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/// A membership test over the ASCII range (bytes `0`–`127`)
/// We use this for performance, since markers are always ASCII, and this this
/// faster than using Character.
struct ASCIIByteSet {
private let low: UInt64
private let high: UInt64
/// Builds a set from the ASCII values.
init(_ characters: String) {
var lo: UInt64 = 0
var hi: UInt64 = 0
for byte in characters.utf8 {
if byte < 64 {
lo |= 1 << UInt64(byte)
} else if byte < 128 {
hi |= 1 << UInt64(byte - 64)
}
}
low = lo
high = hi
}
/// Whether `byte` is in the set.
@inline(__always)
func contains(_ byte: UInt8) -> Bool {
if byte < 64 { return low & (1 << UInt64(byte)) != 0 }
if byte < 128 { return high & (1 << UInt64(byte &- 64)) != 0 }
return false
}
}
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