qiopipe.cpp

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// Copyright (C) 2019 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
 
#include "qiopipe_p.h"
#include <QtCore/qmetaobject.h>
#include <QDebug>
 
QT_BEGIN_NAMESPACE
 
/*
    proxying means do *not* emit readyRead, and instead pump data
    into child pipes directly in a zero-copy fashion.
*/
QIOPipePrivate::QIOPipePrivate(QIODevice *iodevice, bool proxying)
    :  m_proxying(proxying), source(iodevice)
{
}
 
QIOPipePrivate::~QIOPipePrivate()
{
}
 
void QIOPipePrivate::initialize()
{
    const QIOPipe *parentPipe = qobject_cast<QIOPipe *>(source);
    if (parentPipe && parentPipe->d_func()->m_proxying) // with proxying parent,
        return;                                                     // don't do anything
 
    // read available data, does not emit.
    readAvailableData();
    // connect readyRead to onReadyRead
    QObjectPrivate::connect(source, &QIODevice::readyRead, this, &QIOPipePrivate::_q_onReadyRead);
}
 
bool QIOPipePrivate::readAvailableData() {
    if (!source)
        return false;
    QByteArray ba = source->readAll();
    if (ba.isEmpty())
        return false;
 
    pumpData(ba);
    return true;
}
 
void QIOPipePrivate::pumpData(const QByteArray &ba)
{
    if (m_proxying) {
        auto isNull = [](const auto &cp) { return cp == nullptr; };
        childPipes.removeIf(isNull);
        for (const auto &cp : std::as_const(childPipes))
            cp->d_func()->pushData(ba);
    } else {
        for (auto &buffer : readBuffers)
            buffer.append(ba);
    }
}
 
void QIOPipePrivate::pushData(const QByteArray &ba)
{
    Q_Q(QIOPipe);
    if (ba.isEmpty())
        return;
 
    pumpData(ba);
    if (!m_proxying)
        emit q->readyRead();
}
 
void QIOPipePrivate::_q_onReadyRead()
{
    Q_Q(QIOPipe);
    if (readAvailableData() && !m_proxying)
        emit q->readyRead();
}
 
void QIOPipePrivate::addChildPipe(QIOPipe *childPipe)
{
    if (childPipes.contains(childPipe))
        return;
    childPipes.append(childPipe);
}
 
void QIOPipePrivate::removeChildPipe(QIOPipe *childPipe)
{
    childPipes.removeOne(childPipe);
}
 
QIOPipe::QIOPipe(QIODevice *parent, Mode mode)
    : QIODevice(*new QIOPipePrivate(parent, mode == ProxyPipe), parent)
{
    this->d_func()->initialize();
    if (!parent->isOpen() && !parent->open(QIODevice::ReadOnly)) {
        qWarning() << "QIOPipe: Failed to open " << parent;
        return;
    }
    open(ReadOnly);
}
 
QIOPipe::~QIOPipe()
{
 
}
 
bool QIOPipe::open(QIODevice::OpenMode mode)
{
    if (isOpen())
        return true;
 
    static const OpenMode supportedOpenMode = ReadOnly; // Currently limit it to read only
    if (!(mode & supportedOpenMode)) {
        qFatal("Unsupported open mode");
        return false;
    }
 
    return QIODevice::open(mode);
}
 
bool QIOPipe::isSequential() const
{
    return true;
}
 
void QIOPipe::setReadChannelCount(int count)
{
    Q_D(QIOPipe);
    d->setReadChannelCount(qMax(count, 1));
}
 
void QIOPipe::addChildPipe(QIOPipe *childPipe)
{
    Q_D(QIOPipe);
    d->addChildPipe(childPipe);
}
 
/*!
    \reimp
 
    \omit
    This function does not really read anything, as we use QIODevicePrivate's
    buffer. The buffer will be read inside of QIODevice before this
    method will be called.
    See QIODevicePrivate::read, buffer.read(data, maxSize).
    \endomit
*/
qint64 QIOPipe::readData(char *data, qint64 maxlen)
{
    Q_UNUSED(data);
    Q_UNUSED(maxlen);
 
    // return 0 indicating there may be more data in the future
    // Returning -1 means no more data in the future (end of stream).
    return qint64(0);
}
 
qint64 QIOPipe::writeData(const char * /*data*/, qint64 /*len*/)
{
    qFatal("QIOPipe is a read-only device");
    return qint64(0);
}
 
QT_END_NAMESPACE
 
#include "moc_qiopipe_p.cpp"