gecko-dev/intl/locale/MozLocale.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode:nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_intl_MozLocale_h__
#define mozilla_intl_MozLocale_h__

#include "nsString.h"
#include "nsTArray.h"

namespace mozilla {
namespace intl {

/**
 * Locale class is a core representation of a single locale.
 *
 * A locale is a data object representing a combination of language, script,
 * region, variant and a set of regional extension preferences that may further specify
 * particular user choices like calendar, numbering system, etc.
 *
 * A locale can be expressed as a language tag string, like a simple "fr" for French,
 * or a more specific "sr-Cyrl-RS-u-hc-h12" for Serbian in Russia with a Cyrylic script,
 * and hour cycle selected to be `h12`.
 *
 * The format of the language tag follows BCP47 standard and implements a subset of it.
 * In the future we expect to extend this class to cover more subtags and extensions.
 *
 * BCP47: https://tools.ietf.org/html/bcp47
 *
 * The aim of this class it aid in validation, parsing and canonicalization of the
 * string.
 *
 * It allows the user to input any well-formed BCP47 language tag and operate
 * on its subtags in a canonicalized form.
 *
 * It should be used for all operations on language tags, and together with
 * LocaleService::NegotiateLanguages for language negotiation.
 *
 * Example:
 *
 *     Locale loc = Locale("de-at");
 *
 *     ASSERT_TRUE(loc.GetLanguage().Equals("de"));
 *     ASSERT_TRUE(loc.GetScript().IsEmpty());
 *     ASSERT_TRUE(loc.GetRegion().Equals("AT")); // canonicalized to upper case
 *
 *
 * Note: The file name is `MozLocale` to avoid compilation problems on case-insensitive
 * Windows. The class name is `Locale`.
 */
class Locale {
  public:
    /**
     * The constructor expects the input to be a well-formed BCP47-style locale string.
     *
     * Two operations are performed on the well-formed language tags:
     *
     *  * Case normalization to conform with BCP47 (e.g. "eN-uS" -> "en-US")
     *  * Underscore delimiters replaced with dashed (e.g. "en_US" -> "en-US")
     *
     * If the input language tag string is not well-formed, the Locale will be
     * created with its flag `mWellFormed` set to false which will make the Locale never match.
     */
    explicit Locale(const nsACString& aLocale);
    explicit Locale(const char* aLocale)
      : Locale(nsDependentCString(aLocale))
      { };

    const nsCString& GetLanguage() const;
    const nsCString& GetScript() const;
    const nsCString& GetRegion() const;
    const nsTArray<nsCString>& GetVariants() const;

    /**
     * Returns a `true` if the locale is well-formed, such that the
     * Locale object can validly be matched against others.
     */
    bool IsWellFormed() const {
      return mIsWellFormed;
    }

    /**
     * Returns a canonicalized language tag string of the locale.
     */
    const nsCString AsString() const;

    /**
     * Compares two locales optionally treating one or both of
     * the locales as a range.
     *
     * In case one of the locales is treated as a range, its
     * empty fields are considered to match all possible
     * values of the same field on the other locale.
     *
     * Example:
     *
     * Locale("en").Matches(Locale("en-US"), false, false) // false
     * Locale("en").Matches(Locale("en-US"), true, false)  // true
     *
     * The latter returns true because the region field on the "en"
     * locale is being treated as a range and matches any region field
     * value including "US" of the other locale.
     */
    bool Matches(const Locale& aOther, bool aThisRange, bool aOtherRange) const;

    /**
     * This operation uses CLDR data to build a more specific version
     * of a generic locale.
     *
     * Example:
     *
     * Locale("en").AddLikelySubtags().AsString(); // "en-Latn-US"
     */
    bool AddLikelySubtags();

    /**
     * Clears the variants field of the Locale object.
     */
    void ClearVariants();

    /**
     * Clears the region field of the Locale object.
     */
    void ClearRegion();

    /**
     * Marks the locale as invalid which in turns makes
     * it to be skipped by most LocaleService operations.
     */
    void Invalidate() {
      mIsWellFormed = false;
    }

    /**
     * Compares two locales expecting all fields to match each other.
     */
    bool operator== (const Locale& aOther) {
      // Note: non-well-formed Locale objects are never
      // treated as equal to anything
      // (even other non-well-formed ones).
      return IsWellFormed() &&
             aOther.IsWellFormed() &&
             mLanguage.Equals(aOther.mLanguage) &&
             mScript.Equals(aOther.mScript) &&
             mRegion.Equals(aOther.mRegion) &&
             mVariants == aOther.mVariants &&
             mPrivateUse == aOther.mPrivateUse;
    }

  private:
    nsAutoCStringN<3> mLanguage;
    nsAutoCStringN<4> mScript;
    nsAutoCStringN<2> mRegion;
    nsTArray<nsCString> mVariants;
    nsTArray<nsCString> mPrivateUse;
    bool mIsWellFormed = true;
};

} // intl
} // namespace mozilla

DECLARE_USE_COPY_CONSTRUCTORS(mozilla::intl::Locale)

#endif /* mozilla_intl_MozLocale_h__ */