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Export of internal Abseil changes.

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1f44f8f487aa3afe8248132e4081519e85671965 by CJ Johnson <johnsoncj@google.com>:

Updates ScopedAllocatorWorks test for InlinedVector to not depend on specific byte counts of standard library vectors. It's too brittle in the face of capacity-changing changes to InlinedVector and does not provide signal in those breakages.

PiperOrigin-RevId: 259590332

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fef7589547e9cdd04a254f6ae06e2bd9ec2b35f0 by CJ Johnson <johnsoncj@google.com>:

Updates the implementation of InlinedVector::insert(...) to be exception safe and adds an exception safety tests for insert(...)

PiperOrigin-RevId: 259542968
GitOrigin-RevId: 1f44f8f487aa3afe8248132e4081519e85671965
Change-Id: I514beff56159c9c717f8d29197728011af1fecd7
This commit is contained in:
Abseil Team 2019-07-23 12:42:09 -07:00 • committed by Andy Getz
parent f3840bc5e3
commit ad1485c898
4 changed files with 229 additions and 199 deletions
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168
absl/container/inlined_vector.h
View file

@ -549,15 +549,15 @@ class InlinedVector {
// of `v` starting at `pos`. Returns an `iterator` pointing to the first of
// the newly inserted elements.
iterator insert(const_iterator pos, size_type n, const_reference v) {
assert(pos >= begin() && pos <= end());
if (ABSL_PREDICT_FALSE(n == 0)) {
assert(pos >= begin());
assert(pos <= end());
if (ABSL_PREDICT_TRUE(n != 0)) {
value_type dealias = v;
return storage_.Insert(pos, CopyValueAdapter(dealias), n);
} else {
return const_cast<iterator>(pos);
}
value_type copy = v;
std::pair<iterator, iterator> it_pair = ShiftRight(pos, n);
std::fill(it_pair.first, it_pair.second, copy);
UninitializedFill(it_pair.second, it_pair.first + n, copy);
return it_pair.first;
}
// Overload of `InlinedVector::insert()` for copying the contents of the
@ -577,17 +577,15 @@ class InlinedVector {
EnableIfAtLeastForwardIterator<ForwardIterator>* = nullptr>
iterator insert(const_iterator pos, ForwardIterator first,
ForwardIterator last) {
assert(pos >= begin() && pos <= end());
if (ABSL_PREDICT_FALSE(first == last)) {
assert(pos >= begin());
assert(pos <= end());
if (ABSL_PREDICT_TRUE(first != last)) {
return storage_.Insert(pos, IteratorValueAdapter<ForwardIterator>(first),
std::distance(first, last));
} else {
return const_cast<iterator>(pos);
}
auto n = std::distance(first, last);
std::pair<iterator, iterator> it_pair = ShiftRight(pos, n);
size_type used_spots = it_pair.second - it_pair.first;
auto open_spot = std::next(first, used_spots);
std::copy(first, open_spot, it_pair.first);
UninitializedCopy(open_spot, last, it_pair.second);
return it_pair.first;
}
// Overload of `InlinedVector::insert()` for inserting elements constructed
@ -615,23 +613,12 @@ class InlinedVector {
iterator emplace(const_iterator pos, Args&&... args) {
assert(pos >= begin());
assert(pos <= end());
if (ABSL_PREDICT_FALSE(pos == end())) {
emplace_back(std::forward<Args>(args)...);
return end() - 1;
}
T new_t = T(std::forward<Args>(args)...);
auto range = ShiftRight(pos, 1);
if (range.first == range.second) {
// constructing into uninitialized memory
Construct(range.first, std::move(new_t));
} else {
// assigning into moved-from object
*range.first = T(std::move(new_t));
}
return range.first;
value_type dealias(std::forward<Args>(args)...);
return storage_.Insert(pos,
IteratorValueAdapter<MoveIterator>(
MoveIterator(std::addressof(dealias))),
1);
}
// `InlinedVector::emplace_back()`
@ -746,123 +733,6 @@ class InlinedVector {
template <typename H, typename TheT, size_t TheN, typename TheA>
friend H AbslHashValue(H h, const absl::InlinedVector<TheT, TheN, TheA>& a);
void ResetAllocation(pointer new_data, size_type new_capacity,
size_type new_size) {
if (storage_.GetIsAllocated()) {
Destroy(storage_.GetAllocatedData(),
storage_.GetAllocatedData() + size());
assert(begin() == storage_.GetAllocatedData());
AllocatorTraits::deallocate(*storage_.GetAllocPtr(),
storage_.GetAllocatedData(),
storage_.GetAllocatedCapacity());
} else {
Destroy(storage_.GetInlinedData(), storage_.GetInlinedData() + size());
}
storage_.SetAllocatedData(new_data, new_capacity);
storage_.SetAllocatedSize(new_size);
}
template <typename... Args>
reference Construct(pointer p, Args&&... args) {
absl::allocator_traits<allocator_type>::construct(
*storage_.GetAllocPtr(), p, std::forward<Args>(args)...);
return *p;
}
template <typename Iterator>
void UninitializedCopy(Iterator src, Iterator src_last, pointer dst) {
for (; src != src_last; ++dst, ++src) Construct(dst, *src);
}
template <typename... Args>
void UninitializedFill(pointer dst, pointer dst_last, const Args&... args) {
for (; dst != dst_last; ++dst) Construct(dst, args...);
}
// Destroy [`from`, `to`) in place.
void Destroy(pointer from, pointer to) {
for (pointer cur = from; cur != to; ++cur) {
absl::allocator_traits<allocator_type>::destroy(*storage_.GetAllocPtr(),
cur);
}
#if !defined(NDEBUG)
// Overwrite unused memory with `0xab` so we can catch uninitialized usage.
// Cast to `void*` to tell the compiler that we don't care that we might be
// scribbling on a vtable pointer.
if (from != to) {
auto len = sizeof(value_type) * std::distance(from, to);
std::memset(reinterpret_cast<void*>(from), 0xab, len);
}
#endif // !defined(NDEBUG)
}
// Shift all elements from `position` to `end()` by `n` places to the right.
// If the vector needs to be enlarged, memory will be allocated.
// Returns `iterator`s pointing to the start of the previously-initialized
// portion and the start of the uninitialized portion of the created gap.
// The number of initialized spots is `pair.second - pair.first`. The number
// of raw spots is `n - (pair.second - pair.first)`.
//
// Updates the size of the InlinedVector internally.
std::pair<iterator, iterator> ShiftRight(const_iterator position,
size_type n) {
iterator start_used = const_cast<iterator>(position);
iterator start_raw = const_cast<iterator>(position);
size_type s = size();
size_type required_size = s + n;
if (required_size > capacity()) {
// Compute new capacity by repeatedly doubling current capacity
size_type new_capacity = capacity();
while (new_capacity < required_size) {
new_capacity <<= 1;
}
// Move everyone into the new allocation, leaving a gap of `n` for the
// requested shift.
pointer new_data =
AllocatorTraits::allocate(*storage_.GetAllocPtr(), new_capacity);
size_type index = position - begin();
UninitializedCopy(std::make_move_iterator(data()),
std::make_move_iterator(data() + index), new_data);
UninitializedCopy(std::make_move_iterator(data() + index),
std::make_move_iterator(data() + s),
new_data + index + n);
ResetAllocation(new_data, new_capacity, s);
// New allocation means our iterator is invalid, so we'll recalculate.
// Since the entire gap is in new space, there's no used space to reuse.
start_raw = begin() + index;
start_used = start_raw;
} else {
// If we had enough space, it's a two-part move. Elements going into
// previously-unoccupied space need an `UninitializedCopy()`. Elements
// going into a previously-occupied space are just a `std::move()`.
iterator pos = const_cast<iterator>(position);
iterator raw_space = end();
size_type slots_in_used_space = raw_space - pos;
size_type new_elements_in_used_space = (std::min)(n, slots_in_used_space);
size_type new_elements_in_raw_space = n - new_elements_in_used_space;
size_type old_elements_in_used_space =
slots_in_used_space - new_elements_in_used_space;
UninitializedCopy(
std::make_move_iterator(pos + old_elements_in_used_space),
std::make_move_iterator(raw_space),
raw_space + new_elements_in_raw_space);
std::move_backward(pos, pos + old_elements_in_used_space, raw_space);
// If the gap is entirely in raw space, the used space starts where the
// raw space starts, leaving no elements in used space. If the gap is
// entirely in used space, the raw space starts at the end of the gap,
// leaving all elements accounted for within the used space.
start_used = pos;
start_raw = pos + new_elements_in_used_space;
}
storage_.AddSize(n);
return std::make_pair(start_used, start_raw);
}
Storage storage_;
};