Swift 3 ArraySlice setBytes extension

ArraySlice+SetBytes.swift

import Foundation

extension ArraySlice {
  // Overwrites the ArraySlice region with the passed-in array of bytes
  mutating func setBytes(_ from: [UInt8]) {
    var fromIter = from.makeIterator()
    self.withUnsafeMutableBytes { bytes in
      for i in stride(from: bytes.startIndex, to: bytes.endIndex - 1, by: 1) {
        if let fromByte = fromIter.next() {
          bytes[i] = fromByte
        }
      }
    }
  }

  // Converts its parameter to a byte memory image (e.g. UInt32 as 
  // a length 4 array of UInt8) and overwrites the slice.
  // 
  mutating func setBytes<T>(_ from: T) {
    var buffer = from
    let count = MemoryLayout<T>.size
    let bytePtr = withUnsafePointer(to: &buffer) {
      $0.withMemoryRebound(to: UInt8.self, capacity: count) {
        UnsafeBufferPointer(start: $0, count: count)
      }
    }
    
    let byteArray = Array(bytePtr)
    self.setBytes(byteArray)
  }
}