CryptoSwift/Sources/CryptoSwift/UInt16+Extension.swift

//
//  UInt16+Extension.swift
//  CryptoSwift
//
//  Copyright (C) 2014-2017 Marcin Krzyżanowski <marcin@krzyzanowskim.com>
//  This software is provided 'as-is', without any express or implied warranty.
//
//  In no event will the authors be held liable for any damages arising from the use of this software.
//
//  Permission is granted to anyone to use this software for any purpose,including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:
//
//  - The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation is required.
//  - Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
//  - This notice may not be removed or altered from any source or binary distribution.
//

/** array of bytes */
extension UInt16 {

    @_specialize(exported: true, where T == ArraySlice<UInt8>)
    init<T: Collection>(bytes: T) where T.Element == UInt8, T.Index == Int {
        self = UInt16(bytes: bytes, fromIndex: bytes.startIndex)
    }

    @_specialize(exported: true, where T == ArraySlice<UInt8>)
    init<T: Collection>(bytes: T, fromIndex index: T.Index) where T.Element == UInt8, T.Index == Int {
        if bytes.isEmpty {
            self = 0
            return
        }

        let count = bytes.count

        let val0 = count > 0 ? UInt16(bytes[index.advanced(by: 0)]) << 8 : 0
        let val1 = count > 1 ? UInt16(bytes[index.advanced(by: 1)]) : 0

        self = val0 | val1
    }
}