Implement a dynamically growing memory log buffer with an upper limit.

src/log-utils.h

Index: src/log-utils.h
diff --git a/src/log-utils.h b/src/log-utils.h
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+++ b/src/log-utils.h
@@ -0,0 +1,188 @@
+// 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#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.
+//
+// An instance of this class is created dynamically by Log.
+class LogDynamicBuffer {
+ public:
+  LogDynamicBuffer(int block_size, int max_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 <= that 'buf_size'.

[Søren Thygesen Gjesse, 2009/05/27 12:00:40]

Remove that

[Mikhail Naganov, 2009/05/28 07:05:35]

Done.

+  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).
+  int Write(const char* data, int data_size);
+
+ private:
+  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_; }
+
+  const int block_size_;
+  const int max_size_;
+  ScopedVector<char*> blocks_;
+  int write_pos_;
+  int block_index_;
+  int block_write_pos_;
+};
+
+
+// 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();
+
+  // 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;
+  }
+
+ 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);
+  }
+
+  // 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;
+
+  // 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_;
+
+  friend class LogMessageBuilder;
+};
+
+
+// Utility class for formatting log messages. It fills the message into the
+// static buffer in Log.
+class LogMessageBuilder BASE_EMBEDDED {
+ public:
+  // Create a message builder starting from position 0. This acquires the mutex
+  // in the log as well.
+  explicit LogMessageBuilder();
+  ~LogMessageBuilder() { }
+
+  // Append string data to the log message.
+  void Append(const char* format, ...);
+
+  // Append string data to the log message.
+  void Append(const char* format, va_list args);
+
+  // Append a character to the log message.
+  void Append(const char c);
+
+  // Append a heap string.
+  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);
+
+ private:
+  ScopedLock sl;
+  int pos_;
+};
+
+#endif  // ENABLE_LOGGING_AND_PROFILING
+
+} }  // namespace v8::internal
+
+#endif  // V8_LOG_UTILS_H_