log-utils.h

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// Copyright 2006-2009 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.
 
#ifndef V8_LOG_UTILS_H_
#define V8_LOG_UTILS_H_
 
#include "src/allocation.h"
 
namespace v8 {
namespace internal {
 
class Logger;
 
// Functions and data for performing output of log messages.
class Log {
 public:
  // Performs process-wide initialization.
  void Initialize(const char* log_file_name);
 
  // Disables logging, but preserves acquired resources.
  void stop() { is_stopped_ = true; }
 
  static bool InitLogAtStart() {
    return FLAG_log || FLAG_log_api || FLAG_log_code || FLAG_log_gc
        || FLAG_log_handles || FLAG_log_suspect || FLAG_log_regexp
        || FLAG_ll_prof || FLAG_perf_basic_prof || FLAG_perf_jit_prof
        || FLAG_log_internal_timer_events;
  }
 
  // Frees all resources acquired in Initialize and Open... functions.
  // When a temporary file is used for the log, returns its stream descriptor,
  // leaving the file open.
  FILE* Close();
 
  // Returns whether logging is enabled.
  bool IsEnabled() {
    return !is_stopped_ && output_handle_ != NULL;
  }
 
  // Size of buffer used for formatting log messages.
  static const int kMessageBufferSize = 2048;
 
  // This mode is only used in tests, as temporary files are automatically
  // deleted on close and thus can't be accessed afterwards.
  static const char* const kLogToTemporaryFile;
  static const char* const kLogToConsole;
 
  // Utility class for formatting log messages. It fills the message into the
  // static buffer in Log.
  class MessageBuilder BASE_EMBEDDED {
   public:
    // Create a message builder starting from position 0.
    // This acquires the mutex in the log as well.
    explicit MessageBuilder(Log* log);
    ~MessageBuilder() { }
 
    // Append string data to the log message.
    void Append(const char* format, ...);
 
    // Append string data to the log message.
    void AppendVA(const char* format, va_list args);
 
    // Append a character to the log message.
    void Append(const char c);
 
    // Append double quoted string to the log message.
    void AppendDoubleQuotedString(const char* string);
 
    // Append a heap string.
    void Append(String* str);
 
    // Appends an address.
    void AppendAddress(Address addr);
 
    void AppendSymbolName(Symbol* symbol);
 
    void AppendDetailed(String* str, bool show_impl_info);
 
    // Append a portion of a string.
    void AppendStringPart(const char* str, int len);
 
    // Write the log message to the log file currently opened.
    void WriteToLogFile();
 
   private:
    Log* log_;
    base::LockGuard<base::Mutex> lock_guard_;
    int pos_;
  };
 
 private:
  explicit Log(Logger* logger);
 
  // Opens stdout for logging.
  void OpenStdout();
 
  // Opens file for logging.
  void OpenFile(const char* name);
 
  // Opens a temporary file for logging.
  void OpenTemporaryFile();
 
  // Implementation of writing to a log file.
  int WriteToFile(const char* msg, int length) {
    DCHECK(output_handle_ != NULL);
    size_t rv = fwrite(msg, 1, length, output_handle_);
    DCHECK(static_cast<size_t>(length) == rv);
    USE(rv);
    fflush(output_handle_);
    return length;
  }
 
  // Whether logging is stopped (e.g. due to insufficient resources).
  bool is_stopped_;
 
  // When logging is active output_handle_ is used to store a pointer to log
  // destination.  mutex_ should be acquired before using output_handle_.
  FILE* output_handle_;
 
  // mutex_ is a Mutex used for enforcing exclusive
  // access to the formatting buffer and the log file or log memory buffer.
  base::Mutex mutex_;
 
  // Buffer used for formatting log messages. This is a singleton buffer and
  // mutex_ should be acquired before using it.
  char* message_buffer_;
 
  Logger* logger_;
 
  friend class Logger;
};
 
 
} }  // namespace v8::internal
 
#endif  // V8_LOG_UTILS_H_