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[perf] Make an ASCII check faster by enabling the compiler to leverage SIMD instructions #3469

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[perf] Make an ASCII check faster by enabling the compiler to leverage SIMD instructions #3469

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11 changes: 8 additions & 3 deletions Sources/NIOHTTP1/HTTPTypes.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -257,9 +257,14 @@ extension HTTPResponseHead {
}
}

extension UInt8 {
extension String.UTF8View {
/// Determines if this `UTF8View` corresponds to an `String` which contains only ASCII characters.
fileprivate var isASCII: Bool {
self <= 127
var result: UInt8 = 0
for byte in self {
result |= byte
}
return result <= 127
}
}

Expand Down Expand Up @@ -361,7 +366,7 @@ public struct HTTPHeaders: CustomStringConvertible, ExpressibleByDictionaryLiter
/// recommended.
/// - Parameter value: The header field value to add for the given name.
public mutating func add(name: String, value: String) {
precondition(!name.utf8.contains(where: { !$0.isASCII }), "name must be ASCII")
precondition(!name.utf8.isASCII, "name must be ASCII")
self.headers.append((name, value))
if self.isConnectionHeader(name) {
self.keepAliveState = .unknown
Expand Down