path: root/src/corelib/io/qiodevice.cpp

// Copyright (C) 2016 The Qt Company Ltd.// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only//#define QIODEVICE_DEBUG#include"qbytearray.h"#include"qdebug.h"#include"qiodevice_p.h"#include"qfile.h"#include"qstringlist.h"#include"qdir.h"#include"private/qtools_p.h"#include <algorithm> QT_BEGIN_NAMESPACE using namespaceQt::StringLiterals;using namespace QtMiscUtils;[[maybe_unused]]static voiddebugBinaryString(const char*input, qint64 maxlen){ QByteArray tmp; qlonglong startOffset =0;for(qint64 i =0; i < maxlen; ++i) { tmp += input[i];if((i %16) ==15|| i == (maxlen -1)) {printf("\n%15lld:", startOffset); startOffset += tmp.size();for(qsizetype j =0; j < tmp.size(); ++j)printf(" %02x",int(uchar(tmp[j])));for(qsizetype j = tmp.size(); j <16+1; ++j)printf(" ");for(qsizetype j =0; j < tmp.size(); ++j)printf("%c",isAsciiPrintable(tmp[j]) ? tmp[j] :'.'); tmp.clear();}}printf("\n\n");}#define Q_VOID Q_DECL_COLD_FUNCTION static voidcheckWarnMessage(const QIODevice *device,const char*function,const char*what){#if !defined(QT_NO_WARNING_OUTPUT) && !defined(QT_NO_DEBUG_STREAM) QDebug d =qWarning(); d.noquote(); d.nospace(); d <<"QIODevice::"<< function;#ifndef QT_NO_QOBJECT d <<" ("<< device->metaObject()->className();if(!device->objectName().isEmpty()) d <<",\""<< device->objectName() <<'"';if(const QFile *f = qobject_cast<const QFile *>(device)) d <<",\""<<QDir::toNativeSeparators(f->fileName()) <<'"'; d <<')';#elseQ_UNUSED(device);#endif// !QT_NO_QOBJECT d <<": "<< what;#elseQ_UNUSED(device);Q_UNUSED(function);Q_UNUSED(what);#endif// QT_NO_WARNING_OUTPUT}#define CHECK_MAXLEN(function, returnType) \ do { \ if (maxSize < 0) { \ checkWarnMessage(this, #function,"Called with maxSize < 0"); \ return returnType; \ } \ } while (0)#define CHECK_LINEMAXLEN(function, returnType) \ do { \ if (maxSize < 2) { \ checkWarnMessage(this, #function,"Called with maxSize < 2"); \ return returnType; \ } \ } while (0)#define CHECK_LINEMAXLEN_1(function, returnType) \ do { \ if (maxSize < 1) { \ checkWarnMessage(this, #function,"Called with maxSize < 1"); \ return returnType; \ } \ } while (0)#define CHECK_MAXBYTEARRAYSIZE(function) \ do { \ if (maxSize >= QByteArray::maxSize()) { \ checkWarnMessage(this, #function,"maxSize argument exceeds QByteArray size limit"); \ maxSize = QByteArray::maxSize() - 1; \ } \ } while (0)#define CHECK_WRITABLE(function, returnType) \ do { \ if ((d->openMode & WriteOnly) == 0) { \ if (d->openMode == NotOpen) { \ checkWarnMessage(this, #function,"device not open"); \ return returnType; \ } \ checkWarnMessage(this, #function,"ReadOnly device"); \ return returnType; \ } \ } while (0)#define CHECK_READABLE(function, returnType) \ do { \ if ((d->openMode & ReadOnly) == 0) { \ if (d->openMode == NotOpen) { \ checkWarnMessage(this, #function,"device not open"); \ return returnType; \ } \ checkWarnMessage(this, #function,"WriteOnly device"); \ return returnType; \ } \ } while (0)/*! \internal */QIODevicePrivate::QIODevicePrivate(decltype(QObjectPrivateVersion) version)#ifndef QT_NO_QOBJECT:QObjectPrivate(version)#endif{Q_UNUSED(version);}/*! \internal */QIODevicePrivate::~QIODevicePrivate(){}/*! \class QIODevice \inmodule QtCore \reentrant \brief The QIODevice class is the base interface class of all I/O devices in Qt. \ingroup io QIODevice provides both a common implementation and an abstract interface for devices that support reading and writing of blocks of data, such as QFile, QBuffer and QTcpSocket. QIODevice is abstract and cannot be instantiated, but it is common to use the interface it defines to provide device-independent I/O features. For example, Qt's XML classes operate on a QIODevice pointer, allowing them to be used with various devices (such as files and buffers). Before accessing the device, open() must be called to set the correct OpenMode (such as ReadOnly or ReadWrite). You can then write to the device with write() or putChar(), and read by calling either read(), readLine(), or readAll(). Call close() when you are done with the device. QIODevice distinguishes between two types of devices: random-access devices and sequential devices. \list \li Random-access devices support seeking to arbitrary positions using seek(). The current position in the file is available by calling pos(). QFile and QBuffer are examples of random-access devices. \li Sequential devices don't support seeking to arbitrary positions. The data must be read in one pass. The functions pos() and size() don't work for sequential devices. QTcpSocket and QProcess are examples of sequential devices. \endlist You can use isSequential() to determine the type of device. QIODevice emits readyRead() when new data is available for reading; for example, if new data has arrived on the network or if additional data is appended to a file that you are reading from. You can call bytesAvailable() to determine the number of bytes that are currently available for reading. It's common to use bytesAvailable() together with the readyRead() signal when programming with asynchronous devices such as QTcpSocket, where fragments of data can arrive at arbitrary points in time. QIODevice emits the bytesWritten() signal every time a payload of data has been written to the device. Use bytesToWrite() to determine the current amount of data waiting to be written. Certain subclasses of QIODevice, such as QTcpSocket and QProcess, are asynchronous. This means that I/O functions such as write() or read() always return immediately, while communication with the device itself may happen when control goes back to the event loop. QIODevice provides functions that allow you to force these operations to be performed immediately, while blocking the calling thread and without entering the event loop. This allows QIODevice subclasses to be used without an event loop, or in a separate thread: \list \li waitForReadyRead() - This function suspends operation in the calling thread until new data is available for reading. \li waitForBytesWritten() - This function suspends operation in the calling thread until one payload of data has been written to the device. \li waitFor....() - Subclasses of QIODevice implement blocking functions for device-specific operations. For example, QProcess has a function called \l {QProcess::}{waitForStarted()} which suspends operation in the calling thread until the process has started. \endlist Calling these functions from the main, GUI thread, may cause your user interface to freeze. Example: \snippet code/src_corelib_io_qiodevice.cpp 0 By subclassing QIODevice, you can provide the same interface to your own I/O devices. Subclasses of QIODevice are only required to implement the protected readData() and writeData() functions. QIODevice uses these functions to implement all its convenience functions, such as getChar(), readLine() and write(). QIODevice also handles access control for you, so you can safely assume that the device is opened in write mode if writeData() is called. Some subclasses, such as QFile and QTcpSocket, are implemented using a memory buffer for intermediate storing of data. This reduces the number of required device accessing calls, which are often very slow. Buffering makes functions like getChar() and putChar() fast, as they can operate on the memory buffer instead of directly on the device itself. Certain I/O operations, however, don't work well with a buffer. For example, if several users open the same device and read it character by character, they may end up reading the same data when they meant to read a separate chunk each. For this reason, QIODevice allows you to bypass any buffering by passing the Unbuffered flag to open(). When subclassing QIODevice, remember to bypass any buffer you may use when the device is open in Unbuffered mode. Usually, the incoming data stream from an asynchronous device is fragmented, and chunks of data can arrive at arbitrary points in time. To handle incomplete reads of data structures, use the transaction mechanism implemented by QIODevice. See startTransaction() and related functions for more details. Some sequential devices support communicating via multiple channels. These channels represent separate streams of data that have the property of independently sequenced delivery. Once the device is opened, you can determine the number of channels by calling the readChannelCount() and writeChannelCount() functions. To switch between channels, call setCurrentReadChannel() and setCurrentWriteChannel(), respectively. QIODevice also provides additional signals to handle asynchronous communication on a per-channel basis. \sa QBuffer, QFile, QTcpSocket*//*! \class QIODeviceBase \inheaderfile QIODevice \inmodule QtCore \brief Base class for QIODevice that provides flags describing the mode in which a device is opened.*//*! \enum QIODeviceBase::OpenModeFlag This enum is used with QIODevice::open() to describe the mode in which a device is opened. It is also returned by QIODevice::openMode(). \value NotOpen The device is not open. \value ReadOnly The device is open for reading. \value WriteOnly The device is open for writing. Note that, for file-system subclasses (e.g. QFile), this mode implies Truncate unless combined with ReadOnly, Append or NewOnly. \value ReadWrite The device is open for reading and writing. \value Append The device is opened in append mode so that all data is written to the end of the file. \value Truncate If possible, the device is truncated before it is opened. All earlier contents of the device are lost. \value Text When reading, the end-of-line terminators are translated to '\\n'. When writing, the end-of-line terminators are translated to the local encoding, for example '\\r\\n' for Win32. \value Unbuffered Any buffer in the device is bypassed. \value NewOnly Fail if the file to be opened already exists. Create and open the file only if it does not exist. There is a guarantee from the operating system that you are the only one creating and opening the file. Note that this mode implies WriteOnly, and combining it with ReadWrite is allowed. This flag currently only affects QFile. Other classes might use this flag in the future, but until then using this flag with any classes other than QFile may result in undefined behavior. (since Qt 5.11) \value ExistingOnly Fail if the file to be opened does not exist. This flag must be specified alongside ReadOnly, WriteOnly, or ReadWrite. Note that using this flag with ReadOnly alone is redundant, as ReadOnly already fails when the file does not exist. This flag currently only affects QFile. Other classes might use this flag in the future, but until then using this flag with any classes other than QFile may result in undefined behavior. (since Qt 5.11) Certain flags, such as \c Unbuffered and \c Truncate, are meaningless when used with some subclasses. Some of these restrictions are implied by the type of device that is represented by a subclass. In other cases, the restriction may be due to the implementation, or may be imposed by the underlying platform; for example, QTcpSocket does not support \c Unbuffered mode, and limitations in the native API prevent QFile from supporting \c Unbuffered on Windows.*//*! \fn QIODevice::bytesWritten(qint64 bytes) This signal is emitted every time a payload of data has been written to the device's current write channel. The \a bytes argument is set to the number of bytes that were written in this payload. bytesWritten() is not emitted recursively; if you reenter the event loop or call waitForBytesWritten() inside a slot connected to the bytesWritten() signal, the signal will not be reemitted (although waitForBytesWritten() may still return true). \sa readyRead()*//*! \fn QIODevice::channelBytesWritten(int channel, qint64 bytes) \since 5.7 This signal is emitted every time a payload of data has been written to the device. The \a bytes argument is set to the number of bytes that were written in this payload, while \a channel is the channel they were written to. Unlike bytesWritten(), it is emitted regardless of the \l{currentWriteChannel()}{current write channel}. channelBytesWritten() can be emitted recursively - even for the same channel. \sa bytesWritten(), channelReadyRead()*//*! \fn QIODevice::readyRead() This signal is emitted once every time new data is available for reading from the device's current read channel. It will only be emitted again once new data is available, such as when a new payload of network data has arrived on your network socket, or when a new block of data has been appended to your device. readyRead() is not emitted recursively; if you reenter the event loop or call waitForReadyRead() inside a slot connected to the readyRead() signal, the signal will not be reemitted (although waitForReadyRead() may still return true). Note for developers implementing classes derived from QIODevice: you should always emit readyRead() when new data has arrived (do not emit it only because there's data still to be read in your buffers). Do not emit readyRead() in other conditions. \sa bytesWritten()*//*! \fn QIODevice::channelReadyRead(int channel) \since 5.7 This signal is emitted when new data is available for reading from the device. The \a channel argument is set to the index of the read channel on which the data has arrived. Unlike readyRead(), it is emitted regardless of the \l{currentReadChannel()}{current read channel}. channelReadyRead() can be emitted recursively - even for the same channel. \sa readyRead(), channelBytesWritten()*//*! \fn QIODevice::aboutToClose() This signal is emitted when the device is about to close. Connect this signal if you have operations that need to be performed before the device closes (e.g., if you have data in a separate buffer that needs to be written to the device).*//*! \fn QIODevice::readChannelFinished() \since 4.4 This signal is emitted when the input (reading) stream is closed in this device. It is emitted as soon as the closing is detected, which means that there might still be data available for reading with read(). \sa atEnd(), read()*/#ifdef QT_NO_QOBJECTQIODevice::QIODevice():d_ptr(new QIODevicePrivate){ d_ptr->q_ptr =this;}/*! \internal*/QIODevice::QIODevice(QIODevicePrivate &dd):d_ptr(&dd){ d_ptr->q_ptr =this;}#else/*! Constructs a QIODevice object.*/QIODevice::QIODevice():QObject(*new QIODevicePrivate,nullptr){#if defined QIODEVICE_DEBUG QFile *file = qobject_cast<QFile *>(this);printf("%p QIODevice::QIODevice(\"%s\") %s\n",this,metaObject()->className(),qPrintable(file ? file->fileName() :QString()));#endif}/*! Constructs a QIODevice object with the given \a parent.*/QIODevice::QIODevice(QObject *parent):QObject(*new QIODevicePrivate, parent){#if defined QIODEVICE_DEBUGprintf("%p QIODevice::QIODevice(%p\"%s\")\n",this, parent,metaObject()->className());#endif}/*! \internal*/QIODevice::QIODevice(QIODevicePrivate &dd, QObject *parent):QObject(dd, parent){}#endif/*! The destructor is virtual, and QIODevice is an abstract base class. This destructor does not call close(), but the subclass destructor might. If you are in doubt, call close() before destroying the QIODevice.*/QIODevice::~QIODevice(){#if defined QIODEVICE_DEBUGprintf("%p QIODevice::~QIODevice()\n",this);#endif}/*! Returns \c true if this device is sequential; otherwise returns false. Sequential devices, as opposed to a random-access devices, have no concept of a start, an end, a size, or a current position, and they do not support seeking. You can only read from the device when it reports that data is available. The most common example of a sequential device is a network socket. On Unix, special files such as /dev/zero and fifo pipes are sequential. Regular files, on the other hand, do support random access. They have both a size and a current position, and they also support seeking backwards and forwards in the data stream. Regular files are non-sequential. \sa bytesAvailable()*/boolQIODevice::isSequential()const{return false;}/*! Returns the mode in which the device has been opened; i.e. ReadOnly or WriteOnly. \sa OpenMode*/QIODeviceBase::OpenMode QIODevice::openMode()const{returnd_func()->openMode;}/*! Sets the OpenMode of the device to \a openMode. Call this function to set the open mode if the flags change after the device has been opened. \sa openMode(), OpenMode*/voidQIODevice::setOpenMode(QIODeviceBase::OpenMode openMode){Q_D(QIODevice);#if defined QIODEVICE_DEBUGprintf("%p QIODevice::setOpenMode(0x%x)\n",this, openMode.toInt());#endif d->openMode = openMode; d->accessMode =QIODevicePrivate::Unset; d->setReadChannelCount(isReadable() ?qMax(d->readChannelCount,1) :0); d->setWriteChannelCount(isWritable() ?qMax(d->writeChannelCount,1) :0);}/*! If \a enabled is true, this function sets the \l Text flag on the device; otherwise the \l Text flag is removed. This feature is useful for classes that provide custom end-of-line handling on a QIODevice. The IO device should be opened before calling this function. \sa open(), setOpenMode() */voidQIODevice::setTextModeEnabled(bool enabled){Q_D(QIODevice);if(!isOpen()) {checkWarnMessage(this,"setTextModeEnabled","The device is not open");return;}if(enabled) d->openMode |= Text;else d->openMode &= ~Text;}/*! Returns \c true if the \l Text flag is enabled; otherwise returns \c false. \sa setTextModeEnabled()*/boolQIODevice::isTextModeEnabled()const{returnd_func()->openMode.testAnyFlag(Text);}/*! Returns \c true if the device is open; otherwise returns \c false. A device is open if it can be read from and/or written to. By default, this function returns \c false if openMode() returns \c NotOpen. \sa openMode(), QIODeviceBase::OpenMode*/boolQIODevice::isOpen()const{returnd_func()->openMode != NotOpen;}/*! Returns \c true if data can be read from the device; otherwise returns false. Use bytesAvailable() to determine how many bytes can be read. This is a convenience function which checks if the OpenMode of the device contains the ReadOnly flag. \sa openMode(), OpenMode*/boolQIODevice::isReadable()const{return(openMode() & ReadOnly) !=0;}/*! Returns \c true if data can be written to the device; otherwise returns false. This is a convenience function which checks if the OpenMode of the device contains the WriteOnly flag. \sa openMode(), OpenMode*/boolQIODevice::isWritable()const{return(openMode() & WriteOnly) !=0;}/*! \since 5.7 Returns the number of available read channels if the device is open; otherwise returns 0. \sa writeChannelCount(), QProcess*/intQIODevice::readChannelCount()const{returnd_func()->readChannelCount;}/*! \since 5.7 Returns the number of available write channels if the device is open; otherwise returns 0. \sa readChannelCount()*/intQIODevice::writeChannelCount()const{returnd_func()->writeChannelCount;}/*! \since 5.7 Returns the index of the current read channel. \sa setCurrentReadChannel(), readChannelCount(), QProcess*/intQIODevice::currentReadChannel()const{returnd_func()->currentReadChannel;}/*! \since 5.7 Sets the current read channel of the QIODevice to the given \a channel. The current input channel is used by the functions read(), readAll(), readLine(), and getChar(). It also determines which channel triggers QIODevice to emit readyRead(). \sa currentReadChannel(), readChannelCount(), QProcess*/voidQIODevice::setCurrentReadChannel(int channel){Q_D(QIODevice);if(d->transactionStarted) {checkWarnMessage(this,"setReadChannel","Failed due to read transaction being in progress");return;}#if defined QIODEVICE_DEBUGqDebug("%p QIODevice::setCurrentReadChannel(%d), d->currentReadChannel = %d, d->readChannelCount = %d\n",this, channel, d->currentReadChannel, d->readChannelCount);#endif d->setCurrentReadChannel(channel);}/*! \internal*/voidQIODevicePrivate::setReadChannelCount(int count){if(count > readBuffers.size()) { readBuffers.reserve(count);// If readBufferChunkSize is zero, we should bypass QIODevice's// read buffers, even if the QIODeviceBase::Unbuffered flag is not// set when opened. However, if a read transaction is started or// ungetChar() is called, we still have to use the internal buffer.// To support these cases, pass a default value to the QRingBuffer// constructor.while(readBuffers.size() < count) readBuffers.emplace_back(readBufferChunkSize !=0? readBufferChunkSize : QIODEVICE_BUFFERSIZE);}else{ readBuffers.resize(count);} readChannelCount = count;setCurrentReadChannel(currentReadChannel);}/*! \since 5.7 Returns the index of the current write channel. \sa setCurrentWriteChannel(), writeChannelCount()*/intQIODevice::currentWriteChannel()const{returnd_func()->currentWriteChannel;}/*! \since 5.7 Sets the current write channel of the QIODevice to the given \a channel. The current output channel is used by the functions write(), putChar(). It also determines which channel triggers QIODevice to emit bytesWritten(). \sa currentWriteChannel(), writeChannelCount()*/voidQIODevice::setCurrentWriteChannel(int channel){Q_D(QIODevice);#if defined QIODEVICE_DEBUGqDebug("%p QIODevice::setCurrentWriteChannel(%d), d->currentWriteChannel = %d, d->writeChannelCount = %d\n",this, channel, d->currentWriteChannel, d->writeChannelCount);#endif d->setCurrentWriteChannel(channel);}/*! \internal*/voidQIODevicePrivate::setWriteChannelCount(int count){if(count > writeBuffers.size()) {// If writeBufferChunkSize is zero (default value), we don't use// QIODevice's write buffers.if(writeBufferChunkSize !=0) { writeBuffers.reserve(count);while(writeBuffers.size() < count) writeBuffers.emplace_back(writeBufferChunkSize);}}else{ writeBuffers.resize(count);} writeChannelCount = count;setCurrentWriteChannel(currentWriteChannel);}/*! \internal*/boolQIODevicePrivate::allWriteBuffersEmpty()const{for(const QRingBuffer &ringBuffer : writeBuffers) {if(!ringBuffer.isEmpty())return false;}return true;}/*! Opens the device and sets its OpenMode to \a mode. Returns \c true if successful; otherwise returns \c false. This function should be called from any reimplementations of open() or other functions that open the device. \sa openMode(), QIODeviceBase::OpenMode*/boolQIODevice::open(QIODeviceBase::OpenMode mode){Q_D(QIODevice); d->openMode = mode; d->pos = (mode & Append) ?size() :qint64(0); d->accessMode =QIODevicePrivate::Unset; d->readBuffers.clear(); d->writeBuffers.clear(); d->setReadChannelCount(isReadable() ?1:0); d->setWriteChannelCount(isWritable() ?1:0); d->errorString.clear();#if defined QIODEVICE_DEBUGprintf("%p QIODevice::open(0x%x)\n",this, mode.toInt());#endifreturn true;}/*! First emits aboutToClose(), then closes the device and sets its OpenMode to NotOpen. The error string is also reset. \sa setOpenMode(), QIODeviceBase::OpenMode*/voidQIODevice::close(){Q_D(QIODevice);if(d->openMode == NotOpen)return;#if defined QIODEVICE_DEBUGprintf("%p QIODevice::close()\n",this);#endif#ifndef QT_NO_QOBJECT emit aboutToClose();#endif d->openMode = NotOpen; d->pos =0; d->transactionStarted =false; d->transactionPos =0; d->setReadChannelCount(0);// Do not clear write buffers to allow delayed close in sockets d->writeChannelCount =0;}/*! For random-access devices, this function returns the position that data is written to or read from. For sequential devices or closed devices, where there is no concept of a "current position", 0 is returned. The current read/write position of the device is maintained internally by QIODevice, so reimplementing this function is not necessary. When subclassing QIODevice, use QIODevice::seek() to notify QIODevice about changes in the device position. \sa isSequential(), seek()*/ qint64 QIODevice::pos()const{Q_D(const QIODevice);#if defined QIODEVICE_DEBUGprintf("%p QIODevice::pos() == %lld\n",this, d->pos);#endifreturn d->pos;}/*! For open random-access devices, this function returns the size of the device. For open sequential devices, bytesAvailable() is returned. If the device is closed, the size returned will not reflect the actual size of the device. \sa isSequential(), pos()*/ qint64 QIODevice::size()const{returnd_func()->isSequential() ?bytesAvailable() :qint64(0);}/*! For random-access devices, this function sets the current position to \a pos, returning true on success, or false if an error occurred. For sequential devices, the default behavior is to produce a warning and return false. When subclassing QIODevice, you must call QIODevice::seek() at the start of your function to ensure integrity with QIODevice's built-in buffer. \sa pos(), isSequential()*/boolQIODevice::seek(qint64 pos){Q_D(QIODevice);if(d->isSequential()) {checkWarnMessage(this,"seek","Cannot call seek on a sequential device");return false;}if(d->openMode == NotOpen) {checkWarnMessage(this,"seek","The device is not open");return false;}if(pos <0) {qWarning("QIODevice::seek: Invalid pos: %lld", pos);return false;}#if defined QIODEVICE_DEBUGprintf("%p QIODevice::seek(%lld), before: d->pos = %lld, d->buffer.size() = %lld\n",this, pos, d->pos, d->buffer.size());#endif d->devicePos = pos; d->seekBuffer(pos);#if defined QIODEVICE_DEBUGprintf("%p\tafter: d->pos == %lld, d->buffer.size() == %lld\n",this, d->pos, d->buffer.size());#endifreturn true;}/*! \internal*/voidQIODevicePrivate::seekBuffer(qint64 newPos){const qint64 offset = newPos - pos; pos = newPos;if(offset <0|| offset >= buffer.size()) {// When seeking backwards, an operation that is only allowed for// random-access devices, the buffer is cleared. The next read// operation will then refill the buffer. buffer.clear();}else{ buffer.free(offset);}}/*! Returns \c true if the current read and write position is at the end of the device (i.e. there is no more data available for reading on the device); otherwise returns \c false. For some devices, atEnd() can return true even though there is more data to read. This special case only applies to devices that generate data in direct response to you calling read() (e.g., \c /dev or \c /proc files on Unix and \macos, or console input / \c stdin on all platforms). \sa bytesAvailable(), read(), isSequential()*/boolQIODevice::atEnd()const{Q_D(const QIODevice);const bool result = (d->openMode == NotOpen || (d->isBufferEmpty()&&bytesAvailable() ==0));#if defined QIODEVICE_DEBUGprintf("%p QIODevice::atEnd() returns %s, d->openMode == %d, d->pos == %lld\n",this, result ?"true":"false", d->openMode.toInt(), d->pos);#endifreturn result;}/*! Seeks to the start of input for random-access devices. Returns true on success; otherwise returns \c false (for example, if the device is not open). Note that when using a QTextStream on a QFile, calling reset() on the QFile will not have the expected result because QTextStream buffers the file. Use the QTextStream::seek() function instead. \sa seek()*/boolQIODevice::reset(){#if defined QIODEVICE_DEBUGprintf("%p QIODevice::reset()\n",this);#endifreturnseek(0);}/*! Returns the number of bytes that are available for reading. This function is commonly used with sequential devices to determine the number of bytes to allocate in a buffer before reading. Subclasses that reimplement this function must call the base implementation in order to include the size of the buffer of QIODevice. Example: \snippet code/src_corelib_io_qiodevice.cpp 1 \sa bytesToWrite(), readyRead(), isSequential()*/ qint64 QIODevice::bytesAvailable()const{Q_D(const QIODevice);if(!d->isSequential())returnqMax(size() - d->pos,qint64(0));return d->buffer.size() - d->transactionPos;}/*! For buffered devices, this function returns the number of bytes waiting to be written. For devices with no buffer, this function returns 0. Subclasses that reimplement this function must call the base implementation in order to include the size of the buffer of QIODevice. \sa bytesAvailable(), bytesWritten(), isSequential()*/ qint64 QIODevice::bytesToWrite()const{returnd_func()->writeBuffer.size();}/*! Reads at most \a maxSize bytes from the device into \a data, and returns the number of bytes read. If an error occurs, such as when attempting to read from a device opened in WriteOnly mode, this function returns -1. 0 is returned when no more data is available for reading. However, reading past the end of the stream is considered an error, so this function returns -1 in those cases (that is, reading on a closed socket or after a process has died). \sa readData(), readLine(), write()*/ qint64 QIODevice::read(char*data, qint64 maxSize){Q_D(QIODevice);#if defined QIODEVICE_DEBUGprintf("%p QIODevice::read(%p, %lld), d->pos = %lld, d->buffer.size() = %lld\n",this, data, maxSize, d->pos, d->buffer.size());#endifCHECK_READABLE(read,qint64(-1));const bool sequential = d->isSequential();// Short-cut for getChar(), unless we need to keep the data in the buffer.if(maxSize ==1&& !(sequential && d->transactionStarted)) {int chint;while((chint = d->buffer.getChar()) != -1) {if(!sequential)++d->pos;char c =char(uchar(chint));if(c =='\r'&& (d->openMode & Text))continue;*data = c;#if defined QIODEVICE_DEBUGprintf("%p\tread 0x%hhx (%c) returning 1 (shortcut)\n",this,int(c),isAsciiPrintable(c) ? c :'?');#endifif(d->buffer.isEmpty())readData(data,0);returnqint64(1);}}CHECK_MAXLEN(read,qint64(-1));const qint64 readBytes = d->read(data, maxSize);#if defined QIODEVICE_DEBUGprintf("%p\treturning %lld, d->pos == %lld, d->buffer.size() == %lld\n",this, readBytes, d->pos, d->buffer.size());if(readBytes >0)debugBinaryString(data - readBytes, readBytes);#endifreturn readBytes;}/*! \internal*/ qint64 QIODevicePrivate::read(char*data, qint64 maxSize,bool peeking){Q_Q(QIODevice);const bool buffered = (readBufferChunkSize !=0&& (openMode &QIODevice::Unbuffered) ==0);const bool sequential =isSequential();const bool keepDataInBuffer = sequential ? peeking || transactionStarted : peeking && buffered;const qint64 savedPos = pos; qint64 readSoFar =0;bool madeBufferReadsOnly =true;bool deviceAtEof =false;char*readPtr = data; qint64 bufferPos = (sequential && transactionStarted) ? transactionPos :Q_INT64_C(0); forever {// Try reading from the buffer. qint64 bufferReadChunkSize = keepDataInBuffer ? buffer.peek(data, maxSize, bufferPos): buffer.read(data, maxSize);if(bufferReadChunkSize >0) { bufferPos += bufferReadChunkSize;if(!sequential) pos += bufferReadChunkSize;#if defined QIODEVICE_DEBUGprintf("%p\treading %lld bytes from buffer into position %lld\n", q, bufferReadChunkSize, readSoFar);#endif readSoFar += bufferReadChunkSize; data += bufferReadChunkSize; maxSize -= bufferReadChunkSize;}if(maxSize >0&& !deviceAtEof) { qint64 readFromDevice =0;// Make sure the device is positioned correctly.if(sequential || pos == devicePos || q->seek(pos)) { madeBufferReadsOnly =false;// fix readData attemptif((!buffered || maxSize >= readBufferChunkSize) && !keepDataInBuffer) {// Read big chunk directly to output buffer readFromDevice = q->readData(data, maxSize); deviceAtEof = (readFromDevice != maxSize);#if defined QIODEVICE_DEBUGprintf("%p\treading %lld bytes from device (total %lld)\n", q, readFromDevice, readSoFar);#endifif(readFromDevice >0) { readSoFar += readFromDevice; data += readFromDevice; maxSize -= readFromDevice;if(!sequential) { pos += readFromDevice; devicePos += readFromDevice;}}}else{// Do not read more than maxSize on unbuffered devicesconst qint64 bytesToBuffer = (!buffered && maxSize < buffer.chunkSize())? maxSize :qint64(buffer.chunkSize());// Try to fill QIODevice buffer by single read readFromDevice = q->readData(buffer.reserve(bytesToBuffer), bytesToBuffer); deviceAtEof = (readFromDevice != bytesToBuffer); buffer.chop(bytesToBuffer -qMax(Q_INT64_C(0), readFromDevice));if(readFromDevice >0) {if(!sequential) devicePos += readFromDevice;#if defined QIODEVICE_DEBUGprintf("%p\treading %lld from device into buffer\n", q, readFromDevice);#endifcontinue;}}}else{ readFromDevice = -1;}if(readFromDevice <0&& readSoFar ==0) {// error and we haven't read anything: return immediatelyreturnqint64(-1);}}if((openMode &QIODevice::Text) && readPtr < data) {const char*endPtr = data;// optimization to avoid initial self-assignmentwhile(*readPtr !='\r') {if(++readPtr == endPtr)break;}char*writePtr = readPtr;while(readPtr < endPtr) {char ch = *readPtr++;if(ch !='\r')*writePtr++ = ch;else{--readSoFar;--data;++maxSize;}}// Make sure we get more data if there is room for more. This// is very important for when someone seeks to the start of a// '\r\n' and reads one character - they should get the '\n'. readPtr = data;continue;}break;}// Restore positions after readingif(keepDataInBuffer) {if(peeking) pos = savedPos;// does nothing on sequential deviceselse transactionPos = bufferPos;}else if(peeking) {seekBuffer(savedPos);// unbuffered random-access device}if(madeBufferReadsOnly &&isBufferEmpty()) q->readData(data,0);return readSoFar;}/*! \overload Reads at most \a maxSize bytes from the device, and returns the data read as a QByteArray. This function has no way of reporting errors; returning an empty QByteArray can mean either that no data was currently available for reading, or that an error occurred.*/ QByteArray QIODevice::read(qint64 maxSize){Q_D(QIODevice);#if defined QIODEVICE_DEBUGprintf("%p QIODevice::read(%lld), d->pos = %lld, d->buffer.size() = %lld\n",this, maxSize, d->pos, d->buffer.size());#endif QByteArray result;CHECK_READABLE(read, result);// Try to prevent the data from being copied, if we have a chunk// with the same size in the read buffer.if(maxSize == d->buffer.nextDataBlockSize() && !d->transactionStarted && (d->openMode &QIODevice::Text) ==0) { result = d->buffer.read();if(!d->isSequential()) d->pos += maxSize;if(d->buffer.isEmpty())readData(nullptr,0);return result;}CHECK_MAXLEN(read, result);CHECK_MAXBYTEARRAYSIZE(read); result.resize(qsizetype(maxSize)); qint64 readBytes = d->read(result.data(), result.size());if(readBytes <=0) result.clear();else result.resize(qsizetype(readBytes));return result;}/*! Reads all remaining data from the device, and returns it as a byte array. This function has no way of reporting errors; returning an empty QByteArray can mean either that no data was currently available for reading, or that an error occurred. This function also has no way of indicating that more data may have been available and couldn't be read.*/ QByteArray QIODevice::readAll(){Q_D(QIODevice);#if defined QIODEVICE_DEBUGprintf("%p QIODevice::readAll(), d->pos = %lld, d->buffer.size() = %lld\n",this, d->pos, d->buffer.size());#endif QByteArray result;CHECK_READABLE(read, result); qint64 readBytes = (d->isSequential() ?Q_INT64_C(0) :size());if(readBytes ==0) {// Size is unknown, read incrementally. qint64 readChunkSize =qMax(qint64(d->buffer.chunkSize()), d->isSequential() ? (d->buffer.size() - d->transactionPos): d->buffer.size()); qint64 readResult;do{if(readBytes + readChunkSize >=QByteArray::maxSize()) {// If resize would fail, don't read more, return what we have.break;} result.resize(readBytes + readChunkSize); readResult = d->read(result.data() + readBytes, readChunkSize);if(readResult >0|| readBytes ==0) { readBytes += readResult; readChunkSize = d->buffer.chunkSize();}}while(readResult >0);}else{// Read it all in one go. readBytes -= d->pos;if(readBytes >=QByteArray::maxSize()) readBytes =QByteArray::maxSize(); result.resize(readBytes); readBytes = d->read(result.data(), readBytes);}if(readBytes <=0) result.clear();else result.resize(qsizetype(readBytes));return result;}/*! This function reads a line of ASCII characters from the device, up to a maximum of \a maxSize - 1 bytes, stores the characters in \a data, and returns the number of bytes read. If a line could not be read but no error occurred, this function returns 0. If an error occurs, this function returns the length of what could be read, or -1 if nothing was read. A terminating '\\0' byte is always appended to \a data, so \a maxSize must be larger than 1. Data is read until either of the following conditions are met: \list \li The first '\\n' character is read. \li \a maxSize - 1 bytes are read. \li The end of the device data is detected. \endlist For example, the following code reads a line of characters from a file: \snippet code/src_corelib_io_qiodevice.cpp 2 The newline character ('\\n') is included in the buffer. If a newline is not encountered before maxSize - 1 bytes are read, a newline will not be inserted into the buffer. On windows newline characters are replaced with '\\n'. Note that on sequential devices, data may not be immediately available, which may result in a partial line being returned. By calling the canReadLine() function before reading, you can check whether a complete line (including the newline character) can be read. This function calls readLineData(), which is implemented using repeated calls to getChar(). You can provide a more efficient implementation by reimplementing readLineData() in your own subclass. \sa getChar(), read(), canReadLine(), write()*/ qint64 QIODevice::readLine(char*data, qint64 maxSize){Q_D(QIODevice);#if defined QIODEVICE_DEBUGprintf("%p QIODevice::readLine(%p, %lld), d->pos = %lld, d->buffer.size() = %lld\n",this, data, maxSize, d->pos, d->buffer.size());#endifCHECK_READABLE(readLine,qint64(-1));CHECK_LINEMAXLEN(readLine,qint64(-1));const qint64 readBytes = d->readLine(data, maxSize);#if defined QIODEVICE_DEBUGprintf("%p\treturning %lld, d->pos = %lld, d->buffer.size() = %lld, size() = %lld\n",this, readBytes, d->pos, d->buffer.size(),size());debugBinaryString(data, readBytes);#endifreturn readBytes;}/*! \internal*/ qint64 QIODevicePrivate::readLine(char*data, qint64 maxSize, ReadLineOption option){Q_Q(QIODevice);constauto appendNullByte = option &ReadLineOption::NullTerminated;if(appendNullByte) {Q_ASSERT(maxSize >=2);--maxSize;// Leave room for a '\0'}else{Q_ASSERT(maxSize >=1);}const bool sequential =isSequential();const bool keepDataInBuffer = sequential && transactionStarted; qint64 readSoFar =0;if(keepDataInBuffer) {if(transactionPos < buffer.size()) {// Peek line from the specified positionconst qint64 i = buffer.indexOf('\n', maxSize, transactionPos); readSoFar = buffer.peek(data, i >=0? (i - transactionPos +1) : maxSize, transactionPos); transactionPos += readSoFar;if(transactionPos == buffer.size()) q->readData(data,0);}}else if(!buffer.isEmpty()) {// QRingBuffer::readLine() terminates the line with '\0' if requested readSoFar = buffer.readLine(data, maxSize + (appendNullByte ?1:0), option);if(buffer.isEmpty()) q->readData(data,0);if(!sequential) pos += readSoFar;}if(readSoFar) {#if defined QIODEVICE_DEBUGprintf("%p\tread from buffer: %lld bytes, last character read: %hhx\n", q, readSoFar, data[readSoFar -1]);debugBinaryString(data, readSoFar);#endifif(data[readSoFar -1] =='\n') {if(openMode &QIODevice::Text) {// QRingBuffer::readLine() isn't Text aware.if(readSoFar >1&& data[readSoFar -2] =='\r') {--readSoFar; data[readSoFar -1] ='\n';}}if(appendNullByte) data[readSoFar] ='\0';return readSoFar;}}if(pos != devicePos && !sequential && !q->seek(pos))returnqint64(-1); baseReadLineDataCalled =false;// Force base implementation for transaction on sequential device// as it stores the data in internal buffer automatically. qint64 readBytes = keepDataInBuffer ? q->QIODevice::readLineData(data + readSoFar, maxSize - readSoFar): q->readLineData(data + readSoFar, maxSize - readSoFar);#if defined QIODEVICE_DEBUGprintf("%p\tread from readLineData: %lld bytes, readSoFar = %lld bytes\n", q, readBytes, readSoFar);if(readBytes >0) {debugBinaryString(data, readSoFar + readBytes);}#endifif(readBytes <0) {if(appendNullByte) data[readSoFar] ='\0';return readSoFar ? readSoFar : -1;} readSoFar += readBytes;if(!baseReadLineDataCalled && !sequential) { pos += readBytes;// If the base implementation was not called, then we must// assume the device position is invalid and force a seek. devicePos =qint64(-1);}if(appendNullByte) data[readSoFar] ='\0';if(openMode &QIODevice::Text) {if(readSoFar >1&& data[readSoFar -1] =='\n'&& data[readSoFar -2] =='\r') { data[readSoFar -2] ='\n';if(appendNullByte) data[readSoFar -1] ='\0';--readSoFar;}}return readSoFar;}/*! \overload Reads a line from the device, but no more than \a maxSize characters, and returns the result as a byte array. If \a maxSize is 0 or not specified, the line can be of any length, thereby enabling unlimited reading. The resulting line can have trailing end-of-line characters ("\n" or "\r\n"), so calling QByteArray::trimmed() may be necessary. This function has no way of reporting errors; returning an empty QByteArray can mean either that no data was currently available for reading, or that an error occurred.*/ QByteArray QIODevice::readLine(qint64 maxSize){ QByteArray result;if(!readLineInto(&result, maxSize) && !result.isNull()) result =QByteArray();return result;}/*! \since 6.9 Reads a line from the device, but no more than \a maxSize characters. and stores it as a byte array in \a line. \note Reads a line from this device even if \a line is \nullptr. If \a maxSize is 0 or not specified, the line can be of any length, thereby enabling unlimited reading. The resulting line can have trailing end-of-line characters ("\n" or "\r\n"), so calling QByteArray::trimmed() may be necessary. If no data was currently available for reading, or in case an error occurred, this function returns \c{false} and sets \a line to \l{QByteArray::isEmpty()}{empty}. Otherwise it returns \c true. Note that the contents of \a line before the call are discarded in any case but its \l{QByteArray::}{capacity()} is never reduced. \sa readAll(), readLine(), QTextStream::readLineInto()*/boolQIODevice::readLineInto(QByteArray *line, qint64 maxSize){Q_D(QIODevice);#if defined QIODEVICE_DEBUGprintf("%p QIODevice::readLineInto(%lld), d->pos = %lld, d->buffer.size() = %lld\n",this, maxSize, d->pos, d->buffer.size());#endifauto emptyResultOnFailure =qScopeGuard([line] {if(line) line->resize(0);});CHECK_READABLE(readLineInto,false); qint64 readBytes =0;if(maxSize ==0) {// Size is unknown, read incrementally. maxSize =QByteArray::maxSize() -1; qint64 readResult;if(!line) { readBytes = d->skipLine();}else{do{// Leave an extra byte for the terminating null by adding + 1 line->resize(qsizetype(qMin(maxSize,1+ readBytes + d->buffer.chunkSize()))); readResult = d->readLine(line->data() + readBytes, line->size() - readBytes);if(readResult >0|| readBytes ==0) readBytes += readResult;}while(readResult == d->buffer.chunkSize()&& (*line)[qsizetype(readBytes -1)] !='\n');}}else{CHECK_LINEMAXLEN(readLineInto,false);CHECK_MAXBYTEARRAYSIZE(readLineInto);if(!line){ readBytes =skip(maxSize);}else{ line->resize(maxSize); readBytes = d->readLine(line->data(), line->size());}}if(readBytes <=0)return false;if(line) line->resize(readBytes); emptyResultOnFailure.dismiss();return true;}/*! \since 6.9 \fn QIODevice::readLineInto(QSpan<char> buffer); \fn QIODevice::readLineInto(QSpan<uchar> buffer); \fn QIODevice::readLineInto(QSpan<std::byte> buffer); Reads a line from this device into \a buffer, and returns the subset of \a buffer that contains the data read. If \a buffer's size is smaller than the length of the line, only the characters that fit within \a buffer are read and returned. In this case, calling readLineInto() again will retrieve the remainder of the line. To determine whether the entire line was read, first check if the device is atEnd(), in case the last line didn't end with a newline. If not atEnd(), verify whether the returned view ends with '\n'. Otherwise, another call to readLineInto() is required. The resulting line can have trailing end-of-line characters ("\n" or "\r\n"), so calling QByteArrayView::trimmed() may be necessary. In case an error occurred, this function returns a null QByteArrayView. Otherwise it is a sub-span of \a buffer. If no data was currently available for reading or the device is atEnd(), this function returns an empty QByteArrayView. Note that the return value is not null terminated. If you want null-termination, you can pass \c{buffer.chopped(1)} and then insert '\\0' at \c{buffer[result.size()]}. \sa readLine()*/ QByteArrayView QIODevice::readLineInto(QSpan<std::byte> buffer){Q_D(QIODevice); qint64 maxSize = buffer.size();#if defined QIODEVICE_DEBUGprintf("%p QIODevice::readLineInto(%lld), d->pos = %lld, d->buffer.size() = %lld\n",this,qlonglong(maxSize),qlonglong(d->pos),qlonglong(d->buffer.size()));#endifCHECK_READABLE(readLineInto, {});if(atEnd())return buffer.first(0);CHECK_LINEMAXLEN_1(readLineInto, {});CHECK_MAXBYTEARRAYSIZE(readLineInto);const qint64 readBytes = d->readLine(reinterpret_cast<char*>(buffer.data()), buffer.size(),QIODevicePrivate::ReadLineOption::NotNullTerminated);if(readBytes <0)return{};return buffer.first(readBytes);}/*! Reads up to \a maxSize characters into \a data and returns the number of characters read. This function is called by readLine(), and provides its base implementation, using getChar(). Buffered devices can improve the performance of readLine() by reimplementing this function. readLine() appends a '\\0' byte to \a data; readLineData() does not need to do this. If you reimplement this function, be careful to return the correct value: it should return the number of bytes read in this line, including the terminating newline, or 0 if there is no line to be read at this point. If an error occurs, it should return -1 if and only if no bytes were read. Reading past EOF is considered an error.*/ qint64 QIODevice::readLineData(char*data, qint64 maxSize){Q_D(QIODevice); qint64 readSoFar =0;char c; qint64 lastReadReturn =0; d->baseReadLineDataCalled =true;while(readSoFar < maxSize && (lastReadReturn =read(&c,1)) ==1) {*data++ = c;++readSoFar;if(c =='\n')break;}#if defined QIODEVICE_DEBUGprintf("%p QIODevice::readLineData(%p, %lld), d->pos = %lld, d->buffer.size() = %lld, ""returns %lld\n",this, data, maxSize, d->pos, d->buffer.size(), readSoFar);#endifif(lastReadReturn !=1&& readSoFar ==0)returnisSequential() ? lastReadReturn : -1;return readSoFar;}/*! Returns \c true if a complete line of data can be read from the device; otherwise returns \c false. Note that unbuffered devices, which have no way of determining what can be read, always return false. This function is often called in conjunction with the readyRead() signal. Subclasses that reimplement this function must call the base implementation in order to include the contents of the QIODevice's buffer. Example: \snippet code/src_corelib_io_qiodevice.cpp 3 \sa readyRead(), readLine()*/boolQIODevice::canReadLine()const{Q_D(const QIODevice);return d->buffer.indexOf('\n', d->buffer.size(), d->isSequential() ? d->transactionPos :Q_INT64_C(0)) >=0;}/*! \since 5.7 Starts a new read transaction on the device. Defines a restorable point within the sequence of read operations. For sequential devices, read data will be duplicated internally to allow recovery in case of incomplete reads. For random-access devices, this function saves the current position. Call commitTransaction() or rollbackTransaction() to finish the transaction. \note Nesting transactions is not supported. \sa commitTransaction(), rollbackTransaction()*/voidQIODevice::startTransaction(){Q_D(QIODevice);if(d->transactionStarted) {checkWarnMessage(this,"startTransaction","Called while transaction already in progress");return;} d->transactionPos = d->pos; d->transactionStarted =true;}/*! \since 5.7 Completes a read transaction. For sequential devices, all data recorded in the internal buffer during the transaction will be discarded. \sa startTransaction(), rollbackTransaction()*/voidQIODevice::commitTransaction(){Q_D(QIODevice);if(!d->transactionStarted) {checkWarnMessage(this,"commitTransaction","Called while no transaction in progress");return;}if(d->isSequential()) d->buffer.free(d->transactionPos); d->transactionStarted =false; d->transactionPos =0;}/*! \since 5.7 Rolls back a read transaction. Restores the input stream to the point of the startTransaction() call. This function is commonly used to rollback the transaction when an incomplete read was detected prior to committing the transaction. \sa startTransaction(), commitTransaction()*/voidQIODevice::rollbackTransaction(){Q_D(QIODevice);if(!d->transactionStarted) {checkWarnMessage(this,"rollbackTransaction","Called while no transaction in progress");return;}if(!d->isSequential()) d->seekBuffer(d->transactionPos); d->transactionStarted =false; d->transactionPos =0;}/*! \since 5.7 Returns \c true if a transaction is in progress on the device, otherwise \c false. \sa startTransaction()*/boolQIODevice::isTransactionStarted()const{returnd_func()->transactionStarted;}/*! Writes at most \a maxSize bytes of data from \a data to the device. Returns the number of bytes that were actually written, or -1 if an error occurred. \sa read(), writeData()*/ qint64 QIODevice::write(const char*data, qint64 maxSize){Q_D(QIODevice);CHECK_WRITABLE(write,qint64(-1));CHECK_MAXLEN(write,qint64(-1));const bool sequential = d->isSequential();// Make sure the device is positioned correctly.if(d->pos != d->devicePos && !sequential && !seek(d->pos))returnqint64(-1);#ifdef Q_OS_WINif(d->openMode & Text) {const char*endOfData = data + maxSize;const char*startOfBlock = data; qint64 writtenSoFar =0;const qint64 savedPos = d->pos; forever {const char*endOfBlock = startOfBlock;while(endOfBlock < endOfData && *endOfBlock !='\n')++endOfBlock; qint64 blockSize = endOfBlock - startOfBlock;if(blockSize >0) { qint64 ret =writeData(startOfBlock, blockSize);if(ret <=0) {if(writtenSoFar && !sequential) d->buffer.skip(d->pos - savedPos);return writtenSoFar ? writtenSoFar : ret;}if(!sequential) { d->pos += ret; d->devicePos += ret;} writtenSoFar += ret;}if(endOfBlock == endOfData)break; qint64 ret =writeData("\r\n",2);if(ret <=0) {if(writtenSoFar && !sequential) d->buffer.skip(d->pos - savedPos);return writtenSoFar ? writtenSoFar : ret;}if(!sequential) { d->pos += ret; d->devicePos += ret;}++writtenSoFar; startOfBlock = endOfBlock +1;}if(writtenSoFar && !sequential) d->buffer.skip(d->pos - savedPos);return writtenSoFar;}#endif qint64 written =writeData(data, maxSize);if(!sequential && written >0) { d->pos += written; d->devicePos += written; d->buffer.skip(written);}return written;}/*! \since 4.5 \overload Writes data from a zero-terminated string of 8-bit characters to the device. Returns the number of bytes that were actually written, or -1 if an error occurred. This is equivalent to \code ... QIODevice::write(data, qstrlen(data)); ... \endcode \sa read(), writeData()*/ qint64 QIODevice::write(const char*data){returnwrite(data,qstrlen(data));}/*! \overload Writes the content of \a data to the device. Returns the number of bytes that were actually written, or -1 if an error occurred. \sa read(), writeData()*/ qint64 QIODevice::write(const QByteArray &data){Q_D(QIODevice);// Keep the chunk pointer for further processing in// QIODevicePrivate::write(). To reduce fragmentation,// the chunk size must be sufficiently large.if(data.size() >= QRINGBUFFER_CHUNKSIZE) d->currentWriteChunk = &data;const qint64 ret =write(data.constData(), data.size()); d->currentWriteChunk =nullptr;return ret;}/*! \internal*/voidQIODevicePrivate::write(const char*data, qint64 size){if(isWriteChunkCached(data, size)) {// We are called from write(const QByteArray &) overload.// So, we can make a shallow copy of chunk. writeBuffer.append(*currentWriteChunk);}else{ writeBuffer.append(data, size);}}/*! Puts the character \a c back into the device, and decrements the current position unless the position is 0. This function is usually called to "undo" a getChar() operation, such as when writing a backtracking parser. If \a c was not previously read from the device, the behavior is undefined. \note This function is not available while a transaction is in progress.*/voidQIODevice::ungetChar(char c){Q_D(QIODevice);CHECK_READABLE(read, Q_VOID);if(d->transactionStarted) {checkWarnMessage(this,"ungetChar","Called while transaction is in progress");return;}#if defined QIODEVICE_DEBUGprintf("%p QIODevice::ungetChar(0x%hhx '%c')\n",this, c,isAsciiPrintable(c) ? c :'?');#endif d->buffer.ungetChar(c);if(!d->isSequential())--d->pos;}/*! \fn bool QIODevice::putChar(char c) Writes the character \a c to the device. Returns \c true on success; otherwise returns \c false. \sa write(), getChar(), ungetChar()*/boolQIODevice::putChar(char c){returnd_func()->putCharHelper(c);}/*! \internal*/boolQIODevicePrivate::putCharHelper(char c){returnq_func()->write(&c,1) ==1;}/*! \internal*/ qint64 QIODevicePrivate::peek(char*data, qint64 maxSize){returnread(data, maxSize,true);}/*! \internal*/ QByteArray QIODevicePrivate::peek(qint64 maxSize){ QByteArray result(maxSize,Qt::Uninitialized);const qint64 readBytes =read(result.data(), maxSize,true);if(readBytes < maxSize) {if(readBytes <=0) result.clear();else result.resize(readBytes);}return result;}/*! \fn bool QIODevice::getChar(char *c) Reads one character from the device and stores it in \a c. If \a c is \nullptr, the character is discarded. Returns \c true on success; otherwise returns \c false. \sa read(), putChar(), ungetChar()*/boolQIODevice::getChar(char*c){// readability checked in read()char ch;return(1==read(c ? c : &ch,1));}/*! \since 4.1 Reads at most \a maxSize bytes from the device into \a data, without side effects (i.e., if you call read() after peek(), you will get the same data). Returns the number of bytes read. If an error occurs, such as when attempting to peek a device opened in WriteOnly mode, this function returns -1. 0 is returned when no more data is available for reading. Example: \snippet code/src_corelib_io_qiodevice.cpp 4 \sa read()*/ qint64 QIODevice::peek(char*data, qint64 maxSize){Q_D(QIODevice);CHECK_MAXLEN(peek,qint64(-1));CHECK_READABLE(peek,qint64(-1));return d->peek(data, maxSize);}/*! \since 4.1 \overload Peeks at most \a maxSize bytes from the device, returning the data peeked as a QByteArray. Example: \snippet code/src_corelib_io_qiodevice.cpp 5 This function has no way of reporting errors; returning an empty QByteArray can mean either that no data was currently available for peeking, or that an error occurred. \sa read()*/ QByteArray QIODevice::peek(qint64 maxSize){Q_D(QIODevice);CHECK_MAXLEN(peek,QByteArray());CHECK_MAXBYTEARRAYSIZE(peek);CHECK_READABLE(peek,QByteArray());return d->peek(maxSize);}/*! \since 5.10 Skips up to \a maxSize bytes from the device. Returns the number of bytes actually skipped, or -1 on error. This function does not wait and only discards the data that is already available for reading. If the device is opened in text mode, end-of-line terminators are translated to '\n' symbols and count as a single byte identically to the read() and peek() behavior. This function works for all devices, including sequential ones that cannot seek(). It is optimized to skip unwanted data after a peek() call. For random-access devices, skip() can be used to seek forward from the current position. Negative \a maxSize values are not allowed. \sa skipData(), peek(), seek(), read()*/ qint64 QIODevice::skip(qint64 maxSize){Q_D(QIODevice);CHECK_MAXLEN(skip,qint64(-1));CHECK_READABLE(skip,qint64(-1));const bool sequential = d->isSequential();#if defined QIODEVICE_DEBUGprintf("%p QIODevice::skip(%lld), d->pos = %lld, d->buffer.size() = %lld\n",this, maxSize, d->pos, d->buffer.size());#endifif((sequential && d->transactionStarted) || (d->openMode &QIODevice::Text) !=0)return d->skipByReading(maxSize);// First, skip over any data in the internal buffer. qint64 skippedSoFar =0;if(!d->buffer.isEmpty()) { skippedSoFar = d->buffer.skip(maxSize);#if defined QIODEVICE_DEBUGprintf("%p\tskipping %lld bytes in buffer\n",this, skippedSoFar);#endifif(!sequential) d->pos += skippedSoFar;if(d->buffer.isEmpty())readData(nullptr,0);if(skippedSoFar == maxSize)return skippedSoFar; maxSize -= skippedSoFar;}// Try to seek on random-access device. At this point,// the internal read buffer is empty.if(!sequential) {const qint64 bytesToSkip =qMin(size() - d->pos, maxSize);// If the size is unknown or file position is at the end,// fall back to reading below.if(bytesToSkip >0) {if(!seek(d->pos + bytesToSkip))return skippedSoFar ? skippedSoFar :Q_INT64_C(-1);if(bytesToSkip == maxSize)return skippedSoFar + bytesToSkip; skippedSoFar += bytesToSkip; maxSize -= bytesToSkip;}}const qint64 skipResult =skipData(maxSize);if(skippedSoFar ==0)return skipResult;if(skipResult == -1)return skippedSoFar;return skippedSoFar + skipResult;}/*! \internal*/ qint64 QIODevicePrivate::skipByReading(qint64 maxSize){ qint64 readSoFar =0;do{char dummy[4096];const qint64 readBytes = qMin<qint64>(maxSize,sizeof(dummy));const qint64 readResult =read(dummy, readBytes);// Do not try again, if we got less data.if(readResult != readBytes) {if(readSoFar ==0)return readResult;if(readResult == -1)return readSoFar;return readSoFar + readResult;} readSoFar += readResult; maxSize -= readResult;}while(maxSize >0);return readSoFar;}/*! \internal \since 6.9 Reads to the end of the line without storing its content. Returns the number of bytes read from the current line including the '\n' byte. If an error occurs, -1 is returned. This happens when no bytes were read or when trying to read past EOF. \sa readLineData(), skip()*/ qint64 QIODevicePrivate::skipLine(){char c; qint64 readSoFar =0; qint64 lastReadReturn =0;while((lastReadReturn =read(&c,1)) ==1) {++readSoFar;if(c =='\n')break;}#if defined QIODEVICE_DEBUGprintf("%p QIODevicePrivate::skipLine(), pos = %lld, buffer.size() = %lld, ""returns %lld\n",this, pos, buffer.size(), readSoFar);#endifif(lastReadReturn !=1&& readSoFar ==0)returnisSequential() ? lastReadReturn : -1;return readSoFar;}/*! \since 6.0 Skips up to \a maxSize bytes from the device. Returns the number of bytes actually skipped, or -1 on error. This function is called by QIODevice. Consider reimplementing it when creating a subclass of QIODevice. The base implementation discards the data by reading into a dummy buffer. This is slow, but works for all types of devices. Subclasses can reimplement this function to improve on that. \sa skip(), peek(), seek(), read()*/ qint64 QIODevice::skipData(qint64 maxSize){returnd_func()->skipByReading(maxSize);}/*! Blocks until new data is available for reading and the readyRead() signal has been emitted, or until \a msecs milliseconds have passed. If msecs is -1, this function will not time out. Returns \c true if new data is available for reading; otherwise returns false (if the operation timed out or if an error occurred). This function can operate without an event loop. It is useful when writing non-GUI applications and when performing I/O operations in a non-GUI thread. If called from within a slot connected to the readyRead() signal, readyRead() will not be reemitted. Reimplement this function to provide a blocking API for a custom device. The default implementation does nothing, and returns \c false. \warning Calling this function from the main (GUI) thread might cause your user interface to freeze. \sa waitForBytesWritten()*/boolQIODevice::waitForReadyRead(int msecs){Q_UNUSED(msecs);return false;}/*! For buffered devices, this function waits until a payload of buffered written data has been written to the device and the bytesWritten() signal has been emitted, or until \a msecs milliseconds have passed. If msecs is -1, this function will not time out. For unbuffered devices, it returns immediately. Returns \c true if a payload of data was written to the device; otherwise returns \c false (i.e. if the operation timed out, or if an error occurred). This function can operate without an event loop. It is useful when writing non-GUI applications and when performing I/O operations in a non-GUI thread. If called from within a slot connected to the bytesWritten() signal, bytesWritten() will not be reemitted. Reimplement this function to provide a blocking API for a custom device. The default implementation does nothing, and returns \c false. \warning Calling this function from the main (GUI) thread might cause your user interface to freeze. \sa waitForReadyRead()*/boolQIODevice::waitForBytesWritten(int msecs){Q_UNUSED(msecs);return false;}/*! Sets the human readable description of the last device error that occurred to \a str. \sa errorString()*/voidQIODevice::setErrorString(const QString &str){d_func()->errorString = str;}/*! Returns a human-readable description of the last device error that occurred. \sa setErrorString()*/ QString QIODevice::errorString()const{Q_D(const QIODevice);if(d->errorString.isEmpty()) {#ifdef QT_NO_QOBJECTreturnQLatin1StringView(QT_TRANSLATE_NOOP(QIODevice,"Unknown error"));#elsereturntr("Unknown error");#endif}return d->errorString;}/*! \fn qint64 QIODevice::readData(char *data, qint64 maxSize) Reads up to \a maxSize bytes from the device into \a data, and returns the number of bytes read or -1 if an error occurred. If there are no bytes to be read and there can never be more bytes available (examples include socket closed, pipe closed, sub-process finished), this function returns -1. This function is called by QIODevice. Reimplement this function when creating a subclass of QIODevice. When reimplementing this function it is important that this function reads all the required data before returning. This is required in order for QDataStream to be able to operate on the class. QDataStream assumes all the requested information was read and therefore does not retry reading if there was a problem. This function might be called with a maxSize of 0, which can be used to perform post-reading operations. \sa read(), readLine(), writeData()*//*! \fn qint64 QIODevice::writeData(const char *data, qint64 maxSize) Writes up to \a maxSize bytes from \a data to the device. Returns the number of bytes written, or -1 if an error occurred. This function is called by QIODevice. Reimplement this function when creating a subclass of QIODevice. When reimplementing this function it is important that this function writes all the data available before returning. This is required in order for QDataStream to be able to operate on the class. QDataStream assumes all the information was written and therefore does not retry writing if there was a problem. \sa read(), write()*//*! \internal \fn int qt_subtract_from_timeout(int timeout, int elapsed) Reduces the \a timeout by \a elapsed, taking into account that -1 is a special value for timeouts.*/intqt_subtract_from_timeout(int timeout,int elapsed){if(timeout == -1)return-1; timeout = timeout - elapsed;return timeout <0?0: timeout;}#if !defined(QT_NO_DEBUG_STREAM) QDebug operator<<(QDebug debug,QIODevice::OpenMode modes){ debug <<"OpenMode("; QStringList modeList;if(modes ==QIODevice::NotOpen) { modeList <<"NotOpen"_L1;}else{if(modes &QIODevice::ReadOnly) modeList <<"ReadOnly"_L1;if(modes &QIODevice::WriteOnly) modeList <<"WriteOnly"_L1;if(modes &QIODevice::Append) modeList <<"Append"_L1;if(modes &QIODevice::Truncate) modeList <<"Truncate"_L1;if(modes &QIODevice::Text) modeList <<"Text"_L1;if(modes &QIODevice::Unbuffered) modeList <<"Unbuffered"_L1;}std::sort(modeList.begin(), modeList.end()); debug << modeList.join(u'|'); debug <<')';return debug;}#endif QT_END_NAMESPACE #ifndef QT_NO_QOBJECT#include"moc_qiodevice.cpp"#endif