svl/source/items/itemset.cxx | 29 ++++++++++++++++++-----------
1 file changed, 18 insertions(+), 11 deletions(-)
New commits:
commit aa85b303cde517e187a7c3404f9b63f0a0752bf3
Author: Noel Grandin <noel.gran...@collabora.co.uk>
AuthorDate: Fri Feb 18 11:54:37 2022 +0200
Commit: Noel Grandin <noel.gran...@collabora.co.uk>
CommitDate: Fri Feb 18 12:15:43 2022 +0100
avoid an allocation in WhichRangesContainer::MergeRange
speeds up loading a large chart by 5%
Change-Id: Idd8566012a0049d429e38b589782fc6d76eb3a5a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/130132
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.gran...@collabora.co.uk>
diff --git a/svl/source/items/itemset.cxx b/svl/source/items/itemset.cxx
index bfaf0a60e169..7953cd922363 100644
--- a/svl/source/items/itemset.cxx
+++ b/svl/source/items/itemset.cxx
@@ -1478,46 +1478,53 @@ WhichRangesContainer
WhichRangesContainer::MergeRange(sal_uInt16 nFrom,
// create vector of ranges (sal_uInt16 pairs of lower and upper bound)
const size_t nOldCount = size();
- std::vector<WhichPair> aRangesTable;
- aRangesTable.reserve(nOldCount);
+ // Allocate one item more than we already have.
+ // In the worst case scenario we waste a little bit
+ // of memory, but we avoid another allocation, which is more important.
+ std::unique_ptr<WhichPair[]> aRangesTable(new WhichPair[nOldCount+1]);
+ int aRangesTableSize = 0;
bool bAdded = false;
for (const auto& rPair : *this)
{
if (!bAdded && rPair.first >= nFrom)
{ // insert new range, keep ranges sorted
- aRangesTable.push_back({ nFrom, nTo });
+ aRangesTable[aRangesTableSize++] = { nFrom, nTo };
bAdded = true;
}
// insert current range
- aRangesTable.emplace_back(rPair);
+ aRangesTable[aRangesTableSize++] = rPair;
}
if (!bAdded)
- aRangesTable.push_back({ nFrom, nTo });
+ aRangesTable[aRangesTableSize++] = { nFrom, nTo };
// true if ranges overlap or adjoin, false if ranges are separate
auto needMerge = [](WhichPair lhs, WhichPair rhs) {
return (lhs.first - 1) <= rhs.second && (rhs.first - 1) <= lhs.second;
};
- auto it = aRangesTable.begin();
- // we got at least one range
+ auto it = aRangesTable.get();
+ auto endIt = aRangesTable.get() + aRangesTableSize;
+ // we have at least one range at this point
for (;;)
{
auto itNext = std::next(it);
- if (itNext == aRangesTable.end())
+ if (itNext == endIt)
break;
- // check neighbouring ranges, find first range which overlaps or
adjoins a previous range
+ // check if neighbouring ranges overlap or adjoin
if (needMerge(*it, *itNext))
{
// lower bounds are sorted, implies: it->first = min(it[0].first,
it[1].first)
it->second = std::max(it->second, itNext->second);
- aRangesTable.erase(itNext);
+ // remove next element
+ std::move(std::next(itNext), endIt, itNext);
+ --aRangesTableSize;
+ endIt = aRangesTable.get() + aRangesTableSize;
}
else
++it;
}
- return WhichRangesContainer(aRangesTable.data(), aRangesTable.size());
+ return WhichRangesContainer(std::move(aRangesTable), aRangesTableSize);
}
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
