85 lines
3.6 KiB
Swift
85 lines
3.6 KiB
Swift
extension PureXML.Parsing.ByteDecoder {
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/// To-Unicode mappings for the single-byte legacy encodings. Each maps one
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/// byte to its Unicode scalar; bytes `0x00`-`0x7F` are ASCII in every case.
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/// The encodings here are the ones expressible exactly as ISO-8859-1 with a
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/// few substitutions or as a contiguous block, so they carry no risk of a
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/// transcription error.
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enum SingleByte {
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/// ISO-8859-15 (Latin-9): ISO-8859-1 with the euro sign and seven other
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/// substitutions.
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static func iso8859_15(_ byte: UInt8) -> Unicode.Scalar {
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switch byte {
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case 0xA4: "\u{20AC}" // €
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case 0xA6: "\u{0160}" // Š
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case 0xA8: "\u{0161}" // š
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case 0xB4: "\u{017D}" // Ž
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case 0xB8: "\u{017E}" // ž
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case 0xBC: "\u{0152}" // Œ
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case 0xBD: "\u{0153}" // œ
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case 0xBE: "\u{0178}" // Ÿ
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default: Unicode.Scalar(byte)
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}
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}
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/// ISO-8859-9 (Latin-5, Turkish): ISO-8859-1 with six Turkish letters
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/// replacing the Icelandic ones.
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static func iso8859_9(_ byte: UInt8) -> Unicode.Scalar {
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switch byte {
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case 0xD0: "\u{011E}" // Ğ
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case 0xDD: "\u{0130}" // İ
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case 0xDE: "\u{015E}" // Ş
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case 0xF0: "\u{011F}" // ğ
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case 0xFD: "\u{0131}" // ı
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case 0xFE: "\u{015F}" // ş
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default: Unicode.Scalar(byte)
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}
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}
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/// Windows-1254 (Turkish): Windows-1252 with the same six Turkish letters
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/// as ISO-8859-9 (the only differences fall in the Latin-1 upper half).
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static func windows1254(_ byte: UInt8) -> Unicode.Scalar {
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switch byte {
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case 0xD0: "\u{011E}" // Ğ
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case 0xDD: "\u{0130}" // İ
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case 0xDE: "\u{015E}" // Ş
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case 0xF0: "\u{011F}" // ğ
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case 0xFD: "\u{0131}" // ı
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case 0xFE: "\u{015F}" // ş
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default: PureXML.Parsing.ByteDecoder.windows1252Scalar(byte)
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}
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}
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/// ISO-8859-5 (Latin/Cyrillic): the Cyrillic alphabet laid out as a
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/// contiguous block from `0xB0`, with a handful of named exceptions.
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static func iso8859_5(_ byte: UInt8) -> Unicode.Scalar {
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switch byte {
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case 0xA1 ... 0xAC: scalar(0x0401 + UInt32(byte) - 0xA1) // Ё..Ќ
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case 0xAE ... 0xAF: scalar(0x040E + UInt32(byte) - 0xAE) // Ў Џ
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case 0xB0 ... 0xEF: scalar(0x0410 + UInt32(byte) - 0xB0) // А..я
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case 0xF0: "\u{2116}" // №
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case 0xF1 ... 0xFC: scalar(0x0451 + UInt32(byte) - 0xF1) // ё..ќ
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case 0xFD: "\u{00A7}" // §
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case 0xFE ... 0xFF: scalar(0x045E + UInt32(byte) - 0xFE) // ў џ
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default: Unicode.Scalar(byte) // ASCII, C1, NBSP (0xA0), SHY (0xAD)
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}
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}
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/// ISO-8859-2 (Latin-2, Central European). Vendored from the authoritative
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/// Unicode mapping file.
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static func iso8859_2(_ byte: UInt8) -> Unicode.Scalar {
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upperHalf(byte, latin2Upper)
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}
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/// Maps a byte through a 96-entry upper-half table (`0xA0`-`0xFF`); bytes
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/// below `0xA0` are ASCII or C1 controls (identity). Used by the encodings
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/// whose upper half is vendored from the Unicode mapping files.
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static func upperHalf(_ byte: UInt8, _ table: [UInt16]) -> Unicode.Scalar {
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byte >= 0xA0 ? scalar(UInt32(table[Int(byte) - 0xA0])) : Unicode.Scalar(byte)
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}
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static func scalar(_ value: UInt32) -> Unicode.Scalar {
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Unicode.Scalar(value) ?? "\u{FFFD}"
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}
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}
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}
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