function to generate Sha-256 in Kotlin

Sha256.kt

Class Hasher {
  fun hash(): String {
    val bytes = this.toString().toByteArray()
    val md = MessageDigest.getInstance("SHA-256")
    val digest = md.digest(bytes)
    return digest.fold("", { str, it -> str + "%02x".format(it) })
  }
}

thank you very much!!! @lovubuntu

for performance issue, maybe everyone can check samclarke post here:

https://www.samclarke.com/kotlin-hash-strings/

This is a nice little class. If you pass the algorithm ("SHA-256" in this example), it can be generalized to hash strings using different algorithms:

As an extension functions:

fun String.md5(): String {
    return hashString(this, "MD5")
}

fun String.sha256(): String {
    return hashString(this, "SHA-256")
}

private fun hashString(input: String, algorithm: String): String {
    return MessageDigest
        .getInstance(algorithm)
        .digest(input.toByteArray())
        .fold("", { str, it -> str + "%02x".format(it) })
}

class keyword has to be written in lowercase! @lovubuntu

Thank you that was really nice :)

Thank that help me

Thank you @reastland

This is going to have bad performance.
Better:

val hex = digest.fold(StringBuilder(), { sb, it -> sb.append("%02x".format(it)) }).toString()

Thanks to y'all

Your answers have saved my day

You can replace the fold with toHexString() (Mind you that this is, as of the time of writing this, marked as ExperimentalStdlibApi):

fun String.hashedWithSha256() =
    MessageDigest.getInstance("SHA-256")
        .digest(toByteArray())
        .toHexString()

val hashed = "12345".hashedWithSha256() // "5994471abb01112afcc18159f6cc74b4f511b99806da59b3caf5a9c173cacfc5"