Using MD5 hash value on an ansi string in Swift 3 - swift

Question

I have a small function that takes a string and returns its MD5 hash value. The problem is, that it expects a UTF8 string, and I need it to calculate a hash value of a byte array encoded with iso-8859-1 (~ansi).
How can I change the following code to accept a byte array of characters, then return its hashed value?
static func md5(_ string: String) -> String {
let context = UnsafeMutablePointer<CC_MD5_CTX>.allocate(capacity: 1)
var digest = Array<UInt8>(repeating:0, count:Int(CC_MD5_DIGEST_LENGTH))
CC_MD5_Init(context)
CC_MD5_Update(context, string, CC_LONG(string.lengthOfBytes(using: String.Encoding.utf8)))
CC_MD5_Final(&digest, context)
context.deallocate(capacity: 1)
var hexString = ""
for byte in digest {
hexString += String(format:"%02x", byte)
}
return hexString
}
The tricky part is the CC_MD5_Update call. Thanks.

Answer 1

You can easily modify your function to take an arbitrary byte
array as argument. CC_MD5_Update is mapped to Swift as
func CC_MD5_Update(_ c: UnsafeMutablePointer<CC_MD5_CTX>!, _ data: UnsafeRawPointer!, _ len: CC_LONG) -> Int32
and you can pass an array as the UnsafeRawPointer parameter:
func md5(bytes: [UInt8]) -> String {
var context = CC_MD5_CTX()
var digest = Array<UInt8>(repeating:0, count:Int(CC_MD5_DIGEST_LENGTH))
CC_MD5_Init(&context)
CC_MD5_Update(&context, bytes, CC_LONG(bytes.count))
CC_MD5_Final(&digest, &context)
return digest.map { String(format: "%02hhx", $0) }.joined()
}
(I have also simplified it a bit.)
Alternatively, pass a Data argument:
func md5(data: Data) -> String {
var context = CC_MD5_CTX()
var digest = Array<UInt8>(repeating:0, count:Int(CC_MD5_DIGEST_LENGTH))
CC_MD5_Init(&context)
data.withUnsafeBytes {
_ = CC_MD5_Update(&context, $0, CC_LONG(data.count))
}
CC_MD5_Final(&digest, &context)
return digest.map { String(format: "%02hhx", $0) }.joined()
}
which can then be used as
let s = "foo"
if let data = s.data(using: .isoLatin1) {
let hash = md5(data: data)
print(hash)
}
Update for Swift 5:
import CommonCrypto
func md5(data: Data) -> String {
var context = CC_MD5_CTX()
var digest = Array<UInt8>(repeating:0, count:Int(CC_MD5_DIGEST_LENGTH))
CC_MD5_Init(&context)
data.withUnsafeBytes {
_ = CC_MD5_Update(&context, $0.baseAddress, CC_LONG(data.count))
}
CC_MD5_Final(&digest, &context)
return digest.map { String(format: "%02hhx", $0) }.joined()
}

Answer 2

If you are sure your 'string' contains only utf8 characters, call CC_MD5_Update with string.utf8 so:
CC_MD5_Update(context, string.utf8, CC_LONG(string.lengthOfBytes(using: String.Encoding.utf8)))
Strings in swift are 'interesting', this is a good read on the topic: https://oleb.net/blog/2016/08/swift-3-strings/

Answer 3

// requires a bridging header with this:
// #import <CommonCrypto/CommonCrypto.h>
func MD5(_ string: String) -> String? {
let length = Int(CC_MD5_DIGEST_LENGTH)
var digest = [UInt8](repeating: 0, count: length)
if let d = string.data(using: String.Encoding.utf8) {
d.withUnsafeBytes { (body: UnsafePointer<UInt8>) in
CC_MD5(body, CC_LONG(d.count), &digest)
}
}
return (0..<length).reduce("") {
$0 + String(format: "%02x", digest[$1])
}
}
Justin Answer : https://gist.github.com/jstn/787da74ab4be9d4cf3cb