Convert bytes/UInt8 array to Int in Swift

Question

How to convert a 4-bytes array into the corresponding Int?

let array: [UInt8] ==> let value : Int

Example:

Input:

Answer 1

Updated for Swift 5, two things to pay attention:

• As [UInt8] is stored in a contiguous region of memory, there's no need to convert it to Data, pointer can access all bytes directly.

• Int's byte order is little endian currently on all Apple platform, but this is not garanteed on other platforms.

say we want [0, 0, 0, 0x0e] to convert to 14. (big-endian byte order)

let source: [UInt8] = [0, 0, 0, 0x0e]
let bigEndianUInt32 = source.withUnsafeBytes { $0.load(as: UInt32.self) }
let value = CFByteOrderGetCurrent() == CFByteOrder(CFByteOrderLittleEndian.rawValue)
    ? UInt32(bigEndian: bigEndianUInt32)
    : bigEndianUInt32
print(value) // 14