QT分析之网络编程
原文地址：http://blog.163.com/net_worm/blog/static/127702419201002842553382/
首先对Windows下的网络编程总结一下：
如果是服务器，其WinSDK调用分别为：
1 WSAStartup() -> socket() -> htons() / htonl() -> bind() -> listen() -> accept() -> recv() / send() -> closesocket() -> WSACleanup()
如果是客户端程序，其调用序列为：
1 WSAStartup() -> socket() -> htons() / htonl() -> connect() -> recv() / send() -> closesocket() -> WSACleanup()
前面转贴的客户端（WinSocket温习）程序中，收到信息就在console打印出来然后退出了；在一般的应用中，通常是要一直等待收发消息的，直到程序确认退出才关闭socket。如果用一个轮询就会占用很多的CPU资源，所以很多嵌入式设计中会用一个WaitForMultiObject调用，等待退出命令或者超时，然后退出或进行下一轮信息接受。在Windows平台下也有一些比较高明的设计，使用异步socket，然后用异步选择的办法，实现多线程和事件的并发。在WinSocket中，同样也有一套异步Socket函数，那就是使用WSAAsyncSelect()及其配合函数。具体可以参考MSDN。QT在Windows平台上的实现，肯定也跟这些SDK调用有关。
按照这个思路，果然在QT代码里面找到了Qnativesocketengine_win.cpp，WSAStartup()，WSASocket()等序列WSA函数都有。QNativeSocketEnginePrivate类把这些SDK封装成：createNewSocket()、option()、setOption()、nativeConnect()、nativeBind()、nativeListen()、nativeAccept()、nativeWrite()、nativeRead()、nativeSelect()、nativeClose()等。按照QT的设计，QPrivate类是数据类；Q类应该是主类。接着看QNativeSocket类的继承：
1 QNativeSocketEngine : public QAbstractSocketEngine : public QObject
QAbstractSocketEngine类是使用了大量纯虚函数的定义。继续深入查看，发现大量有关的类：QAbstractSocket，SocketAsyncHandler，QTcpSocket，QUdpSocket等，看来我要先了解下QT网络编程体系再进一步分析之
之前没有看QT自带的文档，看了doc之后对QT的网络体系有一个大致的了解：
QNatvieSocketEnginePrivate是OS相关的API封装，和QNativeSocketEngine一起构成具体平台SOCKET实现；
QTcpSocket、QUdpSocket、QTcpServer构成底层的应用API；QSslSocket是SSL加密相关API；
QHttp、QFtp构成高层次应该API；
QNetworkAccessManager、QNetworkRequest、QNetworkReply是高度抽象的网络层。
分析TCP的例子fortuneclient，运行起来按了[Get
Fortune]按钮之后，调用的是Client::requestNewFortune()。
1 void Client::requestNewFortune() 2 { 3 getFortuneButton->setEnabled(false); 4 blockSize = 0; 5 tcpSocket->abort(); 6 tcpSocket->connectToHost(hostLineEdit->text(), portLineEdit->text().toInt()); 7 }
具体看QTcpSocket::connectToHost()的代码
1 void QAbstractSocket::connectToHost(const QString &hostName, quint16 port, 2 OpenMode openMode) 3 { 4 QMetaObject::invokeMethod(this, "connectToHostImplementation", 5 Qt::DirectConnection, 6 Q_ARG(QString, hostName), 7 Q_ARG(quint16, port), 8 Q_ARG(OpenMode, openMode)); 9 }
调用的是QAbstractSocket::connectToHostImplementation()。
1 void QAbstractSocket::connectToHostImplementation(const QString &hostName, quint16 port, 2 OpenMode openMode) 3 { 4 Q_D(QAbstractSocket); 5 if (d->state == ConnectedState || d->state == ConnectingState || d->state == ClosingState) { 6 qWarning("QAbstractSocket::connectToHost() called when already connecting/connected to \"%s\"", qPrintable(hostName)); 7 return; 8 } 9 10 d->hostName = hostName; 11 d->port = port; 12 d->state = UnconnectedState; 13 d->readBuffer.clear(); 14 d->writeBuffer.clear(); 15 d->abortCalled = false; 16 d->closeCalled = false; 17 d->pendingClose = false; 18 d->localPort = 0; 19 d->peerPort = 0; 20 d->localAddress.clear(); 21 d->peerAddress.clear(); 22 d->peerName = hostName; 23 if (d->hostLookupId != -1) { 24 QHostInfo::abortHostLookup(d->hostLookupId); 25 d->hostLookupId = -1; 26 } 27 28 #ifndef QT_NO_NETWORKPROXY 29 // Get the proxy information 30 d->resolveProxy(hostName, port); 31 if (d->proxyInUse.type() == QNetworkProxy::DefaultProxy) { 32 // failed to setup the proxy 33 d->socketError = QAbstractSocket::UnsupportedSocketOperationError; 34 setErrorString(QAbstractSocket::tr("Operation on socket is not supported")); 35 emit error(d->socketError); 36 return; 37 } 38 #endif 39 40 if (!d_func()->isBuffered) 41 openMode |= QAbstractSocket::Unbuffered; 42 QIODevice::open(openMode); // ？？ 43 d->state = HostLookupState; 44 emit stateChanged(d->state); 45 46 QHostAddress temp; 47 if (temp.setAddress(hostName)) { 48 QHostInfo info; 49 info.setAddresses(QList<QHostAddress>() << temp); 50 d->_q_startConnecting(info); 51 #ifndef QT_NO_NETWORKPROXY 52 } else if (d->proxyInUse.capabilities() & QNetworkProxy::HostNameLookupCapability) { 53 // the proxy supports connection by name, so use it 54 d->startConnectingByName(hostName); 55 return; 56 #endif 57 } else { 58 if (d->threadData->eventDispatcher) 59 d->hostLookupId = QHostInfo::lookupHost(hostName, this, SLOT(_q_startConnecting(QHostInfo))); 60 } 61 }
继续调用QAbstractSocket::_q_startConnecting()，是QAbstractSocket的私有信号。简单来说，_q_startConnecting()就是调用了_q_connectToNextAddress()而已。
1 void QAbstractSocketPrivate::_q_connectToNextAddress() 2 { 3 Q_Q(QAbstractSocket); 4 do { 5 // Check for more pending addresses 6 if (addresses.isEmpty()) { 7 state = QAbstractSocket::UnconnectedState; 8 if (socketEngine) { 9 if ((socketEngine->error() == QAbstractSocket::UnknownSocketError 10 ) && socketEngine->state() == QAbstractSocket::ConnectingState) { 11 socketError = QAbstractSocket::ConnectionRefusedError; 12 q->setErrorString(QAbstractSocket::tr("Connection refused")); 13 } else { 14 socketError = socketEngine->error(); 15 q->setErrorString(socketEngine->errorString()); 16 } 17 } else { 18 // socketError = QAbstractSocket::ConnectionRefusedError; 19 // q->setErrorString(QAbstractSocket::tr("Connection refused")); 20 } 21 emit q->stateChanged(state); 22 emit q->error(socketError); 23 return; 24 } 25 26 // Pick the first host address candidate 27 host = addresses.takeFirst(); 28 29 #if defined(QT_NO_IPV6) 30 if (host.protocol() == QAbstractSocket::IPv6Protocol) { 31 // If we have no IPv6 support, then we will not be able to 32 // connect. So we just pretend we didn't see this address. 33 continue; 34 } 35 #endif 36 37 if (!initSocketLayer(host.protocol())) { 38 // hope that the next address is better 39 continue; 40 } 41 42 // Tries to connect to the address. If it succeeds immediately 43 // (localhost address on BSD or any UDP connect), emit 44 // connected() and return. 45 if (socketEngine->connectToHost(host, port)) { 46 //_q_testConnection(); 47 fetchConnectionParameters(); 48 return; 49 } 50 51 // cache the socket descriptor even if we're not fully connected yet 52 cachedSocketDescriptor = socketEngine->socketDescriptor(); 53 54 // Check that we're in delayed connection state. If not, try 55 // the next address 56 if (socketEngine->state() != QAbstractSocket::ConnectingState) { 57 continue; 58 } 59 60 // Start the connect timer. 61 if (threadData->eventDispatcher) { 62 if (!connectTimer) { 63 connectTimer = new QTimer(q); 64 QObject::connect(connectTimer, SIGNAL(timeout()), 65 q, SLOT(_q_abortConnectionAttempt()), 66 Qt::DirectConnection); 67 } 68 connectTimer->start(QT_CONNECT_TIMEOUT); 69 } 70 71 // Wait for a write notification that will eventually call 72 // _q_testConnection(). 73 socketEngine->setWriteNotificationEnabled(true); 74 break; 75 } while (state != QAbstractSocket::ConnectedState); 76 }
上面关键的三句，实际是把WinSocket编程中的简单过程分成三个阶段：socket初始化；connect到远程目标；设定Timer定时查看并处理Select的情况（收发数据或者关闭socket）。这里主要看前面两个：初始化和连接，select的处理放到明天分析。
1、初始化
1 bool QAbstractSocketPrivate::initSocketLayer(QAbstractSocket::NetworkLayerProtocol protocol) 2 { 3 #ifdef QT_NO_NETWORKPROXY 4 // this is here to avoid a duplication of the call to createSocketEngine below 5 static const QNetworkProxy &proxyInUse = *(QNetworkProxy *)0; 6 #endif 7 8 Q_Q(QAbstractSocket); 9 10 resetSocketLayer(); 11 socketEngine = QAbstractSocketEngine::createSocketEngine(q->socketType(), proxyInUse, q); 12 if (!socketEngine) { 13 socketError = QAbstractSocket::UnsupportedSocketOperationError; 14 q->setErrorString(QAbstractSocket::tr("Operation on socket is not supported")); 15 return false; 16 } 17 if (!socketEngine->initialize(q->socketType(), protocol)) { 18 socketError = socketEngine->error(); 19 q->setErrorString(socketEngine->errorString()); 20 return false; 21 } 22 23 if (threadData->eventDispatcher) 24 socketEngine->setReceiver(this); 25 26 return true; 27 } 28 29 QAbstractSocketEngine *QAbstractSocketEngine::createSocketEngine(QAbstractSocket::SocketType socketType, const QNetworkProxy &proxy, QObject *parent) 30 { 31 #ifndef QT_NO_NETWORKPROXY 32 // proxy type must have been resolved by now 33 if (proxy.type() == QNetworkProxy::DefaultProxy) 34 return 0; 35 #endif 36 37 QMutexLocker locker(&socketHandlers()->mutex); 38 for (int i = 0; i < socketHandlers()->size(); i++) { 39 if (QAbstractSocketEngine *ret = socketHandlers()->at(i)->createSocketEngine(socketType, proxy, parent)) 40 return ret; 41 } 42 43 return new QNativeSocketEngine(parent); 44 }
上面可以知道socketEngine->initialize()实际调用的是QNativeSocketEngine::initialize()
1 bool QNativeSocketEngine::initialize(QAbstractSocket::SocketType socketType, QAbstractSocket::NetworkLayerProtocol protocol) 2 { 3 Q_D(QNativeSocketEngine); 4 if (isValid()) 5 close(); 6 7 #if defined(QT_NO_IPV6) 8 if (protocol == QAbstractSocket::IPv6Protocol) { 9 d->setError(QAbstractSocket::UnsupportedSocketOperationError, 10 QNativeSocketEnginePrivate::NoIpV6ErrorString); 11 return false; 12 } 13 #endif 14 15 // Create the socket 16 if (!d->createNewSocket(socketType, protocol)) { 17 return false; 18 } 19 20 // Make the socket nonblocking. 21 if (!setOption(NonBlockingSocketOption, 1)) { 22 d->setError(QAbstractSocket::UnsupportedSocketOperationError, 23 QNativeSocketEnginePrivate::NonBlockingInitFailedErrorString); 24 close(); 25 return false; 26 } 27 28 // Set the broadcasting flag if it's a UDP socket. 29 if (socketType == QAbstractSocket::UdpSocket 30 && !setOption(BroadcastSocketOption, 1)) { 31 d->setError(QAbstractSocket::UnsupportedSocketOperationError, 32 QNativeSocketEnginePrivate::BroadcastingInitFailedErrorString); 33 close(); 34 return false; 35 } 36 37 // Make sure we receive out-of-band data 38 if (socketType == QAbstractSocket::TcpSocket 39 && !setOption(ReceiveOutOfBandData, 1)) { 40 qWarning("QNativeSocketEngine::initialize unable to inline out-of-band data"); 41 } 42 43 // Set the send and receive buffer sizes to a magic size, found 44 // most optimal for our platforms. 45 setReceiveBufferSize(49152); 46 setSendBufferSize(49152); 47 48 d->socketType = socketType; 49 d->socketProtocol = protocol; 50 return true; 51 }
至此，初始化过程完成，socket被设定为非阻塞模式（也就是Select会超时方式）。
2、connect到远程目标
1 bool QNativeSocketEngine::connectToHost(const QHostAddress &address, quint16 port) 2 { 3 Q_D(QNativeSocketEngine); 4 Q_CHECK_VALID_SOCKETLAYER(QNativeSocketEngine::connectToHost(), false); 5 6 #if defined (QT_NO_IPV6) 7 if (address.protocol() == QAbstractSocket::IPv6Protocol) { 8 d->setError(QAbstractSocket::UnsupportedSocketOperationError, 9 QNativeSocketEnginePrivate::NoIpV6ErrorString); 10 return false; 11 } 12 #endif 13 if (!d->checkProxy(address)) 14 return false; 15 16 Q_CHECK_STATES(QNativeSocketEngine::connectToHost(), 17 QAbstractSocket::UnconnectedState, QAbstractSocket::ConnectingState, false); 18 19 d->peerAddress = address; 20 d->peerPort = port; 21 bool connected = d->nativeConnect(address, port); 22 if (connected) 23 d->fetchConnectionParameters(); 24 25 return connected; 26 }
连接相对简单。
3、读取信息
在QAbstractSocket中，有两个成员是收发数据用的：readData()、writeData()
readData()有两种读取方式：有缓冲和无缓冲方式。基本原理是一致的，简单其见只分析无缓冲直接读取方式。
1 qint64 QAbstractSocket::readData(char *data, qint64 maxSize) 2 { 3 Q_D(QAbstractSocket); 4 if (d->socketEngine && !d->socketEngine->isReadNotificationEnabled() && d->socketEngine->isValid()) 5 d->socketEngine->setReadNotificationEnabled(true); 6 7 if (!d->isBuffered) { 8 if (!d->socketEngine) 9 return -1; // no socket engine is probably EOF 10 qint64 readBytes = d->socketEngine->read(data, maxSize); 11 if (readBytes < 0) { 12 d->socketError = d->socketEngine->error(); 13 setErrorString(d->socketEngine->errorString()); 14 } 15 if (!d->socketEngine->isReadNotificationEnabled()) 16 d->socketEngine->setReadNotificationEnabled(true); 17 return readBytes; 18 } 19 20 if (d->readBuffer.isEmpty()) 21 // if we're still connected, return 0 indicating there may be more data in the future 22 // if we're not connected, return -1 indicating EOF 23 return d->state == QAbstractSocket::ConnectedState ? qint64(0) : qint64(-1); 24 25 // If readFromSocket() read data, copy it to its destination. 26 if (maxSize == 1) { 27 *data = d->readBuffer.getChar(); 28 return 1; 29 } 30 31 qint64 bytesToRead = qMin(qint64(d->readBuffer.size()), maxSize); 32 qint64 readSoFar = 0; 33 while (readSoFar < bytesToRead) { 34 const char *ptr = d->readBuffer.readPointer(); 35 int bytesToReadFromThisBlock = qMin(int(bytesToRead - readSoFar), 36 d->readBuffer.nextDataBlockSize()); 37 memcpy(data + readSoFar, ptr, bytesToReadFromThisBlock); 38 readSoFar += bytesToReadFromThisBlock; 39 d->readBuffer.free(bytesToReadFromThisBlock); 40 } 41 42 return readSoFar; 43 }
从前面（二）可以知道，socketEngine->read()实际调用的是QNativeSocketEngine::read()
1 qint64 QNativeSocketEngine::read(char *data, qint64 maxSize) 2 { 3 Q_D(QNativeSocketEngine); 4 Q_CHECK_VALID_SOCKETLAYER(QNativeSocketEngine::read(), -1); 5 Q_CHECK_STATES(QNativeSocketEngine::read(), QAbstractSocket::ConnectedState, QAbstractSocket::BoundState, -1); 6 7 qint64 readBytes = d->nativeRead(data, maxSize); 8 9 // Handle remote close 10 if (readBytes == 0 && d->socketType == QAbstractSocket::TcpSocket) { 11 d->setError(QAbstractSocket::RemoteHostClosedError, 12 QNativeSocketEnginePrivate::RemoteHostClosedErrorString); 13 close(); 14 return -1; 15 } 16 return readBytes; 17 }
除了一些相关的检查，就是调用QNativeSocketPrivate::nativeRead()
1 qint64 QNativeSocketEnginePrivate::nativeRead(char *data, qint64 maxLength) 2 { 3 qint64 ret = -1; 4 WSABUF buf; 5 buf.buf = data; 6 buf.len = maxLength; 7 DWORD flags = 0; 8 DWORD bytesRead = 0; 9 #if defined(Q_OS_WINCE) 10 WSASetLastError(0); 11 #endif 12 if (::WSARecv(socketDescriptor, &buf, 1, &bytesRead, &flags, 0,0) == SOCKET_ERROR) { 13 int err = WSAGetLastError(); 14 WS_ERROR_DEBUG(err); 15 switch (err) { 16 case WSAEWOULDBLOCK: 17 ret = -2; 18 break; 19 case WSAEBADF: 20 case WSAEINVAL: 21 setError(QAbstractSocket::NetworkError, ReadErrorString); 22 break; 23 case WSAECONNRESET: 24 case WSAECONNABORTED: 25 // for tcp sockets this will be handled in QNativeSocketEngine::read 26 ret = 0; 27 break; 28 default: 29 break; 30 } 31 } else { 32 if (WSAGetLastError() == WSAEWOULDBLOCK) 33 ret = -2; 34 else 35 ret = qint64(bytesRead); 36 } 37 38 return ret; 39 }
至此，调用Windows API读取数据。
4、发送数据
同样分有缓存与无缓存方式，对无缓存方式：
1 qint64 QAbstractSocket::writeData(const char *data, qint64 size) 2 { 3 Q_D(QAbstractSocket); 4 if (d->state == QAbstractSocket::UnconnectedState) { 5 d->socketError = QAbstractSocket::UnknownSocketError; 6 setErrorString(tr("Socket is not connected")); 7 return -1; 8 } 9 10 if (!d->isBuffered) { 11 qint64 written = d->socketEngine->write(data, size); 12 if (written < 0) { 13 d->socketError = d->socketEngine->error(); 14 setErrorString(d->socketEngine->errorString()); 15 } else if (!d->writeBuffer.isEmpty()) { 16 d->socketEngine->setWriteNotificationEnabled(true); 17 } 18 if (written >= 0) 19 emit bytesWritten(written); 20 return written; 21 } 22 23 char *ptr = d->writeBuffer.reserve(size); 24 if (size == 1) 25 *ptr = *data; 26 else 27 memcpy(ptr, data, size); 28 29 qint64 written = size; 30 31 if (d->socketEngine && !d->writeBuffer.isEmpty()) 32 d->socketEngine->setWriteNotificationEnabled(true); 33 return written; 34 }
查看QNativeSocketEngine::write()：
1 qint64 QNativeSocketEngine::write(const char *data, qint64 size) 2 { 3 Q_D(QNativeSocketEngine); 4 Q_CHECK_VALID_SOCKETLAYER(QNativeSocketEngine::write(), -1); 5 Q_CHECK_STATE(QNativeSocketEngine::write(), QAbstractSocket::ConnectedState, -1); 6 return d->nativeWrite(data, size); 7 } 8 9 qint64 QNativeSocketEnginePrivate::nativeWrite(const char *data, qint64 len) 10 { 11 Q_Q(QNativeSocketEngine); 12 qint64 ret = 0; 13 // don't send more than 49152 per call to WSASendTo to avoid getting a WSAENOBUFS 14 for (;;) { 15 qint64 bytesToSend = qMin<qint64>(49152, len - ret); 16 WSABUF buf; 17 buf.buf = (char*)data + ret; 18 buf.len = bytesToSend; 19 DWORD flags = 0; 20 DWORD bytesWritten = 0; 21 22 int socketRet = ::WSASend(socketDescriptor, &buf, 1, &bytesWritten, flags, 0,0); 23 24 ret += qint64(bytesWritten); 25 26 if (socketRet != SOCKET_ERROR) { 27 if (ret == len) 28 break; 29 else 30 continue; 31 } else if (WSAGetLastError() == WSAEWOULDBLOCK) { 32 break; 33 } else { 34 int err = WSAGetLastError(); 35 WS_ERROR_DEBUG(err); 36 switch (err) { 37 case WSAECONNRESET: 38 case WSAECONNABORTED: 39 ret = -1; 40 setError(QAbstractSocket::NetworkError, WriteErrorString); 41 q->close(); 42 break; 43 default: 44 break; 45 } 46 break; 47 } 48 } 49 return ret; 50 }
至此分析完毕。
前面分析中，一个问题一直没有解决：新生成的SOCKET是什么时候加入WSASelect()的？另外还有一个不是很大的问题，close流程。
在
1 QEventDispatcherWin32Private::doWsaAsyncSelect()
中WSAAsyncSelect()设置一个断点，观察call stack:
1 QtCored4.dll!QEventDispatcherWin32Private::doWsaAsyncSelect(int socket=0x00001628) 行633 C++ 2 QtCored4.dll!QEventDispatcherWin32::registerSocketNotifier(QSocketNotifier * notifier=0x00c6f248) 行829 C++ 3 QtCored4.dll!QSocketNotifier::QSocketNotifier(int socket=0x00001628, QSocketNotifier::Type type=Write, QObject * parent=0x00c66228) 行185 C++ 4 QtNetworkd4.dll!QWriteNotifier::QWriteNotifier(int fd=0x00001628, QNativeSocketEngine * parent=0x00c66228) 行1053 + 0x1a 字节 C++ 5 QtNetworkd4.dll!QNativeSocketEngine::setWriteNotificationEnabled(bool enable=true) 行1118 + 0x2d 字节 C++ 6 QtNetworkd4.dll!QAbstractSocketPrivate::_q_connectToNextAddress() 行996 C++ 7 QtNetworkd4.dll!QAbstractSocketPrivate::_q_startConnecting(const QHostInfo & hostInfo={...}) 行890 C++ 8 QtNetworkd4.dll!QAbstractSocket::qt_metacall(QMetaObject::Call _c=InvokeMetaMethod, int _id=0x0000000a, void * * _a=0x00c6e510) 行104 + 0x16 字节 C++ 9 QtNetworkd4.dll!QTcpSocket::qt_metacall(QMetaObject::Call _c=InvokeMetaMethod, int _id=0x00000012, void * * _a=0x00c6e510) 行58 + 0x14 字节 C++ 10 QtCored4.dll!QMetaCallEvent::placeMetaCall(QObject * object=0x00c4f790) 行478 C++ 11 QtCored4.dll!QObject::event(QEvent * e=0x00c4d8a0) 行1102 + 0x14 字节 C++ 12 QtGuid4.dll!QApplicationPrivate::notify_helper(QObject * receiver=0x00c4f790, QEvent * e=0x00c4d8a0) 行4065 + 0x11 字节 C++ 13 QtGuid4.dll!QApplication::notify(QObject * receiver=0x00c4f790, QEvent * e=0x00c4d8a0) 行3605 + 0x10 字节 C++ 14 QtCored4.dll!QCoreApplication::notifyInternal(QObject * receiver=0x00c4f790, QEvent * event=0x00c4d8a0) 行610 + 0x15 字节 C++ 15 QtCored4.dll!QCoreApplication::sendEvent(QObject * receiver=0x00c4f790, QEvent * event=0x00c4d8a0) 行213 + 0x39 字节 C++ 16 QtCored4.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver=0x00000000, int event_type=0x00000000, QThreadData * data=0x00bc8890) 行1247 + 0xd 字节 C++ 17 QtCored4.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags={...}) 行679 + 0x10 字节 C++ 18 QtGuid4.dll!QGuiEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags={...}) 行1182 + 0x15 字节 C++ 19 QtCored4.dll!QEventLoop::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags={...}) 行150 C++ 20 QtCored4.dll!QEventLoop::exec(QFlags<enum QEventLoop::ProcessEventsFlag> flags={...}) 行201 + 0x2d 字节 C++ 21 QtGuid4.dll!QDialog::exec() 行499 C++ 22 fortuneclient.exe!main(int argc=0x00000001, char * * argv=0x00bc8750) 行51 + 0x9 字节 C++ 23 fortuneclient.exe!WinMain(HINSTANCE__ * instance=0x00400000, HINSTANCE__ * prevInstance=0x00000000, char * __formal=0x001520e2, int cmdShow=0x00000001) 行137 + 0x12 字节 C++ 24 fortuneclient.exe!__tmainCRTStartup() 行574 + 0x35 字节 C 25 fortuneclient.exe!WinMainCRTStartup() 行399 C 26 kernel32.dll!7c82f23b()
[下面的框架可能不正确和/或缺失，没有为 kernel32.dll 加载符号]
看QNativeSocketEngine::setWriteNotificationEnabled()的代码实现：
1 void QNativeSocketEngine::setWriteNotificationEnabled(bool enable) 2 { 3 Q_D(QNativeSocketEngine); 4 if (d->writeNotifier) { 5 d->writeNotifier->setEnabled(enable); 6 } else if (enable && d->threadData->eventDispatcher) { 7 d->writeNotifier = new QWriteNotifier(d->socketDescriptor, this); 8 d->writeNotifier->setEnabled(true); 9 } 10 }
在QWriteNotifier对象新建的时候，引起其父类的构建：QSocketNotifier
1 QSocketNotifier::QSocketNotifier(int socket, Type type, QObject *parent) 2 : QObject(parent) 3 { 4 if (socket < 0) 5 qWarning("QSocketNotifier: Invalid socket specified"); 6 sockfd = socket; 7 sntype = type; 8 snenabled = true; 9 10 Q_D(QObject); 11 if (!d->threadData->eventDispatcher) { 12 qWarning("QSocketNotifier: Can only be used with threads started with QThread"); 13 } else { 14 d->threadData->eventDispatcher->registerSocketNotifier(this); 15 } 16 }
原来是通过获取当前线程数据得到Dispatcher的指针（QEventDispatcherWin32），通过其注册QNativeSocketEngine对象自己本身。
1 void QEventDispatcherWin32::registerSocketNotifier(QSocketNotifier *notifier) 2 { 3 Q_ASSERT(notifier); 4 int sockfd = notifier->socket(); 5 int type = notifier->type(); 6 7 Q_D(QEventDispatcherWin32); 8 QSNDict *sn_vec[3] = { &d->sn_read, &d->sn_write, &d->sn_except }; 9 QSNDict *dict = sn_vec[type]; 10 11 if (QCoreApplication::closingDown()) // ### d->exitloop? 12 return; // after sn_cleanup, don't reinitialize. 13 14 if (dict->contains(sockfd)) { 15 const char *t[] = { "Read", "Write", "Exception" }; 16 /* Variable "socket" below is a function pointer. */ 17 qWarning("QSocketNotifier: Multiple socket notifiers for " 18 "same socket %d and type %s", sockfd, t[type]); 19 } 20 21 QSockNot *sn = new QSockNot; 22 sn->obj = notifier; 23 sn->fd = sockfd; 24 dict->insert(sn->fd, sn); 25 26 if (d->internalHwnd) 27 d->doWsaAsyncSelect(sockfd); 28 }
在这里跟前面分析的QEventDispatcherWin32消息处理搭上关系了，把QWriteNotifier对象加入到系统的列表中；在QApplication::exec()的消息循环中，就能够获取目标对象了。
今天分析QNetworkAccessManager、QNetworkRequest和QNetworkReply组成的高级抽象API序列。在动手之前，把doc中有关QNetworkAccessManager的介绍看了一遍。其使用方法大致是：
1 QNetworkAccessManager * manager = new QNetworkAccessManager(this); 2 QNetworkRequest request; 3 request.setUrl(QUrl("http://www.baidu.com")); 4 QNetworkReply * reply = manager->get(request); 5 connect(reply, SIGNAL(readyRead()), this, SLOT(slotReadyRead()));
关键是后面的三行：设定URL、发送并获取响应、读取数据。
在QT自带的例子中也有QNetworkAccessManager的应用：downloadmanager
单步跟踪就用downloadmanager这个例子。
在动手跟踪之前，总结了几个问题：
1、QNetworkAccessManager是更高级的抽象，那么怎么跟QTcpSocket/QUdpSocket联系起来的呢？
2、如果没有跟QTcpSocket联系起来，那么又是怎么跟WSA序列WinAPI联系起来的呢？
3、整个逻辑过程是怎么的呢？
4、获取的（图片或者网页）数据保存在什么地方？
5、跟HTTP或者FTP有关的Cookie、认证等怎么实现的？
6、HTTP的Session相关功能实现了吗？怎么实现的？
在动手分析前，简单介绍一下HTTP协议。HTTP协议是一种为分布式，合作式，超媒体信息系统。它是一种通用的，无状态（stateless）的协议，除了应用于超文本传输外，它也可以应用于诸如名称服务器和分布对象管理系统之类的系统，这可以通过扩展它的请求方法，错误代码和报头来实现。HTTP的一个特点是数据表现形式是可输入的和可协商性的，这就允许系统能被建立而独立于数据传输。HTTP在1990年WWW全球信息刚刚起步的时候就得到了应用。该规范定义的协议用“HTTP/1.1”表示，是对RFC2608[33]的更新。 HTTP协议是通过定义一序列的动作（协议文本中称为方法），来完成数据的传输通信。HTTP1.1版本中有这些方法：get、post、head、options、put、delete、trace、connect。
get方法用于获取URI资源，是最为常用的一种方法。
post方法用于向指定URI提交内容，服务器端响应其行为，该方法也极为常用。
head方法向URI发送请求，仅仅只需要获得响应的协议头。
put方法用于向URI发送请求，若URI不存在，则要求服务器端根据请求创建资源。当URI存在时，服务器端必须接受请求内容，将其作为URI资源的修改后版本。
delete方法用于删除URI标识的指定资源。
trace方法用于激活服务器端对请求的循环反馈，反馈作为http响应的正文内容被传输回客户端。
connect方法通常被用于使用代理连接。
更详细的内容请查看相关资料。
回到QT系统，manager->get()调用其实就是HTTP/1.1协议中get方法的实现。
1 QNetworkReply *QNetworkAccessManager::get(const QNetworkRequest &request) 2 { 3 return d_func()->postProcess(createRequest(QNetworkAccessManager::GetOperation, request)); 4 }
上面的一行程序中有两个调用
1 QNetworkAccessManager::createRequest() 2 QNetworkAccessManagerPrivate::postProcess()
先来看createRequest()，两个参数：第一个参数表示使用Get方法；第二个参数是目标网址。
1 QNetworkReply *QNetworkAccessManager::createRequest(QNetworkAccessManager::Operation op, 2 const QNetworkRequest &req, 3 QIODevice *outgoingData) 4 { 5 Q_D(QNetworkAccessManager); 6 7 bool isLocalFile = req.url().isLocalFile(); 8 QString scheme = req.url().scheme().toLower(); 9 10 // fast path for GET on file:// URLs 11 // The QNetworkAccessFileBackend will right now only be used for PUT 12 if ((op == QNetworkAccessManager::GetOperation || op == QNetworkAccessManager::HeadOperation) 13 && (isLocalFile || scheme == QLatin1String("qrc"))) { 14 return new QNetworkReplyFileImpl(this, req, op); 15 } 16 17 if ((op == QNetworkAccessManager::GetOperation || op == QNetworkAccessManager::HeadOperation) 18 && scheme == QLatin1String("data")) { 19 return new QNetworkReplyDataImpl(this, req, op); 20 } 21 22 // A request with QNetworkRequest::AlwaysCache does not need any bearer management 23 QNetworkRequest::CacheLoadControl mode = 24 static_cast<QNetworkRequest::CacheLoadControl>( 25 req.attribute(QNetworkRequest::CacheLoadControlAttribute, 26 QNetworkRequest::PreferNetwork).toInt()); 27 if (mode == QNetworkRequest::AlwaysCache 28 && (op == QNetworkAccessManager::GetOperation 29 || op == QNetworkAccessManager::HeadOperation)) { 30 // FIXME Implement a QNetworkReplyCacheImpl instead, see QTBUG-15106 31 QNetworkReplyImpl *reply = new QNetworkReplyImpl(this); 32 QNetworkReplyImplPrivate *priv = reply->d_func(); 33 priv->manager = this; 34 priv->backend = new QNetworkAccessCacheBackend(); 35 priv->backend->manager = this->d_func(); 36 priv->backend->setParent(reply); 37 priv->backend->reply = priv; 38 priv->setup(op, req, outgoingData); 39 return reply; 40 } 41 42 #ifndef QT_NO_BEARERMANAGEMENT 43 // Return a disabled network reply if network access is disabled. 44 // Except if the scheme is empty or file://. 45 if (!d->networkAccessible && !isLocalFile) { 46 return new QDisabledNetworkReply(this, req, op); 47 } 48 49 if (!d->networkSessionStrongRef && (d->initializeSession || !d->networkConfiguration.isEmpty())) { 50 QNetworkConfigurationManager manager; 51 if (!d->networkConfiguration.isEmpty()) { 52 d->createSession(manager.configurationFromIdentifier(d->networkConfiguration)); 53 } else { 54 if (manager.capabilities() & QNetworkConfigurationManager::NetworkSessionRequired) 55 d->createSession(manager.defaultConfiguration()); 56 else 57 d->initializeSession = false; 58 } 59 } 60 #endif 61 62 QNetworkRequest request = req; 63 if (!request.header(QNetworkRequest::ContentLengthHeader).isValid() && 64 outgoingData && !outgoingData->isSequential()) { 65 // request has no Content-Length 66 // but the data that is outgoing is random-access 67 request.setHeader(QNetworkRequest::ContentLengthHeader, outgoingData->size()); 68 } 69 70 if (static_cast<QNetworkRequest::LoadControl> 71 (request.attribute(QNetworkRequest::CookieLoadControlAttribute, 72 QNetworkRequest::Automatic).toInt()) == QNetworkRequest::Automatic) { 73 if (d->cookieJar) { 74 QList<QNetworkCookie> cookies = d->cookieJar->cookiesForUrl(request.url()); 75 if (!cookies.isEmpty()) 76 request.setHeader(QNetworkRequest::CookieHeader, QVariant::fromValue(cookies)); 77 } 78 } 79 80 // first step: create the reply 81 QUrl url = request.url(); 82 QNetworkReplyImpl *reply = new QNetworkReplyImpl(this); 83 #ifndef QT_NO_BEARERMANAGEMENT 84 if (!isLocalFile) { 85 connect(this, SIGNAL(networkSessionConnected()), 86 reply, SLOT(_q_networkSessionConnected())); 87 } 88 #endif 89 QNetworkReplyImplPrivate *priv = reply->d_func(); 90 priv->manager = this; 91 92 // second step: fetch cached credentials 93 // This is not done for the time being, we should use signal emissions to request 94 // the credentials from cache. 95 96 // third step: find a backend 97 priv->backend = d->findBackend(op, request); 98 99 if (priv->backend) { 100 priv->backend->setParent(reply); 101 priv->backend->reply = priv; 102 } 103 104 #ifndef QT_NO_OPENSSL 105 reply->setSslConfiguration(request.sslConfiguration()); 106 #endif 107 108 // fourth step: setup the reply 109 priv->setup(op, request, outgoingData); 110 111 return reply; 112 }
代码比较长，主要做了这些事情：
1、设定HTTP请求的头信息（例如客户端请求内容的长度、Cookie等）
2、生成并初始化Reply对象（实际是QNetworkReplyImpl对象）
3、获取本地缓存的认证信息（如果有的话）
4、设定Reply
5、获取一个backend实体
6、如果支持OPENSSL的话，设定SSL的配置
暂时先放一边后面再对createRequest()做进一步的分析，再来看postProcess()
1 QNetworkReply *QNetworkAccessManagerPrivate::postProcess(QNetworkReply *reply) 2 { 3 Q_Q(QNetworkAccessManager); 4 QNetworkReplyPrivate::setManager(reply, q); 5 q->connect(reply, SIGNAL(finished()), SLOT(_q_replyFinished())); 6 #ifndef QT_NO_OPENSSL 7 /* In case we're compiled without SSL support, we don't have this signal and we need to 8 * avoid getting a connection error. */ 9 q->connect(reply, SIGNAL(sslErrors(QList<QSslError>)), SLOT(_q_replySslErrors(QList<QSslError>))); 10 #endif 11 #ifndef QT_NO_BEARERMANAGEMENT 12 activeReplyCount++; 13 #endif 14 15 return reply; 16 }
简单来说就做了一件事情，把QNetworkReply的信号（finished、sslErrors）与QNetworkAccessManager的槽连接起来
接上面，进一步分析QNetworkAccessManager::createRequest()的实现。去除不重要的分支末节，看其调用的QNetworkReplyImplPrivate::setup()和QNetworkAccessManagerPrivate::findBackend()的代码
1 void QNetworkReplyImplPrivate::setup(QNetworkAccessManager::Operation op, const QNetworkRequest &req, 2 QIODevice *data) 3 { 4 Q_Q(QNetworkReplyImpl); 5 6 outgoingData = data; //outgoingData实际就是QNetworkRequest对象 7 request = req; 8 url = request.url(); 9 operation = op; 10 11 q->QIODevice::open(QIODevice::ReadOnly); 12 // Internal code that does a HTTP reply for the synchronous Ajax 13 // in QtWebKit. 14 QVariant synchronousHttpAttribute = req.attribute( 15 static_cast<QNetworkRequest::Attribute>(QNetworkRequest::SynchronousRequestAttribute)); 16 // The synchronous HTTP is a corner case, we will put all upload data in one big QByteArray in the outgoingDataBuffer. 17 // Yes, this is not the most efficient thing to do, but on the other hand synchronous XHR needs to die anyway. 18 if (synchronousHttpAttribute.toBool() && outgoingData) { 19 outgoingDataBuffer = QSharedPointer<QRingBuffer>(new QRingBuffer()); 20 qint64 previousDataSize = 0; 21 do { 22 previousDataSize = outgoingDataBuffer->size(); 23 outgoingDataBuffer->append(outgoingData->readAll()); 24 } while (outgoingDataBuffer->size() != previousDataSize); 25 } 26 27 if (backend) 28 backend->setSynchronous(synchronousHttpAttribute.toBool()); 29 30 31 if (outgoingData && backend && !backend->isSynchronous()) { 32 // there is data to be uploaded, e.g. HTTP POST. 33 34 if (!backend->needsResetableUploadData() || !outgoingData->isSequential()) { 35 // backend does not need upload buffering or 36 // fixed size non-sequential 37 // just start the operation 38 QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection); 39 } else { 40 bool bufferingDisallowed = 41 req.attribute(QNetworkRequest::DoNotBufferUploadDataAttribute, 42 false).toBool(); 43 44 if (bufferingDisallowed) { 45 // if a valid content-length header for the request was supplied, we can disable buffering 46 // if not, we will buffer anyway 47 if (req.header(QNetworkRequest::ContentLengthHeader).isValid()) { 48 QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection); 49 } else { 50 state = Buffering; 51 QMetaObject::invokeMethod(q, "_q_bufferOutgoingData", Qt::QueuedConnection); 52 } 53 } else { 54 // _q_startOperation will be called when the buffering has finished. 55 state = Buffering; 56 QMetaObject::invokeMethod(q, "_q_bufferOutgoingData", Qt::QueuedConnection); 57 } 58 } 59 } else { 60 // for HTTP, we want to send out the request as fast as possible to the network, without 61 // invoking methods in a QueuedConnection 62 #ifndef QT_NO_HTTP 63 if (qobject_cast<QNetworkAccessHttpBackend *>(backend) || (backend && backend->isSynchronous())) { 64 _q_startOperation(); 65 } else { 66 QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection); 67 } 68 #else 69 if (backend && backend->isSynchronous()) 70 _q_startOperation(); 71 else 72 QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection); 73 #endif // QT_NO_HTTP 74 } 75 }
发现调用_q_startOperation函数和_q_bufferOutgoingData函数，代码如下
1 void QNetworkReplyImplPrivate::_q_startOperation() 2 { 3 // ensure this function is only being called once 4 if (state == Working || state == Finished) { 5 qDebug("QNetworkReplyImpl::_q_startOperation was called more than once"); 6 return; 7 } 8 state = Working; 9 10 // note: if that method is called directly, it cannot happen that the backend is 0, 11 // because we just checked via a qobject_cast that we got a http backend (see 12 // QNetworkReplyImplPrivate::setup()) 13 if (!backend) { 14 error(QNetworkReplyImpl::ProtocolUnknownError, 15 QCoreApplication::translate("QNetworkReply", "Protocol \"%1\" is unknown").arg(url.scheme())); // not really true!; 16 finished(); 17 return; 18 } 19 20 if (!backend->start()) { 21 #ifndef QT_NO_BEARERMANAGEMENT 22 // backend failed to start because the session state is not Connected. 23 // QNetworkAccessManager will call _q_startOperation again for us when the session 24 // state changes. 25 state = WaitingForSession; 26 27 QSharedPointer<QNetworkSession> session(manager->d_func()->getNetworkSession()); 28 29 if (session) { 30 Q_Q(QNetworkReplyImpl); 31 32 QObject::connect(session.data(), SIGNAL(error(QNetworkSession::SessionError)), 33 q, SLOT(_q_networkSessionFailed()), Qt::QueuedConnection); 34 35 if (!session->isOpen()) 36 session->open(); 37 } else { 38 qWarning("Backend is waiting for QNetworkSession to connect, but there is none!"); 39 state = Working; 40 error(QNetworkReplyImpl::UnknownNetworkError, 41 QCoreApplication::translate("QNetworkReply", "Network session error.")); 42 finished(); 43 } 44 #else 45 qWarning("Backend start failed"); 46 state = Working; 47 error(QNetworkReplyImpl::UnknownNetworkError, 48 QCoreApplication::translate("QNetworkReply", "backend start error.")); 49 finished(); 50 #endif 51 return; 52 } 53 54 if (backend && backend->isSynchronous()) { 55 state = Finished; 56 q_func()->setFinished(true); 57 } else { 58 if (state != Finished) { 59 if (operation == QNetworkAccessManager::GetOperation) 60 pendingNotifications.append(NotifyDownstreamReadyWrite); 61 62 handleNotifications(); 63 } 64 } 65 }
1 void QNetworkReplyImplPrivate::_q_bufferOutgoingData() 2 { 3 Q_Q(QNetworkReplyImpl); 4 5 if (!outgoingDataBuffer) { 6 // first call, create our buffer 7 outgoingDataBuffer = QSharedPointer<QRingBuffer>(new QRingBuffer()); 8 9 QObject::connect(outgoingData, SIGNAL(readyRead()), q, SLOT(_q_bufferOutgoingData())); 10 QObject::connect(outgoingData, SIGNAL(readChannelFinished()), q, SLOT(_q_bufferOutgoingDataFinished())); 11 } 12 13 qint64 bytesBuffered = 0; 14 qint64 bytesToBuffer = 0; 15 16 // read data into our buffer 17 forever { 18 bytesToBuffer = outgoingData->bytesAvailable(); 19 // unknown? just try 2 kB, this also ensures we always try to read the EOF 20 if (bytesToBuffer <= 0) 21 bytesToBuffer = 2*1024; 22 23 char *dst = outgoingDataBuffer->reserve(bytesToBuffer); 24 bytesBuffered = outgoingData->read(dst, bytesToBuffer); 25 26 if (bytesBuffered == -1) { 27 // EOF has been reached. 28 outgoingDataBuffer->chop(bytesToBuffer); 29 30 _q_bufferOutgoingDataFinished(); 31 break; 32 } else if (bytesBuffered == 0) { 33 // nothing read right now, just wait until we get called again 34 outgoingDataBuffer->chop(bytesToBuffer); 35 36 break; 37 } else { 38 // don't break, try to read() again 39 outgoingDataBuffer->chop(bytesToBuffer - bytesBuffered); 40 } 41 } 42 }
连接两个信号与槽之后，是打开QIODevice，暂未深入分析。然后是呼叫q->_q_startOperation()，实际就是调用QNetworkReplyImpl::_q_startOperation()，使用的是队列等待方式（也就是发送一个消息进入系统消息队列，这个setup函数以及全部后续执行完毕，主动权交回给Windows后，再根据进入队列的消息来触发）。
_q_startOperation就是做了一些简单的判断，然后调用 handleNotifications
1 void QNetworkReplyImplPrivate::handleNotifications() 2 { 3 if (notificationHandlingPaused) 4 return; 5 6 NotificationQueue current = pendingNotifications; 7 pendingNotifications.clear(); 8 9 if (state != Working) 10 return; 11 12 while (state == Working && !current.isEmpty()) { 13 InternalNotifications notification = current.dequeue(); 14 switch (notification) { 15 case NotifyDownstreamReadyWrite: 16 if (copyDevice) 17 _q_copyReadyRead(); 18 else 19 backend->downstreamReadyWrite(); 20 break; 21 22 case NotifyCloseDownstreamChannel: 23 backend->closeDownstreamChannel(); 24 break; 25 26 case NotifyCopyFinished: { 27 QIODevice *dev = copyDevice; 28 copyDevice = 0; 29 backend->copyFinished(dev); 30 break; 31 } 32 } 33 } 34 }
该函数主要用于处理各种socket相关事件
因此我们先看QNetworkAccessManagerPrivate::findBackend()的代码实现
1 QNetworkAccessBackend *QNetworkAccessManagerPrivate::findBackend(QNetworkAccessManager::Operation op, 2 const QNetworkRequest &request) 3 { 4 if (QNetworkAccessBackendFactoryData::valid) { 5 QMutexLocker locker(&factoryData()->mutex); 6 QNetworkAccessBackendFactoryData::ConstIterator it = factoryData()->constBegin(), 7 end = factoryData()->constEnd(); 8 while (it != end) { 9 QNetworkAccessBackend *backend = (*it)->create(op, request); 10 if (backend) { 11 backend->manager = this; 12 return backend; // found a factory that handled our request 13 } 14 ++it; 15 } 16 } 17 return 0; 18 }
这段代码有一点复杂，先看红色标记的第一句，factoryData()是用宏来定义的函数：
1 Q_GLOBAL_STATIC(QNetworkAccessBackendFactoryData, factoryData)
宏定义如下：
1 #define Q_GLOBAL_STATIC(TYPE, NAME) \ 2 static TYPE *NAME() \ 3 { \ 4 static TYPE thisVariable; \ 5 static QGlobalStatic<TYPE > thisGlobalStatic(&thisVariable); \ 6 return thisGlobalStatic.pointer; \ 7 }
如果对STD比较熟悉，第一感觉这是一个模板List操作。在这里constBegin()和constEnd()组合起来是一个遍历，那么在什么地方设定值呢？良好代码的命名是很规范的，我试了试全局查找factoryData()，找到了我所希望看到的东西：
1 QNetworkAccessBackendFactory::QNetworkAccessBackendFactory() 2 { 3 QMutexLocker locker(&factoryData()->mutex); 4 factoryData()->append(this); 5 } 6 7 QNetworkAccessBackendFactory::~QNetworkAccessBackendFactory() 8 { 9 if (QNetworkAccessBackendFactoryData::valid) { 10 QMutexLocker locker(&factoryData()->mutex); 11 factoryData()->removeAll(this); 12 } 13 }
里prepend()应该是把对象添加到列表；而removeAll()就是清空全部数据了。
factoryData()里面包含的对象序列，应该是从QNetworkAccessBackendFactory衍生出来的。
一共有哪些子类呢？继续全局查找
1 class QNetworkAccessDataBackendFactory: public QNetworkAccessBackendFactory 2 class QNetworkAccessDebugPipeBackendFactory: public QNetworkAccessBackendFactory 3 class QNetworkAccessFileBackendFactory: public QNetworkAccessBackendFactory 4 class QNetworkAccessFtpBackendFactory: public QNetworkAccessBackendFactory 5 class QNetworkAccessHttpBackendFactory : public QNetworkAccessBackendFactory
去除暂时不关心的DebugPipe，一共有四种：DataBackend、FileBackend、FtpBackend、HttpBackend。媒体的种类原来是在这里实现的。看其中QNetworkAccessHttpBackendFactory::create()
1 QNetworkAccessBackend * 2 QNetworkAccessHttpBackendFactory::create(QNetworkAccessManager::Operation op, 3 const QNetworkRequest &request) const 4 { 5 // check the operation 6 switch (op) { 7 case QNetworkAccessManager::GetOperation: 8 case QNetworkAccessManager::PostOperation: 9 case QNetworkAccessManager::HeadOperation: 10 case QNetworkAccessManager::PutOperation: 11 case QNetworkAccessManager::DeleteOperation: 12 case QNetworkAccessManager::CustomOperation: 13 break; 14 15 default: 16 // no, we can't handle this request 17 return 0; 18 } 19 20 QUrl url = request.url(); 21 QString scheme = url.scheme().toLower(); 22 if (scheme == QLatin1String("http") || scheme == QLatin1String("https")) 23 return new QNetworkAccessHttpBackend; 24 25 return 0; 26 }
如果是能够处理的OP标记并且URL的前缀是http或者是https，则创建一个QNetworkAccessHttpBackend对象。
前面QNetworkAccessManager::get()代码中，调用的参数是QNetworkAccessManager::GetOperation，所以在我们分析的这个应用中，创建的是QNetworkAccessHttpBackend对象。
findBackend()到此分析完毕；由于factoryData()的具体实现跟我们分析网络通信的目标没有太大关系，未深入分析，有谁分析了的话请转告一声，值得一看。
回到前面暂停的QNetworkReplyImpl::_q_startOperation()，又实现了什么动作呢？
首先调用了刚刚创建的QNetworkAccessHttpBackend::start()，然后是添加通知消息、调用_q_sourceReadyRead()、最后处理通知消息
1 bool QNetworkAccessBackend::start() 2 { 3 #ifndef QT_NO_BEARERMANAGEMENT 4 // For bearer, check if session start is required 5 QSharedPointer<QNetworkSession> networkSession(manager->getNetworkSession()); 6 if (networkSession) { 7 // session required 8 if (networkSession->isOpen() && 9 networkSession->state() == QNetworkSession::Connected) { 10 // Session is already open and ready to use. 11 // copy network session down to the backend 12 setProperty("_q_networksession", QVariant::fromValue(networkSession)); 13 } else { 14 // Session not ready, but can skip for loopback connections 15 16 // This is not ideal. 17 const QString host = reply->url.host(); 18 19 if (host == QLatin1String("localhost") || 20 QHostAddress(host) == QHostAddress::LocalHost || 21 QHostAddress(host) == QHostAddress::LocalHostIPv6) { 22 // Don't need an open session for localhost access. 23 } else { 24 // need to wait for session to be opened 25 return false; 26 } 27 } 28 } 29 #endif 30 31 #ifndef QT_NO_NETWORKPROXY 32 #ifndef QT_NO_BEARERMANAGEMENT 33 // Get the proxy settings from the network session (in the case of service networks, 34 // the proxy settings change depending which AP was activated) 35 QNetworkSession *session = networkSession.data(); 36 QNetworkConfiguration config; 37 if (session) { 38 QNetworkConfigurationManager configManager; 39 // The active configuration tells us what IAP is in use 40 QVariant v = session->sessionProperty(QLatin1String("ActiveConfiguration")); 41 if (v.isValid()) 42 config = configManager.configurationFromIdentifier(qvariant_cast<QString>(v)); 43 // Fallback to using the configuration if no active configuration 44 if (!config.isValid()) 45 config = session->configuration(); 46 // or unspecified configuration if that is no good either 47 if (!config.isValid()) 48 config = QNetworkConfiguration(); 49 } 50 reply->proxyList = manager->queryProxy(QNetworkProxyQuery(config, url())); 51 #else // QT_NO_BEARERMANAGEMENT 52 // Without bearer management, the proxy depends only on the url 53 reply->proxyList = manager->queryProxy(QNetworkProxyQuery(url())); 54 #endif 55 #endif 56 57 // now start the request 58 open(); 59 return true; 60 }
start函数很简单，主要是打开QNetworkAccessBackend
话说昨日走到QNetworkReplyImplPrivate::_q_startOperation()，勾引出QNetworkAccessHttpBackend::open()，今日接着欣赏QT之美丽
1 void QNetworkAccessHttpBackend::open() 2 { 3 postRequest(); 4 }
open函数仅仅是调用postRequest()
1 etworkAccessHttpBackend::postRequest() 2 { 3 QThread *thread = 0; 4 if (isSynchronous()) { 5 // A synchronous HTTP request uses its own thread 6 thread = new QThread(); 7 QObject::connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater())); 8 thread->start(); 9 } else if (!manager->httpThread) { 10 // We use the manager-global thread. 11 // At some point we could switch to having multiple threads if it makes sense. 12 manager->httpThread = new QThread(); 13 QObject::connect(manager->httpThread, SIGNAL(finished()), manager->httpThread, SLOT(deleteLater())); 14 manager->httpThread->start(); 15 #ifndef QT_NO_NETWORKPROXY 16 qRegisterMetaType<QNetworkProxy>("QNetworkProxy"); 17 #endif 18 #ifndef QT_NO_OPENSSL 19 qRegisterMetaType<QList<QSslError> >("QList<QSslError>"); 20 qRegisterMetaType<QSslConfiguration>("QSslConfiguration"); 21 #endif 22 qRegisterMetaType<QList<QPair<QByteArray,QByteArray> > >("QList<QPair<QByteArray,QByteArray> >"); 23 qRegisterMetaType<QHttpNetworkRequest>("QHttpNetworkRequest"); 24 qRegisterMetaType<QNetworkReply::NetworkError>("QNetworkReply::NetworkError"); 25 qRegisterMetaType<QSharedPointer<char> >("QSharedPointer<char>"); 26 27 thread = manager->httpThread; 28 } else { 29 // Asynchronous request, thread already exists 30 thread = manager->httpThread; 31 } 32 33 QUrl url = request().url(); 34 httpRequest.setUrl(url); 35 36 bool ssl = url.scheme().toLower() == QLatin1String("https"); 37 setAttribute(QNetworkRequest::ConnectionEncryptedAttribute, ssl); 38 httpRequest.setSsl(ssl); 39 40 41 #ifndef QT_NO_NETWORKPROXY 42 QNetworkProxy transparentProxy, cacheProxy; 43 44 foreach (const QNetworkProxy &p, proxyList()) { 45 // use the first proxy that works 46 // for non-encrypted connections, any transparent or HTTP proxy 47 // for encrypted, only transparent proxies 48 if (!ssl 49 && (p.capabilities() & QNetworkProxy::CachingCapability) 50 && (p.type() == QNetworkProxy::HttpProxy || 51 p.type() == QNetworkProxy::HttpCachingProxy)) { 52 cacheProxy = p; 53 transparentProxy = QNetworkProxy::NoProxy; 54 break; 55 } 56 if (p.isTransparentProxy()) { 57 transparentProxy = p; 58 cacheProxy = QNetworkProxy::NoProxy; 59 break; 60 } 61 } 62 63 // check if at least one of the proxies 64 if (transparentProxy.type() == QNetworkProxy::DefaultProxy && 65 cacheProxy.type() == QNetworkProxy::DefaultProxy) { 66 // unsuitable proxies 67 QMetaObject::invokeMethod(this, "error", isSynchronous() ? Qt::DirectConnection : Qt::QueuedConnection, 68 Q_ARG(QNetworkReply::NetworkError, QNetworkReply::ProxyNotFoundError), 69 Q_ARG(QString, tr("No suitable proxy found"))); 70 QMetaObject::invokeMethod(this, "finished", isSynchronous() ? Qt::DirectConnection : Qt::QueuedConnection); 71 return; 72 } 73 #endif 74 75 76 bool loadedFromCache = false; 77 httpRequest.setPriority(convert(request().priority())); 78 79 switch (operation()) { 80 case QNetworkAccessManager::GetOperation: 81 httpRequest.setOperation(QHttpNetworkRequest::Get); 82 loadedFromCache = loadFromCacheIfAllowed(httpRequest); 83 break; 84 85 case QNetworkAccessManager::HeadOperation: 86 httpRequest.setOperation(QHttpNetworkRequest::Head); 87 loadedFromCache = loadFromCacheIfAllowed(httpRequest); 88 break; 89 90 case QNetworkAccessManager::PostOperation: 91 invalidateCache(); 92 httpRequest.setOperation(QHttpNetworkRequest::Post); 93 createUploadByteDevice(); 94 break; 95 96 case QNetworkAccessManager::PutOperation: 97 invalidateCache(); 98 httpRequest.setOperation(QHttpNetworkRequest::Put); 99 createUploadByteDevice(); 100 break; 101 102 case QNetworkAccessManager::DeleteOperation: 103 invalidateCache(); 104 httpRequest.setOperation(QHttpNetworkRequest::Delete); 105 break; 106 107 case QNetworkAccessManager::CustomOperation: 108 invalidateCache(); // for safety reasons, we don't know what the operation does 109 httpRequest.setOperation(QHttpNetworkRequest::Custom); 110 createUploadByteDevice(); 111 httpRequest.setCustomVerb(request().attribute( 112 QNetworkRequest::CustomVerbAttribute).toByteArray()); 113 break; 114 115 default: 116 break; // can't happen 117 } 118 119 if (loadedFromCache) { 120 // commented this out since it will be called later anyway 121 // by copyFinished() 122 //QNetworkAccessBackend::finished(); 123 return; // no need to send the request! :) 124 } 125 126 QList<QByteArray> headers = request().rawHeaderList(); 127 if (resumeOffset != 0) { 128 if (headers.contains("Range")) { 129 // Need to adjust resume offset for user specified range 130 131 headers.removeOne("Range"); 132 133 // We've already verified that requestRange starts with "bytes=", see canResume. 134 QByteArray requestRange = request().rawHeader("Range").mid(6); 135 136 int index = requestRange.indexOf('-'); 137 138 quint64 requestStartOffset = requestRange.left(index).toULongLong(); 139 quint64 requestEndOffset = requestRange.mid(index + 1).toULongLong(); 140 141 requestRange = "bytes=" + QByteArray::number(resumeOffset + requestStartOffset) + 142 '-' + QByteArray::number(requestEndOffset); 143 144 httpRequest.setHeaderField("Range", requestRange); 145 } else { 146 httpRequest.setHeaderField("Range", "bytes=" + QByteArray::number(resumeOffset) + '-'); 147 } 148 } 149 150 foreach (const QByteArray &header, headers) 151 httpRequest.setHeaderField(header, request().rawHeader(header)); 152 153 if (request().attribute(QNetworkRequest::HttpPipeliningAllowedAttribute).toBool() == true) 154 httpRequest.setPipeliningAllowed(true); 155 156 if (static_cast<QNetworkRequest::LoadControl> 157 (request().attribute(QNetworkRequest::AuthenticationReuseAttribute, 158 QNetworkRequest::Automatic).toInt()) == QNetworkRequest::Manual) 159 httpRequest.setWithCredentials(false); 160 161 162 // Create the HTTP thread delegate 163 QHttpThreadDelegate *delegate = new QHttpThreadDelegate; 164 #ifndef QT_NO_BEARERMANAGEMENT 165 QVariant v(property("_q_networksession")); 166 if (v.isValid()) 167 delegate->networkSession = qvariant_cast<QSharedPointer<QNetworkSession> >(v); 168 #endif 169 170 // For the synchronous HTTP, this is the normal way the delegate gets deleted 171 // For the asynchronous HTTP this is a safety measure, the delegate deletes itself when HTTP is finished 172 connect(thread, SIGNAL(finished()), delegate, SLOT(deleteLater())); 173 174 // Set the properties it needs 175 delegate->httpRequest = httpRequest; 176 #ifndef QT_NO_NETWORKPROXY 177 delegate->cacheProxy = cacheProxy; 178 delegate->transparentProxy = transparentProxy; 179 #endif 180 delegate->ssl = ssl; 181 #ifndef QT_NO_OPENSSL 182 if (ssl) 183 delegate->incomingSslConfiguration = request().sslConfiguration(); 184 #endif 185 186 // Do we use synchronous HTTP? 187 delegate->synchronous = isSynchronous(); 188 189 // The authentication manager is used to avoid the BlockingQueuedConnection communication 190 // from HTTP thread to user thread in some cases. 191 delegate->authenticationManager = manager->authenticationManager; 192 193 if (!isSynchronous()) { 194 // Tell our zerocopy policy to the delegate 195 delegate->downloadBufferMaximumSize = 196 request().attribute(QNetworkRequest::MaximumDownloadBufferSizeAttribute).toLongLong(); 197 198 // These atomic integers are used for signal compression 199 delegate->pendingDownloadData = pendingDownloadDataEmissions; 200 delegate->pendingDownloadProgress = pendingDownloadProgressEmissions; 201 202 // Connect the signals of the delegate to us 203 connect(delegate, SIGNAL(downloadData(QByteArray)), 204 this, SLOT(replyDownloadData(QByteArray)), 205 Qt::QueuedConnection); 206 connect(delegate, SIGNAL(downloadFinished()), 207 this, SLOT(replyFinished()), 208 Qt::QueuedConnection); 209 connect(delegate, SIGNAL(downloadMetaData(QList<QPair<QByteArray,QByteArray> >,int,QString,bool,QSharedPointer<char>,qint64)), 210 this, SLOT(replyDownloadMetaData(QList<QPair<QByteArray,QByteArray> >,int,QString,bool,QSharedPointer<char>,qint64)), 211 Qt::QueuedConnection); 212 connect(delegate, SIGNAL(downloadProgress(qint64,qint64)), 213 this, SLOT(replyDownloadProgressSlot(qint64,qint64)), 214 Qt::QueuedConnection); 215 connect(delegate, SIGNAL(error(QNetworkReply::NetworkError,QString)), 216 this, SLOT(httpError(QNetworkReply::NetworkError, const QString)), 217 Qt::QueuedConnection); 218 #ifndef QT_NO_OPENSSL 219 connect(delegate, SIGNAL(sslConfigurationChanged(QSslConfiguration)), 220 this, SLOT(replySslConfigurationChanged(QSslConfiguration)), 221 Qt::QueuedConnection); 222 #endif 223 // Those need to report back, therefire BlockingQueuedConnection 224 connect(delegate, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)), 225 this, SLOT(httpAuthenticationRequired(QHttpNetworkRequest,QAuthenticator*)), 226 Qt::BlockingQueuedConnection); 227 #ifndef QT_NO_NETWORKPROXY 228 connect (delegate, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)), 229 this, SLOT(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)), 230 Qt::BlockingQueuedConnection); 231 #endif 232 #ifndef QT_NO_OPENSSL 233 connect(delegate, SIGNAL(sslErrors(QList<QSslError>,bool*,QList<QSslError>*)), 234 this, SLOT(replySslErrors(const QList<QSslError> &, bool *, QList<QSslError> *)), 235 Qt::BlockingQueuedConnection); 236 #endif 237 // This signal we will use to start the request. 238 connect(this, SIGNAL(startHttpRequest()), delegate, SLOT(startRequest())); 239 connect(this, SIGNAL(abortHttpRequest()), delegate, SLOT(abortRequest())); 240 241 // To throttle the connection. 242 QObject::connect(this, SIGNAL(readBufferSizeChanged(qint64)), delegate, SLOT(readBufferSizeChanged(qint64))); 243 QObject::connect(this, SIGNAL(readBufferFreed(qint64)), delegate, SLOT(readBufferFreed(qint64))); 244 245 if (uploadByteDevice) { 246 QNonContiguousByteDeviceThreadForwardImpl *forwardUploadDevice = 247 new QNonContiguousByteDeviceThreadForwardImpl(uploadByteDevice->atEnd(), uploadByteDevice->size()); 248 if (uploadByteDevice->isResetDisabled()) 249 forwardUploadDevice->disableReset(); 250 forwardUploadDevice->setParent(delegate); // needed to make sure it is moved on moveToThread() 251 delegate->httpRequest.setUploadByteDevice(forwardUploadDevice); 252 253 // From main thread to user thread: 254 QObject::connect(this, SIGNAL(haveUploadData(QByteArray, bool, qint64)), 255 forwardUploadDevice, SLOT(haveDataSlot(QByteArray, bool, qint64)), Qt::QueuedConnection); 256 QObject::connect(uploadByteDevice.data(), SIGNAL(readyRead()), 257 forwardUploadDevice, SIGNAL(readyRead()), 258 Qt::QueuedConnection); 259 260 // From http thread to user thread: 261 QObject::connect(forwardUploadDevice, SIGNAL(wantData(qint64)), 262 this, SLOT(wantUploadDataSlot(qint64))); 263 QObject::connect(forwardUploadDevice, SIGNAL(processedData(qint64)), 264 this, SLOT(sentUploadDataSlot(qint64))); 265 connect(forwardUploadDevice, SIGNAL(resetData(bool*)), 266 this, SLOT(resetUploadDataSlot(bool*)), 267 Qt::BlockingQueuedConnection); // this is the only one with BlockingQueued! 268 } 269 } else if (isSynchronous()) { 270 connect(this, SIGNAL(startHttpRequestSynchronously()), delegate, SLOT(startRequestSynchronously()), Qt::BlockingQueuedConnection); 271 272 if (uploadByteDevice) { 273 // For the synchronous HTTP use case the use thread (this one here) is blocked 274 // so we cannot use the asynchronous upload architecture. 275 // We therefore won't use the QNonContiguousByteDeviceThreadForwardImpl but directly 276 // use the uploadByteDevice provided to us by the QNetworkReplyImpl. 277 // The code that is in QNetworkReplyImplPrivate::setup() makes sure it is safe to use from a thread 278 // since it only wraps a QRingBuffer 279 delegate->httpRequest.setUploadByteDevice(uploadByteDevice.data()); 280 } 281 } 282 283 284 // Move the delegate to the http thread 285 delegate->moveToThread(thread); 286 // This call automatically moves the uploadDevice too for the asynchronous case. 287 288 // Send an signal to the delegate so it starts working in the other thread 289 if (isSynchronous()) { 290 emit startHttpRequestSynchronously(); // This one is BlockingQueuedConnection, so it will return when all work is done 291 292 if (delegate->incomingErrorCode != QNetworkReply::NoError) { 293 replyDownloadMetaData 294 (delegate->incomingHeaders, 295 delegate->incomingStatusCode, 296 delegate->incomingReasonPhrase, 297 delegate->isPipeliningUsed, 298 QSharedPointer<char>(), 299 delegate->incomingContentLength); 300 replyDownloadData(delegate->synchronousDownloadData); 301 httpError(delegate->incomingErrorCode, delegate->incomingErrorDetail); 302 } else { 303 replyDownloadMetaData 304 (delegate->incomingHeaders, 305 delegate->incomingStatusCode, 306 delegate->incomingReasonPhrase, 307 delegate->isPipeliningUsed, 308 QSharedPointer<char>(), 309 delegate->incomingContentLength); 310 replyDownloadData(delegate->synchronousDownloadData); 311 } 312 313 // End the thread. It will delete itself from the finished() signal 314 thread->quit(); 315 thread->wait(5000); 316 317 finished(); 318 } else { 319 emit startHttpRequest(); // Signal to the HTTP thread and go back to user. 320 } 321 }
主要是链接槽函数，看槽函数代码startRequest
1 void QHttpThreadDelegate::startRequest() 2 { 3 #ifdef QHTTPTHREADDELEGATE_DEBUG 4 qDebug() << "QHttpThreadDelegate::startRequest() thread=" << QThread::currentThreadId(); 5 #endif 6 // Check QThreadStorage for the QNetworkAccessCache 7 // If not there, create this connection cache 8 if (!connections.hasLocalData()) { 9 connections.setLocalData(new QNetworkAccessCache()); 10 } 11 12 // check if we have an open connection to this host 13 QUrl urlCopy = httpRequest.url(); 14 urlCopy.setPort(urlCopy.port(ssl ? 443 : 80)); 15 16 #ifndef QT_NO_NETWORKPROXY 17 if (transparentProxy.type() != QNetworkProxy::NoProxy) 18 cacheKey = makeCacheKey(urlCopy, &transparentProxy); 19 else if (cacheProxy.type() != QNetworkProxy::NoProxy) 20 cacheKey = makeCacheKey(urlCopy, &cacheProxy); 21 else 22 #endif 23 cacheKey = makeCacheKey(urlCopy, 0); 24 25 26 // the http object is actually a QHttpNetworkConnection 27 httpConnection = static_cast<QNetworkAccessCachedHttpConnection *>(connections.localData()->requestEntryNow(cacheKey)); 28 if (httpConnection == 0) { 29 // no entry in cache; create an object 30 // the http object is actually a QHttpNetworkConnection 31 #ifdef QT_NO_BEARERMANAGEMENT 32 httpConnection = new QNetworkAccessCachedHttpConnection(urlCopy.host(), urlCopy.port(), ssl); 33 #else 34 httpConnection = new QNetworkAccessCachedHttpConnection(urlCopy.host(), urlCopy.port(), ssl, networkSession); 35 #endif 36 #ifndef QT_NO_OPENSSL 37 // Set the QSslConfiguration from this QNetworkRequest. 38 if (ssl && incomingSslConfiguration != QSslConfiguration::defaultConfiguration()) { 39 httpConnection->setSslConfiguration(incomingSslConfiguration); 40 } 41 #endif 42 43 #ifndef QT_NO_NETWORKPROXY 44 httpConnection->setTransparentProxy(transparentProxy); 45 httpConnection->setCacheProxy(cacheProxy); 46 #endif 47 48 // cache the QHttpNetworkConnection corresponding to this cache key 49 connections.localData()->addEntry(cacheKey, httpConnection); 50 } 51 52 53 // Send the request to the connection 54 httpReply = httpConnection->sendRequest(httpRequest); 55 httpReply->setParent(this); 56 57 // Connect the reply signals that we need to handle and then forward 58 if (synchronous) { 59 connect(httpReply,SIGNAL(headerChanged()), this, SLOT(synchronousHeaderChangedSlot())); 60 connect(httpReply,SIGNAL(finished()), this, SLOT(synchronousFinishedSlot())); 61 connect(httpReply,SIGNAL(finishedWithError(QNetworkReply::NetworkError, const QString)), 62 this, SLOT(synchronousFinishedWithErrorSlot(QNetworkReply::NetworkError,QString))); 63 64 connect(httpReply, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)), 65 this, SLOT(synchronousAuthenticationRequiredSlot(QHttpNetworkRequest,QAuthenticator*))); 66 connect(httpReply, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)), 67 this, SLOT(synchronousProxyAuthenticationRequiredSlot(QNetworkProxy,QAuthenticator*))); 68 69 // Don't care about ignored SSL errors for now in the synchronous HTTP case. 70 } else if (!synchronous) { 71 connect(httpReply,SIGNAL(headerChanged()), this, SLOT(headerChangedSlot())); 72 connect(httpReply,SIGNAL(finished()), this, SLOT(finishedSlot())); 73 connect(httpReply,SIGNAL(finishedWithError(QNetworkReply::NetworkError, const QString)), 74 this, SLOT(finishedWithErrorSlot(QNetworkReply::NetworkError,QString))); 75 // some signals are only interesting when normal asynchronous style is used 76 connect(httpReply,SIGNAL(readyRead()), this, SLOT(readyReadSlot())); 77 connect(httpReply,SIGNAL(dataReadProgress(int, int)), this, SLOT(dataReadProgressSlot(int,int))); 78 #ifndef QT_NO_OPENSSL 79 connect(httpReply,SIGNAL(sslErrors(const QList<QSslError>)), this, SLOT(sslErrorsSlot(QList<QSslError>))); 80 #endif 81 82 // In the asynchronous HTTP case we can just forward those signals 83 // Connect the reply signals that we can directly forward 84 connect(httpReply, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)), 85 this, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*))); 86 connect(httpReply, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)), 87 this, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*))); 88 } 89 90 connect(httpReply, SIGNAL(cacheCredentials(QHttpNetworkRequest,QAuthenticator*)), 91 this, SLOT(cacheCredentialsSlot(QHttpNetworkRequest,QAuthenticator*))); 92 }
先查缓冲，没用的话新建连接，然后调用其sendRequest
1 QHttpNetworkReply* QHttpNetworkConnection::sendRequest(const QHttpNetworkRequest &request) 2 { 3 Q_D(QHttpNetworkConnection); 4 return d->queueRequest(request); 5 }
sendRequest()调用queueRequest()函数
1 QHttpNetworkReply* QHttpNetworkConnectionPrivate::queueRequest(const QHttpNetworkRequest &request) 2 { 3 Q_Q(QHttpNetworkConnection); 4 5 // The reply component of the pair is created initially. 6 QHttpNetworkReply *reply = new QHttpNetworkReply(request.url()); 7 reply->setRequest(request); 8 reply->d_func()->connection = q; 9 reply->d_func()->connectionChannel = &channels[0]; // will have the correct one set later 10 HttpMessagePair pair = qMakePair(request, reply); 11 12 switch (request.priority()) { 13 case QHttpNetworkRequest::HighPriority: 14 highPriorityQueue.prepend(pair); 15 break; 16 case QHttpNetworkRequest::NormalPriority: 17 case QHttpNetworkRequest::LowPriority: 18 lowPriorityQueue.prepend(pair); 19 break; 20 } 21 22 // this used to be called via invokeMethod and a QueuedConnection 23 // It is the only place _q_startNextRequest is called directly without going 24 // through the event loop using a QueuedConnection. 25 // This is dangerous because of recursion that might occur when emitting 26 // signals as DirectConnection from this code path. Therefore all signal 27 // emissions that can come out from this code path need to 28 // be QueuedConnection. 29 // We are currently trying to fine-tune this. 30 _q_startNextRequest(); 31 32 33 return reply; 34 }
在这里整个消息处理（或者是初始化动作）完成之后，按消息序列调用_q_startNextRequest
循环多通道处理请求，类似于connect流程
1 void QHttpNetworkConnectionPrivate::_q_startNextRequest() 2 { 3 // If the QHttpNetworkConnection is currently paused then bail out immediately 4 if (state == PausedState) 5 return; 6 7 //resend the necessary ones. 8 for (int i = 0; i < channelCount; ++i) { 9 if (channels[i].resendCurrent && (channels[i].state != QHttpNetworkConnectionChannel::ClosingState)) { 10 channels[i].resendCurrent = false; 11 channels[i].state = QHttpNetworkConnectionChannel::IdleState; 12 13 // if this is not possible, error will be emitted and connection terminated 14 if (!channels[i].resetUploadData()) 15 continue; 16 channels[i].sendRequest(); 17 } 18 } 19 20 // dequeue new ones 21 22 // return fast if there is nothing to do 23 if (highPriorityQueue.isEmpty() && lowPriorityQueue.isEmpty()) 24 return; 25 // try to get a free AND connected socket 26 for (int i = 0; i < channelCount; ++i) { 27 if (!channels[i].reply && !channels[i].isSocketBusy() && channels[i].socket->state() == QAbstractSocket::ConnectedState) { 28 if (dequeueRequest(channels[i].socket)) 29 channels[i].sendRequest(); 30 } 31 } 32 33 // try to push more into all sockets 34 // ### FIXME we should move this to the beginning of the function 35 // as soon as QtWebkit is properly using the pipelining 36 // (e.g. not for XMLHttpRequest or the first page load) 37 // ### FIXME we should also divide the requests more even 38 // on the connected sockets 39 //tryToFillPipeline(socket); 40 // return fast if there is nothing to pipeline 41 if (highPriorityQueue.isEmpty() && lowPriorityQueue.isEmpty()) 42 return; 43 for (int i = 0; i < channelCount; i++) 44 if (channels[i].socket->state() == QAbstractSocket::ConnectedState) 45 fillPipeline(channels[i].socket); 46 47 // If there is not already any connected channels we need to connect a new one. 48 // We do not pair the channel with the request until we know if it is 49 // connected or not. This is to reuse connected channels before we connect new once. 50 int queuedRequest = highPriorityQueue.count() + lowPriorityQueue.count(); 51 for (int i = 0; i < channelCount; ++i) { 52 if (channels[i].socket->state() == QAbstractSocket::ConnectingState) 53 queuedRequest--; 54 if ( queuedRequest <=0 ) 55 break; 56 if (!channels[i].reply && !channels[i].isSocketBusy() && (channels[i].socket->state() == QAbstractSocket::UnconnectedState)) { 57 channels[i].ensureConnection(); 58 queuedRequest--; 59 } 60 } 61 }
接着调用看代码
1 bool QHttpNetworkConnectionPrivate::dequeueRequest(QAbstractSocket *socket) 2 { 3 Q_ASSERT(socket); 4 5 int i = indexOf(socket); 6 7 if (!highPriorityQueue.isEmpty()) { 8 // remove from queue before sendRequest! else we might pipeline the same request again 9 HttpMessagePair messagePair = highPriorityQueue.takeLast(); 10 if (!messagePair.second->d_func()->requestIsPrepared) 11 prepareRequest(messagePair); 12 channels[i].request = messagePair.first; 13 channels[i].reply = messagePair.second; 14 return true; 15 } 16 17 if (!lowPriorityQueue.isEmpty()) { 18 // remove from queue before sendRequest! else we might pipeline the same request again 19 HttpMessagePair messagePair = lowPriorityQueue.takeLast(); 20 if (!messagePair.second->d_func()->requestIsPrepared) 21 prepareRequest(messagePair); 22 channels[i].request = messagePair.first; 23 channels[i].reply = messagePair.second; 24 return true; 25 } 26 return false; 27 }
看看prepareReuest
1 void QHttpNetworkConnectionPrivate::prepareRequest(HttpMessagePair &messagePair) 2 { 3 QHttpNetworkRequest &request = messagePair.first; 4 QHttpNetworkReply *reply = messagePair.second; 5 6 // add missing fields for the request 7 QByteArray value; 8 // check if Content-Length is provided 9 QNonContiguousByteDevice* uploadByteDevice = request.uploadByteDevice(); 10 if (uploadByteDevice) { 11 if (request.contentLength() != -1 && uploadByteDevice->size() != -1) { 12 // both values known, take the smaller one. 13 request.setContentLength(qMin(uploadByteDevice->size(), request.contentLength())); 14 } else if (request.contentLength() == -1 && uploadByteDevice->size() != -1) { 15 // content length not supplied by user, but the upload device knows it 16 request.setContentLength(uploadByteDevice->size()); 17 } else if (request.contentLength() != -1 && uploadByteDevice->size() == -1) { 18 // everything OK, the user supplied us the contentLength 19 } else if (request.contentLength() == -1 && uploadByteDevice->size() == -1) { 20 qFatal("QHttpNetworkConnectionPrivate: Neither content-length nor upload device size were given"); 21 } 22 } 23 // set the Connection/Proxy-Connection: Keep-Alive headers 24 #ifndef QT_NO_NETWORKPROXY 25 if (networkProxy.type() == QNetworkProxy::HttpCachingProxy) { 26 value = request.headerField("proxy-connection"); 27 if (value.isEmpty()) 28 request.setHeaderField("Proxy-Connection", "Keep-Alive"); 29 } else { 30 #endif 31 value = request.headerField("connection"); 32 if (value.isEmpty()) 33 request.setHeaderField("Connection", "Keep-Alive"); 34 #ifndef QT_NO_NETWORKPROXY 35 } 36 #endif 37 38 // If the request had a accept-encoding set, we better not mess 39 // with it. If it was not set, we announce that we understand gzip 40 // and remember this fact in request.d->autoDecompress so that 41 // we can later decompress the HTTP reply if it has such an 42 // encoding. 43 value = request.headerField("accept-encoding"); 44 if (value.isEmpty()) { 45 #ifndef QT_NO_COMPRESS 46 request.setHeaderField("Accept-Encoding", "gzip"); 47 request.d->autoDecompress = true; 48 #else 49 // if zlib is not available set this to false always 50 request.d->autoDecompress = false; 51 #endif 52 } 53 54 // some websites mandate an accept-language header and fail 55 // if it is not sent. This is a problem with the website and 56 // not with us, but we work around this by setting 57 // one always. 58 value = request.headerField("accept-language"); 59 if (value.isEmpty()) { 60 QString systemLocale = QLocale::system().name().replace(QChar::fromAscii('_'),QChar::fromAscii('-')); 61 QString acceptLanguage; 62 if (systemLocale == QLatin1String("C")) 63 acceptLanguage = QString::fromAscii("en,*"); 64 else if (systemLocale.startsWith(QLatin1String("en-"))) 65 acceptLanguage = QString::fromAscii("%1,*").arg(systemLocale); 66 else 67 acceptLanguage = QString::fromAscii("%1,en,*").arg(systemLocale); 68 request.setHeaderField("Accept-Language", acceptLanguage.toAscii()); 69 } 70 71 // set the User Agent 72 value = request.headerField("user-agent"); 73 if (value.isEmpty()) 74 request.setHeaderField("User-Agent", "Mozilla/5.0"); 75 // set the host 76 value = request.headerField("host"); 77 if (value.isEmpty()) { 78 QHostAddress add; 79 QByteArray host; 80 if(add.setAddress(hostName)) { 81 if(add.protocol() == QAbstractSocket::IPv6Protocol) { 82 host = "[" + hostName.toAscii() + "]";//format the ipv6 in the standard way 83 } else { 84 host = QUrl::toAce(hostName); 85 } 86 } else { 87 host = QUrl::toAce(hostName); 88 } 89 90 int port = request.url().port(); 91 if (port != -1) { 92 host += ':'; 93 host += QByteArray::number(port); 94 } 95 96 request.setHeaderField("Host", host); 97 } 98 99 reply->d_func()->requestIsPrepared = true; 100 }
按优先级次序发送请求。prepareRequest()设定HTTP请求的Header信息；关键是sendRequest()
1 bool QHttpNetworkConnectionChannel::sendRequest() 2 { 3 if (!reply) { 4 // heh, how should that happen! 5 qWarning() << "QHttpNetworkConnectionChannel::sendRequest() called without QHttpNetworkReply"; 6 state = QHttpNetworkConnectionChannel::IdleState; 7 return false; 8 } 9 10 switch (state) { 11 case QHttpNetworkConnectionChannel::IdleState: { // write the header 12 if (!ensureConnection()) { 13 // wait for the connection (and encryption) to be done 14 // sendRequest will be called again from either 15 // _q_connected or _q_encrypted 16 return false; 17 } 18 written = 0; // excluding the header 19 bytesTotal = 0; 20 21 QHttpNetworkReplyPrivate *replyPrivate = reply->d_func(); 22 replyPrivate->clear(); 23 replyPrivate->connection = connection; 24 replyPrivate->connectionChannel = this; 25 replyPrivate->autoDecompress = request.d->autoDecompress; 26 replyPrivate->pipeliningUsed = false; 27 28 // if the url contains authentication parameters, use the new ones 29 // both channels will use the new authentication parameters 30 if (!request.url().userInfo().isEmpty() && request.withCredentials()) { 31 QUrl url = request.url(); 32 QAuthenticator &auth = authenticator; 33 if (url.userName() != auth.user() 34 || (!url.password().isEmpty() && url.password() != auth.password())) { 35 auth.setUser(url.userName()); 36 auth.setPassword(url.password()); 37 connection->d_func()->copyCredentials(connection->d_func()->indexOf(socket), &auth, false); 38 } 39 // clear the userinfo, since we use the same request for resending 40 // userinfo in url can conflict with the one in the authenticator 41 url.setUserInfo(QString()); 42 request.setUrl(url); 43 } 44 // Will only be false if QtWebKit is performing a cross-origin XMLHttpRequest 45 // and withCredentials has not been set to true. 46 if (request.withCredentials()) 47 connection->d_func()->createAuthorization(socket, request); 48 #ifndef QT_NO_NETWORKPROXY 49 QByteArray header = QHttpNetworkRequestPrivate::header(request, 50 (connection->d_func()->networkProxy.type() != QNetworkProxy::NoProxy)); 51 #else 52 QByteArray header = QHttpNetworkRequestPrivate::header(request, false); 53 #endif 54 socket->write(header); 55 // flushing is dangerous (QSslSocket calls transmit which might read or error) 56 // socket->flush(); 57 QNonContiguousByteDevice* uploadByteDevice = request.uploadByteDevice(); 58 if (uploadByteDevice) { 59 // connect the signals so this function gets called again 60 QObject::connect(uploadByteDevice, SIGNAL(readyRead()),this, SLOT(_q_uploadDataReadyRead())); 61 62 bytesTotal = request.contentLength(); 63 64 state = QHttpNetworkConnectionChannel::WritingState; // start writing data 65 sendRequest(); //recurse 66 } else { 67 state = QHttpNetworkConnectionChannel::WaitingState; // now wait for response 68 sendRequest(); //recurse 69 } 70 71 break; 72 } 73 case QHttpNetworkConnectionChannel::WritingState: 74 { 75 // write the data 76 QNonContiguousByteDevice* uploadByteDevice = request.uploadByteDevice(); 77 if (!uploadByteDevice || bytesTotal == written) { 78 if (uploadByteDevice) 79 emit reply->dataSendProgress(written, bytesTotal); 80 state = QHttpNetworkConnectionChannel::WaitingState; // now wait for response 81 sendRequest(); // recurse 82 break; 83 } 84 85 // only feed the QTcpSocket buffer when there is less than 32 kB in it 86 const qint64 socketBufferFill = 32*1024; 87 const qint64 socketWriteMaxSize = 16*1024; 88 89 90 #ifndef QT_NO_OPENSSL 91 QSslSocket *sslSocket = qobject_cast<QSslSocket*>(socket); 92 // if it is really an ssl socket, check more than just bytesToWrite() 93 while ((socket->bytesToWrite() + (sslSocket ? sslSocket->encryptedBytesToWrite() : 0)) 94 <= socketBufferFill && bytesTotal != written) 95 #else 96 while (socket->bytesToWrite() <= socketBufferFill 97 && bytesTotal != written) 98 #endif 99 { 100 // get pointer to upload data 101 qint64 currentReadSize = 0; 102 qint64 desiredReadSize = qMin(socketWriteMaxSize, bytesTotal - written); 103 const char *readPointer = uploadByteDevice->readPointer(desiredReadSize, currentReadSize); 104 105 if (currentReadSize == -1) { 106 // premature eof happened 107 connection->d_func()->emitReplyError(socket, reply, QNetworkReply::UnknownNetworkError); 108 return false; 109 break; 110 } else if (readPointer == 0 || currentReadSize == 0) { 111 // nothing to read currently, break the loop 112 break; 113 } else { 114 qint64 currentWriteSize = socket->write(readPointer, currentReadSize); 115 if (currentWriteSize == -1 || currentWriteSize != currentReadSize) { 116 // socket broke down 117 connection->d_func()->emitReplyError(socket, reply, QNetworkReply::UnknownNetworkError); 118 return false; 119 } else { 120 written += currentWriteSize; 121 uploadByteDevice->advanceReadPointer(currentWriteSize); 122 123 emit reply->dataSendProgress(written, bytesTotal); 124 125 if (written == bytesTotal) { 126 // make sure this function is called once again 127 state = QHttpNetworkConnectionChannel::WaitingState; 128 sendRequest(); 129 break; 130 } 131 } 132 } 133 } 134 break; 135 } 136 137 case QHttpNetworkConnectionChannel::WaitingState: 138 { 139 QNonContiguousByteDevice* uploadByteDevice = request.uploadByteDevice(); 140 if (uploadByteDevice) { 141 QObject::disconnect(uploadByteDevice, SIGNAL(readyRead()), this, SLOT(_q_uploadDataReadyRead())); 142 } 143 144 // HTTP pipelining 145 //connection->d_func()->fillPipeline(socket); 146 //socket->flush(); 147 148 // ensure we try to receive a reply in all cases, even if _q_readyRead_ hat not been called 149 // this is needed if the sends an reply before we have finished sending the request. In that 150 // case receiveReply had been called before but ignored the server reply 151 if (socket->bytesAvailable()) 152 QMetaObject::invokeMethod(this, "_q_receiveReply", Qt::QueuedConnection); 153 break; 154 } 155 case QHttpNetworkConnectionChannel::ReadingState: 156 // ignore _q_bytesWritten in these states 157 // fall through 158 default: 159 break; 160 } 161 return true; 162 }
进行的底层的socket调用，不详细分析
QHttpNetworkConnection的构造中，有些我们感兴趣的东西：
1 QHttpNetworkConnection::QHttpNetworkConnection(const QString &hostName, quint16 port, bool encrypt, QObject *parent, QSharedPointer<QNetworkSession> networkSession) 2 : QObject(*(new QHttpNetworkConnectionPrivate(hostName, port, encrypt)), parent) 3 { 4 Q_D(QHttpNetworkConnection); 5 d->networkSession = networkSession; 6 d->init(); 7 }
继续跟进 init函数：
1 void QHttpNetworkConnectionPrivate::init() 2 { 3 for (int i = 0; i < channelCount; i++) { 4 channels[i].setConnection(this->q_func()); 5 channels[i].ssl = encrypt; 6 #ifndef QT_NO_BEARERMANAGEMENT 7 //push session down to channels 8 channels[i].networkSession = networkSession; 9 #endif 10 channels[i].init(); 11 } 12 }
接下来看channels的init函数
1 void QHttpNetworkConnectionChannel::init() 2 { 3 #ifndef QT_NO_OPENSSL 4 if (connection->d_func()->encrypt) 5 socket = new QSslSocket; 6 else 7 socket = new QTcpSocket; 8 #else 9 socket = new QTcpSocket; 10 #endif 11 #ifndef QT_NO_BEARERMANAGEMENT 12 //push session down to socket 13 if (networkSession) 14 socket->setProperty("_q_networksession", QVariant::fromValue(networkSession)); 15 #endif 16 #ifndef QT_NO_NETWORKPROXY 17 // Set by QNAM anyway, but let's be safe here 18 socket->setProxy(QNetworkProxy::NoProxy); 19 #endif 20 21 QObject::connect(socket, SIGNAL(bytesWritten(qint64)), 22 this, SLOT(_q_bytesWritten(qint64)), 23 Qt::DirectConnection); 24 QObject::connect(socket, SIGNAL(connected()), 25 this, SLOT(_q_connected()), 26 Qt::DirectConnection); 27 QObject::connect(socket, SIGNAL(readyRead()), 28 this, SLOT(_q_readyRead()), 29 Qt::DirectConnection); 30 31 // The disconnected() and error() signals may already come 32 // while calling connectToHost(). 33 // In case of a cached hostname or an IP this 34 // will then emit a signal to the user of QNetworkReply 35 // but cannot be caught because the user did not have a chance yet 36 // to connect to QNetworkReply's signals. 37 qRegisterMetaType<QAbstractSocket::SocketError>("QAbstractSocket::SocketError"); 38 QObject::connect(socket, SIGNAL(disconnected()), 39 this, SLOT(_q_disconnected()), 40 Qt::QueuedConnection); 41 QObject::connect(socket, SIGNAL(error(QAbstractSocket::SocketError)), 42 this, SLOT(_q_error(QAbstractSocket::SocketError)), 43 Qt::QueuedConnection); 44 45 46 #ifndef QT_NO_NETWORKPROXY 47 QObject::connect(socket, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)), 48 this, SLOT(_q_proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)), 49 Qt::DirectConnection); 50 #endif 51 52 #ifndef QT_NO_OPENSSL 53 QSslSocket *sslSocket = qobject_cast<QSslSocket*>(socket); 54 if (sslSocket) { 55 // won't be a sslSocket if encrypt is false 56 QObject::connect(sslSocket, SIGNAL(encrypted()), 57 this, SLOT(_q_encrypted()), 58 Qt::DirectConnection); 59 QObject::connect(sslSocket, SIGNAL(sslErrors(QList<QSslError>)), 60 this, SLOT(_q_sslErrors(QList<QSslError>)), 61 Qt::DirectConnection); 62 QObject::connect(sslSocket, SIGNAL(encryptedBytesWritten(qint64)), 63 this, SLOT(_q_encryptedBytesWritten(qint64)), 64 Qt::DirectConnection); 65 } 66 #endif 67 }
看到了我们熟悉的QTcpSocket类，该类继承于QAbstractSocket，封装了平台socket
回到前面，继续看postRequst又做了哪些事情呢？再看代码
1 void QNetworkAccessHttpBackend::postRequest() 2 { 3 QThread *thread = 0; 4 if (isSynchronous()) { 5 // A synchronous HTTP request uses its own thread 6 thread = new QThread(); 7 QObject::connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater())); 8 thread->start(); 9 } else if (!manager->httpThread) { 10 // We use the manager-global thread. 11 // At some point we could switch to having multiple threads if it makes sense. 12 manager->httpThread = new QThread(); 13 QObject::connect(manager->httpThread, SIGNAL(finished()), manager->httpThread, SLOT(deleteLater())); 14 manager->httpThread->start(); 15 #ifndef QT_NO_NETWORKPROXY 16 qRegisterMetaType<QNetworkProxy>("QNetworkProxy"); 17 #endif 18 #ifndef QT_NO_OPENSSL 19 qRegisterMetaType<QList<QSslError> >("QList<QSslError>"); 20 qRegisterMetaType<QSslConfiguration>("QSslConfiguration"); 21 #endif 22 qRegisterMetaType<QList<QPair<QByteArray,QByteArray> > >("QList<QPair<QByteArray,QByteArray> >"); 23 qRegisterMetaType<QHttpNetworkRequest>("QHttpNetworkRequest"); 24 qRegisterMetaType<QNetworkReply::NetworkError>("QNetworkReply::NetworkError"); 25 qRegisterMetaType<QSharedPointer<char> >("QSharedPointer<char>"); 26 27 thread = manager->httpThread; 28 } else { 29 // Asynchronous request, thread already exists 30 thread = manager->httpThread; 31 } 32 33 QUrl url = request().url(); 34 httpRequest.setUrl(url); 35 36 bool ssl = url.scheme().toLower() == QLatin1String("https"); 37 setAttribute(QNetworkRequest::ConnectionEncryptedAttribute, ssl); 38 httpRequest.setSsl(ssl); 39 40 41 #ifndef QT_NO_NETWORKPROXY 42 QNetworkProxy transparentProxy, cacheProxy; 43 44 foreach (const QNetworkProxy &p, proxyList()) { 45 // use the first proxy that works 46 // for non-encrypted connections, any transparent or HTTP proxy 47 // for encrypted, only transparent proxies 48 if (!ssl 49 && (p.capabilities() & QNetworkProxy::CachingCapability) 50 && (p.type() == QNetworkProxy::HttpProxy || 51 p.type() == QNetworkProxy::HttpCachingProxy)) { 52 cacheProxy = p; 53 transparentProxy = QNetworkProxy::NoProxy; 54 break; 55 } 56 if (p.isTransparentProxy()) { 57 transparentProxy = p; 58 cacheProxy = QNetworkProxy::NoProxy; 59 break; 60 } 61 } 62 63 // check if at least one of the proxies 64 if (transparentProxy.type() == QNetworkProxy::DefaultProxy && 65 cacheProxy.type() == QNetworkProxy::DefaultProxy) { 66 // unsuitable proxies 67 QMetaObject::invokeMethod(this, "error", isSynchronous() ? Qt::DirectConnection : Qt::QueuedConnection, 68 Q_ARG(QNetworkReply::NetworkError, QNetworkReply::ProxyNotFoundError), 69 Q_ARG(QString, tr("No suitable proxy found"))); 70 QMetaObject::invokeMethod(this, "finished", isSynchronous() ? Qt::DirectConnection : Qt::QueuedConnection); 71 return; 72 } 73 #endif 74 75 76 bool loadedFromCache = false; 77 httpRequest.setPriority(convert(request().priority())); 78 79 switch (operation()) { 80 case QNetworkAccessManager::GetOperation: 81 httpRequest.setOperation(QHttpNetworkRequest::Get); 82 loadedFromCache = loadFromCacheIfAllowed(httpRequest); 83 break; 84 85 case QNetworkAccessManager::HeadOperation: 86 httpRequest.setOperation(QHttpNetworkRequest::Head); 87 loadedFromCache = loadFromCacheIfAllowed(httpRequest); 88 break; 89 90 case QNetworkAccessManager::PostOperation: 91 invalidateCache(); 92 httpRequest.setOperation(QHttpNetworkRequest::Post); 93 createUploadByteDevice(); 94 break; 95 96 case QNetworkAccessManager::PutOperation: 97 invalidateCache(); 98 httpRequest.setOperation(QHttpNetworkRequest::Put); 99 createUploadByteDevice(); 100 break; 101 102 case QNetworkAccessManager::DeleteOperation: 103 invalidateCache(); 104 httpRequest.setOperation(QHttpNetworkRequest::Delete); 105 break; 106 107 case QNetworkAccessManager::CustomOperation: 108 invalidateCache(); // for safety reasons, we don't know what the operation does 109 httpRequest.setOperation(QHttpNetworkRequest::Custom); 110 createUploadByteDevice(); 111 httpRequest.setCustomVerb(request().attribute( 112 QNetworkRequest::CustomVerbAttribute).toByteArray()); 113 break; 114 115 default: 116 break; // can't happen 117 } 118 119 if (loadedFromCache) { 120 // commented this out since it will be called later anyway 121 // by copyFinished() 122 //QNetworkAccessBackend::finished(); 123 return; // no need to send the request! :) 124 } 125 126 QList<QByteArray> headers = request().rawHeaderList(); 127 if (resumeOffset != 0) { 128 if (headers.contains("Range")) { 129 // Need to adjust resume offset for user specified range 130 131 headers.removeOne("Range"); 132 133 // We've already verified that requestRange starts with "bytes=", see canResume. 134 QByteArray requestRange = request().rawHeader("Range").mid(6); 135 136 int index = requestRange.indexOf('-'); 137 138 quint64 requestStartOffset = requestRange.left(index).toULongLong(); 139 quint64 requestEndOffset = requestRange.mid(index + 1).toULongLong(); 140 141 requestRange = "bytes=" + QByteArray::number(resumeOffset + requestStartOffset) + 142 '-' + QByteArray::number(requestEndOffset); 143 144 httpRequest.setHeaderField("Range", requestRange); 145 } else { 146 httpRequest.setHeaderField("Range", "bytes=" + QByteArray::number(resumeOffset) + '-'); 147 } 148 } 149 150 foreach (const QByteArray &header, headers) 151 httpRequest.setHeaderField(header, request().rawHeader(header)); 152 153 if (request().attribute(QNetworkRequest::HttpPipeliningAllowedAttribute).toBool() == true) 154 httpRequest.setPipeliningAllowed(true); 155 156 if (static_cast<QNetworkRequest::LoadControl> 157 (request().attribute(QNetworkRequest::AuthenticationReuseAttribute, 158 QNetworkRequest::Automatic).toInt()) == QNetworkRequest::Manual) 159 httpRequest.setWithCredentials(false); 160 161 162 // Create the HTTP thread delegate 163 QHttpThreadDelegate *delegate = new QHttpThreadDelegate; 164 #ifndef QT_NO_BEARERMANAGEMENT 165 QVariant v(property("_q_networksession")); 166 if (v.isValid()) 167 delegate->networkSession = qvariant_cast<QSharedPointer<QNetworkSession> >(v); 168 #endif 169 170 // For the synchronous HTTP, this is the normal way the delegate gets deleted 171 // For the asynchronous HTTP this is a safety measure, the delegate deletes itself when HTTP is finished 172 connect(thread, SIGNAL(finished()), delegate, SLOT(deleteLater())); 173 174 // Set the properties it needs 175 delegate->httpRequest = httpRequest; 176 #ifndef QT_NO_NETWORKPROXY 177 delegate->cacheProxy = cacheProxy; 178 delegate->transparentProxy = transparentProxy; 179 #endif 180 delegate->ssl = ssl; 181 #ifndef QT_NO_OPENSSL 182 if (ssl) 183 delegate->incomingSslConfiguration = request().sslConfiguration(); 184 #endif 185 186 // Do we use synchronous HTTP? 187 delegate->synchronous = isSynchronous(); 188 189 // The authentication manager is used to avoid the BlockingQueuedConnection communication 190 // from HTTP thread to user thread in some cases. 191 delegate->authenticationManager = manager->authenticationManager; 192 193 if (!isSynchronous()) { 194 // Tell our zerocopy policy to the delegate 195 delegate->downloadBufferMaximumSize = 196 request().attribute(QNetworkRequest::MaximumDownloadBufferSizeAttribute).toLongLong(); 197 198 // These atomic integers are used for signal compression 199 delegate->pendingDownloadData = pendingDownloadDataEmissions; 200 delegate->pendingDownloadProgress = pendingDownloadProgressEmissions; 201 202 // Connect the signals of the delegate to us 203 connect(delegate, SIGNAL(downloadData(QByteArray)), 204 this, SLOT(replyDownloadData(QByteArray)), 205 Qt::QueuedConnection); 206 connect(delegate, SIGNAL(downloadFinished()), 207 this, SLOT(replyFinished()), 208 Qt::QueuedConnection); 209 connect(delegate, SIGNAL(downloadMetaData(QList<QPair<QByteArray,QByteArray> >,int,QString,bool,QSharedPointer<char>,qint64)), 210 this, SLOT(replyDownloadMetaData(QList<QPair<QByteArray,QByteArray> >,int,QString,bool,QSharedPointer<char>,qint64)), 211 Qt::QueuedConnection); 212 connect(delegate, SIGNAL(downloadProgress(qint64,qint64)), 213 this, SLOT(replyDownloadProgressSlot(qint64,qint64)), 214 Qt::QueuedConnection); 215 connect(delegate, SIGNAL(error(QNetworkReply::NetworkError,QString)), 216 this, SLOT(httpError(QNetworkReply::NetworkError, const QString)), 217 Qt::QueuedConnection); 218 #ifndef QT_NO_OPENSSL 219 connect(delegate, SIGNAL(sslConfigurationChanged(QSslConfiguration)), 220 this, SLOT(replySslConfigurationChanged(QSslConfiguration)), 221 Qt::QueuedConnection); 222 #endif 223 // Those need to report back, therefire BlockingQueuedConnection 224 connect(delegate, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)), 225 this, SLOT(httpAuthenticationRequired(QHttpNetworkRequest,QAuthenticator*)), 226 Qt::BlockingQueuedConnection); 227 #ifndef QT_NO_NETWORKPROXY 228 connect (delegate, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)), 229 this, SLOT(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)), 230 Qt::BlockingQueuedConnection); 231 #endif 232 #ifndef QT_NO_OPENSSL 233 connect(delegate, SIGNAL(sslErrors(QList<QSslError>,bool*,QList<QSslError>*)), 234 this, SLOT(replySslErrors(const QList<QSslError> &, bool *, QList<QSslError> *)), 235 Qt::BlockingQueuedConnection); 236 #endif 237 // This signal we will use to start the request. 238 connect(this, SIGNAL(startHttpRequest()), delegate, SLOT(startRequest())); 239 connect(this, SIGNAL(abortHttpRequest()), delegate, SLOT(abortRequest())); 240 241 // To throttle the connection. 242 QObject::connect(this, SIGNAL(readBufferSizeChanged(qint64)), delegate, SLOT(readBufferSizeChanged(qint64))); 243 QObject::connect(this, SIGNAL(readBufferFreed(qint64)), delegate, SLOT(readBufferFreed(qint64))); 244 245 if (uploadByteDevice) { 246 QNonContiguousByteDeviceThreadForwardImpl *forwardUploadDevice = 247 new QNonContiguousByteDeviceThreadForwardImpl(uploadByteDevice->atEnd(), uploadByteDevice->size()); 248 if (uploadByteDevice->isResetDisabled()) 249 forwardUploadDevice->disableReset(); 250 forwardUploadDevice->setParent(delegate); // needed to make sure it is moved on moveToThread() 251 delegate->httpRequest.setUploadByteDevice(forwardUploadDevice); 252 253 // From main thread to user thread: 254 QObject::connect(this, SIGNAL(haveUploadData(QByteArray, bool, qint64)), 255 forwardUploadDevice, SLOT(haveDataSlot(QByteArray, bool, qint64)), Qt::QueuedConnection); 256 QObject::connect(uploadByteDevice.data(), SIGNAL(readyRead()), 257 forwardUploadDevice, SIGNAL(readyRead()), 258 Qt::QueuedConnection); 259 260 // From http thread to user thread: 261 QObject::connect(forwardUploadDevice, SIGNAL(wantData(qint64)), 262 this, SLOT(wantUploadDataSlot(qint64))); 263 QObject::connect(forwardUploadDevice, SIGNAL(processedData(qint64)), 264 this, SLOT(sentUploadDataSlot(qint64))); 265 connect(forwardUploadDevice, SIGNAL(resetData(bool*)), 266 this, SLOT(resetUploadDataSlot(bool*)), 267 Qt::BlockingQueuedConnection); // this is the only one with BlockingQueued! 268 } 269 } else if (isSynchronous()) { 270 connect(this, SIGNAL(startHttpRequestSynchronously()), delegate, SLOT(startRequestSynchronously()), Qt::BlockingQueuedConnection); 271 272 if (uploadByteDevice) { 273 // For the synchronous HTTP use case the use thread (this one here) is blocked 274 // so we cannot use the asynchronous upload architecture. 275 // We therefore won't use the QNonContiguousByteDeviceThreadForwardImpl but directly 276 // use the uploadByteDevice provided to us by the QNetworkReplyImpl. 277 // The code that is in QNetworkReplyImplPrivate::setup() makes sure it is safe to use from a thread 278 // since it only wraps a QRingBuffer 279 delegate->httpRequest.setUploadByteDevice(uploadByteDevice.data()); 280 } 281 } 282 283 284 // Move the delegate to the http thread 285 delegate->moveToThread(thread); 286 // This call automatically moves the uploadDevice too for the asynchronous case. 287 288 // Send an signal to the delegate so it starts working in the other thread 289 if (isSynchronous()) { 290 emit startHttpRequestSynchronously(); // This one is BlockingQueuedConnection, so it will return when all work is done 291 292 if (delegate->incomingErrorCode != QNetworkReply::NoError) { 293 replyDownloadMetaData 294 (delegate->incomingHeaders, 295 delegate->incomingStatusCode, 296 delegate->incomingReasonPhrase, 297 delegate->isPipeliningUsed, 298 QSharedPointer<char>(), 299 delegate->incomingContentLength); 300 replyDownloadData(delegate->synchronousDownloadData); 301 httpError(delegate->incomingErrorCode, delegate->incomingErrorDetail); 302 } else { 303 replyDownloadMetaData 304 (delegate->incomingHeaders, 305 delegate->incomingStatusCode, 306 delegate->incomingReasonPhrase, 307 delegate->isPipeliningUsed, 308 QSharedPointer<char>(), 309 delegate->incomingContentLength); 310 replyDownloadData(delegate->synchronousDownloadData); 311 } 312 313 // End the thread. It will delete itself from the finished() signal 314 thread->quit(); 315 thread->wait(5000); 316 317 finished(); 318 } else { 319 emit startHttpRequest(); // Signal to the HTTP thread and go back to user. 320 } 321 }
完了下面这些动作：
1、看Cache中是否保存有过去浏览的内容，如果有还要看是否超出生存时间(Expiration
Time)；
2、设定Url、Header和数据内容（需要提交的数据）；
3、调用QNetworkAccessHttpBackendCache::sendRequest()发送请求内容；
4、把QHttpNetworkReply的信号与QNetworkAccessHttpBackend的槽连接起来，完成后续处理。
分析QNetworkAccessManager的时候，有一段设定HTTP的请求包的Header，当时没进行深入的分析。
1 void QHttpNetworkConnectionPrivate::prepareRequest(HttpMessagePair &messagePair) 2 { 3 QHttpNetworkRequest &request = messagePair.first; 4 QHttpNetworkReply *reply = messagePair.second; 5 6 // add missing fields for the request 7 QByteArray value; 8 // check if Content-Length is provided 9 QIODevice *data = request.data(); 10 if (data && request.contentLength() == -1) { 11 if (!data->isSequential()) 12 request.setContentLength(data->size()); 13 else 14 bufferData(messagePair); // ### or do chunked upload 15 } 16 // set the Connection/Proxy-Connection: Keep-Alive headers 17 #ifndef QT_NO_NETWORKPROXY 18 if (networkProxy.type() == QNetworkProxy::HttpCachingProxy) { 19 value = request.headerField("proxy-connection"); 20 if (value.isEmpty()) 21 request.setHeaderField("Proxy-Connection", "Keep-Alive"); 22 } else { 23 #endif 24 value = request.headerField("connection"); 25 if (value.isEmpty()) 26 request.setHeaderField("Connection", "Keep-Alive"); 27 #ifndef QT_NO_NETWORKPROXY 28 } 29 #endif 30 31 // If the request had a accept-encoding set, we better not mess 32 // with it. If it was not set, we announce that we understand gzip 33 // and remember this fact in request.d->autoDecompress so that 34 // we can later decompress the HTTP reply if it has such an 35 // encoding. 36 value = request.headerField("accept-encoding"); 37 if (value.isEmpty()) { 38 #ifndef QT_NO_COMPRESS 39 request.setHeaderField("Accept-Encoding", "gzip"); 40 request.d->autoDecompress = true; 41 #else 42 // if zlib is not available set this to false always 43 request.d->autoDecompress = false; 44 #endif 45 } 46 // set the User Agent 47 value = request.headerField("user-agent"); 48 if (value.isEmpty()) 49 request.setHeaderField("User-Agent", "Mozilla/5.0"); 50 // set the host 51 value = request.headerField("host"); 52 if (value.isEmpty()) { 53 QByteArray host = QUrl::toAce(hostName); 54 55 int port = request.url().port(); 56 if (port != -1) { 57 host += ':'; 58 host += QByteArray::number(port); 59 } 60 61 request.setHeaderField("Host", host); 62 } 63 64 reply->d_func()->requestIsPrepared = true; 65 }
如果想模拟IE浏览器，或者想修改成任何你希望的信息，就是在这里修改。
在设定了这些请求信息之后，发送的请求信息包是什么样子的呢？我把工具拦截的信息包具体情况贴出来
有一种落差是，你配不上自己的野心，也辜负了所受的苦难
