IANA To/From Windows Ids Conversion APIs #51093
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| Original file line number | Diff line number | Diff line change | ||||
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| // Licensed to the .NET Foundation under one or more agreements. | ||||||
| // The .NET Foundation licenses this file to you under the MIT license. | ||||||
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| using System.Globalization; | ||||||
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| namespace System | ||||||
| { | ||||||
| public sealed partial class TimeZoneInfo | ||||||
| { | ||||||
| private const string InvariantUtcStandardDisplayName = "Coordinated Universal Time"; | ||||||
| private const string FallbackCultureName = "en-US"; | ||||||
| private const string GmtId = "GMT"; | ||||||
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| // Some time zones may give better display names using their location names rather than their generic name. | ||||||
| // We can update this list as need arises. | ||||||
| private static readonly string[] s_ZonesThatUseLocationName = new[] { | ||||||
| "Europe/Minsk", // Prefer "Belarus Time" over "Moscow Standard Time (Minsk)" | ||||||
| "Europe/Moscow", // Prefer "Moscow Time" over "Moscow Standard Time" | ||||||
| "Europe/Simferopol", // Prefer "Simferopol Time" over "Moscow Standard Time (Simferopol)" | ||||||
| "Pacific/Apia", // Prefer "Samoa Time" over "Apia Time" | ||||||
| "Pacific/Pitcairn" // Prefer "Pitcairn Islands Time" over "Pitcairn Time" | ||||||
| }; | ||||||
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| // Main function that is called during construction to populate the three display names | ||||||
| private static void TryPopulateTimeZoneDisplayNamesFromGlobalizationData(string timeZoneId, TimeSpan baseUtcOffset, ref string? standardDisplayName, ref string? daylightDisplayName, ref string? displayName) | ||||||
| { | ||||||
| // Determine the culture to use | ||||||
| CultureInfo uiCulture = CultureInfo.CurrentUICulture; | ||||||
| if (uiCulture.Name.Length == 0) | ||||||
| uiCulture = CultureInfo.GetCultureInfo(FallbackCultureName); // ICU doesn't work nicely with InvariantCulture | ||||||
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| // Attempt to populate the fields backing the StandardName, DaylightName, and DisplayName from globalization data. | ||||||
| GetDisplayName(timeZoneId, Interop.Globalization.TimeZoneDisplayNameType.Standard, uiCulture.Name, ref standardDisplayName); | ||||||
| GetDisplayName(timeZoneId, Interop.Globalization.TimeZoneDisplayNameType.DaylightSavings, uiCulture.Name, ref daylightDisplayName); | ||||||
| GetFullValueForDisplayNameField(timeZoneId, baseUtcOffset, uiCulture, ref displayName); | ||||||
| } | ||||||
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| // Helper function to get the standard display name for the UTC static time zone instance | ||||||
| private static string GetUtcStandardDisplayName() | ||||||
| { | ||||||
| // Don't bother looking up the name for invariant or English cultures | ||||||
| CultureInfo uiCulture = CultureInfo.CurrentUICulture; | ||||||
| if (GlobalizationMode.Invariant || uiCulture.Name.Length == 0 || uiCulture.TwoLetterISOLanguageName == "en") | ||||||
| return InvariantUtcStandardDisplayName; | ||||||
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| // Try to get a localized version of "Coordinated Universal Time" from the globalization data | ||||||
| string? standardDisplayName = null; | ||||||
| GetDisplayName(UtcId, Interop.Globalization.TimeZoneDisplayNameType.Standard, uiCulture.Name, ref standardDisplayName); | ||||||
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| // Final safety check. Don't allow null or abbreviations | ||||||
| if (standardDisplayName == null || standardDisplayName == "GMT" || standardDisplayName == "UTC") | ||||||
| standardDisplayName = InvariantUtcStandardDisplayName; | ||||||
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| return standardDisplayName; | ||||||
| } | ||||||
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| // Helper function to get the full display name for the UTC static time zone instance | ||||||
| private static string GetUtcFullDisplayName(string timeZoneId, string standardDisplayName) | ||||||
| { | ||||||
| return $"(UTC) {standardDisplayName}"; | ||||||
| } | ||||||
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| // Helper function that retrieves various forms of time zone display names from ICU | ||||||
| private static unsafe void GetDisplayName(string timeZoneId, Interop.Globalization.TimeZoneDisplayNameType nameType, string uiCulture, ref string? displayName) | ||||||
|
There was a problem hiding this comment. I wonder why we use
Suggested change
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| { | ||||||
| if (GlobalizationMode.Invariant) | ||||||
| { | ||||||
| return; | ||||||
| } | ||||||
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| string? timeZoneDisplayName; | ||||||
| bool result = Interop.CallStringMethod( | ||||||
| (buffer, locale, id, type) => | ||||||
|
There was a problem hiding this comment. Can we set static?
Suggested change
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| { | ||||||
| fixed (char* bufferPtr = buffer) | ||||||
| { | ||||||
| return Interop.Globalization.GetTimeZoneDisplayName(locale, id, type, bufferPtr, buffer.Length); | ||||||
| } | ||||||
| }, | ||||||
| uiCulture, | ||||||
| timeZoneId, | ||||||
| nameType, | ||||||
| out timeZoneDisplayName); | ||||||
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| if (!result && uiCulture != FallbackCultureName) | ||||||
| { | ||||||
| // Try to fallback using FallbackCultureName just in case we can make it work. | ||||||
| result = Interop.CallStringMethod( | ||||||
| (buffer, locale, id, type) => | ||||||
|
There was a problem hiding this comment. Can we set static?
Suggested change
|
||||||
| { | ||||||
| fixed (char* bufferPtr = buffer) | ||||||
| { | ||||||
| return Interop.Globalization.GetTimeZoneDisplayName(locale, id, type, bufferPtr, buffer.Length); | ||||||
| } | ||||||
| }, | ||||||
| FallbackCultureName, | ||||||
| timeZoneId, | ||||||
| nameType, | ||||||
| out timeZoneDisplayName); | ||||||
| } | ||||||
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| // If there is an unknown error, don't set the displayName field. | ||||||
| // It will be set to the abbreviation that was read out of the tzfile. | ||||||
| if (result && !string.IsNullOrEmpty(timeZoneDisplayName)) | ||||||
| { | ||||||
| displayName = timeZoneDisplayName; | ||||||
| } | ||||||
| } | ||||||
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| // Helper function that builds the value backing the DisplayName field from globalization data. | ||||||
| private static void GetFullValueForDisplayNameField(string timeZoneId, TimeSpan baseUtcOffset, CultureInfo uiCulture, ref string? displayName) | ||||||
| { | ||||||
| // There are a few diffent ways we might show the display name depending on the data. | ||||||
| // The algorithm used below should avoid duplicating the same words while still achieving the | ||||||
| // goal of providing a unique, discoverable, and intuitive name. | ||||||
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| // Try to get the generic name for this time zone. | ||||||
| string? genericName = null; | ||||||
| GetDisplayName(timeZoneId, Interop.Globalization.TimeZoneDisplayNameType.Generic, uiCulture.Name, ref genericName); | ||||||
| if (genericName == null) | ||||||
| { | ||||||
| // We'll use the fallback display name value already set. | ||||||
| return; | ||||||
| } | ||||||
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| // Get the base offset to prefix in front of the time zone. | ||||||
| // Only UTC and its aliases have "(UTC)", handled earlier. All other zones include an offset, even if it's zero. | ||||||
| string baseOffsetText = $"(UTC{(baseUtcOffset >= TimeSpan.Zero ? '+' : '-')}{baseUtcOffset:hh\\:mm})"; | ||||||
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| // Get the generic location name. | ||||||
| string? genericLocationName = null; | ||||||
| GetDisplayName(timeZoneId, Interop.Globalization.TimeZoneDisplayNameType.GenericLocation, uiCulture.Name, ref genericLocationName); | ||||||
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||||||
| // Some edge cases only apply when the offset is +00:00. | ||||||
| if (baseUtcOffset == TimeSpan.Zero) | ||||||
| { | ||||||
| // GMT and its aliases will just use the equivalent of "Greenwich Mean Time". | ||||||
| string? gmtLocationName = null; | ||||||
| GetDisplayName(GmtId, Interop.Globalization.TimeZoneDisplayNameType.GenericLocation, uiCulture.Name, ref gmtLocationName); | ||||||
| if (genericLocationName == gmtLocationName) | ||||||
| { | ||||||
| displayName = $"{baseOffsetText} {genericName}"; | ||||||
| return; | ||||||
| } | ||||||
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| // Other zones with a zero offset and the equivalent of "Greenwich Mean Time" should only use the location name. | ||||||
| // For example, prefer "Iceland Time" over "Greenwich Mean Time (Reykjavik)". | ||||||
| string? gmtGenericName = null; | ||||||
| GetDisplayName(GmtId, Interop.Globalization.TimeZoneDisplayNameType.Generic, uiCulture.Name, ref gmtGenericName); | ||||||
| if (genericName == gmtGenericName) | ||||||
| { | ||||||
| displayName = $"{baseOffsetText} {genericLocationName}"; | ||||||
| return; | ||||||
| } | ||||||
| } | ||||||
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| if (genericLocationName == genericName) | ||||||
| { | ||||||
| // When the location name is the same as the generic name, | ||||||
| // then it is generally good enough to show by itself. | ||||||
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| // *** Example (en-US) *** | ||||||
| // id = "America/Havana" | ||||||
| // baseOffsetText = "(UTC-05:00)" | ||||||
| // standardName = "Cuba Standard Time" | ||||||
| // genericName = "Cuba Time" | ||||||
| // genericLocationName = "Cuba Time" | ||||||
| // exemplarCityName = "Havana" | ||||||
| // displayName = "(UTC-05:00) Cuba Time" | ||||||
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| displayName = $"{baseOffsetText} {genericLocationName}"; | ||||||
| return; | ||||||
| } | ||||||
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| // Prefer location names in some special cases. | ||||||
| if (StringArrayContains(timeZoneId, s_ZonesThatUseLocationName, StringComparison.OrdinalIgnoreCase)) | ||||||
| { | ||||||
| displayName = $"{baseOffsetText} {genericLocationName}"; | ||||||
| return; | ||||||
| } | ||||||
|
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| // See if we should include the exemplar city name. | ||||||
| string exemplarCityName = GetExemplarCityName(timeZoneId, uiCulture.Name); | ||||||
| if (uiCulture.CompareInfo.IndexOf(genericName, exemplarCityName, CompareOptions.IgnoreCase | CompareOptions.IgnoreNonSpace) >= 0 && genericLocationName != null) | ||||||
|
There was a problem hiding this comment. Maybe swap conditions:
Suggested change
|
||||||
| { | ||||||
| // When an exemplar city is already part of the generic name, | ||||||
| // there's no need to repeat it again so just use the generic name. | ||||||
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| // *** Example (fr-FR) *** | ||||||
| // id = "Australia/Lord_Howe" | ||||||
| // baseOffsetText = "(UTC+10:30)" | ||||||
| // standardName = "heure normale de Lord Howe" | ||||||
| // genericName = "heure de Lord Howe" | ||||||
| // genericLocationName = "heure : Lord Howe" | ||||||
| // exemplarCityName = "Lord Howe" | ||||||
| // displayName = "(UTC+10:30) heure de Lord Howe" | ||||||
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| displayName = $"{baseOffsetText} {genericName}"; | ||||||
| } | ||||||
| else | ||||||
| { | ||||||
| // Finally, use the generic name and the exemplar city together. | ||||||
| // This provides an intuitive name and still disambiguates. | ||||||
|
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| // *** Example (en-US) *** | ||||||
| // id = "Europe/Rome" | ||||||
| // baseOffsetText = "(UTC+01:00)" | ||||||
| // standardName = "Central European Standard Time" | ||||||
| // genericName = "Central European Time" | ||||||
| // genericLocationName = "Italy Time" | ||||||
| // exemplarCityName = "Rome" | ||||||
| // displayName = "(UTC+01:00) Central European Time (Rome)" | ||||||
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| displayName = $"{baseOffsetText} {genericName} ({exemplarCityName})"; | ||||||
| } | ||||||
| } | ||||||
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| // Helper function that gets an exmplar city name either from ICU or from the IANA time zone ID itself | ||||||
| private static string GetExemplarCityName(string timeZoneId, string uiCultureName) | ||||||
| { | ||||||
| // First try to get the name through the localization data. | ||||||
| string? exemplarCityName = null; | ||||||
| GetDisplayName(timeZoneId, Interop.Globalization.TimeZoneDisplayNameType.ExemplarCity, uiCultureName, ref exemplarCityName); | ||||||
| if (!string.IsNullOrEmpty(exemplarCityName)) | ||||||
| return exemplarCityName; | ||||||
|
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||||||
| // Support for getting exemplar city names was added in ICU 51. | ||||||
| // We may have an older version. For example, in Helix we test on RHEL 7.5 which uses ICU 50.1.2. | ||||||
| // We'll fallback to using an English name generated from the time zone ID. | ||||||
| int i = timeZoneId.LastIndexOf('/'); | ||||||
| return timeZoneId.Substring(i + 1).Replace('_', ' '); | ||||||
| } | ||||||
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| // Helper function that returns an alternative ID using ICU data. Used primarily for converting from Windows IDs. | ||||||
| private static unsafe string? GetAlternativeId(string id, out bool idIsIana) | ||||||
| { | ||||||
| idIsIana = false; | ||||||
| return TryConvertWindowsIdToIanaId(id, null, out string? ianaId) ? ianaId : null; | ||||||
| } | ||||||
| } | ||||||
| } | ||||||
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I see in some place such culture sensitive string comparisons. Make sense to use ordinal?
(Below I see
if (windowsId.Equals("utc", StringComparison.OrdinalIgnoreCase)))