crc-8, crc-16 and crc-32 implementations

Playgrounds/CRC16.playground/Contents.swift

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+//
+// CRC16.swift
+//
+// Copyright © 2020 QuickBird Studios. All rights reserved.
+//
+
+import Foundation
+
+let crc16 = CRC16()
+
+crc16.currentValue // initial value is 0
+crc16.append(1.0)
+crc16.append(1) // we are passing integer (If you want to pass UInt8, see the line below)
+crc16.append(UInt8(1))
+crc16.append([1, 20]) // We are passing [UInt8] (because that is the only type of array the append method accepts)
+
+// get the current crc value
+crc16.currentValue
+
+// append more
+crc16.append(5.6)
+crc16.append(225)
+
+// get the current crc value
+crc16.currentValue
+
+// reset the crc value
+crc16.reset()
+
+crc16.currentValue // value is 0 after reset
+
+
+// CRC16's lookup table
+crc16.lookupTable
+
+// CRC16's lookup table (hexadecimal representation)
+let lookupTableHexa = crc16.lookupTable.map { String($0, radix: 16) }
+lookupTableHexa

Playgrounds/CRC16.playground/Sources/CRC.swift

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+//
+// CRC.swift
+//
+// Copyright © 2020 QuickBird Studios. All rights reserved.
+//
+
+import Foundation
+
+public protocol CRC {
+ associatedtype Size
+
+ var currentValue: Size { get }
+
+ func append(_ bytes: [UInt8])
+
+ func reset()
+}
+
+extension CRC {
+ public func append(_ byte: UInt8) {
+ append([byte])
+ }
+
+ public func append<T: FixedWidthInteger>(_ integer: T) {
+ append(integer.bigEndianBytes)
+ }
+
+ public func append<T: BinaryFloatingPoint>(_ floatingPoint: T) {
+ append(floatingPoint.bigEndianBytes)
+ }
+}
+
+extension FixedWidthInteger {
+ public var bigEndianBytes: [UInt8] {
+ [UInt8](withUnsafeBytes(of: self.bigEndian) { Data($0) })
+ }
+}
+
+// Please keep in mind that Float has different representations and you need to make sure
+// you are using the same representation as the system you are communicating with
+extension BinaryFloatingPoint {
+ public var bigEndianBytes: [UInt8] {
+ [UInt8](withUnsafeBytes(of: self) { Data($0) }).reversed()
+ }
+}

Playgrounds/CRC16.playground/Sources/CRC16.swift

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+//
+// CRC16.swift
+//
+// Copyright © 2020 QuickBird Studios. All rights reserved.
+//
+
+import Foundation
+
+/// Class to conveniently calculate CRC-16. It uses the CRC16-CCITT polynomial (0x1021) by default
+public class CRC16: CRC {
+
+ /// The table that stores the precomputed remainders for all possible divisions for 1 byte
+ /// This table is used as a lookup (to speed up the calculation)
+ public let lookupTable: [UInt16]
+
+ private(set) public var currentValue: UInt16 = 0
+
+ /// Creates the instance for calculating CRC
+ /// - Parameter polynomial: The polynomial to use. It uses CRC16-CCITT's polynomial (0x1021) by default
+ public init(polynomial: UInt16 = 0x1021) {
+ /// Generates the lookup table (make sure to generate it only once)
+ self.lookupTable = (0...255).map { Self.crc16(for: UInt8($0), polynomial: polynomial) }
+ }
+
+ public func append(_ bytes: [UInt8]) {
+ currentValue = crc16(for: bytes, initialValue: currentValue)
+ }
+
+ public func reset() {
+ currentValue = 0
+ }
+}
+
+/// Same code as the blog article
+extension CRC16 {
+ /// Caculates CRC-16 of an array of Bytes (UInt8)
+ private func crc16(for inputs: [UInt8], initialValue: UInt16 = 0) -> UInt16 {
+ inputs.reduce(initialValue) { remainder, byte in
+ let bigEndianInput = UInt16(byte).bigEndian
+ let index = (bigEndianInput ^ remainder) >> 8
+ return lookupTable[Int(index)] ^ (remainder << 8)
+ }
+ }
+
+ /// Calculates the CRC-16 of 1 Byte
+ private static func crc16(for input: UInt8, polynomial: UInt16) -> UInt16 {
+ var result = UInt16(input).bigEndian
+ for _ in 0..<8 {
+ let isMostSignificantBitOne = result & 0x8000 != 0
+
+ result = result << 1
+
+ if isMostSignificantBitOne {
+ result = result ^ polynomial
+ }
+ }
+
+ return result
+ }
+}

Playgrounds/CRC16.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true'>
+ <timeline fileName='timeline.xctimeline'/>
+</playground>

Playgrounds/CRC16.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+ <key>IDEDidComputeMac32BitWarning</key>
+ <true/>
+</dict>
+</plist>

Playgrounds/CRC16.playground/xcuserdata/nasir.xcuserdatad/xcschemes/xcschememanagement.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+ <key>SchemeUserState</key>
+ <dict>
+ <key>CRC16 (Playground).xcscheme</key>
+ <dict>
+ <key>isShown</key>
+ <false/>
+ <key>orderHint</key>
+ <integer>0</integer>
+ </dict>
+ </dict>
+</dict>
+</plist>

Playgrounds/CRC32.playground/Contents.swift

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+//
+// CRC32.playground
+//
+// Copyright © 2020 QuickBird Studios. All rights reserved.
+//
+
+import Foundation
+
+let crc32 = CRC32()
+
+crc32.currentValue // initial value is 0
+crc32.append(1.0)
+crc32.append(1) // we are passing integer (If you want to pass UInt8, see the line below)
+crc32.append(UInt8(1))
+crc32.append([1, 20]) // We are passing [UInt8] (because that is the only type of array the append method accepts)
+
+// get the current crc value
+crc32.currentValue
+
+// append more
+crc32.append(5.6)
+crc32.append(225)
+
+// get the current crc value
+crc32.currentValue
+
+// reset the crc value
+crc32.reset()
+
+crc32.currentValue // value is 0 after reset
+
+
+// CRC32's lookup table
+crc32.lookupTable
+
+// CRC32's lookup table (hexadecimal representation)
+let lookupTableHexa = crc32.lookupTable.map { String($0, radix: 16) }

Playgrounds/CRC32.playground/Sources/CRC.swift

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+//
+// CRC.swift
+//
+// Copyright © 2020 QuickBird Studios. All rights reserved.
+//
+
+import Foundation
+
+public protocol CRC {
+ associatedtype Size
+
+ var currentValue: Size { get }
+
+ func append(_ bytes: [UInt8])
+
+ func reset()
+}
+
+extension CRC {
+ public func append(_ byte: UInt8) {
+ append([byte])
+ }
+
+ public func append<T: FixedWidthInteger>(_ integer: T) {
+ append(integer.bigEndianBytes)
+ }
+
+ public func append<T: BinaryFloatingPoint>(_ floatingPoint: T) {
+ append(floatingPoint.bigEndianBytes)
+ }
+}
+
+// MARK: - Convenience Extension Methods
+
+extension FixedWidthInteger {
+ public var bigEndianBytes: [UInt8] {
+ [UInt8](withUnsafeBytes(of: self.bigEndian) { Data($0) })
+ }
+}
+
+// `BinaryFloatingPoint` conforms to 754-2008 - IEEE Standard for Floating-Point Arithmetic (https://ieeexplore.ieee.org/document/4610935)
+// If you target system is using a different floating point representation, you need to adapt accordingly
+extension BinaryFloatingPoint {
+ public var bigEndianBytes: [UInt8] {
+ [UInt8](withUnsafeBytes(of: self) { Data($0) }).reversed()
+ }
+}

Playgrounds/CRC32.playground/Sources/CRC32.swift

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+//
+// CRC32.swift
+//
+// Copyright © 2020 QuickBird Studios. All rights reserved.
+//
+
+import Foundation
+
+/// Class to conveniently calculate CRC-32 It uses the CRC32 polynomial (0x04C11DB7) by default
+public class CRC32: CRC {
+
+ /// The table that stores the precomputed remainders for all possible divisions for 1 byte
+ /// This table is used as a lookup (to speed up the calculation)
+ public let lookupTable: [UInt32]
+
+ private(set) public var currentValue: UInt32 = 0
+
+ /// Creates the instance for calculating CRC
+ /// - Parameter polynomial: The polynomial to use. It uses CRC32's polynomial (0x04C11DB7) by default
+ public init(polynomial: UInt32 = 0x04C11DB7) {
+ /// Generates the lookup table (make sure to generate it only once)
+ self.lookupTable = (0...255).map { Self.crc32(for: UInt8($0), polynomial: polynomial) }
+ }
+
+ public func append(_ bytes: [UInt8]) {
+ currentValue = crc32(for: bytes, initialValue: currentValue)
+ }
+
+ public func reset() {
+ currentValue = 0
+ }
+}
+
+extension CRC32 {
+ /// Caculates CRC-32 of an array of Bytes (UInt8)
+ private func crc32(for inputs: [UInt8], initialValue: UInt32 = 0) -> UInt32 {
+ inputs.reduce(initialValue) { remainder, byte in
+ let bigEndianInput = UInt32(byte).bigEndian
+ let index = (bigEndianInput ^ remainder) >> 24
+ return lookupTable[Int(index)] ^ (remainder << 8)
+ }
+ }
+
+ /// Calculates the CRC-32 of 1 Byte
+ private static func crc32(for input: UInt8, polynomial: UInt32) -> UInt32 {
+ var result = UInt32(input).bigEndian
+ for _ in 0..<8 {
+ let isMostSignificantBitOne = result & 0x80000000 != 0
+
+ result = result << 1
+
+ if isMostSignificantBitOne {
+ result = result ^ polynomial
+ }
+ }
+
+ return result
+ }
+}

Playgrounds/CRC32.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true'>
+ <timeline fileName='timeline.xctimeline'/>
+</playground>

Playgrounds/CRC32.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+ <key>IDEDidComputeMac32BitWarning</key>
+ <true/>
+</dict>
+</plist>

Playgrounds/CRC8.playground/Contents.swift

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+//
+// CRC8.playground
+//
+// Copyright © 2020 QuickBird Studios. All rights reserved.
+//
+
+import Foundation
+
+let crc8 = CRC8()
+
+crc8.currentValue // initial value is 0
+crc8.append(1.0)
+crc8.append(1) // we are passing integer (If you want to pass UInt8, see the line below)
+crc8.append(UInt8(1))
+crc8.append([1, 20]) // We are passing [UInt8] (because that is the only type of array the append method accepts)
+
+// get the current crc value
+crc8.currentValue
+
+// append more
+crc8.append(5.6)
+crc8.append(225)
+
+// get the current crc value
+crc8.currentValue
+
+// reset the crc value
+crc8.reset()
+
+crc8.currentValue // value is 0 after reset
+
+
+// CRC8's lookup table
+crc8.lookupTable
+
+// CRC8's lookup table (hexadecimal representation)
+let lookupTableHexa = crc8.lookupTable.map { String($0, radix: 16) }
+lookupTableHexa