LibUnicode: Move Unicode-aware case transformations to a helper file

These will be needed by AK::String as well, so move them to a helper
file where they can be re-used.

Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateUnicodeData.cpp

@@ -781,6 +781,8 @@ struct CodePointDecomposition {
 
 Optional<Locale> locale_from_string(StringView locale);
 
+Span<SpecialCasing const* const> special_case_mapping(u32 code_point);
+
 }
 )~~~");
 

Userland/Libraries/LibUnicode/CMakeLists.txt

@@ -5,6 +5,7 @@ set(SOURCES
     CurrencyCode.cpp
     Emoji.cpp
     Normalize.cpp
+    UnicodeUtils.cpp
     ${UNICODE_DATA_SOURCES}
 )
 set(GENERATED_SOURCES ${CURRENT_LIB_GENERATED})

Userland/Libraries/LibUnicode/CharacterTypes.cpp

@@ -11,6 +11,7 @@
 #include <AK/Utf16View.h>
 #include <AK/Utf8View.h>
 #include <LibUnicode/CharacterTypes.h>
+#include <LibUnicode/UnicodeUtils.h>
 
 #if ENABLE_UNICODE_DATA
 #    include <LibUnicode/UnicodeData.h>
@@ -25,192 +26,8 @@ Optional<DeprecatedString> __attribute__((weak)) code_point_display_name(u32) {
 Optional<StringView> __attribute__((weak)) code_point_block_display_name(u32) { return {}; }
 Optional<StringView> __attribute__((weak)) code_point_abbreviation(u32) { return {}; }
 u32 __attribute__((weak)) canonical_combining_class(u32) { return {}; }
-Span<SpecialCasing const* const> __attribute__((weak)) special_case_mapping(u32) { return {}; }
 Span<BlockName const> __attribute__((weak)) block_display_names() { return {}; }
 
-#if ENABLE_UNICODE_DATA
-
-static bool is_after_uppercase_i(Utf8View const& string, size_t index)
-{
-    // There is an uppercase I before C, and there is no intervening combining character class 230 (Above) or 0.
-    auto preceding_view = string.substring_view(0, index);
-    bool found_uppercase_i = false;
-
-    // FIXME: Would be better if Utf8View supported reverse iteration.
-    for (auto code_point : preceding_view) {
-        if (code_point == 'I') {
-            found_uppercase_i = true;
-            continue;
-        }
-
-        u32 combining_class = canonical_combining_class(code_point);
-
-        if (combining_class == 0)
-            found_uppercase_i = false;
-        else if (combining_class == 230)
-            found_uppercase_i = false;
-    }
-
-    return found_uppercase_i;
-}
-
-static bool is_after_soft_dotted_code_point(Utf8View const& string, size_t index)
-{
-    // There is a Soft_Dotted character before C, with no intervening character of combining class 0 or 230 (Above).
-    auto preceding_view = string.substring_view(0, index);
-    bool found_soft_dotted_code_point = false;
-
-    // FIXME: Would be better if Utf8View supported reverse iteration.
-    for (auto code_point : preceding_view) {
-        if (code_point_has_property(code_point, Property::Soft_Dotted)) {
-            found_soft_dotted_code_point = true;
-            continue;
-        }
-
-        u32 combining_class = canonical_combining_class(code_point);
-
-        if (combining_class == 0)
-            found_soft_dotted_code_point = false;
-        else if (combining_class == 230)
-            found_soft_dotted_code_point = false;
-    }
-
-    return found_soft_dotted_code_point;
-}
-
-static bool is_final_code_point(Utf8View const& string, size_t index, size_t byte_length)
-{
-    // C is preceded by a sequence consisting of a cased letter and then zero or more case-ignorable
-    // characters, and C is not followed by a sequence consisting of zero or more case-ignorable
-    // characters and then a cased letter.
-    auto preceding_view = string.substring_view(0, index);
-    auto following_view = ((index + byte_length) < string.byte_length())
-        ? string.substring_view(index + byte_length)
-        : Utf8View {};
-
-    size_t cased_letter_count = 0;
-
-    for (auto code_point : preceding_view) {
-        bool is_cased = code_point_has_property(code_point, Property::Cased);
-        bool is_case_ignorable = code_point_has_property(code_point, Property::Case_Ignorable);
-
-        if (is_cased && !is_case_ignorable)
-            ++cased_letter_count;
-        else if (!is_case_ignorable)
-            cased_letter_count = 0;
-    }
-
-    if (cased_letter_count == 0)
-        return false;
-
-    for (auto code_point : following_view) {
-        bool is_cased = code_point_has_property(code_point, Property::Cased);
-        bool is_case_ignorable = code_point_has_property(code_point, Property::Case_Ignorable);
-
-        if (is_case_ignorable)
-            continue;
-        if (is_cased)
-            return false;
-
-        break;
-    }
-
-    return true;
-}
-
-static bool is_followed_by_combining_class_above(Utf8View const& string, size_t index, size_t byte_length)
-{
-    // C is followed by a character of combining class 230 (Above) with no intervening character of combining class 0 or 230 (Above).
-    auto following_view = ((index + byte_length) < string.byte_length())
-        ? string.substring_view(index + byte_length)
-        : Utf8View {};
-
-    for (auto code_point : following_view) {
-        u32 combining_class = canonical_combining_class(code_point);
-
-        if (combining_class == 0)
-            return false;
-        if (combining_class == 230)
-            return true;
-    }
-
-    return false;
-}
-
-static bool is_followed_by_combining_dot_above(Utf8View const& string, size_t index, size_t byte_length)
-{
-    // C is followed by combining dot above (U+0307). Any sequence of characters with a combining class that is neither 0 nor 230 may
-    // intervene between the current character and the combining dot above.
-    auto following_view = ((index + byte_length) < string.byte_length())
-        ? string.substring_view(index + byte_length)
-        : Utf8View {};
-
-    for (auto code_point : following_view) {
-        if (code_point == 0x307)
-            return true;
-
-        u32 combining_class = canonical_combining_class(code_point);
-
-        if (combining_class == 0)
-            return false;
-        if (combining_class == 230)
-            return false;
-    }
-
-    return false;
-}
-
-static SpecialCasing const* find_matching_special_case(u32 code_point, Utf8View const& string, Optional<StringView> locale, size_t index, size_t byte_length)
-{
-    auto requested_locale = Locale::None;
-
-    if (locale.has_value()) {
-        if (auto maybe_locale = locale_from_string(*locale); maybe_locale.has_value())
-            requested_locale = *maybe_locale;
-    }
-
-    auto special_casings = special_case_mapping(code_point);
-
-    for (auto const* special_casing : special_casings) {
-        if (special_casing->locale != Locale::None && special_casing->locale != requested_locale)
-            continue;
-
-        switch (special_casing->condition) {
-        case Condition::None:
-            return special_casing;
-
-        case Condition::AfterI:
-            if (is_after_uppercase_i(string, index))
-                return special_casing;
-            break;
-
-        case Condition::AfterSoftDotted:
-            if (is_after_soft_dotted_code_point(string, index))
-                return special_casing;
-            break;
-
-        case Condition::FinalSigma:
-            if (is_final_code_point(string, index, byte_length))
-                return special_casing;
-            break;
-
-        case Condition::MoreAbove:
-            if (is_followed_by_combining_class_above(string, index, byte_length))
-                return special_casing;
-            break;
-
-        case Condition::NotBeforeDot:
-            if (!is_followed_by_combining_dot_above(string, index, byte_length))
-                return special_casing;
-            break;
-        }
-    }
-
-    return nullptr;
-}
-
-#endif
-
 u32 __attribute__((weak)) to_unicode_lowercase(u32 code_point)
 {
     return to_ascii_lowercase(code_point);
@@ -221,62 +38,18 @@ u32 __attribute__((weak)) to_unicode_uppercase(u32 code_point)
     return to_ascii_uppercase(code_point);
 }
 
-ErrorOr<DeprecatedString> to_unicode_lowercase_full(StringView string, [[maybe_unused]] Optional<StringView> locale)
+ErrorOr<DeprecatedString> to_unicode_lowercase_full(StringView string, Optional<StringView> const& locale)
 {
-#if ENABLE_UNICODE_DATA
-    Utf8View view { string };
     StringBuilder builder;
-
-    size_t index = 0;
-    size_t byte_length = 0;
-
-    for (auto it = view.begin(); it != view.end(); ++it, index += byte_length) {
-        u32 code_point = *it;
-        byte_length = it.underlying_code_point_length_in_bytes();
-
-        auto const* special_casing = find_matching_special_case(code_point, view, locale, index, byte_length);
-        if (!special_casing) {
-            TRY(builder.try_append_code_point(to_unicode_lowercase(code_point)));
-            continue;
-        }
-
-        for (size_t i = 0; i < special_casing->lowercase_mapping_size; ++i)
-            TRY(builder.try_append_code_point(special_casing->lowercase_mapping[i]));
-    }
-
-    return builder.build();
-#else
-    return string.to_lowercase_string();
-#endif
+    TRY(Detail::build_lowercase_string(Utf8View { string }, builder, locale));
+    return builder.to_deprecated_string();
 }
 
-ErrorOr<DeprecatedString> to_unicode_uppercase_full(StringView string, [[maybe_unused]] Optional<StringView> locale)
+ErrorOr<DeprecatedString> to_unicode_uppercase_full(StringView string, Optional<StringView> const& locale)
 {
-#if ENABLE_UNICODE_DATA
-    Utf8View view { string };
     StringBuilder builder;
-
-    size_t index = 0;
-    size_t byte_length = 0;
-
-    for (auto it = view.begin(); it != view.end(); ++it, index += byte_length) {
-        u32 code_point = *it;
-        byte_length = it.underlying_code_point_length_in_bytes();
-
-        auto const* special_casing = find_matching_special_case(code_point, view, locale, index, byte_length);
-        if (!special_casing) {
-            TRY(builder.try_append_code_point(to_unicode_uppercase(code_point)));
-            continue;
-        }
-
-        for (size_t i = 0; i < special_casing->uppercase_mapping_size; ++i)
-            TRY(builder.try_append_code_point(special_casing->uppercase_mapping[i]));
-    }
-
-    return builder.build();
-#else
-    return string.to_uppercase_string();
-#endif
+    TRY(Detail::build_uppercase_string(Utf8View { string }, builder, locale));
+    return builder.to_deprecated_string();
 }
 
 Optional<GeneralCategory> __attribute__((weak)) general_category_from_string(StringView) { return {}; }

Userland/Libraries/LibUnicode/CharacterTypes.h

@@ -32,15 +32,14 @@ Optional<StringView> code_point_abbreviation(u32 code_point);
 Span<BlockName const> block_display_names();
 
 u32 canonical_combining_class(u32 code_point);
-Span<SpecialCasing const* const> special_case_mapping(u32 code_point);
 
 // Note: The single code point case conversions only perform simple case folding.
 // Use the full-string transformations for full case folding.
 u32 to_unicode_lowercase(u32 code_point);
 u32 to_unicode_uppercase(u32 code_point);
 
-ErrorOr<DeprecatedString> to_unicode_lowercase_full(StringView, Optional<StringView> locale = {});
-ErrorOr<DeprecatedString> to_unicode_uppercase_full(StringView, Optional<StringView> locale = {});
+ErrorOr<DeprecatedString> to_unicode_lowercase_full(StringView, Optional<StringView> const& locale = {});
+ErrorOr<DeprecatedString> to_unicode_uppercase_full(StringView, Optional<StringView> const& locale = {});
 
 Optional<GeneralCategory> general_category_from_string(StringView);
 bool code_point_has_general_category(u32 code_point, GeneralCategory general_category);

Userland/Libraries/LibUnicode/UnicodeUtils.cpp

@@ -0,0 +1,252 @@
+/*
+ * Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Platform.h>
+#include <AK/String.h>
+#include <AK/StringBuilder.h>
+#include <AK/Types.h>
+#include <LibUnicode/CharacterTypes.h>
+#include <LibUnicode/UnicodeUtils.h>
+
+#if ENABLE_UNICODE_DATA
+#    include <LibUnicode/UnicodeData.h>
+#endif
+
+// For details on the algorithms used here, see Section 3.13 Default Case Algorithms
+// https://www.unicode.org/versions/Unicode13.0.0/ch03.pdf
+
+namespace Unicode::Detail {
+
+#if ENABLE_UNICODE_DATA
+
+static bool is_after_uppercase_i(Utf8View const& string, size_t index)
+{
+    // There is an uppercase I before C, and there is no intervening combining character class 230 (Above) or 0.
+    auto preceding_view = string.substring_view(0, index);
+    bool found_uppercase_i = false;
+
+    // FIXME: Would be better if Utf8View supported reverse iteration.
+    for (auto code_point : preceding_view) {
+        if (code_point == 'I') {
+            found_uppercase_i = true;
+            continue;
+        }
+
+        auto combining_class = canonical_combining_class(code_point);
+        if (combining_class == 0 || combining_class == 230)
+            found_uppercase_i = false;
+    }
+
+    return found_uppercase_i;
+}
+
+static bool is_after_soft_dotted_code_point(Utf8View const& string, size_t index)
+{
+    // There is a Soft_Dotted character before C, with no intervening character of combining class 0 or 230 (Above).
+    auto preceding_view = string.substring_view(0, index);
+    bool found_soft_dotted_code_point = false;
+
+    // FIXME: Would be better if Utf8View supported reverse iteration.
+    for (auto code_point : preceding_view) {
+        if (code_point_has_property(code_point, Property::Soft_Dotted)) {
+            found_soft_dotted_code_point = true;
+            continue;
+        }
+
+        auto combining_class = canonical_combining_class(code_point);
+        if (combining_class == 0 || combining_class == 230)
+            found_soft_dotted_code_point = false;
+    }
+
+    return found_soft_dotted_code_point;
+}
+
+static bool is_final_code_point(Utf8View const& string, size_t index, size_t byte_length)
+{
+    // C is preceded by a sequence consisting of a cased letter and then zero or more case-ignorable
+    // characters, and C is not followed by a sequence consisting of zero or more case-ignorable
+    // characters and then a cased letter.
+    auto preceding_view = string.substring_view(0, index);
+    auto following_view = ((index + byte_length) < string.byte_length())
+        ? string.substring_view(index + byte_length)
+        : Utf8View {};
+
+    size_t cased_letter_count = 0;
+
+    for (auto code_point : preceding_view) {
+        bool is_cased = code_point_has_property(code_point, Property::Cased);
+        bool is_case_ignorable = code_point_has_property(code_point, Property::Case_Ignorable);
+
+        if (is_cased && !is_case_ignorable)
+            ++cased_letter_count;
+        else if (!is_case_ignorable)
+            cased_letter_count = 0;
+    }
+
+    if (cased_letter_count == 0)
+        return false;
+
+    for (auto code_point : following_view) {
+        bool is_cased = code_point_has_property(code_point, Property::Cased);
+        bool is_case_ignorable = code_point_has_property(code_point, Property::Case_Ignorable);
+
+        if (is_case_ignorable)
+            continue;
+        if (is_cased)
+            return false;
+
+        break;
+    }
+
+    return true;
+}
+
+static bool is_followed_by_combining_class_above(Utf8View const& string, size_t index, size_t byte_length)
+{
+    // C is followed by a character of combining class 230 (Above) with no intervening character of combining class 0 or 230 (Above).
+    auto following_view = ((index + byte_length) < string.byte_length())
+        ? string.substring_view(index + byte_length)
+        : Utf8View {};
+
+    for (auto code_point : following_view) {
+        u32 combining_class = canonical_combining_class(code_point);
+
+        if (combining_class == 0)
+            return false;
+        if (combining_class == 230)
+            return true;
+    }
+
+    return false;
+}
+
+static bool is_followed_by_combining_dot_above(Utf8View const& string, size_t index, size_t byte_length)
+{
+    // C is followed by combining dot above (U+0307). Any sequence of characters with a combining class that is neither 0 nor 230 may
+    // intervene between the current character and the combining dot above.
+    auto following_view = ((index + byte_length) < string.byte_length())
+        ? string.substring_view(index + byte_length)
+        : Utf8View {};
+
+    for (auto code_point : following_view) {
+        if (code_point == 0x307)
+            return true;
+
+        u32 combining_class = canonical_combining_class(code_point);
+
+        if (combining_class == 0)
+            return false;
+        if (combining_class == 230)
+            return false;
+    }
+
+    return false;
+}
+
+static SpecialCasing const* find_matching_special_case(u32 code_point, Utf8View const& string, Optional<StringView> locale, size_t index, size_t byte_length)
+{
+    auto requested_locale = Locale::None;
+
+    if (locale.has_value()) {
+        if (auto maybe_locale = locale_from_string(*locale); maybe_locale.has_value())
+            requested_locale = *maybe_locale;
+    }
+
+    auto special_casings = special_case_mapping(code_point);
+
+    for (auto const* special_casing : special_casings) {
+        if (special_casing->locale != Locale::None && special_casing->locale != requested_locale)
+            continue;
+
+        switch (special_casing->condition) {
+        case Condition::None:
+            return special_casing;
+
+        case Condition::AfterI:
+            if (is_after_uppercase_i(string, index))
+                return special_casing;
+            break;
+
+        case Condition::AfterSoftDotted:
+            if (is_after_soft_dotted_code_point(string, index))
+                return special_casing;
+            break;
+
+        case Condition::FinalSigma:
+            if (is_final_code_point(string, index, byte_length))
+                return special_casing;
+            break;
+
+        case Condition::MoreAbove:
+            if (is_followed_by_combining_class_above(string, index, byte_length))
+                return special_casing;
+            break;
+
+        case Condition::NotBeforeDot:
+            if (!is_followed_by_combining_dot_above(string, index, byte_length))
+                return special_casing;
+            break;
+        }
+    }
+
+    return nullptr;
+}
+
+#endif
+
+ErrorOr<void> build_lowercase_string([[maybe_unused]] Utf8View code_points, [[maybe_unused]] StringBuilder& builder, [[maybe_unused]] Optional<StringView> const& locale)
+{
+#if ENABLE_UNICODE_DATA
+    size_t index = 0;
+    size_t byte_length = 0;
+
+    for (auto it = code_points.begin(); it != code_points.end(); ++it, index += byte_length) {
+        u32 code_point = *it;
+        byte_length = it.underlying_code_point_length_in_bytes();
+
+        auto const* special_casing = find_matching_special_case(code_point, code_points, locale, index, byte_length);
+        if (!special_casing) {
+            TRY(builder.try_append_code_point(to_unicode_lowercase(code_point)));
+            continue;
+        }
+
+        for (size_t i = 0; i < special_casing->lowercase_mapping_size; ++i)
+            TRY(builder.try_append_code_point(special_casing->lowercase_mapping[i]));
+    }
+
+    return {};
+#else
+    return Error::from_string_literal("Unicode data has been disabled");
+#endif
+}
+
+ErrorOr<void> build_uppercase_string([[maybe_unused]] Utf8View code_points, [[maybe_unused]] StringBuilder& builder, [[maybe_unused]] Optional<StringView> const& locale)
+{
+#if ENABLE_UNICODE_DATA
+    size_t index = 0;
+    size_t byte_length = 0;
+
+    for (auto it = code_points.begin(); it != code_points.end(); ++it, index += byte_length) {
+        u32 code_point = *it;
+        byte_length = it.underlying_code_point_length_in_bytes();
+
+        auto const* special_casing = find_matching_special_case(code_point, code_points, locale, index, byte_length);
+        if (!special_casing) {
+            TRY(builder.try_append_code_point(to_unicode_uppercase(code_point)));
+            continue;
+        }
+
+        for (size_t i = 0; i < special_casing->uppercase_mapping_size; ++i)
+            TRY(builder.try_append_code_point(special_casing->uppercase_mapping[i]));
+    }
+
+    return {};
+#else
+    return Error::from_string_literal("Unicode data has been disabled");
+#endif
+}
+
+}

Userland/Libraries/LibUnicode/UnicodeUtils.h

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Error.h>
+#include <AK/Forward.h>
+#include <AK/Optional.h>
+#include <AK/Utf8View.h>
+#include <LibUnicode/Forward.h>
+
+namespace Unicode::Detail {
+
+ErrorOr<void> build_lowercase_string(Utf8View code_points, StringBuilder& builder, Optional<StringView> const& locale);
+ErrorOr<void> build_uppercase_string(Utf8View code_points, StringBuilder& builder, Optional<StringView> const& locale);
+
+}