First step towards support for being able to interrupt a running Dart Isolate

runtime/bin/dbg_message.h

Index: runtime/bin/dbg_message.h
===================================================================
--- runtime/bin/dbg_message.h	(revision 0)
+++ runtime/bin/dbg_message.h	(revision 0)
@@ -0,0 +1,195 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef BIN_DBG_MESSAGE_H_
+#define BIN_DBG_MESSAGE_H_
+
+#include "bin/builtin.h"
+#include "bin/utils.h"
+
+#include "include/dart_debugger_api.h"
+
+#include "platform/globals.h"
+#include "platform/json.h"
+#include "platform/thread.h"
+
+
+// TODO(hausner): Need better error handling.
+#define ASSERT_NOT_ERROR(handle)          \
+  ASSERT(!Dart_IsError(handle))
+
+#define RETURN_IF_ERROR(handle)           \
+  if (Dart_IsError(handle)) {             \
+    return Dart_GetError(handle);         \
+  }
+
+
+// Class to parse a JSON debug command message.
+class MessageParser {
+ public:
+  MessageParser(const char* buf, int buf_length)
+      : buf_(buf), buf_length_(buf_length) {
+  }
+  ~MessageParser() { }
+
+  // Accessors.
+  const char* buf() const { return buf_; }
+
+  bool IsValidMessage() const;
+  int MessageId() const;
+
+  const char* Params() const;
+  intptr_t GetIntParam(const char* name) const;
+  intptr_t GetOptIntParam(const char* name, intptr_t default_val) const;
+
+  // GetStringParam mallocs the buffer that it returns. Caller must free.
+  char* GetStringParam(const char* name) const;
+
+ private:
+  const char* buf_;
+  int buf_length_;
+
+  DISALLOW_COPY_AND_ASSIGN(MessageParser);
+};
+
+
+// Class which represents a debug command message and handles it.
+class DbgMessage {
+ public:
+  DbgMessage(DbgMessage* next, int32_t cmd_idx, const char* start,
+             const char* end, int debug_fd)
+      : next_(next), cmd_idx_(cmd_idx),
+        buffer_(NULL), buffer_len_(end - start),
+        debug_fd_(debug_fd), request_resume_(false) {
+    buffer_ = reinterpret_cast<char*>(malloc(buffer_len_));
+    ASSERT(buffer_ != NULL);
+    memmove(buffer_, start, buffer_len_);
+  }
+  ~DbgMessage() {
+    next_ = NULL;
+    free(buffer_);
+  }
+
+  // Accessors.
+  DbgMessage* next() const { return next_; }
+  char* buffer() const { return buffer_; }
+  int32_t buffer_len() const { return buffer_len_; }
+  int debug_fd() const { return debug_fd_; }
+  bool request_resume() const { return request_resume_; }

[hausner, 2012/09/28 17:03:01]

It's a matter of taste, but I would eliminate the baroqueness of a setter for
request_resume. The field is set by its own class only.

I also don't like that request_resume() is a simple getter, since the value
returned is only correct once the message has been handled. How about returning
this value as a result from HandleMessage()?

[siva, 2012/09/28 23:32:29]

Done.

+  void set_request_resume(bool value) { request_resume_ = value; }
+
+  // Handle debugger command message.
+  void HandleMessage();
+
+  // Send reply after successful handling of command.
+  void SendReply(dart::TextBuffer* msg);
+
+  // Reply error returned by the command handler.
+  void SendErrorReply(int msg_id, const char* err_msg);
+
+  // Handlers for specific commands, they are static because these
+  // functions are populated as function pointers into a dispatch table.
+  static void HandleResumeCmd(DbgMessage* msg);
+  static void HandleStepIntoCmd(DbgMessage* msg);
+  static void HandleStepOverCmd(DbgMessage* msg);
+  static void HandleStepOutCmd(DbgMessage* msg);
+  static void HandleGetLibrariesCmd(DbgMessage* msg);
+  static void HandleGetClassPropsCmd(DbgMessage* msg);
+  static void HandleGetLibPropsCmd(DbgMessage* msg);
+  static void HandleSetLibPropsCmd(DbgMessage* msg);
+  static void HandleGetGlobalsCmd(DbgMessage* msg);
+  static void HandleGetObjPropsCmd(DbgMessage* msg);
+  static void HandleGetListCmd(DbgMessage* msg);
+  static void HandleGetScriptURLsCmd(DbgMessage* msg);
+  static void HandleGetSourceCmd(DbgMessage* msg);
+  static void HandleGetStackTraceCmd(DbgMessage* msg);
+  static void HandlePauseOnExcCmd(DbgMessage* msg);
+  static void HandleSetBpCmd(DbgMessage* msg);
+  static void HandleRemBpCmd(DbgMessage* msg);
+
+ private:
+  DbgMessage* next_;  // Next message in the queue.
+  int32_t cmd_idx_;  // Isolate specific debugger command index.
+  char* buffer_;  // Debugger command message.
+  int32_t buffer_len_;  // Length of the debugger command message.
+  int debug_fd_;  // Debugger connection on which replies are to be sent.
+  bool request_resume_;  // True if command requests execution to resume.
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(DbgMessage);
+};
+
+
+// Class which represents a queue of debug command messages sent to an isolate.
+class DbgMessageQueue {
+ public:
+  static const int32_t kInvalidCommand = -1;
+
+  DbgMessageQueue() : is_running_(true),
+                      is_interrupted_(false),
+                      msglist_(NULL),
+                      queued_output_messages_(64) {
+  }
+  ~DbgMessageQueue() {
+    // Cleanup the message queue
+  }
+
+  // Add specified debug command message to the queue.
+  void AddMessage(int32_t cmd_idx,
+                  const char* start,
+                  const char* end,
+                  int debug_fd);
+
+  // Handle all debug command messages in the queue.
+  void HandleMessages();
+
+  // Queue output messages, these are sent out when we hit an event.
+  void QueueOutputMsg(dart::TextBuffer* msg);
+
+  // Send all queued messages over to the debugger.
+  void SendQueuedMsgs();
+
+  // Send breakpoint event message over to the debugger.
+  void SendBreakpointEvent(Dart_StackTrace trace);
+
+  // Send Exception event message over to the debugger.
+  void SendExceptionEvent(Dart_Handle exception, Dart_StackTrace trace);
+
+  // Initialize the message queue processing by setting up the appropriate
+  // handlers.
+  static void Initialize();
+
+  // Parses the input message and returns the command index if the message
+  // contains a valid isolate specific command.
+  // It returns kInvalidCommand otherwise.
+  static int32_t LookupIsolateCommand(const char* buf, int32_t buflen);
+
+  // Get Debugger Message Queue corresponding to the Isolate.
+  static DbgMessageQueue* GetIsolateMessageQueue(Dart_Isolate isolate);
+
+  // Generic handlers for breakpoints, exceptions and delayed breakpoint
+  // resolution.
+  static void BptResolvedHandler(intptr_t bp_id,
+                                 Dart_Handle url,
+                                 intptr_t line_number);
+  static void BreakpointHandler(Dart_Breakpoint bpt, Dart_StackTrace trace);
+  static void ExceptionThrownHandler(Dart_Handle exception,
+                                     Dart_StackTrace stack_trace);
+
+ private:
+  bool is_running_;  // True if isolate is running and not in the debugger loop.
+  bool is_interrupted_;  // True if interrupt command is pending.
+
+  DbgMessage* msglist_;  // List of debugger messages received.
+
+  // Text buffer that accumulates messages to be output.
+  dart::TextBuffer queued_output_messages_;
+
+  // The waits on this condition variable when it needs to process
+  // debug messages.
+  dart::Monitor msg_queue_lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(DbgMessageQueue);
+};
+
+#endif  // BIN_DBG_MESSAGE_H_