/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Copyright (C) 2017 Intel Corporation.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

//#define QPROCESS_DEBUG
#include "qprocess.h"
#include "qprocess_p.h"
#include "qwindowspipereader_p.h"
#include "qwindowspipewriter_p.h"

#include <qdatetime.h>
#include <qdir.h>
#include <qelapsedtimer.h>
#include <qfileinfo.h>
#include <qrandom.h>
#include <qregexp.h>
#include <qwineventnotifier.h>
#include <private/qsystemlibrary_p.h>
#include <private/qthread_p.h>
#include <qdebug.h>

#include "private/qfsfileengine_p.h" // for longFileName

#ifndef PIPE_REJECT_REMOTE_CLIENTS
#define PIPE_REJECT_REMOTE_CLIENTS 0x08
#endif

QT_BEGIN_NAMESPACE

QProcessEnvironment QProcessEnvironment::systemEnvironment()
{
    QProcessEnvironment env;
    // Calls to setenv() affect the low-level environment as well.
    // This is not the case the other way round.
    if (wchar_t *envStrings = GetEnvironmentStringsW()) {
        for (const wchar_t *entry = envStrings; *entry; ) {
            const int entryLen = int(wcslen(entry));
            // + 1 to permit magic cmd variable names starting with =
            if (const wchar_t *equal = wcschr(entry + 1, L'=')) {
                int nameLen = equal - entry;
                QString name = QString::fromWCharArray(entry, nameLen);
                QString value = QString::fromWCharArray(equal + 1, entryLen - nameLen - 1);
                env.d->vars.insert(QProcessEnvironmentPrivate::Key(name), value);
            }
            entry += entryLen + 1;
        }
        FreeEnvironmentStringsW(envStrings);
    }
    return env;
}

#if QT_CONFIG(process)

static void qt_create_pipe(Q_PIPE *pipe, bool isInputPipe)
{
    // Anomymous pipes do not support asynchronous I/O. Thus we
    // create named pipes for redirecting stdout, stderr and stdin.

    // The write handle must be non-inheritable for input pipes.
    // The read handle must be non-inheritable for output pipes.
    SECURITY_ATTRIBUTES secAtt = { sizeof(SECURITY_ATTRIBUTES), 0, false };

    HANDLE hServer;
    wchar_t pipeName[256];
    unsigned int attempts = 1000;
    forever {
        _snwprintf(pipeName, sizeof(pipeName) / sizeof(pipeName[0]),
                L"\\\\.\\pipe\\qt-%lX-%X", long(QCoreApplication::applicationPid()),
                QRandomGenerator::global()->generate());

        DWORD dwOpenMode = FILE_FLAG_OVERLAPPED;
        DWORD dwOutputBufferSize = 0;
        DWORD dwInputBufferSize = 0;
        const DWORD dwPipeBufferSize = 1024 * 1024;
        if (isInputPipe) {
            dwOpenMode |= PIPE_ACCESS_OUTBOUND;
            dwOutputBufferSize = dwPipeBufferSize;
        } else {
            dwOpenMode |= PIPE_ACCESS_INBOUND;
            dwInputBufferSize = dwPipeBufferSize;
        }
        DWORD dwPipeFlags = PIPE_TYPE_BYTE | PIPE_WAIT | PIPE_REJECT_REMOTE_CLIENTS;
        hServer = CreateNamedPipe(pipeName,
                                  dwOpenMode,
                                  dwPipeFlags,
                                  1,                      // only one pipe instance
                                  dwOutputBufferSize,
                                  dwInputBufferSize,
                                  0,
                                  &secAtt);
        if (hServer != INVALID_HANDLE_VALUE)
            break;
        DWORD dwError = GetLastError();
        if (dwError != ERROR_PIPE_BUSY || !--attempts) {
            qErrnoWarning(dwError, "QProcess: CreateNamedPipe failed.");
            return;
        }
    }

    secAtt.bInheritHandle = TRUE;
    const HANDLE hClient = CreateFile(pipeName,
                                      (isInputPipe ? (GENERIC_READ | FILE_WRITE_ATTRIBUTES)
                                                   : GENERIC_WRITE),
                                      0,
                                      &secAtt,
                                      OPEN_EXISTING,
                                      FILE_FLAG_OVERLAPPED,
                                      NULL);
    if (hClient == INVALID_HANDLE_VALUE) {
        qErrnoWarning("QProcess: CreateFile failed.");
        CloseHandle(hServer);
        return;
    }

    // Wait until connection is in place.
    OVERLAPPED overlapped;
    ZeroMemory(&overlapped, sizeof(overlapped));
    overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    if (ConnectNamedPipe(hServer, &overlapped) == 0) {
        DWORD dwError = GetLastError();
        switch (dwError) {
        case ERROR_PIPE_CONNECTED:
            break;
        case ERROR_IO_PENDING:
            WaitForSingleObject(overlapped.hEvent, INFINITE);
            break;
        default:
            qErrnoWarning(dwError, "QProcess: ConnectNamedPipe failed.");
            CloseHandle(overlapped.hEvent);
            CloseHandle(hClient);
            CloseHandle(hServer);
            return;
        }
    }
    CloseHandle(overlapped.hEvent);

    if (isInputPipe) {
        pipe[0] = hClient;
        pipe[1] = hServer;
    } else {
        pipe[0] = hServer;
        pipe[1] = hClient;
    }
}

static void duplicateStdWriteChannel(Q_PIPE *pipe, DWORD nStdHandle)
{
    pipe[0] = INVALID_Q_PIPE;
    HANDLE hStdWriteChannel = GetStdHandle(nStdHandle);
    HANDLE hCurrentProcess = GetCurrentProcess();
    DuplicateHandle(hCurrentProcess, hStdWriteChannel, hCurrentProcess,
                    &pipe[1], 0, TRUE, DUPLICATE_SAME_ACCESS);
}

/*
    Create the pipes to a QProcessPrivate::Channel.

    This function must be called in order: stdin, stdout, stderr
*/
bool QProcessPrivate::openChannel(Channel &channel)
{
    Q_Q(QProcess);

    if (&channel == &stderrChannel && processChannelMode == QProcess::MergedChannels) {
        return DuplicateHandle(GetCurrentProcess(), stdoutChannel.pipe[1], GetCurrentProcess(),
                               &stderrChannel.pipe[1], 0, TRUE, DUPLICATE_SAME_ACCESS);
    }

    switch (channel.type) {
    case Channel::Normal:
        // we're piping this channel to our own process
        if (&channel == &stdinChannel) {
            if (inputChannelMode != QProcess::ForwardedInputChannel) {
                qt_create_pipe(channel.pipe, true);
            } else {
                channel.pipe[1] = INVALID_Q_PIPE;
                HANDLE hStdReadChannel = GetStdHandle(STD_INPUT_HANDLE);
                HANDLE hCurrentProcess = GetCurrentProcess();
                DuplicateHandle(hCurrentProcess, hStdReadChannel, hCurrentProcess,
                                &channel.pipe[0], 0, TRUE, DUPLICATE_SAME_ACCESS);
            }
        } else {
            if (&channel == &stdoutChannel) {
                if (processChannelMode != QProcess::ForwardedChannels
                        && processChannelMode != QProcess::ForwardedOutputChannel) {
                    if (!stdoutChannel.reader) {
                        stdoutChannel.reader = new QWindowsPipeReader(q);
                        q->connect(stdoutChannel.reader, SIGNAL(readyRead()), SLOT(_q_canReadStandardOutput()));
                    }
                } else {
                    duplicateStdWriteChannel(channel.pipe, STD_OUTPUT_HANDLE);
                }
            } else /* if (&channel == &stderrChannel) */ {
                if (processChannelMode != QProcess::ForwardedChannels
                        && processChannelMode != QProcess::ForwardedErrorChannel) {
                    if (!stderrChannel.reader) {
                        stderrChannel.reader = new QWindowsPipeReader(q);
                        q->connect(stderrChannel.reader, SIGNAL(readyRead()), SLOT(_q_canReadStandardError()));
                    }
                } else {
                    duplicateStdWriteChannel(channel.pipe, STD_ERROR_HANDLE);
                }
            }
            if (channel.reader) {
                qt_create_pipe(channel.pipe, false);
                channel.reader->setHandle(channel.pipe[0]);
                channel.reader->startAsyncRead();
            }
        }
        return true;
    case Channel::Redirect: {
        // we're redirecting the channel to/from a file
        SECURITY_ATTRIBUTES secAtt = { sizeof(SECURITY_ATTRIBUTES), NULL, TRUE };

        if (&channel == &stdinChannel) {
            // try to open in read-only mode
            channel.pipe[1] = INVALID_Q_PIPE;
            channel.pipe[0] =
                CreateFile((const wchar_t*)QFSFileEnginePrivate::longFileName(channel.file).utf16(),
                           GENERIC_READ,
                           FILE_SHARE_READ | FILE_SHARE_WRITE,
                           &secAtt,
                           OPEN_EXISTING,
                           FILE_ATTRIBUTE_NORMAL,
                           NULL);

            if (channel.pipe[0] != INVALID_Q_PIPE)
                return true;

            setErrorAndEmit(QProcess::FailedToStart,
                            QProcess::tr("Could not open input redirection for reading"));
        } else {
            // open in write mode
            channel.pipe[0] = INVALID_Q_PIPE;
            channel.pipe[1] =
                CreateFile((const wchar_t *)QFSFileEnginePrivate::longFileName(channel.file).utf16(),
                           GENERIC_WRITE,
                           FILE_SHARE_READ | FILE_SHARE_WRITE,
                           &secAtt,
                           channel.append ? OPEN_ALWAYS : CREATE_ALWAYS,
                           FILE_ATTRIBUTE_NORMAL,
                           NULL);

            if (channel.pipe[1] != INVALID_Q_PIPE) {
                if (channel.append) {
                    SetFilePointer(channel.pipe[1], 0, NULL, FILE_END);
                }
                return true;
            }

            setErrorAndEmit(QProcess::FailedToStart,
                            QProcess::tr("Could not open output redirection for writing"));
        }
        cleanup();
        return false;
    }
    case Channel::PipeSource: {
        Q_ASSERT_X(channel.process, "QProcess::start", "Internal error");
        // we are the source
        Channel *source = &channel;
        Channel *sink = &channel.process->stdinChannel;

        if (source->pipe[1] != INVALID_Q_PIPE) {
            // already constructed by the sink
            // make it inheritable
            HANDLE tmpHandle = source->pipe[1];
            if (!DuplicateHandle(GetCurrentProcess(), tmpHandle,
                                 GetCurrentProcess(), &source->pipe[1],
                                 0, TRUE, DUPLICATE_SAME_ACCESS)) {
                return false;
            }

            CloseHandle(tmpHandle);
            return true;
        }

        Q_ASSERT(source == &stdoutChannel);
        Q_ASSERT(sink->process == this && sink->type == Channel::PipeSink);

        qt_create_pipe(source->pipe, /* in = */ false); // source is stdout
        sink->pipe[0] = source->pipe[0];
        source->pipe[0] = INVALID_Q_PIPE;

        return true;
    }
    case Channel::PipeSink: { // we are the sink;
        Q_ASSERT_X(channel.process, "QProcess::start", "Internal error");
        Channel *source = &channel.process->stdoutChannel;
        Channel *sink = &channel;

        if (sink->pipe[0] != INVALID_Q_PIPE) {
            // already constructed by the source
            // make it inheritable
            HANDLE tmpHandle = sink->pipe[0];
            if (!DuplicateHandle(GetCurrentProcess(), tmpHandle,
                                 GetCurrentProcess(), &sink->pipe[0],
                                 0, TRUE, DUPLICATE_SAME_ACCESS)) {
                return false;
            }

            CloseHandle(tmpHandle);
            return true;
        }
        Q_ASSERT(sink == &stdinChannel);
        Q_ASSERT(source->process == this && source->type == Channel::PipeSource);

        qt_create_pipe(sink->pipe, /* in = */ true); // sink is stdin
        source->pipe[1] = sink->pipe[1];
        sink->pipe[1] = INVALID_Q_PIPE;

        return true;
    }
    } // switch (channel.type)
    return false;
}

void QProcessPrivate::destroyPipe(Q_PIPE pipe[2])
{
    if (pipe[0] != INVALID_Q_PIPE) {
        CloseHandle(pipe[0]);
        pipe[0] = INVALID_Q_PIPE;
    }
    if (pipe[1] != INVALID_Q_PIPE) {
        CloseHandle(pipe[1]);
        pipe[1] = INVALID_Q_PIPE;
    }
}

template <class T>
void deleteWorker(T *&worker)
{
    if (!worker)
        return;
    worker->stop();
    worker->deleteLater();
    worker = nullptr;
}

void QProcessPrivate::closeChannel(Channel *channel)
{
    if (channel == &stdinChannel)
        deleteWorker(channel->writer);
    else
        deleteWorker(channel->reader);
    destroyPipe(channel->pipe);
}

static QString qt_create_commandline(const QString &program, const QStringList &arguments,
                                     const QString &nativeArguments)
{
    QString args;
    if (!program.isEmpty()) {
        QString programName = program;
        if (!programName.startsWith(QLatin1Char('\"')) && !programName.endsWith(QLatin1Char('\"')) && programName.contains(QLatin1Char(' ')))
            programName = QLatin1Char('\"') + programName + QLatin1Char('\"');
        programName.replace(QLatin1Char('/'), QLatin1Char('\\'));

        // add the prgram as the first arg ... it works better
        args = programName + QLatin1Char(' ');
    }

    for (int i=0; i<arguments.size(); ++i) {
        QString tmp = arguments.at(i);
        // Quotes are escaped and their preceding backslashes are doubled.
        tmp.replace(QRegExp(QLatin1String("(\\\\*)\"")), QLatin1String("\\1\\1\\\""));
        if (tmp.isEmpty() || tmp.contains(QLatin1Char(' ')) || tmp.contains(QLatin1Char('\t'))) {
            // The argument must not end with a \ since this would be interpreted
            // as escaping the quote -- rather put the \ behind the quote: e.g.
            // rather use "foo"\ than "foo\"
            int i = tmp.length();
            while (i > 0 && tmp.at(i - 1) == QLatin1Char('\\'))
                --i;
            tmp.insert(i, QLatin1Char('"'));
            tmp.prepend(QLatin1Char('"'));
        }
        args += QLatin1Char(' ') + tmp;
    }

    if (!nativeArguments.isEmpty()) {
        if (!args.isEmpty())
             args += QLatin1Char(' ');
        args += nativeArguments;
    }

    return args;
}

static QByteArray qt_create_environment(const QProcessEnvironmentPrivate::Map &environment)
{
    QByteArray envlist;
    if (!environment.isEmpty()) {
        QProcessEnvironmentPrivate::Map copy = environment;

        // add PATH if necessary (for DLL loading)
        QProcessEnvironmentPrivate::Key pathKey(QLatin1String("PATH"));
        if (!copy.contains(pathKey)) {
            QByteArray path = qgetenv("PATH");
            if (!path.isEmpty())
                copy.insert(pathKey, QString::fromLocal8Bit(path));
        }

        // add systemroot if needed
        QProcessEnvironmentPrivate::Key rootKey(QLatin1String("SystemRoot"));
        if (!copy.contains(rootKey)) {
            QByteArray systemRoot = qgetenv("SystemRoot");
            if (!systemRoot.isEmpty())
                copy.insert(rootKey, QString::fromLocal8Bit(systemRoot));
        }

        int pos = 0;
        auto it = copy.constBegin();
        const auto end = copy.constEnd();

        static const wchar_t equal = L'=';
        static const wchar_t nul = L'\0';

        for ( ; it != end; ++it) {
            uint tmpSize = sizeof(wchar_t) * (it.key().length() + it.value().length() + 2);
            // ignore empty strings
            if (tmpSize == sizeof(wchar_t) * 2)
                continue;
            envlist.resize(envlist.size() + tmpSize);

            tmpSize = it.key().length() * sizeof(wchar_t);
            memcpy(envlist.data()+pos, it.key().utf16(), tmpSize);
            pos += tmpSize;

            memcpy(envlist.data()+pos, &equal, sizeof(wchar_t));
            pos += sizeof(wchar_t);

            tmpSize = it.value().length() * sizeof(wchar_t);
            memcpy(envlist.data()+pos, it.value().utf16(), tmpSize);
            pos += tmpSize;

            memcpy(envlist.data()+pos, &nul, sizeof(wchar_t));
            pos += sizeof(wchar_t);
        }
        // add the 2 terminating 0 (actually 4, just to be on the safe side)
        envlist.resize( envlist.size()+4 );
        envlist[pos++] = 0;
        envlist[pos++] = 0;
        envlist[pos++] = 0;
        envlist[pos++] = 0;
    }
    return envlist;
}

bool QProcessPrivate::callCreateProcess(QProcess::CreateProcessArguments *cpargs)
{
    if (modifyCreateProcessArgs)
        modifyCreateProcessArgs(cpargs);
    bool success = CreateProcess(cpargs->applicationName, cpargs->arguments,
                                 cpargs->processAttributes, cpargs->threadAttributes,
                                 cpargs->inheritHandles, cpargs->flags, cpargs->environment,
                                 cpargs->currentDirectory, cpargs->startupInfo,
                                 cpargs->processInformation);
    if (stdinChannel.pipe[0] != INVALID_Q_PIPE) {
        CloseHandle(stdinChannel.pipe[0]);
        stdinChannel.pipe[0] = INVALID_Q_PIPE;
    }
    if (stdoutChannel.pipe[1] != INVALID_Q_PIPE) {
        CloseHandle(stdoutChannel.pipe[1]);
        stdoutChannel.pipe[1] = INVALID_Q_PIPE;
    }
    if (stderrChannel.pipe[1] != INVALID_Q_PIPE) {
        CloseHandle(stderrChannel.pipe[1]);
        stderrChannel.pipe[1] = INVALID_Q_PIPE;
    }
    return success;
}

void QProcessPrivate::startProcess()
{
    Q_Q(QProcess);

    bool success = false;

    if (pid) {
        CloseHandle(pid->hThread);
        CloseHandle(pid->hProcess);
        delete pid;
        pid = 0;
    }
    pid = new PROCESS_INFORMATION;
    memset(pid, 0, sizeof(PROCESS_INFORMATION));

    q->setProcessState(QProcess::Starting);

    if (!openChannel(stdinChannel) ||
        !openChannel(stdoutChannel) ||
        !openChannel(stderrChannel)) {
        QString errorString = QProcess::tr("Process failed to start: %1").arg(qt_error_string());
        cleanup();
        setErrorAndEmit(QProcess::FailedToStart, errorString);
        q->setProcessState(QProcess::NotRunning);
        return;
    }

    const QString args = qt_create_commandline(program, arguments, nativeArguments);
    QByteArray envlist;
    if (environment.d.constData())
        envlist = qt_create_environment(environment.d.constData()->vars);

#if defined QPROCESS_DEBUG
    qDebug("Creating process");
    qDebug("   program : [%s]", program.toLatin1().constData());
    qDebug("   args : %s", args.toLatin1().constData());
    qDebug("   pass environment : %s", environment.isEmpty() ? "no" : "yes");
#endif

    // We cannot unconditionally set the CREATE_NO_WINDOW flag, because this
    // will render the stdout/stderr handles connected to a console useless
    // (this typically affects ForwardedChannels mode).
    // However, we also do not want console tools launched from a GUI app to
    // create new console windows (behavior consistent with UNIX).
    DWORD dwCreationFlags = (GetConsoleWindow() ? 0 : CREATE_NO_WINDOW);
    dwCreationFlags |= CREATE_UNICODE_ENVIRONMENT;
    STARTUPINFOW startupInfo = { sizeof( STARTUPINFO ), 0, 0, 0,
                                 (ulong)CW_USEDEFAULT, (ulong)CW_USEDEFAULT,
                                 (ulong)CW_USEDEFAULT, (ulong)CW_USEDEFAULT,
                                 0, 0, 0,
                                 STARTF_USESTDHANDLES,
                                 0, 0, 0,
                                 stdinChannel.pipe[0], stdoutChannel.pipe[1], stderrChannel.pipe[1]
    };

    const QString nativeWorkingDirectory = QDir::toNativeSeparators(workingDirectory);
    QProcess::CreateProcessArguments cpargs = {
        nullptr, reinterpret_cast<wchar_t *>(const_cast<ushort *>(args.utf16())),
        nullptr, nullptr, true, dwCreationFlags,
        environment.isEmpty() ? nullptr : envlist.data(),
        nativeWorkingDirectory.isEmpty()
            ? nullptr : reinterpret_cast<const wchar_t *>(nativeWorkingDirectory.utf16()),
        &startupInfo, pid
    };
    success = callCreateProcess(&cpargs);

    QString errorString;
    if (!success) {
        // Capture the error string before we do CloseHandle below
        errorString = QProcess::tr("Process failed to start: %1").arg(qt_error_string());
    }

    if (!success) {
        cleanup();
        setErrorAndEmit(QProcess::FailedToStart, errorString);
        q->setProcessState(QProcess::NotRunning);
        return;
    }

    q->setProcessState(QProcess::Running);
    // User can call kill()/terminate() from the stateChanged() slot
    // so check before proceeding
    if (!pid)
        return;

    if (threadData->hasEventDispatcher()) {
        processFinishedNotifier = new QWinEventNotifier(pid->hProcess, q);
        QObject::connect(processFinishedNotifier, SIGNAL(activated(HANDLE)), q, SLOT(_q_processDied()));
        processFinishedNotifier->setEnabled(true);
    }

    _q_startupNotification();
}

bool QProcessPrivate::processStarted(QString * /*errorMessage*/)
{
    return processState == QProcess::Running;
}

qint64 QProcessPrivate::bytesAvailableInChannel(const Channel *channel) const
{
    Q_ASSERT(channel->pipe[0] != INVALID_Q_PIPE);
    Q_ASSERT(channel->reader);

    DWORD bytesAvail = channel->reader->bytesAvailable();
#if defined QPROCESS_DEBUG
    qDebug("QProcessPrivate::bytesAvailableInChannel(%d) == %d", channel - &stdinChannel, bytesAvail);
#endif
    return bytesAvail;
}

qint64 QProcessPrivate::readFromChannel(const Channel *channel, char *data, qint64 maxlen)
{
    Q_ASSERT(channel->pipe[0] != INVALID_Q_PIPE);
    Q_ASSERT(channel->reader);
    return channel->reader->read(data, maxlen);
}

static BOOL QT_WIN_CALLBACK qt_terminateApp(HWND hwnd, LPARAM procId)
{
    DWORD currentProcId = 0;
    GetWindowThreadProcessId(hwnd, &currentProcId);
    if (currentProcId == (DWORD)procId)
        PostMessage(hwnd, WM_CLOSE, 0, 0);

    return TRUE;
}

void QProcessPrivate::terminateProcess()
{
    if (pid) {
        EnumWindows(qt_terminateApp, (LPARAM)pid->dwProcessId);
        PostThreadMessage(pid->dwThreadId, WM_CLOSE, 0, 0);
    }
}

void QProcessPrivate::killProcess()
{
    if (pid)
        TerminateProcess(pid->hProcess, 0xf291);
}

bool QProcessPrivate::waitForStarted(int)
{
    if (processStarted())
        return true;

    if (processError == QProcess::FailedToStart)
        return false;

    setError(QProcess::Timedout);
    return false;
}

bool QProcessPrivate::drainOutputPipes()
{
    if (!stdoutChannel.reader && !stderrChannel.reader)
        return false;

    bool someReadyReadEmitted = false;
    forever {
        bool readyReadEmitted = false;
        bool readOperationActive = false;
        if (stdoutChannel.reader) {
            readyReadEmitted |= stdoutChannel.reader->waitForReadyRead(0);
            readOperationActive = stdoutChannel.reader && stdoutChannel.reader->isReadOperationActive();
        }
        if (stderrChannel.reader) {
            readyReadEmitted |= stderrChannel.reader->waitForReadyRead(0);
            readOperationActive |= stderrChannel.reader && stderrChannel.reader->isReadOperationActive();
        }
        someReadyReadEmitted |= readyReadEmitted;
        if (!readOperationActive || !readyReadEmitted)
            break;
        QThread::yieldCurrentThread();
    }

    return someReadyReadEmitted;
}

bool QProcessPrivate::waitForReadyRead(int msecs)
{
    QIncrementalSleepTimer timer(msecs);

    forever {
        if (!writeBuffer.isEmpty() && !_q_canWrite())
            return false;
        if (stdinChannel.writer && stdinChannel.writer->waitForWrite(0))
            timer.resetIncrements();

        if ((stdoutChannel.reader && stdoutChannel.reader->waitForReadyRead(0))
            || (stderrChannel.reader && stderrChannel.reader->waitForReadyRead(0)))
            return true;

        if (!pid)
            return false;
        if (WaitForSingleObjectEx(pid->hProcess, 0, false) == WAIT_OBJECT_0) {
            bool readyReadEmitted = drainOutputPipes();
            if (pid)
                _q_processDied();
            return readyReadEmitted;
        }

        Sleep(timer.nextSleepTime());
        if (timer.hasTimedOut())
            break;
    }

    setError(QProcess::Timedout);
    return false;
}

bool QProcessPrivate::waitForBytesWritten(int msecs)
{
    QIncrementalSleepTimer timer(msecs);

    forever {
        bool pendingDataInPipe = stdinChannel.writer && stdinChannel.writer->bytesToWrite();

        // If we don't have pending data, and our write buffer is
        // empty, we fail.
        if (!pendingDataInPipe && writeBuffer.isEmpty())
            return false;

        // If we don't have pending data and we do have data in our
        // write buffer, try to flush that data over to the pipe
        // writer.  Fail on error.
        if (!pendingDataInPipe) {
            if (!_q_canWrite())
                return false;
        }

        // Wait for the pipe writer to acknowledge that it has
        // written. This will succeed if either the pipe writer has
        // already written the data, or if it manages to write data
        // within the given timeout. If the write buffer was non-empty
        // and the stdinChannel.writer is now dead, that means _q_canWrite()
        // destroyed the writer after it successfully wrote the last
        // batch.
        if (!stdinChannel.writer || stdinChannel.writer->waitForWrite(0))
            return true;

        // If we wouldn't write anything, check if we can read stdout.
        if (stdoutChannel.pipe[0] != INVALID_Q_PIPE
                && bytesAvailableInChannel(&stdoutChannel) != 0) {
            tryReadFromChannel(&stdoutChannel);
            timer.resetIncrements();
        }

        // Check if we can read stderr.
        if (stderrChannel.pipe[0] != INVALID_Q_PIPE
                && bytesAvailableInChannel(&stderrChannel) != 0) {
            tryReadFromChannel(&stderrChannel);
            timer.resetIncrements();
        }

        // Check if the process died while reading.
        if (!pid)
            return false;

        // Wait for the process to signal any change in its state,
        // such as incoming data, or if the process died.
        if (WaitForSingleObjectEx(pid->hProcess, 0, false) == WAIT_OBJECT_0) {
            _q_processDied();
            return false;
        }

        // Only wait for as long as we've been asked.
        if (timer.hasTimedOut())
            break;
    }

    setError(QProcess::Timedout);
    return false;
}

bool QProcessPrivate::waitForFinished(int msecs)
{
#if defined QPROCESS_DEBUG
    qDebug("QProcessPrivate::waitForFinished(%d)", msecs);
#endif

    QIncrementalSleepTimer timer(msecs);

    forever {
        if (!writeBuffer.isEmpty() && !_q_canWrite())
            return false;
        if (stdinChannel.writer && stdinChannel.writer->waitForWrite(0))
            timer.resetIncrements();
        if (stdoutChannel.reader && stdoutChannel.reader->waitForReadyRead(0))
            timer.resetIncrements();
        if (stderrChannel.reader && stderrChannel.reader->waitForReadyRead(0))
            timer.resetIncrements();

        if (!pid) {
            drainOutputPipes();
            return true;
        }

        if (WaitForSingleObject(pid->hProcess, timer.nextSleepTime()) == WAIT_OBJECT_0) {
            drainOutputPipes();
            if (pid)
                _q_processDied();
            return true;
        }

        if (timer.hasTimedOut())
            break;
    }

    setError(QProcess::Timedout);
    return false;
}


void QProcessPrivate::findExitCode()
{
    DWORD theExitCode;
    Q_ASSERT(pid);
    if (GetExitCodeProcess(pid->hProcess, &theExitCode)) {
        exitCode = theExitCode;
        crashed = (exitCode == 0xf291   // our magic number, see killProcess
                   || (theExitCode >= 0x80000000 && theExitCode < 0xD0000000));
    }
}

void QProcessPrivate::flushPipeWriter()
{
    if (stdinChannel.writer && stdinChannel.writer->bytesToWrite() > 0)
        stdinChannel.writer->waitForWrite(ULONG_MAX);
}

qint64 QProcessPrivate::pipeWriterBytesToWrite() const
{
    return stdinChannel.writer ? stdinChannel.writer->bytesToWrite() : qint64(0);
}

bool QProcessPrivate::writeToStdin()
{
    Q_Q(QProcess);

    if (!stdinChannel.writer) {
        stdinChannel.writer = new QWindowsPipeWriter(stdinChannel.pipe[1], q);
        QObject::connect(stdinChannel.writer, &QWindowsPipeWriter::bytesWritten,
                         q, &QProcess::bytesWritten);
        QObjectPrivate::connect(stdinChannel.writer, &QWindowsPipeWriter::canWrite,
                                this, &QProcessPrivate::_q_canWrite);
    } else {
        if (stdinChannel.writer->isWriteOperationActive())
            return true;
    }

    stdinChannel.writer->write(writeBuffer.read());
    return true;
}

// Use ShellExecuteEx() to trigger an UAC prompt when CreateProcess()fails
// with ERROR_ELEVATION_REQUIRED.
static bool startDetachedUacPrompt(const QString &programIn, const QStringList &arguments,
                                   const QString &nativeArguments,
                                   const QString &workingDir, qint64 *pid)
{
    typedef BOOL (WINAPI *ShellExecuteExType)(SHELLEXECUTEINFOW *);

    static const ShellExecuteExType shellExecuteEx = // XP ServicePack 1 onwards.
        reinterpret_cast<ShellExecuteExType>(QSystemLibrary::resolve(QLatin1String("shell32"),
                                                                     "ShellExecuteExW"));
    if (!shellExecuteEx)
        return false;

    const QString args = qt_create_commandline(QString(),                   // needs arguments only
                                               arguments, nativeArguments);
    SHELLEXECUTEINFOW shellExecuteExInfo;
    memset(&shellExecuteExInfo, 0, sizeof(SHELLEXECUTEINFOW));
    shellExecuteExInfo.cbSize = sizeof(SHELLEXECUTEINFOW);
    shellExecuteExInfo.fMask = SEE_MASK_NOCLOSEPROCESS | SEE_MASK_UNICODE | SEE_MASK_FLAG_NO_UI | SEE_MASK_CLASSNAME;
    shellExecuteExInfo.lpClass = L"exefile";
    shellExecuteExInfo.lpVerb = L"runas";
    const QString program = QDir::toNativeSeparators(programIn);
    shellExecuteExInfo.lpFile = reinterpret_cast<LPCWSTR>(program.utf16());
    if (!args.isEmpty())
        shellExecuteExInfo.lpParameters = reinterpret_cast<LPCWSTR>(args.utf16());
    if (!workingDir.isEmpty())
        shellExecuteExInfo.lpDirectory = reinterpret_cast<LPCWSTR>(workingDir.utf16());
    shellExecuteExInfo.nShow = SW_SHOWNORMAL;

    if (!shellExecuteEx(&shellExecuteExInfo))
        return false;
    if (pid)
        *pid = qint64(GetProcessId(shellExecuteExInfo.hProcess));
    CloseHandle(shellExecuteExInfo.hProcess);
    return true;
}

static Q_PIPE pipeOrStdHandle(Q_PIPE pipe, DWORD handleNumber)
{
    return pipe != INVALID_Q_PIPE ? pipe : GetStdHandle(handleNumber);
}

bool QProcessPrivate::startDetached(qint64 *pid)
{
    static const DWORD errorElevationRequired = 740;

    if ((stdinChannel.type == Channel::Redirect && !openChannel(stdinChannel))
            || (stdoutChannel.type == Channel::Redirect && !openChannel(stdoutChannel))
            || (stderrChannel.type == Channel::Redirect && !openChannel(stderrChannel))) {
        closeChannel(&stdinChannel);
        closeChannel(&stdoutChannel);
        closeChannel(&stderrChannel);
        return false;
    }

    QString args = qt_create_commandline(program, arguments, nativeArguments);
    bool success = false;
    PROCESS_INFORMATION pinfo;

    void *envPtr = nullptr;
    QByteArray envlist;
    if (environment.d.constData()) {
        envlist = qt_create_environment(environment.d.constData()->vars);
        envPtr = envlist.data();
    }

    DWORD dwCreationFlags = (GetConsoleWindow() ? 0 : CREATE_NO_WINDOW);
    dwCreationFlags |= CREATE_UNICODE_ENVIRONMENT;
    STARTUPINFOW startupInfo = { sizeof( STARTUPINFO ), 0, 0, 0,
                                 (ulong)CW_USEDEFAULT, (ulong)CW_USEDEFAULT,
                                 (ulong)CW_USEDEFAULT, (ulong)CW_USEDEFAULT,
                                 0, 0, 0,
                                 STARTF_USESTDHANDLES,
                                 0, 0, 0,
                                 pipeOrStdHandle(stdinChannel.pipe[0], STD_INPUT_HANDLE),
                                 pipeOrStdHandle(stdoutChannel.pipe[1], STD_OUTPUT_HANDLE),
                                 pipeOrStdHandle(stderrChannel.pipe[1], STD_ERROR_HANDLE)
                               };

    QProcess::CreateProcessArguments cpargs = {
        nullptr, reinterpret_cast<wchar_t *>(const_cast<ushort *>(args.utf16())),
        nullptr, nullptr, true, dwCreationFlags, envPtr,
        workingDirectory.isEmpty()
            ? nullptr : reinterpret_cast<const wchar_t *>(workingDirectory.utf16()),
        &startupInfo, &pinfo
    };
    success = callCreateProcess(&cpargs);

    if (success) {
        CloseHandle(pinfo.hThread);
        CloseHandle(pinfo.hProcess);
        if (pid)
            *pid = pinfo.dwProcessId;
    } else if (GetLastError() == errorElevationRequired) {
        if (envPtr)
            qWarning("QProcess: custom environment will be ignored for detached elevated process.");
        if (!stdinChannel.file.isEmpty() || !stdoutChannel.file.isEmpty()
                || !stderrChannel.file.isEmpty()) {
            qWarning("QProcess: file redirection is unsupported for detached elevated processes.");
        }
        success = startDetachedUacPrompt(program, arguments, nativeArguments,
                                         workingDirectory, pid);
    }

    closeChannel(&stdinChannel);
    closeChannel(&stdoutChannel);
    closeChannel(&stderrChannel);
    return success;
}

#endif // QT_CONFIG(process)

QT_END_NAMESPACE
