Use slice method where applicable

These code segments already have its boundary checked and can thus be faster.

PR #22411.

src/app/application.cpp

@@ -659,7 +659,13 @@ void Application::runExternalProgram(const QString &programTemplate, const BitTo
     {
         // strip redundant quotes
         if (arg.startsWith(u'"') && arg.endsWith(u'"'))
-            arg = arg.mid(1, (arg.size() - 2));
+        {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+            arg.slice(1, (arg.size() - 2));
+#else
+            arg.removeLast().removeFirst();
+#endif
+        }
 
         arg = replaceVariables(arg);
     }

src/app/cmdoptions.cpp

@@ -465,13 +465,13 @@ QBtCommandLineParameters parseCommandLine(const QStringList &args)
     return result;
 }
 
-QString wrapText(const QString &text, int initialIndentation = USAGE_TEXT_COLUMN, int wrapAtColumn = WRAP_AT_COLUMN)
+QString wrapText(const QString &text, const int initialIndentation = USAGE_TEXT_COLUMN, const int wrapAtColumn = WRAP_AT_COLUMN)
 {
-    QStringList words = text.split(u' ');
+    const QStringList words = text.split(u' ');
     QStringList lines = {words.first()};
     int currentLineMaxLength = wrapAtColumn - initialIndentation;
 
-    for (const QString &word : asConst(words.mid(1)))
+    for (const QString &word : asConst(words.sliced(1)))
     {
         if (lines.last().length() + word.length() + 1 < currentLineMaxLength)
         {

src/base/bittorrent/peeraddress.cpp

@@ -39,7 +39,11 @@ PeerAddress PeerAddress::parse(const QStringView address)
     if (address.startsWith(u'[') && address.contains(u"]:"))
     {  // IPv6
         ipPort = address.split(u"]:");
-        ipPort[0] = ipPort[0].mid(1);  // chop '['
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+        ipPort[0].slice(1);  // chop '['
+#else
+        ipPort[0] = ipPort[0].sliced(1);  // chop '['
+#endif
     }
     else if (address.contains(u':'))
     {  // IPv4

src/base/bittorrent/sessionimpl.cpp

@@ -365,7 +365,7 @@ QString Session::subcategoryName(const QString &category)
 {
     const int sepIndex = category.lastIndexOf(u'/');
     if (sepIndex >= 0)
-        return category.mid(sepIndex + 1);
+        return category.sliced(sepIndex + 1);
 
     return category;
 }
@@ -374,7 +374,7 @@ QString Session::parentCategoryName(const QString &category)
 {
     const int sepIndex = category.lastIndexOf(u'/');
     if (sepIndex >= 0)
-        return category.left(sepIndex);
+        return category.first(sepIndex);
 
     return {};
 }
@@ -385,7 +385,7 @@ QStringList Session::expandCategory(const QString &category)
     int index = 0;
     while ((index = category.indexOf(u'/', index)) >= 0)
     {
-        result << category.left(index);
+        result << category.first(index);
         ++index;
     }
     result << category;

src/base/http/connection.cpp

@@ -155,7 +155,11 @@ void Connection::read()
                     sendResponse(resp);
                 }
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+                m_receivedData.slice(result.frameSize);
+#else
                 m_receivedData.remove(0, result.frameSize);
+#endif
             }
             break;
 

src/base/http/requestparser.cpp

@@ -69,8 +69,8 @@ namespace
             return false;
         }
 
-        const QString name = line.left(i).trimmed().toString().toLower();
+        const QString name = line.first(i).trimmed().toString().toLower();
-        const QString value = line.mid(i + 1).trimmed().toString();
+        const QString value = line.sliced(i + 1).trimmed().toString();
         out[name] = value;
 
         return true;
@@ -206,13 +206,13 @@ bool RequestParser::parseRequestLine(const QString &line)
     // Request Target
     const QByteArray url {match.captured(2).toLatin1()};
     const int sepPos = url.indexOf('?');
-    const QByteArrayView pathComponent = ((sepPos == -1) ? url : QByteArrayView(url).mid(0, sepPos));
+    const QByteArrayView pathComponent = ((sepPos == -1) ? url : QByteArrayView(url).first(sepPos));
 
     m_request.path = QString::fromUtf8(QByteArray::fromPercentEncoding(asQByteArray(pathComponent)));
 
     if (sepPos >= 0)
     {
-        const QByteArrayView query = QByteArrayView(url).mid(sepPos + 1);
+        const QByteArrayView query = QByteArrayView(url).sliced(sepPos + 1);
 
         // [rfc3986] 2.4 When to Encode or Decode
         // URL components should be separated before percent-decoding
@@ -221,8 +221,8 @@ bool RequestParser::parseRequestLine(const QString &line)
             const int eqCharPos = param.indexOf('=');
             if (eqCharPos <= 0) continue;  // ignores params without name
 
-            const QByteArrayView nameComponent = param.mid(0, eqCharPos);
+            const QByteArrayView nameComponent = param.first(eqCharPos);
-            const QByteArrayView valueComponent = param.mid(eqCharPos + 1);
+            const QByteArrayView valueComponent = param.sliced(eqCharPos + 1);
             const QString paramName = QString::fromUtf8(
                 QByteArray::fromPercentEncoding(asQByteArray(nameComponent)).replace('+', ' '));
             const QByteArray paramValue = QByteArray::fromPercentEncoding(asQByteArray(valueComponent)).replace('+', ' ');
@@ -270,7 +270,7 @@ bool RequestParser::parsePostMessage(const QByteArrayView data)
             return false;
         }
 
-        const QByteArray delimiter = Utils::String::unquote(QStringView(contentType).mid(idx + boundaryFieldName.size())).toLatin1();
+        const QByteArray delimiter = Utils::String::unquote(QStringView(contentType).sliced(idx + boundaryFieldName.size())).toLatin1();
         if (delimiter.isEmpty())
         {
             qWarning() << Q_FUNC_INFO << "boundary delimiter field empty!";
@@ -310,8 +310,8 @@ bool RequestParser::parseFormData(const QByteArrayView data)
         return false;
     }
 
-    const QString headers = QString::fromLatin1(data.mid(0, eohPos));
+    const QString headers = QString::fromLatin1(data.first(eohPos));
-    const QByteArrayView payload = viewWithoutEndingWith(data.mid((eohPos + EOH.size()), data.size()), CRLF);
+    const QByteArrayView payload = viewWithoutEndingWith(data.sliced((eohPos + EOH.size())), CRLF);
 
     HeaderMap headersMap;
     const QList<QStringView> headerLines = QStringView(headers).split(QString::fromLatin1(CRLF), Qt::SkipEmptyParts);
@@ -328,8 +328,8 @@ bool RequestParser::parseFormData(const QByteArrayView data)
                 if (idx < 0)
                     continue;
 
-                const QString name = directive.left(idx).trimmed().toString().toLower();
+                const QString name = directive.first(idx).trimmed().toString().toLower();
-                const QString value = Utils::String::unquote(directive.mid(idx + 1).trimmed()).toString();
+                const QString value = Utils::String::unquote(directive.sliced(idx + 1).trimmed()).toString();
                 headersMap[name] = value;
             }
         }

src/base/net/smtp.cpp

@@ -148,8 +148,7 @@ void Smtp::sendMail(const QString &from, const QString &to, const QString &subje
     // Encode the body in base64
     QString crlfBody = body;
     const QByteArray b = crlfBody.replace(u"\n"_s, u"\r\n"_s).toUtf8().toBase64();
-    const int ct = b.length();
+    for (int i = 0, end = b.length(); i < end; i += 78)
-    for (int i = 0; i < ct; i += 78)
         m_message += b.mid(i, 78);
     m_from = from;
     m_rcpt = to;
@@ -190,8 +189,12 @@ void Smtp::readyRead()
     {
         const int pos = m_buffer.indexOf("\r\n");
         if (pos < 0) return; // Loop exit condition
-        const QByteArray line = m_buffer.left(pos);
+        const QByteArray line = m_buffer.first(pos);
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+        m_buffer.slice(pos + 2);
+#else
         m_buffer.remove(0, (pos + 2));
+#endif
         qDebug() << "Response line:" << line;
         // Extract response code
         const QByteArray code = line.left(3);

src/base/path.cpp

@@ -94,7 +94,13 @@ bool Path::isValid() const
 #if defined(Q_OS_WIN)
     QStringView view = m_pathStr;
     if (hasDriveLetter(view))
-        view = view.mid(3);
+    {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+        view.slice(3);
+#else
+        view = view.sliced(3);
+#endif
+    }
 
     // \\37 is using base-8 number system
     const QRegularExpression regex {u"[\\0-\\37:?\"*<>|]"_s};
@@ -147,9 +153,9 @@ Path Path::rootItem() const
 #ifdef Q_OS_WIN
     // should be `c:/` instead of `c:`
     if ((slashIndex == 2) && hasDriveLetter(m_pathStr))
-        return createUnchecked(m_pathStr.left(slashIndex + 1));
+        return createUnchecked(m_pathStr.first(slashIndex + 1));
 #endif
-    return createUnchecked(m_pathStr.left(slashIndex));
+    return createUnchecked(m_pathStr.first(slashIndex));
 }
 
 Path Path::parentPath() const
@@ -167,9 +173,9 @@ Path Path::parentPath() const
     // should be `c:/` instead of `c:`
     // Windows "drive letter" is limited to one alphabet
     if ((slashIndex == 2) && hasDriveLetter(m_pathStr))
-        return (m_pathStr.size() == 3) ? Path() : createUnchecked(m_pathStr.left(slashIndex + 1));
+        return (m_pathStr.size() == 3) ? Path() : createUnchecked(m_pathStr.first(slashIndex + 1));
 #endif
-    return createUnchecked(m_pathStr.left(slashIndex));
+    return createUnchecked(m_pathStr.first(slashIndex));
 }
 
 QString Path::filename() const
@@ -178,7 +184,7 @@ QString Path::filename() const
     if (slashIndex == -1)
         return m_pathStr;
 
-    return m_pathStr.mid(slashIndex + 1);
+    return m_pathStr.sliced(slashIndex + 1);
 }
 
 QString Path::extension() const
@@ -188,9 +194,9 @@ QString Path::extension() const
         return (u"." + suffix);
 
     const int slashIndex = m_pathStr.lastIndexOf(u'/');
-    const auto filename = QStringView(m_pathStr).mid(slashIndex + 1);
+    const auto filename = QStringView(m_pathStr).sliced(slashIndex + 1);
     const int dotIndex = filename.lastIndexOf(u'.', -2);
-    return ((dotIndex == -1) ? QString() : filename.mid(dotIndex).toString());
+    return ((dotIndex == -1) ? QString() : filename.sliced(dotIndex).toString());
 }
 
 bool Path::hasExtension(const QStringView ext) const
@@ -293,7 +299,7 @@ Path Path::commonPath(const Path &left, const Path &right)
     if (commonItemsCount > 0)
         commonPathSize += (commonItemsCount - 1); // size of intermediate separators
 
-    return Path::createUnchecked(left.m_pathStr.left(commonPathSize));
+    return Path::createUnchecked(left.m_pathStr.first(commonPathSize));
 }
 
 Path Path::findRootFolder(const PathList &filePaths)
@@ -322,7 +328,13 @@ void Path::stripRootFolder(PathList &filePaths)
         return;
 
     for (Path &filePath : filePaths)
+    {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+        filePath.m_pathStr.slice(commonRootFolder.m_pathStr.size() + 1);
+#else
         filePath.m_pathStr.remove(0, (commonRootFolder.m_pathStr.size() + 1));
+#endif
+    }
 }
 
 void Path::addRootFolder(PathList &filePaths, const Path &rootFolder)

src/base/rss/rss_autodownloadrule.cpp

@@ -304,7 +304,13 @@ bool AutoDownloadRule::matchesEpisodeFilterExpression(const QString &articleTitl
 
         // We need to trim leading zeroes, but if it's all zeros then we want episode zero.
         while ((episode.size() > 1) && episode.startsWith(u'0'))
-            episode = episode.right(episode.size() - 1);
+        {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+            episode.slice(1);
+#else
+            episode.remove(0, 1);
+#endif
+        }
 
         if (episode.indexOf(u'-') != -1)
         { // Range detected
@@ -328,7 +334,7 @@ bool AutoDownloadRule::matchesEpisodeFilterExpression(const QString &articleTitl
 
                 if (episode.endsWith(u'-'))
                 { // Infinite range
-                    const int episodeOurs {QStringView(episode).left(episode.size() - 1).toInt()};
+                    const int episodeOurs {QStringView(episode).chopped(1).toInt()};
                     if (((seasonTheirs == seasonOurs) && (episodeTheirs >= episodeOurs)) || (seasonTheirs > seasonOurs))
                         return true;
                 }

src/base/rss/rss_item.cpp

@@ -97,7 +97,7 @@ QStringList Item::expandPath(const QString &path)
     int index = 0;
     while ((index = path.indexOf(Item::PathSeparator, index)) >= 0)
     {
-        result << path.left(index);
+        result << path.first(index);
         ++index;
     }
     result << path;
@@ -108,11 +108,11 @@ QStringList Item::expandPath(const QString &path)
 QString Item::parentPath(const QString &path)
 {
     const int pos = path.lastIndexOf(Item::PathSeparator);
-    return (pos >= 0) ? path.left(pos) : QString();
+    return (pos >= 0) ? path.first(pos) : QString();
 }
 
 QString Item::relativeName(const QString &path)
 {
-    int pos;
+    const int pos = path.lastIndexOf(Item::PathSeparator);
-    return ((pos = path.lastIndexOf(Item::PathSeparator)) >= 0 ? path.right(path.size() - (pos + 1)) : path);
+    return (pos >= 0) ? path.sliced(pos + 1) : path;
 }

src/base/rss/rss_session.cpp

@@ -385,8 +385,14 @@ void Session::loadLegacy()
     uint i = 0;
     for (QString legacyPath : legacyFeedPaths)
     {
-        if (Item::PathSeparator == legacyPath[0])
+        if (legacyPath.startsWith(Item::PathSeparator))
+        {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+            legacyPath.slice(1);
+#else
             legacyPath.remove(0, 1);
+#endif
+        }
         const QString parentFolderPath = Item::parentPath(legacyPath);
         const QString feedUrl = Item::relativeName(legacyPath);
 

src/base/search/searchpluginmanager.cpp

@@ -469,9 +469,9 @@ void SearchPluginManager::pluginDownloadFinished(const Net::DownloadResult &resu
     }
     else
     {
-        const QString url = result.url;
+        const QString &url = result.url;
-        QString pluginName = url.mid(url.lastIndexOf(u'/') + 1);
+        const QString pluginName = url.sliced(url.lastIndexOf(u'/') + 1)
-        pluginName.replace(u".py"_s, u""_s, Qt::CaseInsensitive);
+            .replace(u".py"_s, u""_s, Qt::CaseInsensitive);
 
         if (pluginInfo(pluginName))
             emit pluginUpdateFailed(pluginName, tr("Failed to download the plugin file. %1").arg(result.errorString));
@@ -653,7 +653,7 @@ PluginVersion SearchPluginManager::getPluginVersion(const Path &filePath)
         const auto line = QString::fromUtf8(pluginFile.readLine(lineMaxLength)).remove(u' ');
         if (!line.startsWith(u"#VERSION:", Qt::CaseInsensitive)) continue;
 
-        const QString versionStr = line.mid(9);
+        const QString versionStr = line.sliced(9);
         const auto version = PluginVersion::fromString(versionStr);
         if (version.isValid())
             return version;

src/base/utils/compare.cpp

@@ -64,7 +64,7 @@ int Utils::Compare::naturalCompare(const QString &left, const QString &right, co
                 const int start = pos;
                 while ((pos < str.size()) && str[pos].isDigit())
                     ++pos;
-                return str.mid(start, (pos - start));
+                return str.sliced(start, (pos - start));
             };
 
             const QStringView numViewL = numberView(left, posL);

src/base/utils/string.h

@@ -49,12 +49,13 @@ namespace Utils::String
     template <typename T>
     T unquote(const T &str, const QString &quotes = u"\""_s)
     {
-        if (str.length() < 2) return str;
+        if (str.length() < 2)
+            return str;
 
         for (const QChar quote : quotes)
         {
             if (str.startsWith(quote) && str.endsWith(quote))
-                return str.mid(1, (str.length() - 2));
+                return str.sliced(1, (str.length() - 2));
         }
 
         return str;

src/gui/addnewtorrentdialog.cpp

@@ -122,7 +122,7 @@ namespace
         fsPathEdit->setCurrentIndex(existingIndex);
     }
 
-    void updatePathHistory(const QString &settingsKey, const Path &path, const int maxLength)
+    void updatePathHistory(const QString &settingsKey, const Path &path, const qsizetype maxLength)
     {
         // Add last used save path to the front of history
 
@@ -134,7 +134,10 @@ namespace
         else
             pathList.prepend(path.toString());
 
-        settings()->storeValue(settingsKey, QStringList(pathList.mid(0, maxLength)));
+        if (pathList.size() > maxLength)
+            pathList.resize(maxLength);
+
+        settings()->storeValue(settingsKey, pathList);
     }
 }
 
@@ -375,8 +378,7 @@ AddNewTorrentDialog::AddNewTorrentDialog(const BitTorrent::TorrentDescriptor &to
     connect(Preferences::instance(), &Preferences::changed, []
     {
         const int length = Preferences::instance()->addNewTorrentDialogSavePathHistoryLength();
-        settings()->storeValue(KEY_SAVEPATHHISTORY
+        settings()->storeValue(KEY_SAVEPATHHISTORY, settings()->loadValue<QStringList>(KEY_SAVEPATHHISTORY).mid(0, length));
-                , QStringList(settings()->loadValue<QStringList>(KEY_SAVEPATHHISTORY).mid(0, length)));
     });
 
     setCurrentContext(std::make_shared<Context>(Context {torrentDescr, inParams}));

src/gui/fspathedit.cpp

@@ -234,14 +234,14 @@ void FileSystemPathEdit::setFileNameFilter(const QString &val)
     const int closeBracePos = val.indexOf(u')', (openBracePos + 1));
     if ((openBracePos > 0) && (closeBracePos > 0) && (closeBracePos > openBracePos + 2))
     {
-        QString filterString = val.mid(openBracePos + 1, closeBracePos - openBracePos - 1);
+        const QString filterString = val.sliced((openBracePos + 1), (closeBracePos - openBracePos - 1));
         if (filterString == u"*")
         {        // no filters
             d->m_editor->setFilenameFilters({});
         }
         else
         {
-            QStringList filters = filterString.split(u' ', Qt::SkipEmptyParts);
+            const QStringList filters = filterString.split(u' ', Qt::SkipEmptyParts);
             d->m_editor->setFilenameFilters(filters);
         }
     }

src/gui/optionsdialog.cpp

@@ -1859,10 +1859,10 @@ void OptionsDialog::setLocale(const QString &localeStr)
     if (index < 0)
     {
         //Attempt to find a language match without a country
-        int pos = name.indexOf(u'_');
+        const int pos = name.indexOf(u'_');
         if (pos > -1)
         {
-            QString lang = name.left(pos);
+            const QString lang = name.first(pos);
             index = m_ui->comboLanguage->findData(lang, Qt::UserRole);
         }
     }

src/gui/rss/rsswidget.cpp

@@ -82,7 +82,13 @@ namespace
 
             QString relativePath = match.captured(6);
             if (relativePath.startsWith(u'/'))
-                relativePath = relativePath.mid(1);
+            {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+                relativePath.slice(1);
+#else
+                relativePath.remove(0, 1);
+#endif
+            }
 
             const QString absoluteUrl = !host.isEmpty()
                     ? QString(defaultScheme + u':' + host) : (normalizedBaseUrl + relativePath);

src/gui/search/searchsortmodel.cpp

@@ -46,7 +46,7 @@ void SearchSortModel::setNameFilter(const QString &searchTerm)
 {
     m_searchTerm = searchTerm;
     if ((searchTerm.length() > 2) && searchTerm.startsWith(u'"') && searchTerm.endsWith(u'"'))
-        m_searchTermWords = QStringList(m_searchTerm.mid(1, m_searchTerm.length() - 2));
+        m_searchTermWords = QStringList(m_searchTerm.sliced(1, (m_searchTerm.length() - 2)));
     else
         m_searchTermWords = searchTerm.split(u' ', Qt::SkipEmptyParts);
 }

src/gui/search/searchwidget.cpp

@@ -675,7 +675,7 @@ void SearchWidget::loadHistory()
         }
 
         if (history.size() > m_historyLength)
-            history = history.mid(history.size() - m_historyLength);
+            history.remove(0, (history.size() - m_historyLength));
 
         m_searchPatternCompleterModel->setStringList(history);
     });

src/gui/transferlistfilters/categoryfiltermodel.cpp

@@ -174,9 +174,9 @@ namespace
 {
     QString shortName(const QString &fullName)
     {
-        int pos = fullName.lastIndexOf(u'/');
+        const int pos = fullName.lastIndexOf(u'/');
         if (pos >= 0)
-            return fullName.mid(pos + 1);
+            return fullName.sliced(pos + 1);
         return fullName;
     }
 }

src/gui/transferlistfilters/trackersfilterwidget.cpp

@@ -555,7 +555,7 @@ void TrackersFilterWidget::handleFavicoDownloadFinished(const Net::DownloadResul
     {
         if (result.url.endsWith(u".ico", Qt::CaseInsensitive))
         {
-            const QString faviconURL = result.url.left(result.url.size() - 4) + u".png";
+            const QString faviconURL = QStringView(result.url).chopped(4) + u".png";
             for (const auto &trackerHost : trackerHosts)
             {
                 if (m_trackers.contains(trackerHost))

src/webui/webapplication.cpp

@@ -89,8 +89,8 @@ namespace
             if (idx < 0)
                 continue;
 
-            const QString name = cookie.left(idx).trimmed().toString();
+            const QString name = cookie.first(idx).trimmed().toString();
-            const QString value = Utils::String::unquote(cookie.mid(idx + 1).trimmed()).toString();
+            const QString value = Utils::String::unquote(cookie.sliced(idx + 1).trimmed()).toString();
             ret.insert(name, value);
         }
         return ret;
@@ -469,8 +469,8 @@ void WebApplication::configure()
                 continue;
             }
 
-            const QString header = line.left(idx).trimmed().toString();
+            const QString header = line.first(idx).trimmed().toString();
-            const QString value = line.mid(idx + 1).trimmed().toString();
+            const QString value = line.sliced(idx + 1).trimmed().toString();
             m_prebuiltHeaders.push_back({header, value});
         }
     }