Mihaela Mihaljevic
85172923e8
Decode UTF-32 (both byte orders, BOM or sniffed) and the single-byte encodings ISO-8859-1 and Windows-1252, selected by the XML declaration's encoding name, in addition to UTF-8 and UTF-16. The streaming byte path also handles UTF-32. Standard library only, no Foundation. Closes #28. Reimplemented from the documented encoding algorithms; no upstream code copied. 4 tests; 94 total.
58 lines
2.4 KiB
Swift
58 lines
2.4 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 common single-byte encodings
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/// (ISO-8859-1 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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/// 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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