Avoid unnecessary HashTable resizing during copy construction.
We do know the final table size, so reserve its size before starting
to copy over. Thereby avoiding intermediate table allocations.
R=esprehn
BUG=
Review-Url: https://codereview.chromium.org/2715473004
Cr-Commit-Position: refs/heads/master@{#452060}
diff --git a/third_party/WebKit/Source/wtf/HashTable.h b/third_party/WebKit/Source/wtf/HashTable.h
index dc707ef..2d9b5f8 100644
--- a/third_party/WebKit/Source/wtf/HashTable.h
+++ b/third_party/WebKit/Source/wtf/HashTable.h
@@ -1827,12 +1827,13 @@
m_stats(HashTableStatsPtr<Allocator>::copy(other.m_stats))
#endif
{
+ if (other.size())
+ reserveCapacityForSize(other.size());
// Copy the hash table the dumb way, by adding each element to the new
// table. It might be more efficient to copy the table slots, but it's not
// clear that efficiency is needed.
- const_iterator end = other.end();
- for (const_iterator it = other.begin(); it != end; ++it)
- add(*it);
+ for (const auto& element : other)
+ add(element);
}
template <typename Key,
