如何将 QFile 与 std::iostream 一起使用？

是否可以像 std::iostream 一样使用 QFile？我很确定那里一定有一个包装纸。问题是在哪里？

我有另一个库，它需要 std::istream 作为输入参数，但在我的程序中，此时我只有一个 QFile。

我使用以下代码提出了自己的解决方案：

#include <ios>
#include <QIODevice>

class QStdStreamBuf : public std::streambuf
{
public:
    QStdStreamBuf(QIODevice *dev) : std::streambuf(), m_dev(dev)
    {
        // Initialize get pointer.  This should be zero so that underflow is called upon first read.
        this->setg(0, 0, 0);
    }

protected:
virtual std::streamsize xsgetn(std::streambuf::char_type *str, std::streamsize n)
{
    return m_dev->read(str, n);
}

virtual std::streamsize xsputn(const std::streambuf::char_type *str, std::streamsize n)
{
    return m_dev->write(str, n);
}

virtual std::streambuf::pos_type seekoff(std::streambuf::off_type off, std::ios_base::seekdir dir, std::ios_base::openmode /*__mode*/)
{
    switch(dir)
    {
        case std::ios_base::beg:
            break;
        case std::ios_base::end:
            off = m_dev->size() - off;
            break;
        case std::ios_base::cur:
            off = m_dev->pos() + off;
            break;
    }
    if(m_dev->seek(off))
        return m_dev->pos();
    else
        return std::streambuf::pos_type(std::streambuf::off_type(-1));
}
virtual std::streambuf::pos_type seekpos(std::streambuf::pos_type off, std::ios_base::openmode /*__mode*/)
{
    if(m_dev->seek(off))
        return m_dev->pos();
    else
        return std::streambuf::pos_type(std::streambuf::off_type(-1));
}

virtual std::streambuf::int_type underflow()
{ 
    // Read enough bytes to fill the buffer.
    std::streamsize len = sgetn(m_inbuf, sizeof(m_inbuf)/sizeof(m_inbuf[0]));

    // Since the input buffer content is now valid (or is new)
    // the get pointer should be initialized (or reset).
    setg(m_inbuf, m_inbuf, m_inbuf + len);

    // If nothing was read, then the end is here.
    if(len == 0)
        return traits_type::eof();

    // Return the first character.
    return traits_type::not_eof(m_inbuf[0]);
}


private:
    static const std::streamsize BUFFER_SIZE = 1024;
    std::streambuf::char_type m_inbuf[BUFFER_SIZE];
    QIODevice *m_dev;
};

class QStdIStream : public std::istream
{
public:
    QStdIStream(QIODevice *dev) : std::istream(m_buf = new QStdStreamBuf(dev)) {}
    virtual ~QStdIStream()
    {
        rdbuf(0);
        delete m_buf;
    }

private:
    QStdStreamBuf * m_buf;
};

我可以很好地读取本地文件。我还没有测试过它的写入文件功能。这段代码肯定不完美，但它可以工作。