annotate data/fileio/FileSource.cpp @ 875:3e6ed8a8577b tonioni

Use a sparse time-value model only for outputs with fixed bin count of 1, not for those with unknown bin count.
(Precursor to using more than one model for outputs with unknown bin count)

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2007 QMUL.
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#include "FileSource.h"

#include "base/TempDirectory.h"
#include "base/Exceptions.h"
#include "base/ProgressReporter.h"
#include "system/System.h"

#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QFileInfo>
#include <QDir>
#include <QCoreApplication>
#include <QThreadStorage>

#include <iostream>
#include <cstdlib>

#include <unistd.h>

//#define DEBUG_FILE_SOURCE 1

int
FileSource::m_count = 0;

QMutex
FileSource::m_fileCreationMutex;

FileSource::RemoteRefCountMap
FileSource::m_refCountMap;

FileSource::RemoteLocalMap
FileSource::m_remoteLocalMap;

QMutex
FileSource::m_mapMutex;

#ifdef DEBUG_FILE_SOURCE
static int extantCount = 0;
static std::map<QString, int> urlExtantCountMap;
static void incCount(QString url) {
    ++extantCount;
    if (urlExtantCountMap.find(url) == urlExtantCountMap.end()) {
        urlExtantCountMap[url] = 1;
    } else {
        ++urlExtantCountMap[url];
    }
    cerr << "FileSource: Now " << urlExtantCountMap[url] << " for this url, " << extantCount << " total" << endl;
}
static void decCount(QString url) {
    --extantCount;
    --urlExtantCountMap[url];
    cerr << "FileSource: Now " << urlExtantCountMap[url] << " for this url, " << extantCount << " total" << endl;
}
#endif

static QThreadStorage<QNetworkAccessManager *> nms;

FileSource::FileSource(QString fileOrUrl, ProgressReporter *reporter,
                       QString preferredContentType) :
    m_rawFileOrUrl(fileOrUrl),
    m_url(fileOrUrl, QUrl::StrictMode),
    m_localFile(0),
    m_reply(0),
    m_preferredContentType(preferredContentType),
    m_ok(false),
    m_lastStatus(0),
    m_resource(fileOrUrl.startsWith(':')),
    m_remote(isRemote(fileOrUrl)),
    m_done(false),
    m_leaveLocalFile(false),
    m_reporter(reporter),
    m_refCounted(false)
{
    if (m_resource) { // qrc file
        m_url = QUrl("qrc" + fileOrUrl);
    }

    if (m_url.toString() == "") {
        m_url = QUrl(fileOrUrl, QUrl::TolerantMode);
    }
 
#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::FileSource(" << fileOrUrl << "): url <" << m_url.toString() << ">" << endl;
    incCount(m_url.toString());
#endif

    if (!canHandleScheme(m_url)) {
        cerr << "FileSource::FileSource: ERROR: Unsupported scheme in URL \"" << m_url.toString() << "\"" << endl;
        m_errorString = tr("Unsupported scheme in URL");
        return;
    }

    init();

    if (!isRemote() &&
        !isAvailable()) {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::FileSource: Failed to open local file with URL \"" << m_url.toString() << "\"; trying again assuming filename was encoded" << endl;
#endif
        m_url = QUrl::fromEncoded(fileOrUrl.toLatin1());
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::FileSource: URL is now \"" << m_url.toString() << "\"" << endl;
#endif
        init();
    }

    if (isRemote() &&
        (fileOrUrl.contains('%') ||
         fileOrUrl.contains("--"))) { // for IDNA

        waitForStatus();

        if (!isAvailable()) {

            // The URL was created on the assumption that the string
            // was human-readable.  Let's try again, this time
            // assuming it was already encoded.
            cerr << "FileSource::FileSource: Failed to retrieve URL \""
                      << fileOrUrl 
                      << "\" as human-readable URL; "
                      << "trying again treating it as encoded URL"
                      << endl;

            // even though our cache file doesn't exist (because the
            // resource was 404), we still need to ensure we're no
            // longer associating a filename with this url in the
            // refcount map -- or createCacheFile will think we've
            // already done all the work and no request will be sent
            deleteCacheFile();

            m_url = QUrl::fromEncoded(fileOrUrl.toLatin1());

            m_ok = false;
            m_done = false;
            m_lastStatus = 0;
            init();
        }
    }

    if (!isRemote()) {
        emit statusAvailable();
        emit ready();
    }

#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::FileSource(string) exiting" << endl;
#endif
}

FileSource::FileSource(QUrl url, ProgressReporter *reporter) :
    m_url(url),
    m_localFile(0),
    m_reply(0),
    m_ok(false),
    m_lastStatus(0),
    m_resource(false),
    m_remote(isRemote(url.toString())),
    m_done(false),
    m_leaveLocalFile(false),
    m_reporter(reporter),
    m_refCounted(false)
{
#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::FileSource(" << url.toString() << ") [as url]" << endl;
    incCount(m_url.toString());
#endif

    if (!canHandleScheme(m_url)) {
        cerr << "FileSource::FileSource: ERROR: Unsupported scheme in URL \"" << m_url.toString() << "\"" << endl;
        m_errorString = tr("Unsupported scheme in URL");
        return;
    }

    init();

#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::FileSource(url) exiting" << endl;
#endif
}

FileSource::FileSource(const FileSource &rf) :
    QObject(),
    m_url(rf.m_url),
    m_localFile(0),
    m_reply(0),
    m_ok(rf.m_ok),
    m_lastStatus(rf.m_lastStatus),
    m_resource(rf.m_resource),
    m_remote(rf.m_remote),
    m_done(false),
    m_leaveLocalFile(false),
    m_reporter(rf.m_reporter),
    m_refCounted(false)
{
#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::FileSource(" << m_url.toString() << ") [copy ctor]" << endl;
    incCount(m_url.toString());
#endif

    if (!canHandleScheme(m_url)) {
        cerr << "FileSource::FileSource: ERROR: Unsupported scheme in URL \"" << m_url.toString() << "\"" << endl;
        m_errorString = tr("Unsupported scheme in URL");
        return;
    }

    if (!isRemote()) {
        m_localFilename = rf.m_localFilename;
    } else {
        QMutexLocker locker(&m_mapMutex);
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::FileSource(copy ctor): ref count is "
                  << m_refCountMap[m_url] << endl;
#endif
        if (m_refCountMap[m_url] > 0) {
            m_refCountMap[m_url]++;
#ifdef DEBUG_FILE_SOURCE
            cerr << "raised it to " << m_refCountMap[m_url] << endl;
#endif
            m_localFilename = m_remoteLocalMap[m_url];
            m_refCounted = true;
        } else {
            m_ok = false;
            m_lastStatus = 404;
        }
    }

    m_done = true;

#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::FileSource(" << m_url.toString() << ") [copy ctor]: note: local filename is \"" << m_localFilename << "\"" << endl;
#endif

#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::FileSource(copy ctor) exiting" << endl;
#endif
}

FileSource::~FileSource()
{
#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource(" << m_url.toString() << ")::~FileSource" << endl;
    decCount(m_url.toString());
#endif

    cleanup();

    if (isRemote() && !m_leaveLocalFile) deleteCacheFile();
}

void
FileSource::init()
{
    { // check we have a QNetworkAccessManager
        QMutexLocker locker(&m_mapMutex);
        if (!nms.hasLocalData()) {
            nms.setLocalData(new QNetworkAccessManager());
        }
    }

    if (isResource()) {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::init: Is a resource" << endl;
#endif
        QString resourceFile = m_url.toString();
        resourceFile.replace(QRegExp("^qrc:"), ":");
        
        if (!QFileInfo(resourceFile).exists()) {
#ifdef DEBUG_FILE_SOURCE
            cerr << "FileSource::init: Resource file of this name does not exist, switching to non-resource URL" << endl;
#endif
            m_url = resourceFile;
            m_resource = false;
        }
    }

    if (!isRemote() && !isResource()) {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::init: Not a remote URL" << endl;
#endif
        bool literal = false;
        m_localFilename = m_url.toLocalFile();

        if (m_localFilename == "") {
            // QUrl may have mishandled the scheme (e.g. in a DOS path)
            m_localFilename = m_rawFileOrUrl;
#ifdef DEBUG_FILE_SOURCE
            cerr << "FileSource::init: Trying literal local filename \""
                      << m_localFilename << "\"" << endl;
#endif
            literal = true;
        }
        m_localFilename = QFileInfo(m_localFilename).absoluteFilePath();

#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::init: URL translates to absolute filename \""
                  << m_localFilename << "\" (with literal=" << literal << ")"
                  << endl;
#endif
        m_ok = true;
        m_lastStatus = 200;

        if (!QFileInfo(m_localFilename).exists()) {
            if (literal) {
                m_lastStatus = 404;
            } else {
#ifdef DEBUG_FILE_SOURCE
                cerr << "FileSource::init: Local file of this name does not exist, trying URL as a literal filename" << endl;
#endif
                // Again, QUrl may have been mistreating us --
                // e.g. dropping a part that looks like query data
                m_localFilename = m_rawFileOrUrl;
                literal = true;
                if (!QFileInfo(m_localFilename).exists()) {
                    m_lastStatus = 404;
                }
            }
        }

        m_done = true;
        return;
    }

    if (createCacheFile()) {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::init: Already have this one" << endl;
#endif
        m_ok = true;
        if (!QFileInfo(m_localFilename).exists()) {
            m_lastStatus = 404;
        } else {
            m_lastStatus = 200;
        }
        m_done = true;
        return;
    }

    if (m_localFilename == "") return;

    m_localFile = new QFile(m_localFilename);
    m_localFile->open(QFile::WriteOnly);

    if (isResource()) {

        // Absent resource file case was dealt with at the top -- this
        // is the successful case

        QString resourceFileName = m_url.toString();
        resourceFileName.replace(QRegExp("^qrc:"), ":");
        QFile resourceFile(resourceFileName);
        resourceFile.open(QFile::ReadOnly);
        QByteArray ba(resourceFile.readAll());
        
#ifdef DEBUG_FILE_SOURCE
        cerr << "Copying " << ba.size() << " bytes from resource file to cache file" << endl;
#endif

        qint64 written = m_localFile->write(ba);
        m_localFile->close();
        delete m_localFile;
        m_localFile = 0;

        if (written != ba.size()) {
#ifdef DEBUG_FILE_SOURCE
            cerr << "Copy failed (wrote " << written << " bytes)" << endl;
#endif
            m_ok = false;
            return;
        } else {
            m_ok = true;
            m_lastStatus = 200;
            m_done = true;
        }

    } else {

        QString scheme = m_url.scheme().toLower();

#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::init: Don't have local copy of \""
                  << m_url.toString() << "\", retrieving" << endl;
#endif

        if (scheme == "http" || scheme == "https" || scheme == "ftp") {
            initRemote();
#ifdef DEBUG_FILE_SOURCE
            cerr << "FileSource: initRemote returned" << endl;
#endif
        } else {
            m_remote = false;
            m_ok = false;
        }
    }

    if (m_ok) {
        
        QMutexLocker locker(&m_mapMutex);

        if (m_refCountMap[m_url] > 0) {
            // someone else has been doing the same thing at the same time,
            // but has got there first
            cleanup();
            m_refCountMap[m_url]++;
#ifdef DEBUG_FILE_SOURCE
            cerr << "FileSource::init: Another FileSource has got there first, abandoning our download and using theirs" << endl;
#endif
            m_localFilename = m_remoteLocalMap[m_url];
            m_refCounted = true;
            m_ok = true;
            if (!QFileInfo(m_localFilename).exists()) {
                m_lastStatus = 404;
            }
            m_done = true;
            return;
        }

        m_remoteLocalMap[m_url] = m_localFilename;
        m_refCountMap[m_url]++;
        m_refCounted = true;

        if (m_reporter && !m_done) {
            m_reporter->setMessage
                (tr("Downloading %1...").arg(m_url.toString()));
            connect(m_reporter, SIGNAL(cancelled()), this, SLOT(cancelled()));
            connect(this, SIGNAL(progress(int)),
                    m_reporter, SLOT(setProgress(int)));
        }
    }
}

void
FileSource::initRemote()
{
    m_ok = true;

    QNetworkRequest req;
    req.setUrl(m_url);
    
    if (m_preferredContentType != "") {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource: indicating preferred content type of \""
                  << m_preferredContentType << "\"" << endl;
#endif
        req.setRawHeader
            ("Accept",
             QString("%1, */*").arg(m_preferredContentType).toLatin1());
    }

    m_reply = nms.localData()->get(req);

    connect(m_reply, SIGNAL(readyRead()),
            this, SLOT(readyRead()));
    connect(m_reply, SIGNAL(error(QNetworkReply::NetworkError)),
            this, SLOT(replyFailed(QNetworkReply::NetworkError)));
    connect(m_reply, SIGNAL(finished()),
            this, SLOT(replyFinished()));
    connect(m_reply, SIGNAL(metaDataChanged()),
            this, SLOT(metaDataChanged()));
    connect(m_reply, SIGNAL(downloadProgress(qint64, qint64)),
            this, SLOT(downloadProgress(qint64, qint64)));
}

void
FileSource::cleanup()
{
    if (m_done) {
        delete m_localFile; // does not actually delete the file
        m_localFile = 0;
    }
    m_done = true;
    if (m_reply) {
        QNetworkReply *r = m_reply;
        m_reply = 0;
        r->abort();
        r->deleteLater();
    }
    if (m_localFile) {
        delete m_localFile; // does not actually delete the file
        m_localFile = 0;
    }
}

bool
FileSource::isRemote(QString fileOrUrl)
{
    // Note that a "scheme" with length 1 is probably a DOS drive letter
    QString scheme = QUrl(fileOrUrl).scheme().toLower();
    if (scheme == "" || scheme == "file" || scheme.length() == 1) return false;
    return true;
}

bool
FileSource::canHandleScheme(QUrl url)
{
    // Note that a "scheme" with length 1 is probably a DOS drive letter
    QString scheme = url.scheme().toLower();
    return (scheme == "http" || scheme == "https" ||
            scheme == "ftp" || scheme == "file" || scheme == "qrc" ||
            scheme == "" || scheme.length() == 1);
}

bool
FileSource::isAvailable()
{
    waitForStatus();
    bool available = true;
    if (!m_ok) available = false;
    else available = (m_lastStatus / 100 == 2);
#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::isAvailable: " << (available ? "yes" : "no")
              << endl;
#endif
    return available;
}

void
FileSource::waitForStatus()
{
    while (m_ok && (!m_done && m_lastStatus == 0)) {
//        cerr << "waitForStatus: processing (last status " << m_lastStatus << ")" << endl;
        QCoreApplication::processEvents();
    }
}

void
FileSource::waitForData()
{
    while (m_ok && !m_done) {
//        cerr << "FileSource::waitForData: calling QApplication::processEvents" << endl;
        QCoreApplication::processEvents();
        usleep(10000);
    }
}

void
FileSource::setLeaveLocalFile(bool leave)
{
    m_leaveLocalFile = leave;
}

bool
FileSource::isOK() const
{
    return m_ok;
}

bool
FileSource::isDone() const
{
    return m_done;
}

bool
FileSource::isResource() const
{
    return m_resource;
}

bool
FileSource::isRemote() const
{
    return m_remote;
}

QString
FileSource::getLocation() const
{
    return m_url.toString();
}

QString
FileSource::getLocalFilename() const
{
    return m_localFilename;
}

QString
FileSource::getBasename() const
{
    return QFileInfo(m_localFilename).fileName();
}

QString
FileSource::getContentType() const
{
    return m_contentType;
}

QString
FileSource::getExtension() const
{
    if (m_localFilename != "") {
        return QFileInfo(m_localFilename).suffix().toLower();
    } else {
        return QFileInfo(m_url.toLocalFile()).suffix().toLower();
    }
}

QString
FileSource::getErrorString() const
{
    return m_errorString;
}

void
FileSource::readyRead()
{
    m_localFile->write(m_reply->readAll());
}

void
FileSource::metaDataChanged()
{
#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::metaDataChanged" << endl;
#endif

    if (!m_reply) {
        cerr << "WARNING: FileSource::metaDataChanged() called without a reply object being known to us" << endl;
        return;
    }

    int status =
        m_reply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();

    if (status / 100 == 3) {
        QString location = m_reply->header
            (QNetworkRequest::LocationHeader).toString();
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::metaDataChanged: redirect to \""
                  << location << "\" received" << endl;
#endif
        if (location != "") {
            QUrl newUrl(location);
            if (newUrl != m_url) {
                cleanup();
                deleteCacheFile();
#ifdef DEBUG_FILE_SOURCE
                decCount(m_url.toString());
                incCount(newUrl.toString());
#endif
                m_url = newUrl;
                m_localFile = 0;
                m_lastStatus = 0;
                m_done = false;
                m_refCounted = false;
                init();
                return;
            }
        }
    }

    m_lastStatus = status;
    if (m_lastStatus / 100 >= 4) {
        m_errorString = QString("%1 %2")
            .arg(status)
            .arg(m_reply->attribute
                 (QNetworkRequest::HttpReasonPhraseAttribute).toString());
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::metaDataChanged: "
                  << m_errorString << endl;
#endif
    } else {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::metaDataChanged: "
                  << m_lastStatus << endl;
#endif
        m_contentType =
            m_reply->header(QNetworkRequest::ContentTypeHeader).toString();
    }
    emit statusAvailable();
}

void
FileSource::downloadProgress(qint64 done, qint64 total)
{
    int percent = int((double(done) / double(total)) * 100.0 - 0.1);
    emit progress(percent);
}

void
FileSource::cancelled()
{
    m_done = true;
    cleanup();

    m_ok = false;
    m_errorString = tr("Download cancelled");
}

void
FileSource::replyFinished()
{
    emit progress(100);

#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::replyFinished()" << endl;
#endif

    if (m_done) return;

    bool error = (m_lastStatus / 100 >= 4);

    cleanup();

    if (!error) {
        QFileInfo fi(m_localFilename);
        if (!fi.exists()) {
            m_errorString = tr("Failed to create local file %1").arg(m_localFilename);
            error = true;
        } else if (fi.size() == 0) {
            m_errorString = tr("File contains no data!");
            error = true;
        }
    }

    if (error) {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::done: error is " << error << ", deleting cache file" << endl;
#endif
        deleteCacheFile();
    }

    m_ok = !error;
    if (m_localFile) m_localFile->flush();
    m_done = true;
    emit ready();
}

void
FileSource::replyFailed(QNetworkReply::NetworkError)
{
    emit progress(100);
    m_errorString = m_reply->errorString();
    m_ok = false;
    m_done = true;
    cleanup();
    emit ready();
}

void
FileSource::deleteCacheFile()
{
#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::deleteCacheFile(\"" << m_localFilename << "\")" << endl;
#endif

    cleanup();

    if (m_localFilename == "") {
        return;
    }

    if (!isRemote()) {
#ifdef DEBUG_FILE_SOURCE
        cerr << "not a cache file" << endl;
#endif
        return;
    }

    if (m_refCounted) {

        QMutexLocker locker(&m_mapMutex);
        m_refCounted = false;

        if (m_refCountMap[m_url] > 0) {
            m_refCountMap[m_url]--;
#ifdef DEBUG_FILE_SOURCE
            cerr << "reduced ref count to " << m_refCountMap[m_url] << endl;
#endif
            if (m_refCountMap[m_url] > 0) {
                m_done = true;
                return;
            }
        }
    }

    m_fileCreationMutex.lock();

    if (!QFile(m_localFilename).remove()) {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::deleteCacheFile: ERROR: Failed to delete file \"" << m_localFilename << "\"" << endl;
#endif
    } else {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::deleteCacheFile: Deleted cache file \"" << m_localFilename << "\"" << endl;
#endif
        m_localFilename = "";
    }

    m_fileCreationMutex.unlock();

    m_done = true;
}

bool
FileSource::createCacheFile()
{
    {
        QMutexLocker locker(&m_mapMutex);

#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::createCacheFile: refcount is " << m_refCountMap[m_url] << endl;
#endif

        if (m_refCountMap[m_url] > 0) {
            m_refCountMap[m_url]++;
            m_localFilename = m_remoteLocalMap[m_url];
#ifdef DEBUG_FILE_SOURCE
            cerr << "raised it to " << m_refCountMap[m_url] << endl;
#endif
            m_refCounted = true;
            return true;
        }
    }

    QDir dir;
    try {
        dir = TempDirectory::getInstance()->getSubDirectoryPath("download");
    } catch (DirectoryCreationFailed f) {
#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::createCacheFile: ERROR: Failed to create temporary directory: " << f.what() << endl;
#endif
        return "";
    }

    QString filepart = m_url.path().section('/', -1, -1,
                                            QString::SectionSkipEmpty);

    QString extension = "";
    if (filepart.contains('.')) extension = filepart.section('.', -1);

    QString base = filepart;
    if (extension != "") {
        base = base.left(base.length() - extension.length() - 1);
    }
    if (base == "") base = "remote";

    QString filename;

    if (extension == "") {
        filename = base;
    } else {
        filename = QString("%1.%2").arg(base).arg(extension);
    }

    QString filepath(dir.filePath(filename));

#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::createCacheFile: URL is \"" << m_url.toString() << "\", dir is \"" << dir.path() << "\", base \"" << base << "\", extension \"" << extension << "\", filebase \"" << filename << "\", filename \"" << filepath << "\"" << endl;
#endif

    QMutexLocker fcLocker(&m_fileCreationMutex);

    ++m_count;

    if (QFileInfo(filepath).exists() ||
        !QFile(filepath).open(QFile::WriteOnly)) {

#ifdef DEBUG_FILE_SOURCE
        cerr << "FileSource::createCacheFile: Failed to create local file \""
                  << filepath << "\" for URL \""
                  << m_url.toString() << "\" (or file already exists): appending suffix instead" << endl;
#endif

        if (extension == "") {
            filename = QString("%1_%2").arg(base).arg(m_count);
        } else {
            filename = QString("%1_%2.%3").arg(base).arg(m_count).arg(extension);
        }
        filepath = dir.filePath(filename);

        if (QFileInfo(filepath).exists() ||
            !QFile(filepath).open(QFile::WriteOnly)) {

#ifdef DEBUG_FILE_SOURCE
            cerr << "FileSource::createCacheFile: ERROR: Failed to create local file \""
                      << filepath << "\" for URL \""
                      << m_url.toString() << "\" (or file already exists)" << endl;
#endif

            return "";
        }
    }

#ifdef DEBUG_FILE_SOURCE
    cerr << "FileSource::createCacheFile: url "
              << m_url.toString() << " -> local filename "
              << filepath << endl;
#endif
    
    m_localFilename = filepath;

    return false;
}