UsageEnviroment的分析

UsageEnvironment是live555中最基本的几个基类之一，不过它的功能很简单，就是对错误的处理和输出。

在这个类里面有几个虚函数：

operator <<  用于输出信息

setResultMsg  用于设置一个内部字符串（一般用来表示错误信息的）

reportBackgroundError  用于报告错误信息。

 

在live555中是通过BasicUsageEnvrionment来继承UsageEnvironment来在控制台上输出错误消息。当然 如果你想以其他的方式输出消息，可以直接继承UsageEnvironment来实现几个纯虚函数来输出错误。

在这里我自己继承了UsageEnvironment来看一下效果：

#define MAX_STRING 256class MyUsageEnvironment:public UsageEnvironment{private:char ErroMsg[MAX_STRING];int currentLength;public:MyUsageEnvironment(TaskScheduler& task):UsageEnvironment(task),currentLength(0){}virtual MyUsageEnvironment& operator<<(const char* str);virtual MyUsageEnvironment& operator<<(double str);virtual MyUsageEnvironment& operator<<(int str);virtual MyUsageEnvironment& operator<<(unsigned u) ;virtual MyUsageEnvironment& operator<<(void* p);virtual MsgString getResultMsg () const;virtual void setResultMsg(MsgString msg);virtual void setResultMsg(MsgString msg1, MsgString msg2);virtual void appendToResultMsg(MsgString msg);virtual void setResultMsg(MsgString msg1, MsgString msg2, MsgString msg3);virtual void setResultErrMsg(MsgString msg, int err = 0);virtual void reportBackgroundError();virtual int getErrno() const;}; 

具体的实现：

#include"my_usageEnvironment.h"#include<iostream>using namespace std;MyUsageEnvironment& MyUsageEnvironment::operator<<(const char* str){cout<<str;return *this;}MyUsageEnvironment& MyUsageEnvironment::operator<<(double d){cout<<d;return *this;}MyUsageEnvironment& MyUsageEnvironment::operator<<(int i){cout<<i;return *this;}MyUsageEnvironment& MyUsageEnvironment::operator<<(unsigned u){cout<<u;return *this;}MyUsageEnvironment& MyUsageEnvironment::operator<<(void *p){fprintf(stderr,"%p",p);return *this;}MyUsageEnvironment::MsgString MyUsageEnvironment::getResultMsg() const{return this->ErroMsg;}void MyUsageEnvironment::appendToResultMsg(MsgString msg){int len=this->currentLength;currentLength+=strlen(msg);if(currentLength>=MAX_STRING){currentLength-=strlen(msg);return ;}strcpy(this->ErroMsg+len,msg);return ;}void MyUsageEnvironment::setResultMsg(MyUsageEnvironment::MsgString msg){currentLength=strlen(msg);if(currentLength>=MAX_STRING){currentLength-=strlen(msg);return ;}strcpy(this->ErroMsg,msg);return ;}void MyUsageEnvironment::setResultMsg(MyUsageEnvironment::MsgString msg1,MyUsageEnvironment::MsgString msg2){this->setResultMsg(msg1);this->appendToResultMsg(msg2);}void MyUsageEnvironment::setResultMsg(MyUsageEnvironment::MsgString msg1,MyUsageEnvironment::MsgString msg2,MyUsageEnvironment::MsgString msg3){this->setResultMsg(msg1);this->appendToResultMsg(msg2);this->appendToResultMsg(msg3);}void MyUsageEnvironment::setResultErrMsg(MsgString msg, int err){this->setResultMsg(msg);}void MyUsageEnvironment::reportBackgroundError(){cout<<this->ErroMsg<<endl;}int MyUsageEnvironment::getErrno() const{return GetLastError();} 

BasicUsageEnvironment功能只是相当于错误管理，所以其实现很简单，不过如果想你重定向输出信息那么只要重写以上函数就可以了。

但是跟BasicUsageEnvironment地位一致的另一个基类BasicTaskScheduler就没这么简单了，它负责任务调度，里面包含了一些算法和数据结构，今天只是简单的看了下觉得貌似挺负债的，后面几天争取把这个基类过程搞清楚。