live555 源码分析
最近由于项目需要，自己开始阅读live555的源码，下面是一些总结，希望和大家多多交流。
这次项目
1.live555 开发库源代码包括6个部分:UsageEnviroment、BasicUsageEnviroment、groupsock、liveMedia、testProgs、mediaServer
1)UsageEnviroment
UsageEnviroment目录中，声明一些虚类 class UsageEnviroment class HashTable class TaskScheduler
这些类中包括各种纯虚函数，这些虚函数定义出这些类的整体轮廓。这些类的某些子类，如果想要实例化的，必须描绘出这些轮廓。即实现这些函数。
class UsageEnviroment 是程序运行环境的抽象描述，通过包含TaskScheduler& fScheduler 的私有变量，表示网络功能、异步事件处理等。
class TaskScheduler 是定义如何设置RTSPServer端的网络功能、异步事件处理。
class HashTable 是定义类似于字典的功能。(key,value)。
注: virtual 关键字修饰的虚函数，同时不包括实现部分的函数，成为纯虚函数。带有纯虚函数的类是无法实例化的。
2)BasicUsageEnviroment
BasicUsageEnviroment目录中，主要是对UsageEnviroment目录中的class UsageEnviroment 、class TaskScheduler 各个部分的逐步实现，在实现的过程中逐步引入相应的成员数据。
3)groupsock
groupsock目录，主要是对基本的socket封装，在liveMedia目录中，涉及网络的部分会有使用。
这部分，我现在并没有太多关注。
4)liveMedia
liveMeida目录，是整个live555开发库的核心部分。
(1)class Medim，class _Tables，class MediaLookupTable
class Medim，class _Tables在Media.hh文件中定义。在 Media.cpp文件中实现。class MediaLookupTable在 Media.cpp文件中定义和实现。
liveMeida目录中最基础的类是class Medium。liveMedia目录下，很多class类型都是class Media 的子类。
class _Tables，class MediaLookupTable主要是实现对Medium的管理。
#define mediumNameMaxLen 30
class Medium {
public:
static Boolean lookupByName(UsageEnvironment& env,
char const* mediumName,
Medium*& resultMedium); //通过env.liveMediaPriv.mediaTable 这样一个MediaLookupTable里面的lookup方法查找Medium
static void close(UsageEnvironment& env, char const* mediumName); //关闭特定的env中，特定的Medium，释放相关的内存
static void close(Medium* medium); // alternative close() method using ptrs
// (has no effect if medium == NULL)
UsageEnvironment& envir() const {return fEnviron;}
char const* name() const {return fMediumName;}
// Test for specific types of media:
virtual Boolean isSource() const;
virtual Boolean isSink() const;
virtual Boolean isRTCPInstance() const;
virtual Boolean isRTSPClient() const;
virtual Boolean isRTSPServer() const;
virtual Boolean isMediaSession() const;
virtual Boolean isServerMediaSession() const;
virtual Boolean isDarwinInjector() const;
protected:
Medium(UsageEnvironment& env); // abstract base class
virtual ~Medium(); // instances are deleted using close() only
TaskToken& nextTask() {
return fNextTask;
}
private:
friend class MediaLookupTable;
UsageEnvironment& fEnviron; // Medium 属于的UsageEnviroment，在创建Meium实例的时候，赋值。
char fMediumName[mediumNameMaxLen]; // Medium 的名称，例如：liveMedium0/1/2....
TaskToken fNextTask; // void* 与Medium相关的TaskToken，
};
上面是class Medium的定义。
class Medium 某种媒体
class _Tables 查找表，包括void *mediaTable，class MediaLookupTable 类型；void* socketTable，具体类型我现在没有找到。
class MedaLookupTable 通过HashTabel实现的Medium的查找表，包括所有在UsageEnviroment 中创建的Medium实体。
上面三种类型是通过class UsageEnviroment类型中的void *liveMediaPriv 成员变量联系起来。
其中liveMediaPriv实际上是_Tables* 类型，而在_Tables类型中有void *mediaTable成员变量,mediaTable是MediaLookupTable*类型的。
如果我们知道UsageEnviroment& env，给出key值，即Medium的名称，我们就可以查找相关的Medium。
2)class RTSPServer, class RTSPServer::class RTSPClientSession
class RTSPServer，是class Medium 的子类，是对RTSPServer的抽象描述。
RTSPServer主要功能包括
[ 1 ] RTSPServer可以接收客户端TCP连接请求。在接收客户端TCP连接请求后，会创建class RTSPServer::class RTSPClientSession类。
class RTSPClientSession 是真正负责与客户端进行RTSP消息的接收、解包、打包、发送。是RTSP协议在RTSPServer端的具体实现。
接收客户端请求的Socket和端口号，在创建RTSPServer实例时，会调用
static int setUpOurSocket(UsageEnvironment& env, Port& ourPort);
创建RTSPServer端的非阻塞的监听Socket，并且调用listen，监听网络数据。
如果后续有请求消息到达，RTSPServer进行处理。
这里需要特别提出RTSPServer处理网络数据采用的是Select模型。
例如：在创建RTSPServer实例时，源代码如下：
RTSPServer::RTSPServer(UsageEnvironment& env,
int ourSocket, Port ourPort,
UserAuthenticationDatabase* authDatabase,
unsigned reclamationTestSeconds)
: Medium(env),
fRTSPServerSocket(ourSocket), fRTSPServerPort(ourPort),
fHTTPServerSocket(-1), fHTTPServerPort(0), fClientSessionsForHTTPTunneling(NULL),
fAuthDB(authDatabase), fReclamationTestSeconds(reclamationTestSeconds),
fServerMediaSessions(HashTable::create(STRING_HASH_KEYS)) {
#ifdef USE_SIGNALS
// Ignore the SIGPIPE signal, so that clients on the same host that are killed
// don't also kill us:
signal(SIGPIPE, SIG_IGN);
#endif
// Arrange to handle connections from others:
env.taskScheduler().turnOnBackgroundReadHandling(fRTSPServerSocket,
(TaskScheduler::BackgroundHandlerProc*)&incomingConnectionHandlerRTSP, this);
}
我们通过调用TaskScheduler : : turnOnBackgroundReadHandling()，开启监听SOCKET fRTSOServerSocket的READ功能，设置回调函数，以及回调函数的参数，RTSPServer* this。
static void incomingConnectionHandlerRTSP(void*, int /*mask*/); //RTSPServer接收到
TaskScheduler : : doEventLoop( )循环中
void BasicTaskScheduler0::doEventLoop(char* watchVariable) {
// Repeatedly loop, handling readble sockets and timed events:
while (1) {
if (watchVariable != NULL && *watchVariable != 0) break;
SingleStep();
}
}
会调用TaskScheduler : : SingleStep()函数，在SingleStep()函数中，我们会处理网络数据的发送和接收(select模型)、异步事件的处理、触发事件的处理。
在这里，我们会在TaskScheduler : : SingleStep()函数中调用select函数，发现监听SOCKET fRTSOServerSocket有数据需要去读。会调用：
static void incomingConnectionHandlerRTSP(void*, int /*mask*/); //RTSPServer接收到
调用accept()函数，创建RTSPServer端，与特定的Client通信的SOCKET，获取Client的地址。之后实例化class RTSPServer::class RTSPClientSession。
RTSPServer::RTSPClientSession
::RTSPClientSession(RTSPServer& ourServer, unsigned sessionId, int clientSocket, struct sockaddr_in clientAddr)
: fOurServer(ourServer), fOurSessionId(sessionId),
fOurServerMediaSession(NULL),
fClientInputSocket(clientSocket), fClientOutputSocket(clientSocket), fClientAddr(clientAddr),
fSessionCookie(NULL), fLivenessCheckTask(NULL),
fIsMulticast(False), fSessionIsActive(True), fStreamAfterSETUP(False),
fTCPStreamIdCount(0), fNumStreamStates(0), fStreamStates(NULL) {
// Arrange to handle incoming requests:
resetRequestBuffer();
envir().taskScheduler().turnOnBackgroundReadHandling(fClientInputSocket,
(TaskScheduler::BackgroundHandlerProc*)&incomingRequestHandler, this); //打开int fClientInputSocket的READ功能，接收Client的RTSP消息，设置处理函数。
noteLiveness();
}
赋值：
int fRTSPServerSocket; //接收客户端TCP连接请求的SOCKET Port fRTSPServerPort; //接收客户端TCP请求的端口
[ 2 ] 增加，查找，删除RTSPServer 支持的ServerMediaSession集合。
void addServerMediaSession(ServerMediaSession* serverMediaSession); virtual ServerMediaSession* lookupServerMediaSession(char const* streamName); void removeServerMediaSession(ServerMediaSession* serverMediaSession); void removeServerMediaSession(char const* streamName);
ServerMediaSession集合的相关数据保存在HashTable中，在创建RTSPServer时，new HashTable：
HashTable* fServerMediaSessions; //服务器端ServerMediaSession的查找表,(Medium名称，指向ServerMediaSession的地址)
[ 3 ] 用户验证。
UserAuthenticationDatabase* fAuthDB
[ 4 ] TCP打洞。
RTSPServer.hh源文件：
#define RTSP_BUFFER_SIZE 10000 // for incoming requests, and outgoing responses
class RTSPServer: public Medium {
public:
static RTSPServer* createNew(UsageEnvironment& env, Port ourPort = 554,
UserAuthenticationDatabase* authDatabase = NULL,
unsigned reclamationTestSeconds = 65);
// If ourPort.num() == 0, we'll choose the port number
// Note: The caller is responsible for reclaiming "authDatabase"
// If "reclamationTestSeconds" > 0, then the "RTSPClientSession" state for
// each client will get reclaimed (and the corresponding RTP stream(s)
// torn down) if no RTSP commands - or RTCP "RR" packets - from the
// client are received in at least "reclamationTestSeconds" seconds.
static Boolean lookupByName(UsageEnvironment& env, char const* name,
RTSPServer*& resultServer);
void addServerMediaSession(ServerMediaSession* serverMediaSession);
virtual ServerMediaSession* lookupServerMediaSession(char const* streamName);
void removeServerMediaSession(ServerMediaSession* serverMediaSession);
void removeServerMediaSession(char const* streamName);
char* rtspURL(ServerMediaSession const* serverMediaSession, int clientSocket = -1) const;
// returns a "rtsp://" URL that could be used to access the
// specified session (which must already have been added to
// us using "addServerMediaSession()".
// This string is dynamically allocated; caller should delete[]
// (If "clientSocket" is non-negative, then it is used (by calling "getsockname()") to determine
// the IP address to be used in the URL.)
char* rtspURLPrefix(int clientSocket = -1) const;
// like "rtspURL()", except that it returns just the common prefix used by
// each session's "rtsp://" URL.
// This string is dynamically allocated; caller should delete[]
UserAuthenticationDatabase* setAuthenticationDatabase(UserAuthenticationDatabase* newDB);
// Changes the server's authentication database to "newDB", returning a pointer to the old database (if there was one).
// "newDB" may be NULL (you can use this to disable authentication at runtime, if desired).
Boolean setUpTunnelingOverHTTP(Port httpPort);
// (Attempts to) enable RTSP-over-HTTP tunneling on the specified port.
// Returns True iff the specified port can be used in this way (i.e., it's not already being used for a separate HTTP server).
// Note: RTSP-over-HTTP tunneling is described in http://developer.apple.com/quicktime/icefloe/dispatch028.html
portNumBits httpServerPortNum() const; // in host byte order. (Returns 0 if not present.)
protected:
RTSPServer(UsageEnvironment& env,
int ourSocket, Port ourPort,
UserAuthenticationDatabase* authDatabase,
unsigned reclamationTestSeconds);
// called only by createNew();
virtual ~RTSPServer();
static int setUpOurSocket(UsageEnvironment& env, Port& ourPort);
virtual Boolean specialClientAccessCheck(int clientSocket, struct sockaddr_in& clientAddr,
char const* urlSuffix);
// a hook that allows subclassed servers to do server-specific access checking
// on each client (e.g., based on client IP address), without using
// digest authentication.
private: // redefined virtual functions
virtual Boolean isRTSPServer() const;
protected:
// The state of each individual session handled by a RTSP server:
class RTSPClientSession {
public:
RTSPClientSession(RTSPServer& ourServer, unsigned sessionId,
int clientSocket, struct sockaddr_in clientAddr);
virtual ~RTSPClientSession();
protected:
// Make the handler functions for each command virtual, to allow subclasses to redefine them:
virtual void handleCmd_bad(char const* cseq);
virtual void handleCmd_notSupported(char const* cseq);
virtual void handleCmd_notFound(char const* cseq);
virtual void handleCmd_unsupportedTransport(char const* cseq);
virtual void handleCmd_OPTIONS(char const* cseq);
virtual void handleCmd_DESCRIBE(char const* cseq, char const* urlSuffix,
char const* fullRequestStr);
virtual void handleCmd_SETUP(char const* cseq,
char const* urlPreSuffix, char const* urlSuffix,
char const* fullRequestStr);
virtual void handleCmd_withinSession(char const* cmdName,
char const* urlPreSuffix, char const* urlSuffix,
char const* cseq, char const* fullRequestStr);
virtual void handleCmd_TEARDOWN(ServerMediaSubsession* subsession,
char const* cseq);
virtual void handleCmd_PLAY(ServerMediaSubsession* subsession,
char const* cseq, char const* fullRequestStr);
virtual void handleCmd_PAUSE(ServerMediaSubsession* subsession,
char const* cseq);
virtual void handleCmd_GET_PARAMETER(ServerMediaSubsession* subsession,
char const* cseq, char const* fullRequestStr);
virtual void handleCmd_SET_PARAMETER(ServerMediaSubsession* subsession,
char const* cseq, char const* fullRequestStr);
// Support for optional RTSP-over-HTTP tunneling:
virtual Boolean parseHTTPRequestString(char* resultCmdName, unsigned resultCmdNameMaxSize,
char* urlSuffix, unsigned urlSuffixMaxSize,
char* sessionCookie, unsigned sessionCookieMaxSize,
char* acceptStr, unsigned acceptStrMaxSize);
virtual void handleHTTPCmd_notSupported();
virtual void handleHTTPCmd_notFound();
virtual void handleHTTPCmd_TunnelingGET(char const* sessionCookie);
virtual Boolean handleHTTPCmd_TunnelingPOST(char const* sessionCookie, unsigned char const* extraData, unsigned extraDataSize);
virtual void handleHTTPCmd_StreamingGET(char const* urlSuffix, char const* fullRequestStr);
protected:
UsageEnvironment& envir() { return fOurServer.envir(); }
void reclaimStreamStates();
void resetRequestBuffer();
Boolean authenticationOK(char const* cmdName, char const* cseq,
char const* urlSuffix,
char const* fullRequestStr);
Boolean isMulticast() const { return fIsMulticast; }
static void incomingRequestHandler(void*, int /*mask*/);
void incomingRequestHandler1();
static void handleAlternativeRequestByte(void*, u_int8_t requestByte);
void handleAlternativeRequestByte1(u_int8_t requestByte);
void handleRequestBytes(int newBytesRead);
void noteLiveness();
static void noteClientLiveness(RTSPClientSession* clientSession);
static void livenessTimeoutTask(RTSPClientSession* clientSession);
void changeClientInputSocket(int newSocketNum, unsigned char const* extraData, unsigned extraDataSize);
protected:
RTSPServer& fOurServer;
unsigned fOurSessionId;
ServerMediaSession* fOurServerMediaSession;
int fClientInputSocket, fClientOutputSocket;
struct sockaddr_in fClientAddr;
char* fSessionCookie; // used for optional RTSP-over-HTTP tunneling
TaskToken fLivenessCheckTask;
unsigned char fRequestBuffer[RTSP_BUFFER_SIZE];
unsigned fRequestBytesAlreadySeen, fRequestBufferBytesLeft;
unsigned char* fLastCRLF;
unsigned fBase64RemainderCount; // used for optional RTSP-over-HTTP tunneling (possible values: 0,1,2,3)
unsigned char fResponseBuffer[RTSP_BUFFER_SIZE];
Boolean fIsMulticast, fSessionIsActive, fStreamAfterSETUP;
Authenticator fCurrentAuthenticator; // used if access control is needed
unsigned char fTCPStreamIdCount; // used for (optional) RTP/TCP
unsigned fNumStreamStates;
struct streamState {
ServerMediaSubsession* subsession;
void* streamToken;
} * fStreamStates;
};
// If you subclass "RTSPClientSession", then you should also redefine this virtual function in order
// to create new objects of your subclass:
virtual RTSPClientSession*
createNewClientSession(unsigned sessionId, int clientSocket, struct sockaddr_in clientAddr);
// An iterator over our "ServerMediaSession" objects:
class ServerMediaSessionIterator {
public:
ServerMediaSessionIterator(RTSPServer& server);
virtual ~ServerMediaSessionIterator();
ServerMediaSession* next();
private:
HashTable::Iterator *fOurIterator;
ServerMediaSession* fNextPtr;
};
private:
static void incomingConnectionHandlerRTSP(void*, int /*mask*/); //RTSPServer接收到请求
void incomingConnectionHandlerRTSP1();
static void incomingConnectionHandlerHTTP(void*, int /*mask*/);
void incomingConnectionHandlerHTTP1();
void incomingConnectionHandler(int serverSocket);
private:
friend class RTSPClientSession;
friend class ServerMediaSessionIterator;
int fRTSPServerSocket; //接收客户端TCP连接请求的SOCKET
Port fRTSPServerPort; //接收客户端TCP请求的端口
int fHTTPServerSocket; // for optional RTSP-over-HTTP tunneling
Port fHTTPServerPort; // ditto
HashTable* fClientSessionsForHTTPTunneling; // ditto (maps 'session cookie' strings to "RTSPClientSession"s)
UserAuthenticationDatabase* fAuthDB; //用户验证
unsigned fReclamationTestSeconds;
HashTable* fServerMediaSessions; //服务器端ServerMediaSession的查找表,(Medium名称，指向ServerMediaSession的地址)
};
class RTSPServer::class RTSPClientSession是对RTSP协议在Server端的描述。主要功能是：
接收客户端RTSP的Request 消息、解析RTSP Request消息、封装Server端的RTSP Reply消息、发送Server端的RTSP Reply消息。
static void incomingRequestHandler(void*, int /*mask*/); //class RTSPServer::class RTSPClientSession的整体工作流程。