learn_muduo

Logger

Logger有六個日志等級

• TRACE
• DEBUG
• INFO
• WARN
• ERROR
• FATAL

日志的輸出語句是通過宏定義完成，編譯期完成宏定義替換，創建Logger的臨時對象。

#define LOG_TRACE if (muduo::Logger::logLevel() <= muduo::Logger::TRACE) \muduo::Logger(__FILE__, __LINE__, muduo::Logger::TRACE, __func__).stream()#define LOG_DEBUG if (muduo::Logger::logLevel() <= muduo::Logger::DEBUG) \muduo::Logger(__FILE__, __LINE__, muduo::Logger::DEBUG, __func__).stream()#define LOG_INFO if (muduo::Logger::logLevel() <= muduo::Logger::INFO) \muduo::Logger(__FILE__, __LINE__).stream()#define LOG_WARN muduo::Logger(__FILE__, __LINE__, muduo::Logger::WARN).stream()#define LOG_ERROR muduo::Logger(__FILE__, __LINE__, muduo::Logger::ERROR).stream()#define LOG_FATAL muduo::Logger(__FILE__, __LINE__, muduo::Logger::FATAL).stream()#define LOG_SYSERR muduo::Logger(__FILE__, __LINE__, false).stream()#define LOG_SYSFATAL muduo::Logger(__FILE__, __LINE__, true).stream()

Logger的構造函數

Logger::Logger(SourceFile file, int line): impl_(INFO, 0, file, line) { }Logger::Logger(SourceFile file, int line, LogLevel level, const char* func): impl_(level, 0, file, line) {impl_.stream_ << func << ' '; }Logger::Logger(SourceFile file, int line, LogLevel level): impl_(level, 0, file, line) { }Logger::Logger(SourceFile file, int line, bool toAbort): impl_(toAbort? FATAL:ERROR, errno, file, line) { }

Impl類

Logger的構造函數中用到了Impl類，Impl類保存Logger的數據。

class Impl { public:typedef Logger::LogLevel LogLevel;Impl(LogLevel level, int old_errno, const SourceFile& file, int line);void formatTime();void finish();Timestamp time_;LogStream stream_;LogLevel level_;int line_;SourceFile basename_;}; // class Impl

日志的時間，線程號，級別等在Impl構造函數初始化時完成，將這些信息寫到LogStream對象中。

Logger::Impl::Impl(LogLevel level, int savedErrno, const SourceFile& file, int line): time_(Timestamp::now()),stream_(),level_(level),line_(line),basename_(file) {formatTime();CurrentThread::tid();stream_ << T(CurrentThread::tidString(), CurrentThread::tidStringLength());stream_ << T(LogLevelName[level], 6);if (savedErrno != 0){stream_ << strerror_tl(savedErrno) << " (errno=" << savedErrno << ") ";} }

Logger的析構

Logger是臨時對象，因此Logger的析構接管日志的輸出工作。

// 將msg輸出到stdout void defaultOutput(const char* msg, int len) {size_t n = fwrite(msg, 1, len, stdout); }Logger::OutputFunc g_output = defaultOutput;// 文件名和行號 void Logger::Impl::finish() {stream_ << " - " << basename_ << ":" << line_ << "\n"; }Logger::~Logger() {impl_.finish();const LogStream::Buffer& buf(stream().buffer());g_output(buf.data(), buf.length());if (impl_.level_ == FATAL) {g_flush();abort();} }

LogStream

FixedBuffer

LogStream中維護一個FixedBuffer::Buffer的緩沖區，FixedBuffer提供了append()、data()、length()等一些字符串的基本操作。

template<int SIZE> class FixedBuffer : noncopyable { public:FixedBuffer(): cur_(data_){setCookie(cookieStart);}~FixedBuffer(){setCookie(cookieEnd);}void append(const char* buf, size_t len){if (implicit_cast<size_t>(avail()) > len){memcpy(cur_, buf, len);cur_ += len;}}const char* data() const { return data_; }int length() const { return static_cast<int>(cur_ - data_); }// write to data_ directlychar* current() { return cur_; }int avail() { return static_cast<int>(end() - cur_); }void add(size_t len) { cur_ += len; }void reset() { cur_ = data_; }void bzero() { memZero(data_, sizeof(data_)); }// for used by GDBconst char* debugString();void setCookie(void (*cookie)()) { cookie_ = cookie; }// for used by unit teststring toString() const {return string(data_, length()); }StringPiece toStringPiece() const { return StringPiece(data_, length()); }private:const char* end() const { return data_ + sizeof data_; }// Must be outline function for cookies.static void cookieStart();static void cookieEnd();void (*cookie_)();char data_[SIZE];char* cur_; }; // class fixedBuffer

LogStream

Logstream重載了各種 operator << 函數，用于處理多種類型的數據，將這些日志信息追加到Buffer中。

class LogStream : noncopyable {typedef LogStream self;public:typedef detail::FixedBuffer<detail::kSmallBuffer> Buffer;/* 重載的operator<<函數，將日志信息存放在緩沖區中 */self& operator<<(const char* str){if (str){buffer_.append(str, strlen(str));}else{buffer_.append("(null)", 6);}return *this;}/* ... */private:Buffer buffer_;static const int kMaxNumericSize = 32; };

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