82 lines
3.1 KiB
Swift
82 lines
3.1 KiB
Swift
public extension PureXML.Parsing {
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/// A character encoding PureXML can decode from raw bytes. Covers the
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/// Unicode transformation formats plus the single-byte encodings (ISO-8859-1,
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/// ISO-8859-5/9/15, and Windows-1252), toward libxml2 encoding parity.
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enum InputEncoding: String, Equatable, Sendable {
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case utf8
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case utf16BigEndian
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case utf16LittleEndian
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case utf32BigEndian
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case utf32LittleEndian
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case latin1
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case windows1252
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case windows1254 // Turkish
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case latin2 // ISO-8859-2
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case latin3 // ISO-8859-3
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case latin4 // ISO-8859-4
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case greek // ISO-8859-7
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case latin7 // ISO-8859-13
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case arabic // ISO-8859-6
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case hebrew // ISO-8859-8
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case latin6 // ISO-8859-10
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case latin8 // ISO-8859-14
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case latin10 // ISO-8859-16
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case thai // ISO-8859-11
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case windows1250
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case windows1251
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case windows1253
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case windows1257
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case windows1255
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case windows1256
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case windows1258
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case koi8r
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case koi8u
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case latinCyrillic // ISO-8859-5
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case latin5 // ISO-8859-9 (Turkish)
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case latin9 // ISO-8859-15
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/// Detects the encoding from the leading bytes, following the XML sniff
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/// order: a byte-order mark first, then the `<?` byte pattern of the XML
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/// declaration, defaulting to UTF-8. Single-byte encodings are not
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/// detectable from bytes alone; they come from the declared encoding name.
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public static func detect(_ bytes: [UInt8]) -> InputEncoding {
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detectWithBOM(bytes).encoding
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}
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/// Detects the encoding and the length of any byte-order mark to strip.
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static func detectWithBOM(_ bytes: [UInt8]) -> (encoding: InputEncoding, bomLength: Int) {
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if bytes.starts(with: [0xEF, 0xBB, 0xBF]) {
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return (.utf8, 3)
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}
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// UTF-32 marks are four bytes and must be checked before UTF-16, since
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// the UTF-32LE mark begins with the UTF-16LE mark.
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if bytes.starts(with: [0x00, 0x00, 0xFE, 0xFF]) {
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return (.utf32BigEndian, 4)
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}
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if bytes.starts(with: [0xFF, 0xFE, 0x00, 0x00]) {
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return (.utf32LittleEndian, 4)
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}
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if bytes.starts(with: [0xFE, 0xFF]) {
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return (.utf16BigEndian, 2)
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}
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if bytes.starts(with: [0xFF, 0xFE]) {
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return (.utf16LittleEndian, 2)
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}
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// No BOM: sniff the "<?" byte pattern of an XML declaration.
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if bytes.starts(with: [0x00, 0x00, 0x00, 0x3C]) {
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return (.utf32BigEndian, 0)
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}
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if bytes.starts(with: [0x3C, 0x00, 0x00, 0x00]) {
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return (.utf32LittleEndian, 0)
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}
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if bytes.starts(with: [0x00, 0x3C, 0x00, 0x3F]) {
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return (.utf16BigEndian, 0)
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}
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if bytes.starts(with: [0x3C, 0x00, 0x3F, 0x00]) {
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return (.utf16LittleEndian, 0)
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}
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return (.utf8, 0)
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}
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}
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}
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