third_party/WebKit/Source/platform/Language.cpp

/*
 * Copyright (C) 2010, 2013 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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#include "platform/Language.h"

#include "public/platform/Platform.h"
#include "wtf/text/WTFString.h"

namespace blink {

static String canonicalizeLanguageIdentifier(const String& languageCode) {
  String copiedCode = languageCode;
  // Platform::defaultLocale() might provide a language code with '_'.
  copiedCode.replace('_', '-');
  return copiedCode;
}

static const AtomicString& platformLanguage() {
  DEFINE_STATIC_LOCAL(AtomicString, computedDefaultLanguage, ());
  if (computedDefaultLanguage.isEmpty()) {
    computedDefaultLanguage = AtomicString(
        canonicalizeLanguageIdentifier(Platform::current()->defaultLocale()));
    ASSERT(!computedDefaultLanguage.isEmpty());
  }
  return computedDefaultLanguage;
}

static Vector<AtomicString>& preferredLanguagesOverride() {
  DEFINE_STATIC_LOCAL(Vector<AtomicString>, override, ());
  return override;
}

void overrideUserPreferredLanguages(const Vector<AtomicString>& override) {
  Vector<AtomicString>& canonicalized = preferredLanguagesOverride();
  canonicalized.resize(0);
  canonicalized.reserveCapacity(override.size());
  for (const auto& lang : override)
    canonicalized.append(canonicalizeLanguageIdentifier(lang));
}

AtomicString defaultLanguage() {
  Vector<AtomicString>& override = preferredLanguagesOverride();
  if (!override.isEmpty())
    return override[0];
  return platformLanguage();
}

Vector<AtomicString> userPreferredLanguages() {
  Vector<AtomicString>& override = preferredLanguagesOverride();
  if (!override.isEmpty())
    return override;

  Vector<AtomicString> languages;
  languages.reserveInitialCapacity(1);
  languages.append(platformLanguage());
  return languages;
}

size_t indexOfBestMatchingLanguageInList(
    const AtomicString& language,
    const Vector<AtomicString>& languageList) {
  AtomicString languageWithoutLocaleMatch;
  AtomicString languageMatchButNotLocale;
  size_t languageWithoutLocaleMatchIndex = 0;
  size_t languageMatchButNotLocaleMatchIndex = 0;
  bool canMatchLanguageOnly = (language.length() == 2 ||
                               (language.length() >= 3 && language[2] == '-'));

  for (size_t i = 0; i < languageList.size(); ++i) {
    String canonicalizedLanguageFromList =
        canonicalizeLanguageIdentifier(languageList[i]);

    if (language == canonicalizedLanguageFromList)
      return i;

    if (canMatchLanguageOnly && canonicalizedLanguageFromList.length() >= 2) {
      if (language[0] == canonicalizedLanguageFromList[0] &&
          language[1] == canonicalizedLanguageFromList[1]) {
        if (!languageWithoutLocaleMatch.length() &&
            canonicalizedLanguageFromList.length() == 2) {
          languageWithoutLocaleMatch = languageList[i];
          languageWithoutLocaleMatchIndex = i;
        }
        if (!languageMatchButNotLocale.length() &&
            canonicalizedLanguageFromList.length() >= 3) {
          languageMatchButNotLocale = languageList[i];
          languageMatchButNotLocaleMatchIndex = i;
        }
      }
    }
  }

  // If we have both a language-only match and a languge-but-not-locale match,
  // return the languge-only match as is considered a "better" match. For
  // example, if the list provided has both "en-GB" and "en" and the user
  // prefers "en-US" we will return "en".
  if (languageWithoutLocaleMatch.length())
    return languageWithoutLocaleMatchIndex;

  if (languageMatchButNotLocale.length())
    return languageMatchButNotLocaleMatchIndex;

  return languageList.size();
}

}  // namespace blink