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QLocale: improve speed of 'applyIntegerFormatting()' 

This patch reduced the runtime of "QString::number(12345678)"
from 119ns to 84ns in one measurement. It removes one copy of a
QString into a local lambda function, it adds a std::move on
return, removing another QString instantiation and it removes
the usage of StringBuilder on return, which created another QString.

Task-number: QTBUG-87330
Change-Id: Ia37e314353c354ae04402cd482d0f7aeabbfc0cb
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
bb10
Andreas Buhr 2020-10-27 10:27:26 +01:00
parent 4c5c4c6d1c
commit e6cba05b66
1 changed files with 7 additions and 4 deletions
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11
src/corelib/text/qlocale.cpp
View File

@ -3578,7 +3578,7 @@ QString QLocaleData::applyIntegerFormatting(QString &&numStr, bool negative, int
const auto digitWidth = zero.size();
const auto digitCount = numStr.length() / digitWidth;
const auto basePrefix = [numStr, zero, base, flags] () -> QStringView {
const auto basePrefix = [&] () -> QStringView {
if (flags & ShowBase) {
const bool upper = flags & UppercaseBase;
if (base == 16)
@ -3589,9 +3589,9 @@ QString QLocaleData::applyIntegerFormatting(QString &&numStr, bool negative, int
return zero;
}
return {};
};
}();
const QString prefix = signPrefix(negative, flags) + basePrefix();
const QString prefix = signPrefix(negative, flags) + basePrefix;
// Count how much of width we've used up. Each digit counts as one
int usedWidth = digitCount + prefix.size();
@ -3625,7 +3625,10 @@ QString QLocaleData::applyIntegerFormatting(QString &&numStr, bool negative, int
numStr.prepend(zero);
}
return prefix + (flags & CapitalEorX ? std::move(numStr).toUpper() : numStr);
QString result(flags & CapitalEorX ? std::move(numStr).toUpper() : std::move(numStr));
if (prefix.size())
result.prepend(prefix);
return result;
}
/*