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Add resize_and_overwrite #53

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53 changes: 53 additions & 0 deletions include/ankerl/svector.h
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Original file line number Diff line number Diff line change
Expand Up @@ -928,6 +928,59 @@ class svector {
return insert(pos, l.begin(), l.end());
}

template< class Operation >
constexpr void resize_and_overwrite(size_t count, Operation op) {
auto direct = is_direct();

auto current_data = data<direction::direct>();
size_t current_size = size<direction::direct>();
size_t current_capacity = capacity<direction::direct>();

if (!direct) {
current_data = data<direction::indirect>();
current_size = size<direction::indirect>();
current_capacity = capacity<direction::indirect>();
}

auto new_data = current_data;

if (count <= current_size) {
// destroy the trailing elements?
std::destroy_n(new_data + count, current_size - count);
} else if (count > current_capacity) {
// put everything into indirect storage
auto new_capacity = calculate_new_capacity(count, current_capacity);
auto storage = detail::storage<T>::alloc(new_capacity);
// step 1: https://en.cppreference.com/w/cpp/string/basic_string/resize_and_overwrite
// count is strictly >= the current size, move the data over to the new allocation
uninitialized_move_and_destroy(current_data, storage->data(), current_size);

if (!direct) { // cleanup if the old storage was indirect
auto* storage_direct = indirect();
std::destroy_at(storage_direct);
::operator delete(storage_direct);
}
// treat the newly allocated storage as part of this svector
set_indirect(storage);
new_data = storage->data();

// step 2 & 3: perform the target operation and reset the size
size_t new_size = op(new_data, current_size);
set_size<direction::indirect>(new_size);
return;
} else {
// should be ok to reuse the current data
}

// step 2 & 3: perform the target operation and reset the size
size_t new_size = op(new_data, current_size);
if (direct) {
set_size<direction::direct>(new_size);
} else {
set_size<direction::indirect>(new_size);
}
}

auto erase(const_iterator pos) -> iterator {
return erase(pos, pos + 1);
}
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