Write extend file attributes swift example - ios

I am looking for a solution to add extended file attributes for a file in swift. I checked this link Write extended file attributes, but the solutions are in objective c and I need a solution for swift.

Here is a possible implementation in Swift 5 as an extension for URL,
with methods to get, set, list, and remove extended attributes of
a file. (Swift 2, 3, and 4 code can be found in the edit history.)
extension URL {
/// Get extended attribute.
func extendedAttribute(forName name: String) throws -> Data {
let data = try self.withUnsafeFileSystemRepresentation { fileSystemPath -> Data in
// Determine attribute size:
let length = getxattr(fileSystemPath, name, nil, 0, 0, 0)
guard length >= 0 else { throw URL.posixError(errno) }
// Create buffer with required size:
var data = Data(count: length)
// Retrieve attribute:
let result = data.withUnsafeMutableBytes { [count = data.count] in
getxattr(fileSystemPath, name, $0.baseAddress, count, 0, 0)
}
guard result >= 0 else { throw URL.posixError(errno) }
return data
}
return data
}
/// Set extended attribute.
func setExtendedAttribute(data: Data, forName name: String) throws {
try self.withUnsafeFileSystemRepresentation { fileSystemPath in
let result = data.withUnsafeBytes {
setxattr(fileSystemPath, name, $0.baseAddress, data.count, 0, 0)
}
guard result >= 0 else { throw URL.posixError(errno) }
}
}
/// Remove extended attribute.
func removeExtendedAttribute(forName name: String) throws {
try self.withUnsafeFileSystemRepresentation { fileSystemPath in
let result = removexattr(fileSystemPath, name, 0)
guard result >= 0 else { throw URL.posixError(errno) }
}
}
/// Get list of all extended attributes.
func listExtendedAttributes() throws -> [String] {
let list = try self.withUnsafeFileSystemRepresentation { fileSystemPath -> [String] in
let length = listxattr(fileSystemPath, nil, 0, 0)
guard length >= 0 else { throw URL.posixError(errno) }
// Create buffer with required size:
var namebuf = Array<CChar>(repeating: 0, count: length)
// Retrieve attribute list:
let result = listxattr(fileSystemPath, &namebuf, namebuf.count, 0)
guard result >= 0 else { throw URL.posixError(errno) }
// Extract attribute names:
let list = namebuf.split(separator: 0).compactMap {
$0.withUnsafeBufferPointer {
$0.withMemoryRebound(to: UInt8.self) {
String(bytes: $0, encoding: .utf8)
}
}
}
return list
}
return list
}
/// Helper function to create an NSError from a Unix errno.
private static func posixError(_ err: Int32) -> NSError {
return NSError(domain: NSPOSIXErrorDomain, code: Int(err),
userInfo: [NSLocalizedDescriptionKey: String(cString: strerror(err))])
}
}
Example usage:
let fileURL = URL(fileURLWithPath: "/path/to/file")
let attr1 = "com.myCompany.myAttribute"
let attr2 = "com.myCompany.otherAttribute"
let data1 = Data([1, 2, 3, 4])
let data2 = Data([5, 6, 7, 8, 9])
do {
// Set attributes:
try fileURL.setExtendedAttribute(data: data1, forName: attr1)
try fileURL.setExtendedAttribute(data: data2, forName: attr2)
// List attributes:
let list = try fileURL.listExtendedAttributes()
print(list)
// ["com.myCompany.myAttribute", "com.myCompany.otherAttribute", "other"]
let data1a = try fileURL.extendedAttribute(forName: attr1)
print(data1a as NSData)
// <01020304>
// Remove attributes
for attr in list {
try fileURL.removeExtendedAttribute(forName: attr)
}
} catch let error {
print(error.localizedDescription)
}

Related

Unwrapping optional value (returned by data.withUnsafeBytes(_:)) sometimes does not work with guard let

I have issue with guard let statement, which behaves strange. Whole code is below. Else block of statement guard let data = readData, let size = sizeOfData else ... in method readActivity(subdata: Data) is wrongly executed even thoug readData and sizeOfData are not nil.
Code
import Foundation
enum ActivityDataReaderError: Error {
case activityIsReadingOtherCentral
case bluetooth(Error?)
case staleData
}
protocol ActivityDataReaderDelegate: class {
func didReadActivity(data: Data)
func didFailToReadActivity(error: ActivityDataReaderError)
}
final class ActivityDataReader {
private var sizeOfData: Int?
private var isOtherDeviceReading: Bool {
// 0xFFFF
return sizeOfData == 65535
}
private var readData: Data?
var isEmpty: Bool {
return sizeOfData == nil
}
weak var delegate: ActivityDataReaderDelegate?
static func timestampValue(_ timestamp: UInt32) -> Data {
var value = timestamp
return Data(buffer: UnsafeBufferPointer(start: &value, count: 1))
}
func reset() {
readData = nil
sizeOfData = nil
NSLog("reset() -- \(Thread.current)")
}
func readActivity(data: Data?, error: Error? = nil) {
guard let data = data else {
delegate?.didFailToReadActivity(error: .bluetooth(error))
return
}
let isFirstChunk = readData == nil
if isFirstChunk {
let sizeData = data.subdata(in: 0..<2)
sizeOfData = sizeData.withUnsafeBytes { $0.pointee }
guard !isOtherDeviceReading else {
delegate?.didFailToReadActivity(error: .activityIsReadingOtherCentral)
return
}
NSLog(String("readActivity() Size of data: \(String(describing: sizeOfData))"))
let subdata = data.subdata(in: 2..<data.count)
readActivity(subdata: subdata)
} else {
readActivity(subdata: data)
}
}
private func readActivity(subdata: Data) {
if let lastReadData = readData {
readData = lastReadData + subdata
} else {
readData = subdata
}
guard let data = readData, let size = sizeOfData else {
NSLog("WTF? data:\(String(describing: readData)), "
+ "sizeOfData: \(String(describing: sizeOfData)), "
+ "thread: \(Thread.current)")
assertionFailure("WTF")
return
}
NSLog("subdata: \(String(describing: subdata)), "
+ "totalReadBytes: \(data.count), "
+ "size: \(size)")
if data.count == size {
delegate?.didReadActivity(data: data)
reset()
}
}
}
Test
Test which sometimes passes and sometimes crashes because of assertionFailure("WTF").
class ActivityDataServiceReaderTests: XCTestCase {
var service: ActivityDataReader?
override func setUp() {
super.setUp()
service = ActivityDataReader()
}
override func tearDown() {
service = nil
super.tearDown()
}
func testBufferIsNotEmpty() {
NSLog("testBufferIsNotEmpty thread: \(Thread.current)")
guard let service = service else { fatalError() }
let firstDataBytes = [UInt8.min]
let data1 = Data(bytes: [7, 0] + firstDataBytes)
service.readActivity(data: data1)
XCTAssertFalse(service.isEmpty)
service.reset()
XCTAssertTrue(service.isEmpty)
}
}
Log of console in case of crash
2018-10-25 14:53:30.033573+0200 GuardBug[84042:11188210] WTF? data:Optional(1 bytes), sizeOfData: Optional(7), thread: <NSThread: 0x600003399d00>{number = 1, name = main}
Environment
Xcode10
swift 4.1 with legacy build system
swift 4.2
In my opinion, there is no possible way to execute code in else block in guard let else block of method readActivity(subdata: Data). Everything is running on main thread. Am I misssing something? How is possible sometimes test passes and sometimes crasshes?
Thank you for any help.
Edit:
More narrow problem of guard let + data.withUnsafeBytes:
func testGuardLet() {
let data = Data(bytes: [7, 0, UInt8.min])
let sizeData = data.subdata(in: 0 ..< 2)
let size: Int? = sizeData.withUnsafeBytes { $0.pointee }
guard let unwrappedSize = size else {
NSLog("failure: \(size)")
XCTFail()
return
}
NSLog("success: \(unwrappedSize)")
}
Log:
2018-10-25 16:32:19.497540+0200 GuardBug[90576:11351167] failure: Optional(7)
Thanks to help at: https://forums.swift.org/t/unwrapping-value-with-guard-let-sometimes-does-not-work-with-result-from-data-withunsafebytes-0-pointee/17357 problem was with the line:
let size: Int? = sizeData.withUnsafeBytes { $0.pointee }
Where read data was downcasted to Optional Int (8 bytes long) but sizeData it self was just 2 bytes long. I have no idea how is possible it sometimes worked but solution -- which seems to work properly -- is to use method withUnsafeBytes in fallowing way:
let size = sizeData.withUnsafeBytes { (pointer: UnsafePointer<UInt16>) in pointer.pointee }
Returned value is not optional and has the proper type UInt16 (2 bytes long).
If you check Documentation, there is a warning:
Warning The byte pointer argument should not be stored and used
outside of the lifetime of the call to the closure.
Seems like You should deal with the size inside the closure body
func testGuardLet() {
let data = Data(bytes: [7, 0, UInt8.min])
var sizeData = data.subdata(in: 0 ..< 2)
withUnsafeBytes(of: &sizeData) { bytes in
print(bytes.count)
for byte in bytes {
print(byte)
}
}
let bytes = withUnsafeBytes(of: &sizeData) { bytes in
return bytes // BUGS ☠️☠️☠️
}
}

Data, UnsafeMutablePointer and extended attributes in Swift 3 [duplicate]

I am looking for a solution to add extended file attributes for a file in swift. I checked this link Write extended file attributes, but the solutions are in objective c and I need a solution for swift.
Here is a possible implementation in Swift 5 as an extension for URL,
with methods to get, set, list, and remove extended attributes of
a file. (Swift 2, 3, and 4 code can be found in the edit history.)
extension URL {
/// Get extended attribute.
func extendedAttribute(forName name: String) throws -> Data {
let data = try self.withUnsafeFileSystemRepresentation { fileSystemPath -> Data in
// Determine attribute size:
let length = getxattr(fileSystemPath, name, nil, 0, 0, 0)
guard length >= 0 else { throw URL.posixError(errno) }
// Create buffer with required size:
var data = Data(count: length)
// Retrieve attribute:
let result = data.withUnsafeMutableBytes { [count = data.count] in
getxattr(fileSystemPath, name, $0.baseAddress, count, 0, 0)
}
guard result >= 0 else { throw URL.posixError(errno) }
return data
}
return data
}
/// Set extended attribute.
func setExtendedAttribute(data: Data, forName name: String) throws {
try self.withUnsafeFileSystemRepresentation { fileSystemPath in
let result = data.withUnsafeBytes {
setxattr(fileSystemPath, name, $0.baseAddress, data.count, 0, 0)
}
guard result >= 0 else { throw URL.posixError(errno) }
}
}
/// Remove extended attribute.
func removeExtendedAttribute(forName name: String) throws {
try self.withUnsafeFileSystemRepresentation { fileSystemPath in
let result = removexattr(fileSystemPath, name, 0)
guard result >= 0 else { throw URL.posixError(errno) }
}
}
/// Get list of all extended attributes.
func listExtendedAttributes() throws -> [String] {
let list = try self.withUnsafeFileSystemRepresentation { fileSystemPath -> [String] in
let length = listxattr(fileSystemPath, nil, 0, 0)
guard length >= 0 else { throw URL.posixError(errno) }
// Create buffer with required size:
var namebuf = Array<CChar>(repeating: 0, count: length)
// Retrieve attribute list:
let result = listxattr(fileSystemPath, &namebuf, namebuf.count, 0)
guard result >= 0 else { throw URL.posixError(errno) }
// Extract attribute names:
let list = namebuf.split(separator: 0).compactMap {
$0.withUnsafeBufferPointer {
$0.withMemoryRebound(to: UInt8.self) {
String(bytes: $0, encoding: .utf8)
}
}
}
return list
}
return list
}
/// Helper function to create an NSError from a Unix errno.
private static func posixError(_ err: Int32) -> NSError {
return NSError(domain: NSPOSIXErrorDomain, code: Int(err),
userInfo: [NSLocalizedDescriptionKey: String(cString: strerror(err))])
}
}
Example usage:
let fileURL = URL(fileURLWithPath: "/path/to/file")
let attr1 = "com.myCompany.myAttribute"
let attr2 = "com.myCompany.otherAttribute"
let data1 = Data([1, 2, 3, 4])
let data2 = Data([5, 6, 7, 8, 9])
do {
// Set attributes:
try fileURL.setExtendedAttribute(data: data1, forName: attr1)
try fileURL.setExtendedAttribute(data: data2, forName: attr2)
// List attributes:
let list = try fileURL.listExtendedAttributes()
print(list)
// ["com.myCompany.myAttribute", "com.myCompany.otherAttribute", "other"]
let data1a = try fileURL.extendedAttribute(forName: attr1)
print(data1a as NSData)
// <01020304>
// Remove attributes
for attr in list {
try fileURL.removeExtendedAttribute(forName: attr)
}
} catch let error {
print(error.localizedDescription)
}

SQLite db file is only read at the startup of the app

I have an issue with my code that I hope maybe som of you can help me out with.
I have a "kindoff" dictionary app where the user can search for abbreviations.
The datamodel is build using an SQLite database. In my first version the data.db file was only stored locally, but since I have to make a lot of data updates I don't wanna update en whole app every time. So I have made a version that gets the data.db file from a server instead.
My problem is that the user have to quit og restart the app to get the updated version. Somehow, even if the new file is copied to the directory the sqldb class does'nt read the new file. Any idea how to make som code the gets the dbclass to read the new file, while the app is running?
Here is the code the copies the new file to the directory
func executeDownloadTask(){
if Reachability.isConnectedToNetwork() == true{
print("just Checking")
let backgroundSessionConfiguration = NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier("backgroundSession")
backgroundSession = NSURLSession(configuration: backgroundSessionConfiguration, delegate: self,delegateQueue: NSOperationQueue.mainQueue())
let the_path:String = UpdateDbFile.findPathInDocDir("data.db");// get the path for the data.db file
UpdateDbFile.deleteFilewithPath(the_path) // delete the existing file
startDownload() // download the updated dbfile
}
}
Heres the SQLiteDb class that I use.
//
// SQLiteDB.swift
// TasksGalore
//
// Created by Fahim Farook on 12/6/14.
// Copyright (c) 2014 RookSoft Pte. Ltd. All rights reserved.
//
import Foundation
#if os(iOS)
import UIKit
#else
import AppKit
#endif
let SQLITE_DATE = SQLITE_NULL + 1
internal let SQLITE_STATIC = unsafeBitCast(0, sqlite3_destructor_type.self)
internal let SQLITE_TRANSIENT = unsafeBitCast(-1, sqlite3_destructor_type.self)
// MARK:- SQLColumn Class - Column Definition
class SQLColumn {
var value:AnyObject? = nil
var type:CInt = -1
init(value:AnyObject, type:CInt) {
// println("SQLiteDB - Initialize column with type: \(type), value: \(value)")
self.value = value
self.type = type
}
// New conversion functions
func asString()->String {
switch (type) {
case SQLITE_INTEGER, SQLITE_FLOAT:
return "\(value!)"
case SQLITE_TEXT:
return value as! String
case SQLITE_BLOB:
if let str = NSString(data:value as! NSData, encoding:NSUTF8StringEncoding) {
return str as String
} else {
return ""
}
case SQLITE_NULL:
return ""
case SQLITE_DATE:
let fmt = NSDateFormatter()
fmt.dateFormat = "yyyy-MM-dd HH:mm:ss"
return fmt.stringFromDate(value as! NSDate)
default:
return ""
}
}
func asInt()->Int {
switch (type) {
case SQLITE_INTEGER, SQLITE_FLOAT:
return value as! Int
case SQLITE_TEXT:
let str = value as! NSString
return str.integerValue
case SQLITE_BLOB:
if let str = NSString(data:value as! NSData, encoding:NSUTF8StringEncoding) {
return str.integerValue
} else {
return 0
}
case SQLITE_NULL:
return 0
case SQLITE_DATE:
return Int((value as! NSDate).timeIntervalSince1970)
default:
return 0
}
}
func asDouble()->Double {
switch (type) {
case SQLITE_INTEGER, SQLITE_FLOAT:
return value as! Double
case SQLITE_TEXT:
let str = value as! NSString
return str.doubleValue
case SQLITE_BLOB:
if let str = NSString(data:value as! NSData, encoding:NSUTF8StringEncoding) {
return str.doubleValue
} else {
return 0.0
}
case SQLITE_NULL:
return 0.0
case SQLITE_DATE:
return (value as! NSDate).timeIntervalSince1970
default:
return 0.0
}
}
func asData()->NSData? {
switch (type) {
case SQLITE_INTEGER, SQLITE_FLOAT:
let str = "\(value)" as NSString
return str.dataUsingEncoding(NSUTF8StringEncoding)
case SQLITE_TEXT:
let str = value as! NSString
return str.dataUsingEncoding(NSUTF8StringEncoding)
case SQLITE_BLOB:
return value as? NSData
case SQLITE_NULL:
return nil
case SQLITE_DATE:
let fmt = NSDateFormatter()
fmt.dateFormat = "yyyy-MM-dd HH:mm:ss"
let str = fmt.stringFromDate(value as! NSDate)
return str.dataUsingEncoding(NSUTF8StringEncoding)
default:
return nil
}
}
func asDate()->NSDate? {
switch (type) {
case SQLITE_INTEGER, SQLITE_FLOAT:
let tm = value as! Double
return NSDate(timeIntervalSince1970:tm)
case SQLITE_TEXT:
let fmt = NSDateFormatter()
fmt.dateFormat = "yyyy-MM-dd HH:mm:ss"
return fmt.dateFromString(value as! String)
case SQLITE_BLOB:
if let str = NSString(data:value as! NSData, encoding:NSUTF8StringEncoding) {
let fmt = NSDateFormatter()
fmt.dateFormat = "yyyy-MM-dd HH:mm:ss"
return fmt.dateFromString(str as String)
} else {
return nil
}
case SQLITE_NULL:
return nil
case SQLITE_DATE:
return value as? NSDate
default:
return nil
}
}
func description()->String {
return "Type: \(type), Value: \(value)"
}
}
// MARK:- SQLRow Class - Row Definition
class SQLRow {
var data = Dictionary<String, SQLColumn>()
subscript(key: String) -> SQLColumn? {
get {
return data[key]
}
set(newVal) {
data[key] = newVal
}
}
func description()->String {
return data.description
}
}
// MARK:- SQLiteDB Class - Does all the work
class SQLiteDB{
let DB_NAME = "data.db"
let QUEUE_LABLE = "SQLiteDB"
private var db:COpaquePointer = nil
private var queue:dispatch_queue_t
private var fmt = NSDateFormatter()
private var GROUP = ""
var newFileName = " "
var recentFileName = "Bøsse "
struct Static {
static var instance:SQLiteDB? = nil
static var token:dispatch_once_t = 0
}
class func sharedInstance() -> SQLiteDB! {
dispatch_once(&Static.token) {
Static.instance = self.init(gid:"")
}
return Static.instance!
}
class func sharedInstance(gid:String) -> SQLiteDB! {
dispatch_once(&Static.token) {
Static.instance = self.init(gid:gid)
}
return Static.instance!
}
required init(gid:String) {
assert(Static.instance == nil, "Singleton already initialized!")
GROUP = gid
// Set queue
queue = dispatch_queue_create(QUEUE_LABLE, nil)
// Set up for file operations
let fm = NSFileManager.defaultManager()
let dbName:String = String.fromCString(DB_NAME)!
var docDir = ""
// Is this for an app group?
if GROUP.isEmpty {
// Get path to DB in Documents directory
docDir = NSSearchPathForDirectoriesInDomains(.DocumentDirectory,.UserDomainMask, true)[0] as String
} else {
// Get path to shared group folder
if let url = fm.containerURLForSecurityApplicationGroupIdentifier(GROUP) {
docDir = url.path!
} else {
assert(false, "Error getting container URL for group: \(GROUP)")
}
}
let path = docDir.NS.stringByAppendingPathComponent(dbName)
print(path)
// Check if copy of DB is there in Documents directory
if !(fm.fileExistsAtPath(path)) {
// The database does not exist, so copy to Documents directory
if let from = NSBundle.mainBundle().resourcePath?.NS.stringByAppendingPathComponent(dbName) {
var error:NSError?
do {
try fm.copyItemAtPath(from, toPath: path)
print("restart the app to get updated data")
} catch let error1 as NSError {
error = error1
print("SQLiteDB - failed to copy writable version of DB!")
print("Error - \(error!.localizedDescription)")
return
}
}
}
// Open the DB
let cpath = path.cStringUsingEncoding(NSUTF8StringEncoding)
let error = sqlite3_open(cpath!, &db)
if error != SQLITE_OK {
// Open failed, close DB and fail
print("SQLiteDB - failed to open DB!")
sqlite3_close(db)
}
fmt.dateFormat = "YYYY-MM-dd HH:mm:ss"
}
deinit {
closeDatabase()
}
private func closeDatabase() {
if db != nil {
// Get launch count value
let ud = NSUserDefaults.standardUserDefaults()
var launchCount = ud.integerForKey("LaunchCount")
launchCount--
print("SQLiteDB - Launch count \(launchCount)")
var clean = false
if launchCount < 0 {
clean = true
launchCount = 500
}
ud.setInteger(launchCount, forKey: "LaunchCount")
ud.synchronize()
// Do we clean DB?
if !clean {
sqlite3_close(db)
return
}
// Clean DB
print("SQLiteDB - Optimize DB")
let sql = "VACUUM; ANALYZE"
if execute(sql) != SQLITE_OK {
print("SQLiteDB - Error cleaning DB")
}
sqlite3_close(db)
}
}
// Execute SQL with parameters and return result code
func execute(sql:String, parameters:[AnyObject]?=nil)->CInt {
var result:CInt = 0
dispatch_sync(queue) {
let stmt = self.prepare(sql, params:parameters)
if stmt != nil {
result = self.execute(stmt, sql:sql)
}
}
return result
}
// Run SQL query with parameters
func query(sql:String, parameters:[AnyObject]?=nil)->[SQLRow] {
var rows = [SQLRow]()
dispatch_sync(queue) {
let stmt = self.prepare(sql, params:parameters)
if stmt != nil {
rows = self.query(stmt, sql:sql)
}
}
return rows
}
// Show alert with either supplied message or last error
func alert(msg:String) {
dispatch_async(dispatch_get_main_queue()) {
#if os(iOS)
let alert = UIAlertView(title: "SQLiteDB", message:msg, delegate: nil, cancelButtonTitle: "OK")
alert.show()
#else
let alert = NSAlert()
alert.addButtonWithTitle("OK")
alert.messageText = "SQLiteDB"
alert.informativeText = msg
alert.alertStyle = NSAlertStyle.WarningAlertStyle
alert.runModal()
#endif
}
}
// Private method which prepares the SQL
private func prepare(sql:String, params:[AnyObject]?)->COpaquePointer {
var stmt:COpaquePointer = nil
let cSql = sql.cStringUsingEncoding(NSUTF8StringEncoding)
// Prepare
let result = sqlite3_prepare_v2(self.db, cSql!, -1, &stmt, nil)
if result != SQLITE_OK {
sqlite3_finalize(stmt)
if let error = String.fromCString(sqlite3_errmsg(self.db)) {
let msg = "SQLiteDB - failed to prepare SQL: \(sql), Error: \(error)"
print(msg)
}
return nil
}
// Bind parameters, if any
if params != nil {
// Validate parameters
let cntParams = sqlite3_bind_parameter_count(stmt)
let cnt = CInt(params!.count)
if cntParams != cnt {
let msg = "SQLiteDB - failed to bind parameters, counts did not match. SQL: \(sql), Parameters: \(params)"
print(msg)
return nil
}
var flag:CInt = 0
// Text & BLOB values passed to a C-API do not work correctly if they are not marked as transient.
for ndx in 1...cnt {
// println("Binding: \(params![ndx-1]) at Index: \(ndx)")
// Check for data types
if let txt = params![ndx-1] as? String {
flag = sqlite3_bind_text(stmt, CInt(ndx), txt, -1, SQLITE_TRANSIENT)
} else if let data = params![ndx-1] as? NSData {
flag = sqlite3_bind_blob(stmt, CInt(ndx), data.bytes, CInt(data.length), SQLITE_TRANSIENT)
} else if let date = params![ndx-1] as? NSDate {
let txt = fmt.stringFromDate(date)
flag = sqlite3_bind_text(stmt, CInt(ndx), txt, -1, SQLITE_TRANSIENT)
} else if let val = params![ndx-1] as? Double {
flag = sqlite3_bind_double(stmt, CInt(ndx), CDouble(val))
} else if let val = params![ndx-1] as? Int {
flag = sqlite3_bind_int(stmt, CInt(ndx), CInt(val))
} else {
flag = sqlite3_bind_null(stmt, CInt(ndx))
}
// Check for errors
if flag != SQLITE_OK {
sqlite3_finalize(stmt)
if let error = String.fromCString(sqlite3_errmsg(self.db)) {
let msg = "SQLiteDB - failed to bind for SQL: \(sql), Parameters: \(params), Index: \(ndx) Error: \(error)"
print(msg)
}
return nil
}
}
}
return stmt
}
// Private method which handles the actual execution of an SQL statement
private func execute(stmt:COpaquePointer, sql:String)->CInt {
// Step
var result = sqlite3_step(stmt)
if result != SQLITE_OK && result != SQLITE_DONE {
sqlite3_finalize(stmt)
if let err = String.fromCString(sqlite3_errmsg(self.db)) {
let msg = "SQLiteDB - failed to execute SQL: \(sql), Error: \(err)"
print(msg)
}
return 0
}
// Is this an insert
let upp = sql.uppercaseString
if upp.hasPrefix("INSERT ") {
// Known limitations: http://www.sqlite.org/c3ref/last_insert_rowid.html
let rid = sqlite3_last_insert_rowid(self.db)
result = CInt(rid)
} else if upp.hasPrefix("DELETE") || upp.hasPrefix("UPDATE") {
var cnt = sqlite3_changes(self.db)
if cnt == 0 {
cnt++
}
result = CInt(cnt)
} else {
result = 1
}
// Finalize
sqlite3_finalize(stmt)
return result
}
// Private method which handles the actual execution of an SQL query
private func query(stmt:COpaquePointer, sql:String)->[SQLRow] {
var rows = [SQLRow]()
var fetchColumnInfo = true
var columnCount:CInt = 0
var columnNames = [String]()
var columnTypes = [CInt]()
var result = sqlite3_step(stmt)
while result == SQLITE_ROW {
// Should we get column info?
if fetchColumnInfo {
columnCount = sqlite3_column_count(stmt)
for index in 0..<columnCount {
// Get column name
let name = sqlite3_column_name(stmt, index)
columnNames.append(String.fromCString(name)!)
// Get column type
columnTypes.append(self.getColumnType(index, stmt:stmt))
}
fetchColumnInfo = false
}
// Get row data for each column
let row = SQLRow()
for index in 0..<columnCount {
let key = columnNames[Int(index)]
let type = columnTypes[Int(index)]
if let val:AnyObject = self.getColumnValue(index, type:type, stmt:stmt) {
// println("Column type:\(type) with value:\(val)")
let col = SQLColumn(value: val, type: type)
row[key] = col
}
}
rows.append(row)
// Next row
result = sqlite3_step(stmt)
}
sqlite3_finalize(stmt)
return rows
}
// Get column type
private func getColumnType(index:CInt, stmt:COpaquePointer)->CInt {
var type:CInt = 0
// Column types - http://www.sqlite.org/datatype3.html (section 2.2 table column 1)
let blobTypes = ["BINARY", "BLOB", "VARBINARY"]
let charTypes = ["CHAR", "CHARACTER", "CLOB", "NATIONAL VARYING CHARACTER", "NATIVE CHARACTER", "NCHAR", "NVARCHAR", "TEXT", "VARCHAR", "VARIANT", "VARYING CHARACTER"]
let dateTypes = ["DATE", "DATETIME", "TIME", "TIMESTAMP"]
let intTypes = ["BIGINT", "BIT", "BOOL", "BOOLEAN", "INT", "INT2", "INT8", "INTEGER", "MEDIUMINT", "SMALLINT", "TINYINT"]
let nullTypes = ["NULL"]
let realTypes = ["DECIMAL", "DOUBLE", "DOUBLE PRECISION", "FLOAT", "NUMERIC", "REAL"]
// Determine type of column - http://www.sqlite.org/c3ref/c_blob.html
let buf = sqlite3_column_decltype(stmt, index)
// println("SQLiteDB - Got column type: \(buf)")
if buf != nil {
var tmp = String.fromCString(buf)!.uppercaseString
// Remove brackets
let pos = tmp.positionOf("(")
if pos > 0 {
tmp = tmp.subStringTo(pos)
}
// Remove unsigned?
// Remove spaces
// Is the data type in any of the pre-set values?
// println("SQLiteDB - Cleaned up column type: \(tmp)")
if intTypes.contains(tmp) {
return SQLITE_INTEGER
}
if realTypes.contains(tmp) {
return SQLITE_FLOAT
}
if charTypes.contains(tmp) {
return SQLITE_TEXT
}
if blobTypes.contains(tmp) {
return SQLITE_BLOB
}
if nullTypes.contains(tmp) {
return SQLITE_NULL
}
if dateTypes.contains(tmp) {
return SQLITE_DATE
}
return SQLITE_TEXT
} else {
// For expressions and sub-queries
type = sqlite3_column_type(stmt, index)
}
return type
}
// Get column value
private func getColumnValue(index:CInt, type:CInt, stmt:COpaquePointer)->AnyObject? {
// Integer
if type == SQLITE_INTEGER {
let val = sqlite3_column_int(stmt, index)
return Int(val)
}
// Float
if type == SQLITE_FLOAT {
let val = sqlite3_column_double(stmt, index)
return Double(val)
}
// Text - handled by default handler at end
// Blob
if type == SQLITE_BLOB {
let data = sqlite3_column_blob(stmt, index)
let size = sqlite3_column_bytes(stmt, index)
let val = NSData(bytes:data, length: Int(size))
return val
}
// Null
if type == SQLITE_NULL {
return nil
}
// Date
if type == SQLITE_DATE {
// Is this a text date
let txt = UnsafePointer<Int8>(sqlite3_column_text(stmt, index))
if txt != nil {
if let buf = NSString(CString:txt, encoding:NSUTF8StringEncoding) {
let set = NSCharacterSet(charactersInString: "-:")
let range = buf.rangeOfCharacterFromSet(set)
if range.location != NSNotFound {
// Convert to time
var time:tm = tm(tm_sec: 0, tm_min: 0, tm_hour: 0, tm_mday: 0, tm_mon: 0, tm_year: 0, tm_wday: 0, tm_yday: 0, tm_isdst: 0, tm_gmtoff: 0, tm_zone:nil)
strptime(txt, "%Y-%m-%d %H:%M:%S", &time)
time.tm_isdst = -1
let diff = NSTimeZone.localTimeZone().secondsFromGMT
let t = mktime(&time) + diff
let ti = NSTimeInterval(t)
let val = NSDate(timeIntervalSince1970:ti)
return val
}
}
}
// If not a text date, then it's a time interval
let val = sqlite3_column_double(stmt, index)
let dt = NSDate(timeIntervalSince1970: val)
return dt
}
// If nothing works, return a string representation
let buf = UnsafePointer<Int8>(sqlite3_column_text(stmt, index))
let val = String.fromCString(buf)
// println("SQLiteDB - Got value: \(val)")
return val
}
}
public extension String {
var NS: NSString { return (self as NSString) }
}
Hope you can give me some advice. Thanks

Epub Font Mangling is not working

I am creating an EPUB 3 reader for iOS using Swift 2.
The problem I'm currently facing is with font obfuscation / font mangling. I've read a tutorial that goes over how to do that in Swift, and integrated it into my project with some adaptations.
When I load an obfuscated epub into my app, the fonts are not loaded correctly and fall back to other system fonts. When I load an epub with the same fonts but not obfuscated, everything looks fine. Obviously, that means there's something wrong with my obfuscation code, but I can't for the life of me find the error.
Here's my code:
public struct Crypto {
public func obfuscateFontIDPF(data:NSData, key:String) -> NSData {
let source = data
var destination = [UInt8]()
let shaKey = key.sha1()
let keyData = shaKey.utf8Array
var arr = [UInt8](count: source.length, repeatedValue: 0)
source.getBytes(&arr, length:source.length)
var outer = 0
while outer < 52 && arr.isEmpty == false {
var inner = 0
while inner < 20 && arr.isEmpty == false {
let byte = arr.removeAtIndex(0) //Assumes read advances file position
let sourceByte = byte
let keyByte = keyData[inner]
let obfuscatedByte = sourceByte ^ keyByte
destination.append(obfuscatedByte)
inner++
}
outer++
}
if arr.isEmpty == false {
while arr.isEmpty == false {
let byte = arr.removeAtIndex(0)
destination.append(byte)
}
}
let newData = NSData(bytes: &destination, length: destination.count*sizeof(UInt8))
return newData
}
}
extension String {
func sha1() -> String {
var selfAsSha1 = ""
if let data = self.dataUsingEncoding(NSUTF8StringEncoding)
{
var digest = [UInt8](count: Int(CC_SHA1_DIGEST_LENGTH), repeatedValue: 0)
CC_SHA1(data.bytes, CC_LONG(data.length), &digest)
for index in 0..<CC_SHA1_DIGEST_LENGTH
{
selfAsSha1 += String(format: "%02x", digest[Int(index)])
}
}
return selfAsSha1
}
var utf8Array: [UInt8] {
return Array(utf8)
}
}
And here I call the obfuscation method:
func parserDidEndDocument(parser: NSXMLParser) {
if encryptedFilePaths!.count != 0 {
for file in encryptedFilePaths! {
let epubMainDirectoryPath = NSString(string: epubBook!.epubMainFolderPath!).stringByDeletingLastPathComponent
let fullFilePath = epubMainDirectoryPath.stringByAppendingString("/" + file)
let url = NSURL(fileURLWithPath: fullFilePath)
if let source = NSData(contentsOfURL: url) {
let decryptedFont = Crypto().obfuscateFontIDPF(source, key: self.epubBook!.encryptionKey!)
do {
try decryptedFont.writeToFile(fullFilePath, options: .DataWritingAtomic)
} catch {
print(error)
}
}
}
}
}
If you see where the error might be, please let me know.
I figured it out, here is the working code:
private func obfuscateData(data: NSData, key: String) -> NSData {
var destinationBytes = [UInt8]()
// Key needs to be SHA1 hash with length of exactly 20 chars
let hashedKeyBytes = generateHashedBytesFromString(key)
var sourceBytes = [UInt8](count: data.length, repeatedValue: 0)
data.getBytes(&sourceBytes, length: data.length)
var outerCount = 0
while outerCount < 52 && sourceBytes.isEmpty == false {
var innerCount = 0
while innerCount < 20 && sourceBytes.isEmpty == false {
let sourceByte = sourceBytes.removeAtIndex(0)
let keyByte = hashedKeyBytes[innerCount]
let obfuscatedByte = (sourceByte ^ keyByte)
destinationBytes.append(obfuscatedByte)
innerCount += 1
}
outerCount += 1
}
destinationBytes.appendContentsOf(sourceBytes)
let destinationData = NSData(bytes: &destinationBytes, length: destinationBytes.count*sizeof(UInt8))
sourceBytes.removeAll(keepCapacity: false)
destinationBytes.removeAll(keepCapacity: false)
return destinationData
}
/// Convert the key string to a SHA1 hashed Byte Array
private func generateHashedBytesFromString(string: String) -> [UInt8] {
var resultBytes = [UInt8]()
var hashedString = string.sha1()
for _ in 0.stride(to: hashedString.characters.count, by: 2) {
let character = "0x\(hashedString.returnTwoCharacters())"
resultBytes.append(UInt8(strtod(character, nil)))
}
return resultBytes
}
extension String {
func sha1() -> String {
var selfAsSha1 = ""
if let data = self.dataUsingEncoding(NSUTF8StringEncoding) {
var digest = [UInt8](count: Int(CC_SHA1_DIGEST_LENGTH), repeatedValue: 0)
CC_SHA1(data.bytes, CC_LONG(data.length), &digest)
for index in 0..<CC_SHA1_DIGEST_LENGTH {
selfAsSha1 += String(format: "%02x", digest[Int(index)])
}
}
return selfAsSha1
}
mutating func returnTwoCharacters() -> String {
var characters: String = ""
characters.append(self.removeAtIndex(startIndex))
characters.append(self.removeAtIndex(startIndex))
return characters
}
}

Converting Hex String to NSData in Swift

I got the code to convert String to HEX-String in Objective-C:
- (NSString *) CreateDataWithHexString:(NSString*)inputString {
NSUInteger inLength = [inputString length];
unichar *inCharacters = alloca(sizeof(unichar) * inLength);
[inputString getCharacters:inCharacters range:NSMakeRange(0, inLength)];
UInt8 *outBytes = malloc(sizeof(UInt8) * ((inLength / 2) + 1));
NSInteger i, o = 0;
UInt8 outByte = 0;
for (i = 0; i < inLength; i++) {
UInt8 c = inCharacters[i];
SInt8 value = -1;
if (c >= '0' && c <= '9') value = (c - '0');
else if (c >= 'A' && c <= 'F') value = 10 + (c - 'A');
else if (c >= 'a' && c <= 'f') value = 10 + (c - 'a');
if (value >= 0) {
if (i % 2 == 1) {
outBytes[o++] = (outByte << 4) | value;
outByte = 0;
} else {
outByte = value;
}
} else {
if (o != 0) break;
}
}
NSData *a = [[NSData alloc] initWithBytesNoCopy:outBytes length:o freeWhenDone:YES];
NSString* newStr = [NSString stringWithUTF8String:[a bytes]];
return newStr;
}
I want the same in Swift. Can anybody translate this code in Swift, or is there any easy way to do this in Swift?
This is my hex string to Data routine:
extension String {
/// Create `Data` from hexadecimal string representation
///
/// This creates a `Data` object from hex string. Note, if the string has any spaces or non-hex characters (e.g. starts with '<' and with a '>'), those are ignored and only hex characters are processed.
///
/// - returns: Data represented by this hexadecimal string.
var hexadecimal: Data? {
var data = Data(capacity: count / 2)
let regex = try! NSRegularExpression(pattern: "[0-9a-f]{1,2}", options: .caseInsensitive)
regex.enumerateMatches(in: self, range: NSRange(startIndex..., in: self)) { match, _, _ in
let byteString = (self as NSString).substring(with: match!.range)
let num = UInt8(byteString, radix: 16)!
data.append(num)
}
guard data.count > 0 else { return nil }
return data
}
}
And for the sake of completeness, this is my Data to hex string routine:
extension Data {
/// Hexadecimal string representation of `Data` object.
var hexadecimal: String {
return map { String(format: "%02x", $0) }
.joined()
}
}
Note, as shown in the above, I generally only convert between hexadecimal representations and NSData instances (because if the information could have been represented as a string you probably wouldn't have created a hexadecimal representation in the first place). But your original question wanted to convert between hexadecimal representations and String objects, and that might look like so:
extension String {
/// Create `String` representation of `Data` created from hexadecimal string representation
///
/// This takes a hexadecimal representation and creates a String object from that. Note, if the string has any spaces, those are removed. Also if the string started with a `<` or ended with a `>`, those are removed, too.
///
/// For example,
///
/// String(hexadecimal: "<666f6f>")
///
/// is
///
/// Optional("foo")
///
/// - returns: `String` represented by this hexadecimal string.
init?(hexadecimal string: String, encoding: String.Encoding = .utf8) {
guard let data = string.hexadecimal() else {
return nil
}
self.init(data: data, encoding: encoding)
}
/// Create hexadecimal string representation of `String` object.
///
/// For example,
///
/// "foo".hexadecimalString()
///
/// is
///
/// Optional("666f6f")
///
/// - parameter encoding: The `String.Encoding` that indicates how the string should be converted to `Data` before performing the hexadecimal conversion.
///
/// - returns: `String` representation of this String object.
func hexadecimalString(encoding: String.Encoding = .utf8) -> String? {
return data(using: encoding)?
.hexadecimal
}
}
You could then use the above like so:
let hexString = "68656c6c 6f2c2077 6f726c64"
print(String(hexadecimal: hexString))
Or,
let originalString = "hello, world"
print(originalString.hexadecimalString())
For permutations of the above for earlier Swift versions, see the revision history of this question.
convert hex string to data and string:
Swift1
func dataWithHexString(hex: String) -> NSData {
var hex = hex
let data = NSMutableData()
while(countElements(hex) > 0) {
var c: String = hex.substringToIndex(advance(hex.startIndex, 2))
hex = hex.substringFromIndex(advance(hex.startIndex, 2))
var ch: UInt32 = 0
NSScanner(string: c).scanHexInt(&ch)
data.appendBytes(&ch, length: 1)
}
return data
}
use:
let data = dataWithHexString("68656c6c6f2c20776f726c64") // <68656c6c 6f2c2077 6f726c64>
if let string = NSString(data: data, encoding: 1) {
print(string) // hello, world
}
Swift2
func dataWithHexString(hex: String) -> NSData {
var hex = hex
let data = NSMutableData()
while(hex.characters.count > 0) {
let c: String = hex.substringToIndex(hex.startIndex.advancedBy(2))
hex = hex.substringFromIndex(hex.startIndex.advancedBy(2))
var ch: UInt32 = 0
NSScanner(string: c).scanHexInt(&ch)
data.appendBytes(&ch, length: 1)
}
return data
}
use:
let data = dataWithHexString("68656c6c6f2c20776f726c64") // <68656c6c 6f2c2077 6f726c64>
if let string = String(data: data, encoding: NSUTF8StringEncoding) {
print(string) //"hello, world"
}
Swift3
func dataWithHexString(hex: String) -> Data {
var hex = hex
var data = Data()
while(hex.characters.count > 0) {
let c: String = hex.substring(to: hex.index(hex.startIndex, offsetBy: 2))
hex = hex.substring(from: hex.index(hex.startIndex, offsetBy: 2))
var ch: UInt32 = 0
Scanner(string: c).scanHexInt32(&ch)
var char = UInt8(ch)
data.append(&char, count: 1)
}
return data
}
use:
let data = dataWithHexString(hex: "68656c6c6f2c20776f726c64") // <68656c6c 6f2c2077 6f726c64>
let string = String(data: data, encoding: .utf8) // "hello, world"
Swift4
func dataWithHexString(hex: String) -> Data {
var hex = hex
var data = Data()
while(hex.count > 0) {
let subIndex = hex.index(hex.startIndex, offsetBy: 2)
let c = String(hex[..<subIndex])
hex = String(hex[subIndex...])
var ch: UInt32 = 0
Scanner(string: c).scanHexInt32(&ch)
var char = UInt8(ch)
data.append(&char, count: 1)
}
return data
}
use:
let data = dataWithHexString(hex: "68656c6c6f2c20776f726c64") // <68656c6c 6f2c2077 6f726c64>
let string = String(data: data, encoding: .utf8) // "hello, world"
Swift 4 & Swift 5 implementation:
init?(hexString: String) {
let len = hexString.count / 2
var data = Data(capacity: len)
var i = hexString.startIndex
for _ in 0..<len {
let j = hexString.index(i, offsetBy: 2)
let bytes = hexString[i..<j]
if var num = UInt8(bytes, radix: 16) {
data.append(&num, count: 1)
} else {
return nil
}
i = j
}
self = data
}
Usage:
let data = Data(hexString: "0a1b3c4d")
Swift 5
extension Data {
init?(hex: String) {
guard hex.count.isMultiple(of: 2) else {
return nil
}
let chars = hex.map { $0 }
let bytes = stride(from: 0, to: chars.count, by: 2)
.map { String(chars[$0]) + String(chars[$0 + 1]) }
.compactMap { UInt8($0, radix: 16) }
guard hex.count / bytes.count == 2 else { return nil }
self.init(bytes)
}
}
Here is my Swift 5 way to do it:
does take care of "0x" prefixes
use subscript instead of allocated Array(), no C style [i+1] too
add .hexadecimal to String.data(using encoding:) -> Data?
.
String Extension:
extension String {
enum ExtendedEncoding {
case hexadecimal
}
func data(using encoding:ExtendedEncoding) -> Data? {
let hexStr = self.dropFirst(self.hasPrefix("0x") ? 2 : 0)
guard hexStr.count % 2 == 0 else { return nil }
var newData = Data(capacity: hexStr.count/2)
var indexIsEven = true
for i in hexStr.indices {
if indexIsEven {
let byteRange = i...hexStr.index(after: i)
guard let byte = UInt8(hexStr[byteRange], radix: 16) else { return nil }
newData.append(byte)
}
indexIsEven.toggle()
}
return newData
}
}
Usage:
"5413".data(using: .hexadecimal)
"0x1234FF".data(using: .hexadecimal)
Tests:
extension Data {
var bytes:[UInt8] { // fancy pretty call: myData.bytes -> [UInt8]
return [UInt8](self)
}
// Could make a more optimized one~
func hexa(prefixed isPrefixed:Bool = true) -> String {
return self.bytes.reduce(isPrefixed ? "0x" : "") { $0 + String(format: "%02X", $1) }
}
}
print("000204ff5400".data(using: .hexadecimal)?.hexa() ?? "failed") // OK
print("0x000204ff5400".data(using: .hexadecimal)?.hexa() ?? "failed") // OK
print("541".data(using: .hexadecimal)?.hexa() ?? "failed") // fails
print("5413".data(using: .hexadecimal)?.hexa() ?? "failed") // OK
Here's a simple solution I settled on:
extension NSData {
public convenience init(hexString: String) {
var index = hexString.startIndex
var bytes: [UInt8] = []
repeat {
bytes.append(hexString[index...index.advancedBy(1)].withCString {
return UInt8(strtoul($0, nil, 16))
})
index = index.advancedBy(2)
} while index.distanceTo(hexString.endIndex) != 0
self.init(bytes: &bytes, length: bytes.count)
}
}
Usage:
let data = NSData(hexString: "b8dfb080bc33fb564249e34252bf143d88fc018f")
Output:
print(data)
>>> <b8dfb080 bc33fb56 4249e342 52bf143d 88fc018f>
Update 6/29/2016
I updated the initializer to handle malformed data (i.e., invalid characters or odd number of characters).
public convenience init?(hexString: String, force: Bool) {
let characterSet = NSCharacterSet(charactersInString: "0123456789abcdefABCDEF")
for scalar in hexString.unicodeScalars {
if characterSet.characterIsMember(UInt16(scalar.value)) {
hexString.append(scalar)
}
else if !force {
return nil
}
}
if hexString.characters.count % 2 == 1 {
if force {
hexString = "0" + hexString
}
else {
return nil
}
}
var index = hexString.startIndex
var bytes: [UInt8] = []
repeat {
bytes.append(hexString[index...index.advancedBy(1)].withCString {
return UInt8(strtoul($0, nil, 16))
})
index = index.advancedBy(2)
} while index.distanceTo(hexString.endIndex) != 0
self.init(bytes: &bytes, length: bytes.count)
}
Here is my take on converting hexadecimal string to Data using Swift 4:
extension Data {
private static let hexRegex = try! NSRegularExpression(pattern: "^([a-fA-F0-9][a-fA-F0-9])*$", options: [])
init?(hexString: String) {
if Data.hexRegex.matches(in: hexString, range: NSMakeRange(0, hexString.count)).isEmpty {
return nil // does not look like a hexadecimal string
}
let chars = Array(hexString)
let bytes: [UInt8] =
stride(from: 0, to: chars.count, by: 2)
.map {UInt8(String([chars[$0], chars[$0+1]]), radix: 16)}
.compactMap{$0}
self = Data(bytes)
}
var hexString: String {
return map { String(format: "%02hhx", $0) }.joined()
}
}
(I threw in a small feature for converting back to hex string I found in this answer)
And here is how you would use it:
let data = Data(hexString: "cafecafe")
print(data?.hexString) // will print Optional("cafecafe")
One more solution that is simple to follow and leverages swifts built-in hex parsing
func convertHexToBytes(_ str: String) -> Data? {
let values = str.compactMap { $0.hexDigitValue } // map char to value of 0-15 or nil
if values.count == str.count && values.count % 2 == 0 {
var data = Data()
for x in stride(from: 0, to: values.count, by: 2) {
let byte = (values[x] << 4) + values[x+1] // concat high and low bits
data.append(UInt8(byte))
}
return data
}
return nil
}
let good = "e01AFd"
let bad = "e0671"
let ugly = "GT40"
print("\(convertHexToBytes(good))") // Optional(3 bytes)
print("\(convertHexToBytes(bad))") // nil
print("\(convertHexToBytes(ugly))") // nil
The code worked for me in Swift 3.0.2.
extension String {
/// Expanded encoding
///
/// - bytesHexLiteral: Hex string of bytes
/// - base64: Base64 string
enum ExpandedEncoding {
/// Hex string of bytes
case bytesHexLiteral
/// Base64 string
case base64
}
/// Convert to `Data` with expanded encoding
///
/// - Parameter encoding: Expanded encoding
/// - Returns: data
func data(using encoding: ExpandedEncoding) -> Data? {
switch encoding {
case .bytesHexLiteral:
guard self.characters.count % 2 == 0 else { return nil }
var data = Data()
var byteLiteral = ""
for (index, character) in self.characters.enumerated() {
if index % 2 == 0 {
byteLiteral = String(character)
} else {
byteLiteral.append(character)
guard let byte = UInt8(byteLiteral, radix: 16) else { return nil }
data.append(byte)
}
}
return data
case .base64:
return Data(base64Encoded: self)
}
}
}
Swift 5
With support iOS 13 and iOS2...iOS12.
extension String {
var hex: Data? {
var value = self
var data = Data()
while value.count > 0 {
let subIndex = value.index(value.startIndex, offsetBy: 2)
let c = String(value[..<subIndex])
value = String(value[subIndex...])
var char: UInt8
if #available(iOS 13.0, *) {
guard let int = Scanner(string: c).scanInt32(representation: .hexadecimal) else { return nil }
char = UInt8(int)
} else {
var int: UInt32 = 0
Scanner(string: c).scanHexInt32(&int)
char = UInt8(int)
}
data.append(&char, count: 1)
}
return data
}
}
Swift 5
There is a compact implementation of initialize Data instance from hex string using a regular expression. It searches hex numbers inside a string and combine them to a result data so that it can support different formats of hex representations:
extension Data {
private static let regex = try! NSRegularExpression(pattern: "([0-9a-fA-F]{2})", options: [])
/// Create instance from string with hex numbers.
init(from: String) {
let range = NSRange(location: 0, length: from.utf16.count)
let bytes = Self.regex.matches(in: from, options: [], range: range)
.compactMap { Range($0.range(at: 1), in: from) }
.compactMap { UInt8(from[$0], radix: 16) }
self.init(bytes)
}
/// Hex string representation of data.
var hex: String {
map { String($0, radix: 16) }.joined()
}
}
Examples:
let data = Data(from: "0x11223344aabbccdd")
print(data.hex) // Prints "11223344aabbccdd"
let data2 = Data(from: "11223344aabbccdd")
print(data2.hex) // Prints "11223344aabbccdd"
let data3 = Data(from: "11223344 aabbccdd")
print(data3.hex) // Prints "11223344aabbccdd"
let data4 = Data(from: "11223344 AABBCCDD")
print(data4.hex) // Prints "11223344aabbccdd"
let data5 = Data(from: "Hex: 0x11223344AABBCCDD")
print(data5.hex) // Prints "11223344aabbccdd"
let data6 = Data(from: "word[0]=11223344 word[1]=AABBCCDD")
print(data6.hex) // Prints "11223344aabbccdd"
let data7 = Data(from: "No hex")
print(data7.hex) // Prints ""
Handles prefixes
Ignores invalid characters and incomplete bytes
Uses Swift built in hex character parsing
Doesn't use subscripts
extension Data {
init(hexString: String) {
self = hexString
.dropFirst(hexString.hasPrefix("0x") ? 2 : 0)
.compactMap { $0.hexDigitValue.map { UInt8($0) } }
.reduce(into: (data: Data(capacity: hexString.count / 2), byte: nil as UInt8?)) { partialResult, nibble in
if let p = partialResult.byte {
partialResult.data.append(p + nibble)
partialResult.byte = nil
} else {
partialResult.byte = nibble << 4
}
}.data
}
}
Supposing your string is even size, you can use this to convert to hexadecimal and save it to Data:
Swift 5.2
func hex(from string: String) -> Data {
.init(stride(from: 0, to: string.count, by: 2).map {
string[string.index(string.startIndex, offsetBy: $0) ... string.index(string.startIndex, offsetBy: $0 + 1)]
}.map {
UInt8($0, radix: 16)!
})
}

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