Convert a two byte UInt8 array to a UInt16 in Swift

Question

With Swift I want to convert bytes from a uint8_t array to an integer.

\"C\" Example:

char bytes[2] = {0x01, 0x02};
NSData *data = [NSData dataWithBy         


        

Answer 1

How about

let bytes:[UInt8] = [0x01, 0x02]
let result = (UInt16(bytes[1]) << 8) + UInt16(bytes[0])

With a loop, this easily generalizes to larger byte arrays, and it can be wrapped in a function for readability:

let bytes:[UInt8] = [0x01, 0x02, 0x03, 0x04]

func bytesToUInt(byteArray: [UInt8]) -> UInt {
  assert(byteArray.count <= 4)
  var result: UInt = 0
  for idx in 0..<(byteArray.count) {
    let shiftAmount = UInt((byteArray.count) - idx - 1) * 8
    result += UInt(byteArray[idx]) << shiftAmount
  }
  return result
}

println(bytesToUInt(bytes))    // result is 16909060