to
     // bootstrap test cases.
     isolate_->compilation_cache()->Disable();
     is_active = Load();
   } else if (is_loaded()) {
     isolate_->compilation_cache()->Enable();
     Unload();
   }
   is_active_ = is_active;
 }
 
+// Calls the registered debug message handler. This callback is part of the
+// public API.
+void Debug::InvokeMessageHandler(MessageImpl message) {
+  if (message_handler_ != NULL) message_handler_(message);
+}
+
+// Puts a command coming from the public API on the queue.  Creates
+// a copy of the command string managed by the debugger.  Up to this
+// point, the command data was managed by the API client.  Called
+// by the API client thread.
+void Debug::EnqueueCommandMessage(Vector<const uint16_t> command,
+                                  v8::Debug::ClientData* client_data) {
+  // Need to cast away const.
+  CommandMessage message = CommandMessage::New(
+      Vector<uint16_t>(const_cast<uint16_t*>(command.start()),
+                       command.length()),
+      client_data);
+  isolate_->logger()->DebugTag("Put command on command_queue.");
+  command_queue_.Put(message);
+  command_received_.Signal();
+
+  // Set the debug command break flag to have the command processed.
+  if (!in_debug_scope()) isolate_->stack_guard()->RequestDebugCommand();
+}
 
 MaybeHandle<Object> Debug::Call(Handle<Object> fun, Handle<Object> data) {
   DebugScope debug_scope(this);
   if (debug_scope.failed()) return isolate_->factory()->undefined_value();
 
   // Create the execution state.
   Handle<Object> exec_state;
   if (!MakeExecutionState().ToHandle(&exec_state)) {
     return isolate_->factory()->undefined_value();
   }
@@ skipping 27 matching lines @@
       if (!JSFunction::cast(fun)->shared()->IsSubjectToDebugging()) return;
       JSGlobalObject* global =
           JSFunction::cast(fun)->context()->global_object();
       // Don't stop in debugger functions.
       if (IsDebugGlobal(global)) return;
       // Don't stop if the break location is muted.
       if (IsMutedAtCurrentLocation(it.frame())) return;
     }
   }
 
+  // Collect the break state before clearing the flags.
+  bool debug_command_only = isolate_->stack_guard()->CheckDebugCommand() &&
+                            !isolate_->stack_guard()->CheckDebugBreak();
+
   isolate_->stack_guard()->ClearDebugBreak();
 
   // Clear stepping to avoid duplicate breaks.
   ClearStepping();
 
+  ProcessDebugMessages(debug_command_only);
+}
+
+void Debug::ProcessDebugMessages(bool debug_command_only) {
+  isolate_->stack_guard()->ClearDebugCommand();
+
+  StackLimitCheck check(isolate_);
+  if (check.HasOverflowed()) return;
+
   HandleScope scope(isolate_);
   DebugScope debug_scope(this);
   if (debug_scope.failed()) return;
 
-  // Notify the debug event listeners.
-  OnDebugBreak(isolate_->factory()->undefined_value());
+  // Notify the debug event listeners. Indicate auto continue if the break was
+  // a debug command break.
+  OnDebugBreak(isolate_->factory()->undefined_value(), debug_command_only);
 }
 
 #ifdef DEBUG
 void Debug::PrintBreakLocation() {
   if (!FLAG_print_break_location) return;
   HandleScope scope(isolate_);
   JavaScriptFrameIterator iterator(isolate_);
   if (iterator.done()) return;
   JavaScriptFrame* frame = iterator.frame();
   FrameSummary summary = FrameSummary::GetFirst(frame);
@@ skipping 63 matching lines @@
 }
 
 
 DebugScope::~DebugScope() {
   if (!failed_ && prev_ == NULL) {
     // Clear mirror cache when leaving the debugger. Skip this if there is a
     // pending exception as clearing the mirror cache calls back into
     // JavaScript. This can happen if the v8::Debug::Call is used in which
     // case the exception should end up in the calling code.
     if (!isolate()->has_pending_exception()) debug_->ClearMirrorCache();
+
+    // If there are commands in the queue when leaving the debugger request
+    // that these commands are processed.
+    if (debug_->has_commands()) isolate()->stack_guard()->RequestDebugCommand();
   }
 
   // Leaving this debugger entry.
   base::NoBarrier_Store(&debug_->thread_local_.current_debug_scope_,
                         reinterpret_cast<base::AtomicWord>(prev_));
 
   // Restore to the previous break state.
   debug_->thread_local_.break_frame_id_ = break_frame_id_;
   debug_->thread_local_.break_id_ = break_id_;
   debug_->thread_local_.return_value_ = return_value_;
 
   debug_->UpdateState();
 }
 
+MessageImpl MessageImpl::NewEvent(DebugEvent event, bool running,
+                                  Handle<JSObject> exec_state,
+                                  Handle<JSObject> event_data) {
+  MessageImpl message(true, event, running, exec_state, event_data,
+                      Handle<String>(), NULL);
+  return message;
+}
+
+MessageImpl MessageImpl::NewResponse(DebugEvent event, bool running,
+                                     Handle<JSObject> exec_state,
+                                     Handle<JSObject> event_data,
+                                     Handle<String> response_json,
+                                     v8::Debug::ClientData* client_data) {
+  MessageImpl message(false, event, running, exec_state, event_data,
+                      response_json, client_data);
+  return message;
+}
+
+MessageImpl::MessageImpl(bool is_event, DebugEvent event, bool running,
+                         Handle<JSObject> exec_state,
+                         Handle<JSObject> event_data,
+                         Handle<String> response_json,
+                         v8::Debug::ClientData* client_data)
+    : is_event_(is_event),
+      event_(event),
+      running_(running),
+      exec_state_(exec_state),
+      event_data_(event_data),
+      response_json_(response_json),
+      client_data_(client_data) {}
+
+bool MessageImpl::IsEvent() const { return is_event_; }
+
+bool MessageImpl::IsResponse() const { return !is_event_; }
+
+DebugEvent MessageImpl::GetEvent() const { return event_; }
+
+bool MessageImpl::WillStartRunning() const { return running_; }
+
+v8::Local<v8::Object> MessageImpl::GetExecutionState() const {
+  return v8::Utils::ToLocal(exec_state_);
+}
+
+v8::Isolate* MessageImpl::GetIsolate() const {
+  return reinterpret_cast<v8::Isolate*>(exec_state_->GetIsolate());
+}
+
+v8::Local<v8::Object> MessageImpl::GetEventData() const {
+  return v8::Utils::ToLocal(event_data_);
+}
+
+v8::Local<v8::String> MessageImpl::GetJSON() const {
+  Isolate* isolate = event_data_->GetIsolate();
+  v8::EscapableHandleScope scope(reinterpret_cast<v8::Isolate*>(isolate));
+
+  if (IsEvent()) {
+    // Call toJSONProtocol on the debug event object.
+    Handle<Object> fun =
+        JSReceiver::GetProperty(isolate, event_data_, "toJSONProtocol")
+            .ToHandleChecked();
+    if (!fun->IsJSFunction()) {
+      return v8::Local<v8::String>();
+    }
+
+    MaybeHandle<Object> maybe_json =
+        Execution::TryCall(isolate, fun, event_data_, 0, NULL);
+    Handle<Object> json;
+    if (!maybe_json.ToHandle(&json) || !json->IsString()) {
+      return v8::Local<v8::String>();
+    }
+    return scope.Escape(v8::Utils::ToLocal(Handle<String>::cast(json)));
+  } else {
+    return v8::Utils::ToLocal(response_json_);
+  }
+}
+
+namespace {
+v8::Local<v8::Context> GetDebugEventContext(Isolate* isolate) {
+  Handle<Context> context = isolate->debug()->debugger_entry()->GetContext();
+  // Isolate::context() may have been NULL when "script collected" event
+  // occured.
+  if (context.is_null()) return v8::Local<v8::Context>();
+  Handle<Context> native_context(context->native_context());
+  return v8::Utils::ToLocal(native_context);
+}
+}  // anonymous namespace
+
+v8::Local<v8::Context> MessageImpl::GetEventContext() const {
+  Isolate* isolate = event_data_->GetIsolate();
+  v8::Local<v8::Context> context = GetDebugEventContext(isolate);
+  // Isolate::context() may be NULL when "script collected" event occurs.
+  DCHECK(!context.IsEmpty());
+  return context;
+}
+
+v8::Debug::ClientData* MessageImpl::GetClientData() const {
+  return client_data_;
+}
 
 EventDetailsImpl::EventDetailsImpl(DebugEvent event,
                                    Handle<JSObject> exec_state,
                                    Handle<JSObject> event_data,
                                    Handle<Object> callback_data,
                                    v8::Debug::ClientData* client_data)
     : event_(event),
       exec_state_(exec_state),
       event_data_(event_data),
       callback_data_(callback_data),
       client_data_(client_data) {}
 
 
 DebugEvent EventDetailsImpl::GetEvent() const {
   return event_;
 }
 
 
 v8::Local<v8::Object> EventDetailsImpl::GetExecutionState() const {
   return v8::Utils::ToLocal(exec_state_);
 }
 
 
 v8::Local<v8::Object> EventDetailsImpl::GetEventData() const {
   return v8::Utils::ToLocal(event_data_);
 }
 
 
 v8::Local<v8::Context> EventDetailsImpl::GetEventContext() const {
-  Handle<Context> context =
-      exec_state_->GetIsolate()->debug()->debugger_entry()->GetContext();
-  if (context.is_null()) return v8::Local<v8::Context>();
-  Handle<Context> native_context(context->native_context());
-  return v8::Utils::ToLocal(native_context);
+  return GetDebugEventContext(exec_state_->GetIsolate());
 }
 
 
 v8::Local<v8::Value> EventDetailsImpl::GetCallbackData() const {
   return v8::Utils::ToLocal(callback_data_);
 }
 
 
 v8::Debug::ClientData* EventDetailsImpl::GetClientData() const {
   return client_data_;
 }
 
 v8::Isolate* EventDetailsImpl::GetIsolate() const {
   return reinterpret_cast<v8::Isolate*>(exec_state_->GetIsolate());
 }
 
+CommandMessage::CommandMessage()
+    : text_(Vector<uint16_t>::empty()), client_data_(NULL) {}
+
+CommandMessage::CommandMessage(const Vector<uint16_t>& text,
+                               v8::Debug::ClientData* data)
+    : text_(text), client_data_(data) {}
+
+void CommandMessage::Dispose() {
+  text_.Dispose();
+  delete client_data_;
+  client_data_ = NULL;
+}
+
+CommandMessage CommandMessage::New(const Vector<uint16_t>& command,
+                                   v8::Debug::ClientData* data) {
+  return CommandMessage(command.Clone(), data);
+}
+
+CommandMessageQueue::CommandMessageQueue(int size)
+    : start_(0), end_(0), size_(size) {
+  messages_ = NewArray<CommandMessage>(size);
+}
+
+CommandMessageQueue::~CommandMessageQueue() {
+  while (!IsEmpty()) Get().Dispose();
+  DeleteArray(messages_);
+}
+
+CommandMessage CommandMessageQueue::Get() {
+  DCHECK(!IsEmpty());
+  int result = start_;
+  start_ = (start_ + 1) % size_;
+  return messages_[result];
+}
+
+void CommandMessageQueue::Put(const CommandMessage& message) {
+  if ((end_ + 1) % size_ == start_) {
+    Expand();
+  }
+  messages_[end_] = message;
+  end_ = (end_ + 1) % size_;
+}
+
+void CommandMessageQueue::Expand() {
+  CommandMessageQueue new_queue(size_ * 2);
+  while (!IsEmpty()) {
+    new_queue.Put(Get());
+  }
+  CommandMessage* array_to_free = messages_;
+  *this = new_queue;
+  new_queue.messages_ = array_to_free;
+  // Make the new_queue empty so that it doesn't call Dispose on any messages.
+  new_queue.start_ = new_queue.end_;
+  // Automatic destructor called on new_queue, freeing array_to_free.
+}
+
+LockingCommandMessageQueue::LockingCommandMessageQueue(Logger* logger, int size)
+    : logger_(logger), queue_(size) {}
+
+bool LockingCommandMessageQueue::IsEmpty() const {
+  base::LockGuard<base::Mutex> lock_guard(&mutex_);
+  return queue_.IsEmpty();
+}
+
+CommandMessage LockingCommandMessageQueue::Get() {
+  base::LockGuard<base::Mutex> lock_guard(&mutex_);
+  CommandMessage result = queue_.Get();
+  logger_->DebugEvent("Get", result.text());
+  return result;
+}
+
+void LockingCommandMessageQueue::Put(const CommandMessage& message) {
+  base::LockGuard<base::Mutex> lock_guard(&mutex_);
+  queue_.Put(message);
+  logger_->DebugEvent("Put", message.text());
+}
+
+void LockingCommandMessageQueue::Clear() {
+  base::LockGuard<base::Mutex> lock_guard(&mutex_);
+  queue_.Clear();
+}
+
 }  // namespace internal
 }  // namespace v8