Handle filling up of memory buffer to make log processing in DevTools Profiler easier.

src/log-utils.h

 // Copyright 2006-2009 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 17 matching lines @@
 #ifndef V8_LOG_UTILS_H_
 #define V8_LOG_UTILS_H_
 
 namespace v8 {
 namespace internal {
 
 #ifdef ENABLE_LOGGING_AND_PROFILING
 
 // A memory buffer that increments its size as you write in it.  Size
 // is incremented with 'block_size' steps, never exceeding 'max_size'.
-// During growth, memory contents are never copied.
+// During growth, memory contents are never copied.  At the end of the
+// buffer an amount of memory specified in 'seal_size' is reserved.
+// When writing position reaches max_size - seal_size, buffer auto-seals
+// itself with 'seal' and allows no further writes. Data pointed by
+// 'seal' must be available during entire LogDynamicBuffer lifetime.
 //
 // An instance of this class is created dynamically by Log.
 class LogDynamicBuffer {
  public:
-  LogDynamicBuffer(int block_size, int max_size);
+  LogDynamicBuffer(
+      int block_size, int max_size, const char* seal, int seal_size);
 
   ~LogDynamicBuffer();
 
   // Reads contents of the buffer starting from 'from_pos'.  Upon
   // return, 'dest_buf' is filled with the data. Actual amount of data
   // filled is returned, it is <= 'buf_size'.
   int Read(int from_pos, char* dest_buf, int buf_size);
 
   // Writes 'data' to the buffer, making it larger if necessary.  If
   // data is too big to fit in the buffer, it doesn't get written at
-  // all. Returns amount of data written (it is either 'data_size', or
-  // 0, if 'data' is too big).
+  // all. In that case, buffer auto-seals itself and stops to accept
+  // any incoming writes. Returns amount of data written (it is either
+  // 'data_size', or 0, if 'data' is too big).
   int Write(const char* data, int data_size);
 
  private:
   void AllocateBlock(int index) {
     blocks_[index] = NewArray<char>(block_size_);
   }
 
   int BlockIndex(int pos) const { return pos / block_size_; }
 
   int BlocksCount() const { return BlockIndex(max_size_) + 1; }
 
   int PosInBlock(int pos) const { return pos % block_size_; }
 
+  int Seal();
+
+  int WriteInternal(const char* data, int data_size);
+
   const int block_size_;
   const int max_size_;
+  const char* seal_;
+  const int seal_size_;
   ScopedVector<char*> blocks_;
   int write_pos_;
   int block_index_;
   int block_write_pos_;
+  bool is_sealed_;
 };
 
 
 // Functions and data for performing output of log messages.
 class Log : public AllStatic {
  public:
   // Opens stdout for logging.
   static void OpenStdout();
 
   // Opens file for logging.
   static void OpenFile(const char* name);
 
   // Opens memory buffer for logging.
   static void OpenMemoryBuffer();
 
+  // Disables logging, but preserves acquired resources.
+  static void stop() { is_stopped_ = true; }
+
   // Frees all resources acquired in Open... functions.
   static void Close();
 
   // See description in include/v8.h.
   static int GetLogLines(int from_pos, char* dest_buf, int max_size);
 
   // Returns whether logging is enabled.
   static bool IsEnabled() {
-    return output_handle_ != NULL || output_buffer_ != NULL;
+    return !is_stopped_ && (output_handle_ != NULL || output_buffer_ != NULL);
   }
 
  private:
   typedef int (*WritePtr)(const char* msg, int length);
 
   // Initialization function called from Open... functions.
   static void Init();
 
   // Write functions assume that mutex_ is acquired by the caller.
   static WritePtr Write;
 
   // Implementation of writing to a log file.
   static int WriteToFile(const char* msg, int length) {
     ASSERT(output_handle_ != NULL);
     int rv = fwrite(msg, 1, length, output_handle_);
     ASSERT(length == rv);
     return rv;
   }
 
   // Implementation of writing to a memory buffer.
   static int WriteToMemory(const char* msg, int length) {
     ASSERT(output_buffer_ != NULL);
     return output_buffer_->Write(msg, length);
   }
 
+  // Whether logging is stopped (e.g. due to insufficient resources).
+  static bool is_stopped_;
+
   // When logging is active, either output_handle_ or output_buffer_ is used
   // to store a pointer to log destination. If logging was opened via OpenStdout
   // or OpenFile, then output_handle_ is used. If logging was opened
   // via OpenMemoryBuffer, then output_buffer_ is used.
   // mutex_ should be acquired before using output_handle_ or output_buffer_.
   static FILE* output_handle_;
 
   static LogDynamicBuffer* output_buffer_;
 
   // Size of dynamic buffer block (and dynamic buffer initial size).
   static const int kDynamicBufferBlockSize = 65536;
 
   // Maximum size of dynamic buffer.
   static const int kMaxDynamicBufferSize = 50 * 1024 * 1024;
 
+  // Message to "seal" dynamic buffer with.
+  static const char* kDynamicBufferSeal;
+
   // mutex_ is a Mutex used for enforcing exclusive
   // access to the formatting buffer and the log file or log memory buffer.
   static Mutex* mutex_;
 
   // 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_;
@@ skipping 24 matching lines @@
   void Append(String* str);
 
   void AppendDetailed(String* str, bool show_impl_info);
 
   // Write the log message to the log file currently opened.
   void WriteToLogFile();
 
   // Write a null-terminated string to to the log file currently opened.
   void WriteCStringToLogFile(const char* str);
 
+  // A handler that is called when Log::Write fails.
+  typedef void (*WriteFailureHandler)();
+  static WriteFailureHandler write_failure_handler;

[Søren Thygesen Gjesse, 2009/05/28 13:23:35]

Please make the write_failure_handler member private and add a static setter.

[Mikhail Naganov, 2009/05/28 13:52:52]

Done.

+
  private:
   ScopedLock sl;
   int pos_;
 };
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal
 
 #endif  // V8_LOG_UTILS_H_