FileLogger.h

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// Copyright Onix Solutions Limited [OnixS]. All rights reserved.
//
// This software owned by Onix Solutions Limited [OnixS] and is 
// protected by copyright law and international copyright treaties.
//
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// agreements granting a non-assignable, non-transferable and non-exclusive license 
// to use the software for it's own data processing purposes under the terms defined 
// in the Agreement.
//
// Except as otherwise granted within the terms of the Agreement, copying or 
// reproduction of any part of this source code or associated reference material 
// to any other location for further reproduction or redistribution, and any 
// amendments to this copyright notice, are expressly prohibited.
//
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//

#pragma once

#include <OnixS/CME/MDH/String.h>
#include <OnixS/CME/MDH/Integral.h>
#include <OnixS/CME/MDH/Logger.h>
#include <OnixS/CME/MDH/Time.h>

ONIXS_CMEMDH_NAMESPACE_BEGIN

/// Base parameters affecting synchronous logging services.
ONIXS_CMEMDH_LTWT_CLASS FileLoggerSettings
{
    std::string filename_;
    UInt64 fileSizeLimit_;

    LogSeverity::Enum severity_;

    WatchService* watch_;

public:
    /// Initializes parameters with default values. 
    FileLoggerSettings()
        : filename_()
        , fileSizeLimit_(2145386496)
        , severity_(LogSeverity::Regular)
        , watch_(&UtcWatch::service())
    {
    }

    /// Cleans everything up. 
    ~FileLoggerSettings()
    {
    }

    /// Log file name.
    /// 
    /// Ignored if logging is disabled.
    const std::string& filename() const
    {
        return filename_;
    }

    /// Updates log file name.
    /// 
    /// Ignored if logging is disabled.
    void filename(const std::string& value)
    {
        filename_ = value;
    }

    /// Log file size limit (in bytes).
    ///
    /// Handler detaches logged data into separate
    /// file upon reaching given size limit.
    ///
    /// @note Default value is '2145386496'.
    UInt64 fileSizeLimit() const
    {
        return fileSizeLimit_;
    }

    /// Sets logFileSizeLimit. @see logFileSizeLimit.
    void fileSizeLimit(UInt64 value)
    {
        fileSizeLimit_ = value;
    }

    /// Specifies whether the logger should output events 
    /// and which of events should be put into the log.
    ///
    /// @note The default value is LogEntrySeverity::Regular.
    LogSeverity::Enum severityLevel() const
    {
        return severity_;
    }

    /// Specifies whether logger should output its events 
    /// and which of events should be put into the log.
    void severityLevel(LogSeverity::Enum value)
    {
        severity_ = value;
    }

    /// Watch service used by logger while 
    /// assigning timestamps to log entries. 
    WatchService& watch() const
    {
        return *watch_;
    }

    /// Watch service used by logger while 
    /// assigning timestamps to log entries. 
    void watch(WatchService& watch)
    {
        watch_ = &watch;
    }
};

/// Makes filename for log file for the given channel. 
ONIXS_CMEMDH_EXPORTED
std::string
makeLogFilename(UInt32);

ONIXS_CMEMDH_EXPORTED_CLASS_DECL(FileLogger);

/// Collection of events raised by FileLogger during its life time. 
ONIXS_CMEMDH_EXPORTED_STRUCT FileLoggerListener
{
    /// Invoked by FileLogger in case of issue. 
    /// 
    /// FileLogger may experience issues like inability to 
    /// add a new entry due to insufficient disk space. Once 
    /// occurred, issue is reported through given callback. 
    virtual 
    void 
    onFileLoggerIssue(
        const FileLogger&, 
        const Char*)
    {
    }
};

/// Implements logging services to put logged data into a 
/// regular file. Provides additional facilities like splitting 
/// logged data into chunks not exceeding specified size limit. 
ONIXS_CMEMDH_EXPORTED_CLASS FileLogger : public Logger
{
    // File logger machinery implementation. 
    ONIXS_CMEMDH_LTWT_CLASS_DECL(Workhorse);
    Workhorse* workhorse_;

public:
    /// Initializes logger according to given settings.
    FileLogger(
        const FileLoggerSettings&,
        FileLoggerListener* = NULL);

    /// Disposes logging machinery.
    ~FileLogger();

    /// Configuration of given logger instance. 
    const 
    FileLoggerSettings& 
    settings() const;

    /// Adds a new entry into the log. 
    ///
    /// Returns instance for further fulfill or NULL if 
    /// given severity is lower than defined by settings 
    /// at the moment of instance construction. 
    LogEntry* 
    addEntry(
        LogSeverity::Enum);

    /// Rolls over current log and starts recording a new chunk. 
    ///
    /// Detached data is stored into a file whose name is 
    /// suffixed with a timestamp taken at the moment of detach. 
    /// Timestamp is taken using watch service associated with 
    /// the logger using its settings. 
    /// 
    /// @return Name of file containing detached data. 
    std::string rollover();
};

ONIXS_CMEMDH_NAMESPACE_END