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//===--- ASCII.swift ------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
extension Unicode {
@frozen
public enum ASCII {}
}
extension Unicode.ASCII: Unicode.Encoding {
public typealias CodeUnit = UInt8
public typealias EncodedScalar = CollectionOfOne<CodeUnit>
@inlinable
public static var encodedReplacementCharacter: EncodedScalar {
return EncodedScalar(0x1a) // U+001A SUBSTITUTE; best we can do for ASCII
}
/// Returns whether the given code unit represents an ASCII scalar
@_alwaysEmitIntoClient
public static func isASCII(_ x: CodeUnit) -> Bool { return UTF8.isASCII(x) }
@inline(__always)
@inlinable
public static func _isScalar(_ x: CodeUnit) -> Bool {
return true
}
@inline(__always)
@inlinable
public static func decode(_ source: EncodedScalar) -> Unicode.Scalar {
return Unicode.Scalar(_unchecked: UInt32(
source.first._unsafelyUnwrappedUnchecked))
}
@inline(__always)
@inlinable
public static func encode(
_ source: Unicode.Scalar
) -> EncodedScalar? {
guard source.value < (1&<<7) else { return nil }
return EncodedScalar(UInt8(truncatingIfNeeded: source.value))
}
@inline(__always)
@inlinable
public static func transcode<FromEncoding: Unicode.Encoding>(
_ content: FromEncoding.EncodedScalar, from _: FromEncoding.Type
) -> EncodedScalar? {
if _fastPath(FromEncoding.self == UTF16.self) {
let c = _identityCast(content, to: UTF16.EncodedScalar.self)
guard (c._storage & 0xFF80 == 0) else { return nil }
return EncodedScalar(CodeUnit(c._storage & 0x7f))
}
else if _fastPath(FromEncoding.self == UTF8.self) {
let c = _identityCast(content, to: UTF8.EncodedScalar.self)
let first = c.first.unsafelyUnwrapped
guard (first < 0x80) else { return nil }
return EncodedScalar(CodeUnit(first))
}
return encode(FromEncoding.decode(content))
}
@frozen
public struct Parser {
@inlinable
public init() { }
}
public typealias ForwardParser = Parser
public typealias ReverseParser = Parser
}
extension Unicode.ASCII.Parser: Unicode.Parser {
public typealias Encoding = Unicode.ASCII
/// Parses a single Unicode scalar value from `input`.
@inlinable
public mutating func parseScalar<I: IteratorProtocol>(
from input: inout I
) -> Unicode.ParseResult<Encoding.EncodedScalar>
where I.Element == Encoding.CodeUnit {
let n = input.next()
if _fastPath(n != nil), let x = n {
guard _fastPath(Int8(truncatingIfNeeded: x) >= 0)
else { return .error(length: 1) }
return .valid(Unicode.ASCII.EncodedScalar(x))
}
return .emptyInput
}
}
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