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AK+LibUnicode: Implement String::equals_ignoring_case without allocating

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We currently fully casefold the left- and right-hand sides to compare
two strings with case-insensitivity. Now, we casefold one code point at
a time, storing the result in a view for comparison, until we exhaust
both strings.
This commit is contained in:
Timothy Flynn 2023-03-08 13:03:04 -05:00 • committed by Linus Groh
parent 4aee4e80bd
commit 1393ed2000
6 changed files with 150 additions and 52 deletions
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37
Userland/Libraries/LibUnicode/UnicodeUtils.cpp
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@ -330,31 +330,32 @@ ErrorOr<void> build_titlecase_string([[maybe_unused]] Utf8View code_points, [[ma
}
// https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G53253
ErrorOr<void> build_casefold_string([[maybe_unused]] Utf8View code_points, [[maybe_unused]] StringBuilder& builder)
ErrorOr<void> build_casefold_string(Utf8View code_points, StringBuilder& builder)
{
#if ENABLE_UNICODE_DATA
// toCasefold(X): Map each character C in X to Case_Folding(C).
//
// Case_Folding(C) uses the mappings with the status field value “C” or “F” in the data file
// CaseFolding.txt in the Unicode Character Database.
using enum CaseFoldingStatus;
for (auto code_point : code_points) {
auto const* case_folding = find_matching_case_folding<Common, Full>(code_point);
if (!case_folding) {
TRY(builder.try_append_code_point(code_point));
continue;
}
for (size_t i = 0; i < case_folding->mapping_size; ++i)
TRY(builder.try_append_code_point(case_folding->mapping[i]));
auto case_folding = casefold_code_point(code_point);
TRY(builder.try_append(case_folding));
}
return {};
#else
return Error::from_string_literal("Unicode data has been disabled");
}
// https://www.unicode.org/reports/tr44/#CaseFolding.txt
// https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G53253
Utf32View casefold_code_point(u32 const& code_point)
{
#if ENABLE_UNICODE_DATA
// Case_Folding(C) uses the mappings with the status field value “C” or “F” in the data file
// CaseFolding.txt in the Unicode Character Database.
using enum CaseFoldingStatus;
if (auto const* case_folding = find_matching_case_folding<Common, Full>(code_point))
return Utf32View { case_folding->mapping, case_folding->mapping_size };
#endif
// The case foldings are omitted in the data file if they are the same as the code point itself.
return Utf32View { &code_point, 1 };
}
}