qtbase/src/corelib/io/qwindowspipewriter.cpp

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#include "qwindowspipewriter_p.h"
#include "qiodevice_p.h"

QT_BEGIN_NAMESPACE

extern bool qt_cancelIo(HANDLE handle, OVERLAPPED *overlapped);     // from qwindowspipereader.cpp


QWindowsPipeWriter::Overlapped::Overlapped(QWindowsPipeWriter *pipeWriter)
    : pipeWriter(pipeWriter)
{
}

void QWindowsPipeWriter::Overlapped::clear()
{
    ZeroMemory(this, sizeof(OVERLAPPED));
}


QWindowsPipeWriter::QWindowsPipeWriter(HANDLE pipeWriteEnd, QObject *parent)
    : QObject(parent),
      handle(pipeWriteEnd),
      overlapped(this),
      numberOfBytesToWrite(0),
      pendingBytesWrittenValue(0),
      stopped(true),
      writeSequenceStarted(false),
      notifiedCalled(false),
      bytesWrittenPending(false),
      inBytesWritten(false)
{
    connect(this, &QWindowsPipeWriter::_q_queueBytesWritten,
            this, &QWindowsPipeWriter::emitPendingBytesWrittenValue, Qt::QueuedConnection);
}

QWindowsPipeWriter::~QWindowsPipeWriter()
{
    stop();
}

bool QWindowsPipeWriter::waitForWrite(int msecs)
{
    if (!writeSequenceStarted)
        return false;

    if (bytesWrittenPending) {
        if (!inBytesWritten)
            emitPendingBytesWrittenValue();
        return true;
    }

    if (!waitForNotification(msecs))
        return false;

    if (bytesWrittenPending) {
        if (!inBytesWritten)
            emitPendingBytesWrittenValue();
        return true;
    }

    return false;
}

qint64 QWindowsPipeWriter::bytesToWrite() const
{
    return numberOfBytesToWrite;
}

void QWindowsPipeWriter::emitPendingBytesWrittenValue()
{
    if (bytesWrittenPending) {
        bytesWrittenPending = false;
        const qint64 bytes = pendingBytesWrittenValue;
        pendingBytesWrittenValue = 0;

        inBytesWritten = true;
        emit bytesWritten(bytes);
        inBytesWritten = false;
        emit canWrite();
    }
}

void QWindowsPipeWriter::writeFileCompleted(DWORD errorCode, DWORD numberOfBytesTransfered,
                                            OVERLAPPED *overlappedBase)
{
    Overlapped *overlapped = static_cast<Overlapped *>(overlappedBase);
    overlapped->pipeWriter->notified(errorCode, numberOfBytesTransfered);
}

/*!
    \internal
    Will be called whenever the write operation completes.
 */
void QWindowsPipeWriter::notified(DWORD errorCode, DWORD numberOfBytesWritten)
{
    notifiedCalled = true;
    writeSequenceStarted = false;
    numberOfBytesToWrite = 0;

    switch (errorCode) {
    case ERROR_SUCCESS:
        break;
    case ERROR_OPERATION_ABORTED:
        if (stopped)
            break;
        // fall through
    default:
        qErrnoWarning(errorCode, "QWindowsPipeWriter: asynchronous write failed.");
        break;
    }

    // After the writer was stopped, the only reason why this function can be called is the
    // completion of a cancellation. No signals should be emitted, and no new write sequence should
    // be started in this case.
    if (stopped)
        return;

    pendingBytesWrittenValue += qint64(numberOfBytesWritten);
    if (!bytesWrittenPending) {
        bytesWrittenPending = true;
        emit _q_queueBytesWritten(QWindowsPipeWriter::QPrivateSignal());
    }
}

bool QWindowsPipeWriter::waitForNotification(int timeout)
{
    QElapsedTimer t;
    t.start();
    notifiedCalled = false;
    int msecs = timeout;
    while (SleepEx(msecs == -1 ? INFINITE : msecs, TRUE) == WAIT_IO_COMPLETION) {
        if (notifiedCalled)
            return true;

        // Some other I/O completion routine was called. Wait some more.
        msecs = qt_subtract_from_timeout(timeout, t.elapsed());
        if (!msecs)
            break;
    }
    return notifiedCalled;
}

qint64 QWindowsPipeWriter::write(const char *ptr, qint64 maxlen)
{
    if (writeSequenceStarted)
        return 0;

    overlapped.clear();
    numberOfBytesToWrite = maxlen;
    stopped = false;
    writeSequenceStarted = true;
    if (!WriteFileEx(handle, ptr, maxlen, &overlapped, &writeFileCompleted)) {
        writeSequenceStarted = false;
        qErrnoWarning("QWindowsPipeWriter::write failed.");
    }

    return maxlen;
}

void QWindowsPipeWriter::stop()
{
    stopped = true;
    if (writeSequenceStarted) {
        if (!qt_cancelIo(handle, &overlapped)) {
            const DWORD dwError = GetLastError();
            if (dwError != ERROR_NOT_FOUND) {
                qErrnoWarning(dwError, "QWindowsPipeWriter: qt_cancelIo on handle %x failed.",
                              handle);
            }
        }
        waitForNotification(-1);
    }
}

QT_END_NAMESPACE