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Avoid redundant work when processing UTF-8 strings (#4475)

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Victor Chernyakin
2025-06-20 06:39:06 -07:00
committed by GitHub
parent 730fd4d9a7
commit 067bc479b4
1 changed files with 6 additions and 24 deletions
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30
include/fmt/format.h
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@ -696,26 +696,6 @@ FMT_CONSTEXPR inline auto compute_width(string_view s) -> size_t {
return num_code_points; return num_code_points;
} }
template <typename Char>
inline auto code_point_index(basic_string_view<Char> s, size_t n) -> size_t {
return min_of(n, s.size());
}
// Calculates the index of the nth code point in a UTF-8 string.
inline auto code_point_index(string_view s, size_t n) -> size_t {
size_t result = s.size();
const char* begin = s.begin();
for_each_codepoint(s, [begin, &n, &result](uint32_t, string_view sv) {
if (n != 0) {
--n;
return true;
}
result = to_unsigned(sv.begin() - begin);
return false;
});
return result;
}
template <typename T> struct is_integral : std::is_integral<T> {}; template <typename T> struct is_integral : std::is_integral<T> {};
template <> struct is_integral<int128_opt> : std::true_type {}; template <> struct is_integral<int128_opt> : std::true_type {};
template <> struct is_integral<uint128_t> : std::true_type {}; template <> struct is_integral<uint128_t> : std::true_type {};
@ -2150,15 +2130,17 @@ FMT_CONSTEXPR FMT_INLINE auto write(OutputIt out, T value,
inline auto convert_precision_to_size(string_view s, size_t precision) inline auto convert_precision_to_size(string_view s, size_t precision)
-> size_t { -> size_t {
size_t display_width = 0; size_t display_width = 0;
size_t num_code_points = 0; size_t result = s.size();
for_each_codepoint(s, [&](uint32_t, string_view sv) { for_each_codepoint(s, [&](uint32_t, string_view sv) {
display_width += compute_width(sv); display_width += compute_width(sv);
// Stop when display width exceeds precision. // Stop when display width exceeds precision.
if (display_width > precision) return false; if (display_width > precision) {
++num_code_points; result = to_unsigned(sv.begin() - s.begin());
return false;
}
return true; return true;
}); });
return code_point_index(s, num_code_points); return result;
} }
template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)> template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>