C# dotnet 获取某个字符所在 Unicode 字符平面映射

在 dotnet 里面可以通过安装 System.Text.Encodings.Web 库拿到 UnicodeRanges 这个包含了 Unicode 标准的平面映射。但是我还没有找到如何判断一个字符是落在哪个平面的逻辑，本文就告诉大家一个可以使用的方法，这个方法同时稍微兼顾了性能

在 System.Text.Encodings.Web 的 UnicodeRanges 其实是根据标准生成的代码，源代码请看 https://github.com/dotnet/runtime/blob/5372ee9dbe48058ca8d3591763e989d3b2e65581/src/libraries/System.Text.Encodings.Web/src/System/Text/Unicode/UnicodeRanges.generated.cs

本文根据 UnicodeRanges 的定义写出了一个列表如下

        /// <summary>
        /// 这个列表已经是按照 FirstCodePoint 排过顺序的
        /// </summary>
        private static List<UnicodeRangeInfo> UnicodeRangeInfoList { get; } = new List<UnicodeRangeInfo>()
        {
            //new UnicodeRangeInfo("None",UnicodeRanges.None),
            //new UnicodeRangeInfo("All",UnicodeRanges.All),
            new UnicodeRangeInfo("BasicLatin", UnicodeRanges.BasicLatin),
            new UnicodeRangeInfo("Latin1Supplement", UnicodeRanges.Latin1Supplement),
            new UnicodeRangeInfo("LatinExtendedA", UnicodeRanges.LatinExtendedA),
            new UnicodeRangeInfo("LatinExtendedB", UnicodeRanges.LatinExtendedB),
            new UnicodeRangeInfo("IpaExtensions", UnicodeRanges.IpaExtensions),
            new UnicodeRangeInfo("SpacingModifierLetters", UnicodeRanges.SpacingModifierLetters),
            new UnicodeRangeInfo("CombiningDiacriticalMarks", UnicodeRanges.CombiningDiacriticalMarks),
            new UnicodeRangeInfo("GreekandCoptic", UnicodeRanges.GreekandCoptic),
            new UnicodeRangeInfo("Cyrillic", UnicodeRanges.Cyrillic),
            new UnicodeRangeInfo("CyrillicSupplement", UnicodeRanges.CyrillicSupplement),
            new UnicodeRangeInfo("Armenian", UnicodeRanges.Armenian),
            new UnicodeRangeInfo("Hebrew", UnicodeRanges.Hebrew),
            new UnicodeRangeInfo("Arabic", UnicodeRanges.Arabic),
            new UnicodeRangeInfo("Syriac", UnicodeRanges.Syriac),
            new UnicodeRangeInfo("ArabicSupplement", UnicodeRanges.ArabicSupplement),
            new UnicodeRangeInfo("Thaana", UnicodeRanges.Thaana),
            new UnicodeRangeInfo("NKo", UnicodeRanges.NKo),
            new UnicodeRangeInfo("Samaritan", UnicodeRanges.Samaritan),
            new UnicodeRangeInfo("Mandaic", UnicodeRanges.Mandaic),
            new UnicodeRangeInfo("SyriacSupplement", UnicodeRanges.SyriacSupplement),
            new UnicodeRangeInfo("ArabicExtendedA", UnicodeRanges.ArabicExtendedA),
            new UnicodeRangeInfo("Devanagari", UnicodeRanges.Devanagari),
            new UnicodeRangeInfo("Bengali", UnicodeRanges.Bengali),
            new UnicodeRangeInfo("Gurmukhi", UnicodeRanges.Gurmukhi),
            new UnicodeRangeInfo("Gujarati", UnicodeRanges.Gujarati),
            new UnicodeRangeInfo("Oriya", UnicodeRanges.Oriya),
            new UnicodeRangeInfo("Tamil", UnicodeRanges.Tamil),
            new UnicodeRangeInfo("Telugu", UnicodeRanges.Telugu),
            new UnicodeRangeInfo("Kannada", UnicodeRanges.Kannada),
            new UnicodeRangeInfo("Malayalam", UnicodeRanges.Malayalam),
            new UnicodeRangeInfo("Sinhala", UnicodeRanges.Sinhala),
            new UnicodeRangeInfo("Thai", UnicodeRanges.Thai),
            new UnicodeRangeInfo("Lao", UnicodeRanges.Lao),
            new UnicodeRangeInfo("Tibetan", UnicodeRanges.Tibetan),
            new UnicodeRangeInfo("Myanmar", UnicodeRanges.Myanmar),
            new UnicodeRangeInfo("Georgian", UnicodeRanges.Georgian),
            new UnicodeRangeInfo("HangulJamo", UnicodeRanges.HangulJamo),
            new UnicodeRangeInfo("Ethiopic", UnicodeRanges.Ethiopic),
            new UnicodeRangeInfo("EthiopicSupplement", UnicodeRanges.EthiopicSupplement),
            new UnicodeRangeInfo("Cherokee", UnicodeRanges.Cherokee),
            new UnicodeRangeInfo("UnifiedCanadianAboriginalSyllabics",
                UnicodeRanges.UnifiedCanadianAboriginalSyllabics),
            new UnicodeRangeInfo("Ogham", UnicodeRanges.Ogham),
            new UnicodeRangeInfo("Runic", UnicodeRanges.Runic),
            new UnicodeRangeInfo("Tagalog", UnicodeRanges.Tagalog),
            new UnicodeRangeInfo("Hanunoo", UnicodeRanges.Hanunoo),
            new UnicodeRangeInfo("Buhid", UnicodeRanges.Buhid),
            new UnicodeRangeInfo("Tagbanwa", UnicodeRanges.Tagbanwa),
            new UnicodeRangeInfo("Khmer", UnicodeRanges.Khmer),
            new UnicodeRangeInfo("Mongolian", UnicodeRanges.Mongolian),
            new UnicodeRangeInfo("UnifiedCanadianAboriginalSyllabicsExtended",
                UnicodeRanges.UnifiedCanadianAboriginalSyllabicsExtended),
            new UnicodeRangeInfo("Limbu", UnicodeRanges.Limbu),
            new UnicodeRangeInfo("TaiLe", UnicodeRanges.TaiLe),
            new UnicodeRangeInfo("NewTaiLue", UnicodeRanges.NewTaiLue),
            new UnicodeRangeInfo("KhmerSymbols", UnicodeRanges.KhmerSymbols),
            new UnicodeRangeInfo("Buginese", UnicodeRanges.Buginese),
            new UnicodeRangeInfo("TaiTham", UnicodeRanges.TaiTham),
            new UnicodeRangeInfo("CombiningDiacriticalMarksExtended", UnicodeRanges.CombiningDiacriticalMarksExtended),
            new UnicodeRangeInfo("Balinese", UnicodeRanges.Balinese),
            new UnicodeRangeInfo("Sundanese", UnicodeRanges.Sundanese),
            new UnicodeRangeInfo("Batak", UnicodeRanges.Batak),
            new UnicodeRangeInfo("Lepcha", UnicodeRanges.Lepcha),
            new UnicodeRangeInfo("OlChiki", UnicodeRanges.OlChiki),
            new UnicodeRangeInfo("CyrillicExtendedC", UnicodeRanges.CyrillicExtendedC),
            new UnicodeRangeInfo("GeorgianExtended", UnicodeRanges.GeorgianExtended),
            new UnicodeRangeInfo("SundaneseSupplement", UnicodeRanges.SundaneseSupplement),
            new UnicodeRangeInfo("VedicExtensions", UnicodeRanges.VedicExtensions),
            new UnicodeRangeInfo("PhoneticExtensions", UnicodeRanges.PhoneticExtensions),
            new UnicodeRangeInfo("PhoneticExtensionsSupplement", UnicodeRanges.PhoneticExtensionsSupplement),
            new UnicodeRangeInfo("CombiningDiacriticalMarksSupplement",
                UnicodeRanges.CombiningDiacriticalMarksSupplement),
            new UnicodeRangeInfo("LatinExtendedAdditional", UnicodeRanges.LatinExtendedAdditional),
            new UnicodeRangeInfo("GreekExtended", UnicodeRanges.GreekExtended),
            new UnicodeRangeInfo("GeneralPunctuation", UnicodeRanges.GeneralPunctuation),
            new UnicodeRangeInfo("SuperscriptsandSubscripts", UnicodeRanges.SuperscriptsandSubscripts),
            new UnicodeRangeInfo("CurrencySymbols", UnicodeRanges.CurrencySymbols),
            new UnicodeRangeInfo("CombiningDiacriticalMarksforSymbols",
                UnicodeRanges.CombiningDiacriticalMarksforSymbols),
            new UnicodeRangeInfo("LetterlikeSymbols", UnicodeRanges.LetterlikeSymbols),
            new UnicodeRangeInfo("NumberForms", UnicodeRanges.NumberForms),
            new UnicodeRangeInfo("Arrows", UnicodeRanges.Arrows),
            new UnicodeRangeInfo("MathematicalOperators", UnicodeRanges.MathematicalOperators),
            new UnicodeRangeInfo("MiscellaneousTechnical", UnicodeRanges.MiscellaneousTechnical),
            new UnicodeRangeInfo("ControlPictures", UnicodeRanges.ControlPictures),
            new UnicodeRangeInfo("OpticalCharacterRecognition", UnicodeRanges.OpticalCharacterRecognition),
            new UnicodeRangeInfo("EnclosedAlphanumerics", UnicodeRanges.EnclosedAlphanumerics),
            new UnicodeRangeInfo("BoxDrawing", UnicodeRanges.BoxDrawing),
            new UnicodeRangeInfo("BlockElements", UnicodeRanges.BlockElements),
            new UnicodeRangeInfo("GeometricShapes", UnicodeRanges.GeometricShapes),
            new UnicodeRangeInfo("MiscellaneousSymbols", UnicodeRanges.MiscellaneousSymbols),
            new UnicodeRangeInfo("Dingbats", UnicodeRanges.Dingbats),
            new UnicodeRangeInfo("MiscellaneousMathematicalSymbolsA", UnicodeRanges.MiscellaneousMathematicalSymbolsA),
            new UnicodeRangeInfo("SupplementalArrowsA", UnicodeRanges.SupplementalArrowsA),
            new UnicodeRangeInfo("BraillePatterns", UnicodeRanges.BraillePatterns),
            new UnicodeRangeInfo("SupplementalArrowsB", UnicodeRanges.SupplementalArrowsB),
            new UnicodeRangeInfo("MiscellaneousMathematicalSymbolsB", UnicodeRanges.MiscellaneousMathematicalSymbolsB),
            new UnicodeRangeInfo("SupplementalMathematicalOperators", UnicodeRanges.SupplementalMathematicalOperators),
            new UnicodeRangeInfo("MiscellaneousSymbolsandArrows", UnicodeRanges.MiscellaneousSymbolsandArrows),
            new UnicodeRangeInfo("Glagolitic", UnicodeRanges.Glagolitic),
            new UnicodeRangeInfo("LatinExtendedC", UnicodeRanges.LatinExtendedC),
            new UnicodeRangeInfo("Coptic", UnicodeRanges.Coptic),
            new UnicodeRangeInfo("GeorgianSupplement", UnicodeRanges.GeorgianSupplement),
            new UnicodeRangeInfo("Tifinagh", UnicodeRanges.Tifinagh),
            new UnicodeRangeInfo("EthiopicExtended", UnicodeRanges.EthiopicExtended),
            new UnicodeRangeInfo("CyrillicExtendedA", UnicodeRanges.CyrillicExtendedA),
            new UnicodeRangeInfo("SupplementalPunctuation", UnicodeRanges.SupplementalPunctuation),
            new UnicodeRangeInfo("CjkRadicalsSupplement", UnicodeRanges.CjkRadicalsSupplement),
            new UnicodeRangeInfo("KangxiRadicals", UnicodeRanges.KangxiRadicals),
            new UnicodeRangeInfo("IdeographicDescriptionCharacters", UnicodeRanges.IdeographicDescriptionCharacters),
            new UnicodeRangeInfo("CjkSymbolsandPunctuation", UnicodeRanges.CjkSymbolsandPunctuation),
            new UnicodeRangeInfo("Hiragana", UnicodeRanges.Hiragana),
            new UnicodeRangeInfo("Katakana", UnicodeRanges.Katakana),
            new UnicodeRangeInfo("Bopomofo", UnicodeRanges.Bopomofo),
            new UnicodeRangeInfo("HangulCompatibilityJamo", UnicodeRanges.HangulCompatibilityJamo),
            new UnicodeRangeInfo("Kanbun", UnicodeRanges.Kanbun),
            new UnicodeRangeInfo("BopomofoExtended", UnicodeRanges.BopomofoExtended),
            new UnicodeRangeInfo("CjkStrokes", UnicodeRanges.CjkStrokes),
            new UnicodeRangeInfo("KatakanaPhoneticExtensions", UnicodeRanges.KatakanaPhoneticExtensions),
            new UnicodeRangeInfo("EnclosedCjkLettersandMonths", UnicodeRanges.EnclosedCjkLettersandMonths),
            new UnicodeRangeInfo("CjkCompatibility", UnicodeRanges.CjkCompatibility),
            new UnicodeRangeInfo("CjkUnifiedIdeographsExtensionA", UnicodeRanges.CjkUnifiedIdeographsExtensionA),
            new UnicodeRangeInfo("YijingHexagramSymbols", UnicodeRanges.YijingHexagramSymbols),
            new UnicodeRangeInfo("CjkUnifiedIdeographs", UnicodeRanges.CjkUnifiedIdeographs),
            new UnicodeRangeInfo("YiSyllables", UnicodeRanges.YiSyllables),
            new UnicodeRangeInfo("YiRadicals", UnicodeRanges.YiRadicals),
            new UnicodeRangeInfo("Lisu", UnicodeRanges.Lisu),
            new UnicodeRangeInfo("Vai", UnicodeRanges.Vai),
            new UnicodeRangeInfo("CyrillicExtendedB", UnicodeRanges.CyrillicExtendedB),
            new UnicodeRangeInfo("Bamum", UnicodeRanges.Bamum),
            new UnicodeRangeInfo("ModifierToneLetters", UnicodeRanges.ModifierToneLetters),
            new UnicodeRangeInfo("LatinExtendedD", UnicodeRanges.LatinExtendedD),
            new UnicodeRangeInfo("SylotiNagri", UnicodeRanges.SylotiNagri),
            new UnicodeRangeInfo("CommonIndicNumberForms", UnicodeRanges.CommonIndicNumberForms),
            new UnicodeRangeInfo("Phagspa", UnicodeRanges.Phagspa),
            new UnicodeRangeInfo("Saurashtra", UnicodeRanges.Saurashtra),
            new UnicodeRangeInfo("DevanagariExtended", UnicodeRanges.DevanagariExtended),
            new UnicodeRangeInfo("KayahLi", UnicodeRanges.KayahLi),
            new UnicodeRangeInfo("Rejang", UnicodeRanges.Rejang),
            new UnicodeRangeInfo("HangulJamoExtendedA", UnicodeRanges.HangulJamoExtendedA),
            new UnicodeRangeInfo("Javanese", UnicodeRanges.Javanese),
            new UnicodeRangeInfo("MyanmarExtendedB", UnicodeRanges.MyanmarExtendedB),
            new UnicodeRangeInfo("Cham", UnicodeRanges.Cham),
            new UnicodeRangeInfo("MyanmarExtendedA", UnicodeRanges.MyanmarExtendedA),
            new UnicodeRangeInfo("TaiViet", UnicodeRanges.TaiViet),
            new UnicodeRangeInfo("MeeteiMayekExtensions", UnicodeRanges.MeeteiMayekExtensions),
            new UnicodeRangeInfo("EthiopicExtendedA", UnicodeRanges.EthiopicExtendedA),
            new UnicodeRangeInfo("LatinExtendedE", UnicodeRanges.LatinExtendedE),
            new UnicodeRangeInfo("CherokeeSupplement", UnicodeRanges.CherokeeSupplement),
            new UnicodeRangeInfo("MeeteiMayek", UnicodeRanges.MeeteiMayek),
            new UnicodeRangeInfo("HangulSyllables", UnicodeRanges.HangulSyllables),
            new UnicodeRangeInfo("HangulJamoExtendedB", UnicodeRanges.HangulJamoExtendedB),
            new UnicodeRangeInfo("CjkCompatibilityIdeographs", UnicodeRanges.CjkCompatibilityIdeographs),
            new UnicodeRangeInfo("AlphabeticPresentationForms", UnicodeRanges.AlphabeticPresentationForms),
            new UnicodeRangeInfo("ArabicPresentationFormsA", UnicodeRanges.ArabicPresentationFormsA),
            new UnicodeRangeInfo("VariationSelectors", UnicodeRanges.VariationSelectors),
            new UnicodeRangeInfo("VerticalForms", UnicodeRanges.VerticalForms),
            new UnicodeRangeInfo("CombiningHalfMarks", UnicodeRanges.CombiningHalfMarks),
            new UnicodeRangeInfo("CjkCompatibilityForms", UnicodeRanges.CjkCompatibilityForms),
            new UnicodeRangeInfo("SmallFormVariants", UnicodeRanges.SmallFormVariants),
            new UnicodeRangeInfo("ArabicPresentationFormsB", UnicodeRanges.ArabicPresentationFormsB),
            new UnicodeRangeInfo("HalfwidthandFullwidthForms", UnicodeRanges.HalfwidthandFullwidthForms),
            new UnicodeRangeInfo("Specials", UnicodeRanges.Specials),
        };

如果不信这个列表已经排好序，请使用下面方法测试一下

        /// <summary>
        /// 按照 FirstCodePoint 排序，看顺序是否是对的，这个方法仅是让你知道这个列表是排序的
        /// </summary>
        /// <returns></returns>
        internal static bool CheckSort()
        {
            var t = UnicodeRangeInfoList.ToList();
            t.Sort((a, b) => a.UnicodeRange.FirstCodePoint.CompareTo(b.UnicodeRange.FirstCodePoint));

            for (var i = 0; i < UnicodeRangeInfoList.Count; i++)
            {
                if (!ReferenceEquals(t[i], UnicodeRangeInfoList[i]))
                {
                    return false;
                }

            }

            return true;
        }

如果上面方法返回 true 那么证明排序之后的列表和当前的列表是完全相同

这里的 UnicodeRangeInfo 是自己定义的类，可以让平面的名字和值关联

        private class UnicodeRangeInfo
        {
            public UnicodeRangeInfo(string unicodeRangeName, UnicodeRange unicodeRange)
            {
                UnicodeRangeName = unicodeRangeName;
                UnicodeRange = unicodeRange;
            }

            public string UnicodeRangeName { get; }

            public UnicodeRange UnicodeRange { get; }
        }

在拿到一个字符的时候，根据 UnicodeRange 可以判断是否落在这个平面里面，从统计里面使用的字符大部分都是中文或英文字符，所以本文就根据这两个优化

        private static UnicodeRangeInfo GetUnicodeRangeInfo(char ch)
        {
            // 这是英文 数字
            if (UnicodeRangeInfoList[0].UnicodeRange.Contain(ch))
            {
                // UnicodeRangeInfoList[0].UnicodeRange == UnicodeRanges.BasicLatin
                return UnicodeRangeInfoList[0];
            }

            // 119
            var currentIndex = 119;//准备二分，这个值刚好是 中日韩统一表意文字 CJK Unified Ideographs 
            var left = 0;
            var right = UnicodeRangeInfoList.Count;
            while (left <= right)
            {
                var unicodeRangeInfo = UnicodeRangeInfoList[currentIndex];
                var unicodeRange = unicodeRangeInfo.UnicodeRange;
                if (unicodeRange.Contain(ch))
                {
                    return unicodeRangeInfo;
                }
                else if (unicodeRange.FirstCodePoint < ch)
                {
                    // 不落在 unicodeRange 里面，同时比 FirstCodePoint 大的，一定比 unicodeRange.FirstCodePoint + unicodeRange.Length 大
                    left = currentIndex + 1;
                }
                else if (unicodeRange.FirstCodePoint > ch)
                {
                    right = currentIndex - 1;
                }

                currentIndex = (right + left) / 2;
            }

            return null;
        }

调用这个类可以使用三个方法，一个是获取字符所在的 UnicodeRange 可以用来判断多个字符是否落在一个平面，另一个是获取平面名。最后一个是根据所在平面获取平面名

        /// <summary>
        /// 获取此字符所在范围
        /// </summary>
        /// <param name="ch"></param>
        /// <returns></returns>
        public static UnicodeRange GetUnicodeRange(char ch)
            => GetUnicodeRangeInfo(ch)?.UnicodeRange;

        /// <summary>
        /// 获取此字符所在范围名
        /// </summary>
        /// <param name="ch"></param>
        /// <returns></returns>
        public static string GetUnicodeRangeName(char ch)
            => GetUnicodeRangeInfo(ch)?.UnicodeRangeName;

        /// <summary>
        /// 获取字符范围名
        /// </summary>
        /// <param name="unicodeRange"></param>
        /// <returns></returns>
        public static string GetUnicodeRangeName(UnicodeRange unicodeRange) => UnicodeRangeInfoList
            .FirstOrDefault(temp => ReferenceEquals(temp.UnicodeRange, unicodeRange))?.UnicodeRangeName;