citra/src/common/logging/backend.h

// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#pragma once

#include <chrono>
#include <cstdarg>
#include <memory>
#include <string>
#include <utility>
#include <boost/optional.hpp>
#include "common/file_util.h"
#include "common/logging/filter.h"
#include "common/logging/log.h"

namespace Log {

class Filter;

/**
 * A log entry. Log entries are store in a structured format to permit more varied output
 * formatting on different frontends, as well as facilitating filtering and aggregation.
 */
struct Entry {
    std::chrono::microseconds timestamp;
    Class log_class;
    Level log_level;
    std::string filename;
    unsigned int line_num;
    std::string function;
    std::string message;

    Entry() = default;
    Entry(Entry&& o) = default;

    Entry& operator=(Entry&& o) = default;
    Entry& operator=(const Entry& o) = default;
};

/**
 * Interface for logging backends. As loggers can be created and removed at runtime, this can be
 * used by a frontend for adding a custom logging backend as needed
 */
class Backend {
public:
    virtual ~Backend() = default;
    virtual void SetFilter(const Filter& new_filter) {
        filter = new_filter;
    }
    virtual const char* GetName() const = 0;
    virtual void Write(const Entry& entry) = 0;

private:
    Filter filter;
};

/**
 * Backend that writes to stderr without any color commands
 */
class ConsoleBackend : public Backend {
public:
    const char* GetName() const override {
        return "console";
    }
    void Write(const Entry& entry) override;
};

/**
 * Backend that writes to stderr and with color
 */
class ColorConsoleBackend : public Backend {
public:
    const char* GetName() const override {
        return "color_console";
    }
    void Write(const Entry& entry) override;
};

/**
 * Backend that writes to a file passed into the constructor
 */
class FileBackend : public Backend {
public:
    explicit FileBackend(const std::string& filename) : file(filename, "w") {}

    const char* GetName() const override {
        return "file";
    }

    void Write(const Entry& entry) override;

private:
    FileUtil::IOFile file;
};

void AddBackend(std::unique_ptr<Backend> backend);

void RemoveBackend(const std::string& backend_name);

boost::optional<Backend*> GetBackend(const std::string& backend_name);

/**
 * Returns the name of the passed log class as a C-string. Subclasses are separated by periods
 * instead of underscores as in the enumeration.
 */
const char* GetLogClassName(Class log_class);

/**
 * Returns the name of the passed log level as a C-string.
 */
const char* GetLevelName(Level log_level);

/// Creates a log entry by formatting the given source location, and message.
Entry CreateEntry(Class log_class, Level log_level, const char* filename, unsigned int line_nr,
                  const char* function, std::string message);

/**
 * The global filter will prevent any messages from even being processed if they are filtered. Each
 * backend can have a filter, but if the level is lower than the global filter, the backend will
 * never get the message
 */
void SetGlobalFilter(const Filter& filter);

} // namespace Log