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_NETWORKPROXY29 // Get the proxy information30 d->resolveProxy(hostName, port);31 if (d->proxyInUse.type() == QNetworkProxy::DefaultProxy) {32 // failed to setup the proxy33 d->socketError = QAbstractSocket::UnsupportedSocketOperationError;34 setErrorString(QAbstractSocket::tr("Operation on socket is not supported"));35 emit error(d->socketError);36 return;37 }38 #endif39 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 () << temp);50 d->_q_startConnecting(info);51 #ifndef QT_NO_NETWORKPROXY52 } else if (d->proxyInUse.capabilities() & QNetworkProxy::HostNameLookupCapability) {53 // the proxy supports connection by name, so use it54 d->startConnectingByName(hostName);55 return;56 #endif57 } 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::UnknownSocketError10 ) && 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 candidate27 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 to32 // connect. So we just pretend we didn't see this address.33 continue;34 }35 #endif36 37 if (!initSocketLayer(host.protocol())) {38 // hope that the next address is better39 continue;40 }41 42 // Tries to connect to the address. If it succeeds immediately43 // (localhost address on BSD or any UDP connect), emit44 // 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 yet52 cachedSocketDescriptor = socketEngine->socketDescriptor();53 54 // Check that we're in delayed connection state. If not, try55 // the next address56 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 call72 // _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_NETWORKPROXY32 // proxy type must have been resolved by now33 if (proxy.type() == QNetworkProxy::DefaultProxy)34 return 0;35 #endif36 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 #endif14 15 // Create the socket16 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::UdpSocket30 && !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 data38 if (socketType == QAbstractSocket::TcpSocket39 && !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, found44 // 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 #endif13 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 EOF10 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 future22 // if we're not connected, return -1 indicating EOF23 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 close10 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 #endif12 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::read26 ret = 0;27 break;28 default:29 break;30 }31 } else {32 if (WSAGetLastError() == WSAEWOULDBLOCK)33 ret = -2;34 else35 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 else27 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 WSAENOBUFS14 for (;;) {15 qint64 bytesToSend = qMin (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 else30 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 flags={...}) 行679 + 0x10 字节 C++18 QtGuid4.dll!QGuiEventDispatcherWin32::processEvents(QFlags flags={...}) 行1182 + 0x15 字节 C++19 QtCored4.dll!QEventLoop::processEvents(QFlags flags={...}) 行150 C++20 QtCored4.dll!QEventLoop::exec(QFlags 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 C25 fortuneclient.exe!WinMainCRTStartup() 行399 C26 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()));
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 ( 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 71 (request.attribute(QNetworkRequest::CookieLoadControlAttribute, 72 QNetworkRequest::Automatic).toInt()) == QNetworkRequest::Automatic) { 73 if (d->cookieJar) { 74 QList 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_OPENSSL105 reply->setSslConfiguration(request.sslConfiguration());106 #endif107 108 // fourth step: setup the reply109 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 )), SLOT(_q_replySslErrors(QList )));10 #endif11 #ifndef QT_NO_BEARERMANAGEMENT12 activeReplyCount++;13 #endif14 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 Ajax13 // in QtWebKit.14 QVariant synchronousHttpAttribute = req.attribute(15 static_cast (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 (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 or36 // fixed size non-sequential37 // just start the operation38 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 buffering46 // if not, we will buffer anyway47 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, without61 // invoking methods in a QueuedConnection62 #ifndef QT_NO_HTTP63 if (qobject_cast (backend) || (backend && backend->isSynchronous())) {64 _q_startOperation();65 } else {66 QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection);67 }68 #else69 if (backend && backend->isSynchronous())70 _q_startOperation();71 else72 QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection);73 #endif // QT_NO_HTTP74 }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 (see12 // 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_BEARERMANAGEMENT22 // backend failed to start because the session state is not Connected.23 // QNetworkAccessManager will call _q_startOperation again for us when the session24 // state changes.25 state = WaitingForSession;26 27 QSharedPointer 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 #else45 qWarning("Backend start failed");46 state = Working;47 error(QNetworkReplyImpl::UnknownNetworkError,48 QCoreApplication::translate("QNetworkReply", "backend start error."));49 finished();50 #endif51 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 (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 buffer17 forever {18 bytesToBuffer = outgoingData->bytesAvailable();19 // unknown? just try 2 kB, this also ensures we always try to read the EOF20 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 again34 outgoingDataBuffer->chop(bytesToBuffer);35 36 break;37 } else {38 // don't break, try to read() again39 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 else19 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 request13 }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 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 QNetworkAccessBackendFactory2 class QNetworkAccessDebugPipeBackendFactory: public QNetworkAccessBackendFactory3 class QNetworkAccessFileBackendFactory: public QNetworkAccessBackendFactory4 class QNetworkAccessFtpBackendFactory: public QNetworkAccessBackendFactory5 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 request17 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 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 backend12 setProperty("_q_networksession", QVariant::fromValue(networkSession));13 } else {14 // Session not ready, but can skip for loopback connections15 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 opened25 return false;26 }27 }28 }29 #endif30 31 #ifndef QT_NO_NETWORKPROXY32 #ifndef QT_NO_BEARERMANAGEMENT33 // 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 use40 QVariant v = session->sessionProperty(QLatin1String("ActiveConfiguration"));41 if (v.isValid())42 config = configManager.configurationFromIdentifier(qvariant_cast (v));43 // Fallback to using the configuration if no active configuration44 if (!config.isValid())45 config = session->configuration();46 // or unspecified configuration if that is no good either47 if (!config.isValid())48 config = QNetworkConfiguration();49 }50 reply->proxyList = manager->queryProxy(QNetworkProxyQuery(config, url()));51 #else // QT_NO_BEARERMANAGEMENT52 // Without bearer management, the proxy depends only on the url53 reply->proxyList = manager->queryProxy(QNetworkProxyQuery(url()));54 #endif55 #endif56 57 // now start the request58 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"); 17 #endif 18 #ifndef QT_NO_OPENSSL 19 qRegisterMetaType >("QList "); 20 qRegisterMetaType ("QSslConfiguration"); 21 #endif 22 qRegisterMetaType > >("QList >"); 23 qRegisterMetaType ("QHttpNetworkRequest"); 24 qRegisterMetaType ("QNetworkReply::NetworkError"); 25 qRegisterMetaType >("QSharedPointer "); 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 does109 httpRequest.setOperation(QHttpNetworkRequest::Custom);110 createUploadByteDevice();111 httpRequest.setCustomVerb(request().attribute(112 QNetworkRequest::CustomVerbAttribute).toByteArray());113 break;114 115 default:116 break; // can't happen117 }118 119 if (loadedFromCache) {120 // commented this out since it will be called later anyway121 // by copyFinished()122 //QNetworkAccessBackend::finished();123 return; // no need to send the request! :)124 }125 126 QList headers = request().rawHeaderList();127 if (resumeOffset != 0) {128 if (headers.contains("Range")) {129 // Need to adjust resume offset for user specified range130 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 157 (request().attribute(QNetworkRequest::AuthenticationReuseAttribute,158 QNetworkRequest::Automatic).toInt()) == QNetworkRequest::Manual)159 httpRequest.setWithCredentials(false);160 161 162 // Create the HTTP thread delegate163 QHttpThreadDelegate *delegate = new QHttpThreadDelegate;164 #ifndef QT_NO_BEARERMANAGEMENT165 QVariant v(property("_q_networksession"));166 if (v.isValid())167 delegate->networkSession = qvariant_cast >(v);168 #endif169 170 // For the synchronous HTTP, this is the normal way the delegate gets deleted171 // For the asynchronous HTTP this is a safety measure, the delegate deletes itself when HTTP is finished172 connect(thread, SIGNAL(finished()), delegate, SLOT(deleteLater()));173 174 // Set the properties it needs175 delegate->httpRequest = httpRequest;176 #ifndef QT_NO_NETWORKPROXY177 delegate->cacheProxy = cacheProxy;178 delegate->transparentProxy = transparentProxy;179 #endif180 delegate->ssl = ssl;181 #ifndef QT_NO_OPENSSL182 if (ssl)183 delegate->incomingSslConfiguration = request().sslConfiguration();184 #endif185 186 // Do we use synchronous HTTP?187 delegate->synchronous = isSynchronous();188 189 // The authentication manager is used to avoid the BlockingQueuedConnection communication190 // 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 delegate195 delegate->downloadBufferMaximumSize =196 request().attribute(QNetworkRequest::MaximumDownloadBufferSizeAttribute).toLongLong();197 198 // These atomic integers are used for signal compression199 delegate->pendingDownloadData = pendingDownloadDataEmissions;200 delegate->pendingDownloadProgress = pendingDownloadProgressEmissions;201 202 // Connect the signals of the delegate to us203 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 >,int,QString,bool,QSharedPointer ,qint64)),210 this, SLOT(replyDownloadMetaData(QList >,int,QString,bool,QSharedPointer ,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_OPENSSL219 connect(delegate, SIGNAL(sslConfigurationChanged(QSslConfiguration)),220 this, SLOT(replySslConfigurationChanged(QSslConfiguration)),221 Qt::QueuedConnection);222 #endif223 // Those need to report back, therefire BlockingQueuedConnection224 connect(delegate, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)),225 this, SLOT(httpAuthenticationRequired(QHttpNetworkRequest,QAuthenticator*)),226 Qt::BlockingQueuedConnection);227 #ifndef QT_NO_NETWORKPROXY228 connect (delegate, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),229 this, SLOT(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),230 Qt::BlockingQueuedConnection);231 #endif232 #ifndef QT_NO_OPENSSL233 connect(delegate, SIGNAL(sslErrors(QList ,bool*,QList *)),234 this, SLOT(replySslErrors(const QList &, bool *, QList *)),235 Qt::BlockingQueuedConnection);236 #endif237 // 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 blocked274 // so we cannot use the asynchronous upload architecture.275 // We therefore won't use the QNonContiguousByteDeviceThreadForwardImpl but directly276 // 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 thread278 // since it only wraps a QRingBuffer279 delegate->httpRequest.setUploadByteDevice(uploadByteDevice.data());280 }281 }282 283 284 // Move the delegate to the http thread285 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 thread289 if (isSynchronous()) {290 emit startHttpRequestSynchronously(); // This one is BlockingQueuedConnection, so it will return when all work is done291 292 if (delegate->incomingErrorCode != QNetworkReply::NoError) {293 replyDownloadMetaData294 (delegate->incomingHeaders,295 delegate->incomingStatusCode,296 delegate->incomingReasonPhrase,297 delegate->isPipeliningUsed,298 QSharedPointer (),299 delegate->incomingContentLength);300 replyDownloadData(delegate->synchronousDownloadData);301 httpError(delegate->incomingErrorCode, delegate->incomingErrorDetail);302 } else {303 replyDownloadMetaData304 (delegate->incomingHeaders,305 delegate->incomingStatusCode,306 delegate->incomingReasonPhrase,307 delegate->isPipeliningUsed,308 QSharedPointer (),309 delegate->incomingContentLength);310 replyDownloadData(delegate->synchronousDownloadData);311 }312 313 // End the thread. It will delete itself from the finished() signal314 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 host13 QUrl urlCopy = httpRequest.url();14 urlCopy.setPort(urlCopy.port(ssl ? 443 : 80));15 16 #ifndef QT_NO_NETWORKPROXY17 if (transparentProxy.type() != QNetworkProxy::NoProxy)18 cacheKey = makeCacheKey(urlCopy, &transparentProxy);19 else if (cacheProxy.type() != QNetworkProxy::NoProxy)20 cacheKey = makeCacheKey(urlCopy, &cacheProxy);21 else22 #endif23 cacheKey = makeCacheKey(urlCopy, 0);24 25 26 // the http object is actually a QHttpNetworkConnection27 httpConnection = static_cast (connections.localData()->requestEntryNow(cacheKey));28 if (httpConnection == 0) {29 // no entry in cache; create an object30 // the http object is actually a QHttpNetworkConnection31 #ifdef QT_NO_BEARERMANAGEMENT32 httpConnection = new QNetworkAccessCachedHttpConnection(urlCopy.host(), urlCopy.port(), ssl);33 #else34 httpConnection = new QNetworkAccessCachedHttpConnection(urlCopy.host(), urlCopy.port(), ssl, networkSession);35 #endif36 #ifndef QT_NO_OPENSSL37 // Set the QSslConfiguration from this QNetworkRequest.38 if (ssl && incomingSslConfiguration != QSslConfiguration::defaultConfiguration()) {39 httpConnection->setSslConfiguration(incomingSslConfiguration);40 }41 #endif42 43 #ifndef QT_NO_NETWORKPROXY44 httpConnection->setTransparentProxy(transparentProxy);45 httpConnection->setCacheProxy(cacheProxy);46 #endif47 48 // cache the QHttpNetworkConnection corresponding to this cache key49 connections.localData()->addEntry(cacheKey, httpConnection);50 }51 52 53 // Send the request to the connection54 httpReply = httpConnection->sendRequest(httpRequest);55 httpReply->setParent(this);56 57 // Connect the reply signals that we need to handle and then forward58 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 used76 connect(httpReply,SIGNAL(readyRead()), this, SLOT(readyReadSlot()));77 connect(httpReply,SIGNAL(dataReadProgress(int, int)), this, SLOT(dataReadProgressSlot(int,int)));78 #ifndef QT_NO_OPENSSL79 connect(httpReply,SIGNAL(sslErrors(const QList )), this, SLOT(sslErrorsSlot(QList )));80 #endif81 82 // In the asynchronous HTTP case we can just forward those signals83 // Connect the reply signals that we can directly forward84 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 later10 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 QueuedConnection23 // It is the only place _q_startNextRequest is called directly without going24 // through the event loop using a QueuedConnection.25 // This is dangerous because of recursion that might occur when emitting26 // signals as DirectConnection from this code path. Therefore all signal27 // emissions that can come out from this code path need to28 // 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 terminated14 if (!channels[i].resetUploadData())15 continue;16 channels[i].sendRequest();17 }18 }19 20 // dequeue new ones21 22 // return fast if there is nothing to do23 if (highPriorityQueue.isEmpty() && lowPriorityQueue.isEmpty())24 return;25 // try to get a free AND connected socket26 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 sockets34 // ### FIXME we should move this to the beginning of the function35 // as soon as QtWebkit is properly using the pipelining36 // (e.g. not for XMLHttpRequest or the first page load)37 // ### FIXME we should also divide the requests more even38 // on the connected sockets39 //tryToFillPipeline(socket);40 // return fast if there is nothing to pipeline41 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 again19 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 (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 data101 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 happened107 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 loop112 break;113 } else {114 qint64 currentWriteSize = socket->write(readPointer, currentReadSize);115 if (currentWriteSize == -1 || currentWriteSize != currentReadSize) {116 // socket broke down117 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 again127 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 pipelining145 //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 called149 // this is needed if the sends an reply before we have finished sending the request. In that150 // case receiveReply had been called before but ignored the server reply151 if (socket->bytesAvailable())152 QMetaObject::invokeMethod(this, "_q_receiveReply", Qt::QueuedConnection);153 break;154 }155 case QHttpNetworkConnectionChannel::ReadingState:156 // ignore _q_bytesWritten in these states157 // fall through158 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, QSharedPointernetworkSession)2 : QObject(*(new QHttpNetworkConnectionPrivate(hostName, port, encrypt)), parent)3 {4 Q_D(QHttpNetworkConnection);5 d->networkSession = networkSession;6 d->init();7 }
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 #endif10 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 #endif11 #ifndef QT_NO_BEARERMANAGEMENT12 //push session down to socket13 if (networkSession)14 socket->setProperty("_q_networksession", QVariant::fromValue(networkSession));15 #endif16 #ifndef QT_NO_NETWORKPROXY17 // Set by QNAM anyway, but let's be safe here18 socket->setProxy(QNetworkProxy::NoProxy);19 #endif20 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 come32 // while calling connectToHost().33 // In case of a cached hostname or an IP this34 // will then emit a signal to the user of QNetworkReply35 // but cannot be caught because the user did not have a chance yet36 // to connect to QNetworkReply's signals.37 qRegisterMetaType ("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_NETWORKPROXY47 QObject::connect(socket, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),48 this, SLOT(_q_proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),49 Qt::DirectConnection);50 #endif51 52 #ifndef QT_NO_OPENSSL53 QSslSocket *sslSocket = qobject_cast (socket);54 if (sslSocket) {55 // won't be a sslSocket if encrypt is false56 QObject::connect(sslSocket, SIGNAL(encrypted()),57 this, SLOT(_q_encrypted()),58 Qt::DirectConnection);59 QObject::connect(sslSocket, SIGNAL(sslErrors(QList )),60 this, SLOT(_q_sslErrors(QList )),61 Qt::DirectConnection);62 QObject::connect(sslSocket, SIGNAL(encryptedBytesWritten(qint64)),63 this, SLOT(_q_encryptedBytesWritten(qint64)),64 Qt::DirectConnection);65 }66 #endif67 } 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"); 17 #endif 18 #ifndef QT_NO_OPENSSL 19 qRegisterMetaType >("QList "); 20 qRegisterMetaType ("QSslConfiguration"); 21 #endif 22 qRegisterMetaType > >("QList >"); 23 qRegisterMetaType ("QHttpNetworkRequest"); 24 qRegisterMetaType ("QNetworkReply::NetworkError"); 25 qRegisterMetaType >("QSharedPointer "); 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 does109 httpRequest.setOperation(QHttpNetworkRequest::Custom);110 createUploadByteDevice();111 httpRequest.setCustomVerb(request().attribute(112 QNetworkRequest::CustomVerbAttribute).toByteArray());113 break;114 115 default:116 break; // can't happen117 }118 119 if (loadedFromCache) {120 // commented this out since it will be called later anyway121 // by copyFinished()122 //QNetworkAccessBackend::finished();123 return; // no need to send the request! :)124 }125 126 QList headers = request().rawHeaderList();127 if (resumeOffset != 0) {128 if (headers.contains("Range")) {129 // Need to adjust resume offset for user specified range130 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 157 (request().attribute(QNetworkRequest::AuthenticationReuseAttribute,158 QNetworkRequest::Automatic).toInt()) == QNetworkRequest::Manual)159 httpRequest.setWithCredentials(false);160 161 162 // Create the HTTP thread delegate163 QHttpThreadDelegate *delegate = new QHttpThreadDelegate;164 #ifndef QT_NO_BEARERMANAGEMENT165 QVariant v(property("_q_networksession"));166 if (v.isValid())167 delegate->networkSession = qvariant_cast >(v);168 #endif169 170 // For the synchronous HTTP, this is the normal way the delegate gets deleted171 // For the asynchronous HTTP this is a safety measure, the delegate deletes itself when HTTP is finished172 connect(thread, SIGNAL(finished()), delegate, SLOT(deleteLater()));173 174 // Set the properties it needs175 delegate->httpRequest = httpRequest;176 #ifndef QT_NO_NETWORKPROXY177 delegate->cacheProxy = cacheProxy;178 delegate->transparentProxy = transparentProxy;179 #endif180 delegate->ssl = ssl;181 #ifndef QT_NO_OPENSSL182 if (ssl)183 delegate->incomingSslConfiguration = request().sslConfiguration();184 #endif185 186 // Do we use synchronous HTTP?187 delegate->synchronous = isSynchronous();188 189 // The authentication manager is used to avoid the BlockingQueuedConnection communication190 // 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 delegate195 delegate->downloadBufferMaximumSize =196 request().attribute(QNetworkRequest::MaximumDownloadBufferSizeAttribute).toLongLong();197 198 // These atomic integers are used for signal compression199 delegate->pendingDownloadData = pendingDownloadDataEmissions;200 delegate->pendingDownloadProgress = pendingDownloadProgressEmissions;201 202 // Connect the signals of the delegate to us203 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 >,int,QString,bool,QSharedPointer ,qint64)),210 this, SLOT(replyDownloadMetaData(QList >,int,QString,bool,QSharedPointer ,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_OPENSSL219 connect(delegate, SIGNAL(sslConfigurationChanged(QSslConfiguration)),220 this, SLOT(replySslConfigurationChanged(QSslConfiguration)),221 Qt::QueuedConnection);222 #endif223 // Those need to report back, therefire BlockingQueuedConnection224 connect(delegate, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)),225 this, SLOT(httpAuthenticationRequired(QHttpNetworkRequest,QAuthenticator*)),226 Qt::BlockingQueuedConnection);227 #ifndef QT_NO_NETWORKPROXY228 connect (delegate, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),229 this, SLOT(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),230 Qt::BlockingQueuedConnection);231 #endif232 #ifndef QT_NO_OPENSSL233 connect(delegate, SIGNAL(sslErrors(QList ,bool*,QList *)),234 this, SLOT(replySslErrors(const QList &, bool *, QList *)),235 Qt::BlockingQueuedConnection);236 #endif237 // 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 blocked274 // so we cannot use the asynchronous upload architecture.275 // We therefore won't use the QNonContiguousByteDeviceThreadForwardImpl but directly276 // 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 thread278 // since it only wraps a QRingBuffer279 delegate->httpRequest.setUploadByteDevice(uploadByteDevice.data());280 }281 }282 283 284 // Move the delegate to the http thread285 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 thread289 if (isSynchronous()) {290 emit startHttpRequestSynchronously(); // This one is BlockingQueuedConnection, so it will return when all work is done291 292 if (delegate->incomingErrorCode != QNetworkReply::NoError) {293 replyDownloadMetaData294 (delegate->incomingHeaders,295 delegate->incomingStatusCode,296 delegate->incomingReasonPhrase,297 delegate->isPipeliningUsed,298 QSharedPointer (),299 delegate->incomingContentLength);300 replyDownloadData(delegate->synchronousDownloadData);301 httpError(delegate->incomingErrorCode, delegate->incomingErrorDetail);302 } else {303 replyDownloadMetaData304 (delegate->incomingHeaders,305 delegate->incomingStatusCode,306 delegate->incomingReasonPhrase,307 delegate->isPipeliningUsed,308 QSharedPointer (),309 delegate->incomingContentLength);310 replyDownloadData(delegate->synchronousDownloadData);311 }312 313 // End the thread. It will delete itself from the finished() signal314 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 else14 bufferData(messagePair); // ### or do chunked upload15 }16 // set the Connection/Proxy-Connection: Keep-Alive headers17 #ifndef QT_NO_NETWORKPROXY18 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 #endif24 value = request.headerField("connection");25 if (value.isEmpty())26 request.setHeaderField("Connection", "Keep-Alive");27 #ifndef QT_NO_NETWORKPROXY28 }29 #endif30 31 // If the request had a accept-encoding set, we better not mess32 // with it. If it was not set, we announce that we understand gzip33 // and remember this fact in request.d->autoDecompress so that34 // we can later decompress the HTTP reply if it has such an35 // encoding.36 value = request.headerField("accept-encoding");37 if (value.isEmpty()) {38 #ifndef QT_NO_COMPRESS39 request.setHeaderField("Accept-Encoding", "gzip");40 request.d->autoDecompress = true;41 #else42 // if zlib is not available set this to false always43 request.d->autoDecompress = false;44 #endif45 }46 // set the User Agent47 value = request.headerField("user-agent");48 if (value.isEmpty())49 request.setHeaderField("User-Agent", "Mozilla/5.0");50 // set the host51 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