项目日志——日志输出格式化模块的设计、实现、测试

日志输出格式化模块

日志格式化的设计

对日志消息进行格式化，指定成为指定格式的字符串

定义有下面的格式化字符，支持用户自定义输出格式

• pattern成员
  • %d 日期，子格式{%H:%M:%S}
  • %T 缩进
  • %t 线程ID
  • %p 日志级别
  • %c 日志器名称
  • %f 文件名
  • %l 行号
  • %m 日志消息
  • %n 换行
• std::vector<FormatItem::ptr> items;成员
  • 用于格式化对应子项的内容，将日志信息的有效内容提取出来

FormatItem类负责日志消息子项的获取以及格式化，包含以下的子类

• MsgFormatItem : 从LogMsg中取出有效的日志数据
• LevelFormatItem : 取出日志等级
• NameFormatItem : 取出日志器名称
• ThreadFormatItem : 取出线程ID
• TimeFormatItem : 取出时间戳，并按照指定格式格式化
• CFileFormatItem : 取出源文件名称
• CLineFormatItem : 取出源码所在行号
• TabFormatItem : 一个制表符缩进
• NLineFormatItem : 一个换行
• OtherFormatItem : 其他非格式化字符的子项

日志格式化子项的设计

从日志消息中取出指定元素，进行字符串连接

设计思想就是，抽象出一共格式化子项的基类，派生出不同的格式化子项的子类

子类就包含了上面的日志消息子项的内容

在父类中定义父类指针数组，指向不同的格式化子类对象，这样就能在父类中调用不同子类的功能

日志格式化子类的实现

#pragma once#include "level.hpp"
#include "message.hpp"
#include <ctime>namespace Xulog
{// 抽象格式化子项的基类class FormatItem{public:using ptr = std::shared_ptr<FormatItem>;virtual void format(std::ostream &out, LogMsg &msg) = 0;};// 派生格式化子项的子类class MsgFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._payload;}};class LevelFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << LogLevel::toString(msg._level);}};class TimeFormatItem : public FormatItem{public:TimeFormatItem(std::string &fmt = "%H:%M:%S"): _time_fmt(fmt){}void format(std::ostream &out, LogMsg &msg) override{struct tm st;localtime_r(&msg._ctime, &st);char tmp[32] = {0};strftime(tmp, 31, _time_fmt.c_str(), &st);out << tmp;}private:std::string _time_fmt; // %H:%M:%S};class FileFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._file;}};class LineFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._line;}};class ThreadFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._tid;}};class LoggerFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._logger;}};class TabFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << "\t";}};class NLineFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << "\n";}};class OtherFormatItem : public FormatItem{public:OtherFormatItem(std::string &str): _str(str){}void format(std::ostream &out, LogMsg &msg) override{out << _str;}private:std::string _str;};
}

日志格式器的实现

#pragma once#include "level.hpp"
#include "message.hpp"
#include <ctime>
#include <vector>
#include <cassert>
#include <sstream>
#include <memory>
namespace Xulog
{// 抽象格式化子项的基类class FormatItem{public:using ptr = std::shared_ptr<FormatItem>;virtual void format(std::ostream &out, LogMsg &msg) = 0;};// 派生格式化子项的子类class MsgFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._payload;}};class LevelFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << LogLevel::toString(msg._level);}};class TimeFormatItem : public FormatItem{public:TimeFormatItem(const std::string &fmt = "%H:%M:%S"): _time_fmt(fmt){}void format(std::ostream &out, LogMsg &msg) override{struct tm st;localtime_r(&msg._ctime, &st);char tmp[32] = {0};strftime(tmp, 31, _time_fmt.c_str(), &st);out << tmp;}private:std::string _time_fmt; // %H:%M:%S};class FileFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._file;}};class LineFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._line;}};class ThreadFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._tid;}};class LoggerFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << msg._logger;}};class TabFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << "\t";}};class NLineFormatItem : public FormatItem{public:void format(std::ostream &out, LogMsg &msg) override{out << "\n";}};class OtherFormatItem : public FormatItem{public:OtherFormatItem(const std::string &str): _str(str){}void format(std::ostream &out, LogMsg &msg) override{out << _str;}private:std::string _str;};/*%d 日期，子格式{%H:%M:%S}%T 缩进%t 线程ID%p 日志级别%c 日志器名称%f 文件名%l 行号%m 日志消息%n 换行*/class Formatter{public:Formatter(const std::string &pattern = "[%d{%H:%M:%S}][%t][%c][%f:%l][%p]%T%m%n"): _pattern(pattern){assert(parsePattern());}// 对msg进行格式化std::string Format(LogMsg &msg){std::stringstream ss;Format(ss, msg);return ss.str();}void Format(std::ostream &out, LogMsg &msg){for (auto &item : _items){item->format(out, msg);}}// 对格式化内容进行解析/*1. 没有以%起始的字符都是原始字符串2. 遇到%则是原始字符串的结束3. %%表示原始的%4. 如果遇到{则说明这是格式化字符的子格式，遇到}结束*/private:bool parsePattern(){std::vector<std::pair<std::string, std::string>> fmt_order;size_t pos = 0;std::string key, val;// 字符串解析while (pos < _pattern.size()){if (_pattern[pos] != '%'){val.push_back(_pattern[pos++]);continue;}if (pos + 1 < _pattern.size() && _pattern[pos + 1] == '%'){val.push_back('%');pos += 2;continue;}// 原始字符串处理完毕if (val.empty() == false){fmt_order.push_back(std::make_pair("", val));val.clear();}if (pos >= _pattern.size()){std::cout << "%后没有有效字符" << std::endl;return false;}pos+=1;key = _pattern[pos];if (pos + 1 < _pattern.size() && _pattern[pos + 1] == '{'){pos += 2;while (pos < _pattern.size() && _pattern[pos] != '}'){val.push_back(_pattern[pos++]);}if (pos >= _pattern.size()){std::cout << "规则中{}匹配出错" << std::endl;return false;}}fmt_order.push_back(std::make_pair(key, val));pos++;key.clear();val.clear();}// 初始化成员for (auto &it : fmt_order){_items.push_back(createItem(it.first, it.second));}return true;}// 根据不同的格式化字符，创建不同的格式化子项的对象FormatItem::ptr createItem(const std::string &key, const std::string &value){if (key == "d")return std::make_shared<TimeFormatItem>(value);if (key == "t")return std::make_shared<ThreadFormatItem>();if (key == "c")return std::make_shared<LoggerFormatItem>();if (key == "f")return std::make_shared<FileFormatItem>();if (key == "l")return std::make_shared<LineFormatItem>();if (key == "p")return std::make_shared<LevelFormatItem>();if (key == "T")return std::make_shared<TabFormatItem>();if (key == "m")return std::make_shared<MsgFormatItem>();if (key == "n")return std::make_shared<NLineFormatItem>();if(key.empty())return std::make_shared<OtherFormatItem>(value);std::cout<<"没有对应的格式化字符:'%"<<key<<"'\n";exit(1);return FormatItem::ptr();}private:std::string _pattern; // 格式化规则字符串std::vector<FormatItem::ptr> _items;};
}

解析器的实现

格式化字符串的解析规则是这样的

1. 没有以%起始的字符都是原始字符串
2. 遇到%则是原始字符串的结束
3. %%表示原始的%
4. 如果遇到{则说明这是格式化字符的子格式，遇到}结束

这样一直循环遍历，将处理的内容（key，value）保存下来，添加到成员items成员数组中

日志输出格式化模块测试

#include "util.hpp"
#include "level.hpp"
#include "format.hpp"
int main()
{// 测试日志格式化模块Xulog::LogMsg msg(Xulog::LogLevel::value::ERROR, 124, "main.cc", "root", "格式化功能测试");Xulog::Formatter fmt1;Xulog::Formatter fmt2("%c{}");std::string str1 = fmt1.Format(msg);std::string str2 = fmt2.Format(msg);std::cout << str1 << str2;return 0;
}