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AK+LibUnicode: Implement String::equals_ignoring_case without allocating

Browse source 
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
Notes: sideshowbarker 2024-07-17 07:16:27 +09:00
6 changed files with 150 additions and 52 deletions
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2
AK/String.h
View file

@ -109,7 +109,7 @@ public:
ErrorOr<String> to_casefold() const;
// Compare this String against another string with caseless matching. Using this method requires linking LibUnicode into your application.
ErrorOr<bool> equals_ignoring_case(String const&) const;
[[nodiscard]] bool equals_ignoring_case(String const&) const;
[[nodiscard]] bool starts_with(u32 code_point) const;
[[nodiscard]] bool starts_with_bytes(StringView) const;

105
Tests/AK/TestString.cpp
View file

@ -330,25 +330,33 @@ TEST_CASE(equals_ignoring_case)
String string1 {};
String string2 {};
EXPECT(MUST(string1.equals_ignoring_case(string2)));
EXPECT(string1.equals_ignoring_case(string2));
}
{
auto string1 = MUST("abcd"_string);
auto string2 = MUST("ABCD"_string);
auto string3 = MUST("AbCd"_string);
auto string4 = MUST("dcba"_string);
auto string5 = MUST("abce"_string);
auto string6 = MUST("abc"_string);
EXPECT(MUST(string1.equals_ignoring_case(string2)));
EXPECT(MUST(string1.equals_ignoring_case(string3)));
EXPECT(!MUST(string1.equals_ignoring_case(string4)));
EXPECT(string1.equals_ignoring_case(string2));
EXPECT(string1.equals_ignoring_case(string3));
EXPECT(!string1.equals_ignoring_case(string4));
EXPECT(!string1.equals_ignoring_case(string5));
EXPECT(!string1.equals_ignoring_case(string6));
EXPECT(MUST(string2.equals_ignoring_case(string1)));
EXPECT(MUST(string2.equals_ignoring_case(string3)));
EXPECT(!MUST(string2.equals_ignoring_case(string4)));
EXPECT(string2.equals_ignoring_case(string1));
EXPECT(string2.equals_ignoring_case(string3));
EXPECT(!string2.equals_ignoring_case(string4));
EXPECT(!string2.equals_ignoring_case(string5));
EXPECT(!string2.equals_ignoring_case(string6));
EXPECT(MUST(string3.equals_ignoring_case(string1)));
EXPECT(MUST(string3.equals_ignoring_case(string2)));
EXPECT(!MUST(string3.equals_ignoring_case(string4)));
EXPECT(string3.equals_ignoring_case(string1));
EXPECT(string3.equals_ignoring_case(string2));
EXPECT(!string3.equals_ignoring_case(string4));
EXPECT(!string3.equals_ignoring_case(string5));
EXPECT(!string3.equals_ignoring_case(string6));
}
{
auto string1 = MUST("\u00DF"_string); // LATIN SMALL LETTER SHARP S
@ -358,29 +366,66 @@ TEST_CASE(equals_ignoring_case)
auto string5 = MUST("S"_string);
auto string6 = MUST("s"_string);
EXPECT(MUST(string1.equals_ignoring_case(string2)));
EXPECT(MUST(string1.equals_ignoring_case(string3)));
EXPECT(MUST(string1.equals_ignoring_case(string4)));
EXPECT(!MUST(string1.equals_ignoring_case(string5)));
EXPECT(!MUST(string1.equals_ignoring_case(string6)));
EXPECT(string1.equals_ignoring_case(string2));
EXPECT(string1.equals_ignoring_case(string3));
EXPECT(string1.equals_ignoring_case(string4));
EXPECT(!string1.equals_ignoring_case(string5));
EXPECT(!string1.equals_ignoring_case(string6));
EXPECT(MUST(string2.equals_ignoring_case(string1)));
EXPECT(MUST(string2.equals_ignoring_case(string3)));
EXPECT(MUST(string2.equals_ignoring_case(string4)));
EXPECT(!MUST(string2.equals_ignoring_case(string5)));
EXPECT(!MUST(string2.equals_ignoring_case(string6)));
EXPECT(string2.equals_ignoring_case(string1));
EXPECT(string2.equals_ignoring_case(string3));
EXPECT(string2.equals_ignoring_case(string4));
EXPECT(!string2.equals_ignoring_case(string5));
EXPECT(!string2.equals_ignoring_case(string6));
EXPECT(MUST(string3.equals_ignoring_case(string1)));
EXPECT(MUST(string3.equals_ignoring_case(string2)));
EXPECT(MUST(string3.equals_ignoring_case(string4)));
EXPECT(!MUST(string3.equals_ignoring_case(string5)));
EXPECT(!MUST(string3.equals_ignoring_case(string6)));
EXPECT(string3.equals_ignoring_case(string1));
EXPECT(string3.equals_ignoring_case(string2));
EXPECT(string3.equals_ignoring_case(string4));
EXPECT(!string3.equals_ignoring_case(string5));
EXPECT(!string3.equals_ignoring_case(string6));
EXPECT(MUST(string4.equals_ignoring_case(string1)));
EXPECT(MUST(string4.equals_ignoring_case(string2)));
EXPECT(MUST(string4.equals_ignoring_case(string3)));
EXPECT(!MUST(string4.equals_ignoring_case(string5)));
EXPECT(!MUST(string4.equals_ignoring_case(string6)));
EXPECT(string4.equals_ignoring_case(string1));
EXPECT(string4.equals_ignoring_case(string2));
EXPECT(string4.equals_ignoring_case(string3));
EXPECT(!string4.equals_ignoring_case(string5));
EXPECT(!string4.equals_ignoring_case(string6));
}
{
auto string1 = MUST("Ab\u00DFCd\u00DFeF"_string);
auto string2 = MUST("ABSSCDSSEF"_string);
auto string3 = MUST("absscdssef"_string);
auto string4 = MUST("aBSscDsSEf"_string);
auto string5 = MUST("Ab\u00DFCd\u00DFeg"_string);
auto string6 = MUST("Ab\u00DFCd\u00DFe"_string);
EXPECT(string1.equals_ignoring_case(string1));
EXPECT(string1.equals_ignoring_case(string2));
EXPECT(string1.equals_ignoring_case(string3));
EXPECT(string1.equals_ignoring_case(string4));
EXPECT(!string1.equals_ignoring_case(string5));
EXPECT(!string1.equals_ignoring_case(string6));
EXPECT(string2.equals_ignoring_case(string1));
EXPECT(string2.equals_ignoring_case(string2));
EXPECT(string2.equals_ignoring_case(string3));
EXPECT(string2.equals_ignoring_case(string4));
EXPECT(!string2.equals_ignoring_case(string5));
EXPECT(!string2.equals_ignoring_case(string6));
EXPECT(string3.equals_ignoring_case(string1));
EXPECT(string3.equals_ignoring_case(string2));
EXPECT(string3.equals_ignoring_case(string3));
EXPECT(string3.equals_ignoring_case(string4));
EXPECT(!string3.equals_ignoring_case(string5));
EXPECT(!string3.equals_ignoring_case(string6));
EXPECT(string4.equals_ignoring_case(string1));
EXPECT(string4.equals_ignoring_case(string2));
EXPECT(string4.equals_ignoring_case(string3));
EXPECT(string4.equals_ignoring_case(string4));
EXPECT(!string4.equals_ignoring_case(string5));
EXPECT(!string4.equals_ignoring_case(string6));
}
}

2
Userland/Libraries/LibJS/Runtime/Intl/AbstractOperations.cpp
View file

@ -29,7 +29,7 @@ ThrowCompletionOr<Optional<::Locale::LocaleID>> is_structurally_valid_language_t
quick_sort(variants);
for (size_t i = 0; i < variants.size() - 1; ++i) {
if (TRY_OR_THROW_OOM(vm, variants[i].equals_ignoring_case(variants[i + 1])))
if (variants[i].equals_ignoring_case(variants[i + 1]))
return true;
}

54
Userland/Libraries/LibUnicode/String.cpp
View file

@ -6,6 +6,8 @@
#include <AK/String.h>
#include <AK/StringBuilder.h>
#include <AK/Utf32View.h>
#include <AK/Utf8View.h>
#include <LibUnicode/UnicodeUtils.h>
// This file contains definitions of AK::String methods which require UCD data.
@ -40,12 +42,60 @@ ErrorOr<String> String::to_casefold() const
return builder.to_string();
}
class CasefoldStringComparator {
public:
explicit CasefoldStringComparator(Utf8View string)
: m_string(string)
, m_it(m_string.begin())
{
}
bool has_more_data() const
{
return !m_casefolded_code_points.is_empty() || (m_it != m_string.end());
}
u32 next_code_point()
{
VERIFY(has_more_data());
if (m_casefolded_code_points.is_empty()) {
m_current_code_point = *m_it;
++m_it;
m_casefolded_code_points = Unicode::Detail::casefold_code_point(m_current_code_point);
VERIFY(!m_casefolded_code_points.is_empty()); // Must at least contain the provided code point.
}
auto code_point = m_casefolded_code_points[0];
m_casefolded_code_points = m_casefolded_code_points.substring_view(1);
return code_point;
}
private:
Utf8View m_string;
Utf8CodePointIterator m_it;
u32 m_current_code_point { 0 };
Utf32View m_casefolded_code_points;
};
// https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G34145
ErrorOr<bool> String::equals_ignoring_case(String const& other) const
bool String::equals_ignoring_case(String const& other) const
{
// A string X is a caseless match for a string Y if and only if:
// toCasefold(X) = toCasefold(Y)
return TRY(to_casefold()) == TRY(other.to_casefold());
CasefoldStringComparator lhs { code_points() };
CasefoldStringComparator rhs { other.code_points() };
while (lhs.has_more_data() && rhs.has_more_data()) {
if (lhs.next_code_point() != rhs.next_code_point())
return false;
}
return !lhs.has_more_data() && !rhs.has_more_data();
}
}

37
Userland/Libraries/LibUnicode/UnicodeUtils.cpp
View file

@ -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 };
}
}

2
Userland/Libraries/LibUnicode/UnicodeUtils.h
View file

@ -9,6 +9,7 @@
#include <AK/Error.h>
#include <AK/Forward.h>
#include <AK/Optional.h>
#include <AK/Utf32View.h>
#include <AK/Utf8View.h>
#include <LibUnicode/Forward.h>
@ -18,5 +19,6 @@ ErrorOr<void> build_lowercase_string(Utf8View code_points, StringBuilder& builde
ErrorOr<void> build_uppercase_string(Utf8View code_points, StringBuilder& builder, Optional<StringView> const& locale);
ErrorOr<void> build_titlecase_string(Utf8View code_points, StringBuilder& builder, Optional<StringView> const& locale);
ErrorOr<void> build_casefold_string(Utf8View code_points, StringBuilder& builder);
Utf32View casefold_code_point(u32 const& code_point);
}