Character properties

Read a property

UnicodeProperties gives the properties that text processing needs. Every method takes a code point as an int and never allocates: the value is read from a table.

Assert.Equal(UnicodeCategory.UppercaseLetter, UnicodeProperties.GetGeneralCategory('A'));
Assert.Equal(230, UnicodeProperties.GetCanonicalCombiningClass(0x0301));
Assert.Equal(UnicodeBidirectionalCategory.RightToLeft, UnicodeProperties.GetBidiClass(0x05D0));
Assert.True(UnicodeProperties.TryGetBidiMirroringGlyph('(', out var mirrored));
Assert.Equal(')', mirrored);
Assert.Equal(UnicodeLineBreakClass.Glue, UnicodeProperties.GetLineBreakClass(0x00A0));
Assert.Equal(UnicodeGraphemeClusterBreak.ZWJ, UnicodeProperties.GetGraphemeClusterBreak(0x200D));
Assert.Equal(UnicodeWordBreak.ExtendNumLet, UnicodeProperties.GetWordBreak('_'));
Assert.Equal(UnicodeEastAsianWidth.Wide, UnicodeProperties.GetEastAsianWidth(0x4E00));
Assert.Equal(UnicodeVerticalOrientation.TransformedRotated, UnicodeProperties.GetVerticalOrientation(0x300C));
Assert.Equal(UnicodeJoiningType.DualJoining, UnicodeProperties.GetJoiningType(0x0628));
Assert.Equal(UnicodeIndicSyllabicCategory.Virama, UnicodeProperties.GetIndicSyllabicCategory(0x094D));
Assert.True(UnicodeProperties.IsDefaultIgnorable(0x00AD));
Assert.True(UnicodeProperties.IsIdStart('a')); // UAX #31
Assert.True(UnicodeProperties.IsIdContinue('0'));
Assert.Equal('a', UnicodeProperties.ToSimpleLowercase('A'));
Assert.Equal(0x01C5, UnicodeProperties.ToSimpleTitlecase(0x01C6)); // 'dž' to 'Dž'
Assert.Equal('k', UnicodeProperties.ToSimpleCaseFold(0x212A)); // the Kelvin sign
Assert.True(UnicodeProperties.HasBinaryProperty(0x00E9, UnicodeBinaryProperty.Alphabetic));
Assert.Equal([new UnicodeRange('0', '9'), new UnicodeRange('A', 'F'), new UnicodeRange('a', 'f')], UnicodeProperties.GetBinaryPropertyRanges(UnicodeBinaryProperty.ASCIIHexDigit));

• HasBinaryProperty and GetBinaryPropertyRanges cover the binary properties of the Unicode Character Database (Alphabetic, White_Space, Changes_When_Casefolded, the emoji properties...), except the contributory Other_* properties.
• An unassigned code point has the default value the standard gives to its range, for instance RightToLeft in the Hebrew block. An integer that is not a code point has the default value of the property.
• The numeric values of the enumerations (UnicodeScript, UnicodeLineBreakClass, ...) never change: a later version of the standard only adds values. You can store them.

Map the case of a code point

The simple mappings (ToSimpleUppercase...) map a code point to one code point. The full mappings can give several: the German sharp s is SS in uppercase.

Span<int> mapping = stackalloc int[UnicodeProperties.MaxCaseMappingLength];

var length = UnicodeProperties.GetUppercaseMapping('ß', mapping);
Assert.Equal<int>(['S', 'S'], mapping[..length]);

length = UnicodeProperties.GetTitlecaseMapping(0xFB01, mapping); // the "fi" ligature
Assert.Equal<int>(['F', 'i'], mapping[..length]);

length = UnicodeProperties.GetLowercaseMapping(0x0130, mapping); // 'İ'
Assert.Equal<int>(['i', 0x0307], mapping[..length]);

The full mappings of a code point are the mappings of SpecialCasing.txt that apply everywhere, else the simple mappings. The mappings that depend on the language (Turkish, Lithuanian) or on the context (the final sigma of Greek) need the text around the code point: convert a whole text with UnicodeCaseMapping, described in Case conversion. ToSimpleCaseFold is the simple case folding of CaseFolding.txt, to compare texts without case.

Blocks and emoji

UnicodeBlocks has a property per block of the standard, and UnicodeEmoji the emoji properties of UTS #51:

Assert.True(UnicodeBlocks.BasicLatin.Contains('A'));
Assert.Equal(new UnicodeRange(0x0000, 0x007F), UnicodeBlocks.BasicLatin.Range);

Assert.True(UnicodeEmoji.IsEmoji(0x1F600));
Assert.True(UnicodeEmoji.HasEmojiPresentation(0x1F600));
Assert.False(UnicodeEmoji.HasEmojiPresentation(0x2764)); // the heart is shown as text unless followed by U+FE0F

// The emoji that are sequences of code points, such as flags
var flags = UnicodeEmoji.GetSequences(UnicodeEmojiSequenceProperty.RgiEmojiFlagSequence);
Assert.Contains("\U0001F1EB\U0001F1F7", flags);

• A block is a range of code points with a name. It says where a character was allocated, not what it is: to know the writing system of a character, use its script (see Scripts).
• UnicodeEmoji.GetSequences lists the emoji that are sequences of code points (flags, keycaps, people with a skin tone, sequences joined with U+200D), from the properties of strings of UTS #51.
• An emoji is often more than one code point: to count or cut emoji, use grapheme clusters (see Text segmentation).

Get the full record of a character

Unicode.GetCharacterInfo gives everything the Unicode Character Database says about a character, including its name. It is meant for inspection tools, such as a character map; to read one property of many code points, prefer UnicodeProperties.

var info = Unicode.GetCharacterInfo(new Rune('A'));

Assert.NotNull(info);
Assert.Equal("LATIN CAPITAL LETTER A", info.Value.Name);
Assert.Equal(UnicodeCategory.UppercaseLetter, info.Value.Category);
Assert.Equal(UnicodeBidirectionalCategory.LeftToRight, info.Value.BidiCategory);
Assert.Equal("Basic Latin", info.Value.Block.Name);

GetCharacterInfo returns null for a code point the Unicode data does not list, and TryGetCharacterInfo returns false. Unicode.AllCharacters lists the records of the Unicode data.