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XPath: Refactor xpath_node_set short buffer optimization

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This change replaces xpath_node_set single element storage with a
single-element array in hopes that this would silence Coverity false
positive about getting a singleton pointer.

Additionally, it refactors _assign member to unify small and large
buffer codepaths since they are basically identical.

Fixes #233 (hopefully)
This commit is contained in:
Arseny Kapoulkine 2018-09-24 20:18:12 -07:00
parent 1a96777b11
commit e3b5e9ce3c
2 changed files with 28 additions and 41 deletions
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67
src/pugixml.cpp
View File

@ -12013,74 +12013,61 @@ namespace pugi
size_t size_ = static_cast<size_t>(end_ - begin_);
if (size_ <= 1)
// use internal buffer for 0 or 1 elements, heap buffer otherwise
xpath_node* storage = (size_ <= 1) ? _storage : static_cast<xpath_node*>(impl::xml_memory::allocate(size_ * sizeof(xpath_node)));
if (!storage)
{
// deallocate old buffer
if (_begin != &_storage) impl::xml_memory::deallocate(_begin);
// use internal buffer
if (begin_ != end_) _storage = *begin_;
_begin = &_storage;
_end = &_storage + size_;
_type = type_;
#ifdef PUGIXML_NO_EXCEPTIONS
return;
#else
throw std::bad_alloc();
#endif
}
else
{
// make heap copy
xpath_node* storage = static_cast<xpath_node*>(impl::xml_memory::allocate(size_ * sizeof(xpath_node)));
if (!storage)
{
#ifdef PUGIXML_NO_EXCEPTIONS
return;
#else
throw std::bad_alloc();
#endif
}
// deallocate old buffer
if (_begin != _storage)
impl::xml_memory::deallocate(_begin);
// size check is necessary because for begin_ = end_ = nullptr, memcpy is UB
if (size_)
memcpy(storage, begin_, size_ * sizeof(xpath_node));
// deallocate old buffer
if (_begin != &_storage) impl::xml_memory::deallocate(_begin);
// finalize
_begin = storage;
_end = storage + size_;
_type = type_;
}
_begin = storage;
_end = storage + size_;
_type = type_;
}
#ifdef PUGIXML_HAS_MOVE
PUGI__FN void xpath_node_set::_move(xpath_node_set& rhs) PUGIXML_NOEXCEPT
{
_type = rhs._type;
_storage = rhs._storage;
_begin = (rhs._begin == &rhs._storage) ? &_storage : rhs._begin;
_storage[0] = rhs._storage[0];
_begin = (rhs._begin == rhs._storage) ? _storage : rhs._begin;
_end = _begin + (rhs._end - rhs._begin);
rhs._type = type_unsorted;
rhs._begin = &rhs._storage;
rhs._end = rhs._begin;
rhs._begin = rhs._storage;
rhs._end = rhs._storage;
}
#endif
PUGI__FN xpath_node_set::xpath_node_set(): _type(type_unsorted), _begin(&_storage), _end(&_storage)
PUGI__FN xpath_node_set::xpath_node_set(): _type(type_unsorted), _begin(_storage), _end(_storage)
{
}
PUGI__FN xpath_node_set::xpath_node_set(const_iterator begin_, const_iterator end_, type_t type_): _type(type_unsorted), _begin(&_storage), _end(&_storage)
PUGI__FN xpath_node_set::xpath_node_set(const_iterator begin_, const_iterator end_, type_t type_): _type(type_unsorted), _begin(_storage), _end(_storage)
{
_assign(begin_, end_, type_);
}
PUGI__FN xpath_node_set::~xpath_node_set()
{
if (_begin != &_storage)
if (_begin != _storage)
impl::xml_memory::deallocate(_begin);
}
PUGI__FN xpath_node_set::xpath_node_set(const xpath_node_set& ns): _type(type_unsorted), _begin(&_storage), _end(&_storage)
PUGI__FN xpath_node_set::xpath_node_set(const xpath_node_set& ns): _type(type_unsorted), _begin(_storage), _end(_storage)
{
_assign(ns._begin, ns._end, ns._type);
}
@ -12095,7 +12082,7 @@ namespace pugi
}
#ifdef PUGIXML_HAS_MOVE
PUGI__FN xpath_node_set::xpath_node_set(xpath_node_set&& rhs) PUGIXML_NOEXCEPT: _type(type_unsorted), _begin(&_storage), _end(&_storage)
PUGI__FN xpath_node_set::xpath_node_set(xpath_node_set&& rhs) PUGIXML_NOEXCEPT: _type(type_unsorted), _begin(_storage), _end(_storage)
{
_move(rhs);
}
@ -12104,7 +12091,7 @@ namespace pugi
{
if (this == &rhs) return *this;
if (_begin != &_storage)
if (_begin != _storage)
impl::xml_memory::deallocate(_begin);
_move(rhs);

2
src/pugixml.hpp
View File

@ -1372,7 +1372,7 @@ namespace pugi
private:
type_t _type;
xpath_node _storage;
xpath_node _storage[1];
xpath_node* _begin;
xpath_node* _end;