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Speed up iterator_buffer (#4679)

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user202729 2026-03-25 22:38:47 +08:00 committed by GitHub
parent dc05bee307
commit 7b2c4d064b
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2 changed files with 65 additions and 60 deletions
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66
include/fmt/base.h
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@ -1858,6 +1858,65 @@ class fixed_buffer_traits {
}
};
template <typename OutputIt, typename InputIt, typename = void>
struct has_back_insert_iterator_container_append : std::false_type {};
template <typename OutputIt, typename InputIt>
struct has_back_insert_iterator_container_append<
OutputIt, InputIt,
void_t<decltype(get_container(std::declval<OutputIt>())
.append(std::declval<InputIt>(),
std::declval<InputIt>()))>> : std::true_type {};
template <typename OutputIt, typename InputIt, typename = void>
struct has_back_insert_iterator_container_insert_at_end : std::false_type {};
template <typename OutputIt, typename InputIt>
struct has_back_insert_iterator_container_insert_at_end<
OutputIt, InputIt,
void_t<decltype(get_container(std::declval<OutputIt>())
.insert(get_container(std::declval<OutputIt>()).end(),
std::declval<InputIt>(),
std::declval<InputIt>()))>> : std::true_type {};
// An optimized version of std::copy with the output value type (T).
template <typename T, typename InputIt, typename OutputIt,
FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value&&
has_back_insert_iterator_container_append<
OutputIt, InputIt>::value)>
FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
get_container(out).append(begin, end);
return out;
}
template <typename T, typename InputIt, typename OutputIt,
FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value &&
!has_back_insert_iterator_container_append<
OutputIt, InputIt>::value &&
has_back_insert_iterator_container_insert_at_end<
OutputIt, InputIt>::value)>
FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
auto& c = get_container(out);
c.insert(c.end(), begin, end);
return out;
}
template <typename T, typename InputIt, typename OutputIt,
FMT_ENABLE_IF(!(is_back_insert_iterator<OutputIt>::value &&
(has_back_insert_iterator_container_append<
OutputIt, InputIt>::value ||
has_back_insert_iterator_container_insert_at_end<
OutputIt, InputIt>::value)))>
FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
while (begin != end) *out++ = static_cast<T>(*begin++);
return out;
}
template <typename T, typename V, typename OutputIt>
FMT_CONSTEXPR auto copy(basic_string_view<V> s, OutputIt out) -> OutputIt {
return copy<T>(s.begin(), s.end(), out);
}
// A buffer that writes to an output iterator when flushed.
template <typename OutputIt, typename T, typename Traits = buffer_traits>
class iterator_buffer : public Traits, public buffer<T> {
@ -1875,7 +1934,12 @@ class iterator_buffer : public Traits, public buffer<T> {
this->clear();
const T* begin = data_;
const T* end = begin + this->limit(size);
while (begin != end) *out_++ = *begin++;
#if defined(__cpp_if_constexpr)
if constexpr (std::is_move_assignable<OutputIt>::value)
out_ = copy<T>(begin, end, out_);
else
#endif
while (begin != end) *out_++ = *begin++;
}
public:

59
include/fmt/format.h
View File

@ -548,65 +548,6 @@ FMT_CONSTEXPR20 auto fill_n(T* out, Size count, char value) -> T* {
return out + count;
}
template <typename OutputIt, typename InputIt, typename = void>
struct has_back_insert_iterator_container_append : std::false_type {};
template <typename OutputIt, typename InputIt>
struct has_back_insert_iterator_container_append<
OutputIt, InputIt,
void_t<decltype(get_container(std::declval<OutputIt>())
.append(std::declval<InputIt>(),
std::declval<InputIt>()))>> : std::true_type {};
template <typename OutputIt, typename InputIt, typename = void>
struct has_back_insert_iterator_container_insert_at_end : std::false_type {};
template <typename OutputIt, typename InputIt>
struct has_back_insert_iterator_container_insert_at_end<
OutputIt, InputIt,
void_t<decltype(get_container(std::declval<OutputIt>())
.insert(get_container(std::declval<OutputIt>()).end(),
std::declval<InputIt>(),
std::declval<InputIt>()))>> : std::true_type {};
// An optimized version of std::copy with the output value type (T).
template <typename T, typename InputIt, typename OutputIt,
FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value&&
has_back_insert_iterator_container_append<
OutputIt, InputIt>::value)>
FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
get_container(out).append(begin, end);
return out;
}
template <typename T, typename InputIt, typename OutputIt,
FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value &&
!has_back_insert_iterator_container_append<
OutputIt, InputIt>::value &&
has_back_insert_iterator_container_insert_at_end<
OutputIt, InputIt>::value)>
FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
auto& c = get_container(out);
c.insert(c.end(), begin, end);
return out;
}
template <typename T, typename InputIt, typename OutputIt,
FMT_ENABLE_IF(!(is_back_insert_iterator<OutputIt>::value &&
(has_back_insert_iterator_container_append<
OutputIt, InputIt>::value ||
has_back_insert_iterator_container_insert_at_end<
OutputIt, InputIt>::value)))>
FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
while (begin != end) *out++ = static_cast<T>(*begin++);
return out;
}
template <typename T, typename V, typename OutputIt>
FMT_CONSTEXPR auto copy(basic_string_view<V> s, OutputIt out) -> OutputIt {
return copy<T>(s.begin(), s.end(), out);
}
template <typename OutChar, typename InputIt, typename OutputIt>
FMT_CONSTEXPR FMT_NOINLINE auto copy_noinline(InputIt begin, InputIt end,
OutputIt out) -> OutputIt {