refactor: Use hex coding from Kotlin's stdlib

Reduce custom code.

Signed-off-by: Sebastian Schuberth <sebastian@doubleopen.org>

buildSrc/src/main/kotlin/ort-kotlin-conventions.gradle.kts

@@ -174,6 +174,7 @@ tasks.withType<KotlinCompile>().configureEach {
     val hasSerializationPlugin = plugins.hasPlugin(libs.plugins.kotlinSerialization.get().pluginId)
 
     val optInRequirements = listOfNotNull(
+        "kotlin.ExperimentalStdlibApi",
         "kotlin.contracts.ExperimentalContracts",
         "kotlin.io.encoding.ExperimentalEncodingApi",
         "kotlin.io.path.ExperimentalPathApi",

model/src/main/kotlin/Hash.kt

@@ -26,9 +26,6 @@ import java.io.File
 
 import kotlin.io.encoding.Base64
 
-import org.ossreviewtoolkit.utils.common.decodeHex
-import org.ossreviewtoolkit.utils.common.encodeHex
-
 /**
  * A class that bundles a hash algorithm with its hash value.
  */
@@ -60,7 +57,7 @@ data class Hash(
                 // Support Subresource Integrity (SRI) hashes, see
                 // https://w3c.github.io/webappsec-subresource-integrity/
                 Hash(
-                    value = Base64.decode(splitValue.last()).encodeHex(),
+                    value = Base64.decode(splitValue.last()).toHexString(),
                     algorithm = HashAlgorithm.fromString(splitValue.first())
                 )
             } else {
@@ -83,7 +80,7 @@ data class Hash(
     /**
      * Return the hash in Support Subresource Integrity (SRI) format.
      */
-    fun toSri() = algorithm.name.lowercase() + "-" + Base64.encode(value.decodeHex())
+    fun toSri() = algorithm.name.lowercase() + "-" + Base64.encode(value.hexToByteArray())
 
     /**
      * Verify that the [file] matches this hash.

model/src/main/kotlin/HashAlgorithm.kt

@@ -27,7 +27,6 @@ import java.io.InputStream
 import java.security.MessageDigest
 
 import org.ossreviewtoolkit.utils.common.calculateHash
-import org.ossreviewtoolkit.utils.common.encodeHex
 
 /**
  * An enum of supported hash algorithms. Each algorithm has one or more [aliases] associated to it, where the first
@@ -159,5 +158,5 @@ enum class HashAlgorithm(vararg val aliases: String, val emptyValue: String, val
      * closing the stream.
      */
     private fun calculate(inputStream: InputStream, size: Long): String =
-        calculateHash(inputStream, getMessageDigest(size)).encodeHex()
+        calculateHash(inputStream, getMessageDigest(size)).toHexString()
 }

plugins/package-managers/bazel/src/main/kotlin/Bazel.kt

@@ -53,7 +53,6 @@ import org.ossreviewtoolkit.model.orEmpty
 import org.ossreviewtoolkit.utils.common.CommandLineTool
 import org.ossreviewtoolkit.utils.common.ProcessCapture
 import org.ossreviewtoolkit.utils.common.collectMessages
-import org.ossreviewtoolkit.utils.common.encodeHex
 import org.ossreviewtoolkit.utils.common.withoutPrefix
 import org.ossreviewtoolkit.utils.ort.createOrtTempFile
 import org.ossreviewtoolkit.utils.ort.runBlocking
@@ -310,7 +309,7 @@ private fun ModuleMetadata.toVcsInfo() =
 
 private fun ModuleSourceInfo.toRemoteArtifact(): RemoteArtifact {
     val (algo, b64digest) = integrity.split("-", limit = 2)
-    val digest = Base64.getDecoder().decode(b64digest).encodeHex()
+    val digest = Base64.getDecoder().decode(b64digest).toHexString()
 
     val hash = Hash(
         value = digest,

plugins/package-managers/spdx/src/test/kotlin/utils/SpdxResolvedDocumentTest.kt

@@ -49,7 +49,6 @@ import java.net.URI
 import org.ossreviewtoolkit.model.Issue
 import org.ossreviewtoolkit.model.Severity
 import org.ossreviewtoolkit.utils.common.calculateHash
-import org.ossreviewtoolkit.utils.common.encodeHex
 import org.ossreviewtoolkit.utils.spdx.SpdxModelMapper
 import org.ossreviewtoolkit.utils.spdx.model.SpdxChecksum
 import org.ossreviewtoolkit.utils.spdx.model.SpdxDocument
@@ -660,6 +659,6 @@ private fun File.toExternalReference(index: Int): SpdxExternalDocumentReference
     return SpdxExternalDocumentReference(
         externalDocumentId = referenceId(index),
         spdxDocument = name,
-        checksum = SpdxChecksum(SpdxChecksum.Algorithm.SHA1, hash.encodeHex())
+        checksum = SpdxChecksum(SpdxChecksum.Algorithm.SHA1, hash.toHexString())
     )
 }

utils/common/src/main/kotlin/Extensions.kt

@@ -38,11 +38,6 @@ import java.util.Locale
  */
 inline fun <T> T.alsoIfNull(block: (T) -> Unit): T = this ?: also(block)
 
-/**
- * Return a string of lowercase hexadecimal digits representing the bytes in the array.
- */
-fun ByteArray.encodeHex(): String = joinToString("") { String.format(Locale.ROOT, "%02x", it) }
-
 /**
  * Return a map that associates duplicates as identified by [keySelector] with belonging lists of collection entries.
  */
@@ -303,14 +298,6 @@ fun String.collapseWhitespace() = trim().replace(CONSECUTIVE_WHITESPACE_REGEX, "
 
 private val CONSECUTIVE_WHITESPACE_REGEX = Regex("\\s+")
 
-/**
- * Decode a hex-string and return the value as a [ByteArray].
- */
-fun String.decodeHex(): ByteArray {
-    require(length % 2 == 0) { "The string must have an even number of characters." }
-    return chunked(2).map { it.toInt(16).toByte() }.toByteArray()
-}
-
 /**
  * Return the string encoded for safe use as a file name or [emptyValue] encoded for safe use as a file name, if this
  * string is empty. Throws an exception if [emptyValue] is empty.

utils/common/src/test/kotlin/ExtensionsTest.kt

@@ -48,7 +48,7 @@ import java.util.Locale
 class ExtensionsTest : WordSpec({
     "ByteArray.toHexString()" should {
         "correctly convert a byte array to a string of hexadecimal digits" {
-            byteArrayOf(0xde.toByte(), 0xad.toByte(), 0xbe.toByte(), 0xef.toByte()).encodeHex() shouldBe "deadbeef"
+            byteArrayOf(0xde.toByte(), 0xad.toByte(), 0xbe.toByte(), 0xef.toByte()).toHexString() shouldBe "deadbeef"
         }
     }
 

utils/scripting/src/main/kotlin/OrtScriptCompilationConfiguration.kt

@@ -36,7 +36,6 @@ import kotlin.script.experimental.jvm.dependenciesFromCurrentContext
 import kotlin.script.experimental.jvm.jvm
 import kotlin.script.experimental.jvmhost.CompiledScriptJarsCache
 
-import org.ossreviewtoolkit.utils.common.encodeHex
 import org.ossreviewtoolkit.utils.common.safeMkdirs
 import org.ossreviewtoolkit.utils.ort.Environment
 import org.ossreviewtoolkit.utils.ort.ortDataDirectory
@@ -90,5 +89,5 @@ private fun generateUniqueName(script: SourceCode, configuration: ScriptCompilat
             digest.update(it.value.toString().toByteArray())
         }
 
-    return digest.digest().encodeHex()
+    return digest.digest().toHexString()
 }

utils/spdx/src/main/kotlin/Utils.kt

@@ -30,7 +30,6 @@ import org.ossreviewtoolkit.utils.common.Os
 import org.ossreviewtoolkit.utils.common.PATH_STRING_COMPARATOR
 import org.ossreviewtoolkit.utils.common.VCS_DIRECTORIES
 import org.ossreviewtoolkit.utils.common.calculateHash
-import org.ossreviewtoolkit.utils.common.encodeHex
 import org.ossreviewtoolkit.utils.common.isSymbolicLink
 import org.ossreviewtoolkit.utils.common.realFile
 import org.ossreviewtoolkit.utils.spdx.SpdxConstants.LICENSE_REF_PREFIX
@@ -62,7 +61,7 @@ val scanCodeLicenseTextDir by lazy {
 fun calculatePackageVerificationCode(sha1sums: Sequence<String>, excludes: Sequence<String> = emptySequence()): String {
     val sha1sum = sha1sums.sorted().fold(MessageDigest.getInstance("SHA-1")) { digest, sha1sum ->
         digest.apply { update(sha1sum.toByteArray()) }
-    }.digest().encodeHex()
+    }.digest().toHexString()
 
     return if (excludes.none()) {
         sha1sum
@@ -78,7 +77,7 @@ fun calculatePackageVerificationCode(sha1sums: Sequence<String>, excludes: Seque
  */
 @JvmName("calculatePackageVerificationCodeForFiles")
 fun calculatePackageVerificationCode(files: Sequence<File>, excludes: Sequence<String> = emptySequence()): String =
-    calculatePackageVerificationCode(files.map { calculateHash(it).encodeHex() }, excludes)
+    calculatePackageVerificationCode(files.map { calculateHash(it).toHexString() }, excludes)
 
 /**
  * Calculate the [SPDX package verification code][1] for all files in a [directory]. If [directory] points to a file