24 UsageEnvironment使用环境抽象基类——Live555源码阅读(三)UsageEnvironment

24 UsageEnvironment使用环境抽象基类——Live555源码阅读(三)UsageEnvironment

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简介

UsageEnvironment

live555sourcecontrol\UsageEnvironment\include\UsageEnvironment.hh

liveMediaPriv

groupsockPriv

Groupsock

LiveMedia

fScheduler

下面是其定义

// An abstract base class, subclassed for each use of the library
// 一个抽象类，子类为每个使用库
class UsageEnvironment {
public:

//reclaim   vt.开拓，开垦; 感化; 取回; 沙化; n.改造，感化; 教化; 回收再利用; 收回，取回;
//自我回收，如果liveMediaPriv或groupsockPriv这两个成员变量有一个为NULL，就delete this;
void reclaim();

// task scheduler:任务调度
//直接返回对象内部的fScheduler成员
TaskScheduler& taskScheduler() const { return fScheduler; }

// result message handling:
//消息处理结果，注意这里是一个类型定义
typedef char const* MsgString;
//纯虚接口，看意思应该是获取消息处理结果
virtual MsgString getResultMsg() const = 0;

virtual void setResultMsg(MsgString msg) = 0;
virtual void setResultMsg(MsgString msg1, MsgString msg2) = 0;
virtual void setResultMsg(MsgString msg1, MsgString msg2, MsgString msg3) = 0;
virtual void setResultErrMsg(MsgString msg, int err = 0) = 0;
// like setResultMsg(), except that an 'errno' message is appended.  (If "err == 0", the "getErrno()" code is used instead.)
//类似setResultMsg()，除了“errno”的消息被追加。（如果“err== 0”，“getErrno()”代码是用于替代。）

virtual void appendToResultMsg(MsgString msg) = 0;

virtual void reportBackgroundError() = 0;
// used to report a (previously set) error message within
//用于报告错误消息（预先设定）内的
// a background event事件的背景

virtual void internalError(); // used to 'handle' a 'should not occur'-type error condition within the library.

// 'errno'
virtual int getErrno() const = 0;

// 'console' output:
virtual UsageEnvironment& operator<<(char const* str) = 0;
virtual UsageEnvironment& operator<<(int i) = 0;
virtual UsageEnvironment& operator<<(unsigned u) = 0;
virtual UsageEnvironment& operator<<(double d) = 0;
virtual UsageEnvironment& operator<<(void* p) = 0;

// a pointer to additional, optional, client-specific state
// 客户端特定的状态
void* liveMediaPriv;
void* groupsockPriv;

protected:
//初始化liveMediaPriv(NULL), groupsockPriv(NULL), fScheduler(scheduler)
UsageEnvironment(TaskScheduler& scheduler); // abstract base class
virtual ~UsageEnvironment(); // we are deleted only by reclaim()我们只有reclaim()删除

private:
TaskScheduler& fScheduler;
};

UsageEnvironment的构造与析构

UsageEnvironment::UsageEnvironment(TaskScheduler& scheduler)
: liveMediaPriv(NULL), groupsockPriv(NULL), fScheduler(scheduler) {
}

UsageEnvironment::~UsageEnvironment() {
}

reclaim方法(自我回收)

void UsageEnvironment::reclaim() {
// We delete ourselves only if we have no remainining state:
//我们回收自己，仅当我们有一个删除遗留的状态：
if (liveMediaPriv == NULL && groupsockPriv == NULL) delete this;
}

internalError方法(内部错误)

// By default, we handle 'should not occur'-type library errors by calling abort().  Subclasses can redefine this, if desired.
void UsageEnvironment::internalError() {
abort();
}