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[libc++] Simplify the implementation of string::{append,assign,assign_range} #162254

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[libc++] Simplify the implementation of string::{append,assign,assign_range} #162254

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28 changes: 6 additions & 22 deletions libcxx/include/string
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Original file line number Diff line number Diff line change
Expand Up @@ -1413,24 +1413,16 @@ public:
_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& append(const value_type* _LIBCPP_DIAGNOSE_NULLPTR __s);
_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& append(size_type __n, value_type __c);
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Can we add a comment explaining what __string_is_trivial_iterator_v represents? It was introduced in https://reviews.llvm.org/D98573.


template <class _InputIterator, __enable_if_t<__has_exactly_input_iterator_category<_InputIterator>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string&
append(_InputIterator __first, _InputIterator __last) {
const basic_string __temp(__first, __last, __alloc_);
append(__temp.data(), __temp.size());
return *this;
}

template <class _ForwardIterator, __enable_if_t<__has_forward_iterator_category<_ForwardIterator>::value, int> = 0>
template <class _InputIterator>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string&
append(_ForwardIterator __first, _ForwardIterator __last) {
append(_InputIterator __first, _InputIterator __last) {
size_type __sz = size();
size_type __cap = capacity();
size_type __n = static_cast<size_type>(std::distance(__first, __last));
if (__n == 0)
return *this;
Comment on lines 1421 to 1423
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This needs to move into the if, or disappear entirely.


if (__string_is_trivial_iterator_v<_ForwardIterator> && !__addr_in_range(*__first)) {
if (__string_is_trivial_iterator_v<_InputIterator> && !__addr_in_range(*__first)) {
if (__cap - __sz < __n)
__grow_by_without_replace(__cap, __sz + __n - __cap, __sz, __sz, 0);
__annotate_increase(__n);
Comment on lines 1427 to 1428
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I guess this could be something like

string __tmp;
__tmp.reserve(__sz + __n);
__tmp.assign(begin(), end());
__tmp.insert(__tmp.end(), __first, __last);
swap(*this, __tmp);

And then we don't have to care about __addr_in_range(*__first) anymore. That's basically the algorithm that we do in vector as well.

This can be done in a follow-up patch.

Expand Down Expand Up @@ -1540,17 +1532,10 @@ public:
_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& assign(const value_type* _LIBCPP_DIAGNOSE_NULLPTR __s);
_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& assign(size_type __n, value_type __c);

template <class _InputIterator, __enable_if_t<__has_exactly_input_iterator_category<_InputIterator>::value, int> = 0>
template <class _InputIterator>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string&
assign(_InputIterator __first, _InputIterator __last) {
__assign_with_sentinel(__first, __last);
return *this;
}

template <class _ForwardIterator, __enable_if_t<__has_forward_iterator_category<_ForwardIterator>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string&
assign(_ForwardIterator __first, _ForwardIterator __last) {
if (__string_is_trivial_iterator_v<_ForwardIterator>) {
if _LIBCPP_CONSTEXPR (__string_is_trivial_iterator_v<_InputIterator>) {
size_type __n = static_cast<size_type>(std::distance(__first, __last));
__assign_trivial(__first, __last, __n);
} else {
Expand All @@ -1563,8 +1548,7 @@ public:
# if _LIBCPP_STD_VER >= 23
template <_ContainerCompatibleRange<_CharT> _Range>
_LIBCPP_HIDE_FROM_ABI constexpr basic_string& assign_range(_Range&& __range) {
if constexpr (__string_is_trivial_iterator_v<ranges::iterator_t<_Range>> &&
(ranges::forward_range<_Range> || ranges::sized_range<_Range>)) {
if constexpr (__string_is_trivial_iterator_v<ranges::iterator_t<_Range>>) {
size_type __n = static_cast<size_type>(ranges::distance(__range));
__assign_trivial(ranges::begin(__range), ranges::end(__range), __n);

Expand Down
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