PureXML/Sources/Parsing/ShiftJISDecoder.swift
Mihaela Mihaljevic 380160cc2b refactor(validation): decompose XSD instance validation into composable rules
The two monolithic XSD content/identity rules only satisfied the OpenAPIKit
validation idiom at the wrong granularity: no per-constraint removability,
no isolable failing/near-miss tests. Split them into 32 named rules, each
finding tagged at its origin and cached per XSDContext so the walk still
runs once per document (the #101 decision against duplicating XSD's
recursive type resolution still holds). Wired the streaming path's ID/IDREF
and identity checks through the same framework instead of calling the
validators imperatively, and added the unwrapAndLookup combinator the rule
already named as required.

Also includes the mandated repo-wide swiftformat/swiftlint pass.
2026-07-12 14:12:17 +02:00

72 lines
3.0 KiB
Swift

extension PureXML.Parsing.ByteDecoder {
/// The JIS X 0208 index (pointer -> code point), assembled from the vendored
/// parts. `0xFFFF` marks an unmapped pointer.
static let jis0208: [UInt16] = jis0208Part1 + jis0208Part2 + jis0208Part3
/// The Shift-JIS decoder (the WHATWG `Shift_JIS` algorithm). Single bytes cover
/// ASCII and half-width katakana; a lead byte introduces a two-byte sequence
/// resolved through the JIS X 0208 index.
enum ShiftJIS {
/// Decodes a whole Shift-JIS byte buffer.
static func decode(_ bytes: ArraySlice<UInt8>) -> String {
var scalars = String.UnicodeScalarView()
var lead: UInt8 = 0
for byte in bytes {
if lead != 0 {
let saved = lead
lead = 0
if let scalar = twoByteScalar(lead: saved, trail: byte) {
scalars.append(scalar)
} else {
scalars.append("\u{FFFD}")
if byte <= 0x7F {
scalars.append(Unicode.Scalar(byte))
} // reprocess ASCII trail
}
} else if let single = singleByteScalar(byte) {
scalars.append(single)
} else if isLead(byte) {
lead = byte
} else {
scalars.append("\u{FFFD}")
}
}
if lead != 0 {
scalars.append("\u{FFFD}")
}
return String(scalars)
}
/// The scalar for a byte that is not part of a two-byte sequence: ASCII
/// (`0x00`-`0x80`) or half-width katakana (`0xA1`-`0xDF`), else nil.
static func singleByteScalar(_ byte: UInt8) -> Unicode.Scalar? {
if byte <= 0x80 {
return Unicode.Scalar(byte)
}
if (0xA1 ... 0xDF).contains(byte) {
return Unicode.Scalar(0xFF61 + UInt32(byte) - 0xA1)
}
return nil
}
/// Whether a byte introduces a two-byte sequence.
static func isLead(_ byte: UInt8) -> Bool {
(0x81 ... 0x9F).contains(byte) || (0xE0 ... 0xFC).contains(byte)
}
/// The scalar for a `(lead, trail)` pair, or nil when the pair is invalid
/// or unmapped.
static func twoByteScalar(lead: UInt8, trail: UInt8) -> Unicode.Scalar? {
guard (0x40 ... 0x7E).contains(trail) || (0x80 ... 0xFC).contains(trail) else { return nil }
let offset = lead < 0xA0 ? 0x81 : 0xC1
let trailOffset = trail < 0x7F ? 0x40 : 0x41
let pointer = (Int(lead) - offset) * 188 + Int(trail) - trailOffset
if (8836 ... 10715).contains(pointer) {
return Unicode.Scalar(0xE000 + pointer - 8836)
} // EUDC private use
guard pointer >= 0, pointer < jis0208.count, jis0208[pointer] != 0xFFFF else { return nil }
return Unicode.Scalar(UInt32(jis0208[pointer]))
}
}
}