在Darwin的架构中一个很重要的概念就是模块（Module），我们在原生Darwin系统上加入了两个模块（Module），是MyBCInteractModule和MyFileUploadModule，每个模块都要提供两个函数，Main和dispatch函数，服务器启动时（QTSServer）会调用Main函数完成对该模块的初始化；Dispatch是注册给服务器的一个回调函数，服务器通过该函数分发该模块订阅的各种角色，这些角色定义如下：
/********************************************************************/
// QTSS API ROLES
//
// Each role represents a unique situation in which a module may be
// invoked. Modules must specify which roles they want to be invoked for.
enum
{
//Global
QTSS_Register_Role = FOUR_CHARS_TO_INT('r', 'e', 'g', ' '), //reg //All modules get this once at startup
QTSS_Initialize_Role = FOUR_CHARS_TO_INT('i', 'n', 'i', 't'), //init //Gets called once, later on in the startup process
QTSS_Shutdown_Role = FOUR_CHARS_TO_INT('s', 'h', 'u', 't'), //shut //Gets called once at shutdown
QTSS_ErrorLog_Role = FOUR_CHARS_TO_INT('e', 'l', 'o', 'g'), //elog //This gets called when the server wants to log an error.
QTSS_RereadPrefs_Role = FOUR_CHARS_TO_INT('p', 'r', 'e', 'f'), //pref //This gets called when the server rereads preferences.
QTSS_StateChange_Role = FOUR_CHARS_TO_INT('s', 't', 'a', 't'), //stat //This gets called whenever the server changes state.
QTSS_Interval_Role = FOUR_CHARS_TO_INT('t', 'i', 'm', 'r'), //timr //This gets called whenever the module's interval timer times out calls.
//RTSP-specific
QTSS_RTSPFilter_Role = FOUR_CHARS_TO_INT('f', 'i', 'l', 't'), //filt //Filter all RTSP requests before the server parses them
QTSS_RTSPRoute_Role = FOUR_CHARS_TO_INT('r', 'o', 'u', 't'), //rout //Route all RTSP requests to the correct root folder.
QTSS_RTSPAuthenticate_Role = FOUR_CHARS_TO_INT('a', 't', 'h', 'n'), //athn //Authenticate the RTSP request username.
QTSS_RTSPAuthorize_Role = FOUR_CHARS_TO_INT('a', 'u', 't', 'h'), //auth //Authorize RTSP requests to proceed
QTSS_RTSPPreProcessor_Role = FOUR_CHARS_TO_INT('p', 'r', 'e', 'p'), //prep //Pre-process all RTSP requests before the server responds.
//Modules may opt to "steal" the request and return a client response.
QTSS_RTSPRequest_Role = FOUR_CHARS_TO_INT('r', 'e', 'q', 'u'), //requ //Process an RTSP request & send client response
QTSS_RTSPPostProcessor_Role = FOUR_CHARS_TO_INT('p', 'o', 's', 't'), //post //Post-process all RTSP requests
QTSS_RTSPSessionClosing_Role = FOUR_CHARS_TO_INT('s', 'e', 's', 'c'), //sesc //RTSP session is going away
QTSS_RTSPIncomingData_Role = FOUR_CHARS_TO_INT('i', 'c', 'm', 'd'), //icmd //Incoming interleaved RTP data on this RTSP connection
//RTP-specific
QTSS_RTPSendPackets_Role = FOUR_CHARS_TO_INT('s', 'e', 'n', 'd'), //send //Send RTP packets to the client
QTSS_ClientSessionClosing_Role = FOUR_CHARS_TO_INT('d', 'e', 's', 's'), //dess //Client session is going away
//RTCP-specific
QTSS_RTCPProcess_Role = FOUR_CHARS_TO_INT('r', 't', 'c', 'p'), //rtcp //Process all RTCP packets sent to the server
//File system roles
QTSS_OpenFilePreProcess_Role = FOUR_CHARS_TO_INT('o', 'p', 'p', 'r'), //oppr
QTSS_OpenFile_Role = FOUR_CHARS_TO_INT('o', 'p', 'f', 'l'), //opfl
QTSS_AdviseFile_Role = FOUR_CHARS_TO_INT('a', 'd', 'f', 'l'), //adfl
QTSS_ReadFile_Role = FOUR_CHARS_TO_INT('r', 'd', 'f', 'l'), //rdfl
QTSS_CloseFile_Role = FOUR_CHARS_TO_INT('c', 'l', 'f', 'l'), //clfl
QTSS_RequestEventFile_Role = FOUR_CHARS_TO_INT('r', 'e', 'f', 'l'), //refl
//HLS Session
Easy_HLSOpen_Role = FOUR_CHARS_TO_INT('h', 'l', 's', 'o'), //hlso
Easy_HLSClose_Role = FOUR_CHARS_TO_INT('h', 'l', 's', 'c'), //hlsc
};
typedef UInt32 QTSS_Role;
每个模块的main可以如下：
QTSS_Error MyBCInteractModule_Main(void* inPrivateArgs)
{
return _stublibrary_main(inPrivateArgs, MyBCInteractModuleDispatch);
}
其中MyBCInteractModuleDispatch是Dispatch函数，该函数负责对各种角色的处理，如：
QTSS_Error MyBCInteractModuleDispatch(QTSS_Role inRole, QTSS_RoleParamPtr inParams)
{
switch (inRole)
{
case QTSS_Register_Role:
return Register(&inParams->regParams);
break;
case QTSS_Initialize_Role:
return Initialize(&inParams->initParams);
break;
case QTSS_RereadPrefs_Role:
return RereadPrefs();
break;
case QTSS_RTSPAuthenticate_Role:
return AuthenticateRTSPRequest(&inParams->rtspAthnParams);
break;
case QTSS_RTSPAuthorize_Role:
return AccessAuthorizeRTSPRequest(&inParams->rtspRequestParams);
break;
case QTSS_Shutdown_Role:
return Shutdown();
break;
}
return QTSS_NoErr;
}
那么，MyBCInteractModule和!MyFileUploadModule是在什么时候注册到Darwin系统中的呢？答案是QTSServer::LoadCompiledInModules，在调用!SetupModule时传人了模块的Main函数，SetupModule时会调用该main函数，也就获取到了该模块的dispatch函数，在AddModule时，调用dispatch函数分发QTSS_Register_Role角色，此时MyBCInteractModule和MyFileUploadModule会去添加自己感兴趣的角色，最后在AddModule里把MyBCInteractModule和MyFileUploadModule添加到队列里。到此，添加模块算是完成了。
void QTSServer::LoadCompiledInModules()
{
#ifndef DSS_DYNAMIC_MODULES_ONLY
//
// The following modules are all compiled into the server.
QTSSModule* theFileModule = new QTSSModule("QTSSFileModule");
(void)theFileModule->SetupModule(&sCallbacks, &QTSSFileModule_Main);
(void)AddModule(theFileModule);
//与业务服务器通信
QTSSModule* theBCInteractModule = new QTSSModule("MyBCInteractModule");
(void)theBCInteractModule->SetupModule(&sCallbacks, &MyBCInteractModule_Main);
(void)AddModule(theBCInteractModule);
//文件上传模块
QTSSModule* theFileUploadModule = new QTSSModule("MyFileUploadModule");
(void)theFileUploadModule->SetupModule(&sCallbacks, &MyFileUploadModule_Main);
(void)AddModule(theFileUploadModule);
xxxxxx
}
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