ByteFormatStyle

ByteFormatStyle.swift

import Foundation


struct ByteFormatStyle<Bytes> : FormatStyle, Hashable, Sendable where Bytes : Collection, Bytes.Element == UInt8 {
    typealias FormatInput = Bytes
    typealias FormatOutput = String


    var radix: Int = 16
    var uppercase: Bool = false

    var groupingSeparator: String = " "
    var groupingSize: Int = Int.bitWidth / 8

    var secondaryGroupingSeparator: String = "    "
    var secondaryGroupingSize: Int = 2

    var tertiaryGroupingSeparator: String = "\n"
    var tertiaryGroupingSize: Int = 2


    func radix(_ radix: Int, uppercase: Bool = false) -> Self {
        var copy = self
        copy.radix = radix
        copy.uppercase = uppercase
        return copy
    }


    func grouping(size: Int, separator: String = " ") -> Self {
        var copy = self
        copy.groupingSize = size
        copy.groupingSeparator = separator
        return copy
    }


    func secondaryGrouping(size: Int, separator: String = "    ") -> Self {
        var copy = self
        copy.secondaryGroupingSize = size
        copy.secondaryGroupingSeparator = separator
        return copy
    }


    func tertiaryGrouping(size: Int, separator: String = "\n") -> Self {
        var copy = self
        copy.tertiaryGroupingSize = size
        copy.tertiaryGroupingSeparator = separator
        return copy
    }


    func format(_ value: Bytes) -> String {
        let byteCharacterCount = String(UInt8.max, radix: radix).count

        var formattedString = ""

        var byteCount = 0
        var primaryGroupCount = 0
        var secondaryGroupCount = 0

        for byte in value {
            var byteString = String(byte, radix: radix, uppercase: uppercase)

            let paddingCharacterCount = byteCharacterCount - byteString.count
            if paddingCharacterCount > 0 {
                byteString.insert(
                    contentsOf: String(repeating: "0", count: paddingCharacterCount),
                    at: byteString.startIndex
                )
            }

            formattedString.append(byteString)

            byteCount += 1

            var appendPrimaryGroup = groupingSize > 0 && byteCount == groupingSize
            if appendPrimaryGroup {
                byteCount = 0
                primaryGroupCount += 1
            }

            var appendSecondaryGroup = secondaryGroupingSize > 0 && primaryGroupCount == secondaryGroupingSize
            if appendSecondaryGroup {
                appendPrimaryGroup = false
                primaryGroupCount = 0
                secondaryGroupCount += 1
            }

            let appendTertiaryGroup = tertiaryGroupingSize > 0 && secondaryGroupCount == tertiaryGroupingSize
            if appendTertiaryGroup {
                appendSecondaryGroup = false
                secondaryGroupCount = 0
            }

            if appendTertiaryGroup {
                formattedString.append(tertiaryGroupingSeparator)
            } else if appendSecondaryGroup {
                formattedString.append(secondaryGroupingSeparator)
            } else if appendPrimaryGroup {
                formattedString.append(groupingSeparator)
            }
        }

        return formattedString
    }
}


let randomData = Data((0 ..< 128).map { _ in UInt8.random(in: .min ... .max) })

let formatStyle = ByteFormatStyle<Data>()
    .radix(16, uppercase: true)
    .grouping(size: 4, separator: " ")
    .secondaryGrouping(size: 4, separator: "    ")
    .tertiaryGrouping(size: 2, separator: "\n")

print(formatStyle.format(randomData))

// 1616EC47 3BB6D892 85C86BBD 2841EBC8    6DD27D77 E1043EF9 EAD76A98 12720DC8
// 4F0D0F68 08578EDA B53D3517 39E93BAB    42D323BB 29A4FA9E 1DEDAC5F 29F3C92A
// 3BB5E5A3 3DCAF028 27A6D6D4 CCB492BA    53ED4C1F F1CF886A 9D9B0BAD A0C04AC8
// 10334DFB 74502BEF 836BC0FD 00E02605    83FFC261 0A4BB137 0D25068C 7B92421D