项目中需要在多线程环境下，输出日志到标准输出，以下是实现过程。
首先，我们需要一个锁类，能够自动初始化，并且降低耦合。
/* * locker.h * * Created on: Apr 14, 2012 *Author: joan */#ifndef LOCKER_H_#define LOCKER_H_#include "../OPTION.h"class locker{public:inline locker(){pthread_mutex_init(&mutex,NULL);}inline ~locker(){pthread_mutex_destroy(&mutex);}inline void lock(){pthread_mutex_lock(&mutex);}inline void unlock(){pthread_mutex_unlock(&mutex);}private:pthread_mutex_t mutex;};#endif /* LOCKER_H_ */
其次，，声明日志类，重点是将构造函数私有化，将函数成员和数据成员声明为静态，添加实例指针和全局访问点。
/* * log.h * * Created on: Apr 8, 2012 *Author: joan */#ifndef LOG_H_#define LOG_H_#include "../OPTION.h"#include "locker.h"/* * this class is responsible for the running log of tinyJSE * there should only exist one instance of tinyLog, * so we use singleton to implement tinyLog */class tinyLog{public:static tinyLog *GetInstance();static void WriteLog(const char *FORMAT,…);private:tinyLog();~tinyLog();private:static tinyLog *log;static locker llock;};#endif /* LOG_H_ */然后是日志类的实现，注意全局访问点中使用double check提高性能。/* * log.cpp * * Created on: Apr 8, 2012 *Author: joan */#include "../OPTION.h"#include "log.h"tinyLog * tinyLog::log = NULL;locker tinyLog::llock;tinyLog::tinyLog(){}tinyLog::~tinyLog(){}/* * get the pointer to the only instance of tinyLog * use double check to assure only one instance is created */tinyLog *tinyLog::GetInstance(){if(NULL == log){//double checkllock.lock();if(NULL == log){log = new tinyLog();}llock.unlock();}return log;}/* * Unified handling of the log of tinyJSE */void tinyLog::WriteLog(const char *FORMAT,…){va_list args;va_start(args, FORMAT);llock.lock();vfprintf(stdout,FORMAT,args);llock.unlock();va_end(args);}使用该单例：#define PRINT(FORMAT,args…)tinyLog::GetInstance()->WriteLog(FORMAT,##args)
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