How to generate checksum hash for a file in Kotlin

HashUtils.kt

import StringUtils.encodeHex
import java.io.File
import java.io.FileInputStream
import java.io.InputStream
import java.security.MessageDigest

object HashUtils {

    const val STREAM_BUFFER_LENGTH = 1024

    fun getCheckSumFromFile(digest: MessageDigest, filePath: String): String {
        val file = File(filePath)
        return getCheckSumFromFile(digest, file)
    }

    fun getCheckSumFromFile(digest: MessageDigest, file: File): String {
        val fis = FileInputStream(file)
        val byteArray = updateDigest(digest, fis).digest()
        fis.close()
        val hexCode = encodeHex(byteArray, true)
        return String(hexCode)
    }

    /**
     * Reads through an InputStream and updates the digest for the data
     *
     * @param digest The MessageDigest to use (e.g. MD5)
     * @param data Data to digest
     * @return the digest
     */
    private fun updateDigest(digest: MessageDigest, data: InputStream): MessageDigest {
        val buffer = ByteArray(STREAM_BUFFER_LENGTH)
        var read = data.read(buffer, 0, STREAM_BUFFER_LENGTH)
        while (read > -1) {
            digest.update(buffer, 0, read)
            read = data.read(buffer, 0, STREAM_BUFFER_LENGTH)
        }
        return digest
    }

}

Main.kt

import MessageDigestAlgorithm
import java.security.MessageDigest

fun main() {
    var file = File(":/storage/sdcard0/DCIM/Camera/1414240995236.jpg")
    val checkSumSha256 = HashUtils.getCheckSumFromFile(
        MessageDigest.getInstance(MessageDigestAlgorithm.SHA_256),
        file
    )
}

MessageDigestAlgorithm.kt

object MessageDigestAlgorithm {
    const val MD2 = "MD2"
    const val MD5 = "MD5"
    const val SHA_1 = "SHA-1"
    const val SHA_224 = "SHA-224"
    const val SHA_256 = "SHA-256"
    const val SHA_384 = "SHA-384"
    const val SHA_512 = "SHA-512"
    const val SHA_512_224 = "SHA-512/224"
    const val SHA_512_256 = "SHA-512/256"
    const val SHA3_224 = "SHA3-224"
    const val SHA3_256 = "SHA3-256"
    const val SHA3_384 = "SHA3-384"
    const val SHA3_512 = "SHA3-512"
}

StringUtils.kt

object StringUtils {

    /**
     * Used to build output as Hex
     */
    private val DIGITS_LOWER =
        charArrayOf('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f')

    /**
     * Used to build output as Hex
     */
    private val DIGITS_UPPER =
        charArrayOf('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F')

    /**
     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
     * The returned array will be double the length of the passed array, as it takes two characters to represent any
     * given byte.
     *
     * @param data a byte[] to convert to Hex characters
     * @param toLowerCase `true` converts to lowercase, `false` to uppercase
     * @return A char[] containing hexadecimal characters in the selected case
     */
    fun encodeHex(data: ByteArray, toLowerCase: Boolean): CharArray {
        return encodeHex(data, if (toLowerCase) DIGITS_LOWER else DIGITS_UPPER)
    }

    /**
     * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
     * The returned array will be double the length of the passed array, as it takes two characters to represent any
     * given byte.
     *
     * @param data a byte[] to convert to Hex characters
     * @param toDigits the output alphabet (must contain at least 16 chars)
     * @return A char[] containing the appropriate characters from the alphabet
     *         For best results, this should be either upper- or lower-case hex.
     */
    fun encodeHex(data: ByteArray, toDigits: CharArray): CharArray {
        val l = data.size
        val out = CharArray(l shl 1)
        // two characters form the hex value.
        var i = 0
        var j = 0
        while (i < l) {
            out[j++] = toDigits[0xF0 and data[i].toInt() ushr 4]
            out[j++] = toDigits[0x0F and data[i].toInt()]
            i++
        }
        return out
    }

}

Works like a charm, thank you very much 🚀

@LongClipeus I'd like to reuse this for a project. Under what license is this gist's content available?

@david-perez well, I imagine that if your project is open source there should be no issue. If your code is enclosed, @LongClipeus has the word 🤷🏼

@ArnyminerZ @david-perez I'm glad this little piece of code was helpful to both of you. Feel free to use it in your projects.

Most of the code in this sample I took from Apache Commons Codec and converted to Kotlin.

Thank you very much!
This is useful.