diff options
author | Marc Mutz <marc.mutz@kdab.com> | 2015-12-25 16:58:47 +0100 |
---|---|---|
committer | Marc Mutz <marc.mutz@kdab.com> | 2015-12-29 19:02:18 +0000 |
commit | ad74c953998133887ac2362800772e0fa01dd3da (patch) | |
tree | 948d81dd181618d01c7cefb56ff15f8d249859b0 /src/corelib/tools/qcommandlineparser.cpp | |
parent | db0453742c7b156ce1d133d7c2c3c5959ff0c9e6 (diff) |
Optimize string building in QCommandLineParserPrivate::helpText()
- Don't detach QCoreApplication::arguments() by calling first(),
call constFirst()
- Use
QString foo;
foo += initial;
instead of
QString foo = initial;
where 'foo' receives more appends later (does not force an
initial capacity that is known to be too small).
- Use QStringBuilder more
- Don't use QStringLiteral in QStringBuilder expressions
- Reserve optionNameList. Its max. size is known ahead of time.
- Don't create optionNameStrings for hidden options.
The result was never used, they just served as placeholders
for the lock-step iteration that followed and wrapped the text.
- Don't create a QStringList to join(), append to the result
string directly.
- Cache the return value of option.valueName().
Not only is this faster, it also saves more than 2KiB in text
size on optimized GCC 4.9 Linux AMD64 builds.
Change-Id: Id1d88f3c36a521ac71f3a7436810ed31319077ae
Reviewed-by: David Faure <david.faure@kdab.com>
Diffstat (limited to 'src/corelib/tools/qcommandlineparser.cpp')
-rw-r--r-- | src/corelib/tools/qcommandlineparser.cpp | 42 |
1 files changed, 22 insertions, 20 deletions
diff --git a/src/corelib/tools/qcommandlineparser.cpp b/src/corelib/tools/qcommandlineparser.cpp index 15c7a0646f..89685a470a 100644 --- a/src/corelib/tools/qcommandlineparser.cpp +++ b/src/corelib/tools/qcommandlineparser.cpp @@ -1069,16 +1069,12 @@ QString QCommandLineParserPrivate::helpText() const { const QLatin1Char nl('\n'); QString text; - const QString exeName = QCoreApplication::instance()->arguments().first(); - QString usage = exeName; - if (!commandLineOptionList.isEmpty()) { - usage += QLatin1Char(' '); - usage += QCommandLineParser::tr("[options]"); - } - foreach (const PositionalArgumentDefinition &arg, positionalArgumentDefinitions) { - usage += QLatin1Char(' '); - usage += arg.syntax; - } + QString usage; + usage += QCoreApplication::instance()->arguments().constFirst(); // executable name + if (!commandLineOptionList.isEmpty()) + usage += QLatin1Char(' ') + QCommandLineParser::tr("[options]"); + foreach (const PositionalArgumentDefinition &arg, positionalArgumentDefinitions) + usage += QLatin1Char(' ') + arg.syntax; text += QCommandLineParser::tr("Usage: %1").arg(usage) + nl; if (!description.isEmpty()) text += description + nl; @@ -1086,27 +1082,33 @@ QString QCommandLineParserPrivate::helpText() const if (!commandLineOptionList.isEmpty()) text += QCommandLineParser::tr("Options:") + nl; QStringList optionNameList; + optionNameList.reserve(commandLineOptionList.size()); int longestOptionNameString = 0; foreach (const QCommandLineOption &option, commandLineOptionList) { - QStringList optionNames; - foreach (const QString &optionName, option.names()) { - if (optionName.length() == 1) - optionNames.append(QLatin1Char('-') + optionName); - else - optionNames.append(QStringLiteral("--") + optionName); + if (option.isHidden()) + continue; + const QStringList optionNames = option.names(); + QString optionNamesString; + foreach (const QString &optionName, optionNames) { + const int numDashes = optionName.length() == 1 ? 1 : 2; + optionNamesString += QLatin1String("--", numDashes) + optionName + QLatin1String(", "); } - QString optionNamesString = optionNames.join(QStringLiteral(", ")); - if (!option.valueName().isEmpty()) - optionNamesString += QStringLiteral(" <") + option.valueName() + QLatin1Char('>'); + if (!optionNames.isEmpty()) + optionNamesString.chop(2); // remove trailing ", " + const auto valueName = option.valueName(); + if (!valueName.isEmpty()) + optionNamesString += QLatin1String(" <") + valueName + QLatin1Char('>'); optionNameList.append(optionNamesString); longestOptionNameString = qMax(longestOptionNameString, optionNamesString.length()); } ++longestOptionNameString; + auto optionNameIterator = optionNameList.cbegin(); for (int i = 0; i < commandLineOptionList.count(); ++i) { const QCommandLineOption &option = commandLineOptionList.at(i); if (option.isHidden()) continue; - text += wrapText(optionNameList.at(i), longestOptionNameString, option.description()); + text += wrapText(*optionNameIterator, longestOptionNameString, option.description()); + ++optionNameIterator; } if (!positionalArgumentDefinitions.isEmpty()) { if (!commandLineOptionList.isEmpty()) |