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#include "qsystemlibrary_p.h"

#include <QtCore/qvarlengtharray.h>
#include <QtCore/qstringlist.h>
#include <QtCore/qfileinfo.h>

/*!

    \internal
    \class QSystemLibrary

    The purpose of this class is to load only libraries that are located in
    well-known and trusted locations on the filesystem. It does not suffer from
    the security problem that QLibrary has, therefore it will never search in
    the current directory.

    The search order is the same as the order in DLL Safe search mode Windows,
    except that we don't search:
    * The current directory
    * The 16-bit system directory. (normally \c{c:\windows\system})
    * The Windows directory.  (normally \c{c:\windows})

    This means that the effective search order is:
    1. Application path.
    2. System libraries path.
    3. Trying all paths inside the PATH environment variable.

    Note, when onlySystemDirectory is true it will skip 1) and 3).

    DLL Safe search mode is documented in the "Dynamic-Link Library Search
    Order" document on MSDN.

    Since library loading code is sometimes shared between Windows and WinCE,
    this class can also be used on WinCE. However, its implementation just
    calls the LoadLibrary() function. This is ok since it is documented as not
    loading from the current directory on WinCE. This behaviour is documented
    in the documentation for LoadLibrary for Windows CE at MSDN.
    (http://msdn.microsoft.com/en-us/library/ms886736.aspx)
*/

QT_BEGIN_NAMESPACE

#if defined(Q_OS_WINCE)
HINSTANCE QSystemLibrary::load(const wchar_t *libraryName, bool onlySystemDirectory /* = true */)
{
    Q_UNUSED(onlySystemDirectory);
    return ::LoadLibrary(libraryName);
}
#else

#if !defined(QT_BOOTSTRAPPED)
extern QString qAppFileName();
#endif

static inline QString qSystemDirectory()
{
    QVarLengthArray<wchar_t, MAX_PATH> fullPath;

    UINT retLen = ::GetSystemDirectory(fullPath.data(), MAX_PATH);
    if (retLen > MAX_PATH) {
        fullPath.resize(retLen);
        retLen = ::GetSystemDirectory(fullPath.data(), retLen);
    }
    // in some rare cases retLen might be 0
    return QString::fromWCharArray(fullPath.constData(), int(retLen));
}

HINSTANCE QSystemLibrary::load(const wchar_t *libraryName, bool onlySystemDirectory /* = true */)
{
    QStringList searchOrder;

#if !defined(QT_BOOTSTRAPPED)
    if (!onlySystemDirectory)
        searchOrder << QFileInfo(qAppFileName()).path();
#endif
    searchOrder << qSystemDirectory();

    if (!onlySystemDirectory) {
        const QString PATH = QString::fromWCharArray((const wchar_t *)_wgetenv(L"PATH"));
        searchOrder << PATH.split(QLatin1Char(';'), QString::SkipEmptyParts);
    }

    const QString fileName = QString::fromWCharArray(libraryName) + QLatin1String(".dll");
    // Start looking in the order specified
    for (int i = 0; i < searchOrder.count(); ++i) {
        QString fullPathAttempt = searchOrder.at(i);
        if (!fullPathAttempt.endsWith(QLatin1Char('\\')))
            fullPathAttempt.append(QLatin1Char('\\'));
        fullPathAttempt.append(fileName);
        HINSTANCE inst = ::LoadLibrary((const wchar_t *)fullPathAttempt.utf16());
        if (inst != 0)
            return inst;
    }

    return 0;
}

#endif // !Q_OS_WINCE

QT_END_NAMESPACE
