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LibUnicode: Implement grammar validators for Unicode TR-35
ECMA-402 requires validating user input against the EBNF grammar for Unicode locales described in TR-35: https://www.unicode.org/reports/tr35 This commit adds validators for that grammar, as well as other helper to e.g. canonicalize a locale string.
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152
Userland/Libraries/LibUnicode/Locale.cpp
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152
Userland/Libraries/LibUnicode/Locale.cpp
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/*
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* Copyright (c) 2021, Tim Flynn <trflynn89@pm.me>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/AllOf.h>
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#include <AK/CharacterTypes.h>
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#include <AK/GenericLexer.h>
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#include <AK/QuickSort.h>
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#include <AK/StringBuilder.h>
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#include <LibUnicode/Locale.h>
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namespace Unicode {
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bool is_unicode_language_subtag(StringView subtag)
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{
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// unicode_language_subtag = alpha{2,3} | alpha{5,8}
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if ((subtag.length() < 2) || (subtag.length() == 4) || (subtag.length() > 8))
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return false;
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return all_of(subtag, is_ascii_alpha);
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}
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bool is_unicode_script_subtag(StringView subtag)
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{
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// unicode_script_subtag = alpha{4}
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if (subtag.length() != 4)
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return false;
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return all_of(subtag, is_ascii_alpha);
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}
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bool is_unicode_region_subtag(StringView subtag)
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{
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// unicode_region_subtag = (alpha{2} | digit{3})
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if (subtag.length() == 2)
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return all_of(subtag, is_ascii_alpha);
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if (subtag.length() == 3)
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return all_of(subtag, is_ascii_digit);
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return false;
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}
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bool is_unicode_variant_subtag(StringView subtag)
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{
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// unicode_variant_subtag = (alphanum{5,8} | digit alphanum{3})
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if ((subtag.length() >= 5) && (subtag.length() <= 8))
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return all_of(subtag, is_ascii_alphanumeric);
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if (subtag.length() == 4)
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return is_ascii_digit(subtag[0]) && all_of(subtag.substring_view(1), is_ascii_alphanumeric);
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return false;
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}
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Optional<LanguageID> parse_unicode_language_id(StringView language)
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{
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// https://unicode.org/reports/tr35/#Unicode_language_identifier
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//
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// unicode_language_id = "root"
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// OR
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// unicode_language_id = ((unicode_language_subtag (sep unicode_script_subtag)?) | unicode_script_subtag)
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// (sep unicode_region_subtag)?
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// (sep unicode_variant_subtag)*
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LanguageID language_id {};
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if (language == "root"sv) {
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language_id.is_root = true;
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return language_id;
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}
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auto segments = language.split_view_if(is_any_of("-_"sv), true); // keep_empty=true to ensure valid data follows a separator.
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size_t index = 0;
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if (segments.size() == index)
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return {};
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if (is_unicode_language_subtag(segments[index])) {
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language_id.language = segments[index];
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if (segments.size() == ++index)
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return language_id;
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}
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if (is_unicode_script_subtag(segments[index])) {
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language_id.script = segments[index];
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if (segments.size() == ++index)
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return language_id;
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} else if (!language_id.language.has_value()) {
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return {};
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}
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if (is_unicode_region_subtag(segments[index])) {
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language_id.region = segments[index];
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if (segments.size() == ++index)
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return language_id;
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}
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while (index < segments.size()) {
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if (!is_unicode_variant_subtag(segments[index]))
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return {};
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language_id.variants.append(segments[index++]);
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}
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return language_id;
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}
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Optional<LocaleID> parse_unicode_locale_id(StringView locale)
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{
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LocaleID locale_id {};
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// https://unicode.org/reports/tr35/#Unicode_locale_identifier
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//
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// unicode_locale_id = unicode_language_id
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// extensions*
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// pu_extensions?
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auto language_id = parse_unicode_language_id(locale);
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if (!language_id.has_value())
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return {};
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// FIXME: Handle extensions and pu_extensions.
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return LocaleID { language_id.release_value() };
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}
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Optional<String> canonicalize_unicode_locale_id(LocaleID& locale_id)
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{
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// https://unicode.org/reports/tr35/#Canonical_Unicode_Locale_Identifiers
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StringBuilder builder;
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if (!locale_id.language_id.language.has_value())
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return {};
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builder.append(locale_id.language_id.language->to_lowercase_string());
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if (locale_id.language_id.script.has_value()) {
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builder.append('-');
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builder.append(locale_id.language_id.script->to_titlecase_string());
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}
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if (locale_id.language_id.region.has_value()) {
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builder.append('-');
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builder.append(locale_id.language_id.region->to_uppercase_string());
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}
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quick_sort(locale_id.language_id.variants);
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for (auto const& variant : locale_id.language_id.variants) {
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builder.append('-');
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builder.append(variant.to_lowercase_string());
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}
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// FIXME: Handle extensions and pu_extensions.
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return builder.build();
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}
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}
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