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[libc++][NFC] Refactor __do_rehash a bit #151543

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Aug 1, 2025
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[libc++][NFC] Refactor __do_rehash a bit #151543

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72 changes: 38 additions & 34 deletions libcxx/include/__hash_table
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Original file line number Diff line number Diff line change
Expand Up @@ -1709,41 +1709,45 @@ void __hash_table<_Tp, _Hash, _Equal, _Alloc>::__rehash(size_type __n) _LIBCPP_D

template <class _Tp, class _Hash, class _Equal, class _Alloc>
template <bool _UniqueKeys>
void __hash_table<_Tp, _Hash, _Equal, _Alloc>::__do_rehash(size_type __nbc) {
__pointer_allocator& __npa = __bucket_list_.get_deleter().__alloc();
__bucket_list_.reset(__nbc > 0 ? __pointer_alloc_traits::allocate(__npa, __nbc) : nullptr);
__bucket_list_.get_deleter().size() = __nbc;
if (__nbc > 0) {
for (size_type __i = 0; __i < __nbc; ++__i)
__bucket_list_[__i] = nullptr;
__next_pointer __pp = __first_node_.__ptr();
__next_pointer __cp = __pp->__next_;
if (__cp != nullptr) {
size_type __chash = std::__constrain_hash(__cp->__hash(), __nbc);
__bucket_list_[__chash] = __pp;
size_type __phash = __chash;
for (__pp = __cp, void(), __cp = __cp->__next_; __cp != nullptr; __cp = __pp->__next_) {
__chash = std::__constrain_hash(__cp->__hash(), __nbc);
if (__chash == __phash)
__pp = __cp;
else {
if (__bucket_list_[__chash] == nullptr) {
__bucket_list_[__chash] = __pp;
__pp = __cp;
__phash = __chash;
} else {
__next_pointer __np = __cp;
if _LIBCPP_CONSTEXPR_SINCE_CXX17 (!_UniqueKeys) {
for (; __np->__next_ != nullptr &&
key_eq()(__cp->__upcast()->__get_value(), __np->__next_->__upcast()->__get_value());
__np = __np->__next_)
;
}
__pp->__next_ = __np->__next_;
__np->__next_ = __bucket_list_[__chash]->__next_;
__bucket_list_[__chash]->__next_ = __cp;
}
void __hash_table<_Tp, _Hash, _Equal, _Alloc>::__do_rehash(size_type __bucket_count) {
__pointer_allocator& __ptr_alloc = __bucket_list_.get_deleter().__alloc();
__bucket_list_.reset(__bucket_count > 0 ? __pointer_alloc_traits::allocate(__ptr_alloc, __bucket_count) : nullptr);
__bucket_list_.get_deleter().size() = __bucket_count;

if (__bucket_count == 0)
return;

for (size_type __i = 0; __i < __bucket_count; ++__i)
__bucket_list_[__i] = nullptr;
__next_pointer __pp = __first_node_.__ptr();
__next_pointer __cp = __pp->__next_;

if (!__cp)
return;

size_type __chash = std::__constrain_hash(__cp->__hash(), __bucket_count);
__bucket_list_[__chash] = __pp;
size_type __phash = __chash;
for (__pp = __cp, void(), __cp = __cp->__next_; __cp != nullptr; __cp = __pp->__next_) {
__chash = std::__constrain_hash(__cp->__hash(), __bucket_count);
if (__chash == __phash)
__pp = __cp;
else {
if (__bucket_list_[__chash] == nullptr) {
__bucket_list_[__chash] = __pp;
__pp = __cp;
__phash = __chash;
} else {
__next_pointer __np = __cp;
if _LIBCPP_CONSTEXPR (!_UniqueKeys) {
for (; __np->__next_ != nullptr &&
key_eq()(__cp->__upcast()->__get_value(), __np->__next_->__upcast()->__get_value());
__np = __np->__next_)
;
}
__pp->__next_ = __np->__next_;
__np->__next_ = __bucket_list_[__chash]->__next_;
__bucket_list_[__chash]->__next_ = __cp;
}
}
}
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