InputStreamPtr InputStreamPool::getInputStream(const std::string& sFileName) const
{
    {
        ScopedLock<FastMutex> lock(m_mutex);

        InputStreamPtr pInStream = doGetInputStream(sFileName);
        if (pInStream.isNotNull())
        {
            return pInStream;
        }
    }
    return m_pFileSystem->openFile(sFileName);
}