qiodevice.cpp

奇趣公司比较新的qt/emd版本

    d_func()->openMode = openMode;
    d_func()->accessMode = QIODevicePrivate::Unset;
}

/*!
    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.

    \sa open(), setOpenMode()
 */
void QIODevice::setTextModeEnabled(bool enabled)
{
    Q_D(QIODevice);
    if (enabled)
        d->openMode |= Text;
    else
        d->openMode &= ~Text;
}

/*!
    Returns true if the \l Text flag is enabled; otherwise returns false.

    \sa setTextModeEnabled()
*/
bool QIODevice::isTextModeEnabled() const
{
    return d_func()->openMode & Text;
}

/*!
    Returns true if the device is open; otherwise returns false. A
    device is open if it can be read from and/or written to. By
    default, this function returns false if openMode() returns
    \c NotOpen.

    \sa openMode() OpenMode
*/
bool QIODevice::isOpen() const
{
    return d_func()->openMode != NotOpen;
}

/*!
    Returns 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
*/
bool QIODevice::isReadable() const
{
    return (openMode() & ReadOnly) != 0;
}

/*!
    Returns 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
*/
bool QIODevice::isWritable() const
{
    return (openMode() & WriteOnly) != 0;
}

/*!
    Opens the device and sets its OpenMode to \a mode. Returns true if successful;
    otherwise returns false.

    \sa openMode() OpenMode
*/
bool QIODevice::open(OpenMode mode)
{
    Q_D(QIODevice);
    d->openMode = mode;
    d->pos = (mode & Append) ? size() : qint64(0);
    d_func()->accessMode = QIODevicePrivate::Unset;
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::open(0x%x)\n", this, quint32(mode));
#endif
    return true;
}

/*!
    First emits aboutToClose(), then closes the device and sets its
    OpenMode to NotOpen. The error string is also reset.

    \sa setOpenMode() OpenMode
*/
void QIODevice::close()
{
    Q_D(QIODevice);
    if (d->openMode == NotOpen)
        return;

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::close()\n", this);
#endif

#ifndef QT_NO_QOBJECT
    emit aboutToClose();
#endif
    d->openMode = NotOpen;
    d->errorString.clear();
    d->pos = 0;
    d->buffer.clear();
}

/*!
    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_DEBUG
    printf("%p QIODevice::pos() == %d\n", this, int(d->pos));
#endif
    return 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
{
    return d_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 do nothing 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. The base implementation always returns true.

    \sa pos(), isSequential()
*/
bool QIODevice::seek(qint64 pos)
{
    if (d_func()->openMode == NotOpen) {
        qWarning("QIODevice::seek: The device is not open");
        return false;
    }
    if (pos < 0) {
        qWarning("QIODevice::seek: Invalid pos: %d", int(pos));
        return false;
    }

    Q_D(QIODevice);
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::seek(%d), before: d->pos = %d, d->buffer.size() = %d\n",
           this, int(pos), int(d->pos), d->buffer.size());
#endif

    qint64 offset = pos - d->pos;
    if (!d->isSequential()) {
        d->pos = pos;
        d->devicePos = pos;
    }

    if (offset > 0 && !d->buffer.isEmpty()) {
        // When seeking forwards, we need to pop bytes off the front of the
        // buffer.
        do {
            int bytesToSkip = int(qMin<qint64>(offset, INT_MAX));
            d->buffer.skip(bytesToSkip);
            offset -= bytesToSkip;
        } while (offset > 0);
    } else if (offset < 0) {
        // 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. We can optimize this, if we
        // find that seeking backwards becomes a significant performance hit.
        d->buffer.clear();
    }
#if defined QIODEVICE_DEBUG
    printf("%p \tafter: d->pos == %d, d->buffer.size() == %d\n", this, int(d->pos),
           d->buffer.size());
#endif
    return true;
}

/*!
    Returns 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 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 Mac OS X, or console input / \c stdin on all platforms).

    \sa bytesAvailable(), read(), isSequential()
*/
bool QIODevice::atEnd() const
{
    Q_D(const QIODevice);
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::atEnd() returns %s, d->openMode == %d, d->pos == %d\n", this, (d->openMode == NotOpen || d->pos == size()) ? "true" : "false",
           int(d->openMode), int(d->pos));
#endif
    return d->openMode == NotOpen || (d->buffer.isEmpty() && bytesAvailable() == 0);
}

/*!
    Seeks to the start of input for random-access devices. Returns
    true on success; otherwise returns 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()
*/
bool QIODevice::reset()
{
#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::reset()\n", this);
#endif
    return seek(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 QIODevices' buffer. Example:

    \code
        qint64 CustomDevice::bytesAvailable() const
        {
            return buffer.size() + QIODevice::bytesAvailable();
        }
    \endcode

    \sa bytesToWrite(), readyRead(), isSequential()
*/
qint64 QIODevice::bytesAvailable() const
{
    Q_D(const QIODevice);
    if (!d->isSequential())
        return qMax(size() - d->pos, qint64(0));
    return d->buffer.size();
}

/*!
    For buffered devices, this function returns the number of bytes
    waiting to be written. For devices with no buffer, this function
    returns 0.

    \sa bytesAvailable(), bytesWritten(), isSequential()
*/
qint64 QIODevice::bytesToWrite() const
{
    return qint64(0);
}

/*!
    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.

    \sa readData() readLine() write()
*/
qint64 QIODevice::read(char *data, qint64 maxSize)
{
    Q_D(QIODevice);
    CHECK_READABLE(read, qint64(-1));
    CHECK_MAXLEN(read, qint64(-1));

#if defined QIODEVICE_DEBUG
    printf("%p QIODevice::read(%p, %d), d->pos = %d, d->buffer.size() = %d\n",
           this, data, int(maxSize), int(d->pos), int(d->buffer.size()));
#endif
    const bool sequential = d->isSequential();

    // Short circuit for getChar()
    if (maxSize == 1) {
        int chint = d->buffer.getChar();
        if (chint != -1) {
            char c = char(uchar(chint));
            if (c == '\r' && (d->openMode & Text)) {
                d->buffer.ungetChar(c);
            } else {
                if (data)
                    *data = c;
                if (!sequential)
                    ++d->pos;
#if defined QIODEVICE_DEBUG
                printf("%p \tread 0x%hhx (%c) returning 1 (shortcut)\n", this,
                       int(c), isprint(c) ? c : '?');
#endif
                return qint64(1);
            }
        }
    }

    qint64 readSoFar = 0;
    bool moreToRead = true;
    do {
        int lastReadChunkSize = 0;

        // Try reading from the buffer.
        if (!d->buffer.isEmpty()) {
            lastReadChunkSize = d->buffer.read(data + readSoFar, maxSize - readSoFar);
            readSoFar += lastReadChunkSize;
            if (!sequential)
                d->pos += lastReadChunkSize;
#if defined QIODEVICE_DEBUG
            printf("%p \treading %d bytes from buffer into position %d\n", this, lastReadChunkSize,
                   int(readSoFar) - lastReadChunkSize);
#endif
        } else if ((d->openMode & Unbuffered) == 0 && maxSize < QIODEVICE_BUFFERSIZE) {
            // In buffered mode, we try to fill up the QIODevice buffer before
            // we do anything else.
            int bytesToBuffer = qMax(maxSize - readSoFar, QIODEVICE_BUFFERSIZE);
            char *writePointer = d->buffer.reserve(bytesToBuffer);

            // Make sure the device is positioned correctly.
            if (d->pos != d->devicePos && !sequential && !seek(d->pos))
                return qint64(-1);
            qint64 readFromDevice = readData(writePointer, bytesToBuffer);
            d->buffer.chop(bytesToBuffer - (readFromDevice < 0 ? 0 : int(readFromDevice)));

            if (readFromDevice > 0) {
                if (!sequential)
                    d->devicePos += readFromDevice;
#if defined QIODEVICE_DEBUG
                printf("%p \treading %d from device into buffer\n", this, int(readFromDevice));
#endif

                if (readFromDevice < bytesToBuffer)
                    d->buffer.truncate(readFromDevice < 0 ? 0 : int(readFromDevice));
                if (!d->buffer.isEmpty()) {
                    lastReadChunkSize = d->buffer.read(data + readSoFar, maxSize - readSoFar);
                    readSoFar += lastReadChunkSize;
                    if (!sequential)
                        d->pos += lastReadChunkSize;
#if defined QIODEVICE_DEBUG
                    printf("%p \treading %d bytes from buffer at position %d\n", this,
                           lastReadChunkSize, int(readSoFar));
#endif
                }
            }
        }

        // If we need more, try reading from the device.
        if (readSoFar < maxSize) {
            // Make sure the device is positioned correctly.
            if (d->pos != d->devicePos && !sequential && !seek(d->pos))
                return qint64(-1);
            qint64 readFromDevice = readData(data + readSoFar, maxSize - readSoFar);
#if defined QIODEVICE_DEBUG
            printf("%p \treading %d bytes from device\n", this, int(readFromDevice));
#endif
            if (readFromDevice <= 0) {
                moreToRead = false;
            } else {
                // see if we read as much data as we asked for
                if (readFromDevice < maxSize - readSoFar)
                    moreToRead = false;

                lastReadChunkSize += int(readFromDevice);
                readSoFar += readFromDevice;
                if (!sequential) {
                    d->pos += readFromDevice;
                    d->devicePos += readFromDevice;
                }
            }
        } else {
            moreToRead = false;
        }

        if (readSoFar && d->openMode & Text) {
            char *readPtr = data + readSoFar - lastReadChunkSize;
            const char *endPtr = data + readSoFar;

            if (readPtr < endPtr) {
                // optimization to avoid initial self-assignment
                while (*readPtr != '\r') {
                    if (++readPtr == endPtr)
                        return readSoFar;
                }

                char *writePtr = readPtr;

                while (readPtr < endPtr) {
                    char ch = *readPtr++;
                    if (ch != '\r')
                        *writePtr++ = ch;
                    else
                        --readSoFar;
                }

                // 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'.
                moreToRead = (readPtr != writePtr);
            }