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Optimize misc::naturalSort()

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Previous implementation used QRegExp to find a first digit. That is
utterly ineffective.

When torrent list is sorted by name (a column that uses the naturalSort() for
comparison), naturalSort could take 18.6% of the time of the UI thread. Optimize it
so now it takes 1% of the time of the UI thread.
This commit is contained in:
Ivan Sorokin 2014-10-18 01:29:23 +04:00
parent f9dc945730
commit a278261806
1 changed files with 22 additions and 10 deletions
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32
src/misc.cpp
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@ -541,15 +541,29 @@ QString misc::toQString(time_t t)
bool misc::naturalSort(QString left, QString right, bool &result) { // uses lessThan comparison
// Return value indicates if functions was successful
// result argument will contain actual comparison result if function was successful
int posL = 0;
int posR = 0;
do {
int posL = left.indexOf(QRegExp("[0-9]"));
int posR = right.indexOf(QRegExp("[0-9]"));
if (posL == -1 || posR == -1)
break; // No data
else if (posL != posR)
break; // Digit positions mismatch
else if (left.left(posL) != right.left(posR))
break; // Strings' subsets before digit do not match
for (;;) {
if (posL == left.size() || posR == right.size())
return false; // No data
QChar leftChar = left.at(posL);
QChar rightChar = right.at(posR);
bool leftCharIsDigit = leftChar.isDigit();
bool rightCharIsDigit = rightChar.isDigit();
if (leftCharIsDigit != rightCharIsDigit)
return false; // Digit positions mismatch
if (leftCharIsDigit)
break; // Both are digit, break this loop and compare numbers
if (leftChar != rightChar)
return false; // Strings' subsets before digit do not match
++posL;
++posR;
}
QString temp;
while (posL < left.size()) {
@ -578,8 +592,6 @@ bool misc::naturalSort(QString left, QString right, bool &result) { // uses less
// Strings + digits do match and we haven't hit string end
// Do another round
left.remove(0, posL);
right.remove(0, posR);
} while (true);