Introduce internal Log class that handles writing log messages, enable logging to memory buffer.

src/log.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 85 matching lines @@
   VMState* previous_;
 #else
  public:
   explicit VMState(StateTag state) {}
 #endif
 };
 
 
 class Logger {
  public:
-  // Opens the file for logging if the right flags are set.
+  // Acquires resources for logging if the right flags are set.
   static bool Setup();
 
-  // Closes file opened in Setup.
+  // Frees resources acquired in Setup.
   static void TearDown();
 
   // Enable the computation of a sliding window of states.
   static void EnableSlidingStateWindow();
 
   // Write a raw string to the log to be used as a preamble.
   // No check is made that the 'preamble' is actually at the beginning
   // of the log. The preample is used to write code events saved in the
   // snapshot.
   static void Preamble(const char* content);
@@ skipping 74 matching lines @@
   static void RegExpCompileEvent(Handle<JSRegExp> regexp, bool in_cache);
 
   // Log an event reported from generated code
   static void LogRuntime(Vector<const char> format, JSArray* args);
 
 #ifdef ENABLE_LOGGING_AND_PROFILING
   static StateTag state() {
     return current_state_ ? current_state_->state() : OTHER;
   }
 
-  static bool is_enabled() { return logfile_ != NULL; }
+  static bool is_enabled();
 
   // Pause/Resume collection of profiling data.
   // When data collection is paused, Tick events are discarded until
   // data collection is Resumed.
   static bool IsProfilerPaused();
   static void PauseProfiler();
   static void ResumeProfiler();
 
+  // If logging is performed into a memory buffer, allows to
+  // retrieve previously written messages. See v8.h.
+  static int GetLogLines(int from_pos, char* dest_buf, int max_size);
+
  private:
 
   // Emits the source code of a regexp. Used by regexp events.
   static void LogRegExpSource(Handle<JSRegExp> regexp);
 
   // Emits a profiler tick event. Used by the profiler thread.
   static void TickEvent(TickSample* sample, bool overflow);
 
   static void ApiEvent(const char* name, ...);
 
   // Logs a StringEvent regardless of whether FLAG_log is true.
   static void UncheckedStringEvent(const char* name, const char* value);
 
-  // Size of buffer used for formatting log messages.
-  static const int kMessageBufferSize = 2048;
-
-  // Buffer used for formatting log messages. This is a singleton buffer and
-  // mutex_ should be acquired before using it.
-  static char* message_buffer_;
-
-  // When logging is active, logfile_ refers the file events are written to.
-  // mutex_ should be acquired before using logfile_.
-  static FILE* logfile_;
-
   // The sampler used by the profiler and the sliding state window.
   static Ticker* ticker_;
 
   // When the statistical profile is active, profiler_
   // points to a Profiler, that handles collection
   // of samples.
   static Profiler* profiler_;
 
-  // mutex_ is a Mutex used for enforcing exclusive
-  // access to the formatting buffer and the log file.
-  static Mutex* mutex_;
-
   // A stack of VM states.
   static VMState* current_state_;
 
   // Singleton bottom or default vm state.
   static VMState bottom_state_;
 
   // SlidingStateWindow instance keeping a sliding window of the most
   // recent VM states.
   static SlidingStateWindow* sliding_state_window_;
 
   // Internal implementation classes with access to
   // private members.
-  friend class LogMessageBuilder;
   friend class EventLog;
   friend class TimeLog;
   friend class Profiler;
   friend class SlidingStateWindow;
   friend class VMState;
 #else
   static bool is_enabled() { return false; }
 #endif
 };
 
 
 // Class that extracts stack trace, used for profiling.
 class StackTracer BASE_EMBEDDED {
  public:
   explicit StackTracer(unsigned int low_stack_bound)
       : low_stack_bound_(low_stack_bound) { }
   void Trace(TickSample* sample);
  private:
 
   unsigned int low_stack_bound_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LOG_H_