text: // Copyright (c) 2012 The Chromium 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 BASE_LOGGING_WIN_H_
  #define BASE_LOGGING_WIN_H_
  
  #include <stddef.h>
  
  #include <string>
  
  #include "base/base_export.h"
  #include "base/logging.h"
  #include "base/macros.h"
  #include "base/win/event_trace_provider.h"
  
  namespace base {
  template <typename Type>
  struct StaticMemorySingletonTraits;
  }  // namespace base
  
  namespace logging {
  
  // Event ID for the log messages we generate.
  EXTERN_C BASE_EXPORT const GUID kLogEventId;
  
  // Feature enable mask for LogEventProvider.
  enum LogEnableMask {
    // If this bit is set in our provider enable mask, we will include
    // a stack trace with every log message.
    ENABLE_STACK_TRACE_CAPTURE = 0x0001,
    // If this bit is set in our provider enable mask, the provider will log
    // a LOG message with only the textual content of the message, and no
    // stack trace.
    ENABLE_LOG_MESSAGE_ONLY = 0x0002,
  };
  
  // The message types our log event provider generates.
  // ETW likes user message types to start at 10.
  enum LogMessageTypes {
    // A textual only log message, contains a zero-terminated string.
    LOG_MESSAGE = 10,
    // A message with a stack trace, followed by the zero-terminated
    // message text.
    LOG_MESSAGE_WITH_STACKTRACE = 11,
    // A message with:
    //  a stack trace,
    //  the line number as a four byte integer,
    //  the file as a zero terminated UTF8 string,
    //  the zero-terminated UTF8 message text.
    LOG_MESSAGE_FULL = 12,
  };
  
  // Trace provider class to drive log control and transport
  // with Event Tracing for Windows.
  class BASE_EXPORT LogEventProvider : public base::win::EtwTraceProvider {
   public:
    static LogEventProvider* GetInstance();
  
    static bool LogMessage(logging::LogSeverity severity, const char* file,
        int line, size_t message_start, const std::string& str);
  
    static void Initialize(const GUID& provider_name);
    static void Uninitialize();
  
   protected:
    // Overridden to manipulate the log level on ETW control callbacks.
    void OnEventsEnabled() override;
    void OnEventsDisabled() override;
  
   private:
    LogEventProvider();
  
    // The log severity prior to OnEventsEnabled,
    // restored in OnEventsDisabled.
    logging::LogSeverity old_log_level_;
  
    friend struct base::StaticMemorySingletonTraits<LogEventProvider>;
    DISALLOW_COPY_AND_ASSIGN(LogEventProvider);
  };
  
  }  // namespace logging
  
  #endif  // BASE_LOGGING_WIN_H_
  