loghandler.hpp

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/* Copyright (C) 2003 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

#ifndef LOGHANDLER_H
#define LOGHANDLER_H

#include "Logger.hpp"

/**
 * This class is the base class for all log handlers. A log handler is 
 * responsible for formatting and writing log messages to a specific output.
 *
 * A log entry consists of three parts: a header, <body/log message and a footer.
 * <pre>
 * 09:17:37 2002-03-13 [MgmSrv] INFO     -- Local checkpoint 13344 started.
 * </pre>
 *
 * Header format: TIME&DATE CATEGORY LEVEL -- 
 *   TIME&DATE = ctime() format.
 *   CATEGORY  = Any string.
 *   LEVEL     = ALERT to DEBUG (Log levels)
 *
 * Footer format: \n (currently only newline)
 *
 * @version #@ $Id: LogHandler.hpp,v 1.7 2003/09/01 10:15:53 innpeno Exp $
 */
class LogHandler
{
public:  
  /**
   * Default constructor.
   */
  LogHandler();
  
  /**
   * Destructor.
   */
  virtual ~LogHandler();

  /**
   * Opens/initializes the log handler.
   *
   * @return true if successful.
   */ 
  virtual bool open() = 0;

  /**
   * Closes/free any allocated resources used by the log handler. 
   *
   * @return true if successful.
   */ 
  virtual bool close() = 0;
  
  /**
   * Append a log message to the output stream/file whatever.
   * append() will call writeHeader(), writeMessage() and writeFooter() for
   * a child class and in that order. Append checks for repeated messages.
   * append_impl() does not check for repeats.
   *
   * @param pCategory the category/name to tag the log entry with.
   * @param level the log level.
   * @param pMsg the log message.
   */
  void append(const char* pCategory, Logger::LoggerLevel level,
	      const char* pMsg);
  void append_impl(const char* pCategory, Logger::LoggerLevel level,
		   const char* pMsg);

  /**
   * Returns a default formatted header. It currently has the
   * follwing default format: '%H:%M:%S %Y-%m-%d [CATEGORY] LOGLEVEL --' 
   *
   * @param pStr the header string to format.
   * @param pCategory a category/name to tag the log entry with.
   * @param level the log level.
   * @return the header.
   */
  const char* getDefaultHeader(char* pStr, const char* pCategory, 
			       Logger::LoggerLevel level) const;
  
  /**
   * Returns a default formatted footer. Currently only returns a newline.
   *
   * @return the footer.
   */
  const char* getDefaultFooter() const;
  
  /**
   * Returns the date and time format used by ctime().
   *
   * @return the date and time format.
   */
  const char* getDateTimeFormat() const;

  /**
   * Sets the date and time format. It needs to have the same arguments
   * a ctime().
   *
   * @param pFormat  the date and time format.
   */
  void setDateTimeFormat(const char* pFormat);
  
  /**
   * Returns the error code.
   */
  int getErrorCode() const;

  /**
   * Sets the error code.
   *
   * @param code the error code.
   */
  void setErrorCode(int code);

  /**
   * Returns the error string.
   */
  char* getErrorStr();

  /**
   * Sets the error string.
   *
   * @param str the error string.
   */
  void setErrorStr(char* str);

  /**
   * Parse logstring parameters
   *
   * @param params list of parameters, formatted as "param=value", 
   * entries separated by ","
   * @return true on success, false on failure
   */ 
  bool parseParams(const BaseString &params);

  /**
   * Sets a parameters. What parameters are accepted depends on the subclass.
   *
   * @param param name of parameter
   * @param value value of parameter
   */
  virtual bool setParam(const BaseString &param, const BaseString &value) = 0;

  /**
   * Checks that all necessary parameters have been set.
   *
   * @return true if all parameters are correctly set, false otherwise
   */
  virtual bool checkParams();

protected:
  /** Max length of the date and time header in the log. */
  STATIC_CONST( MAX_DATE_TIME_HEADER_LENGTH = 64 );
  /** Max length of the header the log. */
  STATIC_CONST( MAX_HEADER_LENGTH = 128 );
  /** Max lenght of footer in the log. */
  STATIC_CONST( MAX_FOOTER_LENGTH = 128 );

  /**
   * Write the header to the log.
   * 
   * @param pCategory the category to tag the log with.
   * @param level the log level.
   */
  virtual void writeHeader(const char* category, Logger::LoggerLevel level) = 0;

  /**
   * Write the message to the log.
   * 
   * @param pMsg the message to log.
   */
  virtual void writeMessage(const char* pMsg) = 0;

  /**
   * Write the footer to the log.
   * 
   */
  virtual void writeFooter() = 0;
  
private: 
  /**
   * Returns a string date and time string.
   * @note does not update time, uses m_now as time
   * @param pStr a string.
   * @return a string with date and time.
   */
  char* getTimeAsString(char* pStr) const;
  time_t m_now;

  /** Prohibit */
  LogHandler(const LogHandler&);
  LogHandler* operator = (const LogHandler&);
  bool operator == (const LogHandler&);

  const char* m_pDateTimeFormat;
  int m_errorCode;
  char* m_errorStr;

  // for handling repeated messages
  unsigned m_count_repeated_messages;
  unsigned m_max_repeat_frequency;
  time_t m_last_log_time;
  char m_last_category[MAX_HEADER_LENGTH];
  char m_last_message[MAX_LOG_MESSAGE_SIZE];
  Logger::LoggerLevel m_last_level;
};

#endif