Darwin 5.5.5 代码分析文档
DarwinStreamServer 是苹果公司开发的流媒体视频服务器。我们分析的代码基于版
本5.5.5。
一、DSS启动、初始化流程
我们从Server.tproj/main.cpp入手，分析DSS加载module及和module交互的流程。
（1）、DSS在fork子进程后调用StartServer启动服务
调用OS、OSThread、Socket、SocketUtils、QTSSDictionaryMap、
QTSServerInterface、QTSServer等类的Initialize函数进行初始化。
（2）、select_startevents函数
initialize the select() implementation of the event queue.
（3）、QTSServer::Initialize函数
继续调用QTSSModule、QTSServerPres、QTSSMessages、RTSPRequestInterface、
RTSPSessionInterface、RTPSessionInterface、RTPStream、RTSPSession、
QTSSFile、QTSSUserProfile等类的Initialize函数，进行dictionary的初始化。
加载了第一个模块QTSSErrorLogModule。
this->SetDefaultIPAddr() // set default IP addr & DNS name
// begin listening，注意这里传的是false参数。
this->CreateListeners(false,fSrvrPrefs,inPortOverride)
（4）、TaskThreadPool::AddThreads(numThreads) // numThreads为1
到这里，第一个线程创建、运行、被添加到线程池里。
在startBroadcastRTSPSession函数里，又调用AddThreads函数在线程池里添加了一个线程。
（5）、TimeoutTask::Initialize()
Start up the server's global tasks, and start listening. The timeoutTask mechanism is
task
based, we therefore must do this after adding task threads. This be done before starting
the sockets and server tasks.
sThread = NEW TimeoutTaskThread();
sThread->signal(Task::kStartEvent);
创建一个TimeoutTaskThread类对象，实际上这个类的名字容易产生混淆，它并不是一个线程类，而
是一个基于Task类的任务类。
因为前面已经在线程池里添加了一个任务线程，所以在这里调用signal的时候，就会找到这个线程，
并把事件加入到这个线程的任务队列里，等待被处理。(这时，刚才创建的线程应该也在
TaskThread::Entry函数里等待事件的发生)
（6）、IdleTask::Initialize()
// 创建并启动空闲任务线程
sIdleThread = NEW IdleTaskThread(); sIdleThread->Start();
（7）、Socket::StartThread()
// 启动Socket类的sEventThread类所对应的线程。sEventThread类在Socket::Initialize函数里创建
// 到目前为止，这已是第三个启动的线程，分别是任务线程、空闲任务线程、事务线程。
（8）、OSThread::Sleep(1000)
这里的Sleep是调用usleep来实现，为什么这里要睡眠1s？？？是为了等待线程的启动？？？
（9）、sServer->InitModules(inInitialState)
初始化并加载一些模块。共加载了QTSSHomeDirectoryModule、QTSSRefMovieModule、
QTSSFileModule、QTSSReflectorModule、
QTSSRelayModule、QTSSAccessLogModule、QTSSFlowControlModule、QTSSPosixFileSysModule、
QTSSAdminModule、QTSSMP3StreamingModule、QTSSAccessModule这些模块。
fSrvrPrefs = new QTSServerPrefs(sPrefsSource, true); ... ...
fSrvrM7essages = new QTSSMessages(sMessagesSource);
QTSSModuleUtils::Initialize(fSrvrMessages, this, QTSServerInterface::GetErrorLogStream());
... ...
Add Reread Preferences Service.
// 对于那些支持initial role的模块，通过它们的CallDispatch函数来调用具体的initial函数。
this->DoInitRole();
（10）、sServer->StartTasks()
创建RTCPTask、RTPStatsUpdaterTask
Start listening，因为TCPListenerSocket是EventContext的继承类，所以这里实际上调用的是
EventContext::RequestEvent().
（11）、sServer->SetupUDPSockets()
udp sockets are set up after the rtcp task is instantiated。
针对系统的每一个ip地址，都创建并绑定一个socket端口对（分别用于RTP data发送和RTCP data接
收），并申请对这两个socket端口的监听。
注意调用CreateUDPSocketPair函数传进去的Port参数为0，所以在通过Darwin播放静态多媒体文件
时，不论是同一个媒体文件的音频、视频流还是同时播放的多个媒体文件，都是这两个socket端口
来完成RTCP、RTP数据的处理。
（12）、CleanPid(true); WritePid(!inDontFork); doneStartingUp = true;
在/var/run下写pid文件
（13）、sServer->SwitchPersonality()
switch to run user and group ID
执行setgid、setuid函数
（14）、RunServer()
由一个大循环构成：
while((theServerState != qtssShuttingDownState) && (theServerState !=
qtssFatalErrorState))
{
OSThread::Sleep(1000);
if(sStatusUpdateInterval) // 周期性更新状态，当带有-D参数时，为3。
{
通过PrintHeader打印标题行
RTP-Conns RTSP-Conns HTTP-Conns kBits/Sec Pkts/Sec RTP-Playing AvgDelay CurMaxDelay MaxDelay AvgQuality NumThinned Time
RTP-Conns RTSP-Conns HTTP-Conns kBits/Sec Pkts/Sec TotConn TotBytes TotPktsLost Time
通过DebugLevel_1、PrintStatus打印每字段的值。
每个字段对应的变量分别为：
RTP-Conns: fNumRTPSessions;
RTSP-Conns: fNumRTPSessions;
HTTP-Conns: fNumRTSPHTTPSessions;
kBits/Sec: fCurrentRTPBandwidthInBits;
Pkts/Sec: fRTPPacketsPerSecond;
RTP-Playing: fNumRTPPlayingSessions;
// sLastDebugPacket即为上次的fTotalRTPPackets。
AvgDelay: fTotalLate/(fTotalRTPPackets – sLastDebugPackets)
CurMaxDelay: fCurrentMaxLate;
MaxDelay: fMaxLate;
// sLastDebugTotalQuality即为上次的fTotalQuality。
AvgQuality: (fTotalQuality-sLastDebugTotalQuality)/(fTotalRTPPackets–sLastDebugPackets)
NumThinned: fNumThinned;
TotConn: fTotalRTPSessions;
TotBytes: fTotalRTPBytes;
TotPktsLost: fTotalRTPPacketsLost
如果接收到SigInt或者SigTerm，则终止sServer。
}
二、几大部分
（一）、模块
? DSS 利用模块来响应请求和处理任务。DSS 的模块分为三种类型：
（1）、Content-Managing Modules
The content-managing modules manage RTSP requests and responses related to media sources, such as a file
or a broadcast. Each module is responsible for interpreting the client's request, reading and parsing their
supported files or network source, and responding with RTSP and RTP. In some cases, such as the mp3 streaming
module, the module uses HTTP.
The content-managing modules are QTSSFileModule, QTSSReflectorModule, QTSSRelayModule,
and QTSSMP3StreamingModule.
（2）、Server-Support Modules
The server-support modules performserver data gathering and logging functions. The server- support
modules are QTSSErrorLogModule, QTSSAccessLogModule, QTSSWebStatsModule,
QTSSWebDebugModule, QTSSAdminModule, and QTSSPOSIXFileSystemModule.
（3）、Access Control Modules
The access control modules provide authentication and authorization functions as well as URL path
manipulation.
The access control modules are QTSSAccessModule, QTSSHomeDirectoryModule, QTSSHttpFileModule,
and QTSSSpamDefenseModule.
? 几个相关类的定义
一、QTSSModule类
各个Module类均以QTSSModule类为基类。
（1）、构建函数
QTSSModule::QTSSModule(char* inName, char* inPath)
:
QTSSDictionary(QTSSDictionaryMap::GetMap(QTSSDictionaryMap::kModuleDictIndex)), ... ...
{
如果模块以库文件的形式保存在disk上，利用OSCodeFragment类来处理
另外，QTSSModule本身是QTSSDictionary的继承类，它还有一个QTSSDictionary类对象的指
针成员
调用SetVal、SetValue进行一些属性的设置
}
? 模块加载过程
一、以加载QTSSErrorLogModule为例
在创建一个QTSSModule类对象后，调用该类的SetupModule成员函数，并调用AddModule函数和调用
QTSServer的BuildModuleRoleArrays函数。
注意：DSS还提供了一个OSCodeFragment类，来处理以库文件的形式保存在disk的模块。
（1）SetupModule成员函数
传给SetupModule成员函数的两个形参分别是QTSS_CallbacksPtr（函数指针）、
QTSS_MainEntryPointPtr（具体模块的进入函数指针，对于QTSSErrorLogModule类，这个函数是
QTSSErrorLogModule_Main）
调用QTSSErrorLogModule_Main
_stublibrary_main(inPrivateArgs, QTSSErrorLogModuleDispatch)
sCallbacks = theArgs->inCallbacks;
sErrorLogStream = theArgs->inErrorLogStream;
// Send requested information back to the server
theArgs->outStubLibraryVersion = QTSS_API_VERSION;
theArgs->outDispatchFunction = inDispatchFunc;
注：这里的sCallbacks、sErrorLogStream 分别是在QTSS_Private.cpp 里定义的静
态全局量。theArgs->inCallbacks 为SetupModule 的实参（即QTSServer 类的
sCallbacks 成员），而inDispatchFunc 为具体模块传进来的实参
QTSSErrorLogModuleDispatch。
将fDispatchFunc设置为thePrivateArgs.outDispatchFunction，fDispatchFunc为QTSSModule的私有
类成员。这样DSS可以通过具体模块的基类QTSSModule的这个私有成员来让具体模块进行分发处理。
调用QTSServerInterface::LogError函数进行log功能。
（2）AddModule函数
传给AddModule函数的实参为要加载的具体模块。
Prepare to invoke the module's Register role. Setup the Register param block
QTSS_ModuleState theModuleState;
theModuleState.curModule = inModule;
theModuleState.curRole = QTSS_Register_Role;
theModuleState.curTask = NULL;
OSThread::SetMainThreadData(&theModuleState);
inModule->CallDispatch(QTSS_Register_Role, &theRegParams)；
(fDispatchFunc)(inRole, inParams);
对于QTSSErrorLogModule 模块即为QTSSErrorLogModuleDispatch 函数，该函数根据不同的
Role 调用模块具体的处理函数，对于QTSS_Register_Role 调用Register 函数。Register 函
数通过调用QTSS_AddRole 来告知DSS 模块支持的Role。
// Update the module name to reflect what was returned from the register role
inModule->SetValue(qtssModName, 0, theRegParams.regParams.outModuleName,
::strlen(theRegParams.regParams.outModuleName), false);
// Give the module object a prefs dictionary. Instance attributes are allowed for these
objects.
QTSSPrefs* thePrefs = NEW QTSSPrefs( sPrefsSource, inModule->GetValue(qtssModName),
QTSSDictionaryMap::GetMap(QTSSDictionaryMap::kModulePrefsDictIndex), true);
thePrefs->RereadPreferences();
inModule->SetPrefsDict(thePrefs);
// Add this module to the array of module (dictionaries)
UInt32 theNumModules = this->GetNumValues(qtssSvrModuleObjects);
QTSS_Error theErr = this->SetValue(qtssSvrModuleObjects, theNumModules, &inModule,
sizeof(QTSSModule*), QTSSDictionary::kDontObeyReadOnly);
// Add this module to the module queue
sModuleQueue.EnQueue(inModule->GetQueueElem());
（3）BuildModuleRoleArrays函数
根据QTSSModule的fRoleArray数组的Role支持情况，在QTSServerInterface::sNumModulesInRole里做
记录，并在sModuleArray数组里保存相关Role的所有QTSSModule指针。
这样，QTSServer就可以知道目前有哪些模块支持哪些Role。
到此，一个Module已经添加到QTSServer里。
二、以加载QTSSReflectorModule为例
在创建一个QTSSModule类对象后，调用该类的SetupModule成员函数，并调用AddModule函数和调用
QTSServer的BuildModuleRoleArrays函数。
QTSSModule* theReflectorModule = new QTSSModule("QTSSReflectorModule");
(void)theReflectorModule->SetupModule(&sCallbacks, &QTSSReflectorModule_Main);
调用QTSSReflectorModule_Main函数，
将fDispatchFunc设置为
thePrivateArgs.outDispatchFunction(QTSSReflectorModuleDispatch)，fDispatchFunc为
QTSSModule的私有类成员。这样DSS可以通过具体模块的基类QTSSModule的这个私有成员来
让具体模块进行分发处理。
调用QTSServerInterface::LogError函数进行log功能
for(UInt32 x=0;x<QTSServerInterface::GetNumModulesInRole(QTSSModule::kErrorLogRole); x++)
QTSServerInterface::GetModule(QTSSModule::kErrorLogRole,x)-
>CallDispatch(QTSS_ErrorLog_Role,&theParams);
// 因为只有QTSSErrorLogModule注册kErrorLogRole，实际上会调用这个类的
// LogError函数。
If this is a fatal error, 调用SetValue set the proper attribute in the
RTSPServer dictionary。
(void)AddModule(theReflectorModule);
后面同上面所说的QTSSErrorLogModule加载情况。
? 一些模块的介绍
一、QTSSRTPFileModule
Content source module that uses the QTFileLib to serve Hinted QuickTime files to clients.
支持TSS_Initialize_Role、QTSS_RTSPPreProcessor_Role、QTSS_ClientSessionClosing_Role、
QTSS_RereadPrefs_Role。Dispatch函数里也提供了QTSS_RTPSendPackets_Role的处理，直接通过模块
来调用这个Role的处理。
在initialize函数里，通过SetupSupportedMethods登记支持的方法：DESCRIBE, SETUP, PLAY, PAUSE,
and TEARDOWN。
！！这个模块并没有被加载！！
（1）、ProcessRTSPRequest
QTSS_RTSPPreProcessor_Role的处理函数。
根据请求内容，分别做出处理：
Describe: DoDescribe(inParams);
Setup: DoSetup(inParams);
Play: DoPlay(inParams);
Teardown: // Tell the server that this session should be killed, and send a TEARDOWN response
QTSS_Teardown(...); QTSS_SendStandardRTSPResponse();
Pause: QTSS_Pause(); QTSS_SendStandardRTSPResponse();
（2）、DoDescribe
Check and see if this is a request we should handle. We handle all requests with URLs
that end in a '.rtp'
Get the FileSession for this DESCRIBE, if any.
if(theFile != NULL)
{
// There is already a file for this session. This can happen if there are multiple
// DESCRIBES, or a DESCRIBE has been issued with a Session ID, or some such thing.
if ( !theFullPath.Equal( *theFile->fFile.GetMoviePath() ) )
{
delete theFile; theFile = NULL;
QTSS_SetValue(inParamBlock->inClientSession, sFileSessionAttr, 0, &theFile,
sizeof(theFile));
}
}
if(theFile == NULL)
{ // 创建FileSession类对象，调用theFile->fFile.Initialize(theFullPath, 8);
CreateRTPFileSession(inParamBlock, theFullPath, &theFile);
QTSS_SetValue(inParamBlock->inClientSession, sFileSessionAttr, 0, &theFile, sizeof(theFile));
}
二、QTSSFileModule模块
Content source module that uses the QTFileLib to serve Hinted QuickTime files to clients.
注册了QTSS_Initialize_Role、QTSS_RTSPRequest_Role、QTSS_ClientSessionClosing_Role、
QTSS_RereadPrefs_Role的处理。在Dispatch函数里还添加了QTSS_RTPSendPackets_Role的处理。
在initialize函数里，通过SetupSupportedMethods登记支持的方法：DESCRIBE, SETUP, PLAY, PAUSE,
and TEARDOWN。
（1）、ProcessRTSPRequest()
QTSS_RTSPRequest_Role的处理函数。
根据请求内容，分别做出处理：
Describe: DoDescribe(inParams);
Setup: DoSetup(inParams);
Play: DoPlay(inParams);
Teardown: // Tell the server that this session should be killed, and send a TEARDOWN response
QTSS_Teardown(...); QTSS_SendStandardRTSPResponse();
Pause: QTSS_Pause(); QTSS_SendStandardRTSPResponse();
（2）、DoDescribe()
if(isSDP(inParamBlock)) // sdp file
{ ... ...
QTSS_GetValuePtr(inParamBlock->inRTSPRequest, qtssRTSPReqFilePath, 0,(void**)&pathStr.Ptr,
&pathStr.Len);
QTSSModuleUtils::SendErrorResponse(inParamBlock->inRTSPRequest,qtssClientNotFound,sNoSDPFileFoundErr,&pathStr);
... ...return err;
}
... ...
if (theFile != NULL)
{
// There is already a file for this session. This can happen if there are multiple
// DESCRIBES, or a DESCRIBE has been issued with a Session ID, or some such thing.
moviePath(theFile->fFile.GetMoviePath());
if(!requestPath.Equal(moviePath))
{
DeleteFileSession(theFile); theFile = NULL;
QTSS_SetValue(inParamBlock->inClientSession, sFileSessionAttr, 0, &theFile, sizeof(theFile));
}
}
if (theFile == NULL)
{
// 创建FileSession类对象，调用theFile->fFile.Initialize(inPath,);
// theFile->fFile为QTRTPFile类型的对象。
// 通过QTRTPFile、QTFile、QTSSFile等类对象来完成媒体文件的解析
CreateQTRTPFile(inParamBlock, thePath.GetObject(), &theFile);
QTSS_SetValue(inParamBlock->inClientSession, sFileSessionAttr, 0, &theFile,
sizeof(theFile));
}
// replace the sacred character we have trodden on in order to truncate the path.
// 文件名添加.sdp后缀
thePath.GetObject()[thePathLen – sSDPSuffix.Len] = sSDPSuffix.Ptr[0];
if (sEnableMovieFileSDP) // 在配置文件里enable_movie_file_sdp为false，为什么也能在客
// 户端的播放器里访问sdp文件？？？
{
// Check to see if there is an sdp file, if so, return that file instead of the
// built-in sdp.
QTSSModuleUtils::ReadEntireFile(thePath.GetObject(), &theSDPData);
}
后续是sdp信息的处理（这里实现什么？？？）如果配置文件中的record_movie_file_sdp为
true，则会生成一个sdp文件。
// now parse the movie media sdp data. We need to do this in order to extract payload
// information. The SDP parser object will not take responsibility of the memory (one
// exception... see above)
// 注意在前面已经调用了：
// theSDPData.Ptr = theFile->fFile.GetSDPFile(&sdpLen); theSDPData.Len = sdpLen;
// 从媒体文件里获取sdp信息。
theFile->fSDPSource.Parse(theSDPData.Ptr, theSDPData.Len);
（3）、DoSetup()
if (isSDP(inParamBlock))
{ ... ...}
QTSS_GetValue(inParamBlock->inClientSession, sFileSessionAttr, 0, (void*)&theFile,
&theLen);
if((theErr != QTSS_NoErr) || (theLen != sizeof(FileSession*)))
{ ... ...}
QTSS_GetValueAsString(inParamBlock->inRTSPRequest, qtssRTSPReqFileDigit, 0, &theDigitStr);
// 比如客户端发送一个
//“SETUP rtsp://192.168.2.163:554/sample_100kbit.mp4/trackID=3 RTSP/1.0\r\n”请求，则
// theTrackID等于3。
Uint32 theTrackID = ::strtol(theDigitStr, NULL, 10);
// 调用QTRTPFile::AddTrack
theFile->fFile.AddTrack(theTrackID, true);
// Before setting up this track, check to see if there is an If-Modified-Since date. If
// there is, and the content hasn't been modified, then just return a 304 Not Modified
这里所起的作用是什么？？？
// Find the payload for this track ID(if applicable)
根据theFile->fSDPSource的streaminfo，设置thePayload、thePayloadType、bufferDelay
// Create a new RTP stream
// 实际上是调用RTPSession::AddStream()
QTSS_AddRTPStream(inParamBlock->inClientSession, inParamBlock->inRTSPRequest, &newStream, 0);
// Set the payload type, payload name & timescale of this track
// Set the number of quality levels. Allow up to 6
调用QTSS_SetValue进行设置。
// Get the SSRC of this track
// give the file some info it needs.
根据TrackID，将对应的trackEntry->SSRC设置为上面获得的SSRC，将trackEntry->Cookie1
Cookie2分别设为newStream、thePayloadType。
theErr = QTSS_GetValuePtr(inParamBlock->inRTSPHeaders, qtssXRTPMetaInfoHeader, 0,
(void**)&theHeader.Ptr, &theHeader.Len);
if(theErr == QTSS_NoErr)
{ ... ...}
// Our array has now been updated to reflect the fields requested by the client. send the
// setup response
调用QTSS_AppendRTSPHeader
QTSS_SendStandardRTSPResponse(inParamBlock->inRTSPRequest, newStream, 0);
（4）、SetupCacheBuffers()
通过QTSS_GetValue获取playCount值。
// increments num buffers after initialization so do only once per session
// Allocate函数以及OSFileSource::ReadFromCache/ReadFromDisk函数的分析待续
if (sEnableSharedBuffers && playCount == 1)
(*theFile)->fFile.AllocateSharedBuffers(sSharedBufferUnitKSize, sSharedBufferInc,
sSharedBufferUnitSize,sSharedBufferMaxUnits);
if (sEnablePrivateBuffers) // reinitializes buffers to current location so do every
time
(*theFile)->fFile.AllocatePrivateBuffers(sSharedBufferUnitKSize, sPrivateBufferUnitSize,
sPrivateBufferMaxUnits);
playCount ++;
QTSS_SetValue(inParamBlock->inClientSession, sFileSessionPlayCountAttrID, 0, &playCount,
（5）、DoPlay()
if (isSDP(inParamBlock))
{ ... ...}
QTSS_GetValue(inParamBlock->inClientSession, sFileSessionAttr, 0, (void*)&theFile,
&theLen);
SetupCacheBuffers(inParamBlock, theFile);
调用一系列的设置工作QTSS_SetValue。。。
// Tell the server to start playing this movie. We do want it to send RTCP SRs, but we
// DON'T want it to write the RTP header
// 调用RTPSession::Play
QTSS_Play(inParamBlock->inClientSession, inParamBlock->inRTSPRequest, qtssPlayFlagsSendRTCP);
准备RTSP回复内容，并调用QTSS_SendStandardRTSPResponse
（6）、SendPackets()
QTSS_RTPSendPackets_Role的处理函数，在RTPSession::Run函数里会调用这个Role的注册函数。
theLastPacketTrack = (*theFile)->fFile.GetLastPacketTrack();
while (true) {
if ((*theFile)->fPacketStruct.packetData == NULL)
{
// 寻找要传输的包，theTransmitTime为发送时间
theTransmitTime = (*theFile)->fFile.GetNextPacket(
(char**)&(*theFile)->fPacketStruct.packetData, &(*theFile)->fNextPacketLen);
// 刚找到的
theLastPacketTrack = (*theFile)->fFile.GetLastPacketTrack();
theStream = (QTSS_Object)theLastPacketTrack->Cookie1;
// Check to see if we should stop playing now
if (((*theFile)->fStopTime !=-1) && (theTransmitTime > (*theFile)-
>fStopTime))
if (((*theFile)->fStopTrackID !=0) && ((*theFile)->fStopTrackID == theLastPacketTrack-
>TrackID)
&& (theLastPacketTrack->HTCB->fCurrentPacketNumber > (*theFile)->fStopPN))
{ // We should indeed stop playing
... ... inParams->outNextPacketTime = qtssDontCallSendPacketsAgain;
... ... return QTSS_NoErr;
}
// Find out what our play speed is. Send packets out at the specified rate,
// and do so by altering the transmit time of the packet based on the
// Speed rate.
调整theTransmitTime
}
// 如果还没有数据
if ((*theFile)->fPacketStruct.packetData == NULL)
{ inParams->outNextPacketTime = qtssDontCallSendPacketsAgain; return QTSS_NoERR; }
// 发送数据
// If the stream is video, we need to make sure that QTRTPFile knows what quality level
// we're at
设置quality level。
adjust the timestamp so it reflects paused time.
// 调用RTPStream::Write函数。RTPStream::Write返回EAGAIN时，QTSS_Write返回QTSS_WouldBlock
theErr = QTSS_Write(theStream, &(*theFile)->fPacketStruct, (*theFile)-
>fNextPacketLen,NULL,theFlags);
// 设置inParams->outNextPacketTime，RTPSession::Run函数根据outNextPacketTime，决定返回值。
if ( theErr == QTSS_WouldBlock )
{ // reset the packet time stamp so we adjust it again when we really do send it
if (currentTimeStamp != pauseTimeStamp)
SetPacketTimeStamp(currentTimeStamp, packetDataPtr);
// In the case of a QTSS_WouldBlock error, the packetTransmitTime field of the
// packet struct will be set to the time to wakeup, or -1 if not known.
// If the time to wakeup is not given by the server, just give a fixed guess interval
if ((*theFile)->fPacketStruct.suggestedWakeupTime == -1)
inParams->outNextPacketTime = sFlowControlProbeInterval;
else
inParams->outNextPacketTime=(*theFile)->fPacketStruct.suggestedWakeupTimeinParams->
inCurrentTime;
} else {
QTSS_SetValue(theStream, sRTPStreamLastSentPacketSeqNumAttrID, 0, &curSeqNum,
sizeof(curSeqNum));
(*theFile)->fPacketStruct.packetData = NULL;
}
三、QTSSPosixFileSysModule模块
支持QTSS_OpenFile_Role，实际上在该模块的Dispatch函数里同时支持QTSS_Advise_Role、
QTSS_ReadFile_Role、QTSS_CloseFile_Role、QTSS_RequestEventFile_Role的处理，这些Role是直接
通过模块来调用的。
（1）、OpenFile
// 创建OSFileSource对象，该类实现底层的文件操作。
theFileSource = NEW OSFileSource(inParams->inPath);
获取文件长度、修改时间等信息。
// Add this new file source object to the file object
QTSS_SetValue(inParams->inFileObject, sOSFileSourceAttr, 0, &theFileSource, sizeof(theFileSource));
// 如果是异步I/O, at this point we should set up the EventContext
if (inParams->inFlags & qtssOpenFileAsync)
{
theEventContext = NEW EventContext(EventContext::kInvalidFileDesc,
Socket::GetEventThread());
theEventContext->InitNonBlocking(theFileSource->GetFD());
QTSS_SetValue(inParams->inFileObject, sEventContextAttr, 0, &theEventContext, sizeof(theEventContext));
}
Set up the other attribute values in the file object
（2）、ReadFile
通过QTSS_GetValuePtr获得OSFileSource对象，调用该对象的Read函数
四、QTSSReflectorModule模块
支持QTSS_Initialize_Role、QTSS_Shutdown_Role、QTSS_RTSPPreProcessor_Role、
QTSS_ClientSessionClosing_Role、QTSS_RTSPIncomingData_Role、QTSS_RTSPAuthorize_Role、
QTSS_RereadPrefs_Role、QTSS_RTSPRoute_Role
（1）、Register
调用QTSS_AddRole注册支持的Role的处理函数。
调用一系列的QTSS_AddStaticAttribute、QTSS_IDForAttr函数。
调用ReflectorStream::Register函数、RTPSessionOutput::Register函数。
（2）、Initialize
QTSSModuleUtils::Initialize(inParams->inMessages, inParams->inServer, inParams->inErrorLogStream);
QTAccessFile::Initialize(); sSessionMap = NEW OSRefTable();
sServerPrefs = inParams->inPrefs; sServer = inParams->inServer;
sPrefs = QTSSModuleUtils::GetModulePrefsObject(inParams->inModule);
ReflectorStream::Initialize(sPrefs); ReflectorSession::Initialize();
Report to the server that this module handles DESCRIBE, SETUP, PLAY, PAUSE, and TEARDOWN
RereadPrefs();
（3）、FindOrCreateSession
// 注意：sSessionMap是一个静态的全局变量，这里Resolve的参数是sdp文件的路径。
// 也就是说，在同时开启多个窗口播放同一个sdp文件时，都是使用同一个ReflectorSession对象，
// FindOrCreateSession也不会调用SetupReflectorSession函数，即ReflectorStream、
// ReflectorSocket等对象也不会被再次创建。从逻辑上理解也确实如此，因为只需要一套对象和
// Mp4live这类系统打交道。
// 但是在这种情况下，会重新创建RTSPSession、RTPSession对象。这样在
// QTSSReflectorModule::DoSetup函数里，会再次创建RTPSessionOutput对象，并添加到
// ReflectorStream的fOutputArray数组里。同时也会调用QTSS_AddRTPStream函数。
OSRef* theSessionRef = sSessionMap->Resolve(inPath);
if (theSessionRef == NULL)
{
// If this URL doesn't already have a reflector session, we must make a new one.
// The first step is to create an SDPSourceInfo object.
// 读取sdp文件
if(inData == NULL)
{
QTSSModuleUtils::ReadEntireFile(inPath->Ptr, &theFileDeleteData);
theFileData = theFileDeleteData;
} else theFileData = *inData;
OSCharArrayDeleter fileDataDeleter(theFileDeleteData.Ptr);
// 根据读取的sdp文件信息，创建SDPSourceInfo对象，该对象是SourceInfo的继承类。
// 在构建函数里，调用Parse函数，形成了描述sdp文件内容的StreamInfo数据结构。
SDPSourceInfo* theInfo = NEW SDPSourceInfo(theFileData.Ptr, theFileData.Len);
if(!theInfo->IsReflectable() || !InfoPortsOK(inParams, theInfo, inPath))
{ delete theInfo; return NULL; }
if(!AllowBroadcast(inParams->inRTSPRequest))
{
SendErrorResponseWithMessage(inParams->inRTSPRequest, qtssClientForbidden,
&sBroadcastNotAllowed);
return NULL;
}
// Setup a ReflectorSession and bind the sockets. If we are negotiating, make sure
// to let the session know that this is a Push Session so ports may be modified.
// 创建并配置ReflectorSession对象
theSession = NEW ReflectorSession(inPath);
// buffer the incoming streams for clients
theSession->SetHasBufferedStreams(true);
// SetupReflectorSession stores theInfo in theSession so DONT delete the Info if
// we fail here, leave it alone. deleting the session will delete the info.
theSession->SetupReflectorSession(theInfo, inParams,
theSetupFlag,sOneSSRCPerStream, sTimeoutSSRCSecs);
sSessionMap->Register(theSession->GetRef());
}
（4）、ProcessRTSPRequest
QTSS_RTSPPreProcessor_Role的处理函数。
针对RTSP请求的内容，做不同的处理：
AnnounceMethod: DoAnnounce()
DescribeMethod: DoDescribe()
SetupMethod: DoSetup()
PlayMethod: DoPlay()
TeardownMethod: QTSS_Teardown()、QTSS_SendStandardRTSPResponse()
PauseMethod: QTSS_Pause()、QTSS_SendStandardRTSPResponse()
（5）、DoDescribe
// 调用FindOrCreateSession，创建ReflectorSession对象
ReflectorSession* theSession = DoSessionSetup(inParams, qtssRTSPReqFilePath, false, NULL,
&theFilepath);
If there already was an RTPSessionOutput attached to this Client Session, destroy it.
// Send the DESCRIBE response
Process SDP to remove connection info and add track IDs, port info, and default c= line
Clean up missing required SDP lines
Check the headers
Put SDP header lines in correct order
Write the SDP
调用SendDescribeResponse
（6）、DoSetup
... ...
RTPSessionOutput** theOutput = NULL;
theErr = QTSS_GetValuePtr(inParams->inClientSession, sOutputAttr, 0, (void**)&theOutput,
&theLen);
// 注意对于一个新的播放链接来说，RTSPSession、RTPSession都是新创建的对象，所以需要重新
// 创建RTPSessionOutput对象
if (theLen != sizeof(RTPSessionOutput)) {
// Check to see if we have a RTPSessionOutput for this Client Session. If we don't we
// should make one
... ...
RTPSessionOutput *theNewOutput = NEW RTPSessionOutput(inParams->inClientSession,
theSession, sServerPrefs, sStreamCookieAttr);
// 针对ReflectorSession的每一个ReflectorStream，都将theNewOutput添加进
// fOutputArray[bucket][y]
theSession->AddOutput(theNewOutput, true);
// If this is an incoming data session, skip everything having to do with setting up a
// new RTP Stream.
if (isPush)
{ ... ...}
// Get info about this trackID
// 音视频流有不同的trackID，不同的PayloadName、PayloadType
theStreamInfo = theSession->GetSourceInfo()->GetStreamInfoByTrackID(theTrackID);
thePayloadName = &theStreamInfo->fPayloadName;
thePayloadType = theStreamInfo->fPayloadType;
... ...
// 实际上调用的是RTPSession::AddStream，创建RTPStream对象。
QTSS_AddRTPStream(inParams->inClientSession, inParams->inRTSPRequest, &newStream, 0);
// Set up dictionary items for this stream
QTSS_SetValue(newStream,qtssRTPStrPayloadName,0,thePayloadName->Ptr,thePayloadName->Len);
... ...
// Place the stream cookie in this stream for future reference
// 即返回对应该trackID的fStreamArray数组中的ReflectorStream对象。
QTSS_SetValue(newStream, sStreamCookieAttr, 0, &theStreamCookie, sizeof(theStreamCookie));
void* theStreamCookie = theSession->GetStreamCookie(theTrackID);
... ...
QTSS_SendStandardRTSPResponse(...);
（7）、DoPlay
// it is a broadcast session so store the broadcast session.
// broadcast session？？？应用在什么场合？？？
if(inSession == NULL)
{ ... ...};
... ...
// 实际上是调用RTPSession::Play函数，在该函数里会执行“this->Signal(Task::kStartEvent)”
// 从而导致RTPSession::Run函数运行。
// 在RTPSession::Run函数里，调用
// fModule->CallDispatch(QTSS_RTPSendPackets_Role, &theParams)。
// 在我们分析的播放sdp文件这个情景里，fModule在RTSPSession::Run函数里被
// SetPacketSendingModule函数设置成为QTSSReflectorModule，而该Module并不支持
// QTSS_RTPSendPackets_Role，所以RTPSession::Run返回0，从而RTPSession::Run函数不会被
// TaskThread再次调度。
QTSS_Play(...);
QTSS_SendStandardRTSPResponse(...);
（二）、一些类的定义
? RTPSessionOutput
（1）、WritePacket
// make sure all RTP streams with this ID see this packet
for (UInt32 z = 0; QTSS_GetValuePtr(fClientSession, qtssCliSesStreamObjects, z,
(void**)&theStreamPtr, &theLen) == QTSS_NoErr; z++)
{
// 找到和ReflectorStream 相关联的RTPStream 对象
// 在我们分析的播放sdp 文件的这个情景里，该RTPStream 对象在
// QTSSReflectorModule::DoSetup 调用的QTSS_AddRTPStream 函数里创建。
if (this->PacketMatchesStream(inStreamCookie, theStreamPtr))
{
if(this->FilterPacket(theStreamPtr, inPacket)) return QTSS_NoErr;
if (this->PacketAlreadySent(theStreamPtr,inFlags, packetIDPtr))
return QTSS_NoErr;
if (!this->PacketReadyToSend(theStreamPtr,&currentTime, inFlags,
packetIDPtr,
timeToSendThisPacketAgain))
return QTSS_WouldBlock;
QTSS_PacketStruct thePacket;
thePacket.packetData = inPacket->Ptr;
// 这样设置packetTramsmitTime 的原因？？？
thePacket.packetTransmitTime = (currentTime - packetLatenessInMSec) +
(fBufferDelayMSecs - (currentTime - *arrivalTimeMSecPtr));
// 实际上调用的是RTPStream::Write 函数，见该函数的分析.
// 通过UDP Socket 发送音视频流。注意在我们分析的情景里，这个Socket 跟我们
// 用来和mp4live 交互的socket 不同。
writeErr = QTSS_Write(*theStreamPtr, &thePacket, inPacket->Len, NULL,
inFlags | qtssWriteFlagsWriteBurstBegin);
if (writeErr == QTSS_WouldBlock)
{ *timeToSendThisPacketAgain = thePacket.suggestedWakeupTime; }
else {
fLastIntervalMilliSec = currentTime – fLastPacketTransmitTime;
if (fLastIntervalMillisec > 1000) fLastIntervalMilliSec = 5;
fLastPacketTransmitTime = currentTime;
if (inFlags & qtssWriteFlagsIsRTP)
QTSS_SetValue (*theStreamPtr, sLastRTPPacketIDAttr, 0,
packetIDPtr, sizeof(UInt64));
else if (inFlags & qtssWriteFlagsIsRTCP)
}
}
}
? ReflectorSender
（1）、SendPacketsToOutput
OSQueueElem* lastPacket = currentPacket;
// starts from beginning if currentPacket == NULL, else from currentPacket
// 将传进来的Packet 作为当前packet
OSQueueIter qIter(&fPacketQueue, currentPacket);
while (!qIter.IsDone()) {
currentPacket = qIter.GetCurrent(); lastPacket = currentPacket;
thePacket = (ReflectorPacket*)currentPacket->GetEnclosingObject();
packetLateness = bucketDelay; timeToSendPacket = -1;
// 实际上是调用RTPSessionOutput::WritePacket
err = theOutput->WritePacket(&thePacket->fPacketPtr, fStream... )
if (err == QTSS_WouldBlock) {
if((timeToSendPacket >0)&&((fNextTimeToRun +currentTime) >timeToSendPacket))
fNextTimeToRun = timeToSendPacket - currentTime;
if (theOutput->fLastIntervalMilliSec < 5 )
theOutput->fLastIntervalMilliSec = 5;
if (theOutput->fLastIntervalMilliSec >= 1000 )
theOutput->fLastIntervalMilliSec = 1000;
else theOutput->fLastIntervalMilliSec *= 2;
if (timeToSendPacket<0) fNextTimeToRun =theOutput->fLastIntervalMilliSec;
if (fNextTimeToRun > 1000) fNextTimeToRun = 1000;
if (fNextTimeToRun < 5) fNextTimeToRun = 5;
break;
}
count++; qIter.Next();
}
// 注意：如果WritePacket 返回为QTSS_WouldBlock，则lastPacket 不为空。
return lastPacket;
（2）、RemoveOldPackets
遍历fPacketQueue
packetDelay = theCurrentTime – thePacket->fTimeArrived;
// remove packets that are too old
// sMaxPacketAgeMSec = sOverBufferMsec，对应于配置文件中
// reflector_buffer_size_sec，缺省为10s，如果延迟大于这个时间，就去掉这个包
if ( !thePacket->fNeededByOutput && packetDelay > currentMaxPacketDelay) {
thePacket->Reset(); fPacketQueue.Remove(elem);
inFreeQueue->EnQueue(elem);
} else {
thePacket->fNeededByOutput = false;
if (pakcetDelay <= currentMaxPacketDelay) break;
}
（3）、ReflectPackets
/****************************************************************************************
*******
/ ReflectorSender::ReflectPackets
/ There are n ReflectorSender's for n output streams per presentation.
/ Each sender is associated with an array of ReflectorOutput's. Each output
/ represents a client connection. Each output has # RTPStream's.
/ When we write a packet to the ReflectorOutput he matches it's payload
/ to one of his streams and sends it there.
/ To smooth the bandwitdth (server, not user) requirements of the reflected
/ streams, the Sender groups the ReflectorOutput's into buckets. The input
/ streams are reflected to each bucket progressively later in time. So rather
/ than send a single packet to say 1000 clients all at once, we send it to
/ just the first 16, then then next 16 100 ms later and so on.
/
/ intputs ioWakeupTime - relative time to call us again in MSec
/ inFreeQueue - queue of free packets.
/****************************************************************************************
*******
// Call old routine for relays; they don't want buffering.
// 在reflectorSession::FindOrCreateSession 函数里，调用了SetHasBufferedStreams(true)
if (!fStream->BufferEnabled()) {
this->ReflectRelayPackets(ioWakeupTime,inFreeQueue);
return;
}
// make sure to reset these state variables
fHasNewPackets = false; fNextTimeToRun = 10000; // init to 10 secs
// fRTCPSender: qtssWriteFlagsIsRTCP fRTPSender: qtssWriteFlagsIsRTP
if (fWriteFlag == qtssWriteFlagsIsRTCP)
fNextTimeToRun = 1000;
// determine if we need to send a receiver report to the multicast source
if ((fWriteFlag == qtssWriteFlagsIsRTCP) && (currentTime > (fLastRRTime + kRRInterval)))
{ fLastRRTime = currentTime; fStream->SendReceiverReport(); }
// Check to see if we should update the session's bitrate average
fStream->UpdateBitRate(currentTime);
// where to start new clients in the q
// sFirstPakcetOffsetMsec 缺省为500
// 在sender 的fPacketQueue 队列里寻找合适的包
// packetDelay = theCurrentTime - thePacket->fTimeArrived;
// 这里的sOverBufferInSec 对应配置文件中的“reflector_buffer_size_sec”
// if ( packetDelay <= (ReflectorStream::sOverBufferInMsec - offsetMsec) )
// oldestPacketInClientBufferTime = &thePacket->fQueueElem;
// ... return oldestPacketInClientBufferTime
fFirstPacketInQueueForNewOutput =
this->GetClientBufferStartPacketOffset(ReflectorStream::sFirstPacketOffsetMsec);
// 我们在QTSSReflectorModule::DoSetup 里面看到，对于一个ReflectorSession 的每一个
// ReflectorStream，都调用了AddOutput 添加了一个RTPSessionOutput 对象。
// 在开启n 个窗口同时播放同一个sdp 文件的情况下，会有n 个theOutput 对应n 个RTPStream,
// 依序通过这n 个theOutput 发送RTP 数据。
for (UInt32 bucketIndex = 0; bucketIndex < fStream->fNumBuckets; bucketIndex++)
for (UInt32 bucketMemberIndex = 0; bucketMemberIndex < fStream->sBucketSize; bucketMemberIndex++)
{ ReflectorOutput* theOutput = fStream->fOutputArray[bucketIndex][bucketMemberIndex];
if (theOutput != NULL) {
// 检查这个output 是否处于play 状态
if ( flase == theOutput->IsPlaying()) continue;
// 返回既在fBookmarkedPacketsElemsArray 数组同时属于fPacketQueue
// 的成员
packetElem = theOutput->GetBookMarkedPacket(&fPacketQueue);
if (packetElem == NULL) {
// everybody starts at the oldest packet in the buffer delay
// or uses a bookmark
packetElem = fFirstPacketInQueueForNewOutput;
theOutput->fNewOutput = false;
}
// sBucketDelayInMsec 对应于配置文件中的
// reflector_bucket_offset_delay_msec，缺省值为73.
bucketDelay =
ReflectorStream::sBucketDelayInMsec*(SInt64)bucketIndex;
packetElem = this->SendPacketsToOutput(theOutput,
packetElem,currentTime, bucketDelay);
if (packetElem) {
ReflectorPacket *thePacket =
(ReflectorPacket *)packetElem->GetEnclosingObject();
thePacket->fNeededByOutput = true;
// 添加到fBookmarkedPacketsElemsArray
theOutput->SetBookMarkPacket(packetElem);
}
}
}
}
this->RemoveOldPackets(inFreeQueue);
fFirstNewPacketInQueue = NULL;
// Don't forget that the caller also wants to know when we next want to run
// ReflectorSocket::Run 根据*ioWakeupTime 来决定idelTimer 的值。
if (*ioWakeupTime == 0) *ioWakeupTime = fNextTimeToRun;
else if((fNextTimeToRun > 0) && (*ioWakeupTime > fNextTimeToRun))
*ioWakeupTime = fNextTimeToRun;
// exit with fNextTimeToRun in real time, not relative time.
fNextTimeToRun += currentTime;
? ReflectorSocket
IdleTask、UDPSocket 的继承类。
（1）、构建函数
: IdleTask(), UDPSocket(NULL, Socket::kNonBlockingSocketType | UDPSocket::kWantsDemuxer),
... ...
this->SetTaskName(“ReflectorSocket”); this->SetTask(this);
for (UInt32 numPackets = 0; numPackets < kNumPreallocatedPackets; numPackets++)
{
ReflectorPacket* packet = NEW ReflectorPacket();
fFreeQueue.EnQueue(&packet->fQueueElem); // put this packet onto the free queue
}
（2）、AddSender
... ...
this->GetDemuxer()->RegisterTask(inSender->fStream->fStreamInfo.fSrcIPAddr, 0, inSender);
fSenderQueue.EnQueue(&inSender->fSocketQueueElem);
（3）、ProcessPacket
由一个循环组成。
// 对于mp4live 过来的音视频流来说，肯定不是RTCP 数据。
if (GetLocalPort() & 1) thePacket->fIsRTCP = true;
else thePacket->fIsRTCP = false;
// always refresh timeout even if we are filtering
if (fBroadcasterClientSession != NULL) { ... ...}
if (thePacket->fPacketPtr.Len == 0)
{ 将thePacket 重新插入fFreeQueue 队列，重新调用RequestEvent 监听端口}
if (thePacket->IsRTCP()) { ... ...}
// Only reflect one SSRC stream at a time. Pass the packet and whether it is an RTCP or
// RTP packet based on the port number.
if (fFilterSSRCs) this->FilterInvalidSSRCs(thePacket, GetLocalPort() & 1);
// Find the appropriate ReflectorSender for this packet.
// 在bindSockets 函数里，已经对Socket A、B 调用AddSender 注册了fRTPSender、fRTCPSender
ReflectorSender* theSender=(ReflectorSender*)this->GetDemuxer()->GetTask(theRemoteAddr,
0);
对thePacket、theSender 进行一系列设置
// 将thePacket 插入theSender 的fPacketQueue
theSender->fPacketQueue.EnQueue(&thePacket->fQueueElem);
... ...
（4）、GetIncomingData
theRemoteAddr = theRemotePort = 0;
// get all the outstanding packets for this socket
while(true) {
// get a packet off the free queue.
// 如果fFreeQueue 里已经没有ReflectorPacket 链接，则创建一个ReflectorPacket 对象
// 否则从fFreeQueue 里Dequeue 一个ReflectorPacket 对象
ReflectorPacket* thePacket = this->GetPacket();
thePacket->fPacketPtr.Len = 0;
// 调用::recvfrom 从socket 里读取数据
this->RecvFrom(&theRemoteAddr, &theRemotePort, thePacket->fPacketPtr.Ptr,
ReflectorPacket::kMaxReflectorPacketSize, &thePacket->fPacketPtr.Len);
// 获取Socket 对应的Sender，对Sender、thePacket 进行一系列设置，最终将thePacket
// 挂入Sender 的fPacketQueue
if (this->ProcessPacket(inMilliseconds,thePacket,theRemoteAddr, theRemotePort))
break;
}
（5）、Run
我们在ReflectorStream::BindSockets 函数里看到：
fSockets->GetSocketA()->RequestEvent(EV_RE); //这里的Socket 是ReflectorSocket 对象
fSockets->GetSocketB()->RequestEvent(EV_RE);
这样一旦监听的socket 有数据（相当于mp4live 将编码的音视频流通过socket 发送过来），
EventContext::ProcessEvent 函数会调用Siganl(Task::kReadEvent)，导致该Run 函数运行。
// We want to make sure we can't get idle events WHILE we are inside this function. That
// will cause us to run the queues unnecessarily and just get all confused.
this->CancelTimeout();
theEvents = this->GetEvents();
// 从socket 里面读取数据，并和Sender 关联起来
if (theEvents & Task::kReadEvent) this->GetIncomingData(theMilliseconds);
// Now that we've gotten all available packets, have the streams reflect
// 为什么这里不只是该Socket 所对应的Sender，而是所有的Sender!!!
// 可能是因为另外Socket 对应的Sender 也会有数据等待Reflect
for (OSQueueIter iter2(&fSenderQueue); !iter2.IsDone(); iter2.Next())
{
ReflectorSender* theSender2 =
(ReflectorSender*)iter2.GetCurrent()->GetEnclosingObject();
// 根据fNextTimeToRun 和当前时间判断是否马上进行Reflect.
// Sender 的fNextTimeToRun 该如何确定？？？
if (theSender2 != NULL && theSender2->ShouldReflectNow(theMilliseconds, &fSleepTime))
theSender2->ReflectPackets(&fSleepTime, &fFreeQueue);
}
// For smoothing purposes, the streams can mark when they want to wakeup.
// fSleepTime 实际上是Sender 的fNextTimeToRun，利用IdleTimerThread 实现下一次的继续运行。
if (fSleepTime > 0) this->SetIdleTimer(fSleepTime);
return 0; // 返回0,说明该Run 函数不会继续被运行除非被Signal 唤醒
? ReflectorStream
This object supports reflecting an RTP multicast stream to N RTPStreams. It spaces out
the packet send times in order to maximize the randomness of the sending pattern and
smooth the stream.
（1）、构建函数
... ...
fStreamInfo.Copy(*inInfo);
// Allocate Bucket array
// 创建fNumBuckets 个Bucket(即ReflectorOutput**)对象数组，地址赋给fOutputArray.
// 针对fOutputArray 的每一个元素，创建指向ReflectorOutput 的指针数组，将地址赋给
// 发outputArray 的元素。
this->AllocateBucketArray(fNumBuckets);
// Write RTCP Packet
设置fReceiverReportBuffer、fEyeLocation、fReceiverReportSize
if (SocketUtils::IsMulticastIPAddr(fStreamInfo.fDestIPAddr))
{ fDestRTCPAddr = fStreamInfo.fDestIPAddr; fDestRTCPPort = fStreamInfo.fPort+1; }
（2）、BindSockets
... ...
// get a pair of sockets. The socket must be bound on INADDR_ANY because we don't know
// which interface has access to this broadcast. If there is a source IP address
specified
// by the source info, we can use that to demultiplex separate broadcasts on the same
// port. If the src IP addr is 0, we cannot do this and must dedicate 1 port per
broadcast
// 如果找不到，就创建socket 对
// 注意这里调用的是ReflectorSocketPool::ConstructUDPSocketPair
// NEW UDPSocketPair(NEW ReflectorSocket(), NEW ReflectorSocket())
// 这里是检查sdp 文件所指定的目的地址是否为多播地址，相当于mp4live 是否将媒体进行多播。
isMulticastDest = (SocketUtils::IsMulticastIPAddr(fStreamInfo.fDestIPAddr));
// 注意GetUDPSocketPair 搜索socket 对的条件。对于指定了IP、Port 的情况，
// QTSServer::SetupUDPSockets 创建的socket 对显然无法满足要求，所以这里会再次创建socket
// 对。
if (isMulticastDest) {
fSockets = sSocketPool.GetUDPSocketPair(INADDR_ANY, fStreamInfo.fPort,
fStreamInfo.fSrcIPAddr, 0);
} else {
fSockets = sSocketPool.GetUDPSocketPair(fStreamInfo.fDestIPAddr, fStreamInfo.fPort,
fStreamInfo.fSrcIPAddr, 0);
}
... ...
// also put this stream onto the socket's queue of streams
((ReflectorSocket*)fSockets->GetSocketA())->AddSender(&fRTPSender);
((ReflectorSocket*)fSockets->GetSocketB())->AddSender(&fRTCPSender);
// A broadcaster is setting up a UDP session so let the sockets update the session
if (fStreamInfo.fSetupToReceive &&qtssRTPTransportTypeUDP==transportType&&inParams!=NULL)
{
((ReflectorSocket*)fSockets->GetSocketA())->AddBroadcasterSession(inParams-
>inClientSession);
((ReflectorSocket*)fSockets->GetSocketB())->AddBroadcasterSession(inParams-
>inClientSession);
}
((ReflectorSocket*)fSockets->GetSocketA())->SetSSRCFilter(filterState, timeout);
((ReflectorSocket*)fSockets->GetSocketB())->SetSSRCFilter(filterState, timeout);
// Always set the Rcv buf size for the sockets. This is important because the these
// sockets is only useful for RTCP Rrs.
// 512K
fSockets->GetSocketA()->SetSocketRcvBufSize(512 * 1024);
fSockets->GetSocketB()->SetSocketRcvBufSize(512 * 1024);
if (isMulticastDest) { ... ...} // 针对sdp 的多播的目的地址
fStreamInfo.fPort = fSockets->GetSocketA()->GetLocalPort();
// 申请监听
fSockets->GetSocketA()->RequestEvent(EV_RE);
fSockets->GetSocketB()->RequestEvent(EV_RE);
// Copy the source ID and setup the ref
StrPtrLen theSourceID(fSourceIDBuf, kStreamIDSize);
ReflectorStream::GenerateSourceID(&fStreamInfo, fSourceIDBuf);
fRef.Set(theSourceID, this);
（3）、AddOutput
// 寻找第一个fOutputArray[num][x] == NULL,将putInThisBucket 设为num
if (putInThisBucket < 0) putInThisBucket = this->FindBucket();
if (fNumBuckets <= (Uint32)putInThisBucket) this-
>AllocateBucketArray(putInThisBucket * 2);
// 保存inOutput
for(UInt32 y=0; y<sBucketSize; y++) {
if (fOutputArray[putInThisBucket][y] == NULL)
{ fOutputArray[putInThisBucket][y] = inOutput;
fNumElements++; return putInThisBucket;
}
}
? ReflectorSession
This object supports reflecting an RTP multicast stream to N RTPStreams. It spaces out
the packet send times in order to maximize the randomness of the sending pattern and
smooth the stream.
（1）、SetupReflectorSession
fLocalSDP.Delete(); fLocalSDP.Ptr = inInfo->GetLocalSDP(&fLocalSDP.Len);
// Allocate all our ReflectorStreams, using the SourceInfo
delete fStreamArray;
// 音视频分为两个流，对于每个流，创建ReflectorStream 对象。
fStreamArray = NEW ReflectorStream*[fSourceInfo->GetNumStreams()];
for (UInt32 x = 0; x < fSourceInfo->GetNumStreams(); x++)
{ ... ...
if(theStreamRef == NULL)
{
fStreamArray[x] = NEW ReflectorStream(fSourceInfo->GetStreamInfo(x));
fStreamArray[x]->BindSockets(inParams,inFlags, filterState, filterTimeout);
fStreamArray[x]->SetEnableBuffer(this->fHasBufferedStreams);
fSourceInfo->GetStreamInfo(x)->fPort = fStreamArray[x]->GetStreamInfo()->fPort;
ReflectorStream::GenerateSourceID(fSourceInfo->GetStreamInfo(x), &theStreamID[0]);
sStreamMap->Register(fStreamArray[x]->GetRef());
}
}
（2）、AddOutput
bucket = -1; lastBucket = -1;
while (true) {
// 针对每一个ReflectorStream 调用AddOutput 添加inOutput
for ( ; x < fSourceInfo->GetNumStreams(); x++) {
bucket = fStreamArray[x]->AddOutput(inOutput, bucket);
if (bucket == -1) break;
else {
lastBucket = bucket;
if (isClient) fStreamArray[x]->IncEyeCount();
}
}
... ...
} atomic_add(&fNumOutputs, 1);
? QTAtom
（1）、构建函数
QTAtom::QTAtom(QTFile * File, QTFile::AtomTOCEntry * Atom, Bool16 Debug, Bool16 DeepDebug)
: fDebug(Debug), fDeepDebug(DeepDebug), fFile(File)
{ memcpy(&fTOCEntry, Atom, sizeof(QTFile::AtomTOCEntry)); }
? QTAtom_mvhd
基于QTAtom 类
（1）、构建函数
QTAtom_mvhd::QTAtom_mvhd(QTFile* File, QTFile::AtomTOCEntry* TOCEntry, Bool16 Debug, Bool16
DeepDebug)
: QTAtom(File, TOCEntry, Debug, DeepDebug)
{ }
（2）、Initialize()
// Parse this atom's fields. fFile 为QTFile 类型的对象
// 调用fFile->Read(fTOCEntry.AtomDataPos+Offset, Buffer, Length)
ReadInt32(mvhdPos_VersionFlags, &tempInt32);
fVersion = (Uint8)((tempInt32 >> 24) & 0x000000ff); fFlags = tempInt32 &
0x00ffffff;
通过fFile->Read 读取各个参数数据保存到fCreationTime、fModificationTime... ...
? QTTrack
The central point of control for a track in a QTFile.
（1）、构建函数
QTTrack::QTTrack(QTFile * File, QTFile::AtomTOCEntry * Atom, Bool16 Debug, Bool16
DeepDebug)
: fDebug(Debug), fDeepDebug(DeepDebug), fFile(File),
... ...
{
QTFile::AtomTOCEntry *tempTOCEntry;
// Make a copy of the TOC entry.
memcpy(&fTOCEntry, Atom, sizeof(QTFile::AtomTOCEntry));
// Load in the track header atom for this track.
fFile->FindTOCEntry(“:tkhd”, &tempTOCEntry, &fTOCEntry)
// 创建QTAtom_tkhd 类对象，并执行Initialize 函数，类似于QTAtom_mvhd 类。
fTrackHeaderAtom = NEW QTAtom_tkhd(fFile, tempTOCEntry, fDebug, fDeepDebug);
fTrackHeaderAtom->Initialize();
}
（2）、Initialize()
// See if this track has a name and load it in.
// fTOCEntry 在构建函数里初始化。
if( fFile->FindTOCEntry(":udta:name", &tempTOCEntry, &fTOCEntry) ) {
fTrackName = NEW char[ (SInt32) (tempTOCEntry->AtomDataLength + 1) ];
if( fTrackName != NULL )
fFile->Read(tempTOCEntry->AtomDataPos, fTrackName, (UInt32) tempTOCEntry->AtomDataLength);
}
// Load in the media header atom for this track.
fFile->FindTOCEntry(":mdia:mdhd", &tempTOCEntry, &fTOCEntry)
fMediaHeaderAtom = NEW QTAtom_mdhd(fFile, tempTOCEntry, fDebug, fDeepDebug);
fMediaHeaderAtom->Initialize();
// Load in the edit list atom for this track.
类似于上面那样创建并初始化fEditListAtom，并初始化fFirstEditMediaTime。
// Load in the data reference atom for this track.
创建并初始化fDataReferenceAtom。
// Load in the sample table atoms.
创建并初始化fTimeToSampleAtom、fCompTimeToSampleAtom、fSampleToChunkAtom、
fSampleDescriptionAtom、fChunkOffsetAtom、fSampleSizeAtom、fSyncSampleAtom
fIsInitialized = true;
? QTHintTrack
QTTrack 的继承类，The central point of control for a hint track in a
QTFile.
（1）、构建函数
QTHintTrack::QTHintTrack(QTFile * File, QTFile::AtomTOCEntry * Atom, Bool16 Debug, Bool16 DeepDebug)
: QTTrack(File, Atom, Debug, DeepDebug),
... ...
（2）、Initialize()
QTTrack::Initialize()
// Get the sample description table for this track and verify that it is an RTP track.
// fSampleDescriptionAtom 在QTTrack::Initialize 里面创建并初始化
fSampleDescriptionAtom->FindSampleDescription(FOUR_CHARS_TO_INT('r', 't', 'p', ' '),
&sampleDescription, &sampleDescriptionLength)
::memcpy(&fMaxPacketSize, sampleDescription + 20, 4);
fMaxPacketSize = ntohl(fMaxPacketSize);
for( pSampleDescription = (sampleDescription + 24); pSampleDescription <
(sampleDescription + sampleDescriptionLength);)
{
// Get the entry length and data type of this entry
::memcpy(&entryLength, pSampleDescription+0, 4); entryLength=ntohl(entryLength);
::memcpy(&dataType, pSampleDescription+4, 4); dataType = ntohl(dataType);
// Process this data type.
switch(dataType) {
case FOUR_CHARS_TO_INT('t', 'i', 'm', 's'): // tims RTP timescale
::memcpy(&fRTPTimescale, pSampleDescription + 8, 4);
fRTPTimescale = ntohl(fRTPTimescale);
break;
case FOUR_CHARS_TO_INT('t', 's', 'r', 'o'): // tsro Timestamp random
offset
::memcpy(&fTimestampRandomOffset, pSampleDescription + 8, 4);
fTimestampRandomOffset = ntohl(fTimestampRandomOffset);
break;
case FOUR_CHARS_TO_INT('s', 'n', 'r', 'o'): // snro Sequence number random
offset
::memcpy(&fSequenceNumberRandomOffset, pSampleDescription + 8, 2);
fSequenceNumberRandomOffset = ntohl(fSequenceNumberRandomOffset);
break;
} pSampleDescription += entryLength;
}
// Load in the hint info atom for this track.
创建并初始化fHintInfoAtom
// Load in the hint track reference atom for this track.
创建并初始化fHintTrackReferenceAtom
// Allocate space for our track reference table.
numTrackRefs = fHintTrackReferenceAtom->GetNumReferences();
fTrackRefs = NEW QTTrack *[numTrackRefs];
// Locate all of the tracks that we use, but don't initialize them until we actually try
// to access them.
for( UInt32 CurRef = 0; CurRef < numTrackRefs; CurRef++ )
{
// Get the reference and make sure it's not empty.
fHintTrackReferenceAtom->TrackReferenceToTrackID(CurRef, &trackID)
// Store away a reference to this track.
fFile->FindTrack(trackID, &fTrackRefs[CurRef]);
}
// Calculate the first RTP timestamp for this track.
设置fFirstRTPTimestamp
fHintTrackInitialized = true;
? OSFileSource
底层的文件操作类，simple file abstraction. This file abstraction is ONLY to be used for
files intended for serving。
（1）构建函数
会调用Set 函数，在该函数里，调用open 打开文件、调用fstat 获取文件信息。
（2）Read
调用ReadFromPos 或者ReadFromCache。
ReadFromPos 和ReadFromCache 的区别待分析！！
? QTSSFile
（1）Open
// Because this is a role being executed from inside a callback, we need to make
// sure that QTSS_RequestEvent will not work ？？？
... ... curTask = theState->curTask; ... ...
调用注册QTSS_OpenFilePreProcess_Role 处理的模块的处理函数。系统自带的模块没有提
供这个Role 的处理。
如果返回QTSS_FileNotFound，则调用注册QTSS_OpenFile_Role 处理的模块的处理函数。
QTSSPosixFileSysModule 提供了这个Role 的处理。
将上述找到的模块赋给fModule，后续可以通过fModule 来调用该模块没有注册的Role 处理
函数。
... ...theState->curTask = curTask;
? QTFile
（1）、Read(UInt64 Offset, char* const Buffer, UInt32 Length, QTFile_FileControlBlock*
FCB)
if (FCB) FCB->Read(&fMovieFD, Offset, Buffer, Length);
else { QTSS_Seek(fMovieFD, Offset); QTSS_Read(fMovieFD, Buffer, Length); }
（2）、GenerateAtomTOC
// Scan through all of the atoms in this movie, generating a TOC entry for each one.
CurPos = 0;
while ( Read(CurPos, (char *)&atomLength, 4) ) {
// Swap the AtomLength for little-endian machines.
CurPos += 4; atomLength = ntohl(atomLength); BigAtomLength = (Uint64)atomLength;
hasBigAtom = false;
// Is AtomLength zero? If so, and we're in a 'udta' atom, then all is
// well (this is the end of a 'udta' atom). Leave this level of
// siblings as the 'udta' atom is obviously over.
// 发现了End-of-udta marker
if( (BigAtomLength==0)&&CurParent&&(CurParent->AtomType==FOUR_CHARS_TO_INT('u', 'd', 't',
'a')) ) { LastTOCEntry = CurParent； CurParent = CurParent->Parent;
goto lbl_SkipAtom; // Keep moving up.
}
// Is the AtomLength zero? If so, this is a "QT atom" which needs some additional
// work before it can be processed.
else if(BigAtomLength == 0)
{
// This is a QT atom; skip the (rest of the) reserved field and the lock
// count field.
CurPos += 22;
// Read the size and the type of this atom.
Read(CurPos, (char*)&atomLength, 4);
CurPos += 4; BigAtomLength = (Uint64)ntohl(atomLength);
Read(CurPos, (char*)&AtomType, 4);
CurPos += 4; AtomType = (Uint64)ntohl(AtomType);
// Skip over the rest of the fields.
CurPos += 12;
// Set the header size to that of a QT atom.
CurAtomHeaderSize = 10+16+4+4+4+2+2+4;
} else { // This is a normal atom; get the atom type.
Read(CurPos, (char*)&AtomType, 4); CurAtomHeaderSize = 4 + 4;
CurPos += 4; AtomType = (Uint64)ntohl(AtomType);
if(atomLength == 1) // large size atom
{
Read(CurPos, (char*)&BigAtomLength, 8);
BigAtomLength = QTAtom::NTOH64(BigAtomLength); CurPos += 8;
CurAtomHeaderSize += 8; //AtomLength+AtomType+big atom length
hasBigAtom = true;
}
if(AtomType == FOUR_CHARS_TO_INT('u', 'u', 'i', 'd'))
{ sExtendedTypeSize = 16;
// read and just throw it away we don't need to store
Read(CurPos, (char*)usertype, 16);
CurPos += sExtendedTypeSize; CurAtomHeaderSize += sExtendedTypeSize;
}
}
if(BigAtomLength == 0) return false;
if ((AtomType == FOUR_CHARS_TO_INT('m', 'o', 'o', 'v')) && (hasMoovAtom))
{ // Skip over any additional 'moov' atoms once we find one.
CurPos += BigAtomLength – CurAtomHeaderSize; continue;
} else if (AtomType == FOUR_CHARS_TO_INT('m', 'o', 'o', 'v')
hasMoovAtom = true;
else if (!hasMoovAtom) {
CurPos == BigAtomLength – CurAtomHeaderSize; continue;
}
// Create a TOC entry for this atom，并加入fTOC、fTOCOrdHead、fTOCOrdTail 维护的
// 链表。
NewTOCEntry = NEW AtomTOCEntry();
... ...
// Figure out if we have to descend into this entry and do so.
switch (NewTOCEntry->AtomType)
{
case FOUR_CHARS_TO_INT('m', 'o', 'o', 'v'): //moov
... ... // clip trak matt edts tref mdia minf dinf stbl udta hnti hinf
{ // All of the above atoms need to be descended into. Set up our
// variables to descend into this atom.
if (NewTOCEntry->AtomDataLength > 0)
{ CurParent = NewTOCEntry; LastTOCEntry = NULL; continue; }
} break;
}
CurPos += NewTOCEntry->AtomDataLength; // Skip over this atom's data
lbl_SkipAtom:
while(... ...) {
LastTOCEntry = CurParent; CurParent = CurParent->Parent;
}
}
if(!this->ValidTOC()) // make sure we were able to read all the atoms.
return false;
return true; // The TOC has been successfully read in.
（4）、Open
Open a movie file and generate the atom table of contents.
// 创建QTSSFile 对象，并调用Open 函数
QTSS_OpenFileObject(fMoviePath, qtssOpenFileReadAhead, &fMovieFD);
// We have a file, generate the mod date str
fModDateBuffer.Update(this->GetModDate());
// Generate the table of contents for this movie.
GenerateAtomTOC();
// Find the Movie Header atom and read it in.
// 根据匹配AtomType 找到链表中的AtomTOCEntry 对象。
FindTOCEntry(“moov:mvhd”, &TOCEntry);
fMovieHeaderAtom = NEW QTAtom_mvhd(this, TOCEntry, fDebug, fDeepDebug);
// 读取这个atom 的数据
fMovieHeaderAtom->Initialize();
// Create QTTrack objects for all of the tracks in this movie. (Although this does incur
// some extra resource usage where tracks are not used, they can always A) be disposed of
// later, or B) be ignored as their use of system resources is exceptionally minimal.)
// NOTE that the tracks are *not* initialized here. That is done when they are actually
// used; either directly or by a QTHintTrack.
TOCEntry = NULL;
// 生成所有的Track/Hint Track 信息。
while (FindTOCEntry(“moov:trak”, &TOCEntry, TOCEntry)) {
ListEntry = NEW TrackListEntry();
// Make a hint track if that's what this is.
// QTHintTrack 基于QTTrack 类。在QTTrack 类的构建函数里，创建QTAtom_tkhd 类对象，
// 并执行Initialize 函数读取相关信息。
if( FindTOCEntry(":tref:hint", NULL, TOCEntry) ) {
ListEntry->Track = NEW QTHintTrack(this, TOCEntry, fDebug, fDeepDebug);
ListEntry->IsHintTrack = true;
} else {
ListEntry->Track = NEW QTTrack(this, TOCEntry, fDebug, fDeepDebug);
ListEntry->IsHintTrack = false;
}
// GetTrackID 实际上返回的是QTAtom_thkd::fTrackID，由QTTrack 构建函数调用的
// fTrackHeaderAtom::Initialize(即QTAtom_tkhd::Initialize)函数从媒体中读取并初始
化。
// 在fFirstTrack 所指向的链表中搜寻
if(FindTrack(ListEntry->Track->GetTrackID(), theTrack))
{ // A track with this track ID already exists. Ignore other tracks with
// identical track IDs.
delete ListEntry->Track; delete ListEntry; continue;
}
// Add this track object to our track list.
ListEntry->TrackID = ListEntry->Track->GetTrackID();
ListEntry->NextTrack=NULL;
if(fFirstTrack == NULL) fFirstTrack = fLastTrack = ListEntry;
else { fLastTrack->NextTrack = ListEntry; fLastTrack = ListEntry; }
fNumTracks++;
}
? QTRTPFile
（1）、new_QTFile
... ...
QTRTPFile::RTPFileCacheEntry *fileCacheEntry;
// Find and return the QTFile object out of our cache, if it exists.
// 从gFirstFileCacheEntry 开始搜索，一旦发现listEntry->fFilename 和filePath 相同，
// 则返回listEntry。
if ( QTRTPFile::FindAndRefcountFileCacheEntry(filePath, &fileCacheEntry) )
{ ... ...*theQTFile = fileCacheEntry->File; return errNoError; }
// 创建QTFile 对象，并调用Open 函数。
*theQTFile = NEW QTFile(debugFlag, deepDebugFlag);
(*theQTFile)->Open(filePath);
// Add this file to our cache and release the global add mutex.
// 和上面的搜索动作相对应
QTRTPFile::AddFileToCache(filePath, &fileCacheEntry);
// Finish setting up the fileCacheEntry.
if( fileCacheEntry != NULL )
{ fileCacheEntry->File = *theQTFile; fileCacheEntry->InitMutex->Unlock();
}
（2）、Initialize
// create our file object.
this->new_QTFile(filePath, &fFile, fDebug, fDeepDebug);
// Iterate through all of the tracks, adding hint tracks to our list.
for(track = NULL; fFile->NextTrack(&track, track); )
{
在fFile 中已生成的track 信息中寻找hint track 信息。
对于hint track：
创建并初始化RTPTrackListEntry 对象。
将该对象添加到由fFirstTrack、fLastTrack 维护的链表中。
计数
}
// If there aren't any hint tracks, there's no way we can stream this
// movie, so notify the caller！！！
if (fNumHintTracks == 0) return fErr = errNoHintTracks;
return errNoError; // The RTP file has been initialized.
（3）、AddTrack(UInt32 trackID, Bool16 useRandomOffset)
// Find this track.
this->FindTrackEntry(trackID, &trackEntry);
OSMutexLocker locker(fFile->GetMutex());
trackEntry->HintTrack->Initialize(); // Initialize this track.
Set up the sequence number and timestamp offsets.
// This track is now active.
trackEntry->IsTrackActive = true;
? FileSession
class FileSession
{
public:
... ...
QTRTPFile fFile;
QTSS_PacketStruct fPacketStruct;
SDPSourceInfo fSDPSource;
... ...
};
? RTPFileSession
（1）Initialize(StrPtrLen& inFilePath, Float32 inBufferSeconds)
首先创建RTPFile 类的对象，在RTPFile 的Initialize 函数里，创建QTSSFile 对象，并
通过QTSSFile 对象获取文件的头部及SDP、track 信息，同时根据这些信息分配data
buffer。
// check to see if this file is already open
OSMutexLocker locker(sOpenFileMap.GetMutex());
OSRef* theFileRef = sOpenFileMap.Resolve((StrPtrLen*)&inFilePath);
if(theFileRef == NULL)
{
fFile = NEW RTPFile(); //fFile 是RTPFileSession 的类型为RTPFile*的成员
fFile->Initialize(inFilePath);
sOpenFileMap.Register(fFile->GetRef());
// unless we do this, the refcount won't increment (and we'll delete the session prematurely
sOpenFileMap.Resolve(&inFilePath);
}
// 创建QTSSFile 对象fFileSource，并执行Open 操作
QTSS_OpenFileObject(inFilePath.Ptr, 0, &fFileSource);
// Get the file length
QTSS_GetValue(fFileSource, qtssFlObjLength, 0, &fFileLength, &theLen);
// Allocate our data buffer
// inBufferSeconds 为8，GetBytesPerSecond 即返回fFile->fBytesPerSecond
fDataBufferSize = this->PowerOf2Floor((UInt32)(inBufferSeconds * fFile-
>GetBytesPerSecond()));
限制fDataBufferSize 在kMaxDataBufferSize(256k)和kBlockSize(32k)之间
fReadBuffer = fDataBuffer = NEW Uint8[fDataBufferSize];
// Allocate a buffer of TrackInfos
fTrackInfo = NEW RTPFileSessionTrackInfo[fFile->GetMaxTrackNumber() + 1];
::memset(fTrackInfo, 0, fFile->GetMaxTrackNumber() *
sizeof(RTPFileSessionTrackInfo));
? RTPFile
（1）Initialize(const StrPtrLen& inFilePath)
// 创建QTSSFile 对象，并调用Open 函数
QTSS_OpenFileObject(inFilePath.Ptr, 0, &theFile);
根据inFilePath 设置fFilePath
fRef.Set(fFilePath, this);
// Read the header，调用QTSSFile 的Read 函数，在该函数里会调用
// fModule 的Dispatch 函数（在QTSSFile 的Open 函数里，寻找注册了Open 相关Role 的模
// 块，并将其赋给fModule，本系统是QTSSPosixFileSysModule）
QTSS_Read(theFile, &fHeader, sizeof(fHeader), &theLengthRead);
// Read the SDP data
// 类似于读取header
fSDPData.Len = fHeader.fSDPLen; fSDPData.Ptr = NEW char[fSDPData.Len + 1];
QTSS_Read(theFile, fSDPData.Ptr, fSDPData.Len, &theLengthRead);
// Parse the SDP Information
// 待分析!!
fSourceInfo.Parse(fSDPData.Ptr, fSDPData.Len);
// Read the track info
fTrackInfo = NEW RTPFileTrackInfo[fHeader.fNumTracks];
QTSS_Read(theFile, fTrackInfo, sizeof(RTPFileTrackInfo)*fHeader.fNumTracks, &theLengthRead);
// Create and read the block map
fBlockMap = NEW Uint8[fHeader.fBlockMapSize];
QTSS_Read(theFile, fBlockMap, fHeader.fBlockMapSize, &theLengthRead);
// Calculate bit rate of all the tracks combined
for (UInt32 x = 0; x < fHeader.fNumTracks; x++)
totalBytes += (Float64)fTrackInfo[x].fBytesInTrack;
totalBytes /= fHeader.fMovieDuration; fBytesPerSecond = (UInt32)totalBytes;
// Get the max track number
for (UInt32 x = 0; x < fHeader.fNumTracks; x++)
if(fTrackInfo[y].fID > fMaxTrackNumber)
fMaxTrackNumber = fTrackInfo[y].fID;
// 调用close 函数，销毁QTSSFile 对象。
QTSS_CloseFileObject(theFile);
? QTSSCallbacks
属于Server core 一部分。该类主要是为QTSServer 提供支持，比如一些独立子系统/模块通过
sCallbacks 来调用DSS 的处理函数，而这些函数由QTSSCallbacks 类提供定义。下面是一些成员函数
的分析：
（1）QTSS_AddRole
QTSS_ModuleState* theState = (QTSS_ModuleState*)OSThread::GetMainThreadData();
注意：我们在前面分析的“加载一个模块”的情景中，QTSServer::AddModule 中就调用
OSThread::SetMainThreadData(&theModuleState)，其实参为：
theModuleState.curModule = inModule;
theModuleState.curRole = QTSS_Register_Role;
theModuleState.curTask = NULL;
返回theState->curModule->AddRole(inRole)，实际上就是调用QTSSModule::AddRole 函数。
在QTSSModule::AddRole 函数里，根据传入的Role 将fRoleArray 数组的相应位置为true。
如果是QTSS_RTSPRequest_Role、QTSS_OpenFile_Role、QTSS_RTSPAuthenticate_Role，
特别地用一些全局量做标记。
调用SetValue Add this role to the array of roles attribute
（2）QTSS_AddService
返回QTSSDictionaryMap::GetMap(QTSSDictionaryMap::kServiceDictIndex)->
AddAttribute(inServiceName, (QTSS_AttrFunctionPtr)inFunctionPtr,
qtssAttrDataTypeUnknown, qtssAttrModeRead);
DSS 在初始化的时候调用了QTSSDictionaryMap 的Initialize 成员函数，针对各种类型的信
息（比如ServerDict、PrefsDict、TextMessagesDict、ServiceDict、RTPStreamDict 等等）
创建了QTSSDictionaryMap 的类对象，放在sDictionaryMaps 数组里。
QTSS_AddService 在kServiceDict 对应的QTSSDictionaryMap 的fAttrArray 里记录相关的信
息。
? QTSServerInterface 类
QTSServerInterface 类属于DSS server core，它基于QTSSDictionary 类。
This is the internal data storage object tagged as the QTSS_ServerObject in the API.
Each of the QTSS_ServerAttributes in the API is declared and implemented in this base class.
（1）、构建函数
QTSServer 是QTSServerInterface 的继承类，在StartServer 函数里创建QTSServer 类对象的时候，
必然会创建QTSServerInterface 类对象。
QTSServerInterface::QTSServerInterface()
: QTSSDictionary(QTSSDictionaryMap::GetMap(QTSSDictionaryMap::kServerDictIndex),
&fMutex),
... ...
{
初始化sModuleArray 数组、sNumModulesInRole 数组。
// 注意：在构建函数的初始化部分，传给QTSSDictionary 构建函数的是kServerDictIndex
// 对应的dict map。
// 调用基类QTSSDictionary 的SetVal 函数记录每个属性的数据来源和长度等信息。
// 注意和QTSServerInterface::Initialize 函数里调用SetAttribute 的不同。
this->SetVal(qtssSvrState, &fServerState, sizeof(fServerState));
this->SetVal(qtssServerAPIVersion, &sServerAPIVersion, sizeof(sServerAPIVersion));
... ...
}
（2）、QTSServerInterface::Initialize()
// 调用kServerDictIndex、kQTSSConnectedUserDictIndex 两个dict map 的SetAttribute 函数，
// 根据sAttributes、sConnectedUserAttributes 进行属性信息统计。
for(Uint32 x = 0; x < qtssSvrNumParams; x++)
QTSSDictionaryMap::GetMap(QTSSDictionaryMap::kServerDictIndex)->
SetAttribute(x, sAttributes[x].fAttrName, sAttributes[x].fFuncPtr,
sAttributes[x].fAttrDataType, sAttributes[x].fAttrPermission);
for(Uint32 y = 0; y < qtssConnectionNumParams; y++)
QTSSDictionaryMap::GetMap(QTSSDictionaryMap::kQTSSConnectedUserDictIndex)->
SetAttribute(y, sConnectedUserAttributes[y].fAttrName,
sConnectedUserAttributes[y].fFuncPtr,
sConnectedUserAttributes[y].fAttrDataType, sConnectedUserAttributes[y].fAttrPermission);
// write out a premade server header
... ...
（3）、QTSServerInterface::SetValueComplete()
QTSSDictionary::SetValueComplete 函数是虚函数，对于继承类QTSServerInterface 来说，该函数主
要是处理设置qtssSvrState 属性的情况。
对于所有注册了kStateChangeRole 的模块，都将会调用CallDispatch 函数，执行具体模块的处理函
数。
? QTSServer
属于Server core 一部分。处理server 的startup 和shutdown。
该类继承自QTSServerInterface 类。下面是一些成员函数的分析：
（1）、Initialize()
在startServer 函数创建sServer 对象后，该函数被调用。
this->InitCallbacks(); // 初始化sCallbacks
// Dictionary Initialization
QTSSModule::Initialize(); // 调用SetAttribute Setup all the dictionary stuff，下同
QTSServerPrefs::Initialize();
QTSSMessages::Initialize();
// 初始化headerFormatter、noServerInfoHeaderFormatter、调用SetAttribute。
RTSPRequestInterface::Initialize();
RTSPSessionInterface::Initialize();
RTPSessionInterface::Initialize();
RTPStream::Initialize();
RTSPSession::Initialize(); //初始化sHTTPResponseHeaderPtr、
sHTTPResponseNoserverHeaderPtr
QTSSFile::Initialize();
QTSSUserProfile::Initialize();
// STUB SERVER INITIALIZATION
// Construct stub versions of the prefs and message dictionaries。
// QTSServerPrefs 类用来管理QTSS 的配置信息
fSrvrPrefs = new QTSServerPrefs(inPrefsSource, false);
fSrvrMessages = new QTSSMessages(inMessagesSource);
QTSSModuleUtils::Initialize(fSrvrMessages, this, QTSServerInterface::GetErrorLogStream());
// Create Global Objects
// 这两个类的构建函数基本为空
fSocketPool = new RTPSocketPool();
fRTPMap = new OSRefTable(kRTPSessionMapSize);
加载Error Log Module
// 在startServer 函数里已经调用了SocketUtils::Initialize，关于网络及socket 的一些数据
// 已经被收集。
this->SetDefaultIPAddr();
// Record Startup Time
fStartupTime_UnixMilli = OS::Milliseconds();
fGMTOffset = OS::GetGMTOffset();
// Begin Listening
// 见下面的分析。
this->CreateListeners();
（2）CreateListeners()
参数inPortOverride 是由main.cpp 的thePort 传进来（thePort 是指RTSP Server 的监听端口，缺
省为0，可以通过-p 参数来指定）。
根据系统的IP 地址数目和端口数目，创建thePortTrackers 数组，记录IP 地址和端口号。
将thePortTrackers 数组的每一项和fListeners 的比较，如果发现有IP 地址和端口号均相同的一
项，将thePortTrackers 相应项的fNeedsCreating 设为false，并将fListeners 这一项的指针保存
到新创建的newListenerArray 数组。
重新遍历thePortTrackers 数组，处理fNeedsCreating 为true 的项：
创建RTSPListenerSocket 类对象，并保存到newListenerArray 数组，并调用该对象的
Initialize 成员函数。（注意：这里调用的Initialize 函数实际上是
TCPListenerSocket::Initialize，在这个函数里会对socket（流套接字）执行open、bind、
listen 等操作，注意这里绑定的IP 地址缺省为0<在配置文件里对应bind_ip_addr 项>，表示监
听所有地址的连接。绑定的Port 缺省为7070、554、8000、8001<在配置文件里对应rtsp_port 项
>）
如果CreateListeners 的参数startListeningNow 为true，则start listening（这部分我们会
在QTSServer::StartTasks 成员函数里描述）
把fListeners 里包含有但是newListenerArray 里没有（即不再需要的）的监听撤销掉。
最后，设置属性（注意这里调用的是SetValue 函数）：
fListeners = newListenerArray; fNumListeners = curPortIndex;
this->SetValue(qtssSvrRTSPPorts, portIndex, &thePort, sizeof(thePort),
QTSSDictionary::kDontObeyReadOnly);
this->SetNumValues(qtssSvrRTSPPorts, portIndex);
（3）、InitModules()
// 打开module 所在目录，针对该目录下的所有文件调用CreateModule 创建模块。
// 在startServer 调用InitModules 从而又调用LoadModules 的这个情景中，加载了
// QTSSHomeDirectoryModule、QTSSRefMovieModule 这两个模块。
LoadModules（fSrvrPrefs）；
// 加载一些已编入的模块。我们会分析QTSSReflectorModule、QTSSRelayModule 模块的加载过程。
LoadCompiledInmodules();
this->BuildModuleRoleArrays();
处理DSS 系统log、message 等方面的初始化。
this->DoInitRole()；
（4）、CreateModule()
通过创建一个模块对象、调用该模块的SetupModule 函数、调用QTSServer::AddModule 函数这三个步
骤来完成创建加载模块的过程。
（5）、DoInitRole()
theInitParams.initParams.inServer = this; theInitParams.initParams.inPrefs = fSrvrPrefs;
theInitParams.initParams.inMessages = fSrvrMessages;
theInitParams.initParams.inErrorLogStream = &sErrorLogStream;
theModuleState.curRole = QTSS_Initialize_Role; theModuleState.curTask = NULL;
OSThread::SetMainThreadData(&theModuleState);
// Add the OPTIONS method as the one method the server handles by default (it handles
// it internally). Modules that handle other RTSP methods will add
(void)this->SetValue(qtssSvrHandledMethods, 0, &theOptionsMethod,
sizeof(theOptionsMethod));
// 对于那些支持Initialize Role 的模块，通过它们的CallDispatch 函数来调用具体的Initialize
// 函数。实际上这也给各个模块（包括用户自定义的模块）一个执行初始化动作的机会。
// 很多模块都支持Init Role！！！需要一个个分析！！！
for(x=0; x<QTSServerInterface::GetNumModulesInRole(QTSSModule::kInitializeRole); x++) {
QTSSModule* theModule = QTSServerInterface::GetModule(QTSSModule::kInitializeRole,
x);
theInitParams.initParams.inModule = theModule; theModuleState.curModule =
theModule;
QTSS_Error theErr = theModule->CallDispatch(QTSS_Initialize_Role, &theInitParams);
if (theErr != QTSS_NoErr) {... ...}
}
this->SetupPublicHeader();
OSThread::SetMainThreadData(NULL);
（6）、SetupPublicHeader()
// After the Init role, all the modules have reported the methods that they handle.
// So, we can prune this attribute for duplicates, and construct a string to use in the
// Public: header of the OPTIONS response
// 将各个模块登记的支持方法信息汇总一起。在RTSPSession 处理OptionMethod 时，会将这些信
// 息发送出去。
Bool16 theUniqueMethods[qtssNumMethods + 1];
::memset(theUniqueMethods, 0, sizeof(theUniqueMethods));
for (UInt32 y = 0; this->GetValuePtr(qtssSvrHandledMethods, y, (void**)&theMethod,
&theLen) == QTSS_NoErr; y++)
theUniqueMethods[*theMethod] = true;
（7）、StartTasks()
fRTCPTask = new RTCPTask();
fStatsTask = new RTPStatsUpdaterTask();
// Start listening
for (Uint32 x = 0; x < fNumListeners; x++)
fListeners[x]->RequestEvent(EV_RE);
（8）、SetupUDPSockets()
function finds all IP addresses on this machine, and binds 1 RTP/RTCP socket pair to a
port pair on each address.
SocketUtils::GetNumIPAddrs()返回2，包括本机的ip、loop 地址。
for (UInt32 theNumPairs = 0; theNumPairs < SocketUtils::GetNumIPAddrs(); theNumPairs++)
{
// 在QTSServer::Initialize 函数里，fSocketPool=new RTPSocketPool();
// RTPSocketPool 是UDPSocketPool 的继承类，它们的构建函数均为空。
// 基于同一个ip，创建一个socket 对。
UDPSocketPair* thePair=fSocketPool->CreateUDPSocketPair(SocketUtils::GetIPAddr(theNumPairs), 0);
// 申请监听这两个socket 端口
thePair->GetSocketA()->RequestEvent(EV_RE); thePair->GetSocketB()->RequestEvent(EV_RE);
? RTPSocketPool、UDPSocketPool
UDPSocketPool: Object that creates & maintains UDP socket pairs in a pool.
（1）、UDPSocketPool::CreateUDPSocketPair
... ...
while((!foundPair) && (curPort < kHighestUDPPort))
{
socketBPort = curPort +1; // make socket pairs adjacent to one another
theElem = ConstructUDPSocketPair(); // 创建一个udp socket pair
// 创建数据报socket 端口
theElem->fSocketA->Open(); theElem->fSocketB->Open();
// Set sokcet options on these new sockets，主要是设置socket buf size
this->SetUDPSocketOptions(theElem);
// 在两个socket 端口上执行bind 操作，两个port 相差1.
theElem->fSocketA->Bind(inAddr, curPort); theElem->fSocketB->Bind(inAddr, socketBPort);
// 利用UDPSocketPair 的fElem 成员插入fUDPQueue 队列。
fUDPQueue.EnQueue(&theElem->fElem); theElem->fRefCount++;
... ...
}
（2）、RTPSocketPool::ConstructUDPSocketPair
Task* theTask = ((QTSServer*)QTSServerInterface::GetServer())->fRTCPTask;
// construct a pair of UDP sockets, the lower one for RTP data (outgoing only, no demuxer
// necessary), and one for RTCP data (incoming, so definitely need a demuxer).
// These are nonblocking sockets that DON'T receive events (we are going to poll for data)
// They do receive events - we don't poll from them anymore
// 在RTCPTask 的Run 函数里，会寻找带有Demuxer 的socket，将接收到的数据交由Demuxer 相联
// 系的Task 进行处理。
// 注意这里传入的是fRTCPTask!
return NEW UDPSocketPair( NEW UDPSocket(theTask, Socket::kNonBlockingSocketType),
NEW UDPSocket(theTask, UDPSocket::kWantsDemuxer | Socket::kNonBlockingSocketType));
（3）、RTPSocketPool::SetUDPSocketOptions(UDPSocketPair* inPair)
// Apparently the socket buffer size matters even though this is UDP and being used for
// sending... on UNIX typically the socket buffer size doesn't matter because the packet
// goes right down to the driver. On Win32 and linux, unless this is really big, we get
// packet loss.
// Socket A 用来发送RTP data，通过setsockopt 将发送buf 设为256K
inPair->GetSocketA()->SetSocketBufSize(256 * 1024);
// Socket B 用来接收RTCP data，注意这几个socket 端口的buffer size：
// TCPListenerSocket 的rcv buf size 为96K、TCPListenerSocket accept 后返回的socket snd
// buf size 为256K。
// RTP data Socket snd buf size 为256K、RTCP data Socket rcv buf size 为768K。
// Always set the Rcv buf size for the RTCP sockets. This is important because the
// server is going to be getting many many acks.
// 获得用于RTCP 的rcv buf size 大小，缺省为768K，在配置文件中对应rtcp_rcv_buf_size 项
// In case the rcv buf size is too big for the system, retry, dividing the requested size
// by 2. Until it works, or until some minimum value is reached.
while ((theErr != OS_NoErr) && (theRcvBufSize > 32))
{
theErr = inPair->GetSocketB()->SetSocketRcvBufSize(theRcvBufSize * 1024);
if (theErr != OS_NoErr) theRcvBufSize >>= 1;
}
? UDPSocket
Socket 的继承类，Socket 是EventContext 的继承类。注意在Socket 的构建函数里，调用了
EventContext 的SetTask 函数，将传入的intask 参数付给EventContext 的fTask 成员。
? UDPSocketPair
（1）、构建函数
UDPSocketPair(UDPSocket* inSocketA, UDPSocket* inSocketB)
: fSocketA(inSocketA), fSocketB(inSocketB),fRefCount(0),fElem()
{fElem.SetEnclosingObject(this);}
? RTPPacketResender
RTPPacketResender class to buffer and track re-transmits of RTP packets.
the ctor copies the packet data, sets a timer for the packet's age limit and another
timer for it's possible re-transmission.
A duration timer is started to measure the RTT based on the client's ack.
（1）、AddPacket()
AddPacket adds a new packet to the resend queue. This will not send the packet.
可以看到，在RTPStream::ReliableRTPWrite 函数（针对qtssRTPTransportTypeReliableUDP）里，
会调用AddPacket 登记要发送的数据以及到期Drop 的时间。
（2）、AckPacket()
Acks a packet.
可以看到，在RTPStream::ProcessIncomingRTCPPacket 函数里，针对
qtssRTPTransportTypeReliableUDP 类型的传输，会调用AckPacket 将对应包删除。
（3）、ResendDueEntries()
Resends outstanding packets in the queue。
可以看到，在RTPStream::ReliableRTPWrite 函数（针对qtssRTPTransportTypeReliableUDP）里，会调
用该函数，重发或者丢弃那些过期的RTP 包。
? RTPStream
Represents a single client stream (audio, video, etc).
Control API is similar to overall session API.
Contains all stream-specific data & resources, used by Session when it wants to send out
or receive data for this stream.
This is also the class that implements the RTP stream dictionary for QTSS API.
（1）、Setup()
设置fStreamURLPtr、fLateToleranceInSec、fTransportType、fNetworkMode
// decide whether to overbuffer
根据fTransportType 决定是否调用fSession->GetOverbufferWindow()->TurnOffOverbuffering()
// Check to see if this RTP stream should be sent over TCP.
if(fTransportType == qtssRTPTransportTypeTCP)
{ ... ...}
// This track is not interleaved, so let the session know that all tracks are not
// interleaved. This affects our scheduling of packets
fSession->SetAllTracksInterleaved(false);
// 注意对于播放一个静态媒体文件的audio 流、video 流，客户端的RTPPort、RTCPPort 端口号不
// 同。另外RTP 端口号应该是偶数。
设置fRemoteAddr、fRemoteRTPPort、fRemoteRTCPPort、sourceAddr。
// If the destination address is multicast, we need to setup multicast socket options on
// the sockets. Because these options may be different for each stream, we need a
// dedicated set of sockets
if (SocketUtils::IsMulticastIPAddr(fRemoteAddr))
{
重新调用CreateUDPSocketPair 创建socket 对，并设置socket 属性。
} else
// 从fUDPQueue 队列里根据本地的地址、端口号寻找UDP Socket 对。
// 记得我们以前曾经创建过udp socket 对。
fSockets = QTSServerInterface::GetServer()->GetSocketPool()->
GetUDPSocketPair(sourceAddr, 0, fRemoteAddr, fRemoteRTCPPort);
if(fTransportType == qtssRTPTransportTypeReliableUDP)
{ ... ... }
fLocalRTPPort = fSockets->GetSocketA()->GetLocalPort();
// 设置UDPSocket::fDemuxer::fRemoteAddr、UDPSocket::fDemuxer::fRemotePort。同时调用
// UDPSocket::fDemuxer::fHashTable::Add 添加RTPStream 对象(即：this)
fSockets->GetSocketB()->GetDemuxer()->RegisterTask(fRemoteAddr, fRemoteRTCPPort, this);
（2）、Write()
RTP 包的发送函数，QTSSFileModule::SendPackets 通过调用该函数来完成包的发送。
fSession->GetSessionMutex()->TryLock();
theTime = OS::Milliseconds();
// Data passed into this version of write must be a QTSS_PacketStruct
QTSS_PacketStruct* thePacket = (QTSS_PacketStruct*)inBuffer;
thePacket->suggestedWakeupTime = -1;
theCurrentPacketDelay = theTime – thePacket->packetTransmitTime; // 延时
// Empty the overbuffer window
// Update the bit rate value
// If this is the first write in a write burst, mark beginning.
... ...
if (inFlags & qtssWriteFlagsIsRTCP)
{ ... ...}
else if (inFlags & qtssWriteFlagsIsRTP)
{ // Check to see if this packet fits in the overbuffer window
thePacket->suggestedWakeupTime = fSession->GetOverbufferWindow()->CheckTransmitTime
(thePacket->packetTransmitTime, theTime, inLen);
if(thePacket->suggestedWakeupTime > theTime)
{ fSession->GetSessionMutex()->Unlock(); return QTSS_WouldBlock; }
// Check to make sure our quality level is correct. This function also tells us
// whether this packet is just too old to send
// 在updateQualityLevel 里，只有当inCurrentPacketDelay>fDropAllPacketsForThisStreamDelay
// 才会返回false，表明数据被丢弃。跟配置文件中
// 的"drop_all_packets_delay"、"drop_all_video_delay"相关。
if (this->UpdateQualityLevel(thePacket->packetTransmitTime, theCurrentPacketDelay,
theTime, inLen))
{ // write out in interleave format on the RTSP TCP channel
if (fTransportType == qtssRTPTransportTypeTCP )
this->InterleavedWrite( thePacket->packetData, inLen, outLenWritten, fRTPChannel );
else if (fTransportType == qtssRTPTransportTypeReliableUDP )
// 调用fResender 等处理
// 调用fSockets->GetSocketA()->SendTo
// SocketA 即为完成RTP Data 发送功能的UDP Socket 端口。
this->ReliableRTPWrite(thePacket->packetData, inLen, theCurrentPacketDelay);
else if (inLen > 0)
fSockets->GetSocketA()->SendTo(fRemoteAddr, fRemoteRTPPort,
thePacket->packetData, inLen);
}
if(err == QTSS_NoErr && inLen > 0)
{
// Update statistics if we were actually able to send the data (don't
// update if the socket is flow controlled or some such thing)
... ...
}
}
fSession->GetSessionMutex()->Unlock();
（3）、ProcessIncomingRTCPPacket
curTime = OS::Milliseconds();
if (!fSession->GetSessionMutex()->TryLock()) return;
// no matter what happens (whether or not this is a valid packet) reset the timeouts
fSession->RefreshTimeout();
if (fSession->GetRTSPSession() != NULL) fSession->GetRTSPSession()->RefreshTimeout();
while(currentPtr.Len > 0)
{
// Due to the variable-type nature of RTCP packets, this is a bit unusual... We
// initially treat the packet as a generic RTCPPacket in order to determine its'
// actual packet type. Once that is figgered out, we treat it as its' actual
// packet type
RTCPPacket rtcpPacket;
if (!rtcpPacket.ParsePacket((UInt8*)currentPtr.Ptr, currentPtr.Len))
{ fSession->GetSessionMutex()->Unlock(); return; }
// Increment our RTCP Packet and byte counters for the session.
fSession->IncrTotalRTCPPacketsRecv();
fSession->IncrTotalRTCPBytesRecv( (SInt16) currentPtr.Len);
switch (rtcpPacket.GetPacketType())
{
case RTCPPacket::kReceiverPacketType:
{
RTCPReceiverPacket receiverPacket;
if (!receiverPacket.ParseReceiverReport((UInt8*)currentPtr.Ptr,
currentPtr.Len))
{ fSession->GetSessionMutex()->Unlock(); return;}
this-
>PrintPacketPrefEnabled(currentPtr.Ptr,currentPtr.Len,RTPStream::rtcpRR);
fClientSSRC = rtcpPacket.GetPacketSSRC();
fFractionLostPackets=receiverPacket.GetCumulativeFractionLostPackets();
fJitter = receiverPacket.GetCumulativeJitter();
UInt32 curTotalLostPackets = receiverPacket.GetCumulativeTotalLostPackets();
// Workaround for client problem. Sometimes it appears to report a
// bogus lost packet count. Since we can't have lost more packets
// than we sent, ignore the packet if that seems to be the case.
if(curTotalLostPackets-fTotalLostPackets<=fPacketCount - fLastPacketCount)
{ 设置fCurPacketLostINRTCPInterval、fTotalLostPackets、
fPacketCountInRTCPInterval、fLastPacketCount。}
} break;
case RTCPPacket::kAPPPacketType:
{
Check and see if this is an Ack packet. If it is, update the UDP
Resender
If it isn't an ACK, assume its the qtss APP packet。
}
... ...
}
currentPtr.Ptr += (rtcpPacket.GetPacketLength() * 4) + 4;
currentPtr.Len -= (rtcpPacket.GetPacketLength() * 4) + 4;
}
// Invoke the RTCP modules, allowing them to process this packet
// 目前系统中的QTSSProxyModule(This module is intended to be used in a stripped down
// version of QTSS/DSS in order to handle firewall proxy behaviour for the RTP
// protocol.)、QTSSFlowControlModule(Uses information in RTCP packers to throttle back
// the server when it's pumping out too much data to a given client)
调用注册QTSS_RTCPProcess_Role 模块的处理函数。
fSession->GetSessionMutex()->Unlock();
? RTPSessionInterface
（1）、构建函数
... ...
fTimeoutTask.SetTask(this); fUniqueID = (UInt32)atomic_add(&sRTPSessionIDCounter, 1);
fQualityUpdate = fUniqueID;
fTimeout = QTSServerInterface::GetServer()->GetPrefs()->GetRTPTimeoutInSecs() * 1000;
? RTPSession
RTPSession represents an, well, an RTP session. The server creates one of these when a
new client connects, and it lives for the duration of an RTP presentation. It contains
all the resources associated with that presentation, such as RTPStream objects. It also
provides an API for manipulating a session (playing it, pausing it, stopping it, etc)
It is also the active element, ie. it is the object that gets scheduled to send out &
receive RTP & RTCP packets
（1）、AddStream()
// Create a new SSRC for this stream. This should just be a random number unique to all
// the streams in the session
创建一个和当前session 所有stream 的fSsrc 不同的随机数。
*outStream = NEW RTPStream(theSSRC, this);
// 调用RTPStream::Setup 函数
(*outStream)->Setup(request, inFlags);
// If the stream init succeeded, then put it into the array of setup streams
this->SetValue(qtssCliSesStreamObjects, this->GetNumValues(qtssCliSesStreamObjects),
outStream, sizeof(RTPStream*), QTSSDictionary::kDontObeyReadOnly);
fHasAnRTPStream = true;
（2）、Play()
// What time is this play being issued at?
fLastBitRateUpdateTime = fNextSendPacketsTime = fPlayTime = OS::Milliseconds();
if (fIsFirstPlay) fFirstPlayTime = fPlayTime;
fAdjustedPlayTime = fPlayTime - ((SInt64)(request->GetStartTime() * 1000));
// for RTCP Srs, we alse need to store the play time in NTP
fNTPPlayTime = OS::TimeMilli_To_1900Fixed64Secs(fPlayTime);
// we are definitely playing now, so schedule the object.
fState = qtssPlayingState; fIsFirstPlay = false;
// 调整fNumRTPPlayingSessions
QTSServerInterface::GetServer()-> AlterRTPPlayingSessions(1);
// 设置theWindowSize
... ...
this->GetBandwidthTracker()->SetWindowSize(theWindowSize);
this->GetOverbufferWindow()->ResetOverBufferWindow();
// Go through all the streams, setting their thinning params.
调用(*theStream)->SetThinningParams();
// Set the size of the RTSPSession's send buffer to an appropriate max size based on the
// bitrate of the movie. This has 2 benefits:
// 1) Each socket normally defaults to 32K. A smaller buffer prevents the system from
// getting buffer starved if lots of clients get flow-controlled
// 2) We may need to scale up buffer sizes for high-bandwidth movies in order to maximize
// thruput, and we may need to scale down buffer sizes for low-bandwidth movies to
// prevent us from buffering lots of data that the client can't use
// If we don't know any better, assume maximum buffer size.
// 注意：这里设置的是RTSPSession 的socket，即TCP socket。
thePrefs = QTSServerInterface::GetServer()->GetPrefs();
theBufferSize = thePrefs->GetMaxTCPBufferSizeInBytes();
if (this->GetMovieAvgBitrate() > 0)
{
// We have a bit rate... use it.
realBufferSize = this->GetMovieAvgBitrate() * thePrefs->GetTCPSecondsToBuffer();
theBufferSize = (Uint32)realBufferSize >> 3;
theBufferSize = this->PowerOf2Floor(theBufferSize);
// This is how much data we should buffer based on the scaling factor... if it is
// lower than the min, raise to min. Same deal for max buffer size
// 缺省值为配置文件中的max_tcp_buffer_size(200000)、min_tcp_buffer_size(8192)
if (theBufferSize < thePrefs->GetMinTCPBufferSizeInBytes())
theBufferSize = thePrefs->GetMinTCPBufferSizeInBytes();
if (theBufferSize > thePrefs->GetMaxTCPBufferSizeInBytes())
theBufferSize = thePrefs->GetMaxTCPBufferSizeInBytes();
}
fRTPSession->GetSocket()->SetSocketBufSize(theBufferSize);
// 发送信号，RTPSession::Run 将会被运行。
this->Signal(Task::kStartEvent);
（3）、Run
在RTPSession::Play 函数调用Signal 后，该函数会被运行
... ...
// if we have been instructed to go away, then let's delete ourselves
if ((events & Task::kKillEvent) || (events & Task::kTimeoutEvent) ||
(fModuleDoingAsyncStuff))
{ ... ...}
// if the stream is currently paused, just return without doing anything. We'll get woken
// up again when a play is issued
if ((fState == qtssPausedState) || (fModule == NULL))
return 0; // 返回的是0！
// Make sure to grab the session mutex here, to protect the module against RTSP requests
// coming in while it's sending packets
{ OSMutexLocker locker(&fSessionMutex);
// just make sure we haven't been scheduled before our scheduled play time. If so,
// reschedule ourselves for the proper time. (if client sends a play while we are
// already playing, this may occur)
theParams.rtpSendPacketsParams.inCurrentTime = OS::Milliseconds();
if (fNextSendPacketsTime > theParams.rtpSendPacketsParams.inCurrentTime)
// Send retransmits if we need to
for (int streamIter = 0; this->GetValuePtr(qtssCliSesStreamObjects, streamIter,
(void**)&retransStream, &retransStreamLen) == QTSS_NoErr; streamIter++)
if (retransStream && *retransStream)
(*retransStream)->SendRetransmits();
theParams.rtpSendPacketsParams.outNextPacketTime = fNextSendPacketsTime -
theParams.rtpSendPacketsParams.inCurrentTime;
} else {
if ((theParams.rtpSendPacketsParams.inCurrentTime -
fLastBandwidthTrackerStatsUpdate) > 1000)
this->GetBandwidthTracker()->UpdateStats();
theParams.rtpSendPacketsParams.outNextPacketTime = 0;
// Async event registration is definitely allowed from this role.
fModuleState.eventRequested = false;
// 这里的fModule 是在RTSPSession::Run 函数里调用
// fRTPSession->SetPacketSendingModule 设置为找到的注册了Role 的模块。
// QTSSFileModule 注册了QTSS_RTPSendPackets_Role 的处理。
fModule->CallDispatch(QTSS_RTPSendPackets_Role, &theParams);
// make sure not to get deleted accidently!
if (theParams.rtpSendPacketsParams.outNextPacketTime < 0)
theParams.rtpSendPacketsParams.outNextPacketTime = 0;
fNextSendPacketsTime = theParams.rtpSendPacketsParams.inCurrentTime +
theParams.rtpSendPacketsParams.outNextPacketTime;
}
// Make sure the duration between calls to Run() isn't greater than the max retransmit
// delay interval.
// 分别对应配置文件中的“max_retransmit_delay(500)”、“send_interval(50)”项。
// max_retransmit_delay: maximum interval between when a retransmit is supposed to be
// sent and when it actually gets sent. Lower values means
// smoother flow but slower server performance.
// send_interval: the minimum time the server will wait between sending packet
// data to a client.
theRetransDelayInMsec = QTSServerInterface::GetServer()->GetPrefs()->GetMaxRetransmitDelayInMsec();
theSendInterval = QTSServerInterface::GetServer()->GetPrefs()->GetSendIntervalInMsec();
// We want to avoid waking up to do retransmits, and then going back to sleep for like, 1
// msec. So, only adjust the time to wake up if the next packet time is greater than the
// max retransmit delay + the standard interval between wakeups.
if (theParams.rtpSendPacketsParams.outNextPacketTime > (theRetransDelayInMsec + theSendInterval))
theParams.rtpSendPacketsParams.outNextPacketTime = theRetransDelayInMsec;
return theParams.rtpSendPacketsParams.outNextPacketTime; // 指定时间后被再度运行
? RTSPRequestStream
Provides a stream abstraction for RTSP. Given a socket, this object can read in data
until an entire RTSP request header is available. (do this by calling ReadRequest). It
handles RTSP pipelining (request headers are produced serially even if multiple headers
arrive simultaneously), & RTSP request data.
（1）、ReadRequest
while(true)
{ Uint32 newOffset = 0;
// If this is the case, we already HAVE a request on this session, and we now are
// done with the request and want to move onto the next one. The first thing we
// should do is check whether there is any lingering data in the stream. If there
// is, the parent session believes that is part of a new request.
if(fRequestPtr != NULL)
{
}
// We don't have any new data, so try and get some
if(newOffset == 0)
{
if(fRetreatBytes > 0)
{
// This will be true if we've just snarfed another input stream, in
// which case the encoded data is copied into our request buffer,
// and its length is tracked in fRetreatBytes. If this is true, just
// fall through and decode the data.
newOffset = fRetreatBytes; fRetreatBytes = 0;
} else {
// We don't have any new data, get some from the socket...
// 注意我们的socket 端口是non blocking
sockErr = fSocket->Read(&fRequestBuffer[fCurOffset],
(kRequestBufferSizeInBytes-fCurOffset) -1,
&newOffset);
// assume the client is dead if we get an error back
if(sockErr == EAGAIN) return QTSS_NoErr;
if(sockErr != QTSS_NoErr) return sockErr;
}
if(fDecode)
{
base64 decode；
} else fRequest.Len += newOffset;
fCurOffset += newOffset;
}
// see if this is an interleaved data packet
if ('$' == *(fRequest.Ptr))
{
if(fRequest.Len < 4) continue;
Uint16* dataLenP = (Uint16*)fRequest.Ptr;
Uint32 interleavedPacketLen = ntohs(dataLenP[1]) + 4;
if(interleavedPacketLen > fRequest.Len) continue;
// put back any data that is not part of the header
fRetreatBytes += fRequest.Len - interleavedPacketLen;
fRequest.Len = interleavedPacketLen;
fRequestPtr = &fRequest; fIsDataPacket = true;
return QTSS_RequestArrived;
}
fIsDataPacket = false;
if(fPrintRTSP)
打印RTSP 包
// use a StringParser object to search for a double EOL, which signifies the end
// of the header.
weAreDone = false; headerParser(&fRequest); lcount = 0;
while (headerParser.GetThruEol(NULL))
{ ... ...}
// weAreDone means we have gotten a full request
// 应该是指收到最后一个消息头
if(weAreDone)
{
// put back any data that is not part of the header
fRequest.Len -= headerParser.GetDataRemaining();
fRetreatBytes += headerParser.GetDataRemaining();
fRequestPtr = &fRequest;
return QTSS_RequestArrived;
}
// check for a full buffer
if (fCurOffset == kRequestBufferSizeInBytes - 1)
{
fRequestPtr = &fRequest;
return E2BIG;
}
}
? RTSPResponseStream
Object that provides a "buffered WriteV" service. Clients can call this function to write
to a socket, and buffer flow controlled data in different ways.
It is derived from StringFormatter, which it uses as an output stream buffer. The buffer
may grow infinitely.
（1）、构建函数
RTSPResponseStream(TCPSocket* inSocket, TimeoutTask* inTimeoutTask)
: ResizeableStringFormatter(fOutputBuf, kOutputBufferSizeInBytes),
fSocket(inSocket), fBytesSentInBuffer(0), fTimeoutTask(inTimeoutTask),fPrintRTSP(false) {}
? RTSPRequest
This class encapsulates a single RTSP request. It stores the meta data associated with a
request, and provides an interface (through its base class) for modules to access request
information, It divides the request into a series of states.
State 1: At first, when the object is constructed or right after its Reset function is
called, it is in an uninitialized state.
State 2: Parse() parses an RTSP header. Once this function returns, most of the request-
-related query functions have been setup. (unless an error occurs)
State 3: GetHandler() uses the request information to create the proper request Handler
object for this request. After that, it is the Handler object's responsibilty to
process the request and send a response to the client.
RTSPRequest是RTSPRequestInterface的继承类。
? RTSPSession
Represents an RTSP session , which I define as a complete TCP connection lifetime, from
connection to FIN or RESET termination. This object is the active element that gets
scheduled and gets work done. It creates requests and processes them when data arrives.
When it is time to close the connection it takes care of that.
class RTSPSession : public RTSPSessionInterface
class RTSPSessionInterface : public QTSSDictionary, public Task
RTSPSession的状态机：
enum
{
kReadingRequest = 0,
kFilteringRequest = 1,
kRoutingRequest = 2,
kAuthenticatingRequest = 3,
kAuthorizingRequest = 4,
kPreprocessingRequest = 5,
kProcessingRequest = 6,
kSendingResponse = 7,
kPostProcessingRequest = 8,
kCleaningUp = 9,
// states that RTSP sessions that setup RTSP
// through HTTP tunnels pass through
kWaitingToBindHTTPTunnel = 10, // POST or GET side waiting to be joined with it's matching half
kSocketHasBeenBoundIntoHTTPTunnel = 11, // POST side after attachment by GET side (its dying)
kHTTPFilteringRequest = 12, // after kReadingRequest, enter this state
kReadingFirstRequest = 13, // initial state - the only time we look for an HTTP tunnel
kHaveNonTunnelMessage = 14 // we've looked at the message, and its not an HTTP tunnle message
};
RTSP 的消息格式:
请求消息:
方法URI RTSP 版本CR LF
消息头CR LF CR LF
消息体CR LF
回应消息:
RTSP 版本状态码解释CR LF
消息头CR LF CR LF
消息体CR LF
（1）、构建函数
初始化成员
（2）、ParseProxyTunnelHTTP函数
检查是否是Http连接，如果是，返回true。
if it's an HTTP request parse the interesing parts from the request
- check for GET or POST, set fHTTPMethod
- checck for HTTP protocol, set fWasHTTPRequest
- check for SessionID header, set fProxySessionID char array
- check for accept "application/x-rtsp-tunnelled.
... ...
if ( fFoundValidAccept && *fProxySessionID && fWasHTTPRequest )
isHTTPRequest = true;
return isHTTPRequest;
（3）、PreFilterForHTTPProxyTunnel函数
"pre" filter the request looking for the HHTP Proxy tunnel HTTP requests, merge the 2
sessions into one, let the donor Session die.
// returns true if it's an HTTP request that can tunnel
if(!this->ParseProxyTunnelHTTP()) return QTSS_NoErr;
对http连接的处理，暂不做分析！
（4）、Run函数
当一个RTSP端口有数据时，EventContext::ProcessEvent函数会调用Signal函数，TaskThread会调用
RTSPSession::Run函数。见TCPListenerSocket::ProcessEvent函数的分析。
OSThreadDataSetter theSetter(&fModuleState, NULL);
while (this->IsLiveSession())
{
// RTSP Session state machine. There are several well defined points in an RTSP
// request where this session may have to return from its run function and wait
// for a new event. Because of this, we need to track our current state and return
// to it.
case kReadingFirstRequest: // 初始状态
{
// 返回QTSS_NoErr意味着所有数据已经从Socket中读出，但尚不能构成一个完整
// 的请求，因此必须等待更多的数据到达
// 我们从ReadRequest代码可以知道，只有当对socket端口recv返回EAGAIN时，
// ReadRequest才会返回QTSS_NoErr。
if ((err = fInputStream.ReadRequest()) == QTSS_NoErr)
{
fInputSocketP->RequestEvent(EV_RE); // 重新申请监听
return 0;
}
if ((err != QTSS_RequestArrived) && (err != E2BIG))
{ break; } // 注意：这里没有再申请继续监听。
if (err == QTSS_RequestArrived) fState = kHTTPFilteringRequest;
// If we get an E2BIG, it means our buffer was overfilled. In that case, we
// can just jump into the following state, and the code their does a check
// for this error and returns an error.
if (err == E2BIG) fState = kHaveNonTunnelMessage;
} continue; // 注意：这里调用continue
case kHTTPFilteringRequest:
{
// assume it's not a tunnel setup message prefilter will set correct tunnel
// state if it is.
fState = kHaveNonTunnelMessage;
// 对于非Http连接的情况，会返回QTSS_NoErr。但是返回QTSS_NoErr，并不表示
// 一定是非Http连接。而且对于Http连接（RTSP经过Http代理）情况，
// PreFilterForHTTPProxyTunnel可能会更改fState值。
preFilterErr = this->PreFilterForHTTPProxyTunnel();
if(preFilterErr == QTSS_NoErr) continue;
else return -1;
}
case kHaveNonTunnelMessage:
{
fRequest = NEW RTSPRequest(this);
fRoleParams.rtspRequestParams.inRTSPRequest = fRequest;
fRoleParams.rtspRequestParams.inRTSPHeaders = fRequest->GetHeaderDictionary();
// We have an RTSP request and are about to begin processing. We need to
// make sure that anyone sending interleaved data on this session won't
// be allowed to do so until we are done sending our response
// We also make sure that a POST session can't snarf in while we're
// processing the request.
// 通过锁，防止在发送请求回复过程中，有另外的数据被安插发送
fReadMutex.Lock(); fSessionMutex.Lock();
// The fOutputStream's fBytesWritten counter is used to count the # of
// bytes for this RTSP response. So, at this point, reset it to 0 (we can
// then just let it increment until the next request comes in)
fOutputStream.ResetBytesWritten();
如果err == E2BIG或者QTSS_BadArgument，调用SendErrorResponse, fState赋值为
kPostProcessingRequest。否则fState赋值为kFilteringRequest。
}
case kFilteringRequest:
{
// We received something so auto refresh, The need to auto refresh is
// because the api doesn't allow a module to refresh at this point
// 重置fTimeoutTask的到时时间
fTimeoutTask.RefreshTimeout();
// Before we even do this, check to see if this is a *data* packet, in
// which case this isn't an RTSP request, so we don't need to go through
any
// of the remaining steps
// 在readRequest函数里，只有碰到“$”，才会认为是interleaved packet
if (fInputStream.IsDataPacket())
{
// 在handleIncomingDataPacket里，除了调用RTPSession的
// ProcessIncomingInterleavedData函数外，还会调用已注册
// QTSS_RTSPIncomingData_Role模块的处理函数。(系统的
// QTSSReflectorModule模块提供该Role的处理)
// 这里可以进行二次开发！
this->HandleIncomingDataPacket();
fState = kCleaningUp; break;
}
设置filter param block theFilterParams;
调用已注册QTSS_RTSPFilter_Role模块的处理函数(系统的QTSSRelayModule模块、
QTSSMP3StreamingModule模块(Handle ShoutCast/IceCast-style MP3
streaming.)、QTSSRefMovieModule模块(A module that serves an
RTSP text ref movie from an HTTP request.)、QTSSAdminModule模块(A module
that uses the information available in the server to present a web page
containing that information.)、QTSSWebStatsModule模块(A module that uses
the stats information available in the server to present a web page
containing that information.)、QTSSWebDebugModule模块(A module that uses
the debugging information available in the server to present a web page
containing that information.)、QTSSDemoSMILModule模块(?)、
QTSSHttpFileModule模块(A module for HTTP file transfer of files and for
on-the-fly ref movie creation.)提供该Role的处理)，可以添加二次开发模块！
// 根据fBytesWritten来判断，在StringFormatter::Put函数里增加了
// fBytesWritten计数，但是实际上并没有通过socket发送？？？
if (fRequest->HasResponseBeenSent())
{ fState = kPostProcessingRequest; break; }
if (fSentOptionsRequest && this->ParseOptionsResponse())
{ ... ...fState = kSendingResponse; break; }
else //this is a normal request,so parse it and get the RTPSession.
// 建立用于管理数据传输的RTPSession类对象，根据请求消息中的方法
// 做处理。
this->SetupRequest();
if (fRequest->HasResponseBeenSent())
{ fState = kPostProcessingRequest; break; }
fState = kRoutingRequest;
}
case kRoutingRequest:
{
调用注册了QTSS_RTSPRoute_Role处理的模块的处理函数(系统的QTSSRelayModule模
块、QTSSReflectorModule模块、QTSSHomeDirectoryModule模块提供了该Role的处
理)。
// SetupAuthLocalPath must happen after kRoutingRequest and before
// kAuthenticatingRequest placed here so that if the state is shifted to
// kPostProcessingRequest from a response being sent then the
// AuthLocalPath will still be set.
if (fRequest->HasResponseBeenSent())
{ fState = kPostProcessingRequest; break; }
if(fRequest->SkipAuthorization())
{ ... ...}
else fState = kAuthenticatingRequest;
}
case kAuthenticatingRequest:
{
QTSS_RTSPMethod method = fRequest->GetMethod();
if (method != qtssIllegalMethod) do
{ ... ...} while(false);
if(fRequest->GetAuthScheme() == qtssAuthNone)
{ ... ...}
调用二次开发的安全模块(QTSS_RTSPAuthenticate_Role)，主要用于客户身份验证
以及其他规则的处理(系统的QTSSAccessModule模块(Module that handles
authentication and authorization independent of the file
system)、QTSSODAuthModule模块(This is a modified version of the
QTSSAccessModule also released with QTSS 2.0. It has been modified to
shrink
the linespacing so that the code can fit on slides. Also, this module
issues
redirects to an error movie.)提供了该Role的处理)。
// 有两种认证策略: basic authentication、digest authentication
// If authenticaton failed, set qtssUserName in the qtssRTSPReqUserProfile
// attribute to NULL and clear out the password and any groups that have
// been set.
this->CheckAuthentication();
if (fRequest->HasResponseBeenSent())
{ fState = kPostProcessingRequest; break; }
fState = kAuthorizingRequest;
}
case kAuthorizingRequest:
{
调用注册QTSS_RTSPAuthorize_Role模块的处理函数，如果失败，则发送回复并跳出
循环(系统的QTSSSpamDefenseModule模块(Protects the server against denialof-
service attacks by only allowing X number of RTSP connections from a
certain IP address)、QTSSFilePrivsModule模块(Module that handles and file
system authorization)、QTSSReflectorModule模块、QTSSHomeDirectoryModule模
块、
QTSSAccessModule模块、QTSSAdminModule模块、QTSSDemoModule模块(This is a
modified version of the QTSSAccessModule also released with QTSS 2.0. It
has
been modified to shrink the linespacing so that the code can fit on slides.
Also, this module issues redirects to an error movie.)、QTSSODAuthModule模
块
提供了该Role的处理)。
this->SaveRequestAuthorizationParams(fRequest);
if(!allowd) // 怎么会进入这个分支？？？
{ ... ...}
if (fRequest->HasResponseBeenSent())
{ fState = kPostProcessingRequest; break; }
fState = kPreprocessingRequest;
... ...
}
case kPreprocessingRequest:
{
调用注册QTSS_RTSPPreProcessor_Role模块的处理函数，注意系统也提供了支持这
些role的模块(系统的QTSSReflectorModule模块、QTSSSplitterModule模块、
QTSSRTPFileModule模块(Content source module that uses the QTFileLib to
serve Hinted QuickTime files to clients.)、QTSSRawFileModule模块(A module
that returns the entire contents of a file to the client. Only does this if
the suffix of the file is .raw)提供了该Role的处理)。
注意：QTSSRTPFileModule和QTSSRawFileModule并没有加载进系统！！！
if (fRequest->HasResponseBeenSent())
{ fState = kPostProcessingRequest; break; }
fState = k```;
}
case kProcessingRequest:
{
调用注册QTSS_RTSPRequest_Role模块的处理函数，注意系统也提供了支持这
些role的模块(系统的QTSSFileModule模块(Content source module that uses the
QTFileLib to serve Hinted QuickTime files to clients.)、QTSSProxyModule模块
提供了该Role的处理)。
fState = kPostProcessingRequest;
}
case kPostProcessingRequest:
{
调用注册QTSS_RTSPPostProcessor_Role模块的处理函数，注意系统也提供了支持这
些role的模块(系统的QTSSRelayModule模块、QTSSAccessLogModule模块提供了该
Role的处理)。
fState = kSendingResponse;
}
case kSendingResponse:
{
... ...
// 调用fSocket->Send，将在fOutputStream中尚未发出的请求响应通过Socket端
// 口完全发送出去，如果还有数据没有发送出去，返回EAGAIN。
err = fOutputStream.Flush();
if (err == EAGAIN)
{
// If we get this error, we are currently flow-controlled and
should
// wait for the socket to become writeable again
fSocket.RequestEvent(EV_WR);
// 因为前面执行了“fReadMutex.Lock(); fSessionMutex.Lock();”以禁止
在
// 处理请求的过程中，有另外的数据在同一个session中发送。
// 所以这里指定让后续的处理继续由同一个线程完成。
this->ForceSameThread();
return 0;
} else if (err != QTSS_NoErr) break;
fState = kCleaningUp;
case kCleaningUp:
{
// Cleaning up consists of making sure we've read all the incoming Request
// Body data off of the socket
if (this->GetRemainingReqBodyLen() > 0)
把socket里的数据读取出来并丢弃
// If we've gotten here, we've flushed all the data. Cleanup, and wait for
// our next request!
// 置空fRTPSession、fRequest！调用fSessionMutex.Unlock()、fReadMutex.Unlock();
this->CleanupRequest();
fState = kReadingRequest; // 注意，这里处于一个while循环
}
case kReadingRequest
{
类似于kReadingFirstRequest，如果socket有数据则将fState设为
kHaveNonTunnelMessage，否则则调用RequestEvent继续申请监听。
}
}
this->CleanupRequest();
return 0;
（5）、SetupRequest()
首先调用fRequest->Parse分析RTSP请求
// find the RTP session for this request
this->FindRTPSession(theMap);
// let's also refresh RTP session timeout so that it's kept alive in sync with the
// RTSP session.
if(fRTPSession != NULL) fRTPSession->RefreshTimeout();
// 在上面的Parse函数里已经调用RTSPProtocol::GetMethod设置fMethod
// 如果是OPTIONS，将系统支持的方法添加到头部（在DoInitRole里已经把各个模块登记的
// 支持方法汇总了）
// 注意这里并没有实际的通过socket发送出去，只是和fOutputStream相关联
if(fRequest->GetMethod() == qtssOptionsMethod)
{ ... ...}
// If this is a SET_PARAMETER request, don't let modules see it.
if (fRequest->GetMethod() == qtssSetParameterMethod)
{ ... ...}
// If this is a DESCRIBE request, make sure there is no SessionID. This is not
// allowed, and may screw up modules if we let them see this request.
if (fRequest->GetMethod() == qtssDescribeMethod)
{
if (fRequest->GetHeaderDictionary()->GetValue(qtssSessionHeader)->Len > 0)
{ SendErrorResponse(); return; }
}
if(fRTPSession == NULL) this->CreateNewRTPSession(theMap);
// If it's a play request and the late tolerance is sent in the request use this
// value
if ((fRequest->GetMethod() == qtssPlayMethod) && (fRequest->GetLateToleranceInSec() != -1))
// 这个函数做什么处理？？？
fRTPSession->SetStreamThinningParams(fRequest->GetLateToleranceInSec());
// Check to see if this is a "ping" PLAY request (a PLAY request while already
// playing with no Range header). If so, just send back a 200 OK response and do
// nothing. No need to go to modules to do this, because this is an RFC documented
// behavior
if ((fRequest->GetMethod() == qtssPlayMethod) && (fRTPSession->GetSessionState() == qtssPlayingState)
&& (fRequest->GetStartTime() == -1) && (fRequest->GetStopTime() == -1))
{ fRequest->SendHeader(); fRTPSession->RefreshTimeout(); return;}
// setup Authorization params;
fRequest->ParseAuthHeader();
（6）、CreateNewRTPSession
This is a brand spanking new session. At this point, we need to create a new
RTPSession object that will represent this session until it completes. Then, we
need to pass the session onto one of the modules
// First of all, ask the server if it's ok to add a new session
// 根据几个情况来判断是否可以添加新的RTPSession。
// 1、server的状态；2、最大连接数限制；3、最大带宽限制。
this->IsOkToAddNewRTPSession();
// create the RTPSession object
fRTPSession = NEW RTPSession();
// Lock the RTP session down so that it won't delete itself in the unusual event
// there is a timeout while we are doing this.
OSMutexLocker locker(fRTPSession->GetSessionMutex());
// Because this is a new RTP session, setup some dictionary attributes pertaining
// to RTSP that only need to be set once
this->SetupClientSessionAttrs();
// generate a session ID for this session
while (activationError == EPERM)
{
// 利用随机数生成SessionID
fLastRTPSessionIDPtr.Len = this->GenerateNewSessionID(fLastRTPSessionID);
// ok, some module has bound this session, we can activate it. At this
// point, we may find out that this new session ID is a duplicate. If
that's
// the case, we'll simply retry until we get a unique ID
// 该函数执行了以下操作：
// 1. 拷贝到fRTSPSessionIDBuf,
// 2. puts the session into the RTPSession Map:
// theServer->GetRTPSessionMap()->Register(&fRTPMapElem);
// 3. 调用IncrementTotalRTPSessions()
activationError = fRTPSession->Activate(fLastRTPSessionID);
}
（7）、QTSSModuleUtils::SendErrorResponse
... ...
if (sEnableRTSPErrorMsg)
{
准备要输出的Error Message
// 实际上是调用(RTSPRequestInterface*)inRequest)->AppendHeader函数
// 在该函数里，调用RTSPRequetInterface::fOutputStream(RTSPResponseStream类
// 对象)的Put函数关联Error Message
QTSS_AppendRTSPHeader(inRequest, qtssContentLengthHeader, buff, ::strlen(buff));
}
// send the response header. In all situations where errors could happen, we don't
// really care, cause there's nothing we can do anyway!
// 实际上是调用(RTSPRequestInterface*)inRequest)->SendHeader函数
// 在该函数里调用WriteStandardHeaders函数，添加标准的RTSP回复头部。
QTSS_SendRTSPHeaders(inRequest);
// Now that we've formatted the message into the temporary buffer, write it out to
// the request stream and the Client Session object
// 奇怪！！！始终只是调用RTSPRequetInterface::fOutputStream(RTSPResponseStream类
// 对象)的Put函数关联Error Message，并没有写具体的socket端口！！！
QTSS_Write(inRequest, theErrorMsgFormatter.GetBufPtr(), theErrorMsgFormatter.GetBytesWritten(), NULL,
0);
... ...
? RTSPSessionInterface
Presents an API for session-wide resources for modules to use. Implements the RTSP
Session dictionary for QTSS API.
（1）、构建函数
: QTSSDictionary(QTSSDictionaryMap::GetMap(QTSSDictionaryMap::kRTSPSessionDictIndex)),
Task();
// 对应于配置文件中的real_rtsp_timeout，缺省值为180
fTimeoutTask(NULL,QTSServerInterface::GetServer()->GetPrefs()->GetRealRTSPTimeoutInSecs() *
1000),
fInputStream(&fSocket), fOutputStream(&fSocket, &fTimeoutTask),
fSocket(NULL, Socket::kNonBlockingSocketType), fOutputSocketP(&fSocket),
fInputSocketP(&fSocket),
... ...
{
fTimeoutTask.SetTask(this); fSocket.SetTask(this); fStreamRef = this;
... ...
}
? RTSPListenerSocket
属于RTSP 子系统。基于TCPListenerSocket 子类。
（1）GetSessionTask
// when the server is behind a round robin DNS, the client needs to know the IP address
// of the server so that it can direct the "POST" half of the connection to the same
// machine when tunnelling RTSP thru HTTP
doReportHTTPConnectionAddress = QTSServerInterface::GetServer()->GetPrefs()->GetDoReportHTTPConnectionAddress();
theTask = NEW RTSPSession(doReportHTTPConnectionAddress);
// 返回fSocket 成员
*outSocket = theTask->GetSocket(); // out socket is not attached to a unix socket yet.
// 根据配置文件中的maximum_connections(缺省为1000)、fNumRTSPSessions、
// fNumRTSPHTTPSessions（这两个变量值在RTSPSession 的构建、析构函数、
PreFilterForHTTPProxyTunnel 函数里变化）来计算是否超过极限。
if(this->OverMaxConnections(0)) this->SlowDown(); // fSleepBetweenAccepts = true
else this->RunNormal(); // fSleepBetweenAccepts = flase
? TCPListenerSocket
处理基于TCP 协议的socket 传输。它的继承情况为：
class TCPListenerSocket : public TCPSocet, public IdleTask
class IdleTask : public Task
class TCPSocket : public Socket
class Socket : pulic EventContext
下面是一些成员函数的分析：
（1）构建函数
TCPListenerSocket() : TCPSocket(NULL, Socket::kNonBlockingSocketType),
IdleTask(),fAddr(0),
fPort(0), fOutOfDescriptors(false), fSleepBetweenAccepts(false)
{ this->SetTaskName("TCPListenerSocket"); }
（2）Initialize
创建打开流套接字（SOCK_STREAM）端口，并绑定IP 地址、端口，执行listen 操作。
注意在这个函数里调用了SetSocketRcvBufSize 成员函数，以设置这个socket 的接收缓冲区大小为
96K。而内核规定该值最大为sysctl_rmem_max，可以通过/proc/sys/net/core/rmem_default
rmem_max 来了解缺省值和最大值。（注意proc 下的这两个值也是可写的，可以通过调整这些值来
达到优化TCP/IP 的目的。例如：http://www.linuxsky.org/doc/admin/200705/53.html）
（3）ProcessEvent
在fListeners 申请监听流套接字端口后，一旦socket 端口有数据，该函数会被调用。
这个函数的流程是这样的：
首先通过accept 获得客户端的地址以及服务器端新创建的socket 端口。
通过GetSessionTask 创建一个RTSPSession 的类对象<每个RTSPSession 对象对应一个RTSP 连接>，
并将新创建的socket 端口描述符、sockaddr 信息保存到RTSPSession 的TCPSocket 类型成员
fSocket。同时调用fSocket::SetTask 和RequestEvent(EV_RE)，这样EventThread 在监听到
这个
socket 端口有数据时，会调用EventContext::processEvent 函数，在这个函数里会调用
fTask->Signal(Task::kReadEvent)，最终TaskThread 会调用RTSPSession::Run 函数。
而TCPListenerSocket 自己的socket 端口会继续被申请监听。
int osSocket = accept(fFileDesc, (struct sockaddr*)&addr, &size);
if(osSocket == -1)
{
如果errno 为EAGAIN，则再次调用RequestEvent;
... ... // 其它error 的处理，包括Task 发送kKillEvent 信号
}
theTask = this->GetSessionTask(&theSocket);
// set options on the socket. we are a server, always disable nagle algorithm
::setsockopt(osSocket, IPPROTO_TCP, TCP_NODELAY, (char*)&one, sizeof(int));
::setsockopt(osSocket, SOL_SOCKET, SO_KEEPALIVE, (char*)&one, sizeof(int));
sndBufSize = 96L * 1024L;
::setsockopt(osSocket, SOL_SOCKET, SO_SNDBUF, (char*)&sndBufSize, sizeof(int));
// setup the socket. When there is data on the socket, theTask will get an kReadEvent
// event
// TCPSocket::Set 函数通过getsockname 将osSocket 描述字对应的sockaddr 保存到
// TCPSocket::fLocalAddr，并设置TCPSocket:: fState |= kBound | kConnected。
// 同时将osSocket 保存为TCPSocket::fFileDesc
theSocket->Set(osSocket, &addr);
theSocket->InitNonBlocking(osSocket);
// 实际上是调用EventContext::SetTask
theSocket->SetTask(theTask);
theSocket->RequestEvent(EV_RE);
// 如果RTSPSession、HTTPSession 的连接数超过超过限制，则利用IdleTaskThread 定时调用
// Signal 函数，在TCPListenerSocket::Run 函数里会调用TCPListenerSocket::ProcessEvent 函数
// 执行accept(接收下一个连接)和RequestEvent(继续申请监听)。
if(fSleepBetweenAccepts) this->SetIdleTimer(kTimeBetweenAcceptsInMsec);
// sleep until there is a read event outstanding (another client wants to connect)
else this->RequestEvent(EV_RE);
? Socket
Socket 基于EventContext 类。
（1）、构建函数
Socket::Socket(Task *notifytask, UInt32 inSocketType)
: EventContext(EventContext::kInvalidFileDesc, sEventThread), fState(inSocketType),
fLocalAddrStrPtr(NULL),fLocalDNSStrPtr(NULL), fPortStr(fPortBuffer,
kPortBufSizeInBytes)
{
fLocalAddr.sin_addr.s_addr = 0; fLocalAddr.sin_port = 0;
fDestAddr.sin_addr.s_addr = 0; fDestAddr.sin_port = 0;
// SetTask 是EventContext 的成员函数，执行”fTask = notifytask”操作。
this->SetTask(notifytask);
}
（2）、Initialize
sEventThread = new EventThread();
（3）、StartThread
sEventThread->Start(); // 启动线程
? TaskThreadPool
任务线程池类，该类负责生成、删除以及维护内部的任务线程列表。下面是一些成员函数的分析：
（1）AddThreads
根据numToAdd 参数创建TaskThread 类对象，并调用该类的Start 成员函数。
将该类对象指针保存到sTaskThreadArray 数组。
? TaskThread
任务线程类，基于OSThread 类。下面是一些成员函数的分析：
（1）OSThread::Start
调用pthread_create 创建一个线程，该线程的入口函数为OSThread::_Entry 函数。
注意：对于有_POSIX_THREAD_PRIORITY_SCHEDULING 宏定义的pthread 库，创建线程的时候，应该添
加属性PTHREAD_SCOPE_SYSTEM，但是这里被注释掉了！！！
（2）OSThread::_Entry
theThread->Entry() //Entry 函数是OSThread 的纯虚函数，所以这里实际上会调用派生类的Entry
函数，也就是TaskThread::Entry 函数。
注意：在这里调用了pthread_setspecific 将theThread 和线程的key 相关联，而实际上theThread
是线程创建的时候传进来的一个参数，对于每个线程来说都是不一样的数据，有必要要和key 相关联
吗??? 只有对于那些可能多个线程都会访问改写的全局量才有必要关联线程的私有数据。
（3）TaskThread::WaitForTask
该函数同样由一个大循环构成。等待任务的通知到达，或者因stop 的请求而返回。
theCurrentTime = OS::Milliseconds(); //返回当前系统的时间（以ms 表示）
//如果堆里有时间记录，并且这个时间<=系统当前时间（说明任务的运行时间已经到了），则返回//
该记录所对应的任务对象
//PeekMin 获得堆中的第一个元素（但并不取出）
if ((fHeap.PeekMin() != NULL) && (fHeap.PeekMin()->GetValue() <= theCurrentTime))
return (Task*)fHeap.ExtractMin()->GetEnclosingObject();
//如果堆里有时间记录，则计算出还剩下的到时时间，如果小于10ms，则设成10ms
if (fHeap.PeekMin() != NULL)
theTimeout = fHeap.PeekMin()->GetValue() - theCurrentTime;
//对于theTimeout 等于0 的情况，可以考虑将theTimeout 设为更大的值，
//这样在没有事件的情况下，可以避免线程过于频繁的睡眠唤醒，而且也能够响应stop 请求。
if (theTimeout < 10) theTimeout = 10；
//等待事件发生
//TaskThread 类有一个OSQueue_Blocking 类的私有成员fTaskQueue。
//等待队列里有任务插入并将其取出返回。
//如果返回非空，则返回该队列项所对应的任务对象。
OSQueueElem* theElem = fTaskQueue.DeQueueBlocking(this, (SInt32) theTimeout);
if (theElem != NULL) return (Task*)theElem->GetEnclosingObject();
//如果有stop 的请求，则退出
if (OSThread::GetCurrent()->IsStopRequested()) return NULL;
（4）TaskThread::Entry
这个函数是任务线程的入口函数，由一个大循环构成。
// 等待任务的通知到达，或者因stop 的请求而返回（目前，WaitForTask 只有在收到stop 请求后
// 才返回NULL）。
theTask = this->WaitForTask();
if (theTask == NULL || false == theTask->Valid()) return;
Bool16 doneProcessingEvent = false;
// 下面也是一个循环，如果doneProcessingEvent 为true 则跳出循环。
// OSMutexWriteLocker、OSMutexReadLocker 均基于OSMutexReadWriteLocker 类，在下面的使用
// 中这两个类构建函数会调用sMutexRW->LockRead 或sMutexRW->LockWrite 进行互斥的读写操作。
// OSMutexRW 类对象sMutexRW 为taskThreadPool 类的成员，所以是对所有的线程互斥。
while (!doneProcessingEvent)
{
theTask->fUseThisThread = NULL;
if (theTask->fWriteLock) {
OSMutexWriteLocker mutexLocker(&TaskThreadPool::sMutexRW);
theTimeout = theTask->Run();
theTask->fWriteLock = false;
} else {
OSMutexReadLocker mutexLocker(&TaskThreadPool::sMutexRW);
theTimeout = theTask->Run();
}
如果theTimeout < 0，
则说明任务结束，任务对象被销毁，doneProcessingEvent 设为true，在后面调用
ThreadYield 后(对于linux 系统来说，ThreadYield 实际上没有做什么工作)，跳出这
个循环。再调用WaitForTask，等待下个处理。
如果theTimeout == 0，
将theTask->fEvents 和Task::kAlive 比较，如果返回1，则说明该任务已经没有事
件处理，反之则在ThreadYield 返回后继续在循环里处理这个任务的事件。
doneProcessingEvent = compare_and_store(Task::kAlive, 0, &theTask->fEvents);
// 虽然该任务目前没有事件处理，但是并不表示要销毁，所以没有delete。
if(doneProcessingEvent) theTask = NULL;
如果theTimeout > 0，
则说明任务希望等待theTimeout 时间后得到处理。
theTask->fTimerHeapElem.SetValue(OS::Milliseconds() + theTimeout);
// 将该任务的fTimerHeapElem 插入fHeap。
// 在下次的WaitForTask 运行时，一旦发现fHeap 有记录，就会做特别处理。
fHeap.Insert(&theTask->fTimerHeapElem);
// 给这个任务又添加了一个kIdleEvent???
atomic_or(&theTask->fEvents, Task::kIdleEvent);
doneProcessingEvent = true;
this->ThreadYield(); // 对于linux 系统来说，ThreadYield 实际上没有做什么工作
}
? Task
（1）Signal
如果该任务有指定处理的线程，则将该任务加入到指定线程的任务队列中。
如果没有指定的线程，则从线程池中随机选择一个任务线程，并将该任务加入到这个任务线程的任务
队列中。
或者干脆就没有线程运行，那么只是打印信息退出。
这里随机选择线程的方法值得商榷，目前的做法是轮流选择。其实对于已经发送过信号的任务来说，
可以记录选择的线程编号，这样下次可以调度同一个线程运行。需要注意线程任务均衡。
另外，是否线程池里的线程越多，效率就越高？？？
线程类的fTaskQueue.enqueue 函数加入的是&fTaskQueueElem，而在Task 的构建函数里，调用了
fTaskQueueElem.SetEnclosingObject(this)，这样线程类在处理这个事件的时候，就会知道对应的具
体任务，并通过任务的GetEvents 成员函数来获取待处理的事件类型。
fTaskQueueElem 是OSQueueElem 的类对象，很多涉及到队列操作的类，都会有这样的成员。通过这个
成员，可以把具体的类和队列项相关联。
有一点需要注意的是，因为是通过或操作，如果该线程的任务队列里已经有了一个事件待处理，那么
该事件不会被添加，也就是说在事件被处理之前，任务只会被调度一次。
? TimeoutTask
TimeoutTask.h 文件说明:
Just like a normal task, but can be scheduled for timeouts. Unlike IdleTask, which is
VERY aggressive about being on time, but high overhead for maintaining the timing
information, this is a low overhead, low priority timing mechanism. Timeouts may not
happen exactly when they are supposed to, but who cares?
下面是一些成员函数的分析：
（1）Initialize
sThread = NEW TimeoutTaskThread();
//TimeoutTaskThread 是IdleTask 的派生类，IdleTask 是Task 的派生类。
sThread->Signal(Task::kStartEvent);
（2）TimeoutTask::TimeoutTask(Task* inTask, Sint64 inTimeoutInMilSecs)
: fTask(inTask), fQueueElem() // 构建函数
fQueueElem.SetEnclosingObject(this);
this->SetTimeout(inTimeoutInMilSecs);
if (NULL == inTask) fTask = (Task *) this;
OSMutexLocker locker(&sThread->fMutex);
sThread->fQueue.EnQueue(&fQueueElem);
? TimeoutTaskThread
实际上这个类的名字容易产生混淆，它并不是一个线程类，而是一个基于Task类的任务类，它配合
TimeoutTask类实现一个周期性运行的基础任务。
这部分的架构是这样的：
在startServer里，调用了TimeoutTask::Initialize()。在这个函数里创建了一个TimeoutTaskThread
类对象，付给全局量sThread，同时sThread调用Signal，让自己得到运行。DSS别的模块在需要完成自
己的周期性工作时，通过TimeoutTask类的成员把自己的相关信息插入sThread的队列。任务线程在周
期性运行TimeoutTaskThread::Run函数时，会处理sThread队列内的所有任务，从而完成各种周期性工
作。
注意：在TaskThread::Entry将TimeoutTaskThread项从线程的fTaskQueue里取出处理后，根据Run返回
值，决定是否插入线程的fHeap，而不会再次插入到fTaskQueue里。如果插入fHeap，在
TaskThread::WaitForTask里会被得到处理。
（1）Run
这个函数是任务类的处理函数。线程一旦捕获到任务的事件后，会调用该任务的Run函数进行处理。
OSMutexLocker locker(&fMutex);
intervalMilli = kIntervalSeconds * 1000； taskInterval = intervalMilli；
在timeoutTaskThread的fQueue队列里获取TimeoutTask类对象。（在TimeoutTask类的构建函数里曾
经将自己插入到TimeoutTaskThread的fQueue队列。）
for (OSQueueIter iter(&fQueue); !iter.IsDone(); iter.Next()) {
TimeoutTask* theTimeoutTask = (TimeoutTask*)iter.GetCurrent()-
>GetEnclosingObject();
// if it's time to time this task out, signal it
// fTask是TimeoutTask类对象在创建的时候，传进来的具体任务。
// 如果发现有某个任务到期了，通过Signal通知线程。
if ((theTimeoutTask->fTimeoutAtThisTime > 0) && (curTime >=
theTimeoutTask->fTimeoutAtThisTime))
theTimeoutTask->fTask->Signal(Task::kTimeoutEvent);
else {
taskInterval = theTimeoutTask->fTimeoutAtThisTime - curTime;
if ((taskInterval > 0) && (theTimeoutTask->fTimeoutInMilSecs > 0) &&
(intervalMilli > taskInterval))
intervalMilli = taskInterval + 1000;
// 为什么多加1s，这样任务岂不是被延迟了1s ？？？
}
this->GetEvents(); // clear the event mask!
OSThread::ThreadYield(); // 这里的yield操作岂不是和TaskThread::Entry的重复？？
return intervalMilli; // 返回下一次的timeout值。Task::Entry根据这个返回值做后续处理。
? RTCPTask
基于Task类。This task handles all incoming RTCP data. It just polls, so make sure to
start the polling process by signalling a start event.
（1）、构建函数
RTCPTask() : Task() {this->SetTaskName("RTCPTask"); this->Signal(Task::kStartEvent); }
（2）、Run函数
在运行StartTasks创建RTCPTask类后，该Run函数就会被调度运行。
后续当监听到用来完成RTCP Data接收的Udp socket端口有数据时，EventContext::ProcessEvent调用
Signal(Task::kReadEvent)，该函数会被运行。
const Uint32 kMaxRTCPPacketSize = 2048; char thePacketBuffer[kMaxRTCPPacketSize];
StrPtrLen thePacket(thePacketBuffer, 0);
QTSServerInterface* theServer = QTSServerInterface::GetServer();
// This task goes through all the UDPSockets in the RTPSocketPool, checking to see if
// they have data. If they do, it demuxes the packets and sends the packet onto the
// proper RTP session.
EventFlags events = this->GetEvents(); // get and clear events
if((events & Task::kReadEvent) || (events & Task::kIdleEvent))
{
遍历SocketPool中的socket对中的每一个socket，如果这个socket有UDPDemuxer(在
RTPSocketPool::ConstructUDPSocketPair函数里，用来接收RTCP数据的Socket B就带有
Demuxer)，则将端口中接收到的数据发给UDPDemuxer对应的RTPStream，并调用RTPStream
的ProcessIncomingRTCPPacket函数。
在RTPStream的Setup函数里，曾经调用进行注册：
fSockets->GetSocketB()->GetDemuxer()->RegisterTask(fRemoteAddr, fRemoteRTCPPort, this);
}
return 0;
? RTPStatsUpdaterTask
基于Task类。This class runs periodically to compute current totals & averages，同时如果发
现RTP流量超过限制，会考虑是否发送kKillEvent信号给最近的会话。
（1）、构建函数
this->SetTaskName("RTPStatsUpdaterTask");
this->Signal(Task::kStartEvent);
（2）、Run函数
在运行StartTasks创建RTPStatsUpdaterTask类后，该Run函数就会被调度运行。
后续通过调用Task::Signal，该函数会被运行。
QTSServerInterface* theServer = QTSServerInterface::sServer;
// All of this must happen atomically wrt dictionary values we are manipulating
OSMutexLocker locker(&theServer->fMutex);
// First update total bytes. This must be done because total bytes is a 64 bit number,
// so no atomic functions can apply.
// 这种做法有什么意义呢？？？因为在一开始就获得了锁
unsigned int periodicBytes = theServer->fPeriodicRTPBytes;
(void)atomic_sub(&theServer->fPeriodicRTPBytes, periodicBytes);
theServer->fTotalRTPBytes += periodicBytes;
// Same deal for packet totals
unsigned int periodicPackets = theServer->fPeriodicRTPPackets;
(void)atomic_sub(&theServer->fPeriodicRTPPackets, periodicPackets);
theServer->fTotalRTPPackets += periodicPackets;
// ... and for lost packet totals
unsigned int periodicPacketsLost = theServer->fPeriodicRTPPacketsLost;
(void)atomic_sub(&theServer->fPeriodicRTPPacketsLost, periodicPacketsLost);
theServer->fTotalRTPPacketsLost += periodicPacketsLost;
Sint64 curTime = OS::Milliseconds();
// 调用clock函数。clock函数返回进程第一次调用clock以来所用去的cpu时间。
// 第一次调用clock返回0.
Float32 cpuTimeInSec = GetCPUTimeInSeconds();
// also update current bandwidth statistic
if(fLastBandwidthTime != 0)
{
Uint32 delta = (Uint32)(curTime - fLastBandwidthTime);
if(delta < 1000) { // 何时会出现这种情况？？？
(void)this->GetEvents(); // we must clear the event mask
return theServer->GetPrefs()->GetTotalBytesUpdateTimeInSecs() * 1000;
}
设置theServer->fRTPPacketsPerSecond.(包流量)
设置theServer->fCurrentRTPBandwidthInBits.（字节流量）
let's do it for MP3 bytes now，设置theServer->fCurrentMP3BandwidthInBits.
do the computation for cpu percent，设置theServer->fCPUPercent.
}
设置fLastTotalMP3Bytes、fLastBandwidthTime、theServer->fAvgMP3BandwidthInBits、
theServer->fCPUTimeUsedInSec。
// compute average bandwidth, a much more smooth value. This is done with the
// fLastBandwidthAvg, a timestamp of the last time we did an average, and fLastBytesSent,
// the number of bytes sent when we last did an average.
// GetAvgBandwidthUpdateTimeInSecs对应于配置文件中的average_bandwidth_update，缺省为60s.
if((fLastBandwidthAvg != 0) && (curTime > (fLastBandwidthAvg +
(theServer->GetPrefs()->GetAvgBandwidthUpdateTimeInSecs()*1000))))
{
设置theServer->fAvgRTPBandwidthInBits。
// if the bandwidth is above the bandwidth setting, disconnect 1 user by sending
// them a BYE RTCP packet.
// 如果平均带宽大于配置中的最大带宽，则做出处理
// GetMaxKBitsBandwidth对应于配置文件中的maximum_bandwidth，缺省为102400 K/s.
SInt32 maxKBits = theServer->GetPrefs()->GetMaxKBitsBandwidth();
// 在streamingserver.xml里对safe_play_duration的解释：
// If the server discovers it is serving more than its allowed maximum
// bandwidth (using the average bandwidth computation) it will attempt to
// disconnect the most recently connected clients until the average bandwidth
// drops to acceptable levels. However, it will not disconnect clients if they've
// been connected for longer than this time in seconds. If this value is set to 0,
// it will never disconnect clients.
if ((maxKBits>-1) && (theServer->fAvgRTPBandwidthInBits > ((UInt32)maxKBits*1024)))
{
OSMutexLocker locker(theServer->GetRTPSessionMap()->GetMutex());
RTPSessionInterface* theSession=this->GetNewestSession(theServer->fRTPMap);
if(theSession != NULL)
if ((curTime - theSession->GetSessionCreateTime()) <
theServer->GetPrefs()->GetSafePlayDurationInSecs()*1000)
theSession->Signal(Task::kKillEvent);
}
} else if(fLastBandwidthAvg == 0) {
fLastBandwidthAvg = curTime; fLastBytesSent = theServer->fTotalRTPBytes;
}
(void)this->GetEvents(); // clear the event mask!
// 对应于配置文件中的total_bytes_update，缺省为1s。
return theServer->GetPrefs()->GetTotalBytesUpdateTimeInSecs() * 1000;
? QTSSErrorLogModule
（1）、Register()
QTSS_AddRole(QTSS_ErrorLog_Role);
QTSS_AddRole(QTSS_Shutdown_Role);
QTSS_AddRole(QTSS_StateChange_Role);
QTSS_AddRole 这一类函数均在QTSS_Private.cpp 里定义，即通过sCallbacks 调用相应的
DSS 处理函数，而这里的sCallbacks 即是在上面分析的SetupModule 里赋值的QTSServer 的
成员sCallbacks。而在QTSServer::Initialize 函数里也已调用InitCallbacks 函数对
sCallbacks 进行了初始化。这样各个模块就可以通过它来调用DSS 的各种处理函数。
对于QTSS_AddRole，处理函数是QTSSCallbacks::QTSS_AddRole(见下面的分析)
QTSS_AddRole 通过QTSSModule::AddRole 函数在fRoleArray 数组里记录已支持的Role 情况
(奇怪的是，这个数组是QTSSModule 的私有成员，感觉应该是由QTSServer 来维护这个记录)
(原来在QTSServer::BuildModuleRoleArrays 函数里我们发现根据QTSSModule 的fRoleArray
数组的Role 支持情况，在QTSServerInterface::sNumModulesInRole 里做记录，并在
sModuleArray 数组里保存相关Role 的所有QTSSModule 指针)
QTSS_AddService(“RollErrorLog”, &RollErrorLog)
类似于QTSS_AddRole，最终会调用QTSSCallbacks::QTSS_AddService(见下面的分析)
CheckErrorLogState（）
sErrorLog = NEW QTSSErrorLog(); // 决定是否启动ErrorLog task
sErrorLog->EnableLog();
// 如果Error log task 已启动，将启动信息通过sErrorLog 类写到log 文件。
WriteStartupMessage();
sErrorLogCheckTask = NEW ErrorLogCheckTask();
（2）、CheckErrorLogState()
// check error log
// 根据streamingserver.xml配置文件来决定是否启动ErrorLog task,
// thePrefs已经记录了各个属性设置值. 应该是根据属性名称来匹配每一个属性的.
if ((NULL == sErrorLog) && (thePrefs->IsErrorLogEnabled()))
{ sErrorLog = NEW QTSSErrorLog(); sErrorLog->EnableLog(); }
（3）、LogError()
... ...
if(sErrorLog != NULL) sErrorLog->WriteToLog(...);
... ...
? ErrorLogCheckTask
Task类的继承类，主要的任务是每一个小时检查一次if the log needs to roll
（1）、构建函数
ErrorLogCheckTask() : Task()
{this->SetTaskName("ErrorLogCheckTask"); this->Signal(Task::kStartEvent); }
（2）、Run函数
// 如果创建了ErrorLog task，则调用sErrorLog->CheckRollLog();
// 和QTSSRollingLog每一分钟一次的任务相比，这里多了log文件大小的检查。
if(sErrorLog != NULL && sErrorLog->IsLogEnabled()) success = sErrorLog-
>CheckRollLog();
return (60*60*1000); // 1 小时后执行；
? QTSSErrorLog、QTSSRollingLog
QTSSRollingLog的继承类, QTSSRollingLog是Task的继承类.
（1）、QTSSRollingLog::EnableLog()
this->Signal(TASK::kStartEvent); // Start this object running!
打开log文件，并将log header写入该文件
（2）、QTSSRollingLog::WriteToLog()
确保log file已经打开
if(allowLogToRoll) this->CheckRollLog();
调用qtss_fprintf将数据写入log文件。
对log file执行fflush、close工作。
（3）、QTSSRollingLog::CheckRollLog()
// first check to see if log rolling should happen because of a date interval. This takes
// precedence over size based log rolling. this is only if a client connects just between
// 00:00:00 and 00:01:00 since the task object runs every minute.
// when an entry is written to the log file, only the file size must be checked to see if
// it exceeded the limits.
// the roll interval should be monitored in a task object and rolled at midnight if the
// creation time has exceeded.
如果条件满足，则调用this->RollLog();
（4）、QTSSRollingLog::RollLog()
... ...this->RenameLogFile(fLogFullPath); ... ...
（5）、QTSSRollingLog::RenameLogFile
this function takes care of renaming a log file from "myLogFile.log" to
"myLogFile.981217000.log" or if that is already taken, myLogFile.981217001.log", etc
（6）、QTSSRollingLog::Run()
根据时间判断是否需要调用RollLog函数；
返回60 * 1000; // 该任务每1 分钟会被调度一次。
? OSQueue_Blocking
该类用作TaskThread 的私有成员类，实际上是利用线程的条件变量实现了一个可等待唤醒的队列操
作。下面是一些成员函数的分析：
（1）Enqueue
调用OSQueue 类成员fQueue.EnQueue 函数
调用OSCond 类成员fCond.Signal 函数即调用pthread_cond_signal(&fCondition);
（2）DeQueueBlocking
如果fQueue.GetLength() == 0，则调用fCond.Wait 即调用pthread_cond_timedwait 等待条件变量
有效（从上面的分析可知：任务在调用Signal 函数时，实际上就是调用对应线程的fCond.Signal 函
数）
fCond.wait 返回或者fQueue.GetLength() != 0，调用fQueue.DeQueue 返回队列里的任务对象。这里
要注意一点，pthread_cond_timedwait 可能只是超时退出，所以fQueue.DeQueue 可能只是返回空指
针。
需要注意的是：在使用线程的条件变量时需要配合使用一个互斥锁，上述函数都是通过一个
OSMutexLocker 类的局部变量的构建/析构函数来完成这个锁的Lock/Unlock 操作。
? OSMutexRW
这个类是通过互斥锁、线程条件变量、读写状态、等待状态来维持一个读和写互斥的操作。它有一个
OSMutex 类的成员fInternalLock，来完成真正的互斥锁操作。在OSMutex 类的构建函数里，会调用
pthread_mutex_init pthread_mutexattr_init 函数来初始化它的成员fMutex（pthread_mutex_t 对
象）。
下面是一些成员函数的分析：
（1）LockRead
// 通过互斥锁保护读写状态及计数变量。
// 在OSMutexLocker 的构建函数里，会调用OSMutex 类的Lock 函数。OSMutexLocker 这个类的工
// 作就是纯粹完成lock/unlock 操作，创建时lock、销毁时unlock(locker 只是一个局部变量，在
// 这个函数退出的时候被销毁)。
// 在OSMutex 的Lock 处理里，如果该线程已经获得该锁，则退出，否则调用
// pthread_mutex_lock，虽然这里有被阻塞的可能，但是因为LockRead、LockWrite 很快退出，//
互斥锁也会被很快释放。
// 在OSMutex 的Unlock 处理里，如果线程不持有该锁，则退出，否则调用pthread_mutex_unlock
OSMutexLocker locker(&fInternalLock);
// fReadWaiters += 1;
AddReadWaiter();
// 根据fState、fWriteWaiters 来判断是否有写操作在进行或者有写等待
// 如果有，通过线程条件变量来等待，注意这里的OSMutexRW::eMaxWait 为0xFFFFFFFF，
// 不过Wait 调用的pthread_cond_wait 也会先unlock 锁，从而避免死锁。
// fWriteWaiters: number of waiting writers
// fState: -1: writer, 0: free, >0: readers
while (ActiveWriter() || WaitingWriters())
fReadersCond.Wait(&fInternalLock, OSMutexRW::eMaxWait);
RemoveReadWaiter();
AddActiveReader(); // add 1 to active readers
fActiveReaders = fState;
（2）LockWrite
类似于LockRead。
（3）Unlock
根据当前活跃的是读操作还是写操作，来唤醒写等待或者唤醒所有的读等待。
（4）TryLockWrite、TryLockRead
非阻塞的实现。
? IdleTaskThread、IdleTask
IdleTaskThread 基于OSThread、IdleTask 基于Task 类。
IdleTasks are identical to normal tasks (see task.h) with one exception:
You can schedule them for timeouts. If you call SetIdleTimer on one, after the time
has elapsed the task object will receive an OS_IDLE event.
这套机制实际上是利用一个线程专门来处理一个定时事件，平时睡眠，一旦发现有任务到期，就会
通过signal 通知另外的线程处理这个事件。而别的模块可以通过IdleTaskThread::SetIdleTimer 函
数
将自己的信息插入到IdleTaskThread 的堆栈里。
TimoutTaskThread+TaskThread 其实也实现了类似的机制。和IdleTask 机制相比，后者要更为准确：
1、TimeoutTaskThread 机制由TaskThread 处理，而TaskThread 除了处理这个，还有很多的任务处
理。
2、TimeoutTaskThread::Run 函数里，在发现未到期的任务时，会莫名其妙的加个1s（用意何
在？？？）
另外TimeoutTaskThread 机制实现的是周期性的事件处理，而IdleTask 机制的是一次性定时事务处
理。
感觉奇怪的是：既然有了这个纯粹处理定时事务的IdleTask 机制，何必去使用纠缠到TaskThread
上的TimeoutTaskThread 机制呢？？？
（1）、IdleTask::Initialize 函数
该函数在StartServer 里会被调用。
sIdleThread = NEW IdleTaskThread(); sIdleThread->Start();
（2）、IdleTaskThread::Entry 函数
空闲任务线程启动后，该函数运行。主要由一个大循环构成：
OSMutexLocker locker(&fHeapMutex);
while (true)
{
// if there are no events to process, block.
if (fIdleHeap.CurrentHeapSize() == 0) fHeapCond.Wait(&fHeapMutex);
// pop elements out of the heap as long as their timeout time has arrived.
while ((fIdleHeap.CurrentHeapSize() > 0) && (fIdleHeap.PeekMin()->GetValue() <=
msec))
{
IdleTask* elem = (IdleTask*)fIdleHeap.ExtractMin()->GetEnclosingObject();
elem->Signal(Task::kIdleEvent);
}
// we are done sending idle events. If there is a lowest tick count, then
// we need to sleep until that time.
if (fIdleHeap.CurrentHeapSize() > 0)
{
SInt64 timeoutTime = fIdleHeap.PeekMin()->GetValue();
// because sleep takes a 32 bit number
timeoutTime -= msec; UInt32 smallTime = (UInt32)timeoutTime;
fHeapCond.Wait(&fHeapMutex, smallTime);
}
}
? EventContext、EventThread
An event context provides the intelligence to take an event generated from a UNIX file
descriptor (usually EV_RE or EV_WR) and signal a Task.
EventThread 基于OSThread。
EventThread 的机制是这样的：
在Entry 的循环调用里，select_waitevent 要么调用select 监听包括管道文件在内的所有文件、要
么在发现已就绪的描述字后，将每一个就绪描述字的fd、事件类型、唯一的一个标识符返回给
Entry 函数。Entry 函数根据标识符在fRefTable 里找到登记的EventContext 的类对象，从而调用该
对象的processEvent 函数进行处理。
周而复始。
而那些基于EventContext 类的模块在需要申请监听某个文件/socket 时，先调用
EventContext::RequestEvent 函数，在这个函数里，将要登记的fd、事件类型添加到描述字集合里，
并写一个字符到管道文件里，从而引起EventThread 的select 退出，重新select 新的描述字集合。
如果这个模块是第一次申请监听，还要分配一个唯一的描述符，并将自己的信息通过fRef 登记到
fRefTable 里，以供EventThread 使用。
需要注意的是：模块在调用processEvent 处理已发生的事件后，如果需要再次监听，则仍要调用
RequestEvent 函数。
（1）、EventContext 构建函数
EventContext::EventContext(int inFileDesc, EventThread* inThread)
: fFileDesc(inFileDesc), fEventThread(inThread), fWatchEventCalled(false),
fUniqueIDStr((char*)&fUniqueID, sizeof(fUniqueID)), ... ...
{}
（2）、EventContext::RequestEvent
// The first time this function gets called, we're supposed to call watchevent. Each
// subsequent time, call modwatch.
if (fWatchEventCalled)
{
fEventReq.er_eventbits = theMask;
// 更新描述字集合，并写管道文件，以通知EventThread
select_modwatch(&fEventReq, theMask)
} else {
// 如果是第一次申请，需要先分配一个唯一的标识符
// 并将fRef 注册到fRefTable，以供EventThread 在后续处理中找到对应的对象
if(!compare_and_store(10000000, 1, &sUniqueID))
fUniqueID=(PointerSizedInt)atomic_add(&sUniqueID, 1); //sUniqueID 初始化
为1
else fUniqueID = 1;
fRef.Set(fUniqueIDStr, this); // fRef 是OSRef 的类对
象。
fEventThread->fRefTable.Register(&fRef); // 参见下面OSRef、OSRefTable
// fill out the eventreq data structure
::memset(&fEventReq, '\0', sizeof(fEventReq)); fEventReq.er_type = EV_FD;
fEventReq.er_handle = fFileDesc; fEventReq.er_eventbits = theMask;
fEventReq.er_data = (void*) fUniqueID;
select_watchevent(&fEventReq, theMask) // 实际上就是调用select_modwatch
}
（3）、select_startevents
// initialize the select() implementation of the event queue
FD_ZERO(&sReadSet); FD_ZERO(&sWriteSet);
FD_ZERO(&sReturnedReadSet); FD_ZERO(&sReturnedWriteSet);
创建sCookieArray 并初始化
创建sFDsToCloseArray 并初始化
// We need to wakeup select when the masks have changed. In order to do this,
// we create a pipe that gets written to from modwatch, and read when select returns.
::pipe((int*)&sPipes);
// Add the read end of the pipe to the read mask
FD_SET(sPipes[0], &sReadSet); sMaxFDPos = sPipes[0];
（4）、select_modwatch
OSMutexLocker locker(&sMaxFDPosMutex);
// Add or remove this fd from the specified sets
if (which & EV_RE) FD_SET(req->er_handle, &sReadSet);
else FD_CLR(req->er_handle, &sReadSet);
if (which & EV_WR) FD_SET(req->er_handle, &sWriteSet);
else FD_CLR(req->er_handle, &sWriteSet);
if(req->er_handle > sMaxFDPos) sMaxFDPos = req->er_handle;
sCookieArray[req->er_handle] = req->er_data;
// write to the pipe so that select wakes up and registers the new mask
// 这里写管道文件的作用见下面的分析
theErr = ::write(sPipes[1], “p”, 1);
（5）、select_waitevent
如果没有就绪的描述字，则调用select 进行监听，否则通过constructeventreq 将就绪描述字的信
息传递给EventThread::Entry 函数。
EventThread::Entry 函数根据select_waitevent 返回值，决定是否再次调用select_waitevent 还是
调用就绪描述字对应的类的处理函数。
// check to see if we still have some select descriptors to process
// sNumFDsProcessed: 指的是已就绪待处理并已交由EventThread::Entry 处理的描述字个数
// sNumFDsBackFromSelect: 指的是已就绪待处理的描述字总个数
int theFDsProcessed = (int)sNumFDsProcessed; bool isSet = false;
if(theFDsProcessed < sNumFDsBackFromSelect) // 还有已就绪的描述字待处理
{
if(sInReadSet)
{
OSMutexLocker locker(&sMaxFDPosMutex);
// 在select_modwatch 函数中，sMaxFDPos 可能会被更新。
// 也就是说sMaxFDPos 反映现有被监听的最大文件描述符。
// 找到sReturnedReadSet 中第一个描述字，也就是第一个有效的描述字。
while((!(isSet=FD_ISSET(sCurrentFDPos,&sReturnedReadSet)))&&(sCurrentFDPos<sMaxFDPos))
sCurrentFDPos++;
if(isSet)
{
FD_CLR(sCurrentFDPos, &sReturnedReadSet);
// 提出信息后交给EventThread::Entry 处理
return constructeventreq(req, sCurrentFDPos, EV_RE);
} else {
sInReadSet = false; sCurrentFDPos = 0;
}
}
if(!sInReadSet)
{
OSMutexLocker locker(&sMaxFDPosMutex);
while((!(isSet=FD_ISSET(sCurrentFDPos,&sReturnedWriteSet)))&&(sCurrentFDPos<sMaxFDPos))
sCurrentFDPos++;
if(isSet)
{
FD_CLR(sCurrentFDPos, &sReturnedWriteSet);
return constructeventreq(req, sCurrentFDPos, EV_WR);
} else {
// This can happen if another thread calls select_removeevent at
// just the right time, setting sMaxFDPos lower than it was when
// select() was last called. Becase sMaxFDPos is used as the place
to
// stop iterating over the read & write masks, setting it lower can
// cause file descriptors in the mask to get skipped. If they are
// skipped, that's ok, because those file descriptors were removed
by
// select_removeevent anyway. We need to make sure to finish
// iterating over the masks and call select again, which is why we
// set sNumFDsProcessed artificially here.
sNumFDsProcessed = sNumFDsBackFromSelect;
}
}
}
if(sNumFDsProcessed > 0)
{
// 经过select_waitevent 反复调用后，执行到这里说明所有已就绪的描述字都已处理。
OSMutexLocker locker(&sMaxFDPosMutex);
// We've just cycled through one select result. Re-init all the counting states
sNumFDsProcessed=0; sNumFDsBackFromSelect=0; sCurrentFDPos = 0; sInReadSet = true;
}
// selecthasdata 不应该放在这里
while(!selecthasdata())
{
{
OSMutexLocker locker(&sMaxFDPosMutex);
// Prepare to call select. Preserve the read and write sets by copying
// their contents into the corresponding "returned" versions, and then pass
// those into select
// 更新描述字集合，从而让新申请的监听有效。
// sReadSet、sWriteSet 会在RequestEvent 函数里被更新。
::memcpy(&sReturnedReadSet, &sReadSet, sizeof(fd_set));
::memcpy(&sReturnedWriteSet, &sWriteSet, sizeof(fd_set));
}
设置select 的timeout 值，对于我们的系统，tv.tv_sec = 15。
调用OSThread::ThreadYield() // 对于linux 系统，这里实际上没有做什么工作。
// select 的返回值有三种：
// 返回-1，意味着出现错误，例如在任何描述字就绪之前就出现了信号。
// 返回0，意味着在任何描述字就绪之前，定时已到期。描述字集合被清0
// 返回正整数，它指出已就绪的描述字个数。描述字集合中只包括已就绪的描述字。
sNumFDsBackFromSelect = ::select(sMaxFDPos+1, &sReturnedReadSet, &sReturnedWriteSet, NULL, &tv);
}
if(sNumFDsBackFromSelect >= 0)
return EINTR; // either we've timed out or gotten some events. Either way, force
// caller to call waitevent again. select_waitevent 的调用者
//EventThread::Entry 在得到EINTR 的返回值后，会再次调用select_waitevent
// 如果在第一次select 时，出现错误（非EINTR）。那么EventThread 岂不是陷入这种情况的处理
// 中，而不会做任何事情！！！这里应该将sNumFDsBackFromSelect 清零。
return sNumFDsBackFromSelect;
（6）、constructeventreq
req->er_handle = fd; req->er_eventbits = event;
req->er_data = sCookieArray[fd]; sCurrentFDPos++; sNumFDsProcessed++;
// don't want events on this fd until modwatch is called.
// 注意这里去掉了，如果还想继续监听的话，要重新request。
FD_CLR(fd, &sWriteSet); FD_CLR(fd, &sReadSet);
（7）、selecthasdata
// 返回false, select_waitevent 会继续select
// 返回true，select_waitevent 退出。EventThread::Entry 根据select_waitevent 返回值
// 决定是否处理事件还是继续调用select_waitevent。
if(sNumFDsBackFromSelect < 0)
{
int err = OSThread::GetErrno();
if(err == EBADF || err ==EINTR) return false;
// if there is an error from select, we want to make sure and return
// to the caller
return true;
}
if(sNumFDsBackFromSelect == 0)
return false; //if select returns 0, we've simply timed out, so recall
select
// 为什么要用管道？表面上看好像就是为了通知关闭sFDsToCloseArray 里的fd。
// 实际上别的模块在申请监听别的文件（或者说socket）的时候，在添加到sReadSet、
// sWriteSet 后，会写管道文件（见select_modwatch 函数）。这样select_waitevent 中
// 的select 会提前返回。最终selecthasdata 会再次返回0，从而会将sReadSet 拷贝到
// sReturnedReadSet、sWriteSet 拷贝到sReturnedWriteSet（注意select 监听的是
// sReturnedReadSet、sReturnedWriteSet），这样就达到了能很快监听新的文件的目的。
// 不过这里要注意的是：select_waitevent 对于每一个有效的fd 都会调用
// constructeventreq 交给EventThread::Entry 处理。而实际上管道的事件无需处理（也没
// 有在sCookieArray 里添加针对管道的项），所以这里会空走几个回合。不过模块写管道
// 的次数毕竟不会很多，应该不会占用很多的cpu。
// 可以考虑将处理管道的这部分放在select_waitevent 的最前面。
if(FD_ISSET(sPipes[0], &sReturnedReadSet))
{
// we've gotten data on the pipe file descriptor. Clear the data.
// increasing the select buffer fixes a hanging problem when the Darwin
// server is under heavy load
char theBuffer[4096];
(void)::read(sPipes[0], &theBuffer[0], 4096);
FD_CLR(sPipes[0], &sReturnedReadSet); sNumFDsBackFromSelect--;
{
// Check the fds to close array, and if there are any in it, close
// those descriptors
OSMutexLocker locker(&sMaxFDPosMutex);
for (Uint32 theIndex=0; ((sFDsToCloseArray[theIndex] != -1) &&
(theIndex < sizeof(fd_set)*8)); theIndex++)
{
::close(sFDsToCloseArray[theIndex]);
sFDsToCloseArray[theIndex] = -1;
}
}
}
if(sNumFDsBackFromSelect == 0)
return false;//if the pipe file descriptor is the ONLY data we've gotten, recall select
else return true; //we've gotten a real event, return that to the caller
}
（8）、EventThread::Entry
该函数是event thread 的入口函数。类似于Taskthread，在线程创建启动后，该函数会被调用。
主要由一个大循环构成。
struct eventreq theCurrentEvent; ::memset(&theCurrentEvent, '\0',
sizeof(theCurrentEvent));
while (true)
{
int theErrno = EINTR;
while(theErrno == EINTR)
{ int theReturnValue = select_waitevent(&theCurrentEvent, NULL);
if(theReturnValue >= 0) theErrno = theReturnValue;
else theErrno = OSThread::GetErrno();
}
// there is data waiting on this socket. Send a wakeup.
// 还有一种可能，就是前面出错（非EINTR）。对于这种情况，其实可以根据
// theCurrentEvent.er_data 是否为空来判断。但是在处理完theCurrentEvent 后，却没有
// memset 的动作！！！，这样会导致不存在的事件处理。
if(theCurrentEvent.er_data != NULL)
{// The cookie in this event is an objectID. Resolve that objectID into a pointer.
StrPtrLen idStr((char*)&theCurrentEvent.er_data, sizeof(theCurrentEvent.er_data));
OSRef* ref = fRefTable.Resolve(&idStr);
if (ref != NULL)
{ EventContext* theContext = (EventContext*)ref->GetObject();
// 在找到对应的类对象之后，调用该对象的处理函数。
theContext->ProcessEvent(theCurrentEvent.er_eventbits);
fRefTable.Release(ref);
}
}
this->ThreadYield(); // 对于linux 系统，ThreadYield 没有做任何事
}
? OSRef、OSRefKey、OSRefTableUtils、OSRefTable、OSRefReleaser
Class supports creating unique string IDs to object pointers. A grouping
of an object and its string ID may be stored in an OSRefTable, and the
associated object pointer can be looked up by string ID.
Refs can only be removed from the table when no one is using the ref,
therefore allowing clients to arbitrate access to objects in a preemptive,
multithreaded environment.
OSRef 对象引用表则是类似于COM/DCOM 组件编程中IUNKOWN 接口功能的数据结构，它首先为每个对象
建立了一个字符串形式的ID，以便于通过这个ID 找到对象。
（三）、Attributes 相关
QTSS objects consist of attributes that are used to store data. Every attribute has a name, an attribute ID, a
data type, and permissions for reading and writing the attribute’s value. There are two attribute types:
■ static attributes. Static attributes are present in all instances of an object type. A module can add static
attributes to objects from its Register role only. All of the server’s built-in attributes are static attributes.
■ instance attributes. Instance attributes are added to a specific instance of any object type.A module can use
any role to add an instance attribute to an object and can also remove instance attributes that it has added to an object.
相关的初始化在StartServer里开始，顺序为：
QTSSDictionaryMap::Initialize();
QTSServerInterface::Initialize();
sServer = NEW QTSServer();
而这个顺序也是不可更改的。
? QTSSDictionary类
Dictionary is a data storage base class that implements key and value access to object data. This base class is
inherited by all server objects defined by the API.
它的继承类中的QTSSAttrInfoDict类就是被用来描述QTSS Object的具体一个属性。
该类有指向QTSSDictionaryMap 类对象的成员fMap、fInstanceMap。
（1）、构建函数
QTSSDictionary::QTSSDictionary(QTSSDictionaryMap* inMap, OSMutex* inMutex)
: fAttributes(NULL), fInstanceAttr(NULL), fInstanceArraySize(0), fMap(inMap),
fInstanceMap(NULL), fMutexP(inMutex), fMyMutex(false), fLocked*(false)
{
// 根据dict map描述的属性个数，来初始化fAttributes。
if(fMap != NULL) fAttributes = NEW DictValueElement[inMap->GetNumAttrs()];
if(fMutexP == NULL) {
fMyMutex = true; fMutexP = NEW OSMutex();
}
}
（2）、QTSSDictionary::SetVal()
// 记录每个属性的信息、包括属性数据的来源和长度等。
fAttributes[inAttrID].fAttributeData.Ptr = (char*)inValueBuffer;
fAttributes[inAttrID].fAttributeData.Len = inBufferLen;
fAttributes[inAttrID].fAllocatedLen = inBufferLen;
fAttributes[inAttrID].fNumAttributes = 1;
（3）、QTSSDictionary::SetValue()
对于要设置的属性对应有多个值的情况，SetValue函数根据属性的ID、值的index找到正确的存储位
置（这里可能会涉及到空间的重分配和老数据的转储），并利用inBuffer指针拷贝存储新的数据。
所以调用这个函数时传进来的inBuffer指针可以为局部变量。
// 根据传入的ID值，判断是否为Instance Attribute
QTSSDictionaryMap* theMap = fMap; DictValueElement* theAttrs = fAttributes;
if(QTSSDictionaryMap::IsInstanceAttrID(inAttrID))
{ theMap = fInstanceMap;theAttrs = fInstanceAttrs; }
OSMutexLocker locker(fMutexP);
... ... // 一些异常情况的判断。
numValues = theAttrs[theMapIndex].fNumAttributes;
dataType = theMap->GetAttrType(the); //fAttrArray[inIndex]->fAttrInfo.fAttrDataType
Uint32 attrLen = inLen;
if (dataType == qtssAttrDataTypeCharArray)
{
if(inIndex > 0) attrLen = sizeof(char *); // value just contains a pointer
if((numValues == 1) && (inIndex == 1))
{
// we're adding a second value, so we need to change the storage from directly
// storing the string to an array of string pointers.
// creating new memory here just to create a null terminated string instead of
// directly using the old storage as the old storage didn't have its string null
// terminated.
UInt32 tempStringLen = theAttrs[theMapIndex].fAttributeData.Len;
char* temp = NEW char[tempStringLen + 1];
::memcpy(temp, theAttrs[theMapIndex].fAttributeData.Ptr, tempStringLen);
temp[tempStringLen] = '\0';
delete [] theAttrs[theMapIndex].fAttributeData.Ptr;
theAttrs[theMapIndex].fAllocatedLen = 16 * sizeof(char*);
theAttrs[theMapIndex].fAttributeData.Ptr=NEW
char[theAttrs[theMapIndex].fAllocatedLen];
theAttrs[theMapIndex].fAttributeData.Len = sizeof(char*);
// store off original string as first value in array
// 分配空间、将原先的字符串转存之后，把指针付给已重新分配的指针数组Ptr
// 的第一个元素。
*(char**)theAttrs[theMapIndex].fAttributeData.Ptr = temp;
}
} else {
// If this attribute is iterated, this new value must be the same size as all the
// others.
if((inIndex > 0) || (numValues > 1)) &&
(theAttrs[theMapIndex].fAttributeData.Len != 0)
&& (inLen != theAttrs[theMapIndex].fAttributeData.Len))
return QTSS_BadArgument;
}
// Can't put empty space into the array of values
if(inIndex > numValues) return QTSS_BadIndex;
if((attrLen *(inIndex + 1)) > theAttrs[theMapIndex].fAllocatedLen)
{
计算要重新分配的空间大小
char * theNewBuffer = NEW char[theLen];
if(inIndex > 0) // 将老的数据拷贝过来
::memcpy(theNewBuffer, theAttrs[theMapIndex].fAttributeData.Ptr,
theAttrs[theMapIndex].fAllocatedLen);
if (theAttrs[theMapIndex].fAllocatedInternally)
delete [] theAttrs[theMapIndex].fAttributeData.Ptr;
// update this attribute structure with all the new values
theAttrs[theMapIndex].fAttributeData.Ptr = theNewBuffer;
theAttrs[theMapIndex].fAllocatedLen = theLen;
theAttrs[theMapIndex].fAllocatedInternally = true;
}
// 先找到新数据要拷贝到的正确位置
void *attributeBufferPtr;
if ((dataType != qtssAttrDataTypeCharArray) || ((numValues < 2) && (inIndex == 0)))
{
attributeBufferPtr = theAttrs[theMapIndex].fAttributeData.Ptr + (inLen * inIndex);
theAttrs[theMapIndex].fAttributeData.Len = inLen;
} else {
attributeBufferPtr = NEW char[inLen + 1]; // 为什么这里又要分配空间？？？
char* tempBuffer = (char*)attributeBufferPtr;
tempBuffer[inLen] = '\0';
char** valuePtr=(char**)(theAttrs[theMapIndex].fAttributeData.Ptr+(attrLen *
inIndex));
if(inIndex < numValues) delete *valuePtr;
*valuePtr = (char*)attributeBufferPtr;
}
// 拷贝新数据
::memcpy(attributeBufferPtr, inBuffer, inLen);
if(inIndex>=theAttrs[theMapIndex].fNumAttributes) theAttrs[theMapIndex].fNumAttributes++;
if (((fMap == NULL) || fMap->CompleteFunctionsAllowed()) && !(inFlags &
kDontCallCompletionRoutine))
// SetValueComplete是虚函数，不同的继承类有不同的实现
this->SetValueComplete(theMapIndex, theMap, inIndex, attributeBufferPtr, inLen);
? QTSSDictionaryMap类
这个类对象对应着一个具体的QTSS Object，用来描述这个Object的所有属性（或者说参数）。
它有一个QTSSAttrInfoDict**类型的成员fAttrArray，用来记录这个dict map所对应的Object的所有
属性信息。
QTSSAttrInfoDict类（对一个属性的具体描述）的定义为：
class QTSSAttrInfoDict: public QTSSDictionary
{
public:
struct AttrInfo {
char fAttrName[QTSS_MAX_ATTRIBUTE_NAME_SIZE + 1];
QTSS_AttrFunctionPtr fFuncPtr;
QTSS_AttrDataType fAttrDataType;
QTSS_AttrPermission fAttrPermission;
};
QTSSAttrInfoDict();
virtual ~QTSSAttrInfoDict();
private:
AttrInfo fAttrInfo;
QTSS_AttributeID fID;
static AttrInfo sAttributes[];
friend class QTSSDictionaryMap;
};
// 实际上kAttrInfoDictIndex所对应的dict map是专门用来描述每个属性的，也就是说这个dict
// map所对应的object是某一个属性，是属性的属性。它的属性个数是qtssAttrInfoNumParams(4):
// 属性名称、属性ID、属性数据类型、属性权限。
// 而QTSSAttrInfoDict被用来描述一个具体的属性，所以这里传入这个dict map来初始化基类
// QTSSDictionary。
QTSSAttrInfoDict::QTSSAttrInfoDict() // 构建函数
:QTSSDictionary(QTSSDictionaryMap::GetMap(QTSSDictionaryMap::kAttrInfoDictIndex)),
fID(qtssIllegalAttrID)
QTSSAttrInfoDict::AttrInfo QTSSAttrInfoDict::sAttributes[] = {
{"qtssAttrName", NULL,qtssAttrDataTypeCharArray,qtssAttrModeRead |
qtssAttrModePreempSafe},
{"qtssAttrID", NULL, qtssAttrDataTypeUInt32, qtssAttrModeRead | qtssAttrModePreempSafe },
{"qtssAttrDataType",NULL,qtssAttrDataTypeUInt32,qtssAttrModeRead |
qtssAttrModePreempSafe},
{qtssAttrPermissions",NULL,qtssAttrDataTypeUInt32,qtssAttrModeRead|qtssAttrModePreempSafe}
}
（1）、构建函数
根据要描述的Object的属性个数来初始化fAttrArray。
QTSSDictionaryMap::QTSSDictionaryMap(UInt32 inNumReservedAttrs, UInt32 inFlags)
: fNextAvailableID(inNumReservedAttrs), fNumValidAttrs(inNumReservedAttrs),
fAttrArraySize(inNumReservedAttrs), fFlags(inFlags)
{
... ...
fAttrArray = NEW QTSSAttrInfoDict*[fAttrArraySize];
::memset(fAttrArray, 0, sizeof(QTSSAttrInfoDict*) * fAttrArraySize);
}
（2）、QTSSDictionaryMap::Initialize()
首先创建并初始化kAttrInfoDictIndex所对应的dict map。
// Have to do this one first because this dict map is used by all the dict maps.
sDictionaryMaps[kAttrInfoDictIndex] = new QTSSDictionaryMap(qtssAttrInfoNumParams);
// setup the Attr Info attributes before constructing any other dictionaries.
for (Uint32 x = 0; x < qtssAttrInfoNumParams; x++)
sDictionaryMaps[kAttrInfoDictIndex]->SetAttribute(x,
QTSSAttrInfoDict::sAttributes[x].fAttrName,
QTSSAttrInfoDict::sAttributes[x].fFuncPtr,
QTSSAttrInfoDict::sAttributes[x].fAttrDataType,
QTSSAttrInfoDict::sAttributes[x].fAttrPermission);
创建各种类型的dict map（比如kServerDictIndex、kPrefsDictIndex、kTextMessagesDictIndex、
kServiceDictIndex、kRTPStreamDictIndex等)，保存在sDictionaryMaps数组里。
（3）、QTSSDictionaryMap::SetAttribute
... ...
// 创建描述属性的QTSSAttrInfoDict对象，将属性包含的信息（ID、名称、函数指针、数据类型、
// 权限）保存下来。
fAttrArray[theIndex] = NEW QTSSAttrInfoDict;
fAttrArray[theIndex]->fID = inID;
::strcpy(&fAttrArray[theIndex]->fAttrInfo.fAttrName[0], inAttrName);
fAttrArray[theIndex]->fAttrInfo.fFuncPtr = inFuncPtr;
fAttrArray[theIndex]->fAttrInfo.fAttrDataType = inDataType;
fAttrArray[theIndex]->fAttrInfo.fAttrPermission = inPermission;
// 将属性四个成员(名称、ID、数据类型、权限)的相关信息通过基类QTSSDictionary保存起来。
fAttrArray[theIndex]->SetVal(qtssAttrName, &fAttrArray[theIndex]->fAttrInfo.fAttrName[0],
theNameLen);
fAttrArray[theIndex]->SetVal(qtssAttrID, &fAttrArray[theIndex]->fID,
sizeof(fAttrArray[theIndex]->fID));
fAttrArray[theIndex]->SetVal(qtssAttrDataType, &fAttrArray[theIndex]
->fAttrInfo.fAttrDataType, sizeof(fAttrArray[theIndex]->fAttrInfo.fAttrDataType));
fAttrArray[theIndex]->SetVal(qtssAttrPermissions, &fAttrArray[theIndex]
->fAttrInfo.fAttrPermission, sizeof(fAttrArray[theIndex]
->fAttrInfo.fAttrPermission));