import Foundation
extension Array {
subscript (safe index: Int) -> Element? {
// iOS 9 or later
return indices ~= index ? self[index] : nil
}
}
// MARK: Hex String to Array
extension Array {
init(reserveCapacity: Int) {
self = Array<Element>()
self.reserveCapacity(reserveCapacity)
}
var slice: ArraySlice<Element> {
self[self.startIndex ..< self.endIndex]
}
}
extension Array where Element == UInt8 {
public init(hex: String) {
self.init(reserveCapacity: hex.unicodeScalars.lazy.underestimatedCount)
var buffer: UInt8?
var skip = hex.hasPrefix("0x") ? 2 : 0
for char in hex.unicodeScalars.lazy {
guard skip == 0 else {
skip -= 1
continue
}
guard char.value >= 48 && char.value <= 102 else {
removeAll()
return
}
let v: UInt8
let c: UInt8 = UInt8(char.value)
switch c {
case let c where c <= 57:
v = c - 48
case let c where c >= 65 && c <= 70:
v = c - 55
case let c where c >= 97:
v = c - 87
default:
removeAll()
return
}
if let b = buffer {
append(b << 4 | v)
buffer = nil
} else {
buffer = v
}
}
if let b = buffer {
append(b)
}
}
public func toHexString() -> String {
`lazy`.reduce(into: "") {
var s = String($1, radix: 16)
if s.count == 1 {
s = "0" + s
}
$0 += s
}
}
}
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