Protobuf.kt

/*

plugins {
	...
	kotlin("plugin.serialization") version "1.4.10"
}

dependencies {
	implementation("org.jetbrains.kotlinx:kotlinx-serialization-core:1.0.0")
	implementation("org.jetbrains.kotlinx:kotlinx-serialization-protobuf:1.0.0")
}

*/

fun main(args: Array<String>) {
    val content = Content(UUID.randomUUID().toString(), "my-body")
    val order = Order(UUID.randomUUID().toString(), "my title", content)

    val bytes = ProtoBuf.encodeToByteArray(order)
    println(bytes.toAsciiHexString())

    val obj = ProtoBuf.decodeFromByteArray<Order>(bytes)
    println(obj)
  
    // Prints:
    // {0A}$d06f6392-1b9d-43de-88ea-c822b8f402f9{12}{08}my title{1A}/{0A}$d81bf9cf-65ee-4741-882c-51ca4248e0e4{12}{07}my-body
    // Order(id=d06f6392-1b9d-43de-88ea-c822b8f402f9, title=my title, content=Content(id=d81bf9cf-65ee-4741-882c-51ca4248e0e4, body=my-body))
}

fun ByteArray.toAsciiHexString() = joinToString("") {
    if (it in 32..127) it.toChar().toString() else
        "{${it.toUByte().toString(16).padStart(2, '0').toUpperCase()}}"
}

@Serializable
data class Order(val id: String, val title: String, val content: Content)

@Serializable
data class Content(val id: String, val body: String)