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/**
* @file formatter.h
* @author Harold Bruintjes <h.bruintjes@cs.rwth-aachen.de>
*
* Define the Formatter class, used to format output of a sink
*/
#pragma once
#include <string>
#include <tuple>
namespace l3pp {
/**
* Formats a log messages. This is a base class that simply print the message
* with the log level prefix, see derived classes such as TemplatedFormatter
* for more interesting data.
*/
class Formatter {
friend class Logger;
static void initialize();
virtual std::string format(EntryContext const& context, std::string const& msg) const;
public:
virtual ~Formatter() {}
std::string operator()(EntryContext const& context, std::string const& msg) {
return format(context, msg);
}
};
typedef std::shared_ptr<Formatter> FormatterPtr;
/**
* Possible fields for FieldStr instance
*/
enum class Field {
/// Name of the file (everything following the last path separator)
FileName,
/// Full path of the file
FilePath,
/// Line number
Line,
/// Name of function currently executed
Function,
/// Name of the logger
LoggerName,
/// Message to be logged
Message,
/// Level of the log entry
LogLevel,
/// Number of milliseconds since the logger was initialized
WallTime,
};
/**
* Controls justification of formatted log fields.
*/
enum class Justification {
/// Left align field
LEFT,
/// Right align field
RIGHT
};
/**
* Formatter for log entry fields, with the exception of time stamp formatting
* (see TimeStr for that). The Field template argument determines which field
* is printed, see logging::Field.
* The other template arguments control the alignment of the output string.
*/
template<Field field, int Width = 0, Justification j = Justification::RIGHT, char Fill = ' '>
class FieldStr {
public:
void stream(std::ostream& os, EntryContext const& context, std::string const& msg) const;
};
/**
* Formatter for log time stamps. The constructor expects a single string
* argument which is a formatter for the time stamp. For the specification of
* this format string see the documentation for std::put_time . You can use for
* example "%c" or "%T".
* The template arguments control the alignment of the output string.
*/
class TimeStr {
std::string formatStr;
public:
TimeStr(char const* format) : formatStr(format) {
}
TimeStr(std::string const& format) : formatStr(format) {
}
void stream(std::ostream& os, EntryContext const& context, std::string const&) const;
};
/**
* Formatter which formats the output based on the (templated) arguments given.
* The arguments can be anything that implements the stream operator <<, but
* more interestingly also the various FormatField subclasses. These classes
* can output the various fields associated with a log entry.
*/
template<typename ... Formatters>
class TemplateFormatter : public Formatter {
std::tuple<Formatters...> formatters;
template <int N>
typename std::enable_if<N < (sizeof...(Formatters))>::type
formatTuple(EntryContext const& context, std::string const& msg, std::ostream& os) const {
formatElement(std::get<N>(formatters), os, context, msg);
formatTuple<N+1>(context, msg, os);
}
template <int N>
typename std::enable_if<(N >= sizeof...(Formatters))>::type
formatTuple(EntryContext const&, std::string const&, std::ostream&) const {
}
template<Field field, int Width, Justification j, char Fill>
void formatElement(FieldStr<field, Width, j, Fill> const& t, std::ostream& stream, EntryContext const& context, std::string const& msg) const {
t.stream(stream, context, msg);
}
void formatElement(TimeStr const& t, std::ostream& stream, EntryContext const& context, std::string const& msg) const {
t.stream(stream, context, msg);
}
template<typename T>
void formatElement(T const& t, std::ostream& stream, EntryContext const&, std::string const&) const {
stream << t;
}
public:
TemplateFormatter(Formatters ... formatters) :
formatters(std::forward<Formatters>(formatters)...)
{
}
std::string format(EntryContext const& context, std::string const& msg) const override;
};
/**
* Helper function to create a TemplateFormatter. Simply call with some
* formatable arguments, e.g.,
* @code{.cpp}
* logging::makeTemplateFormatter(
* logging::FieldStr<logging::Field::LogLevel>(), " - ",
* logging::FieldStr<logging::Field::Message>(), "\n");
* @endcode
*/
template<typename ... Formatters>
FormatterPtr makeTemplateFormatter(Formatters&& ... formatters) {
return std::make_shared<TemplateFormatter<Formatters...>>(std::forward<Formatters>(formatters)...);
}
}