Swift hexdump function

hexdump.swift

import Cocoa

func printHexdump(data: Data) {
    print("\n           0  1  2  3  4  5  6  7   8  9  a  b  c  d  e  f")
    print("-----------------------------------------------------------------------------")
    var i = 0
    var bytes: [UInt8] = []
    while i < data.count {
        if i % 16 == 0 {
            // Write ASCII at end of previous line
            if !bytes.isEmpty {
                print("  \(String(bytes: bytes, encoding: .ascii)!)")
                bytes = []
            }
            
            // Write offset for this line
            print(String(format: "%08x ", i), terminator: "")
        }
        else if i % 8 == 0 {
            // Extra space between first eight bytes and last eight bytes
            print(" ", terminator: "")
        }
        
        let byte = data[i]
        print(String(format: " %02x", byte), terminator: "")
        if byte >= 0x20 && byte <= 0x7e {
            bytes.append(byte)
        } else {
            bytes.append(0x2e)  // '.'
        }
        
        i += 1
    }
    
    // Handle any remaining whitespace to fill 16-byte line.
    while i % 16 != 0 {
        if i % 8 == 0 {
            // Extra space between first eight bytes and last eight bytes
            print(" ", terminator: "")
        }
        print(" ..", terminator: "")
        bytes.append(0x20)  // ' '
        i += 1
    }
    if !bytes.isEmpty {
        print("  \(String(bytes: bytes, encoding: .ascii)!)")
    }
    
    print("\n")
}

let data = "One ring to rule them all, one ring to find them, one ring to bring them close and in the darkness bind them!".data(using: .utf8)!
printHexdump(data: data)

/* Example output

           0  1  2  3  4  5  6  7   8  9  a  b  c  d  e  f
-----------------------------------------------------------------------------
00000000  4f 6e 65 20 72 69 6e 67  20 74 6f 20 72 75 6c 65  One ring to rule
00000010  20 74 68 65 6d 20 61 6c  6c 2c 20 6f 6e 65 20 72   them all, one r
00000020  69 6e 67 20 74 6f 20 66  69 6e 64 20 74 68 65 6d  ing to find them
00000030  2c 20 6f 6e 65 20 72 69  6e 67 20 74 6f 20 62 72  , one ring to br
00000040  69 6e 67 20 74 68 65 6d  20 63 6c 6f 73 65 20 61  ing them close a
00000050  6e 64 20 69 6e 20 74 68  65 20 64 61 72 6b 6e 65  nd in the darkne
00000060  73 73 20 62 69 6e 64 20  74 68 65 6d 21 .. .. ..  ss bind them!   

*/