chromium/third_party/icu/source/i18n/unicode/tznames.h

// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
*******************************************************************************
* Copyright (C) 2011-2016, International Business Machines Corporation and
* others. All Rights Reserved.
*******************************************************************************
*/
#ifndef __TZNAMES_H
#define __TZNAMES_H

/**
 * \file
 * \brief C++ API: TimeZoneNames
 */
#include "unicode/utypes.h"

#if U_SHOW_CPLUSPLUS_API

#if !UCONFIG_NO_FORMATTING

#include "unicode/uloc.h"
#include "unicode/unistr.h"

U_CDECL_BEGIN

/**
 * Constants for time zone display name types.
 * @stable ICU 50
 */
UTimeZoneNameType;

U_CDECL_END

U_NAMESPACE_BEGIN

class UVector;
struct MatchInfo;

/**
 * <code>TimeZoneNames</code> is an abstract class representing the time zone display name data model defined
 * by <a href="http://www.unicode.org/reports/tr35/">UTS#35 Unicode Locale Data Markup Language (LDML)</a>.
 * The model defines meta zone, which is used for storing a set of display names. A meta zone can be shared
 * by multiple time zones. Also a time zone may have multiple meta zone historic mappings.
 * <p>
 * For example, people in the United States refer the zone used by the east part of North America as "Eastern Time".
 * The tz database contains multiple time zones "America/New_York", "America/Detroit", "America/Montreal" and some
 * others that belong to "Eastern Time". However, assigning different display names to these time zones does not make
 * much sense for most of people.
 * <p>
 * In <a href="http://cldr.unicode.org/">CLDR</a> (which uses LDML for representing locale data), the display name
 * "Eastern Time" is stored as long generic display name of a meta zone identified by the ID "America_Eastern".
 * Then, there is another table maintaining the historic mapping to meta zones for each time zone. The time zones in
 * the above example ("America/New_York", "America/Detroit"...) are mapped to the meta zone "America_Eastern".
 * <p>
 * Sometimes, a time zone is mapped to a different time zone in the past. For example, "America/Indiana/Knox"
 * had been moving "Eastern Time" and "Central Time" back and forth. Therefore, it is necessary that time zone
 * to meta zones mapping data are stored by date range.
 *
 * <p><b>Note:</b>
 * The methods in this class assume that time zone IDs are already canonicalized. For example, you may not get proper
 * result returned by a method with time zone ID "America/Indiana/Indianapolis", because it's not a canonical time zone
 * ID (the canonical time zone ID for the time zone is "America/Indianapolis". See
 * {@link TimeZone#getCanonicalID(const UnicodeString& id, UnicodeString& canonicalID, UErrorCode& status)} about ICU
 * canonical time zone IDs.
 *
 * <p>
 * In CLDR, most of time zone display names except location names are provided through meta zones. But a time zone may
 * have a specific name that is not shared with other time zones.
 *
 * For example, time zone "Europe/London" has English long name for standard time "Greenwich Mean Time", which is also
 * shared with other time zones. However, the long name for daylight saving time is "British Summer Time", which is only
 * used for "Europe/London".
 *
 * <p>
 * {@link #getTimeZoneDisplayName} is designed for accessing a name only used by a single time zone.
 * But is not necessarily mean that a subclass implementation use the same model with CLDR. A subclass implementation
 * may provide time zone names only through {@link #getTimeZoneDisplayName}, or only through {@link #getMetaZoneDisplayName},
 * or both.
 *
 * <p>
 * The default <code>TimeZoneNames</code> implementation returned by {@link #createInstance}
 * uses the locale data imported from CLDR. In CLDR, set of meta zone IDs and mappings between zone IDs and meta zone
 * IDs are shared by all locales. Therefore, the behavior of {@link #getAvailableMetaZoneIDs},
 * {@link #getMetaZoneID}, and {@link #getReferenceZoneID} won't be changed no matter
 * what locale is used for getting an instance of <code>TimeZoneNames</code>.
 *
 * @stable ICU 50
 */
class U_I18N_API TimeZoneNames : public UObject { … };

U_NAMESPACE_END

#endif

#endif /* U_SHOW_CPLUSPLUS_API */

#endif