Like hexdump -C but in Swift 4.1

hexdump.swift

import Foundation


/// Writes a canonical hex+ASCII representation of `bytes` into `output`.
func hexdump<Target>(_ bytes: UnsafeRawBufferPointer, to output: inout Target)
    where Target: TextOutputStream
{
    guard bytes.count > 0 else { return }
    var asciiString = ""
    func startRow(offset: Int) {
        print(String(format: "%08x", offset), terminator: "  ", to: &output)
        asciiString = ""
    }
    for byteIndex in bytes.indices {
        if byteIndex & 15 == 0 { startRow(offset: byteIndex) }
        let byteValue = bytes[byteIndex]
        print(String(format: "%02x", byteValue), terminator: " ", to: &output)
        if byteIndex & 7 == 7 { print(terminator: " ", to: &output) }
        let asciiChar = (0x20 ... 0x7e).contains(byteValue) ? byteValue : 0x2e
        asciiString.append(String(UnicodeScalar(asciiChar)))
        if byteIndex & 15 == 15 { print("|" + asciiString + "|", to: &output) }
    }
    let emptyColumns = 15 - ((bytes.count - 1) & 15)
    if emptyColumns > 0 {
        let spaces = String(repeating: " ", count: (emptyColumns * 28) / 9)
        print(spaces, "|" + asciiString + "|", to: &output)
    }
    startRow(offset: bytes.count)
    print(terminator: "\n", to: &output)
}

/// Writes a canonical hex+ASCII representation of `bytes` to standard output.
func hexdump(_ bytes: UnsafeRawBufferPointer) {
    struct StdOut : TextOutputStream {
        mutating func write(_ string: String) { print(string, terminator: "") }
    }
    var hexdumpStdOut = StdOut()
    hexdump(bytes, to: &hexdumpStdOut)
}

"👋Hello world!🌎".utf8.map({ $0 }).withUnsafeBytes(hexdump)
var log = "\nAll the bytes:\n"
(0 ... 255).map { UInt8($0) }.withUnsafeBytes { hexdump($0, to: &log) }
log += "\nSome random UInt32 values:\n"
(0 ..< 123).map { _ in arc4random() }.withUnsafeBytes { hexdump($0, to: &log) }
print(log)